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Observations and Characterization of Subaqueous Soils and Seagrasses in a Recently Constructed Habitat in the Indian River Lagoon, Florida

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Title:
Observations and Characterization of Subaqueous Soils and Seagrasses in a Recently Constructed Habitat in the Indian River Lagoon, Florida
Creator:
FISCHLER, KELLY C.
Copyright Date:
2008

Subjects

Subjects / Keywords:
Eggshells ( jstor )
Lagoons ( jstor )
Nutrients ( jstor )
Soil horizons ( jstor )
Soil properties ( jstor )
Soil science ( jstor )
Soil texture ( jstor )
Soils ( jstor )
Topographical elevation ( jstor )
Velocity ( jstor )
Indian River Lagoon ( local )

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Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
Copyright Kelly C. Fischler. Permission granted to University of Florida to digitize and display this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Embargo Date:
3/1/2007
Resource Identifier:
658230293 ( OCLC )

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Full Text











OBSERVATIONS AND CHARACTERIZATION OF SUBAQUEOUS SOILS AND
SEAGRASSES IN A RECENTLY CONSTRUCTED HABITAT
IN THE INDIAN RIVER LAGOON, FLORIDA













By

KELLY C. FISCHLER


A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE

UNIVERSITY OF FLORIDA


2006
































Copyright 2006

By

Kelly C. Fischler



































To my family: Ira, Diane, Scott and Matt, and the many friends who have helped me
immeasurably.
















ACKNOWLEDGMENTS

This thesis is the result of the dedication of many family members, teachers, and

friends during the past 25 years. I say "25 years," because I was fortunate enough to

have been raised by true scholars who taught me the importance of education and hard

work. Through their enthusiasm for learning about the past and natural world, my

parents have given me the invaluable gift of curiosity. My mother, Diane (known for her

arsenal of red pens) taught me to write, and to be a strong, independent woman. She also

lent her editing skills to much of this thesis. My father, Ira, through his awe of the world

around him, taught me to love science and to appreciate the little things in life. As a UF

professor, he has been a valuable resource. A few sentences are not enough to thank

them for their love, support, finances, and meals brought to me in the lab. I also must

thank my brothers, Scott and Matt, for making sure that I grew up to be someone who

enjoyed playing in the dirt rather than with dolls. I have always looked up to them.

I would also like to thank my committee for their support. Many thanks go to my

advisor, Dr. Mary Collins, whose undergraduate class was the reason I pursued a degree

in soils. Her enthusiasm for soils and leadership among colleagues has been inspiring.

As the president of a national society, she is a role model for women in soil science.

Wade Hurt is one of a kind and is a wealth of knowledge that I feel privileged to access.

His generosity and concern for his students always show, whether through field help or

the snacks he provides during class. Many agree that his hydric soils test is demanding,

but I believe this challenge derives from his high expectations for students and a desire










for them to understand. I thank Dr. Tom Frazer for encouraging me to think critically

and showing me the importance of a scientific approach. When contemplating an

experimental design, or pondering what certain numbers really mean, I have often

thought, "What would Tom ask?" Although I don't have a beard to scratch while I wax

intellectual, I hope one day to think like Tom. Lastly, I offer a lifetime of thanks to

Dr. Rex Ellis. For the past 3 years he continually offered me chances to grow and learn.

Even the small lessons, such as driving his boat, were appreciated. Rex is known for his

selflessness when it comes to helping others and he repeatedly sacrificed time from his

own work and family to help me in the Hield and onfce. He often claims to "over-think

things," but it is really a sign of a true scientist. This proj ect was a collaboration, and

would not have been possible without him. I thank him for being my mentor and my

friend.

Additional thanks go to Tom Saunders and Chip Chilton for their Hield help, bad

jokes, and always giving me an excuse to take a break. Genaro Keehn was an immense

asset and through his lab and field work, helped me get this proj ect done. Caitlin Hicks

and Natalie Balcer were great colleagues and always willing to listen. Todd Osborne was

especially helpful in the clutch when I needed data. Stephanie Keller was also helpful

during lab analyses. Numerous others have been around to see me through, and I could

not have made it this far without their love and support. Travis, Betsy, Sarah, Melissa,

Paul, Emily, David, Doug, and Jim are my daily inspirations and I thank them for

everything.





















TABLE OF CONTENTS


page

ACKNOWLEDGMENT S .............. .................... iv


LI ST OF T ABLE S ................. ................. viii............


AB STRAC T ................ .............. xi


CHAPTER


1 INTRODUCTION ................. ...............1.......... ......


Obj ectives ................. .. ........ ...............2.......
Sea grass Growth Dynamics ................. ...............3............ ....
Light Availability .............. ...............3.....
Hy drodynami c s ................ ...............4................
Nutrient Cycling ................. ...............5.......... ......
Sub aqueous Soil s................ ...............6.
Seagrass Transplant Experiment. .....___...................___ ............1
Study Site Description ............_...... ._ ...............10...
Spoil Islands .............. ...............12...
The SL 15 Design Concept. ............ .....___ ...............12.


2 METHODS ............ _...... ._ ...............15....


Obj ective 1: Quantification of Environmental Parameters ................. ................ ...15
L ight .............. ...............15....
Chlorophyll ........._..._.._ ...._._. ................ 15...
Currents .............. ...............16....
N utrients ................. ...............16.......... .....
S oil s/1and scape ................. ................. 17..............
Benthic Observations................ .............1

Obj ective 2: Transplant Experiment ................. ....._.._......_. ...........1
Obj ective 3: Habitat Suitability Model ........._._.. ..... ..._. .....__. ..........2

3 RE SULT S .............. ...............25....


Objective 1: Environmental Conditions .............. ...............25....
Light Availability .............. ...............25....
Currents .............. ...............26....












Nutrients ....................... ...............27

Digital Elevation Model .............. ...............27....
Subaqueous Soils............... ...............28.
Benthic Observations................ .............3

Obj ective 2: Transplant Experiment ...._.._.._ ......._._. ...._.._ ..........3
Obj ective 3: Habitat Suitability Model ................. ...............35......_... ..

4 DI SCUS SSION ....._.._................. ........_.._.........5


Soil/Land scape Analy sis............... ...............54

Bathym etry .............. ...............55....
Flow Regime .............. ...............56....
Parent M material .............. ...............56....
Clim ate .............. ...............57....

Organi sm s........._ ....... __ ...............58....
Time............... ...............58.

Catastrophic Events ........._. ....... .__ ...............59....
Water Column Attributes .............. ...............60....

Subaqueous Soil Survey .............. ...............60....
Light Availability............... ..............6
Hy drodynami c s........._.__....... .__. ...............63...
N utrients .............. ...............65...

Transplant Experiment ................. ...............66.................
Seagrass Recruitment................ .............6
Habitat Suitability Model .............. ...............68....


5 SUMMARY AND CONCLUSIONS ................ ...............72................


APPENDIX


A SUBAQUEOUS SOIL DESCRIPTIONS .............. ...............75....


B SUBAQUEOU S SOIL DATA .............. ...............92....


C HYDRODYNAMIC DATA ................. ...............97........... ....


D LIGHT AND NUTRIENT DATA ................. ...............102........... ...


E T RAN SPLANT D AT A ................. ................. 105........ ....


LIST OF REFERENCES ................. ...............108................


BIOGRAPHICAL SKETCH ................. ...............116......... ......













LIST OF TABLES


Table pg

3-1 Chlorophyll a values from each transplant quadrat .............. .....................3

3-2 Average subaqueous soil properties from the bay and natural habitat at SL 15 ......43

3-3 Average soil properties from 0-10 cm in each landscape unit .............. .... ........._...45

3-4 Total number of shoot counts per transplant quadrat over time ............... .... ...........51

B-1 Soil descriptions from the bay............... ...............82..

B-2 Soil descriptions from the natural habitat .............. ...............85....

B-1 Subaqueous soil data from the natural (outside) habitat.. ................ ................ ..92

B-2 Subaqueous soil data from the bay ................. ...............93........... ..

C-1 Current direction (Dir.) and velocity (V) .............. ...............97....

D-1 Light attenuation coefficients (Kd) for the natural and bay habitats ......................103

D-2 Total dissolved Kj eldalh nitrogen (TDKN) and total dissolved phosphorus
(TDP) from 0-5 cm porewater samples ................. ...............104..............


















LIST OF FIGURES


Figure pg

1-1 Study site location in Ft. Pierce, Florida ....._ ................ ............... ....1

1-2 Transformation of SL 15 ................. ...............14........ ...

2-1 Light meter apparatus ................. ...............21........ .....

2-2 Soil porextractor ................. ...............22........... ....

2-3 Bathymetric sampling locations ................ ...............23................

2-4 Soil sampling locations in the bay and natural habitat ................. ............. .......24

2-5 Transplant quadrats location and construction ................. .....___..................24

3-1 Average Kd ValUeS in the natural and constructed bay habitat ................. ...............36

3-2 Average water velocities on both outgoing and incoming tides .............. ................37

3-3 Current flow velocity and direction in the bay............... ...............38..

3-4 Classified maps of current velocities in the bay............... ...............39..

3-5 Digital elevation model of the bay ................. ................ ......... ........ .40

3-6 Representative subaqueous soils taken from the natural outside habitat and
inside the constructed bay habitat .............. ...............41....

3-7 Soils from representative transect 6 from the bay............... ...............42..

3-8 Settling characteristics of soils from the bay and the outside habitat .....................44

3-9 Characteristics of the Ab horizon from the bay .........._..._ .......... ...............45

3-10 Digital elevation model showing delineations of landscape units ..........................46

3-11 Classified landscape units .............. ...............47....

3-12 Percent cover map of Gracilaria sp. in March, 2006............... ..................4











3-13 Seagrass distribution in the bay as of September, 2006............_.__ ........._._ .....49

3-14 Seagrass abundance in the bay per m2 ............. ...............50.....

3-15 Halodule johnsonii recruits in the bay .............. ...............51....

3-16 Epiphytes and macroalgae at SL 15 ........._..._.. ...._.__ ......._ ........._.....52

3-17 Habitat suitability model showing the areas in the bay which had current and
soil properties similar to those in the natural habitat outside of SL 15 ....................53

4-1 Relationship of bathymetry to OM content ................. ...............70........... ..

4-2 Relationship between elevation and F horizon thickness............... ................7

4-3 Relationship between silt % and current velocity .............. ....... .............7

A-1 Soil sampling locations in the bay and natural habitat ......__. ........... ........ .......75

A-1 Soils taken from transect 1 on the east side of the bay ........._.__.... ....._._. .......86

A-2 Transect 2. ............. ...............87.....

A-3 Transect 3 .............. ...............88....

A-4 Transect 4. ............. ...............89.....

A-5 Transect 5 .............. ...............90....

A-6 Transect 6. ............. ...............91.....


D-1 Sampling locations for light attenuation (Kd) .............. ...............102

D-2 Sampling locations for porewater nutrients in the bay and constructed habitats..104

E-1 Halodule wrightii shoot counts in each transplant quadrat ................. ................1 05
















Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science

FACTORS AFFECTING SEAGRASS GROWTH IN A CONSTRUCTED HABITAT
IN INDIAN RIVER LAGOON, FLORIDA

By

Kelly C. Fischler

December 2006

Chair: Mary E. Collins
Major Department: Soil and Water Science

Anthropogenic impacts to seagrasses in the Indian River Lagoon (IRL), Florida

have led to a new method for mitigation in which spoil island SL 15 (St. Lucie County)

was scraped down to create a 1.7 ha submerged bay habitat. To assess the suitability of

this created habitat for seagrass growth, light availability, nutrient content, hydrodynamic

and subaqueous soil conditions in the bay were compared to conditions in the

surrounding natural seagrass beds. There were no significant differences in average light

attenuation (Kd) COefficients in the bay and natural habitat (0.54 m-l and 0.55 m l,

respectively). All underwater irradiance values were above the minimum requirement for

seagrass growth in the IRL. Porewater nutrients at SL 15 were determined by analyzing

total dissolved Kjeldahl nitrogen (TDKN) and total dissolved phosphorus (TDP). Results

showed no significant differences in TDP values in the two habitats, but TDKN values

were slightly higher in the bay (2.53 mg L^1) than in the natural system (1.27 mg L^)~.

Water velocities in the bay were mapped on incoming and outgoing tides to better









understand hydrodynamic conditions and circulation patterns. Although average

velocities in the bay and natural habitat on both tides were not significantly different,

more spatial variability occurred in the bay.

Soil and landscape relationships in the bay were examined by creating a fine-scale

soil survey and digital elevation model. The recently exposed bottom within the bay

consisted of four soils: a coarse carbonate spoil material (Cgl), a fine-textured mangrove

clay (Cg2), an accreted flocculent layer (F horizon), and a buried seagrass A (Ab)

horizon. Surface soil properties correlated with elevation. Subaqueous soils in the natural

habitat were characterized by homogenous dark colors and were dominantly sandy loams

in texture. More variability appeared with regard to texture and organic matter content in

the bay than in the natural habitat.

A transplant experiment was also conducted to assess the viability of Halodule

vi igthlii in the bay. Six plots were planted in May 2006 and monitored monthly for shoot

counts. One plot in the bay maintained transplant viability, suggesting the suitability of

the bay for colonization. This hypothesis was supported by the discovery of four species

of seagrasses growing in the bay. Seagrass recruitment in the bay appeared to follow an

east-west gradient, with higher concentrations of shoots in the west. Although the

environmental conditions in the bay appeared more heterogeneous than in the natural

habitat, successful seagrass recruitment suggested that the design of SL 15 was sufficient

for colonization.















CHAPTER 1
INTTRODUCTION

Seagrasses are marine angiosperms that account for as much as 12% of net oceanic

carbon production (Duarte and Chiscano, 1999; Hemminga and Duarte, 2000). In

addition, seagrass beds perform a variety of ecological functions. They stabilize soils,

promote the deposition of particles that leads to increased water clarity, and also serve as

important refuge and foraging habitats for a large number of fishes and invertebrates

(Dawes, 1981; Larkum et al., 1989; Stevenson et al., 1993; Virnstein and Morris, 1996;

Nagelkerken et al., 2000). Seven species of seagrasses occur in the Indian River Lagoon

(IRL): Halodule wrightii Ascherson, Syringodium fihfornze Kutz, Thala~ssia testudinunt

Banks ex Koinig, Ruppia nzaritinta L., Halophila dicipiens Ostenfeld, Halophila

englenzanii Aschers, and the threatened species, Halophila johnsonii Eisemen (Dawes et

al., 1995). Collectively, these grasses form the most crucial habitat in the lagoon's

ecology (Steward et al., 1994).

In recent decades, however, environmental and anthropogenic stresses in the IRL

have led to an 11% decrease in total seagrass acreage and a 50% decrease in their

maximum depth of occurrence (Fletcher and Fletcher, 1995). Research on the IRL

provided information on environmental conditions needed for seagrass growth such as

light and nutrients, as well as methods for mapping the distribution and health of species

(Dawes et al., 1995; Fletcher and Fletcher, 1995; Virnstein, 1995; Gallegos and

Kenworthy, 1996; Morris et al., 2000; Virnstein and Morris, 2000). No studies,

however, have examined seagrass growth in the IRL in the context of a restored habitat.









In the spring of 2005, a mitigation proj ect in Ft. Pierce, Florida, provided an

opportunity to observe seagrasses in a constructed environment. The transformation of

spoil island SL 15 (St. Lucie County) into a potential habitat for seagrasses offered a

unique chance to examine how different ecological parameters might interact and affect

future seagrass colonization. Prior research established the importance of light

availability, hydrodynamics, and nutrient cycling to seagrass health (Fonseca and

Kenworthy, 1987; Kemp et al., 1988; Duarte, 1991; Olesen and Sand-Jensen, 1993;

Koch, 2001). Subaqueous soil has also been cited as affecting seagrass geochemistry and

landscape attributes (Carlson et al., 1994; Demas et al., 1996; Demas, 1998; Demas and

Rabenhorst, 1999; Borum et al., 2005; Holmer et al., 2005; Bradley and Stolt, 2006; Ellis,

2006). Observing and characterizing these different ecological parameters was therefore

important for understanding the potential ability for seagrass colonization in SL 15.

Obj ectives

Specific requirements for light, hydrodynamics, nutrients, and subaqueous soil

characteristics may vary significantly by location and species. In the IRL, light

requirements for seagrasses have been published (Gallegos and Kenworthy, 1996), but

threshold values for current velocities or soil organic matter, for example, have not been

determined. Thus, one approach for answering the question "is the constructed habitat of

SL 15 sufficient for seagrass growth?" is to compare its subtidal environment within

SL 15 to that of the proximate seagrass beds. Accordingly, three objectives were formed:

* Objective 1: Quantify and describe the environmental factors which might act
upon seagrasses in SL 15.

* Objective 2: Conduct a seagrass transplant experiment in the natural and
constructed habitat.

* Objective 3: Synthesize the data into a habitat suitability model.










Objective 1 addressed the specific parameters previously determined to affect

seagrass growth, including light attenuation, current velocity, nutrient content, and

subaqueous soil conditions. The purpose of Obj ective 2 was to test whether or not

seagrass transplants would survive in SL 15. Finally, the environmental data was

combined to estimate the area within the constructed habitat in SL 15 which would be

supportive of seagrass colonization.

Seagrass Growth Dynamics

Since the publication of Seagra~sses of the World by C. Kees den Hartog in 1 970,

numerous experimental and observational studies on the biology and ecology of

seagrasses have increased our understanding of submerged aquatic vegetation (Larkum et

al., 2006). As a result, certain environmental parameters have become established as

vital factors affecting seagrass.

Light Availability

The vast maj ority of research on seagrasses has involved the direct or indirect

effects of light on their biophysical ecology. As with terrestrial angiosperms, seagrasses

require a minimum amount of photosynthetically active radiation (PAR; 350 or 400 to

700 nm) to produce and survive (Hemminga and Duarte, 2000; Zimmerman, 2006).

Most species require 10 to 37% of in-water surface irradiance (Duarte, 1991; Olesen and

Sand-Jensen 1993; Kenworthy and Fonseca, 1996). In the IRL, Halodule wrightii and

Syringodium fihforme require approximately 24 to 37% of surface irradiance to maintain

net productivity (Gallegos and Kenworthy, 1996; Kenworthy and Fonseca, 1996). The

intensity and duration of light vary with season and location, as do the metabolic

requirements for each species (Hemminga and Duarte, 2000).










Light reduction experiments have shown various negative responses in seagrass

growth and morphology. Decreased light can impact shoot density, blade length,

biomass, and chlorophyll content (Neverauskus, 1988; West, 1990; Williams and

Dennison, 1990). Seagrass physiology is affected by light reduction because oxygen

produced from photosynthesis in the leaves diffuses to the rhizosphere and allows

seagrasses to grow in anaerobic sediments. If light availability and photosynthesis rates

are high, then seagrasses can maintain a larger supply of oxygen to the roots and prevent

phytotoxic sulfide intrusion. Several studies correlated shorter and less intense light

periods with lower photosynthesis rates and increased sulfide toxicity (Goodman et al.,

1995; Holmer and Bondgaard, 2001; Pederson et al., 2004; Holmer et al., 2005).

Manipulating light levels in an experimental setting is informative since one of the

leading causes of seagrass loss is increased light attenuation due to water quality decline

(Kemp et al., 1988; Short and Wyllie-Echeverria, 1996; Tomasko et al., 1996). Light is

attenuated rapidly in even clear water and is further attenuated when dissolved organic

particles are present (Hemminga and Duarte, 2000). A common method for reporting

how much light is absorbed with depth is Kd, or the downwelling attenuation coefficient.

Based on the literature, Kd and chlorophyll a were chosen as variables to describe the

light environment at SL 15.

Hydrodynamics

Current flows in seagrass beds have been shown to affect leaf nutrient uptake,

organic matter transport, pollination, sediment characteristics, light conditions, biomass,

and production (Schumacher and Whitford, 1965; Madsen and Sondergaard, 1983;

Fonseca and Kenworthy, 1987; Koch et al., 2006). Elevated current speeds coincide with

morphological adaptations, such as greater root mass (Short et al., 1985). Faster









velocities also contribute to increased nutrient uptake through the thinning of the diffuse

boundary layer that surrounds leaf blades (Koch, 1994; Massel, 1999; Cornelisen and

Thomas, 2002). Although increased flows can limit the growth of light-reducing

epiphytes on seagrass blades, epiphytes might also serve to "roughen" the boundary layer

and become beneficial (Boston et al., 1989).

Seagrass canopies attenuate current velocity (Fonseca et al., 1982; Fonseca and

Fisher, 1986; Gambi et al., 1990) and reduce physical stress on the plants, but decreased

flows can increase sediment anoxia and allow for more organic matter accretion (Robblee

et al., 1991). Low-flow conditions, therefore, can result in increased porewater sulfide

(Barko et al., 1991; Koch, 1999). Koch (2001) summarized minimum and maximum

threshold values for different seagrass species, only one of which was a subtropical

species. Thala~ssia testudinum was reported to require a minimum velocity of 5 cm/s for

growth and occurrence (Koch, 1994). The time of exposure to different water velocities

was not reported and the requirements for H. wrightii and S. fihiforme are not yet known.

Nutrient Cycling

Although seagrasses are highly productive (up to 800 g carbon m2/yr; Hauxwell et

al., 2001), they typically grow in nutrient-poor waters (Short, 1987; Hemminga and

Duarte, 2000). Because of phosphate's tendency to bind with carbonates (Kitano et al.,

1978), it is a potentially limiting nutrient in tropical seagrass beds (Short, 1987;

Hemminga and Duarte, 2000). Nitrogen is also commonly limited in marine systems

(Short, 1987; Hauxwell et al., 2001; Fourqurean and Zieman, 2002). Short et al. (1993)

noted that in the IRL, nitrogen is the limiting nutrient for S. fihiforme growth. The ability

of seagrasses to grow in oligotrophic waters suggests that they obtain most of their

nutrients (via roots) from the soil, which typically has higher concentrations of









ammonium, phosphate, and nitrate than the overlaying water column (Short, 1987;

Hemminga, 1997; Hemminga and Duarte, 2000; Romero et al., 2006).

While experiments have shown that nutrient enrichment increases leaf and root

biomass (Udy and Dennison, 1997), excess nutrient loading in coastal systems has caused

as much as 50% of worldwide seagrass loss (Short and Wyllie-Echeverria, 1996).

Nutrient-limited algae bloom in response to elevated nutrients, causing eutrophication

and increases in light-attenuating phytoplankton, epiphytes and macroalgae (Cambridge

and McComb, 1984; Silberstein et al., 1986; Kemp et al., 1988; Tomasko et al., 1996;

Ralph et al., 2006). Increased organic matter to the system also adds substrate for

microbial decomposition and thus increases the danger for sulfide toxicity (Terrados et

al., 1999). Between 1940 and 1991, nitrogen inputs from waste water doubled in Tampa

Bay, Florida, resulting in as much as 72% loss of seagrasses by 1982 (Haddad, 1989;

Lewis et al., 1991; Zarbok et al., 1994). Chlorophyll concentrations were positively

correlated with nitrogen levels, thus showing the relationship between nutrient additions

and phytoplankton production (Johansson, 1991). Although the seagrass loss in Tampa

Bay was more significant than that observed in the IRL during the past few decades,

similar increases in nutrient loading have occurred. As a consequence, nutrients are a

primary concern of water resource managers working in the IRL.

Subaqueous Soils

Although many studies have investigated relationships between seagrasses and

their environment, few have focused on the ecological function of the substrates they

occupy. Of the studies that specifically addressed estuarine sediments, most involved

anecdotal observations and were based mainly upon geologic or geochemical principles

(Demas et al., 2001). In the mid-1990s, however, efforts in Maryland demonstrated that









certain sediments could be included in the realm of soil science (Demas et al., 1996;

Demas, 1998; Demas and Rabenhorst, 1999). Researchers observed that sediments

under shallow waters (less than 2.5 m) can experience soil-forming factors, such as those

described by Jenny (1941). These factors include additions from biogenic CaCO3 and

marine humus (Valiela, 1984), bioturbation by infaunal organisms, and chemical

transformations through the oxidation and reduction of S and Fe (Demas, 1998; Bradley

and Stolt, 2003). These investigations spearheaded the inclusion of subaqueouss soils"

within the defined concept of soil by the USDA-National Resource Conservations

Service in 1999 (Demas, 1998; Demas and Rabenhorst, 1999; Bradley and Stolt, 2003).

This broadened view of aquatic bottoms was significant in that it enabled the inclusion of

submerged aquatic vegetation, such as seagrasses, in a pedological paradigm. Demas

(1999) demonstrated that similar to terrestrial soils, subaqueous soils form as a function

of their landscape. Their vegetation cover, elevation position, and even parent material

can create distinct horizons which elucidate previous environments and processes. By

studying these horizons in a pedological context, a suite of characterization analyses can

be performed and used to classify the soil under taxonomic mapping units (Bradley and

Stolt, 2003).

Research in the coastal marsh estuaries of Rhode Island and Maryland, along with

the near-shore grass flats on the west coast of Florida, has demonstrated significant

relationships between seagrasses and soil characteristics, such as color, percent organic

matter, salinity, and texture (Demas, 1999; Bradley and Stolt, 2006; Ellis, 2006).

Subaqueous soils within established beds are typically finer in texture than those in

unvegetated soils (Scoffin 1970; Koch, 2001; Ellis, 2006). Coarse sandy soils might










improve Ol diffusion, but they inhibit rhizome elongation and have less fertility, while

Eine-textured soils might contribute to elevated sulfide levels (Thayer et al., 1994;

Fonseca et al., 1998; Koch, 2001; Bradley and Stolt, 2006). The ability of seagrasses to

attenuate currents and trap particulate organic matter contributes to dark soil colors and

Eine textures, yet most vegetated subaqueous soils have less than 5% organic matter

(Koch, 2001). Higher percentages of organic matter occur, however, but it is unknown if

maximum thresholds exist.

Mesocosm experiments have provided some indication as to whether seagrasses

prefer one type of soil to another. Kenworthy and Fonseca (1977) transplanted Z. marina

from sand, sand-silt, and silt into each of the three soils. Results showed the highest

productivity occurred with silt-originating plants and those which were planted into a silt

soil. The specific percentages of sand and silt in each soil were not identified, however,

leaving the term "sand-silt" as a vague description. Another mesocosm experiment

examined Ruppia maritima growing on different sizes of glass beads to represent sand

and determined that Eine and medium sand-size particles resulted in maximum growth

(Koch, 2001). The use of glass beads avoided the effects of nutrient uptake. It would

therefore be of interest to understand the interactions that influence nutrient availability in

silty versus sandy soils.

In a mitigation proj ect similar to SL 15, subaqueous soils might have influenced

seagrass survival. Three spoil islands were scraped down in Laguna Madre, Texas, each

with different soil characteristics (Montagne, 1993). H. wrightii survived in two of the

island areas, one with 90% sand, 2% silt, and 3% clay, and the other with 88% sand

(Montagne, 1993). All plants died at the third site, however, which had 63% sand and









31% clay (Montagne, 1993). This latter observation suggested that a more detailed

characterization of the subaqueous soils at SL 15 was important.

In traditional soil science, the most common method for mapping the distribution of

soils is through the creation of a soil survey. A soil survey

describes the characteristics of the soils in a given area, classifies the soils
according to a standard system of classification, plots the boundaries of the soils on
a map, and makes predictions about the behavior of soils. The different uses of the
soils and how the response of management affects them are considered (Soil
Survey Staff, 1993)

When creating these maps, observations of landscape (slope, drainage) and

vegetation (crops, native plants) are made in order to generate a conceptual model of soil

formation in the survey area. These attributes, along with physical properties (texture,

horizons) and chemical properties (mineralogy, base saturation), allow pedologists to

define boundaries between soils and to group them into taxonomic units. Previous

attempts at subaqueous soil mapping involved the classification of soils into "landscape

units," which were based upon bathymetry, land-surface shape, location, water depth, and

depositional environment (Demas and Rabenhorst, 1999; Bradley and Stolt, 2003).

Although terrestrial soil science uses "soil map units" as the term for areas with a

dominant kind of soil, these "landscape units" also had shared properties which were

labeled with traditional taxonomic classes, as defined by Soil Taxonomy (Soil Survey

Staff, 1975). Ellis (2006) created a subaqueous soil survey on the west coast of Florida,

which also delineated a seagrass-supporting habitat into taxonomic units based upon

vegetation, landscape, and geographic location with respect to land.

Because the goal of this study was to assess the suitability of SL 15 for seagrass

growth, a subaqueous soil survey was created as a method for describing its physical

environment using established terminology and guidelines. This soil survey also










provided a means of comparison between the natural and constructed habitats. By

delineating the inside of SL 15 into soil (or landscape) units which had similar physical

and chemical properties, the similarities, or differences from soils in the natural habitat

would be more clearly defined.

Seagrass Transplant Experiment

Seagrass restoration and mitigation are currently multimillion dollar industries in

Florida and could continue growing with increased coastal development (R. Lewis, pers.

comm.). Since the 1970s, different methods have resulted in numerous successes and

large-scale failures (Stein, 1984). By 1998, an official set of guidelines and decision

keys were established for restoration in the United States (Fonseca et al., 1998).

Although planting remains somewhat haphazard in success rates, technical improvements

continue to be made, such as the addition of cages for grazing prevention (Hauxwell et

al., 2004).

Success criteria for SL 15 are defined as 10% seagrass cover within the first 5 years

(R. Lewis, pers. comm.) is not achieved by natural recruitment in the first Hyve years, then

H. wrightii will be planted. For this study, a small-scale transplantation experiment

sought to test the viability of such plantings and supplement the Eindings of Obj ective 1.

With three plots inside SL 15 and three plots outside in the surrounding seagrass beds0,

transplant results could also possibly indicate how differences in soil type might

influence future growth.

Study Site Description

The IRL is a shallow, barrier island lagoon which stretches 250 km along the

Atlantic coast of Florida (Figure 1-1). It has an average depth of 1.7 m and an average

width of 3 km (Smith, 2001). The IRL formed in the last 6,000 years when coastal retreat









and sea level rise stabilized (Davis et al., 1992). Although the confining Hawthorne

Formation is thinnest or absent along the east coast of Florida, the four surficial aquifers

that border the IRL contribute only 1% to 5% of interstitial water, suggesting that most of

the IRL consists of recycled seawater (Swarzenski et al., 2000). Other controls on

salinity include precipitation, wind, tidal forcing, evaporation, and surface runoff

(Swarenski et al., 2000). Microtidal exchange occurs through four inlets in the southern

part of the lagoon: Sebastian, Ft. Pierce, St. Lucie, and Jupiter. The study site location

for this proj ect is located within 3 km of the Ft. Pierce Inlet, which transports more than

50% of the intertidal volume of the lagoon (Smith, 2001).

The IRL is considered to be one of the most diverse estuaries in the United States

(Gilmore et al., 1983). Species richness in the IRL has been attributed to its location

which straddles both tropical and subtropical regimes (Dawes et al., 1995). During the

past 50 years, however, development has increased urban and agricultural runoff and

subsequently decreased water quality (Steward et al., 1994; Fletcher and Fletcher, 1995;

National Estuary Program, 1996; Sigua et al., 1999). Such changes could possibly shift

the IRL from a macrophyte-dominant to an algal-dominant system (Steward et al., 1994).

After seagrass loss increased to 70% in some areas, the St. Johns River Water

Management District implemented a network of water quality monitoring sites and

permanent seagrass transects (Morris et al., 2000; Virnstein and Morris, 2000). The

percent coverage along most of these transects actually increased from 1994 to 1998, but

was highly variable (Morris et al., 2000). The current estimate of seagrass coverage for

the IRL is 30,000 ha (Morris and Virnstein, 2004). The database for water quality and









seagrass coverage in the IRL is extensive and growing, yet with mitigation projects such

as that at SL 15, more localized monitoring is needed.

Spoil Islands

Spoil islands in the Indian River Lagoon were created in the 1950s when the Army

Corps of Engineers dredged the Intracoastal Waterway for navigation. Spoil material

from the bottom of the channel was deposited in piles, thus creating 137 islands

throughout the lagoon. Of these 137 islands, 124 are owned by the state and managed by

the Florida Department of Environmental Protection (FDEP). Although the spoil islands

contain a diversity of organisms and frequently act as a native bird habitat, many are

inhabited by exotic vegetation, including Schinus terebinthefolius (Brazilian pepper) and

Casuarina~s equisetifolia (Australian pine). The transformation of a spoil island into an

intertidal and subtidal flat, therefore, had the dual benefit of removing exotics and

creating a potential habitat for native vegetation (e.g. seagrasses and mangroves).

The SL 15 Design Concept

After seagrasses were damaged during bridge construction in Jensen Beach,

Florida, the Florida Department of Transportation was required to mitigate for lost

vegetation. Spoil island SL 15 (270 28' 40" North, 80o 19' 23" West; Figure 1-1) was

chosen because of its sufficient size (4. 1 ha), lack of recreational use, and proximity to a

spoil basin (R. Lewis, pers. comm.). In March 2005, the excavation of SL 15 began with

the removal of all vegetation except the outer 1.24 ha of mangroves (Rhizophora mangle,

Avicennia germinans, and Conocarpus erectus). A trellis was built on the west side of

the island on which a conveyor belt transported material off the island to a barge. Seven

flushing channels were cut through the mangroves on the southern half of the island to

allow for tidal exchange and colonization of seagrasses from the surrounding flats (Figure








1-2). The completed inner submerged bay measures 1.37 ha and was excavated to a

mean depth of 1.5m NGVD. Coccoloba uvifera L. (sea grape) and C. erectus were

planted on the 0.54 ha of upland maritime hammock. The remaining interior of the island

(2.16 ha) was scraped to 1.0 m NGVD and planted with R. mangle propagules and

Spartina alterniflora along the bank ed ges.


Yi


1 '"

bi,.


Figure 1-1. Study site location in Ft. Pierce, Florida. A) Location of Ft. Pierce in the
Indian River Lagoon. B) Spoil island SL 15 (270 28' 40" North, 80o 19' 23 "
West), located north of the A1A bridge in Ft. Pierce.


Fort Pierce,
Florida













































Figure 1-2. Transformation of SL 15. Aerial photos taken in (A) June 2004, (B) May, 2005, (C) November, 2005, and (D) December,
2005. The yellow polygons show each constructed zone, including the seagrass, mangrove and upland habitats.















CHAPTER 2
IVETHOD S

Objective 1: Quantification of Environmental Parameters

Light

Light attenuation coefficients (Kd) were quantified by taking in situ measurements

of surface and underwater Photosynthetic Photon Flux Density (PPFD, Cpmol sl m- ). A

cosine-corrected LI-COR 192SA underwater light sensor (22n) on a mounting frame was

attached to a polyvinyl chloride (PVC) pipe (Figure 2-1). Measurements were recorded

at bottom depth and at a mid-depth point in the water column, usually at 10 cm or 20 cm

below the surface. Surface PPFD was taken simultaneously with a LI-COR 190 light

sensor. Four paired at-depth and surface readings were recorded by a LI-COR 1400

datalogger and then averaged at each site. Seven sites were sampled within the bay and

nine outside the bay (Appendix D). Kd WaS calculated using Beer' s Law (Equation 2-1),

where

Iz =Ioe"(2-1)

z=depth (m), and I= irradiance values (Cpmol sl m l) at z depth (Iz) and at the surface (lo).

Solving for Kd,

Kd= n(z o)/z (2-2)

Chlorophyll

Chlorophyll a concentration served as an estimate of phytoplankton biomass and

contributed to an understanding of the light environment at SL 15. Six surface water

samples and replicates were collected from each transplant quad and filtered in the field.









A Nalgene" vacuum hand pump was used to filter 500 ml of water through a Whatman"

GF/F glass fiber filter (Strickland and Parsons, 1968; Frazer et al., 2001;). Pigment

extraction used 90% heated ethanol, and corrections for pheophytin were made by

acidifying the sample with 0.2 N HCI (Sartory and Grobbelaar, 1984). Samples were

analyzed at the Department of Fisheries and Aquatic Sciences, University of Florida.

Currents

Current velocities at SL 15 were measured throughout the bay at times of

incoming (n=154) and outgoing (n=168) tidal flow to better understand circulation

patterns and flow magnitudes in the seagrass zone. To capture events within a similar

tide range, observations were made within a one hour time period. Three teams were

equipped with a Trimble" or Garmin" Global Positioning System (GPS). Bright Dyes

Fluorescent water tracing dye was used to observe current direction and speed. The

direction was quantified using a meterstick and compass while speed was calculated

using a stopwatch.

Nutrients

For the purpose of this study, porewater was analyzed in order to characterize the

nutrient environment at SL 15. Fourteen porewater samples from the inside (n=8) and

outside (n=6) of SL 15 were collected on August 23, 2006, using a porextractor (Figure

2-2, Nayar et al., 2006). The design of the apparatus enabled an integrated extraction

from 1 to 5 cm below the soil surface. Samples were drawn through a 0.45 Cpm filter,

acidified with 36 N2SO4, and kept refrigerated until analyzed. Total dissolved

phosphorus (TDP) and total Kjeldahl nitrogen (TKN) were KSO4 digested and analyzed

using an autoclave colorimetric autoanalyzer at the Wetlands Biogeochemistry Lab in the

Soil and Water Science Department at the University of Florida (EPA 3 51.2).









Soils/landscape

In terrestrial soil science, a priori knowledge of landforms in the survey area is

obtained from aerial photos and field observations. In a subaqueous environment,

however, these landforms are hidden underwater. At SL 15, bathymetric data were

collected and converted into a digital elevation model (DEM) in order to visualize the

microtopography that resulted from the construction process.

Bathymetry for the inside of SL 15 were collected, using a meter stick to measure

water depth and a Trimble Pathfinder" Pro Series GPS to record position (Figure 2-3).

To correct for tidal fluctuations, water level was simultaneously recorded by an In-situ"

miniTroll submersible data logger in the middle of the bay. Corrections for tide were

made by relating changes in the water level to the recorded depth. The top of the well

containing the data logger was surveyed in to a benchmark on the island, thus enabling

the conversion of water depths to an absolute elevation (NAD 88). The elevation data set

was interpolated using an ordinary krigging with a lag size chosen to minimize RMS

error. The digital elevation model (DEM) was created by converting the interpolation

into a grid using a cell size of 1 m.

After examining the DEM, aerial photos, and vegetation/elevation patterns in the

natural habitat, soil sampling locations in the bay were chosen to represent areas in

differing landscape positions (Figure 2-4). Twenty-three acrylic push cores (inner

diameter = 6 cm) deployed along six transects were taken within the island. Three

additional cores were taken from the southern side of SL 15 in the surrounding seagrass.

Munsell" soil color, shell content, hand texture, horizon designation, n-value, depth, and

root occurrence were recorded. The soil cores were described and sampled in the lab.

Representative subaqueous soils were collected from the seagrasses surrounding SL 15










(Figure 2-4). Locations were chosen to capture a diversity of seagrass species covers.

Six soils were described with the following cover: S. fihforme, S. fihforme and T.

Testudinum, H. wrightii, 7 testudinum and H. johnsonii, and H. wrightii and S. fihforme.

Munsell" soil color, shell content, texture, horizon, n-value, depth, and root occurrence

were recorded in situ.

Although soil surveys traditionally examine soils to a depth of 2 m, the cores in

the bay were deployed to maximum depths between 40 cm and 60 cm. Two-meter

observations are important on land because of agricultural or construction limitations, for

example. Because SL 15 was designed specifically for seagrass mitigation, however, this

study focused on the upper (>50 cm) portion of the soil which would most likely be

influential in the seagrass rooting zone. For laboratory analysis, subaqueous soils from

the natural and constructed habitat were sampled by horizon, but an integrated analysis

on the 0 to 10 cm range was also performed to represent soil characteristics in the rooting

zone of H wrightii and Halophila species (Zieman and Zieman, 1989). The A horizons

from the natural habitat were greater than 10 cm and therefore analyzed as described. For

the soils from the constructed habitat in which the top horizon was less than 10 cm,

composite OM content and particle-size distribution were calculated using a weighted

average based on thicknesses. A soil with an A horizon from 0 to 3 cm, and an Cg

horizon from 3 to 10 cm, for example, were analyzed by horizon, but the A horizon was

assigned a weight of 0.3 and the Cg horizon a weight of 0.7. Organic matter content was

calculated by loss on ignition in a 5500 C muffle furnace for four hours (Heiri et al.,

2001). Particle-size distribution was determined by the pipette method (Gee and Bauder,










1965). Carbonate content was determined on a subset of samples by acidification with

20 mL 2M HCI (Kennedy et al., 2005).

Benthic Observations

Estimates of algae and seagrass coverage in the bay were made throughout the

study. In March 2006, the extent and distribution of Gracilaria sp. (drift algae) in the

bay were visually estimated in north-south transects and interpolated (Figure 3-12A).

The percent cover for Gracilaria sp. was recorded in 5 m2 areas. In September 2006,

seagrasses growing in the bay were mapped along east-west transects. Because seagrass

shoots were often spaced farther than 1 m apart, visual estimates of percent cover were

not sensitive enough to capture spatial patterns in seagrasses. Instead, the number of

shoots in a 2 m radius around the observer was used to capture the sparse, but frequently

occurring, seagrasses. Shoot counts, percent cover where applicable, and species were

recorded along east-west transects (Figure 3-13A).

Objective 2: Transplant Experiment

Six 1.5 x 1.5 m transplant plots were constructed in May 2006. Three plots within

the bay and three on the southern side of SL 15 were established (Figure 2-4a).

Transplant quadrats TQ-2, TQ-3, and TQ-6 were planted on May 11, and TQ-1, TQ-4,

and TQ-5 were planted on May 26, 2006. Transplant quadrats TQ-1 and TQ-3 were

located on mounds, and TQ-2 was located at a lower elevation. Previously determined

Kd demonstrated that there was sufficient light for seagrass growth at each site, therefore

minimizing light availability as a factor. Transplant quadrats TQ-4, TQ-5, and TQ-6,

were situated based on surrounding seagrass cover. Sites were located where H. wrightii

was the dominant species, where existing seagrass appeared undisturbed, and where

unvegetated bottom was available for planting. H. vi igthrii was selected as the species to









transplant because of its availability as wrack around SL 15 and its previous success in

bare-root planting efforts (Fonseca et al., 1998).

The plots were constructed using four steel rebar posts (2 cm diameter) at each

corner, which were then covered with a PVC pipe to enhance visual identification (Figure

2-5b). H. wrightii fragments with more than six shoots were collected and stored in

seawater for less than one hour until planting. After gently pushing the roots

approximately 1 to 2 cm into the soil, the fragments were anchored by a bamboo-skewer

according to Davis and Short (1997). Nine fragments were planted in each plot and

spaced 0.5 m apart. A 1-inch chicken-wire cage was wrapped around each plot to

prevent grazing (Figure 2-5b). Shoot counts were recorded on May 11, May 26, July 10,

August 8, and September 8, 2006. Fouled cages were cleaned following each count.

Objective 3: Habitat Suitability Model

When comparing the natural and constructed habitat at SL 15, statistical analyses

were used to assess any significant differences between the two environments. To

illustrate any spatial relationships and variability that might appear in the data,

geostatistical analyses were used to create map layers that would show differences in the

constructed and natural habitat at SL 15. Current velocities were interpolated using a

first order, local polynomial interpolation (75% local). The interpolation was converted

to a raster grid using a cell size of 1 m. For each grid cell, the mean current velocity from

outside SL 15 was subtracted from the interpolated value, resulting in a map which

showed spatial distributions of deviation from the mean outside value. This calculation

was then classified to differentiate areas which were one, two, or three standard

deviations above and one, two, or three standard deviations below from the mean outside

value.









A similar technique was used to map and compare differences in subaqueous soil

properties. Landscape units were visually delineated on the DEM, thus grouping areas of

similar soil properties. These properties were classified as being significantly different or

similar to soils in the natural habitat. The habitat suitability model essentially combined

these map layers, showing the intersection of areas where light availability, soil

properties, nutrients and current velocities were comparable to the seagrass beds outside

of SL 15.


Figure 2-1. Light meter apparatus. A 2xn, LI-COR 192SA underwater light sensor
attached to a mounting frame and PVC pipe.








































Figure 2-2. Soil porextractor (Nayar et al., 2006). The unit is pushed into the soil to the
desired depth. A parafilm membrane within the PVC is pierced, breaking a
vacuum and allowing porewater to enter the pipe.




















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Figure 2-3. Bathymetric sampling locations. Water depth was recorded at each point with

a meter stick. Position was recorded with a Trimble" GPS. Depths were

corrected for tidal fluctuations by referencing a submersed datalogger, which

was simultaneously recording changes in water height.




































Figure 2-4. Soil sampling locations in the bay and natural habitat. The numbers next to
the yellow dots show the transect and core number. These locations were
chosen to represent different landforms in the bay based upon the aerial
photograph (above) and the digital elevation model. O-1 O-3 were cores
taken from the outside seagrasses (green). The pink dots around the outside of
SL 15 were soils from different seagrass species cover (samples "SG-1," etc.
Appendix A).


Figure 2-5. Transplant quadrats location and construction. A) Location of transplant
quadrats B) Picture of TQ-3 with PVC/rebar posts and 1" caging.














CHAPTER 3
RESULTS

Objective 1: Environmental Conditions

Light Availability

Light extinction coefficients (Kd) and chlorophyll concentrations were measured to

characterize the light environment affecting seagrasses in the constructed and natural

habitats at SL 15. Chlorophyll a (Chl a) concentration was analyzed as an indicator for

the amount of phytoplankton in the water column. Corrected Chl a refers to samples

which were acidified to remove phaeophytin, a degradation product which can interfere

with measurements. The average corrected Chl a content was 2.12 & 0.20 Cpg L^1 within

the bay (n=3) and 2.20 + 0.28 CpgL^1 (n=3) outside of SL 15 (Table 3-1). Uncorrected

values (including phaeophytin) were 2.91 & 0.22 Cpg L^1 in the bay and 2.97 & 0.31 Cpg L^1

outside of SL 15. A Kruskal-Wallis test (a =0.05) showed no significant differences in

corrected Chl a concentration in the bay and natural habitat.

The Kd ValUeS with the bay ranged from 0.17 m-l to 0.75 ml (n=13) and from 0.35

m-l to 0.74 m-l (n=1 1) on the outside of SL 15. The average Kd for the inside bay was

0.54 (A 0. 18), and the outside Kd WaS 0.55 (f0. 12). The average Kd ValUeS calculated

from the bay and the outside natural habitat showed no significant differences within the

two environments (Figure 3-1). Irradiance values on the bottom (ca. 10 cm above soil

surface) ranged from 850 to 1964 umol sl m-l and varied with depth and time of day.









Currents

An understanding of the hydrodynamic conditions (velocities, flow vectors) in the

bay and natural habitat was integral when considering how flow patterns might affect

seagrass colonization and bed maintenance. The mean current velocities in the bay and

outside of SL 15 were statistically compared, but more detailed maps of flow vectors

were also created to assess circulation patterns caused by the flushing channels and

bottom topography.

Average flow velocities revealed no significant differences between the area inside

the bay and the outside area supporting seagrasses (Figure 3-2). The average velocity for

the outside was 11 & 5 cm s-l on the incoming tide and 9 & 4 cm s-l on the outgoing tide.

The average velocity for the bay was 10 & 7 cm s-l on the incoming tide and

11 & 9 cm s-l on the outgoing tide.

Although the averaged velocities showed no significant differences in the two

habitats, the velocities in the bay varied spatially on incoming and outgoing tides. Also,

spatial patterns of flow were different for incoming and outgoing tides. Circulation

vectors in the bay on the incoming tide showed patterns of flow originating from the

southeast and exiting the bay to the northwest into the channel (Figure 3-3a). The

opposite direction of flow occurred on the outgoing tide, with water moving from the

channel, back through the bay, and to the inlet in the southeast (Figure 3-3b). Flow

vectors outside of SL 15 appeared more consistent in direction, either toward or away

from nearby channels.

To visually compare the velocities of the bay to the mean velocity in the natural

habitat, the flow maps from both tides were classified into three categories: faster than,

slower than, and similar to the natural habitat mean. Faster velocities were those which









were between 1 and 2 sd away from the mean. Slower velocities were those between -1

and -2 sd below the mean, and similar velocities were those which were within +/- 1 sd.

The classification of the current flow maps revealed that on the incoming tide, 13% of the

bay had velocities slower than the outside mean velocity, 1% of the bay was faster and

86% of the bay was similar (4a). A classification of the outgoing tide showed that 40%

of the bay had slower velocities, 6% was faster, and 53% had velocities which were

similar to the outside habitat (Figure 3-4b).

Nutrients

Based on a Kruskal-Wallis test, porewater samples from 0 to 5 cm revealed

significant differences in TDKN between the bay and outside habitat (df=1, p=0.024,

a=0.05). The average TDKN content for the bay was 2.535 A 1.007 mg L^1 and the

average TDKN for the outside of SL 15 was 1.267 & 0.573 mg L^1. The median TDKN

for the bay was 2.72 mg L^1 and 1.148 mg L^1 for the natural habitat. No significant

difference appeared in the averages for TDP values between the bay and outside habitat

(df=1, p=0.519, a=0.05). The average TDP in the bay was 0.602 & 0.872 mg L^1 and the

average TDP in the outside was 0.401 & 0.403 mg L^1. The median TDP value in the bay

was 0.177 mg L^1 and 0.335 mg L^1 in the natural habitat.

Digital Elevation Model

The model that best fit the elevation data was generated by ordinary krigging. This

interpolation method was used because it produced a model with relative smoothness (i.e.

outliers carried less weight) and it had the lowest root-mean-square (6.445). A search

neighborhood of 9.4 m was used, meaning that elevations at unknown points were

calculated by considering the elevation values within a radius of 9.4 m. A lag size of









2.2 m was chosen, which grouped elevation points into bins based on their distance apart

(in intervals of 2.2 m) from each other. The lag size and search neighborhood thresholds

were selected based on their ability to produce a precise DEM in the bay. Because over

900 elevation points were collected, the DEM showed a fine-resolution image of the

bottom topography in the bay (Figure 3-5). The lowest elevation was -61 cm (North

American Datum 1988; NAD 88) and the highest was +24 cm (NAD 88). The average

elevation according to the model was -43 A 11 cm (NAD 88).

Subaqueous Soils

The subaqueous soils within the bay appeared to be more heterogeneous with

regard to particle-size distribution, OM content and color than the soils from the

surrounding seagrass beds (Figure 3-6). A typical bay soil consisted of a black (5Y

2.5/1) flocculant (flock) layer, a dark gray (5Y 4/1) A horizon, one to three olive gray

(5Y 5/2) Cg horizons, and a very dark gray buried A horizon (Ab; 5Y 3/1). Flock layers

lack a specific horizon designation by the USDA-Natural Resources Conservation

Service. For this study, they are thus referred to as F horizons. The subaqueous soils

from vegetated areas in surrounding natural habitat were described as having multiple A

horizons with an underlying Cg horizon. The Al horizons were typically black (5Y

2.5/1), and the A horizons beneath were either dark gray (5Y 4/1) or very dark gray (5Y



Thickness of F horizon correlated with topography. Lower elevations appeared to

collect fine materials and accrete a thicker F horizon (Figure 3-7; Appendices A and B).

Higher elevations had thin or absent F horizons and had coarse spoil material (Cg) as the

surface soil. Mixing of color and texture was common among the Cg and Ab horizon. A










clay loam layer was also interspersed among the Cg (5Y 5/1 or 5Y 5/2) horizon in six of

the cores.

Statistical analyses were performed to identify significant differences in soil

properties in the bay and natural habitats (Kruskal-Wallis, a=0.05; df=1). There was no

significant difference in organic matter (OM) content between the natural and constructed

habitats within the 0 to 10 cm depth range (p=0.3 86, H=0.75; Table 3-2). The F horizon

in the bay, however, had significantly higher levels of OM than the A horizon in the soils

from the natural habitat (p=0.000, H=12.57). Percent carbonates varied by horizon, and

were significantly higher in the bay soils compared to the soils from the natural habitat.

Particle-size distribution analysis revealed significant differences in the soils from

the bay compared to the soils from the outside natural habitat (Table 3-2). The A

(p=0.008), F (p=0.014) and Cg2 (p=0.008) horizons from the bay had significantly higher

amounts of silt than the A horizon from the natural habitat. The F (p=0.000) and Cg2

(p=0.008) horizons also had significantly higher amounts of clay than the A horizon from

the natural habitat. There was greater variation in particle-size distributions for the bay

than in the natural habitat. The dominant textures of soil in the surrounding seagrasses

were sandy loams, loamy sands and sands. Textures in the bay included clay loam, sandy

clay loam, sandy loam, loamy sand and sand.

The high amounts of clay (up to 35%) in the bay soils was also reflected in Hield

observations. Walking in the bay appeared to significantly cloud the water with particles

that remained suspended for up to an hour. This effect was not noticed in the natural

habitat. As an experiment, a handful of Cg horizon from the bay and A horizon from the

natural habitat were simultaneously dropped into the water and allowed to settle. The









settling time of the Cg2 horizon was much greater than for the outside A horizon (Figure

3-8). The long (>2 minutes) settling time of clay particles in the bay can be explained by

Stoke' s Law which states that settling velocities are a function of particle diameter.

Additional comparisons of soil properties were made in order to address the

hypothesis of the Ab horizons in the bay being relict A horizons from a seagrass bed.

The chemical and physical properties of the Ab and A horizon from the natural habitat

were tested for significant differences. Based on Kruskal-Wallis (a =0.05), no significant

differences existed between the Ab horizons and A horizons with regard to percent sand

(p=0.254, df=1), but there was a significant difference in OM content (p=0.039, df=1).

Similar colors (5Y 3/1 and SY 2.5/1), as well as the presence of dead roots in the Ab

horizon (Appendix A) also supported the hypothesis prior of seagrasses occurrence in the

area which SL 15 was created (Figure 3-9).

At SL 15, a subaqueous soil survey (1:1,200) was created in order to map the

distribution of soils in the bay using methods similar to terrestrial soil surveys and to

facilitate a comparison of soil properties in the nearby natural habitat. Ellis (2006) listed

the steps for creating a soil survey:

1. Observe patterns in vegetation and landforms using aerial photography, digital
elevation models, and Hield observations.

2. Observe patterns in soil properties via Hield observations, as related to the
vegetation and landform patterns.

3. Superimpose patterns of soils, vegetation, and landscape on the local geology to
develop a conceptual soil/landscape model.

4. Describe and define the soil map units.

5. Create a physical representation of the conceptual soil/landscape model by spatially
delineating aerial photography into units that represent the various landforms and
associated soils map units.









Step 1 was carried out through the creation of a Eine-scale DEM and an analysis

of recent aerial photography (see Chapter 2). Observations in the field (Steps 2 and 3)

confirmed relationships between landscape position (elevation) and soils. Deeper

elevations (-3 8 to -60 cm, NAD 88) were associated with thicker F horizons than soils

which were located on mounds (-10 to -33 cm). Using these elevation thresholds, the

DEM was classified into three landscape units: mounds, flats, and depressions (Steps 4

and 5; Figure 3-10). The areas with elevations between -33 and -38 cm (NAD 88) were

labeled as flats. Mounds and depressions which were smaller than approximately 50 m2

were not delineated. The flats landscape unit therefore included microtopographic

features such as small mounds and depressions.

The remaining steps of a soil survey include refining the model and populating

each map/landscape unit with a soil identifier or the taxonomic classification, as defined

by Soil Taxonomy (Soil Survey Staff, 1999; Ellis, 2006). In the United States,

taxonomic classification is based mainly "on the kind and character of soil properties and

the arrangement of horizons within the profile" (Wettstein et al., 1987). Based on these

criteria, the soils from the natural habitat were classified as loamy, siliceous,

hyperthermic Typic Endoaquolls (Soil Survey Staff, 2003). Soils in the bay were also

classified as loamy, siliceous, Typic Endoaquolls (Soil Survey Staff, 2003).

Although soils in the bay and natural habitats were taxonomically identical, the

bay soils (0 to 10cm) had significantly different properties from soils (0 to 10cm) in the

natural habitat (Table 3-3). Because the purpose of this soil survey was to map soils in

the context of suitability for seagrasses, these differences were considered when refining

the conceptual and spatial model of soils in the bay. The landscape units were referred to










by their non-taxonomic term (depression, flat, mound) to convey that differences exist

and might potentially affect seagrass growth.

In a terrestrial system, the arrangement of horizons is important because of water

table fluctuations, or limitations with agriculture and development. For the subaqueous

soils in the bay, however, an emphasis was placed on the 0 to 10 cm range because it is

the rooting zone for seagrass species likely to colonize the bay (Zieman and Zieman,

1989; Creed, 1997). Also, the arrangement of horizons in the bay was fairly consistent

throughout in that an F horizon or A horizon was followed by a Cg horizon and then an

Ab horizon (Figure 3-7). Each horizon's thickness varied throughout the bay, most likely

as a result of the constructions process, but the Ab horizon appeared in every soil, 8 to

30 cm below the soil surface. In a terrestrial survey, this underlying horizon throughout

the area might classify the landscape into one similar map unit. Thus, in the context of

seagrass growth, a classification based on horizon arrangement below the F horizon

would not provide sufficient information.

A classification of the soils in the bay was therefore based upon particle-size

distribution and OM content in the 0 to 10 cm range for each landscape unit. These

properties for each landscape unit were then compared to the soil properties in the natural

habitat (Table 3-3). Results showed that the depression landscape unit had particle-size

distribution and OM content values which were significantly different to values in the

natural habitat. Although both the mound and flats landscape units had one soil property

which was significantly different (OM content and sand %, respectively) to the soils in

the natural habitat, the mound landscape unit was classified as significantly different and

the flats was classified as similar to the nearby environment (Figure 3-11). The










distinguishing factor of the mound landscape unit was that on low tide, certain areas were

exposed, suggesting a potential stressor for seagrass recruits.

Benthic Observations

On two occasions, observations of benthic colonization were made. In the spring

of 2006, Gracilaria sp. formed a dense mat on the bottom of the bay. Estimates of

percent cover in a 5 m2 area were made in transects and interpolated (Figure 3-12). The

spatial distribution of Gracilaria sp. followed an east to west gradient, with higher

concentrations on the west side of the bay. Over the summer, mats of the blue-green

al gae Lyngbya nzajuscula formed in the outside sea grasses. Acanthophora spicifera,

Hypnea sp., and Caulerpa sertularioides were also observed in both the bay and the

natural habitat.

In May 2006, the first observation of seagrass colonization in the bay was made.

H. vi igthlii and S. filifornze appeared to be growing with a concentration on the west part

of the bay, similar to the Gracilaria sp. distribution. H. johnsonii was also observed as

growing in patches, with higher concentrations in mounded areas. Single blades of T.

testudinunt and H. englenzanii were also noted. Epiphytes appeared to cover all

seagrasses in the bay. A seagrass survey was performed in September to estimate the

number of shoots growing in the bay. Sampling locations were along transects and the

number of shoots counted in a 2-m radius (Figure 3-13a). The dominant species was H.

wrightii, which comprised approximately 90% of the seagrass recruits, excluding H.

johnsonii (Figure 3-13b). The seagrass survey was then interpolated (local polynomial,

80%) to show seagrass abundance per square meter (Figure 3-14). Because of H

johnsonii' s small structure, percent cover was used to quantify its extent of growth.









Shallow areas in the west part of the bay had up to 20% cover by H. johnsonii (Figure 3-

13 and Figure 3-15).

Objective 2: Transplant Experiment

In TQ-1 and TQ-3, 100% mortality occurred. The remaining transplant quads had

various levels of survivorship (Table 3-4). TQ-2 lost 14% of its total shoots, TQ-4 lost

45%, and TQ-5 and TQ-6 lost 9% and 34%, respectively. In TQ-2 and TQ-5, shoot

counts decreased during the first two months, but new shoots grew into the quadrat and

led to an approximate increase of 50% between July and August. The new shoots were

determined to be separate recruits from the original transplants because they appeared to

be growing through the caging material, into the quadrat. The averaged shoot number

loss was 71% in the bay and 29% loss in the natural habitat.

During monthly monitoring, the cages were cleaned of fouling. Dried drift algae

and dead seagrass fragments comprised most of the trapped material in and around the

caging material. Estimates of cage fouling after one week revealed that 60% to 90% of

the cage mesh was covered in flotsam (Figure 3-16a). Irradiance values were measured

in TQ-1 between 10:00 and 11:00 a.m. to quantify the amount of light blocked by the

cage fouling. Bottom irradiance on the east side of the cage which experienced mid-

morning shading was 50% of surface irradiance. The non-shaded west side had an

average bottom irradiance of 82% of surface irradiance. In the transplant quads which

had some survival, an average of 85% loss occurred on the east side of the quadrat. On

July 26, 2006, it was noted that the cages on TQ-2 and TQ-3 were damaged after a strong

wind event. Half of the cage appeared to be intact, but the other half had been lifted over

the rebar stakes. TQ-1 remained intact, but the transplants had completely disappeared

from TQ-1 and TQ-3. No signs of grazing were present on the blades in TQ-2.









Lyngbya majuscula was the dominant algae in both habitats that covered the cage

and seagrass blades. Epiphytic algae also covered seagrass blades in both the constructed

and natural habitat after one day from planting (Figure 3-16b). Callinectes sapidus (blue

crabs), Lagodon rhomboides pinfishh) and Sphoeroides maculates (northern puffer) were

observed in the outside quads.

Objective 3: Habitat Suitability Model

A habitat suitability model (HSM) was created to illustrate the extent of "suitable"

areas for seagrass growth in the bay. Suitable, for this study, was defined as similar to

conditions in the natural habitat. The HSM was the synthesis and culmination of data

gathered from Objective 1 and was generated by combining the areas in the bay which

had current and soil conditions that were similar to conditions in the natural habitat. For

currents, similarity was established as areas with water velocities within 1 standard

deviation of the outside mean velocity on both incoming and outgoing tides (Figure 3-4).

Soil conditions in the bay were tested for significant differences in OM content and

particle-size distribution to soils in the natural habitat. The classification of landscape

units by these differences provided a map with soil properties which were similar to

properties outside of SL 15 (Figure 3-12).

The HSM calculated areas in the bay which formed the intersection of three input

layers: the classified maps of current velocity (incoming and outgoing tide, Figure 3-3, 3-

4) and the classified landscape map units (Figure 3-11). Because Kd ValUeS in the bay

were determined to not be significantly different from the outside natural habitat, the

entire bay was classified as suitable with regard to light availability. Although TDKN

values differed in the two habitats, the small number and high variability of porewater

samples (n=14) hindered a spatial interpolation of the data, thus nutrient conditions were









not included in the HSM. The intersection of the areas which had properties similar to

the natural ecosystem comprised 14% of the bay (Figure 3-17).

Table 3-1. Chlorophyll a (Chl a) values from each transplant quadrat.


Location Habitat Cr a (pg/L) Cr a (pg/L) n
TQ1 Bay 2.23 2.99 1
TQ2 Bay 2.23 3.08 1
TQ3 Bay 1.90 2.67 1
TQ4 Natural 2.23 3.17 1
TQ5 Natural 2.46 3.13 1
TQ6 Natural 1.90 2.62 1


Corrected


Uncorrected


T 1


1


No significant difference (Kruskal-Wallis test; df=1, a-
corrected Chl a values in the bay and natural habitat.


=0.05, p-value=0.663) occurred in


1.00

0.90

0.80

0.70

0.60

0.50

0.40

0.30

0.20

0.10

0.00


Kd (m-1


Figure 3-1. Average Kd ValUeS in the natural and constructed bay habitat. Although Kd
values varied with depth and time of day in the natural and constructed bay,
there was no significant difference in average Kd ValUeS for both habitats
(Kruskal-wallis test; df=1, p=0.829, a=0.05).


Natural Bay











Outside of SL 15


20



15



10


Inside Bay


0


Incoming Tide


Outgoing Tide


I


Tidal Period

Figure 3-2. Average water velocities on both outgoing and incoming tides. Based on a
Kruskal-Wallis test, no significant differences (a=0.05) occurred in the bay
and natural habitats on the outgoing tide (df=1, p=0.915) and incoming tide
(df=1, p=0.280).




































100 m


100 mi


Cu rrent Velocity (c m/s)

High : 22


c




tN


Current Velocity (cmis)


4)1


i


I
I
~Jb


HN


Figure 3-3. Current flow velocity and direction in the bay. Incoming tide (A) and
outgoing tide (B) are shown. Water flows were faster near flushing channels
and flow directions followed paths to either the inlet in the southeast, or
intercoastal waterway to the northwest.


--
I~-5~,~;,u.,
~ ,.
1,JI~3=';JI .1
=_:n



B

























N u


I Slower (>-1 sd)

I Similar (-1 sd- +1 sd:

SFaster (>+1 sd)


86%


1 3%


100 m


I Similar (-1 sd +*1 sd)


tN


SFaster (>+1 sd)


100 m


Figure 3-4. Classified maps of current velocities in the bay. The incoming tide (A) and
outgoing (B) tides are shown. The mean velocity from the natural habitat was
subtracted from the original map and then classified into three groups: faster,
slower, and similar to the natural habitat.






























Elevation (cm, NAD 88)
E +2- 25
S+2--10
4..~~ 1" -10 --20
......1 -20 --27
S-27 --33

"100 m 5 N m 3-3-38--46
H -46 --60

Figure 3-5. Digital elevation model of the bay. More than 900 water depths were collected in the field, corrected for tide, and related
to surveyed benchmarks on SL 15. Elevation values were based on the NAD 88 datum.


Digital Elevation Model









10 cm




10 cm




20 cm



30 cm




40 icm


Figure 3-6. Representative subaqueous soils taken from the natural outside habitat (left,
O-1) and inside the constructed bay habitat (right, T2-3). The soils from the
natural habitat had dark, homogenous colors throughout and multiple A
horizons. Soils from the bay were characterized by an F horizon, followed by
an A or Cg horizon. The F horizon was typically black (5Y 2.5/1), but
appears light brown in the image because of the oxidized surface. The Cg2
horizon had a clay loam texture. The Ab horizon was hypothesized to be a
relict A horizon from a pre-existing seagrass bed.








Transe ct 6


-30


-40


-50



aco
0


O
-


T6-1


T6-2



100 m N~


TGj_3


T6-4


Distance along transect (m)


Figure 3-7. Soils from representative transect 6 from the bay. As elevation decreased
(deeper), an increase in F horizon thickness appeared. The Cg horizon was
spoil material of varying thickness. The Ab horizon usually occurred between
20 to 30 cm below the surface of the soil.


I



r












Dominant
Horizon Color OM % Sand % Silt % Clay % CaCO3 % Sand Size n
F 5Y 2.5/1 6.4 & 2.6 55 A 12 25 A 17 20 + 8 2.6 fine 15
A 5Y 5/2 2.9 &1.7 68 & 21 20 & 21 12 & 6 2.7 fine 9
A/Cg 5Y 4/1 3.8 & 2.1 72 & 14 10 & 6 18 &9 -fine 5
Cg, Cgl 5Y 5/1 2.8 &1.2 77 & 18 12 & 16 11 &9 1.3 medium 20
Cg2 5Y 5/2 6.7 & 2.6 38 & 25 27 & 13 35 A 13 2.2 fine 8
Cg/Ab 5Y 4/1 3.3 & 0.8 85 & 5 6 &2 9 &2 very fine 3
Ab 5Y 3/1 2.9 & 0.8 84 & 12 7 & 13 9 &3 0.2 very fine 18
L0-10 cm 3.8 & 1.6 72 13 15 2.7 fine
Al 5Y 2.5/1 3.4 & 1.0 81 & 5 9 &3 11 &2 0.4 very fine 6
A2 10Y 2.5/1 2.2 & 0.7 86 & 7 5 &3 9 &4 very fine 6
A3 2.5Y 2.5/1 1.8 f 0.5 89 f 4 4 &2 7 &3- very fine 6
A4 5Y 3/1 1.8 & 0.7 88 & 4 5 A1.6 8 &2 very fine 6
C 5Y 4/2 1.5 f 0.1 93 2 5 -very fine 6
0-10 cm 5Y 2.5/1 3.3 & 0.9 85 6 9 very fine 30
Dashes represent no data available. Organic matter is OM.


43


Table 3-2. Average subaqueous soil properties from the bay and natural habitat at SL 15.


Bay







Natural












Cg fromm b;ay)



A (from outside)






: Time = 10
seconds











II *E ii~i~ ~ TT J1 Time = "1 minute







Figure 3-8. Settling characteristics of soils from the bay and the outside habitat. The
higher amounts of clay in the Cg horizon than in the A horizon were evident
in the time taken for particles to settle out of the water column. The
implications are that if disturbed, soils in the bay might reduce light
availability and affect seagrass.










































Sand %
68 (0.006)
74 (0.032)
75 (0.083)


Silt %
16 (0.046)
10 (0.121)
12 (0.073)


Clay %
16 (0.007)
16 (0.050)
12 (0. 116)


Landscape
Unit
Depression
Flat
Mound


A (from outside)


Ab (from bay)


Dead roots from Ab


Figure 3-9. Characteristics of the Ab horizon from the bay. A) The Ab horizon and A
horizon from the bay and natural habitat. Color, shell content, particle-size
distribution and OM content were not significantly different in both soils. B)
Dead seagrass roots in the Ab horizon.




Table 3-3. Average soil properties from 0 to 10 cm in each landscape unit. Bolded
values are those with p values (in parenthesis) which were significantly
(Kruskal-Wallis test; a=0.05) higher or lower than soil properties from the
natural habitat.


F horizon
thickness (cm)
2.61
1.57
1.00


Organic Matter
4.52 (0.046)
3.66 (0.350)
2.51 (0.002)





Elevation (cm, NAD 88) 22

M +2 --10
0 1-10 --20
Mond 1 -20 -27
".." (..............I-27 -33
Flat { 33 -38

Depressions I 3 4
i.-46 -60


------------------------1 0 0 m

_i -

.C


.,i~E


*'
d~'ir"""`
'


.I


I ,~ii;;I r
r


1:1,200


Figure 3-10. Digital elevation model showing delineations of landscape units. Three
units were created based on elevation: mounds, flats, and depressions. Soil
sampling locations (pink dots) were selected to represent soils from the
different landscape units. The green areas (-10 to +25 cm) were elevations
along the shoreline which were exposed at medium and low tide. Soils in the
flushing channels were not sampled.


.."C'


I;




















|N

-- Significantly different

I Similar
'100 m

Figure 3-11. Classified landscape units. The original depressions and mounds were
classified as having soil properties (OM content, texture) in the 0 to 10 cm
range which were significantly different (blue) from soil properties in the
natural habitat, while soils in the flats had similar soil properties (yellow).


































































N


A































B


*0 *


4020
*


son


100 m


r
'"'
~ r~.
P c
r.. Irr
jL~ *
r .~
I~ifF ~T~
~I CI~l'


"


20%


100 m


Figure 3-12. Percent cover map of Gracilaria sp. in March, 2006. Estimates of percent
cover per 5m2 were made at each location (A). Numbers next to each point are
the percent coverage estimates for macroalgae. High concentrations of
macroalgae existed near flushing channels, and in the south-west side of the
bay (B).


*100%



















# Shoots



























a a 0 H. johnsonii
SS. filiforme

O H. wrightii



Figure 3-13. Seagrass distribution in the bay as of September, 2006. A) Shoot counts
were made in a 2-m radius around each point (12.6 m2). The pink stars
represent areas that had H. johnsonii cover. The numbers next to each star are
the percent coverage for H. johnsonii at each point. B) Seagrass distribution
in the bay by species present.





















i ~Shoots m-2



Nr 100 m5

Figure 3-14. Seagrass abundance in the bay per m2. The number of shoots was
interpolated (local polynomial, 80%) to show trends in recruit concentration.











































Table 3-4. Total number of shoot counts per transplant quadrat over time. TQ-1, 4, 5, and
6 have "np" for May 11, 2006, because they were not yet planted.
Date TQ-1 TQ-2 TQ-3 TQ-4 TQ-5 TQ-6
5/11/2006 np 77 94 np np np
5/26/2006 113 39 37 111 98 88
7/10/2006 0 35 0 62 83 67
8/9/2006 0 66 0 61 89 58
% loss 100 14 100 45 9 34
Location Bay Bay Bay Outside Outside Outside


Figure 3-15. H. johnsonii recruits in the bay. This patch represents approximately 25%
cover.





52














Epiphytes and
algae on blades


i:










Figure 3-16. Epiphytes and macroalgae at SL 15. A) Cage fouling and Lyngbya
majuscula growing on transplant blades. B) Epiphytic algae growing on
seagrass blades.



















i'


L


ng tide)


Current (incomi
map


Landscape
properties)








N "


Units (soil


current (out oing tide) ~
mnap


i:


Suitable for seag rasses


100 m


Figure 3-17. Habitat suitability model showing the areas in the bay which had current and soil properties similar to those in the natural
habitat outside of SL 15. This model predicted that 14% of the bay was suitable for seagrass growth.


Habitat Suitability Model














CHAPTER 4
DISCUSSION

The transformation of SL 15 was an experimental approach for seagrass mitigation

in the IRL and if successful, its repeatability would be of interest to ecosystem managers.

Seagrasses in the IRL have been cited as having a value of $30,000 ha/yr (Virnstein and

Morris, 1996), showing their importance as the economic foundation of a widely used

fishery. Seagrasses in the IRL are also an integral ecologic component in the most

diverse estuary in North America. Other than light thresholds and nutrient ranges,

however, no specific requirements for seagrass growth in the IRL are published. The

inherent difficulty of dissociating and controlling an ecosystem for analysis means that

while relationships can be demonstrated, declaring specific requirements for a habitat

remains challenging. The approach for this study, therefore, was to compare the

conditions in the constructed habitat with the conditions in the surrounding seagrass beds

as a proxy for growth requirements in the southern IRL. Although more research is

needed to determine the maximum soil organic matter content or current velocity that

IRL seagrasses can tolerate, this study provided a range of values which can be identified

in a healthy seagrass bed. The results from this study also offered baseline data for future

monitoring at SL 15 and additional knowledge of seagrass/landscape interactions.

Soil/Landscape Analysis

The transformation of SL 15 provided a unique context in which pedology could be

applied to an aquatic realm. The excavation of the bay offered a view of recently

exposed subaqueous material and a chance to observe how various soil-forming factors









can develop spoil material into vegetation-supporting soil. Previous geology-based

sediment models described the influence of geology, hydrology, and bathymetry (Folger,

1972; Demas and Rabenhorst, 2001), but certain ecological elements were not included.

Following V.V. Dokuchaiev (1948) and Jenny's (1941) advancement of soil forming

factors, Demas and Rabenhorst (2001) proposed a new model for subaqueous soil

formation:

Ss = f(C, O, B, F, P, T, W, E) (eq. 4-1)

Where subaqueous soil (Ss) properties are a function of climate (C), organisms (0),

bathymetry (B), flow regime (F), parent material (P), time (T), water column attributes

(W) and catastrophic events (E). When applying this conceptual model at SL 15, these

factors have appeared to affect the development of soil characteristics in the natural and

constructed habitats.

Bathymetry

In the bay, bathymetry was observed as influencing the development of subaqueous

soil characteristics. Depressional landforms (-38 to -60 cm, NAD 88) were related to

relatively high (> 4%) concentrations of OM content (Figure 4-1). This relationship

could have been caused by the accumulation of algae in depressional areas which

senesced in place and added organic matter. Suspended particulate OM near the bottom

could also have been trapped by depressional features.

Thickness of the F horizon was also related to bathymetry (Figure 4-2). The

accretion of algae in depressions (-3 8 to -60 cm, NAD 88) most likely contributed to the

development of the F horizon through trapping of fine-sized particles. The

decomposition of algae in depressions would also explain the high average OM content

of the F horizon (6.2%).










Regression analyses were performed to relate currents, bathymetry, and soil

properties, but no significant statistical relationships appeared other than OM content to

elevation, F horizon thickness to elevation and percent silt to current velocity (Figure 4-

3).

Flow Regime

Interactions of bathymetry and flow energy might also explain the accumulation of

detritus in depressions and thus F horizon thickness and OM content. Flow velocities

were approximately four to Hyve times slower (< 10 cm/s) in depressions (-3 8 to -60 cm,

NAD 88) than in mounded areas, which likely reduced bottom sheer stress and allowed

for particles to settle out of the water column. Lower flow energy could have also

allowed silt-sized particles, which would otherwise remain suspended, to fall to the

bottom. A weak statistical relationship existed between silt content and incoming flow

velocities (r2=0.385, p=; Figure 4-3). The accretion of algal detritus due to slow

velocities could have also affected nutrient dynamics in the depressions. Although

porewater sample locations for this study were selected at random, future sampling for

possible relationships between elevation, velocity, detritus accretion, and nutrient

availability would be of interest.

Parent Material

Parent material might also be of significance when considering the nutrient

dynamics in the bay compared to the natural habitat. Although the IRL is considered to

have terrigeneous quartz parent material (Hoskin, 1983; Short et al., 1993), the

abundance of carbonate shells in the bay soils may indicate different source geology than

the dominantly siliciclastic material in the surrounding seagrass beds. Loss of CaCO3 by

acidiaication indicated that the F horizon had the highest amount of carbonates, although









the Cg horizons had the highest shell content of the bay soils (Table 3-2; Appendix A).

The carbonates in the Cg horizons were mostly coarse-sized particles (>1 mm) and were

possibly incompletely dissolved by 20 ml of 2 M HC1. The carbonates in the F horizon

were smaller and more likely to be acidified. The Cg horizons also had a higher

percentage of sand than the F horizons (Table 3-2), which may have buffered its percent

weight lost after acidification, whereas the loss of heavy carbonates in the more silty

F horizon could have resulted in a higher percent weight change. The high amount of

carbonates in the bay soils might have long-term effects on nutrient storage and flux

(Kitano et al., 1978; Short et al., 1993b).

The presence of clay loam textures in the Cg horizons further suggested differences

in source material between the two habitats. The clay loam was hypothesized to be a

relict soil from a mangrove bed which became mixed with spoil material during the

construction process. Although this soil occurs intermittently in the bay, its influence on

the light environment was notable. Clay particles became easily suspended when

disturbed, thus clouding the bay water for several hours. Increased amounts of clay in the

bay soils might also have future impacts on nutrient retention and mineralogy.

Climate

Climate, on a local scale, could also be contributing to the geochemical properties

of soils in the bay. For example, localized increases in water temperature in the bay

might be of significance for seagrass growth, benthic activity and detrital decomposition.

On a low tide in July, water temperature within the bay was more than 5o C higher than in

the natural habitat, possibly because of restricted flow exchange through the flushing

channels. Studies have shown that increased temperature and salinity exacerbate the

detrimental effects of sulfide toxicity (Carlson et al., 1994; Koch and Erskine, 2001).









Although soil temperatures were not measured in this study, long-term temperature

monitoring would be an interesting component of future biogeochemical patterns in the

bay.

Organisms

Although not included in sediment models (Folger, 1972), organisms are as

influential for aquatic soils as they are in terrestrial systems. Through chemical

additions, such as organic matter deposits, and physical mixing, benthic flora and fauna

play an integral role in diagenetic processes. In the natural habitat outside of SL 15, the

difference in soil color between vegetated and non-vegetated areas are indicative of how

seagrasses have increased, either through the trapping of fine particles, or turnover of

biomass, the carbon content of the soil on which they grow. For the subaqeuous soils in

the constructed habitat, observations of burrowing crabs and senescent macroalgae

indicated that the newly created habitat is already subj ect to biotic engineering.

Time

The influence of time was evident in subaqueous soil characteristics in the bay and

natural habitat. Significant morphological differences in the soils from both habitats can

be readily explained by the time needed for formation. The Ab horizons in the bay had

color, texture, and OM content that was similar to the A horizon from the natural habitat,

thus supporting the hypothesis that SL 15 was built on top of a pre-existing seagrass bed.

The subaqueous soils from the natural habitat have therefore experienced at least 60 years

of development. The subaqueous soils in the bay were plowed by construction

equipment in the last 12 months. Within the last year, however, changes have occurred in

the upper 10 cm of soil within the bay. Fine particles have accreted in depressions and

might thicken over time, possibly leading to bathymetric features becoming more









uniform. The flow of water from the mangrove zone during outgoing tides has also

created gullies and deltas on the north bank of the bay, continually reshaping the bay

geomorphology.

Although significant differences appeared in the subaqueous soils in the bay and

outside habitat, time could be an important factor when comparing the two ecosystems.

Difficulty arises when discussing at what point a constructed system reaches equilibrium,

but long-term observations of subaqueous soil development might reveal changes

indicating that the habitat in the bay is more closely resembling the surrounding natural

environment.

Catastrophic Events

Catastrophic events were not examined during the study, but in the fall of 2004,

Ft. Pierce experienced two maj or hurricanes (Frances and Jeanne). Baseline data for

subaqueous soils near SL 15 were not available for comparison, but the shallowness

(average depth <2 m) of the IRL suggests that catastrophic wind events might have an

effect on surface subaqueous soils. Sandbar movement and vegetation removal is likely

if a storm were to hit on low tide. Strong wind events might be of importance in the bay

considering the high amounts of clay that could become re-suspended. Although not

specified as a catastrophic event (Demas and Rabenhorst, 2001), dredging and human

disturbance should also be inferred as a forming factor. The excavation of the bay in SL

15 was performed with large construction equipment which moved 69,000 m3 Of SOil. If

the flushing channels in SL 15 require dredging in the future, additional large-scale soil

movement might affect subaqueous soils in the bay.









Water Column Attributes

The effects of water column attributes were not analyzed and merit further attention

at SL 15 with regard to organic matter deposition and nutrient concentrations. Long-term

monitoring of water quality properties such as total suspended solids, dissolved oxygen

and chlorophyll might contribute to an understanding of how water column attributes

affect soil properties in the bay.

Subaqueous Soil Survey

The subaqueous soil survey of the bay revealed that soil properties were most

closely related to landscape position. The thickness of F horizons, as well as the particle-

size distribution and OM content of soils in the bay varied across each landscape unit.

Similar to a terrestrial survey, variation also occurred within each landscape unit,

showing how survey scale can either capture or exclude soil heterogeneity. The fine-

scale of the bay soil survey (1:1,200) was more detailed than a traditional soil survey (e.g.

1:20,000). Despite the 1:1,200 scale, features such as mounds and depressions that were

less than 50 m2 COuld have affected soil descriptions and comparisons to the soils in the

natural habitat. An increased number of samples (n>30), along with DEM validation

points, could have produced a more accurate soil map.

The subaqueous soil survey was also limited in taxonomic terms. As yet,

subaqueous soils lack a clear definition in Soil Taxonomy (Soil Survey Staff, 2003).

Although the soils in the bay had different physical and chemical properties than soils

from the natural habitat, they classify as the same soil because the particle-size control

section for Mollisols is 25 to 100 cm below the surface (Soil Survey Staff, 2003). Most

bay soils had an Ab horizon at that depth, which had textures similar to the A horizon in

the natural habitat, thus their identical classification. Research in Rhode Island produced









a subaqueous soil survey with soil descriptions, such as fine-silty over sandy, mixed,

nonacid, Thapto-Histic Hydraquents, because a buried O horizon occurred in the soil

(Bradley and Stolt, 2003). The unique construction of SL 15, however, prevents an

accurate taxonomic description of the soils present, such as a buried A horizon and

dredged spoil material. These soils are nonetheless important to consider when

describing the physical environment for the purpose of explaining seagrass colonization

and subsequent growth.

Subaqueous soil research at SL 15 contributed to an understanding of

seagrass/soil/landscape interactions in the IRL, but also expanded the geographic range of

subaqueous soil knowledge in the state of Florida. Previous subtropical subaqueous soil

research was conducted in Cedar Key on the west coast of Florida in a near-shore

environment (Ellis, 2006). Results from SL 15 showed that subaqueous soils from an

enclosed lagoon system on the east coast were similar to soils in the near-shore sites on

the west coast. The OM content for both systems averaged less than 5% (Ellis, 2006).

Colors varied slightly, with west coast soils having hues of 2.5Y, as opposed to 5Y in the

IRL. Particle-size distributions from Cedar Key were typically 85 to 95% sand, with a

dominantly medium-sized sand fraction. These soils were coarser in grain size than the

loamy sands near SL 15 which were on average less than 85% very fine-sized sand.

General soil characteristics were similar on both coasts, with dark colors and higher

organic matter in vegetated soils compared to unvegetated soils.

Subaqueous soil research in Rhode Island (Bradley and Stolt, 2003) and Maryland

(Demas and Rabenhorst, 1999) also applied pedology to lagoonal estuaries and

contributed to landscape-level understandings of vegetated aquatic systems. The









investigation of soils at SL 15 followed similar methodologies and concepts from these

previous studies, such as the generation of bathymetric maps and the classification of the

landscape into soil map units. Adaptations were made, however, for soil sampling

techniques. While previous studies employed bucket augers, McCauley peat samplers

and vibracores (Demas et al., 1996; Bradley and Stolt, 2003; Ellis, 2006) preserving soils

from the IRL for description and analysis required acrylic push-cores.

In the larger context of soil science, the results from this study propose the addition

of the F horizon to the Soil Survey Handbook. Aquatic habitats with rooted vegetation

attenuate energy and most likely accumulate fine-sized particles. Because this layer

occupies the subaqueous soil surface, its properties could be of biogeochemical

significance for seagrasses and should therefore have a designated term. The upper 3 to

5 cm of soil in the bay and natural habitat was characterized by cohesive particles which

were most likely deposited by sedimentary processes, such as microalgal precipitation.

Although the F horizon had n values greater than 1, it was more consolidated than a

nepheloid layer, which in sedimentology is a layer of highly turbid bottom water

(Chambers and Eadie, 1981). Soil Taxonomy (1975) describes limnic materials that

share similar properties to the proposed F horizon, the term "limnic," however, connotes

freshwater conditions. The F horizon could therefore possibly be defined as "organic or

mineral surface soil material which can be found in association with coastal submerged

aquatic vegetation and originates from depositional processes."

Light Availability

During the 1990s, more than 60% of seagrass literature focused on light (Koch,

2001). Because of the importance of light for photosynthesis, this parameter has been

thoroughly studied and was the initial measurement in the bay to determine the










possibility that seagrasses could persist in SL 15. The water column within the bay had

Kd ValUeS which were similar to the outside of the island and demonstrated a light

environment suitable for seagrass growth. Irradiance values showed that an average of

82% of surface light was reaching the bottom of the bay, well above the minimum

threshold 23% to 37% reported in the literature for H. wrightii and S. filiforme (Gallegos

and Kenworthy, 1996; Kenworthy and Fonseca, 1996).

Light availability is in large part, a function of suspended particles in the water

column. Thus the lack of differences in Kd ValUeS in the bay and natural habitat inferred

that each environment shares similar water column attributes. Chlorophyll a

measurements supported the idea of similar water characteristics in both habitats. No

significant difference in chlorophyll a measured in the bay and the amount measured in

the surrounding seagrass habitats. All chlorophyll a values were also well below the

mean for the south IRL (12. 1 Cpg/L; 1988-1994) as reported by the St. Johns River Water

Management District (Sigua et al., 1999). Although light conditions in the bay were

deemed as sufficient for seagrasses, the abundance of potentially light attenuating factors

including macroalgae, epiphytes, and clay particles suggests that long-term monitoring of

irradiance in the bay would be an asset to the future management of water clarity in SL

15.

Hydrodynamics

The effects of hydrodynamics on seagrass ecology/physiology and geochemistry

have been demonstrated. Seagrasses in the IRL grow in a diversity of flow regimes,

ranging from channels near inlets to protected deep-water coves (Virnstein, 1995;

Virnstein et al., 1997). At SL 15, H. vi igthrii grows on a shallow bar next to the channel

where it receives high energy waves from boating traffic, but it also grows in mixed









stands on the south side of the island, a lower energy environment. Koch (1994)

determined a minimum velocity for 7 testudinum to be 5 cm sl for maximum

photosynthetic rates. The duration of this velocity, however, was not specified. The

temporal variation of tidal flows in any habitat then poses the question of how long

maximum and minimum velocities persist. On one part of the tidal cycle at SL 15, 23%

of the bay fell below the 5 cm s-l threshold. The maj ority of the bay, however, was faster

than 5 cm s-l on both tides and--by comparison to the literature and to the surrounding

habitat--was thus classified as suitable for growth of 7 testudinum. The water flow data,

however, was collected as a snapshot of daily conditions and does not reflect the

variability of flow conditions over time. The lack of published flow requirements for

seagrass species in the IRL hinders a supportable conclusion about the bay being suitable

or unsuitable for seagrass growth, but flow velocities were considered to be an important

factor to measure when investigating the physical attributes of the bay.

Although averaged current velocities in the bay and natural habitat were not

significantly different, the data showed many flow observations that were up to four

times as fast as the rest of the bay and thus could have created a higher average.

Velocities and direction appeared to be influenced by proximity to the flushing channels

and possibly bottom topography. The geomorphology of the narrow channels created

areas of constriction and fast flows, while the depressional areas appeared to relate to

reduced current flows. The hydrodynamic data in the bay on both tides showed that

certain areas repeatedly experience faster current velocities, while areas in the center of

the bay experience a wider range of flow speeds, depending on tidal strength and bottom

features.









Interactions of current velocity, soil texture, and organic matter accretion have been

previously cited as being important for seagrass health in the IRL. Morris and Virnstein

(2004) observed an area in the northern IRL which experienced a loss of 100 ha of

seagrass which they hypothesized to be caused by its restricted flushing abilities. They

noted that a 10 to 15 cm thick "layer of organic detritus and ooze" had built up and

suggested that the lack of proper circulation and increased sulfides led to a die-back

event. Although no statistical relationships appeared between current velocity and OM

content or F horizon thickness in the bay, the continual accretion of silt and detritus in

low energy areas in the bay might be an important variable to monitor over time.

Nutrients

A baseline assessment of porewater nutrients at SL 15, however, was performed in

order to obtain a general characterization of nitrogen and phosphorus levels in the soils

from the bay and natural habitat. Porewater in the recently constructed bay was

hypothesized to have lower nutrient concentrations than the surrounding seagrass beds

due to its recent exposure and lack of biomass. The results showed no significant

differences in TDP levels between the bay and natural habitat, but significant differences

did occur in TDKN. The relatively small sample number (n=14) could have contributed

to the statistical differences, as well as seasonal fluxes in nitrogen pools in the outside

seagrass habitat. Short et al. (1993) noted that nitrogen dynamics for S. fihiforme in the

IRL were directly related to light variations and growing season. Porewater nitrogen

pools appeared to be lower during summer growth periods when plant nutrient uptake

increased (Short et al., 1993). Since porewater samples were taken in August, this could

be a possible explanation for the lower TDKN in the seagrass habitat outside of SL 15

than in the bay. By comparison to the natural habitat, nitrogen availability in the bay










appeared to be significantly higher, thus suggesting less of a limitation for seagrass

growth.

Short et al. (1993b) also determined that the IRL is not phosphorus limited, and that

phosphate concentrations between 0.06 mg/L and 0.87 mg/L would supply enough

phosphorus to support seagrass growth. The measured TDP values in the bay and natural

habitat were in this range (0.6 mg/L in the bay, 0.4 mg/L in the natural habitat outside the

bay).

Transplant Experiment

The general purpose of the transplant experiment was to assess the viability of H.

wrightii within the bay. The results showed that two of the transplant plots in the bay

experienced total mortality, while the three plots outside of SL 15, and one inside the bay

had various levels of survivorship. Because each plot location varied in geography and

elevation, it was difficult to ascertain the cause of mortality. The surviving transplants in

TQ-2 suggested that seagrasses were able to grow in the bay, and the surviving

transplants in the natural habitat suggested that mortality might not have been directly

related to planting technique. It was noted that on extreme low tides, TQ-1 and TQ-3

were completely exposed. During these low tides, observations revealed that mounded

areas in the bay were at higher elevations than the surrounding seagrass beds. Water

height in the outside natural habitat was less than 5 cm at times, but most seagrass blades

remained unexposed to air. Desiccation, therefore, could have been a possible cause of

the 100% loss in TQ-1 and TQ-3. Shoots were still present in TQ-2 after a storm event

which damaged its cage. All shoots, however, had disappeared from TQ-1 which had no

cage damage, suggesting that grazing affects were not the cause of mortality.

Interestingly, the plots which experienced the most shoot loss showed no signs of dead










seagrass remnants, appearing as if the transplants were completely removed. The lack of

senescent seagrass blades could have possibly been the result of scavenging, high energy

flow, or wind events.

The results of the transplant experiment were expected based on lack of

transplanting experience, as well as a statistically small number of samples. Additional

observations on blade length, for example, would have contributed to an understanding of

shoot productivity rather than just viability. A control plot with caging but no transplants

would also have been useful in determining the extent of natural colonization in the bay

and natural habitat. The question of the ability of seagrasses to survive (at least for short

periods) in the bay was answered by the results in TQ-2, and further supported upon the

discovery of seagrass recruits in May, 2006.

Seagrass Recruitment

The main research question of this study asked if the environmental conditions in

the constructed habitat of SL 15 were sufficient for seagrass growth. The approach was

to compare the ecosystem in the bay to the ecosystem in the proximate natural seagrass

beds. The original research question was partially answered by the viability of

transplanted seagrasses and more directly answered by the discovery of natural recruits.

H. vi igthlii, S. fihiforme, H. johnsonii, H. dicipiens, H. englemanii and 7: testudinum

became established in the bay, mostly in areas outside of the region deemed supportive

by the habitat suitability model.

The absence of recruits in the flushing channels demonstrated that colonization was

not by rhizome. Sexual reproduction in H. wrightii and H. johnsonii is either rare, or

non-existent, so their colonization was most likely not by extension of rhizome, but

development of fragments (Phillips, 1960; Eiseman and McMillan, 1980; Jewett-Smith et










al., 1997; Hall et al., 2006). Floating fragments of H. wrightii were frequently observed

in and around SL 15 and previous studies have shown that fragments remain viable for up

to four weeks in the spring (Hall et al., 2006). H. johnsonii also propagates by

fragments, but its viability is on the order of days (Hall et al., 2006).

The similarities in seagrass distribution to macroalgae distribution along an east-

west gradient were apparent. This pattern implies that flow or possibly wind directions,

rather than soil, had more significant effects on vegetative colonization in the bay. A

high percentage of lower elevations (-45 to -60 cm, NAD 88) occur on the west side of

the bay, as well as areas of consistent low flow. The east-west orientation of the bay

might also be allowing fragments to float in from the high energy channel, and become

deposited in the low energy depressional areas. The most southwest flushing channel is

also protected by outcrops of mangroves, thus creating a protected cove.

Habitat Suitability Model

Results from Obj ective I were compiled into a habitat suitability model which

calculated the intersection of areas in the bay that were similar to the natural habitat.

This model predicted 14% of the bay as being supportive for seagrasses. Observations of

benthic colonization, however, showed that seagrass recruitment occurred in more than

14% of the bay. Recruits grew in elevations ranging from -20 cm to -55 cm (NAD 88),

demonstrating that elevation, and therefore light availability was non-prohibitive. It is

likely also that the hydrodynamics in the bay were also non-prohibitive. Although H.

johnsonii is restricted in its geographic range, it grows in a variety of physical

environments, such as high energy sandy channels and deep water "soft mud" (Virnstein

et al., 1997; Heidelbaugh et al., 2000). The thresholds for current velocities in the model

were therefore possibly too narrow. Hydrodynamic conditions in the bay that were









deemed "similar" to the natural habitat included current velocities which were within one

standard deviation of the mean outside velocity, yet currents on the outside of SL 15 were

also highly variable. A wider variation of flow speeds should therefore have been taken

into account in the model.

Because specific elevation ranges for different seagrass species are not known,

elevation was not incorporated into the habitat suitability model, but colonization patterns

in the bay suggested that different species occupied different landscape positions. H.

johnsonii commonly grew in areas of higher elevation (<-20 cm) than H. 11 I igthrii and S.

filifornze. Although lower depth limits are published for seagrasses in the IRL (Gallegos

and Kenworthy, 1996; Steward et al., 2005), upper limits have not been quantified.

Virnstein (1995) noted that H. as Iigthrii is "occasionally exposed at lowest tides" and that

S. filifornze is "rarely in very shallow water (< 15cm)." These comments partially

explained the distribution of recruits in the bay in that S. jilifornze grew in elevations

deeper than -20 cm. H. wrightii, however, had not yet colonized areas which were

observed to be exposed on low tides. The two H. wrightii transplant plots which were

exposed also experienced the highest mortality, thus showing the need to properly

quantify the desiccation tolerance for each species. A reclassification of the DEM might

have contributed an additional input layer to the habitat suitability model as a predictor of

species distribution, but further information on the depth ranges for IRL seagrasses would

be needed.

In summary, because of restricting thresholds, the habitat suitability model

underestimated the area which was considered to have sufficient conditions to support

seagrasses. The successful colonization of SL 15 suggested that species such as H.






70


wrightii, S. jiliforme, and H. johnsonii are resilient to a heterogeneous environment,

which in certain aspects, might vary significantly from proximate areas.


Mound Depression


R2= 0.4786


-20


-30 -40


-50


-60


Figure 4-1. Relationship of bathymetry to OM content. As elevation decreases (depth
increases), OM content increases. The significance level was p=0.009
(a=0.05).


Elevation (cm, NAD 88)






























Elevation (cm, NAD 88)


Figure 4-2. Relationship between elevation and F horizon thickness. As elevation
decreased, F horizon thickness increased. The significance level was p=0.000
(a=0.05).
35

30 +

25 R2 = 0.3851
25+

Silt % 20 *

15-

10 *

5- *


Mound Depressiion
**


R2= 0.69"1


-20


- 30 -40 -50


-6;0


5.0 6.0 7.0 8.0 9.0


10.0 11.0


Current velocity (cmn/s)

Figure 4-3. Relationship between silt % and current velocity. Low current velocities
were related to high silt content, possibly because decreased energy allowed
fine particles to settle. This relationship suggests that hydrodynamics have an
effect on particle size distributions in the bay. The significance level was
p=0.014 (a=0.05)















CHAPTER 5
SUMMARY AND CONCLUSIONS

The quantification of physical parameters such as light, nutrients, currents, and soil

properties at SL 15 was important for understanding the suitability of the constructed bay

for seagrasses. By comparison to the literature and surrounding ecosystem, the light

environment in the bay was deemed sufficient for colonization. Porewater TDKN varied

between the bay and natural habitat, but was possibly a reflection of seasonal fluxes in

seagrass nitrogen pools. Values of TDP were determined to be a non-prohibitive nutrient

in either habitat. Water velocity and direction in the bay varied with tide and location,

usually with fast flows in the flushing channels.

The accumulation of fine particles and organic matter in depressional areas

suggested that flow energy and bathymetry were significant subaqueous soil forming

factors in the bay. The thickness of the F horizon increased with decreasing elevations.

Organic matter content was higher in the F horizon than in the A horizon from the natural

habitat. Soil textures in the bay were spatially variable, but on average, had higher clay

content than soils in the natural habitat. These clay loam textures, when disturbed,

caused considerable clouding in the bay and might impact light availability at times.

Observations of these environmental conditions emphasized how interactions and

feedback cycles can potentially influence an ecosystem.

Although considerable spatial variability occurred in the bay with regard to

hydrodynamics and subaqueous soil properties, this heterogeneity did not appear to

hinder seagrass recruitment. A habitat suitability model, created to show suitable areas









for seagrass growth in SL 15, found that 14% of the bay had hydrodynamic, soil, light,

and nutrient conditions which were similar to the natural habitat. Recent colonization,

however, has appeared to be successful in almost two-thirds of the bay. The abundance

and distribution of recruits in the bay suggest that seagrasses are able to colonize in a

heterogeneous environment.

With increasing coastal development in Florida, anthropogenic influences on

seagrasses will likely lead to increases in mitigation efforts. Although this study focused

on an IRL spoil island, the results could be applied to future management efforts

elsewhere. Because the distribution of seagrasses in the bay appeared to be influenced by

flow patterns and elevation, consideration should be taken for island orientation and

construction. An east-west direction of the bay and flushing channels might provide an

increased supply of fragments and seeds, thus increasing possibilities for seagrass

recruitment. Proper knowledge of extreme tidal cycles and more uniform bathymetry in

the bay might prevent certain areas from becoming exposed to desiccation. Less

variation in elevation could also prevent the accumulation of organic-rich F horizons. It

could be speculated that less organic material would decrease available substrate for

decomposition and therefore decrease the likelihood of sulfide toxicity.

Although this study quantified certain environmental parameters in the bay and

could offer baseline data for future research at SL 15, more long-term monitoring would

contribute to the development of future spoil island mitigation endeavors. Porewater

nutrients were generally characterized by this study, but an outlier of high TDKN and

TDP in the deepest elevation (-60 cm, NAD 88) in the bay indicates that a more thorough

analysis of nutrients in the bay is warranted. Semi-permanent flow sensors in the bay and









natural habitat might also provide more specific information on current velocity

requirements for seagrasses in the IRL. In situ light meters could contribute to the

understanding of how weather events might affect water clarity in the bay. A desiccation

experiment in which different IRL species are exposed for various periods of time in

different soils would also be informative as to the upper depth limit at which different

taxa can survive. Finally, the continual development of subaqueous pedology concepts

and techniques, as well as the geographic expansion of subaqueous soil characterization,

will contribute to the understanding and management of protected coastal environments.















APPENDIX A
SUBAQUEOUS SOIL DESCRIPTIONS


Figure A-1. Soil sampling locations in the bay and natural habitat. Transect number and
core number are labeled. O-1, O-2 and O-3 were cores taken from the natural
habitat. Numbers 1-6 were soils described in the natural habitat (sample
numbers "SG")










Table A-1. Subaqueous soil descriptions from the natural habitat. Coordinates are in State
Plane East (feet, NAD 83).
Location: GPS 1 (X = 875537.4; Y=1144027.65)
Date: August 22, 2005
Personel: Hurt, Ellis, Fischler
Sample IDs: SG1-SG5

Map Unit: Vegetated Flat Undifferentiated Drainage: very poorly drained
Native vegetation: S. filiforme Water level when sampled: above surface
Parent material: sandy and loamy marine sediments Daily low water: exposed at low tide
Physiography landformm): vegetated flat Moisture status: wet, drained to moist
Relief: nearly level Permeability: moderately rapid
Elevation: below MSL Salt or Alkali: none
Slope: <1% Stones: none
Aspect: south and west % Coarse framents: 7
Erosion: none % Clay: 9

Al 0-6 cm; black (N2.5/0) sandy loam; structureless and very fluid, n value more
than 1; common fine and medium live roots; moderately alkaline; abrupt wavy boundary.

A2 6-32 cm; black (5Y 2.5/1) sandy loam; structureless and very fluid, n value more
than 1; common fine and medium live roots; moderately alkaline; clear smooth boundary.

A3 32-42 cm; black (5Y 2.5/1) gravelly loamy sand; weak Eine and medium
subangular structure; friable to very friable, n value less than 0.7; common fine and
medium live and dead roots; 15 % shell fragments; moderately alkaline; clear smooth
boundary.

A4 42-80 cm; greenish black (10Y 2.5/1) loamy sand; weak fine and medium
subangular structure; friable to very friable, n value less than 0.7; common fine and
medium live and dead roots; 5 % shell fragments; moderately alkaline; clear smooth
boundary.

A5 80-140 cm; greenish black (10Y 2.5/1) loamy sand; weak fine and medium
subangular structure; friable to very friable, n value less than 0.7; 5 % shell fragments;
moderately alkaline.

Unable to sample soil below 140 cm; material appeared to be sandy with few shell
fragments and colors similar to material above.











Table A-1 Continued
Location: GPS 2 (X=875958.15; Y=1144009.91)
Date: August 22, 2005
Personel: Hurt, Ellis, Fischler
Sample IDs: SG6-SG9


Map Unit: Vegetated Flat Undifferentiated
Native vegetation: T. testudinum ,S. filiforme
Parent material: sandy and loamy marine sediments
Physiography landformm): vegetated flat
Relief: nearly level
Elevation: below MSL
Slope: <1%
Aspect: south and west
Erosion: none


Drainage: very poorly drained
Water level when sampled: above surface
Daily low water: exposed at low tide
Moisture status: wet, drained to moist
Permeability: moderately rapid
Salt or Alkali: none
Stones: none
% Coarse framents: 3
% Clay: 8


Al 0-9 cm; black (5Y 2.5/1) sandy loam; structureless and very fluid, n value more
than 1; common fine and medium live roots; moderately alkaline; abrupt wavy boundary.

A2 9-24 cm; black (5Y 2.5/1) loamy sand; weak fine and medium subangular
structure; friable to very friable, n value less than 0.7; common fine and medium live and
dead roots; less than 5 % shell fragments; moderately alkaline; clear smooth boundary.

A3 24-62 cm; greenish black (10Y 2.5/1) loamy sand; weak fine and medium
subangular structure; friable to very friable, n value less than 0.7; common fine and
medium live and dead roots; less than 5 % shell fragments; moderately alkaline; clear
smooth boundary.

A4 62-88 cm; black (2.5Y 2.5/1) sand; structureless; loose, n value less than 0.7; 5 %
shell fragments; moderately alkaline.

Unable to sample soil below 88 cm; material appeared to be sandy with few shell
fragments and colors similar to material above.










Table A-1 Continued
Location: GPS 3 (X=876145.7; Y=1143424.46)
Date: August 22, 2005
Personel: Hurt, Ellis, Fischler
Sample ID: SG15-SG19


Map Unit: Vegetated Flat Undifferentiated
Native vegetation: H. wrightii
Parent material: sandy and loamy marine sediments
Physiography landformm): vegetated flat
Relief: nearly level
Elevation: below MSL
Slope: <1%
Aspect: south and west
Erosion: none


Drainage: very poorly drained
Water level when sampled: above surface
Daily low water: exposed at low tide
Moisture status: wet, drained to moist
Permeability: moderately rapid
Salt or Alkali: none
Stones: none
% Coarse framents: 3
% Clay: 10


C 0-2 cm; 80 % gray (5Y 4/1) and 20% black (N 2.5/0) sand; loose, n value less
than 0.7; common fine and medium live and dead roots; moderately alkaline; abrupt
wavy boundary.

Ab1 2-13 cm; black (N 2.5/1) sand; weak Eine and medium subangular structure;
friable to very friable, n value less than 0.7; common fine and medium live and dead
roots; less than 5 % shell fragments; moderately alkaline; abrupt smooth boundary. (this
horizon combined with C for sampling purposes)

Ab2 13-47 cm; black (5Y 2.5/1) sand; weak fine and medium subangular structure;
friable to very friable, n value less than 0.7; common fine and medium live and dead
roots; less than 5 % shell fragments; moderately alkaline; clear smooth boundary.

Ab3 47-59 cm; greenish black (10Y 2.5/1) sand; weak fine and medium subangular
structure; friable to very friable, n value less than 0.7; 5 % shell fragments; moderately
alkaline; clear smooth boundary.

Ab 59-74 cm; greenish black (10Y 2.5/1) loamy sand; weak fine and medium
subangular structure; friable to very friable, n value less than 0.7; common fine and
medium live and dead roots; less than 5 % shell fragments; moderately alkaline.

Unable to sample soil below 74 cm; no clue as to the properties of the material










Table A-1 Continued
Location: GPS 4 (X=875730.06; Y=1142942.93)
Date: August 22, 2005
Personel: Hurt, Ellis, Fischler
Sample ID: SG26-SG28


Map Unit: Vegetated Flat Undifferentiated
Native vegetation: S. filiforme, H. wrightii (sparse)
Parent material: sandy and loamy marine sediments
Physiography landformm): vegetated flat
Relief: nearly level
Elevation: below MSL
Slope: <1%
Aspect: south and west
Erosion: none


Drainage: very poorly drained
Water level when sampled: above surface
Daily low water: exposed at low tide
Moisture status: wet, drained to moist
Permeability: moderately rapid
Salt or Alkali: none
Stones: none
% Coarse framents: 3
% Clay: 5


Al 0-10 cm; black (N 2.5/1) loamy sand; structurless; loose; very fluid, n value more
than 1.0; common fine and medium live and dead roots; less than 5 % shell fragments;
moderately alkaline; abrupt smooth boundary.

A2 10-37 cm; greenish black (10Y 2.5/1) loamy sand; weak fine and medium
subangular structure; friable to very friable, n value less than 0.7; common fine and
medium live and dead roots; less than 5 % shell fragments; moderately alkaline; clear
smooth boundary.

A3 37-61 cm; very dark gray (5Y 3/1) sand; weak fine and medium subangular
structure; friable to very friable, n value less than 0.7; less than 5 % shell fragments;
moderately alkaline.

Unable to sample soil below 61 cm; material appeared to be sandy with few shell
fragments and colors similar to A3 horixon.

A thin (less than a few mm) dark gray (5Y 4/1) sand C horizon covers the Al horizon in
most of the pedon; not sampled.










Table A-1 Continued
Location: GPS 5 (X=874853.15; Y=1143951.62)
Date: August 22, 2005
Personel: Hurt, Ellis, Fischler
Sample ID: SG10-SG14


Map Unit: Vegetated Flat Undifferentiated
Native vegetation: sand bar with sparse H. wrightii
Parent material: sandy and loamy marine sediments
Physiography landformm): vegetated flat
Relief: nearly level
Elevation: below MSL
Slope: <1%
Aspect: south and west
Erosion: none


Drainage: very poorly drained
Water level when sampled: above surface
Daily low water: exposed at low tide
Moisture status: wet, drained to moist
Permeability: moderately rapid
Salt or Alkali: none
Stones: none
% Coarse framents: 3
% Clay: 9


C 0-6 cm; 80% olive gray (5Y 4/2) and 20% black (N2.5/0) sand; structureless;
loose, n value less than 0.7; no roots; moderately alkaline; abrupt wavy boundary.

Ab1 6-8 cm; black (N2.5/0) sand; weak fine and medium subangular structure; friable
to very friable, n value less than 0.7; common fine and medium live and dead roots; less
than 5 % shell fragments; moderately alkaline; abrupt wavy boundary. (this horizon was
not sampled)

Ab2 8-28 cm; 50% very dark gray (5Y 3/1) and 50% dark gray (5Y 4/1) sand; weak
fine and medium subangular structure; friable to very friable, n value less than 0.7;
common fine and medium live and dead roots; less than 5 % shell fragments; moderately
alkaline; clear smooth boundary.

Ab3 28-50 cm; very dark gray (5Y 3/1) greenish black (10Y 2.5/1) sand; weak fine
and medium subangular structure; friable to very friable, n value less than 0.7; less than
5 % shell fragments; moderately alkaline; clear smooth boundary.

Ab 50-68 cm; greenish black (10Y 2.5/1) sandy loam; weak fine and medium
subangular structure; friable to very friable, n value less than 0.7; common fine and
medium live and dead roots; less than 5 % shell fragments; moderately alkaline.

Unable to sample soil below 68 cm; no clue as to the properties of the material










Table A-1 Continued
Location: GPS 6 (X=874911.44; Y=1143378.84)
Date: August 22, 2005
Personel: Hurt, Ellis, Fischler
Sample ID: SG20-SG25

Map Unit: Vegetated Flat Undifferentiated Drainage: very poorly drained
Native vegetation: H. johnsonii Water level when sampled: above surface
Parent material: sandy and loamv marine sediments Daily low water: exposed at low tide
Physiography landformm): vegetated flat Moisture status: wet, drained to moist
Relief: nearly level Permeability: moderately rapid
Elevation: below MSL Salt or Alkali: none
Slope: <1% Stones: none
Aspect: south and west % Coarse framents: 3
Erosion: none % Clay: 10

C 0-0.5 cm; dark gray (5Y 4/1) sand; structureless; loose, n value less than 0.7; no
roots; moderately alkaline; abrupt wavy boundary. (this horizon combined with Ab 1 for
sampling purposes)

Ab1 0.5-13 cm; black (N 2.5/1) loamy sand; weak fine and medium subangular
structure; friable to very friable, n value less than 0.7; common fine and medium live and
dead roots; less than 5 % shell fragments; moderately alkaline; abrupt smooth boundary.
(this horizon combined with C for sampling purposes)

Ab2 13-44 cm; greenish black (10Y 2.5/1) loamy sand; weak fine and medium
subangular structure; friable to very friable, n value less than 0.7; common fine and
medium live and dead roots; less than 5 % shell fragments; moderately alkaline; clear
smooth boundary.

Ab3 44-66 cm; greenish black (10Y 2.5/1) loamy sand; weak fine and medium
subangular structure; friable to very friable, n value less than 0.7; 5 % shell fragments;
moderately alkaline; clear smooth boundary.

Ab4 66-84 cm; greenish black (10Y 2.5/1) loamy sand; weak fine and medium
subangular structure; friable to very friable, n value less than 0.7; common fine and
medium live and dead roots; less than 5 % shell fragments; moderately alkaline; clear
smooth boundary.

Ab4 84-100 cm; greenish black (10Y 2.5/1) sand; structureless; loose, n value less than
0.7; less than 5 % shell fragments; moderately alkaline. ((no sample of this horizon
combined was obtained)

Unable to sample soil below 100 cm; no clue as to the properties of the material





Table A-2. Soil descriptions from the bay. Coordinates are in State Plane East (feet, NAD 83). Shell % was not recorded for "n/a".
Boundary transitions are diffuse (D), gradual (G) and clear (C) and topography is wavy (W) or smooth (S). Roots are fine


(f) or very fine (vf).
ID X~coord
T1-1 875866.40
T1-1 875866.40
T1-1 875866.40
T1-1 875866.40
T1-2 875867.15
T1-2 875867.15
T1-2 875867.15
T1-2 875867.15
T1-2 875867.15
T1-3 875865.69
T1-3 875865.69
T1-3 875865.69
T1-3 875865.69
T1-4 875868.62
T1-4 875868.62
T1-4 875868.62
T1-4 875868.62
T1-5 875868.81
T1-5 875868.81
T2-1 875810.58
T2-1 875810.58
T2-1 875810.58
T2-1 875810.58
T2-1 875810.58


Y coord
1143441.67
1143441.67
1143441.67
1143441.67
1143430.13
1143430.13
1143430.13
1143430.13
1143430.13
1143419.05
1143419.05
1143419.05
1143419.05
1143402.71
1143402.71
1143402.71
1143402.71
1143395.86
1143395.86
1143426.96
1143426.96
1143426.96
1143426.96
1143426.96


Horizon
A
Cgl
Cg2
Ab
F
A
C
Ab/C
Ab
F
A
C/Ab
Ab/C
F
AC
C
Ab
A
C
A
Cgl
Cg2
Cg3
Ab


Depth (cm)
0-6
6-10.5
10.5-21
21-32
0-2
0-9
9-16
16-32
32-36
0-2
2-5
5-20
20-32
0-4.5
4.5-13
13-23
23-25
0-4.5
4.5-13
0-3
3-13
13-23
23-26
26-36.6


Sample
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24


Color
5Y 3/1
5Y 5/2
2.5Y 5/2
5Y 4/1
5Y 2.5/1
5Y 4/1
5Y 5/2
5Y 3/1
5Y 4/1
5Y 2.5/1
5Y 5/2
5Y 4/1
5Y 5/2
5Y 4/1
5Y 5/1
5Y 5/2
5Y 4/2
5Y 5/1
5Y 5/1
5Y 4/1
5Y 5/1
5Y 5/1
5Y 5/1
5Y 3/2


Shell %
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
5
15
5
0
2


< 0.7
< 0.7
< 0.7
< 0.7
>>1
< 0.7
< 0.7
< 0.7
< 0.7
>>1
>>1
< 0.7
< 0.7
>> 1
0.7-1
< 0.7
< 0.7
< 0.7
< 0.7
0.7-1
< 0.7
< 0.7
< 0.7
< 0.7


CW none
CW none
GW none
few vf
GW none
CS none
GW none
DW none
few vf
CW none
CW none
none
none
DS none
DS none
none
none
none
none
GW none
CW none
CS none
CS none
few vf


"F" stands for flock horizon. "ID" is the transect number (T1) and core number (-1).


n-value Boundary Roots


I


I


I


I


I











































T4-1 875609.70 1143217.50 A 0-3 46 5Y 4/1 5 0.7-1 GW none
T4-1 875609.70 1143217.50 Cg 3-14 47 5Y 4/1 40 <0.7 CW none
T4-1 875609.70 1143217.50 Ab 14-22 48 5Y 3/1 1 <0.7 common f


Table A-2 Continued
ID X coord


Y~coord Horizon Depth (cm) Sample


Color Shell % n-value Boundary Roots


T2-2
T2-2
T2-2
T2-3
T2-3
T2-3
T2-3
T2-3
T3-1
T3-1
T3-1
T3-1
T3-2
T3-2
T3-2
T3-2
T3-3
T3-3
T3-4
T3-4
T3-4


875805.86
875805.86
875805.86
875798.03
875798.03
875798.03
875798.03
875798.03
875760.96
875760.96
875760.96
875760.96
875742.45
875742.45
875742.45
875742.45
875723.60
875723.60
875744.40
875744.40
875744.40


1143432.41
1143432.41
1143432.41
1143438.13
1143438.13
1143438.13
1143438.13
1143438.13
1143323.93
1143323.93
1143323.93
1143323.93
1143315.56
1143315.56
1143315.56
1143315.56
1143305.64
1143305.64
1143289.79
1143289.79
1143289.79


F
Cg
Ab
F
A/Cg
Cgl
Cg2
Ab
A
Cgl
Cg2
Ab
F
Cgl
Cg2
Ab
Cg/A
Cg
A
Cg
Ab


0-3
3-11
11-24
0-1
1-5
5-11
11-14
14-36
0-2
2-22
22-30.5
30.5-46
0-5
5-9
9-10
10-36
0-3
3-16
0-4
4-8
8-32


5Y 4/1
5Y 5/1
5Y 2.5/1
5Y 4/1
5Y 3/1
5Y 5/1
5Y 5/2
5Y 4/1
5Y 3/1
5Y 5/1
5Y 5/2
5Y 3/1
5Y 2.5/1
5Y 5/2
5Y 5/2
5Y 3/1
5Y 4/1
5Y 5/1
5Y 4/1
5Y 5/1
5Y 3/1


>>1
< 0.7
< 0.7
>>1
.7-1
< 0.7
< 0.7
< 0.7
< 0.7
< 0.7
< 0.7
< 0.7
>>1
< 0.7
< 0.7
< 0.7
0.7-1
< 0.7
>>1
< 0.7
< 0.7


CW none
CW none
few vf
GW none
GW none
CW none
CS none
few vf
GW none
GW none
CS none
few vf
CW none
GS none
CS none
few vf
GW none
none
DW none
CW none
few vf


40


41
42


I





T6-1 875308.08 1143224.93 F 0-2 68 5Y 2.5/1 0 >>1 GW few f
T6-1 875308.08 1143224.93 Cg/A 2-8 69 5Y 4/1 40 <0.7 CW none
T6-1 875308.08 1143224.93 Cg 8-19 70 5Y 5/2 30 <0.7 CS none
T6-1 875308.08 1143224.93 Ab 19-30.5 71 5Y 3/1 1 <0.7 few f


Table A-2 Continued.


ID Xcoord


Y coord Horizon Depth (cm) Sample


Color Shell % n-value Boundary Roots


T4-2
T4-2
T4-2
T4-2
T4-2
T4-3
T4-3
T4-3
T5-1
T5-1
T5-1
T5-2
T5-2
T5-2
T5-2
T5-2
T5-3
T5-3
T5-3


875616.70
875616.70
875616.70
875616.70
875616.70
875626.63
875626.63
875626.63
875483.19
875483.19
875483.19
875507.27
875507.27
875507.27
875507.27
875507.27
875524.92
875524.92
875524.92


1143248.82
1143248.82
1143248.82
1143248.82
1143248.82
1143275.34
1143275.34
1143275.34
1143219.23
1143219.23
1143219.23
1143193.19
1143193.19
1143193.19
1143193.19
1143193.19
1143170.29
1143170.29
1143170.29


F
Cg/A
Cgl
Cg2
Ab
F
CgA
Ab
F
Cg
Ab
F
Cgl
Cg2
Ab1
Ab2
F
Cg
Ab


0-1
1-18
18-32
32-35
35-59
0-3
3-12
12-27
0-3
3-12
12-34
0-3
3-8
8-9.5
9.5-32
32-45.5
0-3
3-11
11-38


5Y 2.5/1
5Y 4/1
5Y 5/1
5Y 5/1
5Y 3/1
5Y 2.5/1
5Y 4/1
5Y 3/1
5Y 3/1
5Y 5/1
5Y 3/1
5Y 2.5/1
5Y 5/1
5Y 5/1
5Y 3/1
5Y 5/1
5Y 3/1
5Y 5/1
5Y 4/1


>>1
<0.7
<0.7
<0.7
<0.7
>>1
<0.7
<0.7
>>1
<0.7
<0.7
>>1
<0.7
0.7-1
<0.7
<0.7
>>1
<0.7
<0.7


DW none
GW none
GW none
CS none
few vf
GW none
CW none
few vf
GW none
GW none
few vf
GW none
CS none
CS none
CW few f
none
GW none
GW few f
few vf


_ _



































Y coord
1142958.71
1142958.71
1142958.71
1142852.57
1142852.57
1142852.57
1143037.86
1143037.86
1143037.86


Horizon
Al
A2
A3
Al
A2
A3
F
Al
A2


Depth (cm) Sample


Color Shell % n-value Boundary Roots


0-15
15-35
35-50
0-10
10-30
30-41
0-5
5-15
15-38


5Y 2.5/1
5Y 4/1
5Y 3/1
5Y 2.5/1
5Y 3/1
5Y 4/1
5Y 2.5/1
5Y 3/1
5Y 3/1


0.7-1
<0.7
<0.7
>>1
<.7
<0.7
>>1
0.7-1
<0.7


GW
DW


few f
few f
few f
few f
few vf
few f
none
none
few vf


GW
DW


_ _


Table A-3. Soil descriptions from the natural habitat.


I


GW
DW


Table A-2 Continued


ID Xcoord


Y coord Horizon Depth (cm) Sample


Color Shell % n-value Boundary Roots


T6-2
T6-2
T6-2
T6-2
T6-3
T6-3
T6-3
T6-4
T6-4
T6-4


875289.38
875289.38
875289.38
875289.38
875271.03
875271.03
875271.03
875326.67
875326.67
875326.67


1143212.32
1143212.32
1143212.32
1143212.32
1143204.74
1143204.74
1143204.74
1143235.69
1143235.69
1143235.69


0-2
2-5
5-14
14-46
0-3
3-9
9-43
0-6
6-16
16-46


5Y 5/1
5Y 3/1
5Y 5/2
5Y 3/1
5Y 4/1
5Y 5/2
5Y 3/1
5Y 2.5/1
5Y 4/1
5Y 3/1


>>1
0.7-1
<0.7
<0.7
<0.7
<0.7
<0.7
>>1
<0.7
<0.7


GW none
GW none
CW none
few f
GW few f
CS none
few f
GW none
CW none
none


ID
O-1
O-1
O-1
O-2
O-2
O-2
O-3
O-3
O-3


X coord
875366.54
875366.54
875366.54
875572.52
875572.52
875572.52
875870.26
875870.26
875870.26













-20


IN


-100






O

I Irl IL~I~T1-5
> I T1-4

w T1-2 T1-3



0 5 10 15 20

Distance along transect (m)

Figure A-1. Soils taken from transect 1 on the east side of the bay. The light brown color
in the A and F horizons in T1-1 and T1-2 are oxidized surface layers.












-20


-30


-40


-50


c?
E
O
r
O


(L)
LLI


T2-2

T2-3


tu


--------------------1-- 0 0 m


Distance along transect (m)


Figure A-2. Transect 2. The Cg2 and Cg3 horizons were found intermittently throughout
the bay and were clay loam or silty clay textures.


T2-1










-30


-40


-50







I T_3-1 T3-4
I T3-2


L ) I..I-- .

tN


0 610 "17

Distance along transect (m)

Figure A-3. Transect 3. The light colored patch in the Ab horizon in T3-1 is a pocket of
air and thus shows lighter-colored oxidized soils.




Full Text

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OBSERVATIONS AND CHARACTERIZATION OF SUBAQUEOUS SOILS AND SEAGRASSES IN A RECENTLY CONSTRUCTED HABITAT IN THE INDIAN RIVER LAGOON, FLORIDA By KELLY C. FISCHLER A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2006

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Copyright 2006 By Kelly C. Fischler

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To my family: Ira, Diane, Scott and Matt, and the many friends who have helped me immeasurably.

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iv ACKNOWLEDGMENTS This thesis is the result of the dedica tion of many family members, teachers, and friends during the past 25 years. I say years, because I was fortunate enough to have been raised by true scholars who taught me the importance of education and hard work. Through their enthusiasm for learni ng about the past and natural world, my parents have given me the inva luable gift of curiosity. My mother, Diane (known for her arsenal of red pens) taught me to write, and to be a strong, independent woman. She also lent her editing skills to much of this thes is. My father, Ira, thr ough his awe of the world around him, taught me to love science and to ap preciate the little things in life. As a UF professor, he has been a valuable resource. A few sentences ar e not enough to thank them for their love, support, finances, and meals brought to me in the lab. I also must thank my brothers, Scott and Matt, for maki ng sure that I grew up to be someone who enjoyed playing in the dirt ra ther than with dolls. I have always looked up to them. I would also like to thank my committee fo r their support. Many thanks go to my advisor, Dr. Mary Collins, whose undergradu ate class was the reason I pursued a degree in soils. Her enthusiasm for soils and leadership among colleagues has been inspiring. As the president of a national society, she is a role model for women in soil science. Wade Hurt is one of a kind and is a wealth of knowledge that I feel privileged to access. His generosity and concern for his students always show, whether th rough field help or the snacks he provides during class. Many ag ree that his hydric so ils test is demanding, but I believe this challenge derives from his high expectations for students and a desire

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v for them to understand. I thank Dr. Tom Frazer for encouraging me to think critically and showing me the importance of a scien tific approach. When contemplating an experimental design, or ponderi ng what certain numbers re ally mean, I have often thought, What would Tom ask? Although I don t have a beard to scratch while I wax intellectual, I hope one day to thi nk like Tom. Lastly, I offer a lifetime of thanks to Dr. Rex Ellis. For the past 3 years he con tinually offered me chances to grow and learn. Even the small lessons, such as driving his boat, were appreciated. Rex is known for his selflessness when it comes to helping others and he repeatedly sacrificed time from his own work and family to help me in the field and office. He often claims to over-think things, but it is really a si gn of a true scientist. This project was a collaboration, and would not have been possible without him. I thank him for being my mentor and my friend. Additional thanks go to Tom Saunders and Chip Chilton for their field help, bad jokes, and always giving me an excuse to take a break. Genaro Keehn was an immense asset and through his lab and field work, helped me get this project done. Caitlin Hicks and Natalie Balcer were great colleagues and always willing to listen. Todd Osborne was especially helpful in the clutch when I n eeded data. Stephanie Keller was also helpful during lab analyses. Numerous others have been around to see me through, and I could not have made it this far without their love and support. Travis, Betsy, Sarah, Melissa, Paul, Emily, David, Doug, and Jim are my da ily inspirations a nd I thank them for everything.

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vi TABLE OF CONTENTS page ACKNOWLEDGMENTS.................................................................................................iv LIST OF TABLES...........................................................................................................viii ABSTRACT.......................................................................................................................xi CHAPTER 1 INTRODUCTION........................................................................................................1 Objectives.....................................................................................................................2 Seagrass Growth Dynamics..........................................................................................3 Light Availability..................................................................................................3 Hydrodynamics......................................................................................................4 Nutrient Cycling....................................................................................................5 Subaqueous Soils...................................................................................................6 Seagrass Transplant Experiment.................................................................................10 Study Site Description................................................................................................10 Spoil Islands........................................................................................................12 The SL 15 Design Concept..................................................................................12 2 METHODS.................................................................................................................15 Objective 1: Quantification of Environmental Parameters.........................................15 Light....................................................................................................................15 Chlorophyll..........................................................................................................15 Currents...............................................................................................................16 Nutrients..............................................................................................................16 Soils/landscape....................................................................................................17 Benthic Observations...........................................................................................19 Objective 2: Transplant Experiment...........................................................................19 Objective 3: Habitat Suitability Model.......................................................................20 3 RESULTS...................................................................................................................25 Objective 1: Environmental Conditions.....................................................................25 Light Availability................................................................................................25 Currents...............................................................................................................26

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vii Nutrients..............................................................................................................27 Digital Elevation Model......................................................................................27 Subaqueous Soils.................................................................................................28 Benthic Observations...........................................................................................33 Objective 2: Transplant Experiment...........................................................................34 Objective 3: Habitat Suitability Model.......................................................................35 4 DISCUSSION.............................................................................................................54 Soil/Landscape Analysis.............................................................................................54 Bathymetry..........................................................................................................55 Flow Regime.......................................................................................................56 Parent Material....................................................................................................56 Climate................................................................................................................57 Organisms............................................................................................................58 Time.....................................................................................................................58 Catastrophic Events.............................................................................................59 Water Column Attributes....................................................................................60 Subaqueous Soil Survey.............................................................................................60 Light Availability........................................................................................................62 Hydrodynamics...........................................................................................................63 Nutrients.....................................................................................................................65 Transplant Experiment................................................................................................66 Seagrass Recruitment..................................................................................................67 Habitat Suitability Model...........................................................................................68 5 SUMMARY AND CONCLUSIONS.........................................................................72 APPENDIX A SUBAQUEOUS SOIL DESCRIPTIONS..................................................................75 B SUBAQUEOUS SOIL DATA...................................................................................92 C HYDRODYNAMIC DATA.......................................................................................97 D LIGHT AND NUTRIENT DATA............................................................................102 E TRANSPLANT DATA............................................................................................105 LIST OF REFERENCES.................................................................................................108 BIOGRAPHICAL SKETCH...........................................................................................116

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viii LIST OF TABLES Table page 3-1 Chlorophyll a values from each transplant quadrat.................................................36 3-2 Average subaqueous soil properties from the bay and natural habitat at SL 15......43 3-3 Average soil properties from 0-10 cm in each landscape unit.................................45 3-4 Total number of shoot counts pe r transplant quadrat over time...............................51 B-1 Soil descriptions from the bay..................................................................................82 B-2 Soil descriptions from the natural habitat................................................................85 B-1 Subaqueous soil data from th e natural (outside) habitat..........................................92 B-2 Subaqueous soil data from the bay...........................................................................93 C-1 Current direction (Dir .) and velocity (V).................................................................97 D-1 Light attenuation coefficients (Kd) for the natural and bay habitats......................103 D-2 Total dissolved Kjeldalh nitrogen (TDKN) and total dissolved phosphorus (TDP) from 0-5 cm porewater samples..................................................................104

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ix LIST OF FIGURES Figure page 1-1 Study site location in Ft. Pierce, Florida..................................................................13 1-2 Transformation of SL15...........................................................................................14 2-1 Light meter apparatus...............................................................................................21 2-2 Soil porextractor.......................................................................................................22 2-3 Bathymetric sampling locations...............................................................................23 2-4 Soil sampling locations in the bay and natural habitat.............................................24 2-5 Transplant quadrats location and construction.........................................................24 3-1 Average Kd values in the natural a nd constructed bay habitat.................................36 3-2 Average water velocities on both outgoing and incoming tides..............................37 3-3 Current flow velocity and direction in the bay.........................................................38 3-4 Classified maps of curre nt velocities in the bay.......................................................39 3-5 Digital elevation model of the bay...........................................................................40 3-6 Representative subaqueous soils take n from the natural outside habitat and inside the construc ted bay habitat............................................................................41 3-7 Soils from representati ve transect 6 from the bay...................................................42 3-8 Settling characteristics of soils from the bay and the outside habitat.....................44 3-9 Characteristics of the Ab horizon from the bay......................................................45 3-10 Digital elevation model show ing delineations of landscape units..........................46 3-11 Classified landscape units.......................................................................................47 3-12 Percent cover map of Gracilaria sp in March, 2006..............................................48

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x 3-13 Seagrass distribution in th e bay as of September, 2006...........................................49 3-14 Seagrass abundance in the bay per m2.....................................................................50 3-15 Halodule johnsonii recruits in the bay.....................................................................51 3-16 Epiphytes and macroalgae at SL 15.........................................................................52 3-17 Habitat suitability model showing th e areas in the bay which had current and soil properties similar to those in the natural habitat outside of SL 15....................53 4-1 Relationship of bathymetry to OM content..............................................................70 4-2 Relationship between elev ation and F horizon thickness.........................................71 4-3 Relationship between silt % and current velocity....................................................71 A-1 Soil sampling locations in the bay and natural habitat.............................................75 A-1 Soils taken from transect 1 on the east side of the bay............................................86 A-2 Transect 2................................................................................................................ .87 A-3 Transect 3................................................................................................................ .88 A-4 Transect 4................................................................................................................ .89 A-5 Transect 5................................................................................................................ .90 A-6 Transect 6................................................................................................................ .91 D-1 Sampling locations for light attenuation (Kd).......................................................102 D-2 Sampling locations for porewater nutri ents in the bay and constructed habitats..104 E-1 Halodule wrightii shoot counts in each transplant quadrat....................................105

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xi Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science FACTORS AFFECTING SEAGRASS GROWTH IN A CONSTRUCTED HABITAT IN INDIAN RIVER LAGOON, FLORIDA By Kelly C. Fischler December 2006 Chair: Mary E. Collins Major Department: Soil and Water Science Anthropogenic impacts to seagrasses in the Indian River Lagoon (IRL), Florida have led to a new method for mitigation in which spoil island SL 15 (St. Lucie County) was scraped down to create a 1.7 ha submerged bay habitat. To asse ss the suitability of this created habitat for seagrass growth, light availability, nutrie nt content, hydrodynamic and subaqueous soil conditions in the bay were compared to conditions in the surrounding natural seagrass beds. There were no significant differences in average light attenuation (Kd) coefficients in the bay and natural habitat (0.54 m-1 and 0.55 m-1, respectively). All underwater irradiance valu es were above the minimum requirement for seagrass growth in the IRL. Porewater nutr ients at SL 15 were determined by analyzing total dissolved Kjeldahl nitr ogen (TDKN) and total dissolved phosphorus (TDP). Results showed no significant differences in TDP valu es in the two habitats, but TDKN values were slightly higher in the bay (2.53 mg L-1) than in the natural system (1.27 mg L-1). Water velocities in the bay were mapped on incoming and outgoing tides to better

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xii understand hydrodynamic conditions and circ ulation patterns. Although average velocities in the bay and natural habitat on both tides were not si gnificantly different, more spatial variability o ccurred in the bay. Soil and landscape relationships in the ba y were examined by creating a fine-scale soil survey and digital elevation model. The recently exposed bottom within the bay consisted of four soils: a coar se carbonate spoil material (Cg1), a fine-textured mangrove clay (Cg2), an accreted flocculent layer (F horizon), and a buried seagrass A (Ab) horizon. Surface soil properties correlated with elevation. Subaqueous soils in the natural habitat were characterized by homogenous da rk colors and were dominantly sandy loams in texture. More variability appeared with regard to texture and organic matter content in the bay than in the natural habitat. A transplant experiment was also co nducted to assess the viability of Halodule wrigthii in the bay. Six plots were planted in May 2006 and monitored monthly for shoot counts. One plot in the bay maintained tran splant viability, sugges ting the suitability of the bay for colonization. This hypothesis was supported by the discove ry of four species of seagrasses growing in the ba y. Seagrass recruitment in th e bay appeared to follow an east-west gradient, with higher concentra tions of shoots in the west. Although the environmental conditions in the bay appeared more heterogeneous than in the natural habitat, successful seagrass recruitment sugge sted that the design of SL 15 was sufficient for colonization.

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1 CHAPTER 1 INTRODUCTION Seagrasses are marine angiosperms that acc ount for as much as 12% of net oceanic carbon production (Duarte and Chiscano, 1999; Hemminga and Duarte, 2000). In addition, seagrass beds perform a variety of eco logical functions. They stabilize soils, promote the deposition of partic les that leads to increased wa ter clarity, and also serve as important refuge and foraging habitats for a large number of fish es and invertebrates (Dawes, 1981; Larkum et al., 1989; Stevenson et al., 1993; Virnstei n and Morris, 1996; Nagelkerken et al., 2000). Seven species of seagrasses occur in the Indian River Lagoon (IRL): Halodule wrightii Ascherson Syringodium filiforme Kutz Thalassia testudinum Banks ex Knig, Ruppia maritima L. Halophila dicipiens Ostenfeld Halophila englemanii Aschers and the threatened species, Halophila johnsonii Eisemen (Dawes et al., 1995). Collectively, these grasses form the most crucial habitat in the lagoons ecology (Steward et al., 1994). In recent decades, however, environmenta l and anthropogenic stresses in the IRL have led to an 11% decrease in total s eagrass acreage and a 50% decrease in their maximum depth of occurrence (Fletcher and Fletcher, 1995). Research on the IRL provided information on environmental conditions needed for seagrass growth such as light and nutrients, as well as methods for ma pping the distribution and health of species (Dawes et al., 1995; Fletcher and Flet cher, 1995; Virnstein, 1995; Gallegos and Kenworthy, 1996; Morris et al., 2000; Virnst ein and Morris, 2000). No studies, however, have examined seagrass growth in the IRL in the context of a restored habitat.

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2 In the spring of 2005, a mitigation project in Ft. Pierce, Florida, provided an opportunity to observe seagrass es in a constructed environm ent. The transformation of spoil island SL 15 (St. Lucie County) into a potential habitat for seagrasses offered a unique chance to examine how different ecologi cal parameters might interact and affect future seagrass colonization. Prior resear ch established the importance of light availability, hydrodynamics, and nutrient cy cling to seagrass health (Fonseca and Kenworthy, 1987; Kemp et al., 1988; Duarte 1991; Olesen and Sand-Jensen, 1993; Koch, 2001). Subaqueous soil has also been cite d as affecting seagrass geochemistry and landscape attributes (Carlson et al., 1994; Demas et al., 1996; Demas, 1998; Demas and Rabenhorst, 1999; Borum et al., 2005; Holmer et al., 2005; Bradley and Stolt, 2006; Ellis, 2006). Observing and characterizing these di fferent ecological parameters was therefore important for understanding th e potential ability for seag rass colonization in SL 15. Objectives Specific requirements for light, hydrodynamics, nutrients, and subaqueous soil characteristics may vary significantly by lo cation and species. In the IRL, light requirements for seagrasses have been published (Gallegos and Kenworthy, 1996), but threshold values for current velocities or soil organic matter, for example, have not been determined. Thus, one approach for answeri ng the question is the constructed habitat of SL 15 sufficient for seagrass growth? is to compare its subtidal environment within SL 15 to that of the proximate seagrass beds. Accordingly, three objectives were formed: Objective 1: Quantify and describe the envir onmental factors which might act upon seagrasses in SL 15. Objective 2: Conduct a seagrass transplant experiment in the natural and constructed habitat. Objective 3: Synthesize the data into a habitat suitability model.

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3 Objective 1 addressed the specific paramete rs previously determined to affect seagrass growth, including light attenuation, current velo city, nutrient content, and subaqueous soil conditions. The purpose of Objective 2 was to test whether or not seagrass transplants would survive in SL 15. Finally, the environmental data was combined to estimate the area within the c onstructed habitat in SL 15 which would be supportive of seagrass colonization. Seagrass Growth Dynamics Since the publication of Seagrasses of the World by C. Kees den Hartog in 1970, numerous experimental a nd observational studies on th e biology and ecology of seagrasses have increased our understanding of submerged aquatic vegetation (Larkum et al., 2006). As a result, certain environmenta l parameters have become established as vital factors affecting seagrass. Light Availability The vast majority of rese arch on seagrasses has involve d the direct or indirect effects of light on their biophysical ecology. As with terrestrial angiosperms, seagrasses require a minimum amount of photosynthetica lly active radiation (PAR; 350 or 400 to 700 nm) to produce and survive (Hemminga and Duarte, 2000; Zimmerman, 2006). Most species require 10 to 37% of in-water surface irradiance (Duarte, 1991; Olesen and Sand-Jensen 1993; Kenworthy and Fonseca, 1996). In the IRL, Halodule wrightii and Syringodium filiforme require approximately 24 to 37% of surface irradiance to maintain net productivity (Gallegos and Kenworthy, 1996; Kenworthy and Fonseca, 1996). The intensity and duration of li ght vary with season and location, as do the metabolic requirements for each species (Hemminga and Duarte, 2000).

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4 Light reduction experiments have shown various negative responses in seagrass growth and morphology. Decreased light can impact shoot density, blade length, biomass, and chlorophyll content (Neverauskus, 1988; West, 1990; Williams and Dennison, 1990). Seagrass physiology is a ffected by light reduction because oxygen produced from photosynthesis in the leaves diffuses to the rhizosphere and allows seagrasses to grow in anaerobic sediments. If light availability and photosynthesis rates are high, then seagrasses can maintain a larg er supply of oxygen to the roots and prevent phytotoxic sulfide intrusion. Several studies correlated shorter a nd less intense light periods with lower photosynthesis rates and incr eased sulfide toxicity (Goodman et al., 1995; Holmer and Bondgaard, 2001; Pederson et al., 2004; Holmer et al., 2005). Manipulating light levels in an experimental setting is informative since one of the leading causes of seagrass loss is increased light attenuation due to water quality decline (Kemp et al., 1988; Short and Wyllie-Echeverri a, 1996; Tomasko et al., 1996). Light is attenuated rapidly in even clear water and is further attenuated when dissolved organic particles are present (He mminga and Duarte, 2000). A common method for reporting how much light is abso rbed with depth is Kd, or the downwelling atte nuation coefficient. Based on the literature, Kd and chlorophyll a were chosen as vari ables to describe the light environment at SL 15. Hydrodynamics Current flows in seagrass beds have been shown to affect leaf nutrient uptake, organic matter transport, pollination, sediment characteristics, light conditions, biomass, and production (Schumacher and Whitford, 1965; Madsen and Sondergaard, 1983; Fonseca and Kenworthy, 1987; Koch et al., 2006). Elevated current speeds coincide with morphological adaptations, such as greater root mass (Short et al., 1985). Faster

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5 velocities also contribute to in creased nutrient uptake through the thinni ng of the diffuse boundary layer that surrounds leaf blades (Koch, 1994; Massel, 1999; Cornelisen and Thomas, 2002). Although increased flows can limit the growth of light-reducing epiphytes on seagrass blades, epiphytes mi ght also serve to roughen the boundary layer and become beneficial (Boston et al., 1989). Seagrass canopies attenuate current velo city (Fonseca et al., 1982; Fonseca and Fisher, 1986; Gambi et al., 1990) and reduce phys ical stress on the plants, but decreased flows can increase sediment anoxia and allo w for more organic matter accretion (Robblee et al., 1991). Low-flow conditi ons, therefore, can result in increased porew ater sulfide (Barko et al., 1991; Koch, 1999). Koch (2001) summarized mi nimum and maximum threshold values for different seagrass speci es, only one of which was a subtropical species. Thalassia testudinum was reported to require a minimum velocity of 5 cm/s for growth and occurrence (Koch, 1994). The time of exposure to different water velocities was not reported and the requirements for H. wrightii and S. filiforme are not yet known. Nutrient Cycling Although seagrasses are highly pr oductive (up to 800 g carbon m2/yr; Hauxwell et al., 2001), they typically grow in nutrient-poor waters (Short, 1987; Hemminga and Duarte, 2000). Because of phosphates tenden cy to bind with carbonates (Kitano et al., 1978), it is a potentially limiting nutrient in tropical seagrass beds (Short, 1987; Hemminga and Duarte, 2000). Nitrogen is also commonly limited in marine systems (Short, 1987; Hauxwell et al., 2001; Fourqurean and Zieman, 2002). Short et al. (1993) noted that in the IRL, nitr ogen is the limiting nutrient for S. filiforme growth. The ability of seagrasses to grow in oligotrophic waters suggests that they obtain most of their nutrients (via roots) from the soil, whic h typically has higher concentrations of

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6 ammonium, phosphate, and nitr ate than the overlaying wa ter column (Short, 1987; Hemminga, 1997; Hemminga and Duarte 2000; Romero et al., 2006). While experiments have shown that nutrie nt enrichment increases leaf and root biomass (Udy and Dennison, 1997), excess nutrien t loading in coastal systems has caused as much as 50% of worldwide seagrass loss (Short and Wyllie-Echeverria, 1996). Nutrient-limited algae bloom in response to elevated nutrients causing eutrophication and increases in light-attenuating phytoplan kton, epiphytes and macroalgae (Cambridge and McComb, 1984; Silberstein et al., 1986; Ke mp et al., 1988; Tomasko et al., 1996; Ralph et al., 2006). Increased organic matter to the system also adds substrate for microbial decomposition and thus increases th e danger for sulfide toxicity (Terrados et al., 1999). Between 1940 and 1991, nitrogen input s from waste water doubled in Tampa Bay, Florida, resulting in as much as 72% loss of seagrasses by 1982 (Haddad, 1989; Lewis et al., 1991; Zarbok et al., 1994). Chlorophyll concentrations were positively correlated with nitrogen levels, thus showi ng the relationship betw een nutrient additions and phytoplankton production (Johansson, 1991) Although the seagrass loss in Tampa Bay was more significant than that observ ed in the IRL during the past few decades, similar increases in nutrient loading have occurred. As a consequence, nutrients are a primary concern of water resource managers working in the IRL. Subaqueous Soils Although many studies have investigated relationships between seagrasses and their environment, few have focused on the ecological functi on of the substrates they occupy. Of the studies that specifically addressed estuar ine sediments, most involved anecdotal observations and were based main ly upon geologic or geochemical principles (Demas et al., 2001). In the mid-1990s, however efforts in Maryland demonstrated that

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7 certain sediments could be included in th e realm of soil scien ce (Demas et al., 1996; Demas, 1998; Demas and Rabenhorst, 1999). Researchers observed that sediments under shallow waters (less than 2.5 m) can experience soil-for ming factors, such as those described by Jenny (1941). These factor s include additions from biogenic CaCO3 and marine humus (Valiela, 1984) bioturbation by infaunal organisms, and chemical transformations through the oxi dation and reduction of S a nd Fe (Demas, 1998; Bradley and Stolt, 2003). These investigations spear headed the inclusion of subaqueous soils within the defined concept of soil by the USDA-National Resource Conservations Service in 1999 (Demas, 1998; Demas and Ra benhorst, 1999; Bradley and Stolt, 2003). This broadened view of aquatic bottoms was si gnificant in that it enabled the inclusion of submerged aquatic vegetation, such as seagra sses, in a pedological paradigm. Demas (1999) demonstrated that similar to terrestria l soils, subaqueous soils form as a function of their landscape. Their vegetation cover, elevation position, and even parent material can create distinct horizons which elucidate previous environments and processes. By studying these horizons in a pedological context, a suite of characte rization analyses can be performed and used to classify the so il under taxonomic mapping units (Bradley and Stolt, 2003). Research in the coastal marsh estuarie s of Rhode Island and Maryland, along with the near-shore grass flats on the west coast of Florida, has demonstrated significant relationships between seagrasses and soil characteristics, such as color, percent organic matter, salinity, and texture (Demas, 1999; Bradley and Stolt, 2006; Ellis, 2006). Subaqueous soils within established beds are typically finer in texture than those in unvegetated soils (Scoffin 1970; Koch, 2001; Ellis, 2006). Coarse sandy soils might

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8 improve O2 diffusion, but they inhibit rhizome el ongation and have less fertility, while fine-textured soils might contribute to elev ated sulfide levels (Thayer et al., 1994; Fonseca et al., 1998; Koch, 2001; Bradley and St olt, 2006). The ability of seagrasses to attenuate currents and trap part iculate organic matter contribu tes to dark soil colors and fine textures, yet most vegetated subaqueous soils have less than 5% organic matter (Koch, 2001). Higher percentages of organic ma tter occur, however, but it is unknown if maximum thresholds exist. Mesocosm experiments have provided some indication as to whether seagrasses prefer one type of soil to another. Kenworthy and Fonseca (1977) transplanted Z. marina from sand, sand-silt, and silt in to each of the three soils. Results showed the highest productivity occurred with silt-originating plan ts and those which were planted into a silt soil. The specific percentages of sand and si lt in each soil were not identified, however, leaving the term sand-silt as a vague description. Another mesocosm experiment examined Ruppia maritima growing on different sizes of glass beads to represent sand and determined that fine and medium sandsize particles resulted in maximum growth (Koch, 2001). The use of glass beads avoided the effects of nutrien t uptake. It would therefore be of interest to unde rstand the interactions that infl uence nutrient availability in silty versus sandy soils. In a mitigation project similar to SL 15, subaqueous soils might have influenced seagrass survival. Three spoil islands were scraped down in Laguna Madre, Texas, each with different soil characte ristics (Montagne, 1993). H. wrightii survived in two of the island areas, one with 90% sand, 2% silt, and 3% clay, and the other with 88% sand (Montagne, 1993). All plants died at the third site, however, which had 63% sand and

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9 31% clay (Montagne, 1993). This latter obs ervation suggested that a more detailed characterization of the subaqueous soils at SL 15 was important. In traditional soil sc ience, the most common method fo r mapping the distribution of soils is through the cr eation of a soil survey. A soil survey describes the characteristics of the soils in a given area, classifies the soils according to a standard system of classification, plots the boundaries of the soils on a map, and makes predictions a bout the behavior of soils. The different uses of the soils and how the response of manageme nt affects them are considered (Soil Survey Staff, 1993) When creating these maps, observations of landscape (slope, drainage) and vegetation (crops, native plants ) are made in order to genera te a conceptual model of soil formation in the survey area. These attributes, along with physical properties (texture, horizons) and chemical propert ies (mineralogy, base satura tion), allow pedologists to define boundaries between soils and to group them into taxonomic units. Previous attempts at subaqueous soil mapping involved th e classification of soils into landscape units, which were based upon bathymetry, land-surface shape, location, water depth, and depositional environment (Demas and Ra benhorst, 1999; Bradley and Stolt, 2003). Although terrestrial soil science uses soil map units as the term for areas with a dominant kind of soil, these landscape un its also had shared properties which were labeled with traditional taxonomic classes, as defined by Soil Taxonomy (Soil Survey Staff, 1975). Ellis (2006) created a subaqueous soil survey on the west coast of Florida, which also delineated a seagrass-supporti ng habitat into taxonomic units based upon vegetation, landscape, and geographi c location with respect to land. Because the goal of this study was to asse ss the suitability of SL 15 for seagrass growth, a subaqueous soil surv ey was created as a method for describing its physical environment using established terminology and guidelines. This soil survey also

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10 provided a means of comparison between the natural and construc ted habitats. By delineating the inside of SL 15 into soil (or landscape) units whic h had similar physical and chemical properties, the si milarities, or differences from soils in the natural habitat would be more clearly defined. Seagrass Transplant Experiment Seagrass restoration and mitigation are currently multimillion dollar industries in Florida and could continue gr owing with increased coastal development (R. Lewis, pers. comm.). Since the 1970s, different methods have resulted in nu merous successes and large-scale failures (Stein, 1984). By 1998, an official set of gui delines and decision keys were established for restoration in the United States (Fonseca et al., 1998). Although planting remains somewhat haphazard in success rates, technical improvements continue to be made, such as the addition of cages for graz ing prevention (Hauxwell et al., 2004). Success criteria for SL 15 are defined as 10% seagrass cover within the first 5 years (R. Lewis, pers. comm.) is not achieved by natu ral recruitment in the first five years, then H. wrightii will be planted. For this study, a sm all-scale transplantation experiment sought to test the viability of such plantings and supplement the findings of Objective 1. With three plots inside SL 15 and three pl ots outside in the surrounding seagrass beds0, transplant results could also possibly indicate how differe nces in soil type might influence future growth. Study Site Description The IRL is a shallow, barrier island lagoon which stretches 250 km along the Atlantic coast of Florida (Figure 1-1). It has an average depth of 1.7 m and an average width of 3 km (Smith, 2001). The IRL formed in the last 6,000 years when coastal retreat

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11 and sea level rise stabilized (Davis et al., 1992). Although the confining Hawthorne Formation is thinnest or absent along the east coast of Florida, the four surficial aquifers that border the IRL contribute only 1% to 5% of interstitial water, s uggesting that most of the IRL consists of recycled seawater (S warzenski et al., 2000). Other controls on salinity include precipitation, wind, tidal forcing, evaporation, and surface runoff (Swarenski et al., 2000). Micr otidal exchange occu rs through four inle ts in the southern part of the lagoon: Sebastian, Ft Pierce, St. Lucie, and Jupi ter. The study site location for this project is located within 3 km of th e Ft. Pierce Inlet, which transports more than 50% of the intertidal volume of the lagoon (Smith, 2001). The IRL is considered to be one of the mo st diverse estuaries in the United States (Gilmore et al., 1983). Species richness in th e IRL has been attributed to its location which straddles both tropical and subtropical regimes (Dawes et al., 1995). During the past 50 years, however, development has in creased urban and ag ricultural runoff and subsequently decreased water quality (Steward et al., 1994; Fletcher and Fletcher, 1995; National Estuary Program, 1996; Sigua et al ., 1999). Such changes could possibly shift the IRL from a macrophyte-dominant to an alga l-dominant system (Steward et al., 1994). After seagrass loss increased to 70% in some areas, the St. Johns River Water Management District implemented a networ k of water quality monitoring sites and permanent seagrass transects (Morris et al., 2000; Virnstei n and Morris, 2000). The percent coverage along most of these trans ects actually increased from 1994 to 1998, but was highly variable (Morris et al., 2000). Th e current estimate of seagrass coverage for the IRL is 30,000 ha (Morris and Virnstein, 2004 ). The database for water quality and

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12 seagrass coverage in the IRL is extensive a nd growing, yet with mitigation projects such as that at SL 15, more localized monitoring is needed. Spoil Islands Spoil islands in the Indian River Lagoon were created in the 1950s when the Army Corps of Engineers dredged the Intracoastal Waterway for navigation. Spoil material from the bottom of the channel was deposit ed in piles, thus creating 137 islands throughout the lagoon. Of these 137 islands, 124 are owned by the state and managed by the Florida Department of Environmental Pr otection (FDEP). Although the spoil islands contain a diversity of organisms and frequen tly act as a native bird habitat, many are inhabited by exotic vegetation, including Schinus terebinthefolius (Brazilian pepper) and Casuarinas equisetifolia (Australian pine). The transfor mation of a spoil island into an intertidal and subtidal flat, therefore, had the dual benefit of removing exotics and creating a potential habitat for native ve getation (e.g. seagrasses and mangroves). The SL 15 Design Concept After seagrasses were damaged during br idge construction in Jensen Beach, Florida, the Florida Department of Trans portation was required to mitigate for lost vegetation. Spoil island SL 15 (27o 28' 40" North, 80o 19' 23" West; Figure 1-1) was chosen because of its sufficient size (4.1 ha), lack of recrea tional use, and proximity to a spoil basin (R. Lewis, pers. comm.). In March 2005, the excavation of SL 15 began with the removal of all vegetation except the outer 1.24 ha of mangroves ( Rhizophora mangle, Avicennia germinans, and Conocarpus erectus ). A trellis was built on the west side of the island on which a conveyor belt transporte d material off the island to a barge. Seven flushing channels were cut through the mangrov es on the southern ha lf of the island to allow for tidal exchange and colonization of seagrasses from the surrounding flats (Figure

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13 1-2). The completed inner submerged bay measures 1.37 ha and was excavated to a mean depth of 1.5m NGVD. Coccoloba uvifera L. (sea grape) and C. erectus were planted on the 0.54 ha of upland maritime hammoc k. The remaining interior of the island (2.16 ha) was scraped to 1.0 m NGVD and planted with R. mangle propagules and Spartina alterniflora along the bank edges. Figure 1-1. Study site location in Ft. Pierce, Florida. A) Location of Ft. Pierce in the Indian River Lagoon. B) Spoil island SL 15 (27o 28' 40" North, 80o 19' 23" West), located north of the A1A bridge in Ft. Pierce. A B

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14 Figure 1-2. Transformation of SL 15. Aerial photos taken in (A) June 2004, (B) May, 2005, (C) November, 2005, and (D) December, 2005. The yellow polygons show each constructed zone, including the seagrass, mangrove and upland habitats. 100 m

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15 CHAPTER 2 METHODS Objective 1: Quantification of Environmental Parameters Light Light attenuation coefficients (Kd) were quantified by taking in situ measurements of surface and underwater Photosynt hetic Photon Flux Density (PPFD, mol s-1 m-1). A cosine-corrected LI-COR 192SA underwater light sensor (2 ) on a mounting frame was attached to a polyvinyl chloride (PVC) pipe (Figure 2-1). Measurements were recorded at bottom depth and at a mid-de pth point in the water column, usually at 10 cm or 20 cm below the surface. Surface PPFD was taken simultaneously with a LI-COR 190 light sensor. Four paired at-depth and surface readings were recorded by a LI-COR 1400 datalogger and then averaged at each site. Seven sites were sampled within the bay and nine outside the ba y (Appendix D). Kd was calculated using B eers Law (Equation 2-1), where Iz = Ioekz (2-1) z=depth (m), and I= irradiance values ( mol s-1 m-1) at z depth (Iz) and at the surface (Io). Solving for Kd, Kd= -ln(Iz/Io)/z (2-2) Chlorophyll Chlorophyll a concentration served as an es timate of phytoplankton biomass and contributed to an understanding of the light environment at SL 15. Six surface water samples and replicates were collected from each transplant quad and filtered in the field.

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16 A Nalgene vacuum hand pump was used to fi lter 500 ml of water through a Whatman GF/F glass fiber filter (Str ickland and Parsons, 1968; Fr azer et al., 2001;). Pigment extraction used 90% heated ethanol, and corrections for pheophytin were made by acidifying the sample with 0.2 N HCl (Sar tory and Grobbelaar, 1984). Samples were analyzed at the Department of Fisheries a nd Aquatic Sciences, University of Florida. Currents Current velocities at SL 15 were meas ured throughout the bay at times of incoming (n=154) and outgoing (n=168) tidal flow to better understand circulation patterns and flow magnitudes in the seagrass zone. To captu re events within a similar tide range, observations were made within a one hour time period. Three teams were equipped with a Trimble or Garmin Global Positioning System (GPS). Bright Dyes Fluorescent water tracing dye was used to observe current direction and speed. The direction was quantified using a meterstick and compass while speed was calculated using a stopwatch. Nutrients For the purpose of this study, porewater wa s analyzed in order to characterize the nutrient environment at SL 15. Fourteen porew ater samples from the inside (n=8) and outside (n=6) of SL 15 were collected on August 23, 2006, us ing a porextractor (Figure 2-2, Nayar et al., 2006). The design of the apparatus enabled an integrated extraction from 1 to 5 cm below the soil surfac e. Samples were drawn through a 0.45 m filter, acidified with 36 N2SO4, and kept refrigerated until analyzed. Total dissolved phosphorus (TDP) and total Kjelda hl nitrogen (TKN) were KSO4 digested and analyzed using an autoclave colorimetric autoanalyzer at the Wetlands Biogeochemistry Lab in the Soil and Water Science Department at th e University of Florida (EPA 351.2).

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17 Soils/landscape In terrestrial soil science, a priori knowledge of landforms in the survey area is obtained from aerial photos and field observa tions. In a subaqueous environment, however, these landforms are hidden underwat er. At SL 15, bathymetric data were collected and converted into a digital eleva tion model (DEM) in or der to visualize the microtopography that resulted from the construction process. Bathymetry for the inside of SL 15 were collected, using a meter stick to measure water depth and a Trimble Pathfinder Pro Series GPS to record position (Figure 2-3). To correct for tidal fluctuations, water leve l was simultaneously r ecorded by an In-situ miniTroll submersible data logger in the mi ddle of the bay. Corrections for tide were made by relating changes in the water level to the recorded depth. The top of the well containing the data logger was surveyed in to a benchmark on the island, thus enabling the conversion of water depths to an absolute elevation (NAD 88). The elevation data set was interpolated using an ordinary kriggi ng with a lag size chosen to minimize RMS error. The digital elevation model (DEM) was created by converting the interpolation into a grid using a cell size of 1 m. After examining the DEM, aerial photos, and vegetation/elevation patterns in the natural habitat, soil sampling locations in the bay were chosen to represent areas in differing landscape positions (Figure 2-4). Twenty-three acry lic push cores (inner diameter = 6 cm) deployed along six transect s were taken within the island. Three additional cores were taken from the southern side of SL 15 in the surrounding seagrass. Munsell soil color, shell content, hand texture, horizon desi gnation, n-value, depth, and root occurrence were recorded. The soil cores were described and sampled in the lab. Representative subaqueous soils were coll ected from the seagrasses surrounding SL 15

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18 (Figure 2-4). Locations were chosen to captu re a diversity of seagrass species covers. Six soils were described w ith the following cover: S. filiforme, S. filiforme and T. Testudinum, H. wrightii, T. testudinum and H. johnsonii, and H. wrightii and S. filiforme Munsell soil color, shell content, texture, horizon, n-value, depth, and root occurrence were recorded in situ Although soil surveys traditionally examine so ils to a depth of 2 m, the cores in the bay were deployed to maximum depths between 40 cm and 60 cm. Two-meter observations are important on land because of agricultural or construction limitations, for example. Because SL 15 was designed specifically for seagrass mitigation, however, this study focused on the upper (>50 cm) portion of the soil which would most likely be influential in the seagrass rooting zone. Fo r laboratory analysis, subaqueous soils from the natural and constructed habitat were sa mpled by horizon, but an integrated analysis on the 0 to 10 cm range was also performed to represent soil characteristics in the rooting zone of H. wrightii and Halophila species (Zieman and Zieman, 1989). The A horizons from the natural habitat were greater than 10 cm and therefore analyzed as described. For the soils from the constructed habitat in which the top horizon was less than 10 cm, composite OM content and part icle-size distribution were calculated using a weighted average based on thicknesses. A soil with an A horizon from 0 to 3 cm, and an Cg horizon from 3 to 10 cm, for example, were analyzed by horizon, but the A horizon was assigned a weight of 0.3 and the Cg horizon a weight of 0.7. Organic matter content was calculated by loss on ignition in a 550o C muffle furnace for four hours (Heiri et al., 2001). Particle-size distribu tion was determined by the pipette method (Gee and Bauder,

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19 1965). Carbonate content was determined on a subset of samples by acidification with 20 mL 2M HCl (Kennedy et al., 2005). Benthic Observations Estimates of algae and seagrass coverage in the bay were made throughout the study. In March 2006, the extent and distribution of Gracilaria sp (drift algae) in the bay were visually estimated in north-sout h transects and inter polated (Figure 3-12A) The percent cover for Gracilaria sp was recorded in 5 m2 areas. In September 2006, seagrasses growing in the bay were mapped along east-west transects. Because seagrass shoots were often spaced farther than 1 m apar t, visual estimates of percent cover were not sensitive enough to capture spatial patterns in seagrasses. Instead, the number of shoots in a 2 m radius around the observer was us ed to capture the sparse, but frequently occurring, seagrasses. Shoot counts, percen t cover where applicable, and species were recorded along east-west tran sects (Figure 3-13A). Objective 2: Transplant Experiment Six 1.5 x 1.5 m transplant plots were constr ucted in May 2006. Three plots within the bay and three on the southern side of SL 15 were established (Figure 2-4a). Transplant quadrats TQ-2, TQ-3, and TQ-6 were planted on May 11, and TQ-1, TQ-4, and TQ-5 were planted on May 26, 2006. Tran splant quadrats TQ-1 and TQ-3 were located on mounds, and TQ-2 was located at a lower elevation. Previously determined Kd demonstrated that there was sufficient light for seagrass growth at each site, therefore minimizing light availability as a factor. Transplant quadrats TQ-4, TQ-5, and TQ-6, were situated based on surrounding seagra ss cover. Sites were located where H. wrightii was the dominant species, where existing se agrass appeared undisturbed, and where unvegetated bottom was available for planting. H. wrigthii was selected as the species to

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20 transplant because of its availability as wrack around SL 15 and its previous success in bare-root planting efforts (Fonseca et al., 1998). The plots were constructed using four stee l rebar posts (2 cm diameter) at each corner, which were then covered with a PVC pi pe to enhance visual identification (Figure 2-5b). H. wrightii fragments with more than six s hoots were collected and stored in seawater for less than on e hour until planting. After gently pushing the roots approximately 1 to 2 cm into the soil, the fragments were anchor ed by a bamboo-skewer according to Davis and Short (1997). Nine fragments were planted in each plot and spaced 0.5 m apart. A 1-inch chicken-wi re cage was wrapped around each plot to prevent grazing (Figure 2-5b) Shoot counts were recorded on May 11, May 26, July 10, August 8, and September 8, 2006. Fouled cag es were cleaned following each count. Objective 3: Habitat Suitability Model When comparing the natural and constructed habitat at SL 15, st atistical analyses were used to assess any significant differe nces between the two environments. To illustrate any spatial relationships and vari ability that might appear in the data, geostatistical analyses were used to create ma p layers that would show differences in the constructed and natural habitat at SL 15. Cu rrent velocities were interpolated using a first order, local polynomial interpolation (75% local). The inter polation was converted to a raster grid using a cell size of 1 m. For each grid cell, the mean current velocity from outside SL 15 was subtracted from the in terpolated value, resulting in a map which showed spatial distributions of deviation from the mean outside value. This calculation was then classified to differentiate areas which were one, two, or three standard deviations above and one, two, or three standa rd deviations below from the mean outside value.

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21 A similar technique was used to map and compare differences in subaqueous soil properties. Landscape units were visually delineated on the DEM, thus grouping areas of similar soil properties. These properties were classified as be ing significantly different or similar to soils in the natural habitat. The habitat suitability model essentially combined these map layers, showing the intersection of areas where light availability, soil properties, nutrients and current velocities were comparable to the seagrass beds outside of SL 15. Light sensorMounting frame Figure 2-1. Light meter apparatus. A 2 LI-COR 192SA underwater light sensor attached to a mounting frame and PVC pipe.

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22 Figure 2-2. Soil porextractor (Nayar et al., 2006). The unit is pushed into the soil to the desired depth. A parafilm membrane w ithin the PVC is pierced, breaking a vacuum and allowing porewa ter to enter the pipe.

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23 Figure 2-3. Bathymetric sampling locations. Wate r depth was recorded at each point with a meter stick. Position was recorded with a Trimble GPS. Depths were corrected for tidal fluctu ations by referencing a submersed datalogger, which was simultaneously recording changes in water height.

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24 Figure 2-4. Soil sampling locations in the bay an d natural habitat. The numbers next to the yellow dots show the transect and core number. These locations were chosen to represent different landfor ms in the bay based upon the aerial photograph (above) and the di gital elevation model. O-1 O-3 were cores taken from the outside seagrasses (green ). The pink dots around the outside of SL 15 were soils from different seagra ss species cover (samples SG-1, etc. Appendix A). Figure 2-5. Transplant quadrats location a nd construction. A) Loca tion of transplant quadrats B) Picture of TQ-3 with PVC/rebar posts and 1 caging.

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25 CHAPTER 3 RESULTS Objective 1: Environmental Conditions Light Availability Light extinction coefficients (Kd) and chlorophyll concentrations were measured to characterize the light environment affecting seagrasses in the constructed and natural habitats at SL 15. Chlorophyll a (Chl a ) concentration was analyzed as an indicator for the amount of phytoplankton in th e water column. Corrected Chl a refers to samples which were acidified to remove phaeophyti n, a degradation product which can interfere with measurements. The average corrected Chl a content was 2.12 0.20 g L-1 within the bay (n=3) and 2.20 0.28 gL-1 (n=3) outside of SL 15 (Table 3-1). Uncorrected values (including phaeophytin) were 2.91 0.22 g L-1 in the bay and 2.97 0.31 g L-1 outside of SL 15. A Kruskal-Wallis test ( =0.05) showed no signi ficant differences in corrected Chl a concentration in the ba y and natural habitat. The Kd values with the bay ranged from 0.17 m-1 to 0.75 m-1 (n=13) and from 0.35 m-1 to 0.74 m-1 (n=11) on the outside of SL 15. The average Kd for the inside bay was 0.54 ( 0.18), and the outside Kd was 0.55 (.12). The average Kd values calculated from the bay and the outside natural habitat showed no significant di fferences within the two environments (Figure 3-1). Irradiance values on the bottom (ca. 10 cm above soil surface) ranged from 850 to 1964 umol s-1 m-1 and varied with depth and time of day.

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26 Currents An understanding of the hydrodynamic conditions (velocities, flow vectors) in the bay and natural habitat was integral when considering how flow patterns might affect seagrass colonization and bed maintenance. The mean current velocities in the bay and outside of SL 15 were statistic ally compared, but more deta iled maps of flow vectors were also created to assess circulation patterns caused by the flushing channels and bottom topography. Average flow velocities reve aled no significant differences between the area inside the bay and the outside area supporting seagrasses (Figure 3-2). The average velocity for the outside was 11 5 cm s-1 on the incoming tide and 9 4 cm s-1 on the outgoing tide. The average velocity for the bay was 10 7 cm s-1 on the incoming tide and 11 9 cm s-1 on the outgoing tide. Although the averaged veloci ties showed no significant differences in the two habitats, the velocities in the bay varied sp atially on incoming and outgoing tides. Also, spatial patterns of flow were different for incoming and outgoing tides. Circulation vectors in the bay on the incoming tide showed patterns of flow or iginating from the southeast and exiting the bay to the northw est into the channel (Figure 3-3a). The opposite direction of flow occurred on the out going tide, with water moving from the channel, back through the bay, and to the inle t in the southeast (Figure 3-3b). Flow vectors outside of SL 15 appeared more consis tent in direction, either toward or away from nearby channels. To visually compare the velocities of the bay to the mean velocity in the natural habitat, the flow maps from both tides were cl assified into three categories: faster than, slower than, and similar to the natural habita t mean. Faster velocities were those which

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27 were between 1 and 2 sd away from the mean. Slower velocities we re those between -1 and -2 sd below the mean, and similar velociti es were those which we re within +/1 sd. The classification of the current flow maps re vealed that on the incoming tide, 13% of the bay had velocities slower than the outside m ean velocity, 1% of th e bay was faster and 86% of the bay was similar (4a). A classifi cation of the outgoing tide showed that 40% of the bay had slower velocities, 6% was faster, and 53% had velocities which were similar to the outside habitat (Figure 3-4b). Nutrients Based on a Kruskal-Wallis test, porewater samples from 0 to 5 cm revealed significant differences in TDKN between the bay and outside habitat (df=1, p=0.024, =0.05). The average TDKN content for the bay was 2.535 1.007 mg L-1 and the average TDKN for the outside of SL 15 was 1.267 0.573 mg L-1. The median TDKN for the bay was 2.72 mg L-1 and 1.148 mg L-1 for the natural habitat. No significant difference appeared in the averages for TDP values between the bay and outside habitat (df=1, p=0.519, =0.05). The average TDP in the bay was 0.602 0.872 mg L-1 and the average TDP in the outside was 0.401 0.403 mg L-1. The median TDP value in the bay was 0.177 mg L-1 and 0.335 mg L-1 in the natural habitat. Digital Elevation Model The model that best fit the elevation data was generated by ordinary krigging. This interpolation method was used because it pr oduced a model with relative smoothness (i.e. outliers carried less weight) a nd it had the lowest root-meansquare (6.445). A search neighborhood of 9.4 m was used, meaning th at elevations at unknown points were calculated by considering the el evation values within a radius of 9.4 m. A lag size of

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28 2.2 m was chosen, which grouped el evation points into bins ba sed on their distance apart (in intervals of 2.2 m) from each other. Th e lag size and search neighborhood thresholds were selected based on their ability to produ ce a precise DEM in the bay. Because over 900 elevation points were collected, the DEM showed a fine-resolution image of the bottom topography in the bay (Figure 3-5). Th e lowest elevation was -61 cm (North American Datum 1988; NAD 88) and the highest was +24 cm (NAD 88). The average elevation according to the mode l was -43 11 cm (NAD 88). Subaqueous Soils The subaqueous soils within the bay app eared to be more heterogeneous with regard to particle-size di stribution, OM content and co lor than the soils from the surrounding seagrass beds (Figure 3-6). A t ypical bay soil consisted of a black (5Y 2.5/1) flocculant (flock) layer, a dark gray (5Y 4/1) A hor izon, one to three olive gray (5Y 5/2) Cg horizons, and a very dark gray buried A horizon (Ab; 5Y 3/1). Flock layers lack a specific horizon designation by th e USDA-Natural Resources Conservation Service. For this study, they are thus refe rred to as F horizons. The subaqueous soils from vegetated areas in surrounding natural ha bitat were described as having multiple A horizons with an underlying Cg horizon. Th e A1 horizons were typically black (5Y 2.5/1), and the A horizons beneath were either dark gray (5Y 4/ 1) or very dark gray (5Y 3/1). Thickness of F horizon correlated with topog raphy. Lower elevations appeared to collect fine materials and accrete a thicker F horizon (Figure 3-7; Appendices A and B). Higher elevations had thin or absent F horizons and had coarse spoil material (Cg) as the surface soil. Mixing of color and texture was common among the Cg and Ab horizon. A

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29 clay loam layer was also inte rspersed among the Cg (5Y 5/1 or 5Y 5/2) horizon in six of the cores. Statistical analyses were performed to identify significant differences in soil properties in the bay and natural habitats (Kruskal-Wallis, =0.05; df=1). There was no significant difference in organi c matter (OM) content between the natural and constructed habitats within the 0 to 10 cm depth range (p=0.386, H=0.75; Table 3-2). The F horizon in the bay, however, had significantly higher le vels of OM than the A horizon in the soils from the natural habitat (p=0.000, H=12.57). Percent carbonates varied by horizon, and were significantly higher in the bay soils compar ed to the soils from the natural habitat. Particle-size distribution anal ysis revealed significant diffe rences in the soils from the bay compared to the soils from the out side natural habitat (Table 3-2). The A (p=0.008), F (p=0.014) and Cg2 (p=0.008) horizons from the bay had significantly higher amounts of silt than the A horizon from the na tural habitat. The F (p=0.000) and Cg2 (p=0.008) horizons also had si gnificantly higher amounts of cl ay than the A horizon from the natural habitat. There was greater variati on in particle-size dist ributions for the bay than in the natural habitat. The dominant te xtures of soil in the surrounding seagrasses were sandy loams, loamy sands and sands. Te xtures in the bay included clay loam, sandy clay loam, sandy loam, loamy sand and sand. The high amounts of clay (up to 35%) in th e bay soils was also reflected in field observations. Walking in the bay appeared to significantly cloud the water with particles that remained suspended for up to an hour. This effect was not not iced in the natural habitat. As an experiment, a handful of Cg horizon from the bay and A horizon from the natural habitat were simultaneously dropped in to the water and allowed to settle. The

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30 settling time of the Cg2 horizon was much great er than for the outside A horizon (Figure 3-8). The long (>2 minutes) settling time of cl ay particles in the bay can be explained by Stokes Law which states that settling veloci ties are a function of particle diameter. Additional comparisons of soil properties were made in order to address the hypothesis of the Ab horizons in the bay be ing relict A horizons from a seagrass bed. The chemical and physical properties of the Ab and A horizon from the natural habitat were tested for significant differences. Based on Kruskal-Wallis ( =0.05), no significant differences existed between the Ab horizons and A horizons with re gard to percent sand (p=0.254, df=1), but there was a significant difference in OM content (p=0.039, df=1). Similar colors (5Y 3/1 and 5Y 2.5/1), as well as the presence of dead roots in the Ab horizon (Appendix A) also supported the hypothesi s prior of seagrasses occurrence in the area which SL 15 was created (Figure 3-9). At SL 15, a subaqueous soil survey (1: 1,200) was created in order to map the distribution of soils in the ba y using methods similar to terr estrial soil surveys and to facilitate a comparison of soil properties in th e nearby natural habitat. Ellis (2006) listed the steps for creating a soil survey: 1. Observe patterns in vegetation and landf orms using aerial photography, digital elevation models, and field observations. 2. Observe patterns in soil properties via field observations, as related to the vegetation and landform patterns. 3. Superimpose patterns of soils, vegeta tion, and landscape on the local geology to develop a conceptual soil/landscape model. 4. Describe and define the soil map units. 5. Create a physical representation of the con ceptual soil/landscape model by spatially delineating aerial photography into units that represent the various landforms and associated soils map units.

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31 Step 1 was carried out through the creation of a fine-scale DEM and an analysis of recent aerial photography (see Chapter 2). Observations in the field (Steps 2 and 3) confirmed relationships between landscape position (elevation) and soils. Deeper elevations (-38 to -60 cm, NAD 88) were asso ciated with thicker F horizons than soils which were located on mounds (-10 to -33 cm). Using these elevation thresholds, the DEM was classified into three landscape uni ts: mounds, flats, and depressions (Steps 4 and 5; Figure 3-10). The areas with eleva tions between -33 and -38 cm (NAD 88) were labeled as flats. Mounds and depressions which were smaller than approximately 50 m2 were not delineated. The flats landscap e unit therefore included microtopographic features such as small mounds and depressions. The remaining steps of a soil survey include refining the model and populating each map/landscape unit with a soil identifier or the taxonomic classification, as defined by Soil Taxonomy (Soil Survey Staff, 1999; Ellis, 2006). In the United States, taxonomic classification is based mainly on th e kind and character of soil properties and the arrangement of horizons w ithin the profile (Wettstein et al., 1987). Based on these criteria, the soils from the natural habitat were classified as loamy, siliceous, hyperthermic Typic Endoaquolls (Soil Survey Staff, 2003). Soils in the bay were also classified as loamy, siliceous, Typic E ndoaquolls (Soil Survey Staff, 2003). Although soils in the bay and natural habi tats were taxonomically identical, the bay soils (0 to 10cm) had signi ficantly different pr operties from soils (0 to 10cm) in the natural habitat (Table 3-3). Because the purpos e of this soil survey was to map soils in the context of suitability for seagrasses, thes e differences were considered when refining the conceptual and spatial model of soils in the bay. The landscape units were referred to

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32 by their non-taxonomic term (depression, flat, mound) to convey that differences exist and might potentially affect seagrass growth. In a terrestrial system, the arrangement of horizons is important because of water table fluctuations, or limitations with agricu lture and development. For the subaqueous soils in the bay, however, an emphasis was pl aced on the 0 to 10 cm range because it is the rooting zone for seagrass species likel y to colonize the bay (Zieman and Zieman, 1989; Creed, 1997). Also, the arra ngement of horizons in the bay was fairly consistent throughout in that an F horiz on or A horizon was followed by a Cg horizon and then an Ab horizon (Figure 3-7). Each horizons th ickness varied throughout the bay, most likely as a result of the constructions process, but the Ab horizon ap peared in every soil, 8 to 30 cm below the soil surface. In a terrestri al survey, this underlying horizon throughout the area might classify the landscape into one similar map unit. Thus in the context of seagrass growth, a classification based on horizon arrangement below the F horizon would not provide sufficient information. A classification of the soils in the ba y was therefore based upon particle-size distribution and OM content in the 0 to 10 cm range for each landscape unit. These properties for each landscape unit were then comp ared to the soil properties in the natural habitat (Table 3-3). Results showed that the depression landscape unit had particle-size distribution and OM content va lues which were significantly different to values in the natural habitat. Although both the mound a nd flats landscape units had one soil property which was significantly different (OM content and sand %, respectively) to the soils in the natural habitat, the mound landscape unit wa s classified as signifi cantly different and the flats was classified as similar to the nearby environment (Figure 3-11). The

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33 distinguishing factor of the mound landscape unit was that on low tide, certain areas were exposed, suggesting a potential stress or for seagrass recruits. Benthic Observations On two occasions, observations of benthic colonization were made. In the spring of 2006, Gracilaria sp formed a dense mat on the bottom of the bay. Estimates of percent cover in a 5 m2 area were made in transects and interpolated (Fig ure 3-12). The spatial distribution of Gracilaria sp followed an east to west gradient, with higher concentrations on the west side of the bay. Over the summer, mats of the blue-green algae Lyngbya majuscula formed in the outside seagrasses. Acanthophora spicifera, Hypnea sp ., and Caulerpa sertularioides were also observed in both the bay and the natural habitat. In May 2006, the first observation of seag rass colonization in the bay was made. H. wrigthii and S. filiforme appeared to be growing with a concentration on the west part of the bay, similar to the Gracilaria sp. distribution. H. johnsonii was also observed as growing in patches, with higher concentra tions in mounded areas. Single blades of T. testudinum and H. englemanii were also noted. Epiphyt es appeared to cover all seagrasses in the bay. A seagrass survey was performed in September to estimate the number of shoots growing in the bay. Samp ling locations were along transects and the number of shoots counted in a 2-m radius (Figure 3-13a). The dominant species was H. wrightii which comprised approximately 90% of the seagrass recruits, excluding H. johnsonii (Figure 3-13b). The seagrass survey wa s then interpolated (local polynomial, 80%) to show seagrass abundance per squa re meter (Figure 3-14). Because of H. johnsonii s small structure, percent cover was us ed to quantify its extent of growth.

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34 Shallow areas in the west part of the bay had up to 20% cover by H. johnsonii (Figure 313 and Figure 3-15). Objective 2: Transplant Experiment In TQ-1 and TQ-3, 100% mortality occurred. The remaining transplant quads had various levels of survivorship (Table 3-4). TQ-2 lost 14% of its total shoots, TQ-4 lost 45%, and TQ-5 and TQ-6 lost 9% and 34%, respectively. In TQ-2 and TQ-5, shoot counts decreased during the firs t two months, but new shoots grew into the quadrat and led to an approximate increas e of 50% between July and August. The new shoots were determined to be separate recruits from the original transplants because they appeared to be growing through the caging material, into the quadrat. The averaged shoot number loss was 71% in the bay and 29% loss in the natural habitat. During monthly monitoring, the cages were cleaned of fouling. Dried drift algae and dead seagrass fragments comprised most of the trapped material in and around the caging material. Estimates of cage fouling af ter one week revealed that 60% to 90% of the cage mesh was covered in flotsam (Figure 3-16a). Irradiance values were measured in TQ-1 between 10:00 and 11:00 a.m. to qua ntify the amount of light blocked by the cage fouling. Bottom irradiance on the east side of the cage which experienced midmorning shading was 50% of surface irradian ce. The non-shaded west side had an average bottom irradiance of 82% of surface irradiance. In the transplant quads which had some survival, an average of 85% loss occu rred on the east side of the quadrat. On July 26, 2006, it was noted that the cages on TQ -2 and TQ-3 were damaged after a strong wind event. Half of the cage appeared to be intact, but the other half had been lifted over the rebar stakes. TQ-1 remained intact, but the transplants had completely disappeared from TQ-1 and TQ-3. No signs of grazing were present on the blades in TQ-2.

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35 Lyngbya majuscula was the dominant algae in both habitats that covered the cage and seagrass blades. Epiphytic algae also c overed seagrass blades in both the constructed and natural habitat after one day from planting (Figure 3-16b). Callinectes sapidus (blue crabs), Lagodon rhomboides (pinfish) and Sphoeroides maculates (northern puffer) were observed in the outside quads. Objective 3: Habitat Suitability Model A habitat suitability model (HSM) was create d to illustrate the extent of suitable areas for seagrass growth in the bay. Suitabl e, for this study, was defined as similar to conditions in the natural habitat. The HSM was the synthesis and culmination of data gathered from Objective 1 and was generate d by combining the areas in the bay which had current and soil conditions that were simila r to conditions in the natural habitat. For currents, similarity was established as areas with water velocities within 1 standard deviation of the outside mean velocity on both incoming and outgoing tides (Figure 3-4). Soil conditions in the bay were tested for significant differences in OM content and particle-size distribution to soils in the natu ral habitat. The cla ssification of landscape units by these differences provided a map with soil properties which were similar to properties outside of SL 15 (Figure 3-12). The HSM calculated areas in the bay which formed the intersection of three input layers: the classified maps of current velocity (incomi ng and outgoing tide, Figure 3-3, 34) and the classified landscape ma p units (Figure 3-11). Because Kd values in the bay were determined to not be significantly diffe rent from the outside natural habitat, the entire bay was classified as suitable with regard to light availability. Although TDKN values differed in the two habitats, the sm all number and high vari ability of porewater samples (n=14) hindered a spatial interpolati on of the data, thus nutrient conditions were

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36 not included in the HSM. The intersection of the areas which had properties similar to the natural ecosystem comprised 14 % of the bay (Figure 3-17). Table 3-1. Chlorophyll a (Chl a ) values from each transplant quadrat. CorrectedUncorrected LocationHabitat Chl a (g/L)Chl a (g/L) n TQ1Bay2.232.991 TQ2Bay2.233.081 TQ3Bay1.902.671 TQ4Natural2.233.171 TQ5Natural2.463.131 TQ6Natural1.902.621 No significant difference (Kruskal-Wallis test; df=1, =0.05, p-value=0.663) occurred in corrected Chl a values in the bay and natural habitat. 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00Kd(m-1)NaturalBay 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00Kd(m-1)NaturalBay Figure 3-1. Average Kd values in the natural and c onstructed bay habitat. Although Kd values varied with depth and time of day in the natural and constructed bay, there was no significant difference in average Kd values for both habitats (Kruskal-wallis test; df=1, p=0.829, =0.05). Kd (m-1)

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37 Natural Bay 0 5 10 15 20 25Tidal PeriodCurrent Velocity (cm/s)Incoming Tide Outgoing Tide Outside of SL 15 Inside Bay Natural Bay 0 5 10 15 20 25Tidal PeriodCurrent Velocity (cm/s)Incoming Tide Outgoing Tide Outside of SL 15 Inside Bay Figure 3-2. Average water ve locities on both outgoing and incoming tides. Based on a Kruskal-Wallis test, no significant differences ( =0.05) occurred in the bay and natural habitats on the outgoing tide (df=1, p=0.915) and incoming tide (df=1, p=0.280).

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38 Figure 3-3. Current flow ve locity and direction in th e bay. Incoming tide (A) and outgoing tide (B) are shown. Water flows were faster near flushing channels and flow directions followed paths to either the inlet in the southeast, or intercoastal waterway to the northwest. A B

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39 A Figure 3-4. Classified maps of current velo cities in the bay. The incoming tide (A) and outgoing (B) tides are shown. The mean velocity from the natural habitat was subtracted from the original map and then classified into three groups: faster, slower, and similar to the natural habitat. B

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40 Figure 3-5. Digital elevation model of the bay. More than 900 water depths were co llected in the field, corrected for tide, a nd related to surveyed benchmarks on SL 15. Eleva tion values were based on the NAD 88 datum.

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41 Figure 3-6. Representative suba queous soils taken from the natural outside habitat (left, O-1) and inside the constructed bay hab itat (right, T2-3). The soils from the natural habitat had dark, homogenous colors throughout and multiple A horizons. Soils from the bay were ch aracterized by an F horizon, followed by an A or Cg horizon. The F horizon was typically black (5Y 2.5/1), but appears light brown in the image becau se of the oxidized surface. The Cg2 horizon had a clay loam texture. Th e Ab horizon was hypothesized to be a relict A horizon from a pre-existing seagrass bed.

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42 Figure 3-7. Soils from represen tative transect 6 from the bay. As elevation decreased (deeper), an increase in F horizon th ickness appeared. The Cg horizon was spoil material of varying thickness. The Ab horizon usually occurred between 20 to 30 cm below the surface of the soil.

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43 Table 3-2. Average subaqueous soil properties fr om the bay and natural habitat at SL 15. Dominant HorizonColorOM %Sand %Silt %Clay %CaCO3 %Sand Size n F5Y 2.5/16.4 2.655 1225 1720 82.6fine15 A5Y 5/22.9 1.768 2120 2112 62.7fine9 A/Cg5Y 4/13.8 2.172 1410 618 9-fine5 BayCg, Cg15Y 5/12.8 1.277 1812 1611 91.3medium20 Cg25Y 5/26.7 2.638 2527 1335 132.2fine8 Cg/Ab5Y 4/13.3 0.885 56 29 2-very fine3 Ab5Y 3/12.9 0.884 12 7 13 9 30.2very fine18 0-10 cm3.8 1.67213152.7fine A15Y 2.5/13.4 1.081 59 311 20.4very fine6 A210Y 2.5/12.2 0.786 75 39 4-very fine6 NaturalA32.5Y 2.5/11.8 0.589 44 27 3-very fine6 A45Y 3/11.8 0.788 45 1.68 2-very fine6 C 5Y 4/21.5 0.19325-very fine6 0-10 cm5Y 2.5/13.3 0.98569-very fine30 Dashes represent no data available. Organic matter is OM.

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44 Figure 3-8. Settling characteristics of soils fr om the bay and the outside habitat. The higher amounts of clay in the Cg horizon than in the A horizon were evident in the time taken for particles to settle out of the water column. The implications are that if disturbed, soils in the bay might reduce light availability and affect seagrass.

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45 Figure 3-9. Characteristics of the Ab hor izon from the bay. A) The Ab horizon and A horizon from the bay and natural habitat. Color, shell content, particle-size distribution and OM content were not signi ficantly different in both soils. B) Dead seagrass roots in the Ab horizon. Table 3-3. Average soil properties from 0 to 10 cm in each landscape unit. Bolded values are those with p values (in pa renthesis) which we re significantly (Kruskal-Wallis test; =0.05) higher or lower than soil properties from the natural habitat. LandscapeF horizon UnitOrganic MatterSand %Silt %Clay %thickness (cm) Depression 4.52 (0.046)68 (0.006)16 (0.046)16 (0.007) 2.61 Flat3.66 (0.350) 74 (0.032) 10 (0.121) 16 (0.050) 1.57 Mound 2.51 (0.002) 75 (0.083)12 (0.073)12 (0.116)1.00

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46 Figure 3-10. Digital elevation model show ing delineations of landscape units. Three units were created based on elevation: mounds, flats, and depressions. Soil sampling locations (pink dots) were selected to represent soils from the different landscape units. The green ar eas (-10 to +25 cm) were elevations along the shoreline which were exposed at medium and low tide. Soils in the flushing channels were not sampled. 1:1,200

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47 Figure 3-11. Classified landscape units. Th e original depressions and mounds were classified as having soil properties (OM content, text ure) in the 0 to 10 cm range which were significantly different (blue) from soil properties in the natural habitat, while soils in the flat s had similar soil properties (yellow). Classified Landscape Units

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48 Figure 3-12. Percent cover map of Gracilaria sp in March, 2006. Estimates of percent cover per 5m2 were made at each location (A). Numbers next to each point are the percent coverage estimates for macroalgae. High concentrations of macroalgae existed near flushing channels and in the south-west side of the bay (B). A B

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49 B B Figure 3-13. Seagrass distribu tion in the bay as of Sept ember, 2006. A) Shoot counts were made in a 2-m radius around each point (12.6 m2). The pink stars represent areas that had H. johnsonii cover. The numbers next to each star are the percent coverage for H. johnsonii at each point. B) Seagrass distribution in the bay by species present.

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50 Figure 3-14. Seagrass a bundance in the bay per m2. The number of shoots was interpolated (local polynomial, 80%) to show trends in recruit concentration.

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51 Figure 3-15. H. johnsonii recruits in the bay. This patc h represents approximately 25% cover. Table 3-4. Total number of shoot counts per tr ansplant quadrat over time. TQ-1, 4, 5, and 6 have np for May 11, 2006, because they were not yet planted. DateTQ-1TQ-2TQ-3TQ-4TQ-5TQ-6 5/11/2006np7794npnpnp 5/26/200611339371119888 7/10/20060350628367 8/9/20060660618958 % loss1001410045934 LocationBayBayBayOutsideOutsideOutside

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52 Figure 3-16. Epiphytes and macroalg ae at SL 15. A) Cage fouling and Lyngbya majuscula growing on transplant blades. B) Epiphytic algae growing on seagrass blades.

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53 Figure 3-17. Habitat suitability m odel showing the areas in the ba y which had current and soil prop erties similar to those in t he natural habitat outside of SL 15. This model predicted th at 14% of the bay was suitable for seagrass growth.

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54 CHAPTER 4 DISCUSSION The transformation of SL 15 was an experimental approach for seagrass mitigation in the IRL and if successful, its repeatability w ould be of interest to ecosystem managers. Seagrasses in the IRL have been cited as having a value of $30,000 ha/yr (Virnstein and Morris, 1996), showing their importance as the economic foundation of a widely used fishery. Seagrasses in the IRL are also an integral ecologic component in the most diverse estuary in North America. Other than light thresholds and nutrient ranges, however, no specific requirements for seagra ss growth in the IRL are published. The inherent difficulty of dissociating and controlling an ecosystem for analysis means that while relationships can be demonstrated, de claring specific require ments for a habitat remains challenging. The approach for this study, therefore, was to compare the conditions in the constructed habitat with th e conditions in the surrounding seagrass beds as a proxy for growth requirements in the s outhern IRL. Although more research is needed to determine the maximum soil organi c matter content or current velocity that IRL seagrasses can tolerate, th is study provided a range of values which can be identified in a healthy seagrass bed. The results from th is study also offered baseline data for future monitoring at SL 15 and additional knowledge of seagrass/landscape interactions. Soil/Landscape Analysis The transformation of SL 15 provided a uni que context in which pedology could be applied to an aquatic realm. The excava tion of the bay offered a view of recently exposed subaqueous material and a chance to observe how various soil-forming factors

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55 can develop spoil material into vegetatio n-supporting soil. Previous geology-based sediment models described the influence of geology, hydrology, and bathymetry (Folger, 1972; Demas and Rabenhorst, 2001), but certain ecological elements were not included. Following V.V. Dokuchaiev (1948) and Jennys (1941) adva ncement of soil forming factors, Demas and Rabenhorst (2001) proposed a new model for subaqueous soil formation: Ss = f (C, O, B, F, P, T, W, E) (eq. 4-1) Where subaqueous soil (Ss) properties are a function of climate (C), organisms (O), bathymetry (B), flow regime (F), parent mate rial (P), time (T), water column attributes (W) and catastrophic events (E). When applying this conceptual model at SL 15, these factors have appeared to aff ect the development of soil characteristics in the natural and constructed habitats. Bathymetry In the bay, bathymetry was observed as in fluencing the development of subaqueous soil characteristics. Depressional landform s (-38 to -60 cm, NAD 88) were related to relatively high (> 4%) concentr ations of OM content (Figur e 4-1). This relationship could have been caused by the accumulation of algae in depressional areas which senesced in place and added organic matter. Suspended particulate OM near the bottom could also have been trappe d by depressional features. Thickness of the F horizon was also relate d to bathymetry (Figure 4-2). The accretion of algae in depressi ons (-38 to -60 cm, NAD 88) most likely contributed to the development of the F horizon through trap ping of fine-sized particles. The decomposition of algae in depressions would also explain the high average OM content of the F horizon (6.2%).

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56 Regression analyses were performed to relate currents, ba thymetry, and soil properties, but no significant statistical relati onships appeared other than OM content to elevation, F horizon thickness to elevation and percent silt to current velocity (Figure 43). Flow Regime Interactions of bathymetry and flow ener gy might also explain the accumulation of detritus in depressions and thus F horizon thic kness and OM content. Flow velocities were approximately four to five times slower (< 10 cm/s) in depres sions (-38 to -60 cm, NAD 88) than in mounded areas, which like ly reduced bottom sheer stress and allowed for particles to settle out of the water co lumn. Lower flow energy could have also allowed silt-sized particles, which would otherwise remain suspended, to fall to the bottom. A weak statistical relationship existed between si lt content and incoming flow velocities (r2=0.385, p=; Figure 4-3). The accreti on of algal detritus due to slow velocities could have also affected nut rient dynamics in the depressions. Although porewater sample locations for this study were selected at random, future sampling for possible relationships between elevation, ve locity, detritus accretion, and nutrient availability would be of interest. Parent Material Parent material might also be of si gnificance when considering the nutrient dynamics in the bay compared to the natural ha bitat. Although the IRL is considered to have terrigeneous quartz parent material (Hoskin, 1983; Short et al., 1993), the abundance of carbonate shells in the bay soils may indicate different source geology than the dominantly siliciclastic material in th e surrounding seagrass beds. Loss of CaCO3 by acidification indicated that th e F horizon had the highest am ount of carbonates, although

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57 the Cg horizons had the highest shell content of the bay soils (Table 3-2; Appendix A). The carbonates in the Cg horizons were mostly coarse-sized particles (>1 mm) and were possibly incompletely dissolved by 20 ml of 2 M HCl. The carbonates in the F horizon were smaller and more likely to be acid ified. The Cg horizons also had a higher percentage of sand than the F horizons (Table 3-2), which may have buffered its percent weight lost after acidification, whereas the lo ss of heavy carbonates in the more silty F horizon could have resulted in a higher per cent weight change. The high amount of carbonates in the bay soils might have longterm effects on nutrient storage and flux (Kitano et al., 1978; Short et al., 1993b). The presence of clay loam textures in th e Cg horizons further suggested differences in source material between the two habitats The clay loam was hypothesized to be a relict soil from a mangrove bed which becam e mixed with spoil material during the construction process. Although this soil occurs intermittently in the bay, its influence on the light environment was notable. Clay particles became easily suspended when disturbed, thus clouding the bay water for severa l hours. Increased amounts of clay in the bay soils might also have future impact s on nutrient retention and mineralogy. Climate Climate, on a local scale, could also be contributing to the geochemical properties of soils in the bay. For example, localized increases in water temperature in the bay might be of significance for s eagrass growth, benthic activit y and detrital decomposition. On a low tide in July, water temperature within the bay was more than 5o C higher than in the natural habitat, possibly because of re stricted flow exchange through the flushing channels. Studies have shown that increas ed temperature and salinity exacerbate the detrimental effects of sulfide toxicity (C arlson et al., 1994; Koch and Erskine, 2001).

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58 Although soil temperatures were not measur ed in this study, long-term temperature monitoring would be an intere sting component of future bi ogeochemical patterns in the bay. Organisms Although not included in sediment mode ls (Folger, 1972), organisms are as influential for aquatic soils as they are in terrestrial systems. Through chemical additions, such as organic matter deposits, and physical mixing, benthic flora and fauna play an integral role in diagen etic processes. In the natura l habitat outside of SL 15, the difference in soil color between vegetated a nd non-vegetated areas are indicative of how seagrasses have increased, either through the trapping of fine particles, or turnover of biomass, the carbon content of the soil on whic h they grow. For the subaqeuous soils in the constructed habitat, observations of burrowing crabs and senescent macroalgae indicated that the newly crea ted habitat is already subj ect to biotic engineering. Time The influence of time was evident in suba queous soil characterist ics in the bay and natural habitat. Significant morphological differe nces in the soils from both habitats can be readily explained by the time needed for formation. The Ab horizons in the bay had color, texture, and OM conten t that was similar to the A horizon from the natural habitat, thus supporting the hypothesis that SL 15 was built on top of a pre-existing seagrass bed. The subaqueous soils from the natural habitat have therefore experienced at least 60 years of development. The subaqueous soils in the bay were plowed by construction equipment in the last 12 months Within the last year, howev er, changes have occurred in the upper 10 cm of soil within the bay. Fine particles have accreted in depressions and might thicken over time, possibly leading to bathymetric features becoming more

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59 uniform. The flow of water from the ma ngrove zone during outgoing tides has also created gullies and deltas on the north bank of the bay, c ontinually reshaping the bay geomorphology. Although significant differences appeared in the subaqueous soils in the bay and outside habitat, time could be an important factor when comparing the two ecosystems. Difficulty arises when discussing at what poi nt a constructed system reaches equilibrium, but long-term observations of subaqueous soil development might reveal changes indicating that the habitat in the bay is more closely re sembling the surrounding natural environment. Catastrophic Events Catastrophic events were not examined dur ing the study, but in the fall of 2004, Ft. Pierce experienced two major hurricanes (F rances and Jeanne). Baseline data for subaqueous soils near SL 15 were not avai lable for comparison, but the shallowness (average depth <2 m) of the IRL suggests that catastrophic wind ev ents might have an effect on surface subaqueous soils. Sandbar movement and vegetation removal is likely if a storm were to hit on low tide. Strong wi nd events might be of importance in the bay considering the high amounts of clay that could become re-suspended. Although not specified as a catastrophic event (Demas and Rabenhorst, 2001), dredging and human disturbance should also be infe rred as a forming factor. The excavation of the bay in SL 15 was performed with large constr uction equipment which moved 69,000 m3 of soil. If the flushing channels in SL 15 require dredging in the future additional large-scale soil movement might affect suba queous soils in the bay.

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60 Water Column Attributes The effects of water column attributes were not analyzed and me rit further attention at SL 15 with regard to organic matter depos ition and nutrient concen trations. Long-term monitoring of water quality properties such as total suspended solids, dissolved oxygen and chlorophyll might contribute to an unde rstanding of how water column attributes affect soil properties in the bay. Subaqueous Soil Survey The subaqueous soil survey of the bay revealed that so il properties were most closely related to landscape posi tion. The thickness of F horizons, as well as the particlesize distribution and OM content of soils in the bay varied acro ss each landscape unit. Similar to a terrestrial survey, variation also occurred within each landscape unit, showing how survey scale can either capture or exclude soil heterogeneity. The finescale of the bay soil su rvey (1:1,200) was more detailed th an a traditional soil survey (e.g. 1:20,000). Despite the 1:1,200 scale, features such as mounds and depressions that were less than 50 m2 could have affected soil descriptions and comparisons to the soils in the natural habitat. An increased number of samples ( n >30), along with DEM validation points, could have produced a more accurate soil map. The subaqueous soil survey was also lim ited in taxonomic terms. As yet, subaqueous soils lack a clear definition in Soil Taxonomy (Soil Survey Staff, 2003). Although the soils in the bay had different phys ical and chemical properties than soils from the natural habitat, they classify as the same soil because the particle-size control section for Mollisols is 25 to 100 cm below the surface (Soil Survey Staff, 2003). Most bay soils had an Ab horizon at that depth, wh ich had textures similar to the A horizon in the natural habitat, thus thei r identical classification. Res earch in Rhode Island produced

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61 a subaqueous soil survey with soil descriptions, such as fine-silty over sandy, mixed, nonacid, Thapto-Histic Hydraquents, because a buried O horizon occurred in the soil (Bradley and Stolt, 2003). The unique c onstruction of SL 15, however, prevents an accurate taxonomic description of the soils present, such as a buried A horizon and dredged spoil material. These soils are nonetheless important to consider when describing the physical environment for the pur pose of explaining seagrass colonization and subsequent growth. Subaqueous soil research at SL 15 co ntributed to an understanding of seagrass/soil/landscape interactions in the IR L, but also expanded the geographic range of subaqueous soil knowledge in the state of Florida. Previous subtropical subaqueous soil research was conducted in Cedar Key on the west coast of Florid a in a near-shore environment (Ellis, 2006). Results from SL 15 showed that subaqueous soils from an enclosed lagoon system on the east coast were similar to soils in the near-shor e sites on the west coast. The OM content for both systems averaged less than 5% (Ellis, 2006). Colors varied slightly, with west coast soil s having hues of 2.5Y, as opposed to 5Y in the IRL. Particle-size distributions from Ceda r Key were typically 85 to 95% sand, with a dominantly medium-sized sand fraction. These soils were coarser in grain size than the loamy sands near SL 15 which were on aver age less than 85% very fine-sized sand. General soil characteristics were similar on both coasts, with dark colors and higher organic matter in vegetated soils compared to unvegetated soils. Subaqueous soil research in Rhode Island (Bradley and Stolt, 2003) and Maryland (Demas and Rabenhorst, 1999) also applie d pedology to lagoonal estuaries and contributed to landscape-leve l understandings of vegetate d aquatic systems. The

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62 investigation of soils at SL 15 followed si milar methodologies and concepts from these previous studies, such as the generation of bathymetric maps and the classification of the landscape into soil map units. Adaptations were made, however, for soil sampling techniques. While previous studies employed bucket augers McCauley peat samplers and vibracores (Demas et al., 1996; Bradley and Stolt, 2003; Ellis, 2006) preserving soils from the IRL for description and analys is required acrylic push-cores. In the larger context of soil science, th e results from this study propose the addition of the F horizon to the Soil Survey Handbook. Aquatic habitats with rooted vegetation attenuate energy and most likely accumulate fi ne-sized particles. Because this layer occupies the subaqueous soil surface, its properties could be of biogeochemical significance for seagrasses and should therefore have a designated term. The upper 3 to 5 cm of soil in the bay and natural habitat was characterized by cohe sive particles which were most likely deposited by sedimentary proc esses, such as microalgal precipitation. Although the F horizon had n values greater than 1, it wa s more consolidated than a nepheloid layer, which in sedimentology is a layer of highly turbid bottom water (Chambers and Eadie, 1981). Soil Taxonomy (1975) describes limnic materials that share similar properties to the proposed F hor izon, the term limnic, however, connotes freshwater conditions. The F horizon could ther efore possibly be defined as organic or mineral surface soil material which can be found in association with coastal submerged aquatic vegetation and originates from depositional processes. Light Availability During the 1990s, more than 60% of seagrass literature focused on light (Koch, 2001). Because of the importance of light fo r photosynthesis, this parameter has been thoroughly studied and was the initial meas urement in the bay to determine the

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63 possibility that seagrasses c ould persist in SL 15. The water column within the bay had Kd values which were similar to the outside of the island and demonstrated a light environment suitable for seagrass growth. Irradiance values showed that an average of 82% of surface light was reaching the botto m of the bay, well above the minimum threshold 23% to 37% repor ted in the literature for H. wrightii and S. filiforme (Gallegos and Kenworthy, 1996; Kenworthy and Fonseca, 1996). Light availability is in large part, a f unction of suspended particles in the water column. Thus the lack of differences in Kd values in the bay and natural habitat inferred that each environment shares similar water column attributes. Chlorophyll a measurements supported the idea of similar wa ter characteristics in both habitats. No significant difference in chlorophyll a measured in the bay and the amount measured in the surrounding seagrass ha bitats. All chlorophyll a values were also well below the mean for the south IRL (12.1 g/L; 1988-1994) as reported by the St. Johns River Water Management District (Sigua et al., 1999). Although light conditions in the bay were deemed as sufficient for seagrasses, the a bundance of potentially light attenuating factors including macroalgae, epiphytes, and clay particles suggests th at long-term monitoring of irradiance in the bay would be an asset to th e future management of water clarity in SL 15. Hydrodynamics The effects of hydrodynamics on seagrass ecology/physiology and geochemistry have been demonstrated. Seagrasses in the IRL grow in a diversity of flow regimes, ranging from channels near inlets to pr otected deep-water c oves (Virnstein, 1995; Virnstein et al., 1997). At SL 15, H. wrigthii grows on a shallow bar next to the channel where it receives high energy waves from boa ting traffic, but it also grows in mixed

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64 stands on the south side of the island, a lower energy environment. Koch (1994) determined a minimum velocity for T. testudinum to be 5 cm s-1 for maximum photosynthetic rates. The duration of this velocity, however, was not specified. The temporal variation of tidal flows in any habitat then poses the question of how long maximum and minimum velocities persist. On one part of the tidal cycle at SL 15, 23% of the bay fell below the 5 cm s-1 threshold. The majority of the bay, however, was faster than 5 cm s-1 on both tides and--by comparison to th e literature and to the surrounding habitatwas thus classified as suitable for growth of T. testudinum The water flow data, however, was collected as a snapshot of daily conditions and does not reflect the variability of flow conditions over time. The lack of published flow requirements for seagrass species in the IRL hinders a supporta ble conclusion about the bay being suitable or unsuitable for seagrass growth, but flow ve locities were considered to be an important factor to measure when investigating the physical attributes of the bay. Although averaged current ve locities in the bay and natural habitat were not significantly different, the data showed many flow observations that were up to four times as fast as the rest of the bay and thus could have created a higher average. Velocities and direction appear ed to be influenced by proxim ity to the flushing channels and possibly bottom topography. The geomorphology of the narrow channels created areas of constriction and fast flows, while th e depressional areas a ppeared to relate to reduced current flows. The hydrodynamic data in the bay on both tides showed that certain areas repeatedly experience faster curr ent velocities, while areas in the center of the bay experience a wider range of flow sp eeds, depending on tidal strength and bottom features.

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65 Interactions of current veloci ty, soil texture, and organic matter accretion have been previously cited as being important for seagra ss health in the IRL. Morris and Virnstein (2004) observed an area in the northern IR L which experienced a loss of 100 ha of seagrass which they hypothesized to be caused by its restricted flushing abilities. They noted that a 10 to 15 cm thick layer of organic detritus and ooze had built up and suggested that the lack of pr oper circulation and increased sulfides led to a die-back event. Although no statistical relationships appeared betwee n current velocity and OM content or F horizon thickness in the bay, the continual accretion of silt and detritus in low energy areas in the bay might be an im portant variable to monitor over time. Nutrients A baseline assessment of porewater nutrie nts at SL 15, however, was performed in order to obtain a general char acterization of nitrogen and phosphorus levels in the soils from the bay and natural habitat. Pore water in the recently constructed bay was hypothesized to have lower nutrient concentr ations than the surrounding seagrass beds due to its recent exposure and lack of bi omass. The results showed no significant differences in TDP levels between the bay and natural habitat, but si gnificant differences did occur in TDKN. The relatively small samp le number (n=14) could have contributed to the statistical differences, as well as s easonal fluxes in nitrogen pools in the outside seagrass habitat. Short et al. ( 1993) noted that nitrogen dynamics for S. filiforme in the IRL were directly related to light varia tions and growing seas on. Porewater nitrogen pools appeared to be lower during summer gr owth periods when plant nutrient uptake increased (Short et al., 1993). Since porewater samples were taken in August, this could be a possible explanation for the lower TDKN in the seagrass habitat outside of SL 15 than in the bay. By comparison to the natura l habitat, nitrogen availability in the bay

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66 appeared to be significantly higher, thus suggesting le ss of a limitation for seagrass growth. Short et al. (1993b) also determined that the IRL is not phosphorus limited, and that phosphate concentrations between 0.06 mg/L and 0.87 mg/L would supply enough phosphorus to support seagrass growth. The meas ured TDP values in the bay and natural habitat were in this range (0.6 mg/L in the bay, 0.4 mg/L in the natural habitat outside the bay). Transplant Experiment The general purpose of the transplant expe riment was to assess the viability of H. wrightii within the bay. The results showed that two of the transplant plots in the bay experienced total mortality, while the three pl ots outside of SL 15, and one inside the bay had various levels of survivorship. Because each plot location varied in geography and elevation, it was difficult to as certain the cause of mortality. The surviving transplants in TQ-2 suggested that seagrasses were able to grow in the bay, and the surviving transplants in the natural habitat suggested th at mortality might not have been directly related to planting technique. It was noted that on extreme low tides, TQ-1 and TQ-3 were completely exposed. During these low tides, observations revealed that mounded areas in the bay were at hi gher elevations than the surr ounding seagrass beds. Water height in the outside natural habitat was less than 5 cm at times, but most seagrass blades remained unexposed to air. Desiccation, ther efore, could have been a possible cause of the 100% loss in TQ-1 and TQ-3. Shoots were still present in TQ-2 after a storm event which damaged its cage. All shoots, however had disappeared from TQ-1 which had no cage damage, suggesting that grazing aff ects were not the cause of mortality. Interestingly, the plots which experienced th e most shoot loss showed no signs of dead

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67 seagrass remnants, appearing as if the transp lants were completely removed. The lack of senescent seagrass blades could have possibl y been the result of scavenging, high energy flow, or wind events. The results of the transplant experime nt were expected based on lack of transplanting experience, as well as a statisti cally small number of samples. Additional observations on blade length, for example, woul d have contributed to an understanding of shoot productivity rather than just viability. A control plot with caging but no transplants would also have been useful in determining the extent of natural colonization in the bay and natural habitat. The question of the abilit y of seagrasses to survive (at least for short periods) in the bay was answered by the re sults in TQ-2, and further supported upon the discovery of seagrass recruits in May, 2006. Seagrass Recruitment The main research question of this study asked if the environmental conditions in the constructed habitat of SL 15 were suffici ent for seagrass growth. The approach was to compare the ecosystem in the bay to the ecosystem in the proximate natural seagrass beds. The original research question wa s partially answered by the viability of transplanted seagrasses and more directly an swered by the discovery of natural recruits. H. wrigthii, S. filiforme, H. johnsoni i, H. dicipiens, H. englemanii and T. testudinum became established in the bay, mostly in areas outside of the region deemed supportive by the habitat suitability model. The absence of recruits in the flushing ch annels demonstrated that colonization was not by rhizome. Sexual reproduction in H. wrightii and H. johnsonii is either rare, or non-existent, so their colonization was most likely not by extension of rhizome, but development of fragments (Phillips, 1960; Eiseman and McMillan, 1980; Jewett-Smith et

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68 al., 1997; Hall et al., 2006). Floating fragments of H. wrightii were frequently observed in and around SL 15 and previous studies have shown that fragments remain viable for up to four weeks in the spring (Hall et al., 2006). H. johnsonii also propagates by fragments, but its viability is on the order of days (Hall et al., 2006). The similarities in seagra ss distribution to macroalg ae distribution along an eastwest gradient were apparent. This pattern implies that flow or possibly wind directions, rather than soil, had more significant eff ects on vegetative coloni zation in the bay. A high percentage of lower elevations (-45 to -60 cm, NAD 88) occur on the west side of the bay, as well as areas of consistent low flow. The east-west orientation of the bay might also be allowing fragments to float in from the high energy channel, and become deposited in the low energy depressional areas The most southwest flushing channel is also protected by outcrops of mangroves, thus creati ng a protected cove. Habitat Suitability Model Results from Objective 1 were compiled into a habitat suitability model which calculated the intersection of areas in the bay that were similar to the natural habitat. This model predicted 14% of the bay as bei ng supportive for seagrasses. Observations of benthic colonization, however, showed that seagrass recruitment occurred in more than 14% of the bay. Recruits grew in elevations ranging from -20 cm to -55 cm (NAD 88), demonstrating that elevation, a nd therefore light availability was non-prohibitive. It is likely also that the hydrodynamics in the bay were also non-prohibitive. Although H. johnsonii is restricted in its ge ographic range, it grows in a variety of physical environments, such as high energy sandy channe ls and deep water s oft mud (Virnstein et al., 1997; Heidelbaugh et al., 2000). The thresholds for curr ent velocities in the model were therefore possibly too narrow. Hydrodynamic conditions in the bay that were

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69 deemed similar to the natural habitat include d current velocities which were within one standard deviation of the mean outside velocit y, yet currents on the outside of SL 15 were also highly variable. A wide r variation of flow speeds should therefore have been taken into account in the model. Because specific elevation ranges for di fferent seagrass species are not known, elevation was not incorporated into the habitat suitability mo del, but colonization patterns in the bay suggested that different specie s occupied different landscape positions. H. johnsonii commonly grew in areas of hi gher elevation (<-20 cm) than H. wrigthii and S. filiforme Although lower depth limits are published for seagrasses in the IRL (Gallegos and Kenworthy, 1996; Steward et al., 2005), upper limits have not been quantified. Virnstein (1995) noted that H. wrigthii is occasionally exposed at lowest tides and that S. filiforme is rarely in very shallow water (< 15cm). These comments partially explained the distribu tion of recruits in the bay in that S. filiforme grew in elevations deeper than -20 cm. H. wrightii however, had not yet co lonized areas which were observed to be exposed on low tides. The two H. wrightii transplant plots which were exposed also experienced the highest mort ality, thus showing the need to properly quantify the desiccation tolerance for each sp ecies. A reclassification of the DEM might have contributed an additional i nput layer to the habitat suitab ility model as a predictor of species distribution, but furthe r information on the depth ranges for IRL seagrasses would be needed. In summary, because of restricting th resholds, the habitat suitability model underestimated the area which was considered to have sufficient conditions to support seagrasses. The successful colonization of SL 15 suggested that species such as H.

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70 wrightii S. filiforme, and H. johnsonii are resilient to a hete rogeneous environment, which in certain aspects, might vary significantly from proximate areas. Figure 4-1. Relationship of bathymetry to OM content. As elevation decreases (depth increases), OM content increase s. The significance level was p=0.009 ( =0.05).

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71 Figure 4-2. Relationship between elevati on and F horizon thickness. As elevation decreased, F horizon thickness increased. The significance level was p=0.000 ( =0.05). Figure 4-3. Relationship between silt % and current velocity. Low current velocities were related to high silt content, poss ibly because decreased energy allowed fine particles to settle. This relation ship suggests that hydrodynamics have an effect on particle size distributions in the bay. The significance level was p=0.014 ( =0.05)

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72 CHAPTER 5 SUMMARY AND CONCLUSIONS The quantification of physical parameters su ch as light, nutrient s, currents, and soil properties at SL 15 was important for understand ing the suitability of the constructed bay for seagrasses. By comparison to the li terature and surrounding ecosystem, the light environment in the bay was deemed sufficien t for colonization. Porewater TDKN varied between the bay and natural ha bitat, but was possibly a reflection of seasonal fluxes in seagrass nitrogen pools. Values of TDP were determined to be a non-prohibitive nutrient in either habitat. Water velocity and direc tion in the bay varied w ith tide and location, usually with fast flows in the flushing channels. The accumulation of fine particles and organic matter in depressional areas suggested that flow energy and bathymetry were signifi cant subaqueous soil forming factors in the bay. The thickness of the F horiz on increased with decreasing elevations. Organic matter content was higher in the F hor izon than in the A horizon from the natural habitat. Soil textures in the bay were spat ially variable, but on average, had higher clay content than soils in the natural habitat. These clay loam textures, when disturbed, caused considerable clouding in the bay and mi ght impact light availability at times. Observations of these environmental c onditions emphasized how interactions and feedback cycles can potentially influence an ecosystem. Although considerable spatia l variability occurred in the bay with regard to hydrodynamics and subaqueous soil properties, this heterogeneity did not appear to hinder seagrass recruitment. A habitat suitab ility model, created to show suitable areas

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73 for seagrass growth in SL 15, found that 14 % of the bay had hydrodynamic, soil, light, and nutrient conditions which were similar to the natural habitat. Recent colonization, however, has appeared to be successful in al most two-thirds of the bay. The abundance and distribution of recruits in the bay suggest that seagrass es are able to colonize in a heterogeneous environment. With increasing coastal development in Florida, anthropogenic influences on seagrasses will likely lead to increases in mitigation efforts. Although this study focused on an IRL spoil island, the results could be applied to future management efforts elsewhere. Because the distri bution of seagrasses in the bay appeared to be influenced by flow patterns and elevation, consideration s hould be taken for island orientation and construction. An east-west direction of th e bay and flushing channels might provide an increased supply of fragments and seeds, t hus increasing possibili ties for seagrass recruitment. Proper knowledge of extreme tid al cycles and more uni form bathymetry in the bay might prevent certain areas from becoming exposed to desiccation. Less variation in elevation could al so prevent the accumulation of organic-rich F horizons. It could be speculated that le ss organic material would decrease available substrate for decomposition and therefore decrease th e likelihood of sulfide toxicity. Although this study quantified certain envi ronmental parameters in the bay and could offer baseline data for future resear ch at SL 15, more long-term monitoring would contribute to the development of future spoi l island mitigation endeavors. Porewater nutrients were generally char acterized by this study, but an outlier of high TDKN and TDP in the deepest elevation (-60 cm, NAD 88) in the bay indicates that a more thorough analysis of nutrients in the ba y is warranted. Semi-permanent flow sensors in the bay and

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74 natural habitat might also provide more specific information on current velocity requirements for seagrasses in the IRL. In situ light meters could contribute to the understanding of how weather events might affe ct water clarity in the bay. A desiccation experiment in which different IRL species are exposed for various periods of time in different soils would also be informative as to the upper depth limit at which different taxa can survive. Finally, the continual development of subaqueous pedology concepts and techniques, as well as the geographic e xpansion of subaqueous soil characterization, will contribute to the understanding and mana gement of protected coastal environments.

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75 APPENDIX A SUBAQUEOUS SOIL DESCRIPTIONS Figure A-1. Soil sampling locations in the bay and natural habitat. Transect number and core number are labeled. O-1, O-2 and O3 were cores taken from the natural habitat. Numbers 1-6 were soils desc ribed in the natural habitat (sample numbers SG)

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76 Table A-1. Subaqueous soil descriptions from th e natural habitat. Coordinates are in State Plane East (feet, NAD 83). Location: GPS 1 (X = 875537.4; Y=1144027.65) Date: August 22, 2005 Personel: Hurt, Ellis, Fischler Sample IDs: SG1-SG5 Map Unit: Vegetated Flat Undifferentiated Draina g e: very poorly drained Native ve g etation: S. filiforme Water level when sampled: above surface Parent material: sandy and loamy marine sediments Dail y low water: exposed at low tide Ph y sio g raph y (landform): vegetated flat Moisture status: wet, drained to moist Relief: nearly level Permeabilit y : moderately rapid Elevation: below MSL Salt or Alkali: none Slope: <1% Stones: none Aspect: south and west % Coarse framents: 7 Erosion: none % Cla y : 9 A1 0-6 cm; black (N2.5/0) sandy loam ; structureless and very fluid n value more than 1; common fine and medium live root s; moderately alkaline; abrupt wavy boundary. A2 6-32 cm; black (5Y 2.5/1) sandy lo am; structureless and very fluid, n value more than 1; common fine and medium live root s; moderately alkaline; clear smooth boundary. A3 32-42 cm; black (5Y 2.5/1) gravelly loamy sand; weak fine and medium subangular structure; fria ble to very friable, n value less than 0.7; common fine and medium live and dead roots; 15 % shell frag ments; moderately alkaline; clear smooth boundary. A4 42-80 cm; greenish black (10Y 2.5/1) loamy sand; weak fine and medium subangular structure; fria ble to very friable, n value less than 0.7; common fine and medium live and dead roots; 5 % shell frag ments; moderately alkaline; clear smooth boundary. A5 80-140 cm; greenish black (10Y 2.5/1) loamy sand; weak fine and medium subangular structure; fria ble to very friable, n value less than 0.7; 5 % shell fragments; moderately alkaline. Unable to sample soil below 140 cm; materi al appeared to be sandy with few shell fragments and colors similar to material above.

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77 Table A-1 Continued Location: GPS 2 (X=875958.15; Y=1144009.91) Date: August 22, 2005 Personel: Hurt, Ellis, Fischler Sample IDs: SG6-SG9 Map Unit: Vegetated Flat Undifferentiated Draina g e: very poorly drained Native ve g etation: T. testudinum S. filiforme Water level when sampled: above surface Parent material: sandy and loamy marine sediments Dail y low water: exposed at low tide Ph y sio g raph y (landform): vegetated flat Moisture status: wet, drained to moist Relief: nearly level Permeabilit y : moderately rapid Elevation: below MSL Salt or Alkali: none Slope: <1% Stones: none Aspect: south and west % Coarse framents: 3 Erosion: none % Cla y : 8 A1 0-9 cm; black (5Y 2.5/1) sandy loam; structureless and very fluid, n value more than 1; common fine and medium live root s; moderately alkaline; abrupt wavy boundary. A2 9-24 cm; black (5Y 2.5/1) loamy sand; weak fine and medium subangular structure; friable to very friable, n value less than 0.7; common fine and medium live and dead roots; less than 5 % shell fragments; moderately alkaline; clear smooth boundary. A3 24-62 cm; greenish black (10Y 2.5/1) loamy sand; weak fine and medium subangular structure; fria ble to very friable, n value less than 0.7; common fine and medium live and dead roots; less than 5 % sh ell fragments; moderately alkaline; clear smooth boundary. A4 62-88 cm; black (2.5Y 2.5/1) sand; structureless; loose, n value less than 0.7; 5 % shell fragments; moderately alkaline. Unable to sample soil below 88 cm; materi al appeared to be sandy with few shell fragments and colors similar to material above.

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78 Table A-1 Continued Location: GPS 3 (X=876145.7; Y=1143424.46) Date: August 22, 2005 Personel: Hurt, Ellis, Fischler Sample ID: SG15-SG19 Map Unit: Vegetated Flat Undifferentiated Draina g e: very poorly drained Native ve g etation: H. wrightii Water level when sampled: above surface Parent material: sandy and loamy marine sediments Dail y low water: exposed at low tide Ph y sio g raph y (landform): vegetated flat Moisture status: wet, drained to moist Relief: nearly level Permeabilit y : moderately rapid Elevation: below MSL Salt or Alkali: none Slope: <1% Stones: none Aspect: south and west % Coarse framents: 3 Erosion: none % Cla y : 10 C 0-2 cm; 80 % gray (5Y 4/1) and 20% black (N 2.5/0) sand; loose, n value less than 0.7; common fine and medium live and dead roots; moderately alkaline; abrupt wavy boundary. Ab1 2-13 cm; black (N 2.5/1) sand; weak fi ne and medium subangular structure; friable to very friable, n value less than 0.7; common fine and medium live and dead roots; less than 5 % shell fr agments; moderately alkaline ; abrupt smooth boundary. (this horizon combined with C for sampling purposes) Ab2 13-47 cm; black (5Y 2.5/1) sand; weak fine and medium subangular structure; friable to very friable, n value less than 0.7; common fine and medium live and dead roots; less than 5 % shell fragments; moderately alkaline; clear smooth boundary. Ab3 47-59 cm; greenish black (10Y 2.5/1) sa nd; weak fine and medium subangular structure; friable to very friable, n value less than 0.7; 5 % sh ell fragments; moderately alkaline; clear smooth boundary. Ab 59-74 cm; greenish black (10Y 2.5/1) loamy sand; weak fine and medium subangular structure; fria ble to very friable, n value less than 0.7; common fine and medium live and dead roots; less than 5 % shell fragments; moderately alkaline. Unable to sample soil below 74 cm; no clue as to the properties of the material

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79 Table A-1 Continued Location: GPS 4 (X=875730.06; Y=1142942.93) Date: August 22, 2005 Personel: Hurt, Ellis, Fischler Sample ID: SG26-SG28 Map Unit: Vegetated Flat Undifferentiated Draina g e: very poorly drained Native ve g etation: S. filiforme, H. wrightii (sparse) Water level when sampled: above surface Parent material: sandy and loamy marine sediments Dail y low water: exposed at low tide Ph y sio g raph y (landform): vegetated flat Moisture status: wet, drained to moist Relief: nearly level Permeabilit y : moderately rapid Elevation: below MSL Salt or Alkali: none Slope: <1% Stones: none Aspect: south and west % Coarse framents: 3 Erosion: none % Cla y : 5 A1 0-10 cm; black (N 2.5/1) loamy sand; structurless; loose; very fluid, n value more than 1.0; common fine and medium live and d ead roots; less than 5 % shell fragments; moderately alkaline; abrupt smooth boundary. A2 10-37 cm; greenish black (10Y 2.5/1) loamy sand; weak fine and medium subangular structure; fria ble to very friable, n value less than 0.7; common fine and medium live and dead roots; less than 5 % shell fragments; moderately alkaline; clear smooth boundary. A3 37-61 cm; very dark gray (5Y 3/1) sand; weak fine and medium subangular structure; friable to very friable, n value less than 0.7; less th an 5 % shell fragments; moderately alkaline. Unable to sample soil below 61 cm; materi al appeared to be sandy with few shell fragments and colors similar to A3 horixon. A thin (less than a few mm) dark gray (5Y 4/1) sand C horizon covers the A1 horizon in most of the pedon; not sampled.

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80 Table A-1 Continued Location: GPS 5 (X=874853.15; Y=1143951.62) Date: August 22, 2005 Personel: Hurt, Ellis, Fischler Sample ID: SG10-SG14 Map Unit: Vegetated Flat Undifferentiated Draina g e: very poorly drained Native ve g etation: sand bar with sparse H. wrightii Water level when sampled: above surface Parent material: sandy and loamy marine sediments Dail y low water: exposed at low tide Ph y sio g raph y (landform): vegetated flat Moisture status: wet, drained to moist Relief: nearly level Permeabilit y : moderately rapid Elevation: below MSL Salt or Alkali: none Slope: <1% Stones: none Aspect: south and west % Coarse framents: 3 Erosion: none % Cla y : 9 C 0-6 cm; 80% olive gray (5Y 4/2) and 20% black (N2.5/0) sa nd; structureless; loose, n value less than 0.7; no roots; moderately alka line; abrupt wavy boundary. Ab1 6-8 cm; black (N2.5/0) sand; weak fine and medium subangular structure; friable to very friable, n value less than 0.7; common fine a nd medium live and dead roots; less than 5 % shell fragments; moderately al kaline; abrupt wavy bounda ry. (this horizon was not sampled) Ab2 8-28 cm; 50% very dark gray (5Y 3/1) and 50% dark gray (5 Y 4/1) sand; weak fine and medium subangular struct ure; friable to very friable, n value less than 0.7; common fine and medium live and dead roots; less than 5 % shell fragments; moderately alkaline; clear smooth boundary. Ab3 28-50 cm; very dark gray (5Y 3/1) gr eenish black (10Y 2.5/1) sand; weak fine and medium subangular structure; friable to very friable, n value less than 0.7; less than 5 % shell fragments; moderately alkaline; clear smooth boundary. Ab 50-68 cm; greenish black (10Y 2.5/1) sandy loam; weak fine and medium subangular structure; fria ble to very friable, n value less than 0.7; common fine and medium live and dead roots; less than 5 % shell fragments; moderately alkaline. Unable to sample soil below 68 cm; no clue as to the properties of the material

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81 Table A-1 Continued Location: GPS 6 (X=874911.44; Y=1143378.84) Date: August 22, 2005 Personel: Hurt, Ellis, Fischler Sample ID: SG20-SG25 Map Unit: Vegetated Flat Undifferentiated Draina g e: very poorly drained Native ve g etation: H. johnsonii Water level when sampled: above surface Parent material: sandy and loamy marine sediments Dail y low water: exposed at low tide Ph y sio g raph y (landform): vegetated flat Moisture status: wet, drained to moist Relief: nearly level Permeabilit y : moderately rapid Elevation: below MSL Salt or Alkali: none Slope: <1% Stones: none Aspect: south and west % Coarse framents: 3 Erosion: none % Cla y : 10 C 0-0.5 cm; dark gray (5Y 4/1) sand; structureless; loose, n value less than 0.7; no roots; moderately alkaline; abrupt wavy bounda ry. (this horizon comb ined with Ab1 for sampling purposes) Ab1 0.5-13 cm; black (N 2.5/1) loamy sand; weak fine and medium subangular structure; friable to very friable, n value less than 0.7; common fine and medium live and dead roots; less than 5 % shell fragments; moderately alkaline; abrupt smooth boundary. (this horizon combined with C for sampling purposes) Ab2 13-44 cm; greenish black (10Y 2.5/1) loamy sand; weak fine and medium subangular structure; fria ble to very friable, n value less than 0.7; common fine and medium live and dead roots; less than 5 % shell fragments; moderately alkaline; clear smooth boundary. Ab3 44-66 cm; greenish black (10Y 2.5/1) loamy sand; weak fine and medium subangular structure; fria ble to very friable, n value less than 0.7; 5 % shell fragments; moderately alkaline; clear smooth boundary. Ab4 66-84 cm; greenish black (10Y 2.5/1) loamy sand; weak fine and medium subangular structure; fria ble to very friable, n value less than 0.7; common fine and medium live and dead roots; less than 5 % sh ell fragments; moderately alkaline; clear smooth boundary. Ab4 84-100 cm; greenish black (10Y 2.5/ 1) sand; structureless; loose, n value less than 0.7; less than 5 % shell fragments; moderate ly alkaline. ((no sample of this horizon combined was obtained) Unable to sample soil below 100 cm; no clue as to the properties of the material

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82Table A-2. Soil descriptions from the bay. C oordinates are in State Plan e East (feet, NAD 83). Shell % was not recorded for n/ a. Boundary transitions are diffuse (D), gra dual (G) and clear (C) and topography is wavy (W) or smooth (S). Roots are fine (f) or very fine (vf). F stands for flock horizon. ID is the transect number (T1) and core number (-1). IDX_coordY_coordHorizonDepth (cm)SampleColorShell %n-valueBoundaryRoots T1-1875866.401143441.67A0-615Y 3/1n/a< 0.7CWnone T1-1875866.401143441.67Cg16-10.525Y 5/2n/a< 0.7CWnone T1-1875866.401143441.67Cg210.5-2132.5Y 5/2n/a< 0.7GWnone T1-1875866.401143441.67Ab21-3245Y 4/1n/a< 0.7few vf T1-2875867.151143430.13F0-255Y 2.5/1n/a>>1GWnone T1-2875867.151143430.13A0-965Y 4/1n/a< 0.7CSnone T1-2875867.151143430.13C9-1675Y 5/2n/a< 0.7GWnone T1-2875867.151143430.13Ab/C16-3285Y 3/1n/a< 0.7DWnone T1-2875867.151143430.13Ab32-3695Y 4/1n/a< 0.7few vf T1-3875865.691143419.05F0-2105Y 2.5/1n/a>>1CWnone T1-3875865.691143419.05A2-5115Y 5/2n/a>>1CWnone T1-3875865.691143419.05C/Ab5-20125Y 4/1n/a< 0.7none T1-3875865.691143419.05Ab/C20-32135Y 5/2n/a< 0.7none T1-4875868.621143402.71F0-4.5145Y 4/1n/a>> 1DSnone T1-4875868.621143402.71AC4.5-13155Y 5/1n/a0.7-1DSnone T1-4875868.621143402.71C13-23165Y 5/2n/a< 0.7none T1-4875868.621143402.71Ab23-25175Y 4/2n/a< 0.7none T1-5875868.811143395.86A0-4.5185Y 5/1n/a< 0.7none T1-5875868.811143395.86C4.5-13195Y 5/1n/a< 0.7none T2-1875810.581143426.96A0-3205Y 4/150.7-1GWnone T2-1875810.581143426.96Cg13-13215Y 5/115< 0.7CWnone T2-1875810.581143426.96Cg213-23225Y 5/15< 0.7CSnone T2-1875810.581143426.96Cg323-26235Y 5/10< 0.7CSnone T2-1875810.581143426.96Ab26-36.6245Y 3/22< 0.7few vf

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83Table A-2 Continued IDX_coordY_coordHorizonDepth (cm)SampleColorShell %n-valueBoundaryRoots T2-2875805.861143432.41F0-3255Y 4/10>>1CWnone T2-2875805.861143432.41Cg3-11265Y 5/110< 0.7CWnone T2-2875805.861143432.41Ab11-24275Y 2.5/11< 0.7few vf T2-3875798.031143438.13F0-1285Y 4/12>>1GWnone T2-3875798.031143438.13A/Cg1-5295Y 3/12.7-1GWnone T2-3875798.031143438.13Cg15-11305Y 5/120< 0.7CWnone T2-3875798.031143438.13Cg211-14315Y 5/20< 0.7CSnone T2-3875798.031143438.13Ab14-36325Y 4/12< 0.7few vf T3-1875760.961143323.93A0-2335Y 3/120< 0.7GWnone T3-1875760.961143323.93Cg12-22345Y 5/140< 0.7GWnone T3-1875760.961143323.93Cg222-30.5355Y 5/20< 0.7CSnone T3-1875760.961143323.93Ab30.5-46365Y 3/12< 0.7few vf T3-2875742.451143315.56F0-5375Y 2.5/10>>1CWnone T3-2875742.451143315.56Cg15-9385Y 5/220< 0.7GSnone T3-2875742.451143315.56Cg29-10395Y 5/21< 0.7CSnone T3-2875742.451143315.56Ab10-36405Y 3/11< 0.7few vf T3-3875723.601143305.64Cg/A0-3415Y 4/150.7-1GWnone T3-3875723.601143305.64Cg3-16425Y 5/140< 0.7none T3-4875744.401143289.79A0-4435Y 4/15>>1DWnone T3-4875744.401143289.79Cg4-8445Y 5/140< 0.7CWnone T3-4875744.401143289.79Ab8-32455Y 3/11< 0.7few vf T4-1875609.701143217.50A0-3465Y 4/150.7-1GWnone T4-1875609.701143217.50Cg3-14475Y 4/140<0.7CWnone T4-1875609.701143217.50Ab14-22485Y 3/11<0.7common f

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84Table A-2 Continued. IDX_coordY_coordHorizonDepth (cm)SampleColorShell %n-valueBoundaryRoots T4-2875616.701143248.82F0-1495Y 2.5/10>>1DWnone T4-2875616.701143248.82Cg/A1-18505Y 4/140<0.7GWnone T4-2875616.701143248.82Cg118-32515Y 5/12<0.7GWnone T4-2875616.701143248.82Cg232-35525Y 5/10<0.7CSnone T4-2875616.701143248.82Ab35-59535Y 3/115<0.7few vf T4-3875626.631143275.34F0-3545Y 2.5/10>>1GWnone T4-3875626.631143275.34CgA3-12555Y 4/150<0.7CWnone T4-3875626.631143275.34Ab12-27565Y 3/12<0.7few vf T5-1875483.191143219.23F0-3575Y 3/10>>1GWnone T5-1875483.191143219.23Cg3-12585Y 5/140<0.7GWnone T5-1875483.191143219.23Ab12-34595Y 3/12<0.7few vf T5-2 875507.271143193.19F0-3605Y 2.5/10>>1GWnone T5-2 875507.271143193.19Cg13-8615Y 5/15<0.7CSnone T5-2875507.271143193.19Cg28-9.5625Y 5/100.7-1CSnone T5-2875507.271143193.19Ab19.5-32635Y 3/12<0.7CWfew f T5-2875507.271143193.19Ab232-45.5645Y 5/160<0.7none T5-3875524.921143170.29F0-3655Y 3/11>>1GWnone T5-3875524.921143170.29Cg3-11665Y 5/12<0.7GWfew f T5-3875524.921143170.29Ab11-38675Y 4/15<0.7few vf T6-1875308.081143224.93F0-2685Y 2.5/10>>1GWfew f T6-1875308.081143224.93Cg/A2-8695Y 4/140<0.7CWnone T6-1875308.081143224.93Cg8-19705Y 5/230<0.7CSnone T6-1875308.081143224.93Ab19-30.5715Y 3/11<0.7few f

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85Table A-2 Continued IDX_coordY_coordHorizonDepth (cm)SampleColorShell %n-valueBoundaryRoots T6-2875289.381143212.32F0-2725Y 5/10>>1GWnone T6-2875289.381143212.32A2-5735Y 3/1200.7-1GWnone T6-2875289.381143212.32Cg5-14745Y 5/230<0.7CWnone T6-2875289.381143212.32Ab14-46755Y 3/11<0.7few f T6-3875271.031143204.74A0-3765Y 4/11<0.7GWfew f T6-3875271.031143204.74Cg3-9775Y 5/250<0.7CSnone T6-3875271.031143204.74Ab9-43785Y 3/11<0.7few f T6-4875326.671143235.69F0-6795Y 2.5/10>>1GWnone T6-4875326.671143235.69Cg6-16805Y 4/120<0.7CWnone T6-4875326.671143235.69Ab16-46815Y 3/11<0.7none Table A-3. Soil descriptions fr om the natural habitat. IDX_coordY_coordHorizonDepth (cm)SampleColorShell %n-valueBoundaryRoots O-1875366.541142958.71A10-15825Y 2.5/10 0.7-1GWfew f O-1875366.541142958.71A215-35835Y 4/15<0.7DWfew f O-1875366.541142958.71A335-50845Y 3/12<0.7few f O-2875572.521142852.57A10-10855Y 2.5/10>>1GWfew f O-2875572.521142852.57A210-30865Y 3/11<.7DWfew vf O-2875572.521142852.57A330-41875Y 4/13<0.7few f O-3875870.261143037.86F0-5885Y 2.5/10>>1GWnone O-3875870.261143037.86A15-15895Y 3/100.7-1DWnone O-3875870.261143037.86A215-38905Y 3/11<0.7few vf

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86 Figure A-1. Soils taken from transect 1 on the east side of the bay. The light brown color in the A and F horizons in T1-1 and T1-2 are oxidized surface layers.

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87 Figure A-2. Transect 2. The Cg2 and Cg3 hor izons were found intermittently throughout the bay and were clay loam or silty clay textures.

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88 Figure A-3. Transect 3. The light colored patch in the Ab hor izon in T3-1 is a pocket of air and thus shows lighter-c olored oxidized soils.

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89 Figure A-4. Transect 4.

PAGE 102

90 Figure A-5. Transect 5. The soil in T5-1 shows heterogeneity of shell content and texture throughout. This mixture was likely the result of the cons truction process.

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91 Figure A-6. Transect 6.

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92 APPENDIX B SUBAQUEOUS SOIL DATA Table B-1. Subaqueous soil data from the natural (outside) habitat. N/A is data that is not available. Sand fractions are displa yed as very coarse (VC, 2-1 mm), coarse (C, 1-500 m), medium (M, 500-250 m), fine (F, 250-106 m) and very fine (VF, 106-45 m). OM is organic matter. ID is the sample number. IDHorizonDepth (cm ) OM %Sand %Silt %Clay %VC %C %M %F %VF % SG 1A1 0-6n/a8010100013048 SG 2A2 6-322.66798130022848 SG 3A3 32-421.8285693133148 SG 4A4 42-801.290461013850 SG 5A5 80-1401.44894712103244 SG 6A1 0-9n/an/an/an/an/an/an/an/an/a SG 7A2 9-242.59798120012948 SG 8A3 24-622.33826110013348 SG 9A4 62-881.0993351124544 SG 10C 0-61.4494240002766 SG 11Ab1 6-8n/an/an/an/an/an/an/an/an/a SG 12Ab2 8-281.0195230003362 SG 13Ab3 28-501.2694240002766 SG 14Ab4 50-682.684790012558 SG 15C 0-21.6492250003062 SG 16Ab1 2-131.3894240013756 SG 17Ab2 13-471.292350003260 SG 18Ab3 47-591.4491450002961 SG 19Ab4 59-741.9288570012859 SG 20C 0-0.5n/an/an/an/an/an/an/an/an/a SG 21Ab1 0.5-13n/an/an/an/an/an/an/an/an/a SG 22Ab2 13-442.3787481133053 SG 23Ab3 44-662.4589470012760 SG 24Ab4 66-842.32856100012163 SG 25Ab5 84-100n/an/an/an/an/an/an/an/an/a SG 26A1 0-102.0389380013849 SG 27A2 10-372.3386590013351 SG 28A3 37-611.2293250014150

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93Table B-2. Subaqueous soil data from the bay. IDSampleHorizonOM%ElevSand %Silt %Clay %VC %C %M %F %VF % T1-11A2.12-22.008749111832205 2Cg11.49923561738255 3Cg22.948371049212723 4Ab2.7986681123648 T1-25F3.71-28.0073121549222314 6A2.518081141229268 7C4.207791471627188 8Ab/C3.3786691283540 9Ab3.1688481123647 T1-310F8.95-37.005721221272226 11A4.8354192715161913 12C/Ab3.988081237132829 13Ab/C2.4088471133846 T1-414F7.43-43.006572835101928 15AC8.0360112847132016 16C4.704342152714155 17Ab2.67365941221021 T1-518A3.58-42.0036568369144 19C1.84336072413104 T2-120An/a-29.004642123413188 21Cg18.278721241237314 22Cg25.096214230152828 23Cg36.695504500014 24Ab2.60863111013351 Elev= elevation (cm, NAD 88). n/a is data that is not available.

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94Table B-2 Continued. IDSampleHorizonOM%ElevSand %Silt %Clay %VC %C %M %F %VF % T2-225F8.22-36.00683301182137 26Cg3.556118212516326 27Ab2.52843131013448 T2-328F3.09-26.004145143415145 29A/Cg5.0362172148192011 30Cg15.82333037238119 31Cg26.212734390011015 32Ab2.2687590013451 T3-133A2.42-33.004246122615136 34Cg12.04875941331309 35Cg27.0419324912367 36Ab3.6885780013349 T3-237F6.80-40.0060142612122520 38Cg11.46911815294115 39Cg29.524723300131726 40Ab2.7886680123349 T3-341Cg/A3.51-40.0074121415192821 42Cg1.31914651337288 T3-443A5.61-36.00741016613251911 44Cg4.167981348172426 45Ab3.0088390133251 T4-146A1.99-32.00904651138297 47Cg1.33930671739255 48Ab3.0684791273143

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95Table B-2 Continued. IDSampleHorizonOM%ElevSand %Silt %Clay %VC %C %M %F %VF % T4-249Flock8.47-37.0053222424121818 50Cg/A2.23n/an/an/an/an/an/an/an/a 51Cg14.2677101313174213 52Cg210.31273043015138 53Ab2.4291451134047 T4-354Flock2.20-34.0069141726172222 55CgA2.6184214510252619 56Ab3.41881112483143 T5-157Flock11.47-37.007102934103024 58Cg4.09n/an/an/an/an/an/an/an/a 59Ab5.5485681143346 T5-2 60Flock4.85-37.0041451468182220 61Cg13.6378101225142829 62Cg25.483429372031316 63Ab13.40808121113146 64Ab21.2894241134345 T5-365Flock5.96-46.0050292135111813 66Cg2.238911048243518 67Ab1.7394240124448 T6-168Flock5.2031.0045401424101613 69Cg/A1.669226121934216 70Cg2.08875861233298 71Ab2.64862120013251

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96Table B-2 Continued. IDSampleHorizonOM%ElevSand %Silt %Clay %VC %C %M %F %VF % T6-272Flock3.90-40.00384913361298 73A3.158659112032176 74Cg2.86904681533259 75Ab2.5686580013450 T6-376Floc/A6.00-41.0044431324111512 77Cg2.7988581113232416 78Ab3.0185690013251 T6-479Flock9.10-50.0052173156111317 80Cg1.5492261118282015 Ab1.6791350014148 O-182A13.70826121132948 83A22.6387581133647 84A396-160123855 O-285A14.83766180012549 86A25.317911101023245 87A31.8092350123652 O-388Flock4.194543121013147 89A12.7284791013052 90A23.2485591012855

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97 APPENDIX C HYDRODYNAMIC DATA Table C-1. Current direction (Dir .) and velocity (V). Coordina tes are in State Plane East (feet, NAD 83) Incoming TideOutgoing Tide IDDir.V(cm/s)X_coordY_coordIDDir.V (cm/s)X_coordY_coord 128017875229.81143329.5116025875232.91143329.4 23309875122.01143374.721705875096.51143388.7 33209875108.91143356.232008875073.91143360.6 42607875102.51143322.241805875062.91143326.7 51802875099.91143288.952007875060.51143295.7 61404875131.81143288.761407875105.11143282.1 726010875137.41143308.571607875119.31143313.2 828025875136.71143330.281407875126.41143342.3 93109875139.91143351.891308875133.61143365.5 1028025875181.71143339.61013020875171.21143340.7 1128025875184.41143325.71110013875172.61143326.5 121404875187.91143313.61210013875175.61143308.6 1332025875226.31143319.5139013875233.81143308.3 1432025875232.01143327.4149020875236.41143320.9 1531017875235.11143335.71510017875237.31143333.7 1631017875261.01143321.11612017875268.21143320.3 1731017875263.91143302.61712014875267.41143297.5 183304875262.91143286.3182208875261.31143269.6 193406875258.51143254.9191406875258.71143242.5 20704875254.81143220.9202306875253.71143203.4 212005875247.01143184.5212202875240.91143169.9 222005875237.51143150.2222206875227.01143141.8 232702875236.71143127.1239010875228.41143123.9 242604875235.31143112.024808875228.71143113.3 252508875235.41143099.525906875229.81143102.6 2627020875205.81143095.326407875197.41143096.8 272706875200.01143106.527607875192.51143103.8 282806875194.51143116.728805875189.01143111.4 2928014875156.81143114.829905875156.01143115.3 302708875156.31143097.1301007875158.61143103.1 313405875162.61143076.731806875160.91143086.8 323003875257.11143103.2321406875156.21143056.9 331603875258.41143119.2331005875138.41143069.7 341703875263.21143144.034803875123.91143092.4 352705875265.61143169.1351009875260.61143107.4

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98 Table C-1 Continued. Incoming TideOutgoing Tide IDDir.V(cm/s)X_coordY_coordIDDir.V (cm/s)X_coordY_coord 362907875268.81143193.7361006875265.91143132.3 3735010875282.01143225.9371703875269.11143157.3 3835014875289.51143258.0382402875275.41143192.7 393308875291.51143277.9392803875285.11143223.8 4032014875297.61143291.240605875294.21143256.6 4132013875304.21143303.94112020875301.71143272.1 423009875332.11143286.54213033875307.71143289.3 433108875333.01143267.04312033875288.31143298.2 443108875337.81143243.2441104875317.81143295.8 4531010875326.61143209.94512033875317.81143283.2 463106875326.41143174.6461409875318.61143260.7 4729013875331.81143151.6471703875319.81143235.2 48604875329.51143136.0482805875308.41143234.2 491204875331.01143123.8492703875314.71143210.5 502705875311.31143137.9502703875312.01143188.7 5136014875359.91143124.5511906875311.71143166.0 523406875366.41143147.1527011875319.81143138.8 532203875369.61143170.4539013875355.41143139.6 542908875372.01143196.9541403875358.71143165.1 552908875380.11143219.1553206875360.81143186.5 5629011875386.21143243.756603875361.01143205.4 572909875389.11143262.2571405875363.31143230.6 582908875391.31143276.35812025875361.01143243.9 592508875414.91143281.45912033875361.91143254.3 6030010875416.91143258.66012020875365.41143264.7 6130011875414.91143227.9611202875403.41143273.8 6228014875413.81143202.86211013875406.61143258.3 632707875412.21143178.66310020875407.31143235.3 641806875411.41143152.36412013875405.71143212.0 65010875379.71143131.9651304875402.51143192.1 66014875386.21143041.1661402875400.81143172.2 672013875386.11143066.8672004875399.61143158.5 682020875380.01143107.2681302875399.41143136.2 693408875372.01143123.069906875431.21143133.6

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99 Table C-1 Continued. Incoming TideOutgoing Tide IDDir.V(cm/s)X_coordY_coordIDDir.V (cm/s)X_coordY_coord 70209875399.71143134.670104875432.51143152.0 713106875670.81143027.0711204875431.61143171.9 7233014875658.91143056.1721408875429.71143193.1 7333025875650.71143088.37314013875428.31143221.0 7434033875640.01143124.57412013875428.71143244.0 75020875638.31143143.3751904875428.51143267.3 7609875867.11143186.37611033875235.61143323.4 7735011875852.31143210.6771204875378.51143025.9 7834020875844.11143253.7781354875377.41143037.0 7933011875805.71143248.5791803875372.41143065.0 80407875817.11143299.1801638875376.31143119.3 813106875773.61143306.6811464875363.41143118.6 823009875774.21143306.9822005875390.51143130.5 8333010875725.91143334.78311511875662.81143023.7 8430013875719.91143385.98413013875670.21143036.8 8529010875700.91143410.38514014875654.81143061.0 8622013875662.81143382.38614513875640.41143089.7 872307875668.61143356.1871159875614.31143113.1 882206875673.51143326.8881658875634.01143132.0 89806875697.91143267.3891509875844.01143182.1 9001875712.11143226.19014517875866.61143190.0 9126014875689.41143197.49114017875842.01143206.6 9201875661.91143222.49214517875818.21143230.4 932105875640.11143264.9931209875806.21143265.6 942304875595.41143299.8941606875805.51143263.5 9523020875540.11143311.1951304875771.81143274.7 962606875554.11143270.5961203875769.11143309.0 972303875567.81143237.4971056875731.41143338.0 9829014875572.11143192.8981204875703.11143353.7 99906875582.81143146.699451875682.71143383.4 10001875592.01143118.8100451875658.81143367.8 1012806875545.61143114.7101451875658.91143338.3 102107875535.41143152.9102451875676.71143309.4 1033006875518.81143196.4103607875693.11143258.2 10427010875501.41143244.7104507875696.31143235.0

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100 Table C-1 Continued. Incoming TideOutgoing Tide IDDir.V(cm/s)X_coordY_coordIDDir.V (cm/s)X_coordY_coord 1052408875496.71143294.5105607875674.11143207.1 10625017875453.11143282.5106609875659.91143233.9 10727017875440.11143242.2107903875629.21143261.3 10826014875438.81143214.6108805875613.71143279.3 1092808875452.41143157.9109905875598.01143312.0 1102206875451.21143157.4110451875575.41143316.7 111706875442.11143128.8111853875581.11143276.6 112513876031.21143515.6112803875596.01143242.3 113608875995.81143516.2113908875611.51143172.4 1147020875948.81143502.71141058875605.01143168.2 1157020875905.31143491.61151056875592.31143132.3 1169010875885.71143498.51161003875561.01143124.7 1175013875880.61143482.81171054875535.61143127.3 118604875886.71143458.5118905875494.91143135.8 1191602875881.61143431.9119904875495.91143169.0 1201653875879.81143405.31201108875496.51143214.1 12128017875878.91143377.3121451875484.91143279.4 12233013875878.91143355.712225528875899.21143482.0 1233003875872.21143336.512318015875998.51143512.3 1241704875869.61143309.01241807875977.61143512.2 1251010875991.21143302.812527017875964.11143500.1 12633017875964.31143315.112630022875944.71143490.1 12730025875933.81143340.812727014875898.91143478.1 12828020875913.11143347.812824017875867.81143461.6 12930020875904.31143360.612915530875867.31143433.3 13030013875899.51143348.313019030875872.61143418.7 1313456875828.31143276.613113517875872.41143387.8 1322453875828.01143311.713212017875878.71143353.8 1333503875823.11143332.41331208875916.51143343.6 1341453875812.61143368.81341408875925.41143332.7 1352152875809.81143405.01351506875947.81143323.8 1361802875795.21143431.71361809875976.91143310.3 137305875828.31143465.91372509875854.21143302.1 13835011875845.11143417.51388527875852.31143336.8 13928017875850.11143382.313911020875846.21143359.6 140604875848.81143350.114016028875840.01143390.3

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101 Table C-1 Continued. Incoming TideOutgoing Tide IDDir.V(cm/s)X_coordY_coordIDDir.V (cm/s)X_coordY_coord 14132014875811.11143282.714120511875837.91143427.3 1421053875794.31143262.114223018875835.41143454.5 14334020875800.61143279.214314554875800.21143459.0 14434033875787.21143316.814416014875797.21143435.5 14535920875783.11143347.114516014875810.61143396.7 14635510875767.21143383.914611029875820.61143350.7 14702875756.61143411.414715521875823.01143320.1 148702875783.21143404.214817018875837.81143319.0 1491102875791.61143370.21496012875856.11143319.4 150502875806.11143348.115021020875834.61143283.3 1513106875812.21143314.015114511875813.41143261.4 1522803875847.91143316.715213022875800.71143254.1 15305875837.41143368.41539011875792.11143278.9 15435014875821.01143428.115420053875791.31143326.9 1551205875861.21143449.21558018875765.01143352.2 1566015875752.21143393.2 1575020875738.31143423.8 1581686876027.51143518.4 1596185876038.41143445.6 1601958876026.01143372.4 1611959876016.71143316.5 16219512875988.91143227.9 16317013875956.81143163.7 1641709875892.91143091.8 16511511875803.91143020.6 16613515875691.01142965.6 16713515875567.61142928.5 1681457875452.01142920.9 16917016875357.21142953.2 17025015875162.81142984.2

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102 APPENDIX D LIGHT AND NUTRIENT DATA 584 13 12 583 14 586 20 587 1 N 100 m 584 13 12 583 14 586 20 587 1 584 13 12 583 14 586 20 587 1 N 100 m Figure D-1. Sampling locations for light attenuation (Kd). The numbers next to each point are the GPS positions (Id).

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103 Table D-1. Light attenu ation coefficients (Kd) for the natural and bay habitats. IdKdX_coordY_coord 30.63876105.4071143552.948 40.53876079.0011143192.066 50.67875721.6401142912.163 60.60874985.7921142940.329 70.65874908.3351143188.545 80.74874867.8461143544.146Natural 90.48874910.0951143790.602 100.40875234.0091143949.038 110.35875821.9831143957.840 5900.43875103.4041143029.091 5910.60875319.7121142975.753 10.38875354.5541143143.109 120.52875925.8461143491.334 130.68875848.3891143394.512 140.70875582.8431143316.109 200.48875500.8021143194.831 5830.75875638.0101143169.283 5840.17875781.1251143365.271Bay 5860.80875720.8441143290.679 5870.56875491.3071143232.874 5870.43875491.3071143232.874 5880.40875320.3601143141.406 5880.68875320.3601143141.406

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104 N 100 m N 100 m Figure D-2. Sampling locations for porewater nutrients in the bay and constructed habitats. Table D-2. Total dissolved Kjeldalh nitr ogen (TDKN) and tota l dissolved phosphorus (TDP) from 0-5 cm porewater samples. GPS #LocationX_coordY_coordTDKNTDP 592bay566777.63230394872.2912.381 593bay566773.61230394672.0911.150 594bay566773.81330394432.4330.119 598bay566846.324303944413.7381.554 599bay566838.03530394620.7480.065 600bay566843.62930394873.0050.143 601bay566878.29130395033.2900.155 602bay566912.71830395193.8900.198 595natural566794.05330393932.2911.098 596natural566819.28830393891.0050.522 597natural566879.06630393910.8340.050 603natural566962.06230394211.2910.519 604natural566962.16830394001.4620.151 605natural566963.27830393880.7200.066

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105 APPENDIX E TRANSPLANT DATA DateTQ1DateTQ2 5/11/06not yet planted5/11/20061169 1387 869 5/26/06 1013155/26/2006543 111310951 171212354 6/26/060007/10/2006040* 0001340* 000932* 8/8/2006080 23140 13912 *shadedDateTQ1DateTQ2 5/11/06not yet planted5/11/20061169 1387 869 5/26/06 1013155/26/2006543 111310951 171212354 6/26/060007/10/2006040* 0001340* 000932* 8/8/2006080 23140 13912 *shaded Figure E-1. Halodule wrightii shoot counts in each transplant quadrat.

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106 DateTQ3DateTQ4 5/11/2006not yet planted 5/11/20069139 121012 71111 5/26/20063245/26/2006131611 117111012 5113101513 6/26/20060007/10/2006880 0005101 00010134 8/8/200612110 363 10133 Figure E-1 Continued.

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107DateTQ5DateTQ6 5/11/2006not yet planted5/11/200661612 131411 61611 5/26/2006119115/26/2006630 101110777 129156311 7/10/200629237/10/2006946 141468710 880869 8/8/200609238/8/2006668 163010677 20230436 Figure E-1 Continued.

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116 BIOGRAPHICAL SKETCH Destined to wear orange and blue, Kelly Compton Fischler was born in Gainesville, Florida, in 1982. Her family is full of Gato rs: her father, Ira, is a University of Florida psychology professor; her mother, Diane, is an editor with UFs Samuel Proctor Oral History Program; and older brot her, Matt, is a UF graduate. Kelly received her B.S. degree in Environm ental Science from UF in 2004. During her undergraduate program, she spent a semester a James Cook University in Townsville, Australia, where she first encountered soil scie nce. Her extracurricu lar activities at UF included playing tuba and baritone in the UF marching, basketball and symphonic bands, as well as competing with the UF racquetball club team. From 2003 to 2005, Kelly worked with Dr. Rex Ellis from whom she gained invaluable field and lab experienceand a love for fishing at the end of a long day of conducting research. Kelly hopes to continue her travels abroad, explore more of the natural world, and pursue a career in natural resource management and/or education.