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Factors Affecting the Maximum Depth of Plant Colonization by Submersed Macrophytes in Florida Lakes

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Title:
Factors Affecting the Maximum Depth of Plant Colonization by Submersed Macrophytes in Florida Lakes
Copyright Date:
2008

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Subjects / Keywords:
Attenuation coefficients ( jstor )
Bodies of water ( jstor )
Chlorophylls ( jstor )
Colors ( jstor )
Highlands ( jstor )
Lakes ( jstor )
Light water ( jstor )
Macrophytes ( jstor )
Mathematical maxima ( jstor )
Orange fruits ( jstor )
Alachua County ( local )

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University of Florida
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University of Florida
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Embargo Date:
8/31/2006

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FACTORS AFFECTING THE MAXIMUM DEPTH OF COLONIZATION BY
SUBMERSED MACROPHYTES IN FLORIDA LAKES















By

ALEXIS JORDAN CAFFREY


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

Alexis Jordan Caffrey















ACKNOWLEDGMENTS

Gratitude is expressed to the many people who helped me carry out this project.

Special thanks are given to Mark Hoyer who helped me with my project in ways too

numerous to list. Julie Terrell assisted in providing the Florida LAKEWATCH data.

Claude Brown and Eric Schultz provided immeasurable professional advice as well as

many long days out in the field helping with field sampling. Appreciation is granted to

David Watson and Dan Willis for providing directions to many of the sampled lakes.

Appreciation is expressed to Dr. Roger Bachmann, a brilliant limnologist, for guiding me

in analyzing my light readings. Thanks are given to Dr. Daniel E. Canfield, Jr., for

funding the project and serving as my committee chairman and advisor. Gratitude is

expressed to Dr. Charles E. Cichra for serving as my committee cochair and for offering

encouragement and guidance. Finally, Dr. Kenneth Langeland served on my committee

and helped oversee the project.
















TABLE OF CONTENTS



A C K N O W L E D G M E N T S ......... ................................................................................... iii

LIST OF TABLES ........ .............. ........ ..................... .... ............... v

LIST OF FIGURES ......... ....... .................... .......... ....... ............ vi

ABSTRACT ........ .............. ............. ........ ..................... vii

CHAPTER

1 IN TR O D U C TIO N ......................................................................... .... .. ........

2 M A TERIALS AND M ETH OD S ............................................. .......................... 3

3 RESULTS AND D ISCU SSION ........................................... ............................10

4 C O N C L U SIO N .......... ......................................................................... ............ .. 2 1

APPENDIX

A 32-LAKE STUDY DATA .......................................................... ............... 24

B 279-LAK E-YEAR STUD Y ................................................ .............................. 30

L IST O F R E FE R E N C E S ............................................................................. .............. 37

B IO G R A PH IC A L SK E TCH ...................................................................... ..................40















LIST OF TABLES


Table p


3-1 Descriptive statistics for the maximum depth of plant colonization (MDC in
m eter), Secchi disk ....... ....... .......................... ... ....................................... 16

3-2 Multiple regression equations relating Secchi disk (SD in meters), light
attenuation coefficient. ............................................... .. ........ .. ...... ............18

3-3 Mean maximum depth of plant colonization (MDC in meters) and slope values
by lake and the relationship between M DC .................................. ............... 19

3-4 Descriptive statistics for maximum depth of plant colonization (MDC in
m eters), Secchi disk......... ....... ................. ........... ............... 20

3-5 Regression equations of the maximum depth of submersed plant colonization. .....20

A-i Maximum depth of plant colonization (MDC in meters), Secchi disk
transparency (SD in meters) ....... .................... .......... ..... 25

B-1 Maximum depth of plant colonization (MDC in meters), yearly mean Secchi
d isk tran sp aren cy ............ ............................................................... 3 0















LIST OF FIGURES


Figure pge

2-1 Locations of lakes sam pled for both studies. ........................................ .................9

3-1 Relationship between the mean maximum depth of submersed macrophyte
colonization and mean Secchi disc depth (A) and mean light attenuation (B). .......17

3-2 Relationships between mean Secchi disc depth and mean light attenuation (A,
B). ...................... ....................................... 18

3-3 Comparison of a calculated maximum line to the best-fit line relating yearly
Secchi disk depth to the maximum depth of plant colonization. ...........................20















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 THE MAXIMUM DEPTH OF COLONIZATION BY
SUBMERSED MACROPHYTES IN FLORIDA LAKES

By

Alexis Jordan Caffrey

August 2006

Chair: Daniel E. Canfield, Jr.
Cochair: Charles E. Cichra
Major Department: Fisheries and Aquatic Sciences

In 32 Florida lakes, Secchi disk (SD) transparency, light attenuation coefficient

values, plant and sediment type, and slope were examined with respect to the maximum

depth of plant colonization (MDC). In the 32-lake study, MDC was shown to be

significantly related to light through measurements taken by a SD (R2 = 0.46; p < 0.0001)

and a light meter (R2= 0.41; p < 0.0001). There was no significant difference in the

mean percent of light penetration at MDC stations between hydrilla (Hydrilla verticillata

Royle) and non-hydrilla species (p = 0.2), and furthermore, between angiosperms and

charophytes (p = 0.4). Similarly, organic, sandy, and mixed sediment types were not

shown to exert a significant influence (p = 0.07) on the depth of aquatic plant

colonization. Lake bottom slope was not shown to be significantly related (R2 = 0.03; p =

0.35) to the maximum depth of plant growth.

To increase the sample size, SD transparency, color, chlorophyll, and water column

nutrients (total phosphorus and total nitrogen) were examined with respect to the









maximum depth of macrophyte growth for 279-lake-years of information. An upper limit

line relating MDC to SD in meters was calculated and was found to be equal to: log (max

MDC) = 0.52 log (SD) + 0.59. The maximum MDC line describes light limitation when

the MDC response fall on or near the response curve and when MDC values fall below

the line, there is some other limiting environmental factor. For the 279-lake-year study,

the maximum depth of aquatic plant growth was significantly related to Secchi disk

transparency (R2= 0.67; p < 0.0001), color (R2 = 0.41; p < 0.0001), chlorophyll (R2

0.30; p < 0.0001), total phosphorus (R2 = 0.42; p < 0.0001), and total nitrogen (R2 = 0.33;

p < 0.0001).














CHAPTER 1
INTRODUCTION

The distribution and abundance of aquatic macrophytes in lakes are affected by

many forces including but not limited to pressure (Hutchinson 1975), substrate

characteristics (Bachmann et al. 2001) and lake morphology (Duarte and Kalff 1986),

water column nutrient concentrations (Jupp and Spence 1977), waterfowl grazing

(Weisner et al. 1997), and light availability (Chambers and Kalff 1985; Canfield et al.

1985). Given the high attenuation of irradiance through the water column, and because

plants require light to photosynthesize, it is not surprising that light availability is often

considered one of the most important factors that regulate abundance and distribution of

aquatic macrophytes (Zimmerman et al. 1994).

The maximum depth at which autotrophic aquatic plants grow has been shown to

be linearly related to transparency of the water in numerous studies (Maristo 1941;

Canfield et al.1985; Hudon et al. 2000). Chambers & Kalff (1985) found the maximum

depth of colonization (MDC) for charophytes on average to occur at 11% of the surface

incident irradiance. For angiosperms and bryophytes, they found MDC to be 21% of the

surface irradiance. However, aquatic plants have been recorded in areas receiving less

than 1 and 2% of the surface irradiance (Hutchinson 1975).

Canfield et al. (1985) demonstrated a relationship between water transparency as

measured by a Secchi disc (SD) and the maximum depth of macrophyte colonization in

26 Florida lakes. They also developed an empirical model for the relationship and

suggested the model could provide lake managers with a first approximation of how









changes in SD values caused by either natural or anthropogenic activities might affect the

extent of macrophyte colonization in lakes. However, they cautioned lake mangers that,

in using the model, other environmental factors (e.g., types of plants present, basin

morphometry, sediment types) besides SD values need to be considered to enhance the

predictive ability of the model.

In the 1990s, the Florida Legislature directed the state's water management districts

to establish minimum water levels for lakes (Section 373.042, Florida Statutes). The

Southwest Florida Water Management District (SWFWMD) developed methods for

establishing minimum lake levels (Chapter 40D-8. Florida Administrative Code), which

included use of the model developed by Canfield et al. (1985) to assess potential changes

in the coverage of submersed vegetation with changes in water transparency. The

Southwest Florida Water Management District, however, recognized the need to try to

develop a more robust model from a larger number of lakes.

This study was designed based on the earlier work of Canfield et al. (1985) in an

attempt to develop more robust model/models for use by SWFWMD. The first part of

the study involved the sampling of 32 Florida lakes. At each lake, environmental factors

such as water chemistry, photosynthetically active radiation (PAR), and bottom slopes

were measured to determine if the maximum depth of macrophyte colonization could be

better predicted than relying solely on SD transparency. The second phase of this study

used information collected by Florida LAKEWATCH on a large number of Florida lakes

to develop a series of models to predict the maximum depth of colonization of

macrophytes and establish a model where the maximum depth of macrophyte

colonization in Florida lakes should be limited by light.














CHAPTER 2
MATERIALS AND METHODS

Two data sets were used for model development. The first part of the study

involved field sampling of 32 Florida lakes using the basic approach of Canfield et al.

(1985). Study lakes selected were located in eight counties, with the majority located in

peninsular Florida (Figure 2-1). Lakes located in the SWFWMD comprised 38% of the

sampled lakes. Each lake was sampled once between May and December of 2004.

At each study lake, four straight transects were established to provide an

assessment of macrophyte coverage. A Raytheon DE-719 fathometer was used to detect

the MDC for the macrophyte community along each transect. Buoys were placed at

locations of measured macrophyte MDC. After all transects were completed, the three to

four deepest buoy stations were checked with a toothed hook (18 cm by 18 cm) for the

presence of submersed aquatic macrophytes.

At stations where the MDC was identified, measurements were made for SD

transparency, light attenuation (E), true color, sediment type, and bottom slope, and the

plant species were identified. In some lakes with sparse plant growth, fewer than three

stations were found harboring submersed aquatic macrophytes. At these lakes, open

water stations were sampled for SD transparency, light attenuation (E), true color, and

sediment type. The variables that had quantitative values (i.e., SD transparency, E, color,

and slope) were averaged by lake for the day sampled, and because lakes were visited

only once during the study, each lake is considered the experimental unit for the

quantitative variables. On the other hand, the experimental unit for qualitative variables,









such as plant type [i.e., the inclusion or exclusion of the plants being a hydrilla (Hydrilla

verticillata Royle) versus non-hydrilla species and being an angiosperm versus a

charophyte] or sediment type (i.e., organic, sandy, mixed) was considered to be the lake

stations.

At each of the 32 study lakes, water transparency was measured where the MDC

occurred by the use of a Secchi disc on the shady side of the boat. If the Secchi disc was

visible on the bottom for all three stations, an additional Secchi reading was taken in a

deeper location to use for analysis. Surface and corresponding underwater light

irradiance were measured (in quanta units) on the sunny side of the boat using a

photometer (LI-COR model LI-1400 data logger) with a quantum sensor that was placed

both above (LiCor 193) and below (LiCor 192) the water. Light meter readings were

taken at two to three depths. If possible, light measurements at each station were made at

depths of one, two, and three meters to better represent light attenuation for the entire

water column. An additional open-water light reading was taken in deeper water at some

lakes where all three stations were shallow (less than 3 meters) or when sun coverage was

fading and no stations had yet been sampled for light. Light readings were averaged over

ten seconds to mitigate instantaneous fluctuations with light intensity. The downward

attenuation coefficient values for each station were calculated as the slope of the graph of

the natural logarithm of the irradiance values, corrected for changes in incident irradiance

on the y-axis, against depth on the x-axis (Lind 1974). The percent of surface irradiance

penetrating at MDC was calculated using the relationship: Iz/ Io = 100eEz, where Iz/ Io =

percent of subsurface irradiance, E = light attenuation coefficient and z = the maximum

depth of plant colonization (Scheffer 1998).









Color samples were collected at the surface (0.5 m) with 250-mL, acid cleaned,

triple-rinsed, Nalgene bottles and immediately placed on ice until they could be put in a

freezer to await analysis. True color values were determined following filtration through

a Gelman type A/E glass fiber filter, centrifugation of the filtrate, and using the platinum-

cobalt standard technique determined by spectroscopy (Bowling et al. 1986).

A ponar dredge with a 15 cm opening was used to obtain soil samples. Sediment

type was classified as one of three types: sandy, organic, or mixed. Soil samples that

were dark colored and slippery to the touch were classified as organic while white,

granular soil samples were classified as sandy, and a blend of organic and sandy soil was

categorized as a mixed soil.

Bottom slope was calculated around MDC stations and not the entire littoral area.

Slope was calculated from the Raytheon DE-719 fathometer chart by dividing the rise

(the change in water depth) by the horizontal distance across the station.

For the 32-lake study, regression equations and coefficient of determination values

(R2) were calculated using SD and E readings as the independent variables in order to

predict the maximum depth of submersed macrophyte colonization. Multiple regression

analysis was used to relate SD, E, and MDC to color and chlorophyll. Chlorophyll

concentrations were obtained from the Florida LAKEWATCH database. Best fit linear

regressions were calculated between SD and E and vise versa. A t-test was used to test

whether there was a significant difference in the average percent of incident light at the

maximum depth of colonization between stations with hydrilla versus non-hydrilla and

between stations harboring angiosperms versus charophytes. To investigate soil

influence on MDC, an ANOVA was used to test for differences in the mean depth of









plant growth for the three soil types. Also, the coefficient of determination was

calculated for the relationship between slope and MDC (McClave and Sincich 2000).

The statistical software package JMP version 4.0 was used for statistical analysis and

Kaleidagraph version 3.6 was used to generate linear regression figures.

The second part of this study involved obtaining information on 187 lakes which

had their macrophyte communities sampled by Florida LAKEWATCH. The lakes were

sampled between 1991 and 2004. The water chemisty data were represented as yearly

averages and although most lakes were sampled only once, some lakes were sampled

multiple times providing 279-lake-years of information. Florida LAKEWATCH is a

volunteer citizens' lake monitoring program in which volunteers take measurements at

three mid-lake locations, usually on a monthly basis, for total phosphorus (TP), total

nitrogen (TN), chlorophyll, and SD transparency. The 187 lakes were located in 24

counties (Figure 2-1) and 35% of the lakes were in the SWFWMD.

For the 279-lake-year study, Florida LAKEWATCH provided 250 Raytheon DE-

719 fathometer chart papers that were later examined for the maximum point of plant

colonization. The 32-lake study provided an additional 29 Raytheon DE-719 fathometer

chart papers.

Secchi disk readings and true color samples were obtained using the same

procedures as the 32-lake study. Surface (0.5 m) water samples for measuring

chlorophyll were collected in 4-L, tap-water rinsed, plastic milk jugs and placed in

coolers until the samples could be filtered. A measured volume of water was filtered

through a Gelman Type A-E glass fiber filter. Filters where folded and placed inside a

larger paper filter and then stored inside a silica gel desiccant bottle in a freezer.









Chlorophyll was extracted from the filters in hot ethanol (Sartory and Grobbelarr 1984).

The trichromatic equation for chlorophyll a was used to calculate the concentrations of

chlorophyll with the hot ethanol method (Method 10200H; APHA 1992).

Water samples for TP and TN were collected at the surface (0.5 m) with 250-mL,

acid cleaned, triple-rinsed, Nalgene bottles. Water samples were immediately placed and

held on ice until returned at the end of the sampling day to the Florida LAKEWATCH

water quality laboratory in Gainesville, Florida. At the laboratory, water samples were

frozen until being analyzed by Florida LAKEWATCH staff. Total phosphorus

concentrations were determined using the methods of Murphy and Riley (1962) with a

persulfate digestion (Menzel and Corwin 1965). Total nitrogen concentrations where

determined by the oxidization of water samples using persulfate and determining nitrate-

nitrogen with second derivative spectroscopy (D'Elia et al. 1977).

Data (i.e., SD transparency, color, chlorophyll, TP, and TN) obtained from Florida

LAKEWATCH were averaged for the year in which plants were inventoried at each lake.

For each lake, Florida LAKEWATCH means were first averaged for the day of the

month sampled and these monthly means were averaged together for a yearly mean for

the lake. Some lakes were represented in the data set more than once if they were

sampled multiple years.

If Florida LAKEWATCH was missing water chemistry data for the corresponding

year that the lake was measured for MDC, long-term water chemistry means for that lake

were used. Long-term means were computed by averaging all yearly means for a lake.

For the 279-lake-year study, long-term values used represented 5% of SD transparency

readings, 43% of color measurements, and 2.5% of chlorophyll, TP, TN values.









An empirical model was developed using the Florida LAKEWATCH database

relating SD transparency to the maximum depth of submersed vegetation in order to

increase the representation of Florida lakes. A maximum line relating MDC and SD was

also determined by sorting the 279 SD values from lowest to highest and then dividing

these into 10 groups. Because 279 is not divisible by 10, there were 28 SD values in each

of the first nine groups, and one group of 27 SD readings. The maximum MDC value in

each group with its associated SD value was used to run a regression through the 10 pairs

of points. Linear and multiple regression models were created to quantify the

relationship of MDC to color and chlorophyll because these two light-reducing variables

have been shown to be hyperbolically related to SD depth (Canfield and Hodgson 1983).

Furthermore, because TP and TN have been shown to be positively related to chlorophyll

concentrations (Canfield 1983), these nutrients were also examined mathematically with

respect to the maximum depth of submersed plant colonization. To meet the assumption

of normality, prior to statistical analysis, all distributions were transformed to a base 10

logarithm. A software program, Kaleidagraph version 3.6, was used to generate figures

and JMP version 4.0 was used to perform statistical tests. The alpha level of rejection

was set at 0.05.













30




29




28-



27-




26- 0 187-lake study

t 32-lake study


25-


-87 -86 -85 -84 -8

Longitude

Figure 2-1. Locations of lakes sampled for both studies.














CHAPTER 3
RESULTS AND DISCUSSION

Canfield et al. (1985) sampled 26 Florida lakes with SD transparencies ranging

from approximately 1 m to about 6.3 m. For the 32-lake study, there was a wide range in

SD transparency from 0.3 m to 5.8 m. The mean transparency for all lakes was 1.8 m.

The other measured limnological parameters in the 32-lake study also varied

considerably. Measured light extinction coefficients ranged from 0.2 m1 to 6.8 m-1

(mean for all lakes 1.8 m-1). True color ranged from 2 PCU to 385 PCU (mean color 50

PCU). The calculated bottom slopes ranged from 0.3% to 13% (mean slope 4%). The

maximum depth of plant colonization ranged from 0.7 m to 9.2 m, with mean depth of

aquatic macrophyte growth at 3.1 m (Table 3-1).

Canfield et al. (1985) found a significant positive relationship between the MDC

and SD depth (R2 = 0.49) using data from Finnish, Florida, and Wisconsin lakes. For the

32 Florida lakes sampled during this study, there was also a significant positive

relationship between the MDC and SD depth (R2= 0.46; p < 0.0001; Figure 3-1A). The

best fit equation between MDC and SD for the Canfield et al. 1985 study was:

log ( MDC ) = 0.61 log ( SD ) + 0.26 (3-1)

The equation between MDC and SD for the 32 Florida lakes was:

log (MDC ) = 0.64 log ( SD ) + 0.30 (3-2)

where MDC and SD are expressed in meters. Both equations are similar and provide

evidence that the positive relationship between MDC and SD is repeatable.









Canfield et al. (1985) found light meter readings were highly correlated (r = 0.96)

to concurrently measured SD values. Most light reaching the water surface is reflected,

turned to heat, or absorbed by objects in the water column as well as by the water itself

(Cole 1983). The intensity of light in the water column (Iz) decreases exponentially with

depth (z) depending on the vertical attenuation coefficient (E) of the water and the

starting surface illumination (Io), using the relationship set forth in Beers law: Iz = Io e-Ez

(Scheffer 1998). Wavelengths are absorbed differentially in the water column with

infrared light and many of the visible reds being absorbed mostly in the first meter and

with blues penetrating the deepest (Cole 1983). Additional substances in the water---

dissolved organic (color), algae, and non-algal suspended solids---influence the amount

of light penetration through the water column (Havens 2003), and potential SD values.

Light availability to a depth in the water column can be measured directly by the

use of a light meter or indirectly by the use of a SD. For the English Channel, the

relationship between light attenuation (E) and SD measurements was E =1.7 / SD (Poole

and Atkins 1929). However, the relationship between E and SD varies among studies

and many alternatives have been suggested (Holmes 1970; Walker 1980). For the 32

study lakes, the correlation between the measured light attenuation coefficients and SD

was significant, but not as strong (r = 0.81) as that reported (r = 0.96) by Canfield et al.

(1985). Color and chlorophyll concentrations were also highly related to SD depth (R2

0.71; p < 0.0001), light attenuation (R2 = 0.74; p < 0.0001), and MDC (R2= 0.65; p <

0.0001) through multiple regression analysis (Table 3-2). Secchi disk transparency,

however, can be predicted reasonably well from measured light attenuation coefficients

(Figure 3-2A) using the equation:









log ( SD )= -0.69 log ( E )+ 0.26 (3-3)

and light attenuation coefficient (E) can be predicted from SD (Figure 3-2B) using the

equation:

log (E)= -0.96 log ( SD)+ 0.30 (3-4)

where SD is in meters and E is per meter.

Although E and SD are highly correlated, the large 95% confidence limit (46-

236%) associated with the MDC-SD model published by Canfield et al. (1985) has lead

to speculation that the use of light meter readings could lead to the development of a

more robust model. The MDC of macrophytes in the 32-lake study was negatively

related to the mean light attenuation coefficient (Figure 3-1B) and the relationship was

represented by the following equation:

log (MDC)= -0.51 log (E)+ 0.48 (3-5)

where MDC is in meters and E is per meter. Light attenuation, however, did not predict

MDC any better than SD transparency and actually had a slightly lower coefficient of

determination (R2 = 0.41) than SD readings (R2 = 0.46). This finding demonstrated SD,

an easily measured and inexpensive index of water transparency, is as useful for

assessing MDC as E values that require the use of complex and expensive equipment.

Canfield et al. (1985) suggested the major factor contributing to the variability in

the MDC-Secchi relationship is the type of plant colonizing the lake bottom because

different species of plants have different light requirements. The amount of surface light

penetrating at the maximum depth at which submersed aquatic macrophytes colonized in

the 32 study lakes ranged from < 1% to 47%. The mean percent of incident light at the

maximum depth of colonization was 11%, which was in agreement with much of the









literature (Table 3-1). For example, Hoyer et al. (2004) found that when the percent of

incident light at the surface reaching the substrate was less than 10%, there was little or

no submersed aquatic vegetation biomass. Sheldon and Boylen (1977) found the MDC to

correspond to 10% of the light intensity hitting the surface. The mean percent of incident

light at the maximum depth of colonization for stations with hydrilla, non-hydrilla,

angiosperms, and charophytes present in this study was 19%, 10%, 12%, and 7%,

respectively (Table 3-1). Although hydrilla has been shown to have low light

requirements in laboratory conditions (Van et al. 1976), for the 32 lakes examined in

natural conditions, hydrilla was not found at low light levels. There was no significant

difference in percent of incident light at the maximum depth of colonization between

hydrilla and non-hydrilla species (p = 0.2). Similarly, there was no significant difference

of mean percent surface penetration present at the depth of maximum plant growth

between angiosperms and charophytes (p = 0.4). This indicates that for this group of

Florida lakes, differences in the light requirements of individual plant types can not be

invoked as the major factor contributing to the variability in the MDC-Secchi

relationship.

Lake bottom sediment serves not only as a physical anchor for submersed

vegetation but also as a source of nutrients (Barko et al. 1991). Bachmann et al. (2001)

suggested the flocculent organic sediments in Lake Apopka were deleterious for root

anchorage and limited the colonization of submersed aquatic macrophytes. Lake Apopka

sediments, however, are unique and the lake was not included in the 32-lake study. For

the 32-lake study, the mean MDC for organic, mixed, and sandy soils were 2.9 m, 3.7 m,

and 2.7 m, respectively. There was no significant difference in the maximum depth of









plant colonization among the three soil types classifications established in this study (p =

0.07). Soil type, therefore, was not shown to have a significant effect on the maximum

depth of plant growth. However, the means were close to be significantly different with

the mixed soil having the largest mean MDC, suggesting that mixed soil tends to promote

plant growth in deeper waters.

As early as 1924, H. W. Rickett noticed that aquatic vegetation grew deeper in

lakes possessing gentle slopes and shallower in lakes having steeper slopes. Duarte and

Kalff (1986) demonstrated a strong influence of littoral bottom slope on the maximum

biomass of aquatic macrophyte communities. However, they pointed out that the model

generated in their study did not reflect turbid lakes (i.e., Secchi disk readings < 2 m),

where irradiance rather than slope is pre-eminent. The mean SD transparency for the 32

lakes was 1.8 m; therefore littoral bottom slope according to Duarte and Kalff (1986)

should not greatly influence MDC in Florida lakes. In another study by Duarte and Kalff

(1990), they found that 15% was the steepest slope at which aquatic macrophytes were

present and able to grow. All of the lakes in the 32-lake study had slopes less than 15%.

Lake bottom slope was not significantly related to the maximum depth of submersed

plant colonization (R2 = 0.03; p = 0.35; Table 3-3) so slope is not a variable that can be

used to improve the MDC-Secchi relationship in Florida. Although slope has been found

to affect aquatic plant growth in other studies, it seems plausible that slope has a minimal

influence on MDC for many of Florida lakes because they are generally shallow, with a

majority of them having mean depths less than 5 meters (Florida LAKEWATCH 2003).

Florida lakes display a wide range of limnological conditions (Canfield and Hoyer

1988). Information on MDC, SD, and other water chemistries were obtained from









Florida LAKEWATCH to examine the MDC-Secchi relationship for a wide range of

lakes. For the 279-lake-year study, MDC ranged from 0.7 m to 9.2 m. The mean MDC

depth was 3.3 m. Secchi disk transparency ranged from 0.2 m to 8.2 m (mean of 2.2 m).

Color values ranged from 0 PCU to 430 PCU, with the mean color for all lakes equal to

50 PCU. The minimum and maximum chlorophyll concentrations were 0.5 tg/L and 292

[tg/L, respectively, and the overall mean was 17 [tg/L. Total phosphorus and TN

concentrations ranged from 2.1 tg/L to 402 tg/L and 43 tg/L and 4550 [tg/L,

respectively, and averaged 28 [tg/L and 764 [tg/L, respectively (Table 3-4).

For the 279-lake-year study, there was as significant positive relationship between

SD and MDC (R2 = 0.67; p < 0.0001; Figure 3-3). The best fit MDC-SD regression line

was:

log (MDC)= 0.66 log ( SD) + 0.30 (3-6)

where MDC and SD are expressed in meters. Equation 3-6 is essentially the same as the

regression equations developed by Canfield et al. (1985) (Equation 3-1) and by my 32-

lake study (Equation 3-2). This strongly suggests the MDC-SD relationship is applicable

to a wide range of lakes.

Inspection of Figure 3-3 clearly shows that for a given SD there is considerable

variability in the measured maximum depth of macrophyte colonization. This is evidence

that other environmental factors besides water transparency influence MDC. However,

there is a clear upper limit for MDC at various SD levels. This upper limit represents

where light is the limiting environmental factor and can be described by the following

equation:

log (max MDC ) = 0.52 log ( SD ) + 0.59 (3-7)









where MDC and SD are expressed in meters. When MDC values falls below the line,

there is some other limiting environmental factor other than solely light that is inhibiting

plant growth.

Because SD readings were related to the measured color (R2 = 0.49) and

chlorophyll samples (R2= 0.59), these two light reducing variables were quantifiably

related to the maximum depth of submersed plant colonization. Moreover, because

chlorophyll readings were related to TP (R2 = 0.69) and TN (R2 = 0.53), regression

models were developed to relate these nutrients to the maximum depth of submersed

macrophyte colonization. Therefore, the depth at which plants colonized was also

significantly inversely related to color (R2= 0.41; p < 0.0001), chlorophyll (R2= 0.30; p <

0.0001), TP (R2 = 0.42; p < 0.0001), and TN (R= 0.33; p < 0.0001). The light

attenuating substances, color and chlorophyll, were inversely related to MDC through

multiple regression analysis (R2= 0.52; p < 0.0001). Given the significant relationships

between MDC and color, chlorophyll, TP, and TN, it is possible to provide a basic

assessment of the potential effects of these variables on macrophyte colonization in

Florida lakes even without measurements of SD or E.

Table 3-1. Descriptive statistics for the maximum depth of plant colonization (MDC in
meters), Secchi disk (SD in meters), light attenuation coefficient (E in m-1),
percent of subsurface irradiance penetration (Iz / Io in %), color (PCU), and
slope (%) for the 32-lake study.
Parameter n Minimum Maximum Mean Standard
deviation
MDC 32 0.7 9.2 3.1 1.8
SD 32 0.3 5.8 1.8 1.2
E 32 0.2 6.8 1.8 1.5
Color 32 2 385 50 70
Iz/Io 32 0.008 47 11 14
Iz/Io hydrilla 9 0.43 99 19 33
Iz/ Io Non-hydrilla 72 0.0003 78 10 16
Iz/Io Angiosperm 68 0.0003 99 12 20
Iz/Io Charophyte 13 0.02 19 7 6
Slope 31 0.3 13 4 3




































Secchi Disc (m)


Light Attenuation Coefficient (-m)

Relationship between the mean maximum depth of submersed macrophyte
colonization and mean Secchi disc depth (A) and mean light attenuation (B).


I o

0 O00
0 0 O0




00 0
0
O O

log [MDC) = 0.64 log [SD) + 0.30
R = 0.46
n= 32
p< 0.0001 A
I


0 I


00





0 0
0 0 0 0 0


O0)
0 0


log [MDC = -0.51 log (E) + 0.48
R =0.41
n= 32
p < 0.0001 B
I


Figure 3-1.







18


Table 3-2. Multiple regression equations relating Secchi disk (SD in meters), light
attenuation coefficient (E in m-1) and the maximum depth of plant
colonization (MDC in meters) to color (PCU) and chlorophyll (CHL in tg/L).
n Equation R2 p value
29 log(SD) = -0.25 log(COLOR) 0.39 log(CHL) + 0.88 0.71 < 0.0001
29 log(E) = 0.52 log(COLOR) + 0.22 log(CHL) 0.82 0.74 < 0.0001
29 log(MDC) = -0.27 log(COLOR) -0.35 log(CHL) + 1.11 0.65 < 0.0001


Light Attenuation Coefficient (-m)


Figure 3-2.


Secchi Disk (m)
Relationships between mean Secchi disc depth and mean light attenuation
(A, B).


0





0
^0

1 00



log (SD) = -0.69 log (E + 0.26
2 0
R = 0.66
n= 32
p < 0.0001 A


0

0 0

0
r- 0


0 0


log (E = -0.96 log (SD) + 0.30 0
R= 0.66 O
n= 32 B
p < 0.0001
I









Table 3-3. Mean maximum depth of plant colonization (MDC in meters) and slope
values by lake and the relationship between MDC and mean slope.
Lake County MDC Slope
Alligator Lake 2.6 0.04
Alto Alachua 2.5 0.02
Bay Marion 1.97 0.02
Beakman Lake 3.4 0.01
Bellamy Citrus 0.72 0.04
Brant Hillsborough 1 0.03
Church Hillsborough 2 0.06
Conway North Orange 5.5 0.05
Conway South Orange 5.83 0.04
Dodd Citrus 1.03 0.10
Doe Marion 4.23 0.03
Farles Prairie Lake 4.57 0.05
Grasshopper Lake 2.25 0.02
Hampton Bradford 1.73 0.01
Hernando Citrus 2.27 0.03
Ivanhoe East Orange 2.17 0.07
Little Conway Orange 5.57 0.03
Little Santa Fe Alachua 2 0.01
Magdalene Hillsborough 3.57 0.02
Maurine Hillsborough 1.2 0.04
Melrose Bay Alachua 2.87 0.07
Mill Dam Marion 2.73 0.03
Newnan Alachua 0.65 0.003
Osceola Hillsborough 3.5 0.07
Santa Fe Alachua 3.87 0.02
Sellers Lake 9.2
Starke Orange 1.5 0.13
Stella Putnam 4.27 0.03
Taylor Hillsborough 3.1 0.03
Twin Hillsborough 2.65 0.05
Weir Marion 3 0.01
White Trout Hillsborough 4.8 0.07
Note: n = 31, R2 = 0.03, p value = 0.35.










Table 3-4. Descriptive statistics for maximum depth of plant colonization (MDC in
meters), Secchi disk (SD in meters), color (PCU), chlorophyll (pg/L), total
phosphorus (TP in pg/L), and total nitrogen (TN in pg/L).
Parameter n Minimum Maximum Mean Standard


MDC
SD
Color
Chlorophyll
TP
TN


ie
r-
0


0

4-
0

0

a.



E
E




Figure 3-3.


9.2
8.2
430
292
402
4550


3.3
2.2
50
17
28
764


deviation
1.9
1.5
69
34
40.5
601.2


Yearly Secchi Disk
Yearly Secchi Disk (m)


Comparison of a calculated maximum line to the best-fit line relating yearly
Secchi disk depth to the maximum depth of plant colonization.


Table 3-5. Regression equations of the maximum depth of submersed plant colonization
(MDC in meters) related to color (PCU), chlorophyll (CHL in gg/L), total
phosphorus (TP in ig/L), and total nitrogen (TN in ig/L).
Input n Equation R p value


log(MDC) = 0.66 log(SD) + 0.30
log(MDC) = -0.29 log(COLOR) + 0.85
log(MDC) = -0.28 log(CHL) + 0.71
log(MDC) = -0.43 log(TP) + 0.99
log(MDC) = -0.48 log(TN) + 1.79
log(MDC) = -0.22 log(COLOR) 0.18
log(CHL) + 0.93


0.67 < 0.0001


0.41
0.30
0.42
0.33
0.52


< 0.0001
< 0.0001
< 0.0001
< 0.0001
< 0.0001


variable
SD
COLOR
CHL
TP
TN
COLOR &
CHL


279
262
279
279
279
262














CHAPTER 4
CONCLUSION

For this study, the maximum depth inhabited by an angiosperm was found at 9.2 m.

This was similar to the comments of Hutchinson (1975), which concluded that, in lakes,

most angiosperms are limited to depths of 9 m. There have, however, been a few

exceptions of extreme deep water expansion by freshwater angiosperms. For example,

Sheldon and Boylen (1977) found Elodea canadensis growing to depths of 12 m in Lake

George, New York and Hydrilla verticillata has been found growing to a depth of 15 m

in Crystal River (Langeland 1996).

This study has confirmed the findings of Canfield et al. (1985) that the maximum

depth of macrophyte colonization can be predicted using SD transparency. Furthermore,

the maximum depth of plant growth can be predicted reasonably well by light meter

measurements. The mean percent of incident light at the maximum depth of plant

colonization was 11% for the Florida lakes studied, which was in agreement with much

of the primary literature. Although plant species, sediment type and slope have been

shown to influence aquatic plant growth on an individual lake basis, no significant

influences on MDC were found in this study when looking among lakes. When those

variables (plant species, sediment types, slope) where taken into account, they did not

increase the predictive capabilities of the Canfield et al. SD-MDC model.

Although this study represents a more comprehensive research effort than those of

Canfield et al (1985) to identify and quantify the environmental determinants of MDC,

the findings, nevertheless, offer no improvement on the predictive value offered by the









SD measurements reported in that study. This suggests that light attenuation, as

quantified by SD sampling, is the most important environmental factor in determining

MDC. Still, there is substantial variability in SD-MDC correlates from one site to

another, suggesting that other factors play a causal role.

It is possible that much of the variability in the MDC-SD model is due to

fluctuations in lakes levels that prevent plant depth from attaining a state of equilibrium.

Furthermore, light regimes fluctuate through time causing oscillation in the equilibrium

depth at which plants grow. For the 279-lake-year study, the use of yearly average SD

readings helped account for the changing light regimes in which the plants had been

growing and to which they were responding that year, whereas only daily SD readings

were used in the 32-lake study. It is significant, therefore, that if yearly SD transparency

values from the Florida LAKEWATCH database were used to replace the daily SD

values for the 32-lake study, the yearly SD-MDC model accounts for more variablility

(R2 = 0.57) than the one using the daily SD values (R2 = 0.46).

Obviously, when herbicides are used or when grass carp are released into a lake,

the depth of plant growth should diminish and could cause lakes to deviate below the best

fit SD-MDC line. When the Hernando Chain of Lakes in Citrus County was visited

during the 32-lake study, the water was being sprayed with a herbicide and an island was

being built. Many of the areas visited in this chain had the presence of freshly killed

plant material, indicative of continued plant maintenance control.

There are innumerable possible combinations of environmental variables for a

specific site over the course of time and this introduces the element of unquantifiable

chance into any predictive value for response by a resident organism. The inability of









this current research effort to isolate other specific factors as core determinants makes it

seem likely that the range of variation in MDC response from site to site is to be

expected. In the final analysis, this simply represents a measurable variation in response

to an immeasurably complex interaction of environmental factors

An upper limit line relating MDC to SD was developed and describes light

limitation when the MDC response falls on or near the response curve and when MDC

values fall below the line, there is some other limiting environmental factor. Managers

should recognize that the maximum MDC model predicts the upper limit of deepwater

growth, but other factors will routinely result in the actual depth of plant colonization less

than predicted.

The other water chemistry parameters examined (color, chlorophyll, TP, and TN)

were found to provide reasonable estimates for predicting the potential depth of

macrophyte growth and could be particularly useful when SD transparency or E of a lake

is unknown. Managers should assess each lake independently and consider what water

chemistry variable is the dominant factor influencing plant growth. For example, true

color would be the best tool to use for predicting MDC for a dystrophic lake.

Submersed aquatic macrophytes play an integral role in the functioning of lake

processes, therefore, it is important for managers to understand how submersed plants

will respond to changes in lake conditions, such as eutrophication or altered water levels.

These models allow managers to assess potential changes in plant coverage that might

result from changes in light and water chemistry variables.















APPENDIX A
32-LAKE STUDY DATA













Table A-1. Maximum depth of plant colonization (MDC in meters), Secchi disk transparency (SD in meters), top, middle, and bottom
depths that the light meter was measured (Z top, Z middle, Z bottom in meters), top, middle, and bottom deck cell light
readings (deck top, deck middle, deck bottom in gmol s-1 m-2 per gA), and top, middle, and bottom underwater light
readings (Iz top, Iz middle, Iz bottom in gmol s-1 m-2 per gA), color (PCU), soil type, and plant species identification by
station (buoy number) at 32 Florida lakes sampled in 2004.


Lake County


Z
Buoy MDC SD Z
top


Z Deck Iz Z Deck Iz Soil
Deck top Iztop middle middle middle bottom bottom bottom Color type


10/29/04 Alligator Lake 2 2.6 1

10/29/04 Alligator Lake 3 2.5 1

10/29/04 Alligator Lake 6 2.7 0.9
10/22/04 Alto Alachua 2 4.3 0.8

10/22/04 Alto Alachua 6 1.8 0.8

10/22/04 Alto Alachua 8 1.4 0.7

08/11/04 Bay Hillsborough 2 2.9 1.5

08/11/04 Bay Hillsborough 3 0.9 B
k)
Ji 08/11/04 Bay Hillsborough 4 2.1 B

08/11/04 Bay Hillsborough OWL1 .
08/3/04 Beakman Lake 3 3.7 B

08/3/04 Beakman Lake 5 3.1 B

08/3/04 Beakman Lake 6 3.4 B

08/3/04 Beakman Lake SD 3.5

10/16/04 Bellamy Citrus 3 1.3 1.2

10/16/04 Bellamy Citrus 5 0.8 1.7

10/16/04 Bellamy Citrus 6 0.2 1.5

10/16/04 Bellamy Citrus OWL1 .


0.6 1427

0.6 1359

0.6 1367

0.5 1288

0.75 825

5 0.3 1016

1 1895

0.2 1705

0.2 1233

1 1727

1 1088

0.5 1678

1 1374


5 0.5 1569

5 0.4 1643

0.5 1567

1 1638


109.3 1.2

193.4 1.2

270.2 1.2

117.2 1

38.95 1.5

115.6 0.6

247.7 2

1190 0.4

711.2 0.5

415.9 2

0.13 1.5

808.4 1

26.38 1.5


403.6 1

472 0.8

501.4 1

238.7 2


947 30.27 2.1

1330 50.59 2.1

1366 63.79 1.8

1320 28.66 1.5

1073 5.59 2.3

773.3 39.99 0.9

1893 12.47 2.5

1739 831.2 0.6

1767 677.2 1

1734 93.2 2.5

1844 0.28 2

1694 825.6 1.5

1850 42.8 2


1423 171.3 1.4

1616 318.3 1.2

1569 77.87 1.5

1648 47.23 3


1306 16.41 65 Organic Hydrilla verticillata

1224 15.64 63 Organic Hydrilla verticillata

1357 34.94 69 Organic Hydrilla verticillata
1301 6.3 150 Mix Eleocharis baldwinii

831.8 0.55 152 Mix Eleocharis baldwinii

1049 20.15 147 Mix Eleocharis baldwinii

1829 3.24 38 Organic Chara sp.
1808 609.8 35 Sandy Chara sp.

1738 374.7 34 Organic Chara sp.

1823 49.68

2109 0.08 13 Sandy Websteria confervoides

1727 485.2 17 Sandy Websteria confervoides

1850 24.48 19 Sandy Websteria confervoides


1674 86.35 61 Organic Bacopa caroliniana
1564 179.9 61 Organic Hydrilla verticillata

1574 46.46 61 Organic Bacopa caroliniana
1566 7.86


Date


Species















Z Z Deck Iz Z Deck Iz Soil
Buoy MDC SD top Deck top Iz top middle middle middle bottom bottom bottom Color type
top middle middle middle bottom bottom bottom type


06/23/04 Brant

06/23/04 Brant

06/23/04 Brant

08/4/04 Church

08/4/04 Church

08/4/04 Church

11/20/04 Conway North

11/20/04 Conway North

11/20/04 Conway North

11/20/04 Conway North

11/20/04 Conway South

11/20/04 Conway South

11/20/04 Conway South

10/16/04 Dodd

10/16/04 Dodd

10/16/04 Dodd

10/16/04 Doe

10/16/04 Doe

10/16/04 Doe

9/10/04 Farles Prairie

9/10/04 Farles Prairie

9/10/04 Farles Prairie


8/6/04

8/6/04

8/6/04


Grasshopper

Grasshopper

Grasshopper


Hillsborough 2 1 B 0.5 1559 0.26

Hillsborough OW1 1 1 1473 121

Hillsborough OW2 1.25 0.2 1728 684.4

Hillsborough 1 2 1.5 0.5 2014 849.3

Hillsborough OW1 1.25 1 1585 492.1

Hillsborough OW2 1.5 1 2357 566

Orange 3 5.1 3 1 565.7 160.5

Orange 6 5.8 2.6 1 670.9 184.9

Orange 9 5.6 2.75 1 757.3 231.1

Orange OWL1 1 1384 653.1

Orange 4 5.7 2.5 1 1423 556.9

Orange 5 5.5 2.4 1 1637 578.5

Orange 8 6.3 2.6 1 1508 576.3

Citrus 3 0.8 1.25 0.5 935.8 235.4

Citrus 5 2.1 1.25 0.5 1173 149.1

Citrus 6 0.3 1.5 0.4 1366 484.5

Marion 3 4 3.5 1 1483 529

Marion 5 4.4 3.5 1 1437 563.6

Marion 8 4.3 3.5 1 1524 378.2


Lake

Lake

Lake


2 4.9 3.25 1

7 4.2 3.75 1

8 4.6 3.25 1


Hillsborough 1

Hillsborough 2

Hillsborough OW2


1552 0.22

1525 47.14 2

1637 401.6 0.6

2028 516.2 1.5

1616 149.2 2.5

2378 199.1 3

559.3 86.14 3

645.4 100.4 3

721.2 107.7 3

1371 313.9 3

1401 277.6 3

1627 279.9 3

1647 313.7 3

1032 113.9 1.5

1069 109.1 1.5

1368 449.4 1.2

1485 250.9 3

1427 220.5 3

1566 92.13 3


787.4 190.2 2 793.9 79.35 3


1454 250.1


2 1058 111.5 3


635.9 194.6 2 630.6 74.38 3


2.8 1.25 0.5 287.5 27.54

1.8 1 0.5 552.4 53.26

1.5 0.5 1177 206.2


271.7 4.29 1.3

560.5 17.43 1.5

1158 13.59 1.5


88 Mix Bacopa caroliniana


1572 15.93 89

1721 302.6 89

2005 301.6 28

1580 82.22 31

2359 47.66 25

541.4 47.57 7

646 32.31 8

699.4 60.76 9

1370 178.3

1436 149.8 9

1642 146.3 8

1692 172.1 8

1095 35.15 61

1225 41.69 62

1374 221 63

1486 129.5 9

1416 116.6 9

1552 67.59 14

794 40.76 11

1055 54.57 12

626.1 33.09 12

267.2 0.58 78

575 3.31 76

1127 0.2 80


Organic

Organic

Mix Chara sp.

Mix

Mix

Mix Vallisneria americana

Mix Potamogeton illinoensis

Mix Potamogeton illinoensis


Mix Vallisneria americana

Mix Vallisneria americana

Mix Nitella sp.

Sandy Ludwigia repens

Organic Utricularia sp.

Organic Hydrochloa caroliniensis

Mix Chara sp.

Mix Chara sp.

Mix Chara sp.
Myriophyllum
heterophyllum
Sandy Utricularia sp.
Sandy Myriophyllum
heterophyllum
Sandy Websteria confervoides

Sandy Utricularia sp.

Sandy


873.1 28.69 2 786.6 2.89 3 767.3 0.95


Table A-1. Continued.


County


Species


8/6/04 Grasshopper Hillsborough OWL1 .















Z Z Deck Iz Z Deck Iz Soil
Buoy MDC SD top Deck top Iz top iddle middle middle bottom bottom botto Color type
top middle middle middle bottom bottom bottom type


10/22/04 Hampton

10/22/04 Hampton

10/22/04 Hampton

10/16/04 Hernando

10/16/04 Hernando

10/16/04 Hernando

11/21/04 Ivanhoe

11/21/04 Ivanhoe

11/21/04 Ivanhoe

11/20/04 Little Conway

11/20/04 Little Conway

11/20/04 Little Conway

10/18/04 Little Santa Fe

10/18/04 Little Santa Fe

10/18/04 Little Santa Fe

08/11/04 Magdalene

08/11/04 Magdalene

08/11/04 Magdalene

08/4/04 Maurine

08/4/04 Maurine

08/4/04 Maurine

08/4/04 Maurine

08/12/04 Melrose Bay

08/12/04 Melrose Bay

08/12/04 Melrose Bay

05/27/04 Mill Dam


Bradford 5

Bradford 6

Bradford 9

Citrus 1

Citrus 2

Citrus 4

Orange 2

Orange 3

Orange 6

Orange 5

Orange 6

Orange 9

Alachua 2

Alachua 4

Alachua OW1

Hillsborough 1

Hillsborough 2

Hillsborough 6

Hillsborough 1

Hillsborough 5

Hillsborough 7

Hillsborough SD

Alachua 3

Alachua 7

Alachua 8

Marion 4


1.7 1 0.4 959.8 197.3

1.8 1 0.4 1231 189

1.7 0.8 0.5 1027 133.6

2.2 1.4 0.75 1067 95.33

2 1.5 0.6 1059 135.2

2.6 1.75 1 986.5 79.77

2 1 1 1228 392.5

2.7 1 1 1150 325.4

1.8 1.1 1 1113 214

6.1 1.25 1 1356 293.8

5.1 1 1 1197 176.6

5.5 1.75 1 1183 405.3

2 0.5 0.3 1257 49.92

2 0.5 0.2 1053 83.82

0.4 0.2 818.3 86

3.8 2 1 1961 502.5

3.6 1.75 1 1828 507.7

3.3 1.6 1 2093 336.8

1.3 B 0.2 1972 620.3

1 B 0.2 2010 814.8

1.3 B 0.3 1198 175.4


2.8 2

2.8 2

3 2

3 B


1 307.6 49.92


1 752.9 113.70

1 2031.0 403.20


968.7 76.49 0.9

1213 62.69 1.2

1029 53.67 1.4

1049 23.79 2.1

1054 22.92 1.8

970 9.65 2.5

1236 150.60 3

1156 125.40 3

1117 116.30 3

1353 92.37 3

1196 62.83 3

1169 145.60 3

1249 14.47 1.2

1191 28.53 0.6

786.6 15.02 0.6

1963 488.00 3

1883 206.10 3

2094 424.80 3

2064 439.40 0.6

2077 679.50 0.6

1306 109.80 0.9


300.9 0.18 2.5


758.4 32.02 3

2212 260.80 2.2


894.9 52.89 89

1262 40.78 91

1041 17.81 87

1047 1.24 61

977.5 7.27 62

934.2 4.26 56

1058 108.4 10

1150 62.35 11

1116 52.07 9

1328 30.61 14

1176 23.21 12

1169 55.37 12

1275 0.98 375

1072 7.3 381

801.2 1.63 399

1921 15.7 29

327.1 2.95 29

2059 86.54 43

2028 152.4 64

2052 397.8 64

1480 85.01 65


291.8 0.15 27

27

738.3 18.44 26

2210 323.1 14


Sandy Websteria confervoides

Sandy Websteria confervoides

Sandy Websteria confervoides

Organic Ceratophyllum demersum

Organic Ceratophyllum demersum

Organic Ceratophyllum demersum

Mix Najas guadalupensis

Mix Vallisneria americana

Sandy Vallisneria americana

Organic Vallisneria americana

Organic Hydrilla verticillata

Organic Hydrilla verticillata

Mix Eleocharis baldwinii

Mix Eleocharis baldwinii

Mix

Organic Unidentified plant

Organic Nitella sp.

Organic Najas guadalupensis

Sandy Bacopa caroliniana

Sandy Bacopa caroliniana

Sandy Bacopa caroliniana


Mix Mayaca fluviatilis

Mix Mayaca fluviatilis

Mix Mayaca fluviatilis

Mix Mayaca fluviatilis


Table A-1. Continued.


County


Species













Table A-1. Continued.


Z
Buoy MDC SD z
top


Z Deck Iz Z Deck Iz Soil
Deck top Iztop middle middle middle bottom bottom bottom Colo type


05/27/04 Mill Dam

05/27/04 Mill Dam

05/18/04 Newnan

05/18/04 Newnan

05/18/04 Newnan

08/25/04 Osceola

08/25/04 Osceola

08/25/04 Osceola

10/18/04 Santa Fe

10/18/04 Santa Fe

10/18/04 Santa Fe

05/13/04 Sellers

05/19/04 Starke

08/12/04 Stella

08/12/04 Stella

08/12/04 Stella

09/25/04 Taylor

09/25/04 Taylor

09/25/04 Taylor

06/16/04 Twin

06/16/04 Twin

06/16/04 Twin

06/1/04 Weir

06/1/04 Weir

06/1/04 Weir


Marion 7

Marion 8

Alachua 3

Alachua 6

Alachua OW1

Hillsborough 2

Hillsborough 4

Hillsborough 8

Alachua 1

Alachua 2

Alachua 3

Lake 2

Orange 1

Putnam 3

Putnam 7

Putnam 8

Hillsborough 1

Hillsborough OW1

Hillsborough OW2

Hillsborough 3

Hillsborough 5

Hillsborough OW1

Marion 1

Marion 6

Marion 8


2.8 3.05 1

2.4 B 1

0.9 0.3 0.5

0.4 0.3 0.5

0.25 0.5

3.3 2.1 1

3.2 2.1 1

4.0 2.1 1

3.5 1.4 1

4.0 1.3 1

4.1 1.4 1

9.2 5.75 1

1.5 0.75 1

4.3 2 1

4.1 2 1

4.4 2 1

3.1 1.5 1

1.5 1

1.5 1

2.8 0.5 1

2.5 0.5 1

0.5 1

2.9 1.5 1

2.8 1.4 1

3.3 1.5 1


588.3 146.7 2

1878 290.6 2

2184 155.4 0.6

2181 194.3 0.7

2098 19.37 0.8

1504 160.8 2

1778 389.3 2

1794 367.4 2

1135 96.34 2

1205 103.6 2

999.9 100.7 2

2327 1199 2

2011 499 1.5

651.4 143.5 2

1003 244.7 2

1014 282 2

1429 216.6 2

1516 44.8 2

1481 193.4 2

472.3 28.87 2

2028 74.64

1946 35.37 2

2065 267.5 2

2007 501.5 2

2104 664.9 2


597.9 99.55 3

2182 281.9

2179 106.6

2286 90.45

2098 1.16 1

1549 99.87 3

1779 382.3 3

1732 107.2 3

1162 17.47 2.5

1096 7.47 3

995.2 17.27 3

2335 1035 3

694.6 54.58 .

650.3 52 3

975.2 86.04 3

1019 102.4 3

1428 206.5 2.5

1516 41.3 3

1480 57.97 3

474.4 3.13


2058 22.3 2.5

2118 137.9 2.5

2064 284.2 2.5

2093 341.7 2.5


4.0 3.5 1 477.7 129.5 2 575.1 77.86 3


1811 185.1 15 Sandy Mayaca fluviatilis

14 Sandy Mayaca fluviatilis

112 Organic Ceratophyllum demersum

96 Organic Ceratophyllum demersum

2095 0.19 91 Organic.

1568 39.18 38 Organic Najas guadalupensis

1781 53.89 35 Organic Hydrilla verticillata

1695 11.41 37 Organic Utricularia sp.

1116 9.56 52 Organic Najas guadalupensis

1039 3.65 54 Organic Najas guadalupensis

971.8 0.79 52 Organic Najas guadalupensis

2270 729.9 2 Sandy Utricularia sp.

14 Sandy Vallisneria americana

681.3 19.92 19 Mix Najas guadalupensis

969.6 37.82 18 Mix Chara sp.

989.8 43.92 21 Mix Najas guadalupensis

1437 55.96 36 Organic Eleocharis baldwinii

1528 8.93 46 Organic

1525 16.75 41 Organic

15 Sandy Vallisneria americana

14 Sandy Vallisneria americana

1956 11.06 16 Sandy

2004 64.73 6 Sandy Nitella sp.

2076 161.8 7 Mix Nitella sp.

2122 296 8 Sandy Nitella sp.

511.9 50.17 10 Organic Hydrillaverticillata


County


Species


06/16/04 White Trout Hillsborough












Table A-1. Continued.


County


06/16/04 White Trout Hillsborough
06/16/04 White Trout Hillsborough
06/16/04 White Trout Hillsborough

Note: SD = Secchi disk transp,
visible on lake bottom


Buoy MDC SD
top

2 5.5 B 0.5
3 5.1 3 1
4 4.6 2.75 1

irency stations, OW


Z Deck Iz Z Deck Iz Soil
Deck top Iztop middle middle middle bottom bottom bottom Colo type

447.4 150.3 0.7 451.3 135.4 0.9 455.4 122.4 10 Organic
2153 194.2 2 2188 149.6 3 2184 196.5 13 Mix
2203 664.4 2 2215 224.7 3 1925 188.8 13 Mix

SOpen-water stations, OWL = Open-water light stations, B = S


Species

Vallisneria americana
Hydrilla verticillata
Utricularia sp.

ecchi disk was


























Maximum depth of plant colonization (MDC in meters), yearly mean Secchi
disk transparency (SD in meters), color (PCU), chlorophyll (gg/L), total

phosphorus (TP in gg/L), total nitrogen (TN gg/L) for 279 Florida lake years
sampled during 1991 to 2004.


SD Color Chlorophyll TP TN


35.50
7.00
8.13
18.00


5.00
6.50
9.50
35.00
90.50
3.50


28.67
13.71
58.31
166.80
128.00
65.52
6.30
122.50
11.00
3.88
62.83
11.31
21.21
19.20
43.75
70.63
380.19
128.09


14.27
1.90
3.05
53.21
1.58
3.89
2.26
5.56
23.67
23.33
1.20
9.09
17.07
3.33
181.87
19.92
20.40
6.25
2.46
3.11
5.55
2.00
10.36
3.96
15.96
3.08
166.40
11.82
3.97
2.58
3.20


17.06
7.40
8.19
58.30
7.08
6.53
10.29
8.36
40.10
33.73
3.77
14.39
33.56
12.51
139.23
139.47
35.00
20.69
6.36
10.37
16.45
5.07
21.67
10.87
24.89
17.61
56.20
14.76
25.92
8.30
11.42


566.06
204.29
245.71
1144.55
377.50
134.72
101.39
456.11
687.67
980.30
122.33
709.39
779.63
368.65
3679.33
1385.83
1067.67
774.44
180.40
533.33
700.61
158.52
733.61
479.67
764.44
519.72
3389.00
411.21
1009.44
563.64
754.24


Table B-1.


APPENDIX B
279-LAKE-YEAR STUDY


Lake

Alto
Boll Green
Chipco
Clear
Erie
Fanny
Georges
Gillis
Grandin
Little Orange
Alice
Banana
Bass
Bear
Beauclaire
Bethel
Blue
Brant
Broward
Cherry
Church
Como
Crenshaw
David
De Witt
Deborah
Dora West
Dorr
Eaton
Emma
Emporia


County

Alachua
Putnam
Putnam
Orange
Leon
Putnam
Putnam
Putnam
Putnam
Alachua
Hillsborough
Putnam
Pasco
Seminole
Lake
Volusia
Volusia
Hillsborough
Putnam
Lake
Hillsborough
Putnam
Hillsborough
St Lucie
St Lucie
St Lucie
Lake
Lake
Marion
Lake
Volusia


MDC

2.5
4.1
3.9
2.2
2.8
4.4
3.4
3.3
1.3
2
5.5
1.8
2.7
3
1.7
1.6
2.9
4.5
4.3
3.3
4.3
3.4
2.3
1.6
1.9
1.8
0.9
1.3
1.6
5.5
2.9













Table B-1. Continued.


SD Color Chlorophyll


TP TN


Floyd
Formosa
Georgia
Gertrude
Halfmoon
Hall
Hampton
Hart
Henderson
Hernando
Hiawatha
Hickorynut
Howell
Island
Jean
Jeffery
Joanna
Karen
Keene
Keystone
Kingsley
Kirkland
Little Henderson
Little Weir
Ola
Osceola
Sellers
Seminary
Bay
Bear
Blue Heron
Conway South
Coon
Cowpen
Crescent
Croft
Crooked
Dead Lady
Diane
Disston
Eagle
Egypt
Elbert
English
Erie
Fannie
Fredrica


Pasco 2.8
Orange 2.3
Orange 5.3
Lake 8
Marion 3.1
Leon 6
Bradford 4.1
Orange 1.8
Citrus 2.7
Citrus 3
Hillsborough 5.2
Orange 5.8
Seminole 4
Marion 0.8
St Lucie 2.2
St Lucie 2.2
Lake 3.1
St Lucie 2.3
Hillsborough 2.1
Hillsborough 3.7
Clay 8.3
Lake 4.1
Citrus 2.5
Marion 3.4
Orange 6.1
Hillsborough 5.2
Lake 7.5
Seminole 6.5
Orange 3
Seminole 2.2
Leon 2.3
Orange 6.8
Osceola 1
Putnam 3.9
Hillsborough 3.3
Citrus 3.4
Lake 2.8
Hillsborough 2.6
Leon 4.2
Flagler 0.7
Polk 2.8
Hillsborough 2.5
Polk 4.9
Putnam 2.8
Leon 1.7
Polk 1.7
Orange 5


County


MDC


6.83
3.61
9.67
16.35
4.31
13.84
6.35
1.97
5.92
7.75
6.79
15.46
3.16
6.04
6.33
5.14
11.95
3.84
5.10
9.23
21.81
10.71
5.91
5.85
12.03
15.22
20.00
15.63
2.91
10.89
2.70
11.38
1.78
10.23
7.00
12.00
5.10
5.65
8.31
1.69
3.00
4.77
5.50
4.76
5.81
2.14
10.38


26.00
14.54
18.35
6.28
47.94
6.31
12.06
183.33
151.05
101.78
36.69
53.50


3.00


10.75
12.20
14.25
119.00
98.71
6.43


66.19
10.50
9.50
36.50
2.50
8.42
21.00
9.00
15.00
7.00
217.00
1.00
22.00
19.00
15.00
75.00
6.00
290.00
10.00
12.00
9.00
35.00


63.00
7.00


3.42
42.00
3.56
2.47
9.92
16.07
5.06
3.39
7.61
3.60
10.17
1.08
47.58
2.83
2.86
2.00
2.05
22.04
12.33
2.70
3.56
2.37
9.06
9.38
3.06
1.94
1.03
2.50
47.77
3.15
51.48
7.67
8.37
1.67
10.75
2.31
10.36
31.23
2.56
7.00
27.50
19.25
3.33
13.33
2.89
27.86
4.73


14.47
38.17
8.22
7.10
16.47
23.77
11.25
15.08
19.17
10.63
15.61
5.88
46.75
12.99
10.97
9.33
6.33
32.89
36.23
9.18
4.59
7.27
15.67
12.38
12.08
6.25
3.39
8.19
39.23
12.39
55.15
10.00
35.23
5.00
14.75
6.72
21.77
36.69
13.19
25.36
19.33
20.58
12.33
13.00
5.17
56.00
12.87


826.11
796.11
535.56
558.61
620.83
412.58
489.72
1143.06
898.33
564.00
508.89
730.00
1068.33
298.33
491.94
520.00
422.08
1086.30
1149.67
462.73
260.74
357.17
877.78
915.83
560.00
443.06
42.50
354.44
1455.13
391.47
938.48
440.51
1045.00
86.67
549.17
601.28
971.03
1104.62
304.72
965.76
1110.00
745.00
553.33
870.00
419.44
1133.33
417.33













Table B-1. Continued.


County


MDC


Gillis Putnam
Grasshopper Lake
Haines Polk
Halfmoon Hillsborough
Hamilton Polk
Hampton Bradford
Harney Volusia
Harris Lake
Hartridge Polk
Henry Polk
Higgenbotham Putnam
Highland Orange
Howard Polk
Idlewild Lake
Ivanhoe East Orange
Ivanhoe Middle Orange
Ivanhoe West Orange
Lawsona Orange
Little Bass Polk
Little Halfmoon Hillsborough
Little Santa Fe Alachua
Little Spirit Polk
Lizzie Osceola
Marsha Orange
Mary Marion
Rosa Putnam
Ashby Volusia
Bennett Orange
Conway North Orange
Conway South Orange
Eaton Marion
Highland Orange
Howell Seminole
Bellamy Citrus
Blue Highlands
Broward Putnam
Clay Highlands
Crews Highlands
Denton Highlands
Dinner Highlands
Dodd Citrus
Eagle Pond Highlands
Floral City Citrus
Francis Highlands
Hall Leon
Hampton Citrus
Henderson Citrus


SD Color Chlorophyll


7.44
12.38
1.99
6.89
3.63
6.49
3.40
2.72
4.62
1.51
11.57
4.17
2.22
5.30
3.31
3.91
3.05
3.46
2.24
11.19
5.67
8.00
4.56
16.21
14.50
14.69
2.56
7.56
8.60
10.49
2.40
4.38
2.67
9.19
10.89
15.83
10.61
4.37
23.02
20.27
8.70
4.19
3.64
6.50
16.68
3.58
4.52


6.00
0.00
55.00
9.00
62.00
28.00
108.00
12.00
9.00
295.00
7.00
9.00
20.00
55.00
14.00
15.00
15.00


40.00
9.00
54.00
27.00
97.00
13.00
1.00
4.00
192.75
12.88
6.96
7.17
380.19
13.50
15.00
31.00
7.00
4.00
8.00
28.00
3.00
4.00
29.00
18.00
157.00
5.00
6.00
111.00
107.00


7.06
1.41
99.10
6.13
8.61
4.74
8.75
67.53
1.00
4.60
2.46
22.00
39.23
10.09
29.48
24.03
29.78
27.28
92.85
2.67
7.33
5.58
3.74
2.64
1.61
6.95
3.92
7.46
11.88
9.36
6.45
16.42
32.42
3.04
4.22
1.96
5.45
5.83
1.64
1.67
4.04
13.39
12.83
12.40
3.52
16.43
9.79


TP TN

9.03 318.06
2.05 235.13
158.21 1804.62
13.88 533.75
116.33 1042.22
9.79 511.54
38.56 1157.92
31.20 1839.67
9.00 396.67
131.00 1207.33
5.77 389.49
36.13 625.33
31.40 1446.67
15.64 1005.76
30.82 770.61
29.58 612.78
31.85 720.37
82.81 996.11
344.22 1912.95
7.58 451.39
12.63 528.97
20.33 704.17
15.72 738.72
7.14 391.39
2.58 118.61
5.59 86.92
67.14 737.50
18.30 613.70
11.15 534.55
10.09 458.79
22.67 1276.67
32.00 620.00
35.83 653.33
11.11 687.04
10.22 575.56
6.29 296.46
11.12 459.70
13.77 423.67
3.39 3133.64
7.67 633.33
10.78 774.07
12.50 698.79
33.44 974.17
14.42 510.33
11.80 320.60
30.26 929.64
21.67 960.91













Table B-1. Continued.

Year Lake County MDC SD Color Chlorophyll TP TN

1996 Hickorynut Orange 4.6 10.97 19.00 2.85 7.64 694.24
1996 Hill Highlands 3.2 6.15 13.00 5.81 10.00 347.41
1996 Jackson Highlands 5 11.22 10.00 4.50 12.28 337.78
1996 Josephine Center Highlands 1.2 1.81 92.00 24.97 46.10 959.67
1996 Josephine East Highlands 1 2.46 58.00 24.33 35.30 915.56
1996 Josephine West Highlands 0.8 1.56 127.00 33.40 82.50 1079.33
1996 Lillian Highlands 4.5 8.23 6.00 7.73 9.58 631.21
1996 Little Henderson Citrus 4 5.00 77.00 8.83 18.61 932.73
1996 Little Jackson Highlands 2.7 2.94 27.50 52.78 51.67 1167.41
1996 Little Santa Fe Alachua 3.7 5.41 106.70 6.03 10.85 450.30
1996 Ola Orange 6.6 14.96 8.00 3.42 9.82 525.00
1997 Carroll Hillsborough 4.6 11.00 8.69 2.33 12.67 463.33
1997 Fanny Putnam 5.1 11.83 3.63 2.28 4.78 129.44
1997 Lily Clay 4 11.50 2.76 2.74 6.33 109.26
1997 Lochloosa Alachua 2.5 2.24 222.00 70.66 52.14 1795.45
1997 Sheelar Clay 6 26.77 1.39 1.62 3.25 87.08
1997 Winnemissett Volusia 6.2 18.75 6.50 0.50 5.75 193.33
1998 Ada Seminole 3.2 8.19 14.00 5.89 16.50 534.67
1998 Alto Alachua 2.5 4.63 83.30 9.36 17.97 586.11
1998 Bay Orange 2.1 3.04 25.63 39.15 37.50 1086.67
1998 Chipco Putnam 5.5 11.86 8.13 5.43 10.50 319.33
1998 Cowpen Putnam 4.5 9.50 1.00 2.78 6.56 193.33
1998 Crooked Lake 1.9 5.71 37.31 7.58 13.94 718.89
1998 Crystal Clay 3.9 7.40 9.00 5.67 11.30 264.67
1998 Dorr Lake 0.7 2.08 70.63 15.60 18.00 499.33
1998 Gillis Putnam 2.2 3.47 10.77 11.47 912.33
1998 Grandin Putnam 1.6 3.95 19.67 28.76 501.21
1998 Grasshopper Lake 3.7 6.39 112.42 3.25 5.72 365.28
1998 Joes Marion 4.2 7.83 11.00 3.88 10.39 598.18
1998 Kingsley Clay 7.5 16.88 6.43 6.96 8.13 323.75
1998 Little Bear Seminole 2.9 12.49 16.52 3.17 13.00 474.17
1998 Little Crystal Clay 2.7 5.87 25.50 7.78 12.50 330.00
1998 Little Orange Alachua 2.2 2.76 173.65 10.58 129.81 958.33
1998 Little Santa Fe Alachua 3.1 4.41 106.70 11.42 14.56 530.00
1998 Little Weir Marion 3.5 6.18 10.50 8.58 11.09 816.67
1998 Lizzie Osceola 1 2.67 98.33 5.30 22.52 744.81
1998 Sellers Lake 7.6 21.00 2.50 1.33 3.50 76.06
1998 Seminary Seminole 5.4 15.49 8.42 2.52 7.94 373.03
1999 Bear Seminole 5.9 13.01 13.71 4.17 14.35 440.42
1999 Beauclaire Lake 1.5 0.78 58.31 291.56 169.44 4551.94
1999 Bennett Orange 3.8 11.15 12.88 2.56 16.74 524.44
1999 Carlton Orange 1 1.06 41.87 219.25 85.97 3572.22
1999 Disston Flagler 0.9 1.29 428.47 4.00 25.67 1074.72
1999 Erie Leon 2.2 4.77 .2.25 6.82 457.58
1999 Gatlin Orange 2.7 2.25 15.64 36.81 21.39 1209.17
1999 Halfmoon Marion 2.2 4.85 47.94 8.00 14.78 774.17














Table B-1. Continued.

Year Lake County MDC SD Color Chlorophyll TP TN

1999 Hiawatha Leon 2.6 4.41 174.17 5.39 19.56 520.56
1999 Josephine Center Highlands 1.6 1.82 134.05 20.17 57.47 930.56
1999 Josephine East Highlands 1.8 2.58 87.40 37.70 47.47 1003.67
1999 Josephine West Highlands 1.4 1.53 158.30 19.78 93.72 977.78
1999 June Highlands 3.4 4.97 13.70 17.25 13.78 745.00
1999 Juniper East Walton 3.7 6.93 14.81 6.64 12.94 367.22
1999 Juniper West Walton 3.5 6.67 14.79 5.33 11.56 717.78
1999 Little Conway Orange 8.5 12.51 6.00 3.69 11.50 479.72
1999 Lochloosa Alachua 2.6 1.54 222.00 152.50 62.93 2351.25
1999 Wooten Jefferson 4.2 10.78 .4.10 13.52 301.90
2000 Asbury North Clay 6.5 8.50 14.50 7.81 20.56 409.63
2000 Bedford Bradford 2.4 5.64 13.00 11.56 44.33 783.06
2000 Deerback Marion 1.8 8.27 19.56 3.50 10.75 559.58
2000 Dexter Polk 5.3 15.43 9.60 2.25 9.21 425.83
2000 Diane Leon 3.7 4.40 9.07 8.78 22.36 529.72
2000 Eagle Polk 3.6 3.50 9.75 18.54 21.42 807.50
2000 East Pasco 3.6 8.75 16.98 3.39 18.00 582.22
2000 Florida Seminole 2.5 5.14 12.82 33.36 909.44
2000 Hartridge Polk 1.7 4.35 11.00 14.50 20.67 625.00
2000 Henry Polk 1.2 1.31 98.50 8.05 96.24 1122.86
2000 Little Bass Polk 2 1.33 23.25 148.25 401.64 2643.61
2000 Little Santa Fe Alachua 3.2 5.34 106.70 9.94 15.83 528.61
2001 Arbuckle Polk 1 1.46 269.00 17.44 82.22 1258.33
2001 Big Volusia 2.2 6.00 56.40 5.93 18.57 707.62
2001 Cassidy Holmes 6 18.15 1.33 1.83 4.71 129.58
2001 Conway North Orange 4.6 13.29 6.33 4.00 11.83 366.67
2001 Conway South Orange 7 14.90 7.50 2.58 10.17 359.17
2001 Crooked Polk 5.4 8.16 15.50 3.97 13.53 580.94
2001 De Witt St Lucie 2 3.04 20.50 13.82 29.94 988.89
2001 Deborah St Lucie 1.7 5.80 19.20 2.25 12.13 508.33
2001 Grayton Walton 1.5 4.42 32.25 3.44 11.92 251.11
2001 Howell Seminole 3.3 2.75 15.00 38.45 41.95 1032.80
2001 Istokpoga Highlands 1.7 2.97 55.25 36.75 55.61 1515.56
2001 Ivanhoe East Orange 1.8 3.63 12.00 30.71 25.74 827.86
2001 Ivanhoe Middle Orange 1.7 4.17 10.50 25.29 27.19 725.24
2001 Ivanhoe West Orange 2.7 4.12 13.00 30.43 35.62 692.86
2001 Josephine Center Highlands 0.8 1.75 105.00 25.08 76.22 1007.78
2001 Josephine East Highlands 1 2.68 70.50 29.36 51.58 944.55
2001 Josephine West Highlands 1.2 1.57 121.00 25.33 111.31 1068.06
2001 Jovita Pasco 4.2 5.79 8.75 10.22 21.47 783.06
2001 June Highlands 4.7 9.03 7.75 6.83 11.11 499.72
2001 Juniper East Walton 3.7 7.64 13.67 6.00 11.18 417.64
2001 Juniper West Walton 2.4 6.93 14.67 7.78 11.42 864.72
2001 Karen St Lucie 1.9 4.82 14.25 5.10 15.53 665.67
2001 Little Wilson Hillsborough 4 5.89 31.00 8.63 25.44 875.93
2001 Lochloosa Alachua 1.5 1.30 222.00 138.00 89.88 3823.75














Table B-1. Continued.

Year Lake County MDC SD Color Chlorophyll TP TN

2001 Margaret St Lucie 2.2 5.02 8.75 6.52 12.19 434.44
2001 Viola Highlands 5.5 14.90 3.00 2.58 7.92 446.67
2002 Bessie Orange 8.6 15.79 8.00 2.06 7.08 479.72
2002 E Miami-Dade 7.8 17.67 3.75 1.41 5.22 321.48
2002 Grassy Highlands 4.7 12.06 11.80 2.69 9.50 716.11
2002 Sellers Lake 8.9 19.83 1.83 1.09 3.33 66.67
2002 Verona Highlands 6.1 14.09 5.10 6.41 10.37 340.37
2003 Alligator Osceola 2.6 3.37 54.58 5.11 19.63 875.14
2003 Annie Putnam 3 9.67 9.00 3.78 10.08 428.33
2003 Blue Lake 2 3.27 72.50 5.78 15.67 385.56
2003 Clear Lake 4.8 11.65 14.80 2.64 13.31 502.50
2003 Cliff Broward 4.4 7.33 26.00 5.28 20.89 455.00
2003 Conway North Orange 8 14.30 8.00 3.47 8.73 412.00
2003 Conway South Orange 7.1 14.17 8.00 4.67 10.20 434.00
2003 Delevoe Broward 2.3 6.29 8.00 29.21 44.57 828.57
2003 Farm 13 Indian River 2.1 3.09 85.00 35.94 76.75 1634.44
2003 Florence Seminole 4.2 9.33 11.00 5.00 12.83 518.33
2003 Flynn Hillsborough 1.9 3.67 63.08 5.97 10.14 1145.28
2003 Formosa Orange 3.4 6.77 14.00 30.21 45.03 856.67
2003 Galilee Putnam 2.5 3.77 8.00 10.00 15.00 230.00
2003 Highland Miami-Dade 5.2 7.27 17.00 7.00 15.00 462.33
2003 Highland Orange 2.8 3.52 12.00 39.67 50.17 773.33
2003 Istokpoga Highlands 2 2.46 62.00 51.75 64.97 1382.50
2003 Ivanhoe East Orange 2.3 5.91 11.40 14.00 34.72 707.33
2003 Ivanhoe Middle Orange 2.4 6.04 11.73 15.71 26.85 681.30
2003 Ivanhoe West Orange 3.4 6.59 11.65 22.33 29.95 633.67
2003 Jem Lake 3.5 8.98 9.83 5.75 12.06 481.94
2003 John's Orange 1.3 2.54 125.00 16.42 55.97 1298.50
2003 Josephine Center Highlands 1.2 1.55 173.00 22.11 74.36 916.11
2003 Josephine East Highlands 1.2 2.02 113.00 40.61 59.03 1036.39
2003 Josephine West Highlands 1.1 1.55 212.00 17.33 114.33 928.89
2003 Lochloosa Alachua 1.1 2.47 222.00 26.57 36.50 1544.50
2003 Winyah Orange 2 6.83 23.00 30.52 56.57 1019.33
2004 Alto Alachua 2.5 3.37 102.75 13.88 19.58 763.94
2004 Bay Marion 2 3.83 19.00 16.04 24.62 813.11
2004 Bellamy Citrus 0.7 4.76 74.00 9.27 22.90 1207.62
2004 Brant Hillsborough 1 3.05 107.00 43.50 52.10 1203.67
2004 Church Hillsborough 2 8.10 11.00 4.81 15.58 656.27
2004 Conway North Orange 5.5 17.00 7.00 2.00 10.33 404.44
2004 Conway South Orange 5.8 12.39 6.50 4.11 10.89 388.89
2004 Dodd Citrus 1.0 5.21 79.75 8.72 19.94 1289.17
2004 Doe Marion 4.2 4.50 4.33 11.33 283.33
2004 Grasshopper Lake 2.2 2.71 208.67 4.36 8.70 958.18
2004 Hampton Bradford 1.7 4.71 10.00 5.25 11.58 490.83
2004 Hernando Citrus 2.3 4.61 71.40 9.08 20.25 1112.08
2004 Ivanhoe East Orange 2.2 4.88 9.50 21.04 17.10 537.62















SD Color Chlorophyll TP


Orange 5.6
Alachua 2
Hillsborough 3.6
Hillsborough 1.2
Alachua 2.9
Marion 2.7
Alachua 0.6
Hillsborough 3.5
Alachua 3.9
Lake 9.2
Orange 1.5
Putnam 4.3
Hillsborough 3.1
Hillsborough 2.6
Marion 3
Hillsborough 4.8


12.97
2.91
7.68
6.07
5.52
9.27
0.97
6.89
5.34
18.68
3.48
8.33
5.95
3.89
6.17
9.28


8.00
180.75
32.80


41.00
14.00
206.83
40.00
45.50
5.00
18.67


35.50
12.50
6.92
12.60


4.11 11.33 496.67
6.97 18.77 925.67
6.75 19.42 811.39
7.26 20.66 801.14
8.80 13.90 562.67
3.83 10.27 471.33
223.84 121.64 3479.12
7.08 20.25 847.50
8.00 12.13 564.33
2.52 4.70 250.30
25.50 24.67 881.67
5.50 7.67 598.33
8.00 22.04 717.92
22.96 24.70 802.28
11.00 13.50 863.33
4.67 13.67 437.14


Table B-1. Continued.


County


MDC


Little Conway
Little Santa Fe
Magdalene
Maurine
Melrose Bay
Mill Dam
Newnan
Osceola
Santa Fe
Sellers
Starke
Stella
Taylor
Twin
Weir
White Trout
















LIST OF REFERENCES


APHA. 1992. Standard Methods for the Examination of Water and Wastewater. 18th
Edition. Am. Public Health Assn. Washington, D. C.

Bachmann, R. W., M. V. Hoyer, D. E. Canfield, Jr. 2001. Evaluation of recent
limnological changes at Lake Apopka. Hydrobiologia. 448: 19-26.

Barko, J. W., D. Gunnison, and S. R. Carpenter. 1991. Sediment interaction with
submersed macrophyte growth and community dynamics. Aquat. Bot. 41: 41-65.

Bowling, L. C., M. S. Steane, and P. A. Bays. 1986. The spectral distribution and
attenuation of underwater irradiance in Tasmanian inland water. Freshwater Biol.
16: 331-335.

Canfield, D. E., Jr. 1983. Predication of chlorophyll a concentrations in Florida Lakes: the
importance of phosphorus and nitrogen. Water Resour. Bull. 19(2): 255-262.

Canfield, D. E., Jr., and L. M. Hodgson. 1983. Predication of Secchi disc depths in
Florida lakes: impact of algal biomass and organic color. Hydrobiologia. 99: 51-
60.

Canfield, D. E., Jr., K. A. Langeland, S. B. Linda, and W. T. Haller. 1985. Relations
between water transparency and maximum depth of macrophyte colonization in
lakes. J. Aquat. Plant Manage. 23: 25-28.

Canfield, D. E., Jr., and M. V. Hoyer. 1988. Regional geology and the chemical and
trophic state characteristics of Florida lakes. Lake and Reserv. Manage. 4(1): 21-
31.

Chambers, P. A., and J. Kalff. 1985. Depth distribution and biomass of submersed
aquatic macrophyte communities in relation to Secchi depth. Can. J. fish. Aquat.
Sci. 42: 701-709.

Cole, G. A. 1983. Textbook of limnology. Third Edition. C. V. Mosby Company. St.
Louis, MO.

D'Elia, C. F., P. A. Steudler, and N. Corwin. 1977. Determination of total nitrogen in
aqueous samples using persulfate digestion. Limnol. Oceanogr. 22: 760-764.









Duarte, C. M., and J. Kalff. 1986. Littoral slope as a predictor of the maximum biomass
of submerged macrophyte communities. Limnol. Oceanogr. 31(5): 1072-1080.

Duarte, C. M., and J. Kalff 1990. Patterns in the submerged macrophyte biomass of lakes
and the importance of the scale of analysis in the interpretation. Can. J. Aquat.
Sci. 47: 357-363.

Florida LAKEWATCH. 2003. Florida LAKEWATCH annual data summaries 2002.
Department of Fisheries and Aquatic Sciences, University of Florida / Institute of
Food and Agricultural Sciences, Gainesville, FL.

Havens, K. E. 2003. Submerged aquatic vegetation correlations with depth and light
attenuating materials in a shallow subtropical lake. Hydrobiologia. 493: 173-186.

Holmes, R. W. 1970. The Secchi disk in turbid coastal waters. Limnol. and Oceanogr.
15: 688-694.

Hoyer, M. V, T. K Frazer, S. K. Notestein, and D. E Canfield, Jr. 2004. Vegetative
characteristics of three low-lying Florida coastal rivers in relation to flow, light,
salinity and nutrients. Hydrobiologia. 528: 31-43.

Hudon, C., S. Lalonde., and P. Gagnon. 2000. Ranking the effects of site exposure, plant
growth form, water depth, and transparency on aquatic plant biomass. Can J. Fish.
Aquat. Sci. 57(Suppl. 1): 31-42.

Hutchinson, G. E. 1975. A treatise of limnology. Vol. 3. Limnological botany. John
Wiley and Son, Inc. New York, NY.

Jupp, B. P., and D. H. N. Spence. 1977. Limitations on macrophytes in a eutrophic lake,
Loch Leven. J. Ecol. 65: 175-186.

Langeland, K. A. 1996. Hydrilla verticillata (L.F.) Royle (Hydrocharitaceae), the perfect
aquatic weed. Castanea. 61(3): 293-304.

Lind, O. T. 1974. Handbook of common methods in limnology. The C. V. Mosby
Company. St Louis, MO.

Maristo, L. 1941. Die Seetypen Finnlands auf floristischer und vegetations-
physiognomischer Grundlage. Suom. Elain-ja Kasvitiet. Seuran Vanamon
Kasvitiet. Julk. Ann Bot. Soc. Zool. Bot. Vanamo. No. 5: 314.

McClave, J. T., and T. Sincich. 2000. Statistics 8th Edition. Prentice Hall. Upper Saddle
River, NJ.









Menzel, D. W., and N. Corwin. 1965. The measurement of total phosphorus in seawater
based on the liberation of organically bound fractions by persulfate oxidation.
Limnol. and Oceanogr. 10: 280-282.

Murphy. J., and J. P. Riley. 1962. A modified single solution method for the
determination of phosphate in natural waters. Anal. Chim. Acta 27: 31-36.

Poole, H. H., and W. R. G. Atkins. 1929. Photo-electric measurement of submarine
illumination throughout the year. J. Mar. Biol. Assoc. U.K. 16: 297-324.

Rickett, H. W. 1924. A quantitative study of the larger aquatic plants of Green Lake,
Wisconsin. Trans. Wisc. Acad. Arts Sci. Lett. 21: 381-414.

Sartory, D. P., and J. U. Grobbelarr. 1984. Extraction of chlorophyll a from freshwater
phytoplankton for spectrophotometric analysis. Hydrobiologia. 114: 117-187.

Scheffer, M. 1998. Ecology of shallow lakes. Chapman & Hall. London, England.

Sheldon, R. B., and Boylen, C. W. 1977. Maximum depth inhabited by aquatic vascular
plants. Am. Midl. Nat. 97(1): 248-254.

Van, T. K, W. T. Haller, and G. Bowes. 1976. Comparison of the photosynthetic
characteristics of three submersed aquatic plants. Plant Physiol. 58: 761-768.

Walker, T. A. 1980. A correction to the Poole and Atkins Secchi Disc/Light-Attenuation
Formula. J. Mar. Biol. Ass. U.K. 60: 769-771.

Weisner, S. E. B., J. A. Strand, and H. Sandsten. 1997. Mechanisms regulating
abundance of submerged vegetation in shallow eutrophic lakes. Oceologia. 109:
592-599.

Zimmerman, R. C., A. Cabello-Pasini, and R. S. Alberte. 1994. Modeling daily
production of aquatic macrophytes from irradiance measurements: a comparative
analysis. Mar. Ecol. Prog. Ser. 114: 185-196.















BIOGRAPHICAL SKETCH

Alexis J. Caffrey earned an Associate of Arts degree at Santa Fe Community

College in Gainesville, FL. She went on to earn a Bachelor of Science degree at the

University of Florida with a major in Wildlife Ecology and Conservation.




Full Text

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FACTORS AFFECTING THE MAXIMUM DEPTH OF COLONIZATION BY SUBMERSED MACROPHYTES IN FLORIDA LAKES By ALEXIS JORDAN CAFFREY 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 Alexis Jordan Caffrey

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iii ACKNOWLEDGMENTS Gratitude is expressed to the many people w ho helped me carry out this project. Special thanks are given to Mark Hoyer who helped me w ith my project in ways too numerous to list. Julie Terrell assisted in providing the Florida LAKEWATCH data. Claude Brown and Eric Schultz provided im measurable professional advice as well as many long days out in the fiel d helping with field sampling. Appreciation is granted to David Watson and Dan Willis for providing directions to many of the sampled lakes. Appreciation is expressed to Dr. Roger Bachmann, a brilli ant limnologist, for guiding me in analyzing my light readings. Thanks ar e given to Dr. Daniel E. Canfield, Jr., for funding the project and serving as my committ ee chairman and advisor. Gratitude is expressed to Dr. Charles E. Cichra for serv ing as my committee cochair and for offering encouragement and guidance. Finally, Dr. Kenneth Langeland served on my committee and helped oversee the project.

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iv TABLE OF CONTENTS page ACKNOWLEDGMENTS.................................................................................................iii LIST OF TABLES...............................................................................................................v LIST OF FIGURES...........................................................................................................vi ABSTRACT......................................................................................................................v ii CHAPTER 1 INTRODUCTION........................................................................................................1 2 MATERIALS AND METHODS.................................................................................3 3 RESULTS AND DISCUSSION.................................................................................10 4 CONCLUSION...........................................................................................................21 APPENDIX A 32-LAKE STUDY DATA..........................................................................................24 B 279-LAKE-YEAR STUDY........................................................................................30 LIST OF REFERENCES...................................................................................................37 BIOGRAPHICAL SKETCH.............................................................................................40

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v LIST OF TABLES Table page 3-1 Descriptive statistics for the maximu m depth of plant colonization (MDC in meter), Secchi disk...................................................................................................16 3-2 Multiple regression equations relating Secchi disk (SD in meters), light attenuation coefficient..............................................................................................18 3-3 Mean maximum depth of plant colonizat ion (MDC in meters) and slope values by lake and the relationship between MDC.............................................................19 3-4 Descriptive statistics for maximum depth of plant colonization (MDC in meters), Secchi disk..................................................................................................20 3-5 Regression equations of the maximum depth of submersed plant colonization......20 A-1 Maximum depth of plant colonizatio n (MDC in meters), Secchi disk transparency (SD in meters).....................................................................................25 B-1 Maximum depth of plant colonization (MDC in meters), yearly mean Secchi disk transparency......................................................................................................30

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vi LIST OF FIGURES Figure page 2-1 Locations of lakes sampled for both studies..............................................................9 3-1 Relationship between the mean ma ximum depth of submersed macrophyte colonization and mean Secchi disc depth (A) and mean light attenuation (B)........17 3-2 Relationships between mean Secchi disc depth and mean light attenuation (A, B)............................................................................................................................. .18 3-3 Comparison of a calculated maximum lin e to the best-fit line relating yearly Secchi disk depth to the maximu m depth of plant colonization..............................20

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vii 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 THE MAXIMUM DEPTH OF COLONIZATION BY SUBMERSED MACROPHYTES IN FLORIDA LAKES By Alexis Jordan Caffrey August 2006 Chair: Daniel E. Canfield, Jr. Cochair: Charles E. Cichra Major Department: Fisher ies and Aquatic Sciences In 32 Florida lakes, Secchi disk (SD) transparency, light attenuation coefficient values, plant and sediment t ype, and slope were examined with respect to the maximum depth of plant colonization (MDC). In the 32-lake study, MDC was shown to be significantly related to light through measurem ents taken by a SD (R2 = 0.46; p < 0.0001) and a light meter (R2 = 0.41; p < 0.0001). There was no significant difference in the mean percent of light penetration at MDC stations between hydrilla ( Hydrilla verticillata Royle) and non-hydrilla species (p = 0.2), and fu rthermore, between angiosperms and charophytes (p = 0.4). Similarly, organic, sandy, and mixed sediment types were not shown to exert a significant influence (p = 0.07) on the depth of aquatic plant colonization. Lake bottom slope was not shown to be significantly related (R2 = 0.03; p = 0.35) to the maximum depth of plant growth. To increase the sample size, SD transparen cy, color, chlorophyll, and water column nutrients (total phosphorus and total nitrog en) were examined with respect to the

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viii maximum depth of macrophyte growth for 279-lake-years of information. An upper limit line relating MDC to SD in me ters was calculated and was found to be equal to: log (max MDC) = 0.52 log (SD) + 0.59. The maximum MDC line describes light limitation when the MDC response fall on or near the res ponse curve and when MDC values fall below the line, there is some other limiting envir onmental factor. For the 279-lake-year study, the maximum depth of aquatic plant growth was significantly related to Secchi disk transparency (R2 = 0.67; p < 0.0001), color (R2 = 0.41; p < 0.0001), chlorophyll (R2 = 0.30; p < 0.0001), total phosphorus (R2 = 0.42; p < 0.0001), and total nitrogen (R2 = 0.33; p < 0.0001).

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1 CHAPTER 1 INTRODUCTION The distribution and abundance of aquatic macrophytes in lakes are affected by many forces including but not limited to pressure (Hutchinson 1975), substrate characteristics (Bachmann et al. 2001) a nd lake morphology (Dua rte and Kalff 1986), water column nutrient con centrations (Jupp and Spence 1977), waterfowl grazing (Weisner et al. 1997), and light availability (Chambers and Kalff 1985; Canfield et al. 1985). Given the high attenuation of irradian ce through the water column, and because plants require light to photosynt hesize, it is not surprising that light availability is often considered one of the most important factor s that regulate abundan ce and distribution of aquatic macrophytes (Zimmerman et al. 1994). The maximum depth at which autotrophic a quatic plants grow has been shown to be linearly related to transparency of th e water in numerous studies (Maristo 1941; Canfield et al.1985; Hudon et al. 2000). Chambers & Kalff (1985) found the maximum depth of colonization (MDC) for charophytes on average to occur at 11% of the surface incident irradiance. For angiosperms and bryophytes, they found MDC to be 21% of the surface irradiance. However, aquatic plants ha ve been recorded in areas receiving less than 1 and 2% of the surface irradiance (Hutchinson 1975). Canfield et al. (1985) demonstrated a re lationship between water transparency as measured by a Secchi disc (SD) and the maximum depth of macrophyte colonization in 26 Florida lakes. They also developed an empirical model for the relationship and suggested the model could provide lake ma nagers with a first approximation of how

PAGE 10

2 changes in SD values caused by either natura l or anthropogenic activities might affect the extent of macrophyte colonization in lakes. However, they cautioned lake mangers that, in using the model, other environmental f actors (e.g., types of plants present, basin morphometry, sediment types) besides SD valu es need to be considered to enhance the predictive ability of the model. In the 1990s, the Florida Legislature directed the stateÂ’s water management districts to establish minimum water levels for la kes (Section 373.042, Florida Statutes). The Southwest Florida Water Management Dist rict (SWFWMD) deve loped methods for establishing minimum lake levels (Chapter 40D-8. Florida Administrative Code), which included use of the model developed by Canfield et al. (1985) to assess potential changes in the coverage of submersed vegetation w ith changes in water transparency. The Southwest Florida Water Management District however, recognized the need to try to develop a more robust model from a larger number of lakes. This study was designed based on the earlier wo rk of Canfield et al. (1985) in an attempt to develop more robust model/models for use by SWFWMD. The first part of the study involved the sampling of 32 Florida la kes. At each lake, environmental factors such as water chemistry, photosynthetically active radiation (PAR), and bottom slopes were measured to determine if the maximu m depth of macrophyte colonization could be better predicted than re lying solely on SD transparency. The second phase of this study used information collected by Florida LAKE WATCH on a large number of Florida lakes to develop a series of models to pred ict the maximum depth of colonization of macrophytes and establish a model wh ere the maximum depth of macrophyte colonization in Florida lake s should be limited by light.

PAGE 11

3 CHAPTER 2 MATERIALS AND METHODS Two data sets were used for model deve lopment. The first part of the study involved field sampling of 32 Florida lakes usin g the basic approach of Canfield et al. (1985). Study lakes selected we re located in eight counties, with the majority located in peninsular Florida (Figure 2-1). Lakes lo cated in the SWFWMD comprised 38% of the sampled lakes. Each lake was sampled once between May and December of 2004. At each study lake, four straight tran sects were established to provide an assessment of macrophyte coverage. A Raythe on DE-719 fathometer was used to detect the MDC for the macrophyte community along e ach transect. Buoys were placed at locations of measured macrophyt e MDC. After all transects were completed, the three to four deepest buoy stations were checked w ith a toothed hook (18 cm by 18 cm) for the presence of submersed aquatic macrophytes. At stations where the MDC was identified, measurements were made for SD transparency, light attenuation (E), true color, sediment type, and bottom slope, and the plant species were identified In some lakes with sparse plant growth, fewer than three stations were found harboring submersed a quatic macrophytes. At these lakes, open water stations were sampled for SD transparen cy, light attenuation (E ), true color, and sediment type. The variables that had quantitat ive values (i.e., SD transparency, E, color, and slope) were averaged by lake for the da y sampled, and because lakes were visited only once during the study, each lake is c onsidered the experimental unit for the quantitative variables. On the other hand, th e experimental unit for qualitative variables,

PAGE 12

4 such as plant type [i.e., the inclusion or exclusion of the plants being a hydrilla ( Hydrilla verticillata Royle) versus non-hydrilla species a nd being an angiosperm versus a charophyte] or sediment type (i.e., organic, sa ndy, mixed) was considered to be the lake stations. At each of the 32 study lakes, water tran sparency was measured where the MDC occurred by the use of a Secchi disc on the shady side of the boat. If the Secchi disc was visible on the bottom for all three stations, an additional Secchi reading was taken in a deeper location to use for analysis. Surface and corresponding underwater light irradiance were measured (in quanta un its) on the sunny side of the boat using a photometer (LI-COR model LI-140 0 data logger) with a quantum sensor that was placed both above (LiCor 193) and below (LiCor 192) the water. Light meter readings were taken at two to three depths. If possible, li ght measurements at each station were made at depths of one, two, and three meters to better represent light attenuation for the entire water column. An additional open-water light reading was taken in deeper water at some lakes where all three stations were shallow (l ess than 3 meters) or when sun coverage was fading and no stations had yet been sampled for light. Light readings were averaged over ten seconds to mitigate instantaneous fluctu ations with light intensity. The downward attenuation coefficient values for each station were calculated as the slope of the graph of the natural logarithm of the i rradiance values, corrected for changes in incident irradiance on the y-axis, against depth on the x-axis (Li nd 1974). The percent of surface irradiance penetrating at MDC was calcula ted using the relationship: IZ / Io = 100e-Ez, where IZ / Io = percent of subsurface irradiance, E = light attenuation coefficient and z = the maximum depth of plant colonization (Scheffer 1998).

PAGE 13

5 Color samples were collected at the surface (0.5 m) with 250-mL, acid cleaned, triple-rinsed, Nalgene bottles and immediatel y placed on ice until they could be put in a freezer to await analysis. True color values were determined fo llowing filtration through a Gelman type A/E glass fiber filter, centrifugation of the filtrate, and using the platinumcobalt standard technique determined by spectroscopy (Bowling et al. 1986). A ponar dredge with a 15 cm opening was used to obtain soil samples. Sediment type was classified as one of three types: sandy, organic, or mixed. Soil samples that were dark colored and slippery to the touc h were classified as organic while white, granular soil samples were cl assified as sandy, and a blend of organic and sandy soil was categorized as a mixed soil. Bottom slope was calculated around MDC statio ns and not the entire littoral area. Slope was calculated from the Raytheon DE -719 fathometer chart by dividing the rise (the change in water depth) by the ho rizontal distance across the station. For the 32-lake study, regression equations a nd coefficient of determination values (R2) were calculated using SD and E readings as the independent variables in order to predict the maximum depth of submersed macrophyte colonization. Multiple regression analysis was used to relate SD, E, and MDC to color and chlorophyll. Chlorophyll concentrations were obtained from the Flor ida LAKEWATCH database Best fit linear regressions were calculated betw een SD and E and vise versa. A t-test was used to test whether there was a significant difference in th e average percent of incident light at the maximum depth of colonization between stat ions with hydrilla versus non-hydrilla and between stations harboring angiosperms ve rsus charophytes. To investigate soil influence on MDC, an ANOVA was used to te st for differences in the mean depth of

PAGE 14

6 plant growth for the three soil types. Also, the coefficient of determination was calculated for the relationship between sl ope and MDC (McClave and Sincich 2000). The statistical software package JMP version 4.0 was used for sta tistical analysis and Kaleidagraph version 3.6 was used to generate linear regression figures. The second part of this study involved obtaining information on 187 lakes which had their macrophyte communities sampled by Florida LAKEWATCH. The lakes were sampled between 1991 and 2004. The water chemis ty data were represented as yearly averages and although most lakes were samp led only once, some lakes were sampled multiple times providing 279-lake-years of information. Florida LAKEWATCH is a volunteer citizensÂ’ lake monito ring program in which volunteers take measurements at three mid-lake locations, usually on a mont hly basis, for total phosphorus (TP), total nitrogen (TN), chlorophyll, and SD transp arency. The 187 lakes were located in 24 counties (Figure 2-1) and 35% of the lakes were in the SWFWMD. For the 279-lake-year study, Florida LAKEWATCH provided 250 Raytheon DE719 fathometer chart papers that were late r examined for the maximum point of plant colonization. The 32-lake study provided an additional 29 Raytheon DE-719 fathometer chart papers. Secchi disk readings and true color samples were obtained using the same procedures as the 32-lake study. Surface (0.5 m) water samples for measuring chlorophyll were collected in 4-L, tap-water rinsed, plastic milk jugs and placed in coolers until the samples could be filtered. A measured volume of water was filtered through a Gelman Type A-E glass fiber filter. Filters where folded and placed inside a larger paper filter and then stored inside a silica gel desiccant bottle in a freezer.

PAGE 15

7 Chlorophyll was extracted from th e filters in hot ethanol (Sartory and Grobbelarr 1984). The trichromatic equation for chlorophyll a was used to calculate the concentrations of chlorophyll with the ho t ethanol method (Method 10200H; APHA 1992). Water samples for TP and TN were collected at the surface (0.5 m) with 250-mL, acid cleaned, triple-rinsed, Nalgene bottles. Water samples were immediately placed and held on ice until returned at the end of the sampling day to the Florida LAKEWATCH water quality laboratory in Gainesville, Florid a. At the laboratory, water samples were frozen until being analyzed by Florid a LAKEWATCH staff. Total phosphorus concentrations were determined using the methods of Murphy and Riley (1962) with a persulfate digestion (Menzel and Corwin 1965) Total nitrogen concentrations where determined by the oxidization of water sample s using persulfate and determining nitratenitrogen with second derivative sp ectroscopy (D'Elia et al. 1977). Data (i.e., SD transparency, color, chlo rophyll, TP, and TN) obtained from Florida LAKEWATCH were averaged for the year in whic h plants were inventoried at each lake. For each lake, Florida LAKEWATCH means we re first averaged for the day of the month sampled and these monthly means were averaged together for a yearly mean for the lake. Some lakes were represented in the data set more than once if they were sampled multiple years. If Florida LAKEWATCH was missing wate r chemistry data for the corresponding year that the lake was measur ed for MDC, long-term water chemistry means for that lake were used. Long-term means were computed by averaging all yearly means for a lake. For the 279-lake-year study, long-term values us ed represented 5% of SD transparency readings, 43% of color measurements, a nd 2.5% of chlorophyll, TP, TN values.

PAGE 16

8 An empirical model was developed using the Florida LAKEWATCH database relating SD transparency to the maximum de pth of submersed vegetation in order to increase the representation of Florida lakes. A maximum line relating MDC and SD was also determined by sorting the 279 SD values from lowest to highest and then dividing these into 10 groups. Because 279 is not divi sible by 10, there were 28 SD values in each of the first nine groups, and one group of 27 SD readings. The maximum MDC value in each group with its associated SD value was used to run a regression through the 10 pairs of points Linear and multiple regression models were created to quantify the relationship of MDC to color and chlorophyll because these two light-reducing variables have been shown to be hyperbolically rela ted to SD depth (Can field and Hodgson 1983). Furthermore, because TP and TN have been shown to be positively related to chlorophyll concentrations (Canfield 1983), these nutrients were also examined mathematically with respect to the maximum depth of submersed plant colonization. To meet the assumption of normality, prior to statistical analysis, all distributions were transformed to a base 10 logarithm. A software program, Kaleidagra ph version 3.6, was used to generate figures and JMP version 4.0 was used to perform statis tical tests. The alpha level of rejection was set at 0.05.

PAGE 17

9 Figure 2-1. Locations of lakes sampled for both studies.

PAGE 18

10 CHAPTER 3 RESULTS AND DISCUSSION Canfield et al. (1985) sampled 26 Florid a lakes with SD transparencies ranging from approximately 1 m to about 6.3 m. For the 32-lake study, there was a wide range in SD transparency from 0.3 m to 5.8 m. The mean transparency for all lakes was 1.8 m. The other measured limnological paramete rs in the 32-lake study also varied considerably. Measured light extin ction coefficients ranged from 0.2 m-1 to 6.8 m-1 (mean for all lakes 1.8 m-1). True color ranged from 2 PCU to 385 PCU (mean color 50 PCU). The calculated bottom slopes ranged fr om 0.3% to 13% (mean slope 4%). The maximum depth of plant colonization ranged fr om 0.7 m to 9.2 m, with mean depth of aquatic macrophyte growth at 3.1 m (Table 3-1). Canfield et al. (1985) found a significa nt positive relationship between the MDC and SD depth (R2 = 0.49) using data from Finnish, Florid a, and Wisconsin lakes. For the 32 Florida lakes sampled during this st udy, there was also a significant positive relationship between the MDC and SD depth (R2 = 0.46; p < 0.0001; Figure 3-1A). The best fit equation between MDC and SD fo r the Canfield et al. 1985 study was: log ( MDC ) = 0.61 log ( SD ) + 0.26 ( 3-1) The equation between MDC and SD for the 32 Florida lakes was: log ( MDC ) = 0.64 log ( SD ) + 0.30 (3-2) where MDC and SD are expressed in meters. Both equations are similar and provide evidence that the positive relationship between MDC and SD is repeatable.

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11 Canfield et al. (1985) found light meter readings were highly correlated (r = 0.96) to concurrently measured SD values. Most light reaching the water surface is reflected, turned to heat, or absorbed by objects in the water column as well as by the water itself (Cole 1983). The intensity of light in the water column (Iz) decreases exponentially with depth (z) depending on the vertical attenuati on coefficient (E) of the water and the starting surface illumination (Io), using the relationship set forth in Beers law: Iz = Io e-Ez (Scheffer 1998). Wavelengths are absorbed differentially in the water column with infrared light and many of the visible reds be ing absorbed mostly in the first meter and with blues penetrating the deepest (Cole 1983) Additional substan ces in the water--dissolved organics (color), algae, and nonalgal suspended solids--influence the amount of light penetration through the water column (Haven s 2003), and potential SD values. Light availability to a depth in the wate r column can be measured directly by the use of a light meter or indirectly by the us e of a SD. For the English Channel, the relationship between light attenuation (E) a nd SD measurements was E =1.7 / SD (Poole and Atkins 1929). However, the relations hip between E and SD varies among studies and many alternatives have been suggeste d (Holmes 1970; Walker 1980). For the 32 study lakes, the correlation between the measur ed light attenuation coefficients and SD was significant, but not as str ong (r = 0.81) as that reported (r = 0.96) by Canfield et al. (1985). Color and chlorophyll concentrations were also highly related to SD depth (R2 = 0.71; p < 0.0001), light attenuation (R2 = 0.74; p < 0.0001), and MDC (R2 = 0.65; p < 0.0001) through multiple regression analysis (Tab le 3-2). Secchi disk transparency, however, can be predicted reasonably well fr om measured light attenuation coefficients (Figure 3-2A) using the equation:

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12 log ( SD ) = -0.69 log ( E ) + 0.26 (3-3) and light attenuation coefficient (E) can be predicted from SD (Figure 3-2B) using the equation: log ( E ) = -0.96 log ( SD ) + 0.30 (3-4) where SD is in meters and E is per meter. Although E and SD are highly correlate d, the large 95% confidence limit (46236%) associated with the MD C-SD model published by Canfie ld et al. (1985) has lead to speculation that the use of light meter r eadings could lead to the development of a more robust model. The MDC of macrophyt es in the 32-lake study was negatively related to the mean light attenuation coeffi cient (Figure 3-1B) and the relationship was represented by the following equation: log ( MDC ) = -0.51 log ( E ) + 0.48 (3-5) where MDC is in meters and E is per meter. Light attenuation, however, did not predict MDC any better than SD transparency and act ually had a slightly lower coefficient of determination (R2 = 0.41) than SD readings (R2 = 0.46). This finding demonstrated SD, an easily measured and inexpensive index of water transparency, is as useful for assessing MDC as E values that require th e use of complex and expensive equipment. Canfield et al. (1985) suggested the major factor contributing to the variability in the MDC-Secchi relationship is the type of plant colonizing the lake bottom because different species of plants ha ve different light requirements The amount of surface light penetrating at the maximum depth at which submersed aquatic macrophytes colonized in the 32 study lakes ranged from < 1% to 47%. The mean percent of in cident light at the maximum depth of colonization was 11%, which was in agreement with much of the

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13 literature (Table 3-1). For example, Hoyer et al. (2004) found that when the percent of incident light at the surface reaching the s ubstrate was less than 10%, there was little or no submersed aquatic vegetation biomass. Sheldon and Boylen (1977) found the MDC to correspond to 10% of the light intensity hitting the surface. The mean percent of incident light at the maximum depth of colonization for stations with hydrilla, non-hydrilla angiosperms, and charophytes present in this study was 19%, 10%, 12%, and 7%, respectively (Table 3-1). Although hydrilla has been shown to have low light requirements in laboratory conditions (Van et al. 1976), for the 32 lakes examined in natural conditions, hydrilla was not found at lo w light levels. Ther e was no significant difference in percent of inci dent light at the maximum de pth of colonization between hydrilla and non-hydrilla species (p = 0.2). Similarly, th ere was no significant difference of mean percent surface pene tration present at the dept h of maximum plant growth between angiosperms and charophytes (p = 0.4). This indicates that for this group of Florida lakes, differences in the light require ments of individual plant types can not be invoked as the major factor contributing to the variability in the MDC-Secchi relationship. Lake bottom sediment serves not only as a physical anchor for submersed vegetation but also as a source of nutrients (Barko et al. 1991 ). Bachmann et al. (2001) suggested the flocculent orga nic sediments in Lake Apopka were deleterious for root anchorage and limited the col onization of submersed aquatic macrophytes. Lake Apopka sediments, however, are unique and the lake was not included in the 32-lake study. For the 32-lake study, the mean MDC for organic, mixed, and sandy soils were 2.9 m, 3.7 m, and 2.7 m, respectively. There was no signifi cant difference in the maximum depth of

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14 plant colonization among the three soil types classifications established in this study (p = 0.07). Soil type, therefore, wa s not shown to have a significant effect on the maximum depth of plant growth. However, the means we re close to be signifi cantly different with the mixed soil having the largest mean MDC, suggesting that mixed soil tends to promote plant growth in deeper waters. As early as 1924, H. W. Rickett noticed th at aquatic vegetation grew deeper in lakes possessing gentle slopes and shallower in lakes having steeper slopes. Duarte and Kalff (1986) demonstrated a strong influence of littoral bottom slope on the maximum biomass of aquatic macrophyte communities. However, they pointed out that the model generated in their study did not reflect turbid lakes (i.e., Secchi disk readings < 2 m), where irradiance rather than sl ope is pre-eminent. The mean SD transparency for the 32 lakes was 1.8 m; therefore littoral bottom slope according to Duar te and Kalff (1986) should not greatly influence MDC in Florida la kes. In another study by Duarte and Kalff (1990), they found that 15% was the steepest slope at which aquatic macrophytes were present and able to grow. All of the lakes in the 32-lake study had slopes less than 15%. Lake bottom slope was not significantly rela ted to the maximum depth of submersed plant colonization (R2 = 0.03; p = 0.35; Table 3-3) so slope is not a variable that can be used to improve the MDC-Secchi relationship in Florida. Although slope has been found to affect aquatic plant growth in other studies it seems plausible that slope has a minimal influence on MDC for many of Florida lakes be cause they are generally shallow, with a majority of them having mean depths less th an 5 meters (Florida LAKEWATCH 2003). Florida lakes display a wide range of limnological conditions (Canfield and Hoyer 1988). Information on MDC, SD, and other water chemistries were obtained from

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15 Florida LAKEWATCH to examine the MDC-S ecchi relationship for a wide range of lakes. For the 279-lake-year study, MDC ra nged from 0.7 m to 9.2 m. The mean MDC depth was 3.3 m. Secchi disk transparency ranged from 0.2 m to 8.2 m (mean of 2.2 m). Color values ranged from 0 PCU to 430 PCU, w ith the mean color for all lakes equal to 50 PCU. The minimum and maximum ch lorophyll concentrations were 0.5 g /L and 292 g /L, respectively, and the overall mean was 17 g /L. Total phosphorus and TN concentrations ranged from 2.1 g /L to 402 g/L and 43 g/L and 4550 g/L, respectively, and averaged 28 g /L and 764 g/L, respectively (Table 3-4). For the 279-lake-year study, there was as significant positive relationship between SD and MDC (R2 = 0.67; p < 0.0001; Figure 3-3). The be st fit MDC-SD regression line was: log ( MDC ) = 0.66 log ( SD ) + 0.30 (3-6) where MDC and SD are expressed in meters. Equation 3-6 is essentially the same as the regression equations developed by Canfield et al. (1985) (Equati on 3-1) and by my 32lake study (Equation 3-2). This strongly sugge sts the MDC-SD relati onship is applicable to a wide range of lakes. Inspection of Figure 3-3 clearly shows that for a given SD there is considerable variability in the measured maximum depth of macrophyte colonization. This is evidence that other environmental factors besides wate r transparency influence MDC. However, there is a clear upper limit for MDC at various SD levels. This upper limit represents where light is the limiting environmental f actor and can be described by the following equation: log ( max MDC ) = 0.52 log ( SD ) + 0.59 (3-7)

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16 where MDC and SD are expressed in meters. When MDC values falls below the line, there is some other limiting environmental factor other than solely lig ht that is inhibiting plant growth. Because SD readings were rela ted to the measured color (R2 = 0.49) and chlorophyll samples (R2 = 0.59), these two light reducing variables were quantifiably related to the maximum depth of submerse d plant colonization. Moreover, because chlorophyll readings we re related to TP (R2 = 0.69) and TN (R2 = 0.53), regression models were developed to re late these nutrients to the maximum depth of submersed macrophyte colonization. Therefore, the de pth at which plants colonized was also significantly inversely related to color (R2 = 0.41; p < 0.0001), chlorophyll (R2 = 0.30; p < 0.0001), TP (R2 = 0.42; p < 0.0001), and TN (R2 = 0.33; p < 0.0001). The light attenuating substances, colo r and chlorophyll, were inve rsely related to MDC through multiple regression analysis (R2 = 0.52; p < 0.0001). Given th e significant relationships between MDC and color, chlorophyll, TP, and TN, it is possible to provide a basic assessment of the potential effects of th ese variables on macrophyte colonization in Florida lakes even without measurements of SD or E. Table 3-1. Descriptive statistics for the ma ximum depth of plant colonization (MDC in meters), Secchi disk (SD in meters), light attenuation coefficient (E in m-1), percent of subsurface irradiance penetra tion (Iz / Io in %), color (PCU), and slope (%) for the 32-lake study. Parameter n Minimum Maximum Mean Standard deviation MDC 32 0.7 9.2 3.1 1.8 SD 32 0.3 5.8 1.8 1.2 E 32 0.2 6.8 1.8 1.5 Color 32 2 385 50 70 IZ / Io 32 0.008 47 11 14 IZ / Io hydrilla 9 0.43 99 19 33 IZ / Io Non-hydrilla 72 0.0003 78 10 16 IZ / Io Angiosperm 68 0.0003 99 12 20 IZ / Io Charophyte 13 0.02 19 7 6 Slope 31 0.3 13 4 3

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17 Figure 3-1. Relationship between the mean maximum depth of submersed macrophyte colonization and mean Secchi disc dept h (A) and mean light attenuation (B).

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18 Table 3-2. Multiple regression equations re lating Secchi disk (SD in meters), light attenuation coefficient (E in m-1) and the maximum depth of plant colonization (MDC in meters) to color (P CU) and chlorophyll (CHL in g/L). n Equation R2 p value 29 log(SD) = -0.25 log(COLOR) – 0.39 log(CH L) + 0.88 0.71 < 0.0001 29 log(E) = 0.52 log(COLOR) + 0.22 log(CHL) – 0.82 0.74 < 0.0001 29 log(MDC) = -0.27 log(COLOR) -0.35 log(CHL) + 1.11 0.65 < 0.0001 Figure 3-2. Relationships between mean Secchi disc depth and mean light attenuation (A, B).

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19 Table 3-3. Mean maximum depth of plant colonization (MDC in meters) and slope values by lake and the relations hip between MDC and mean slope. Lake County MDC Slope Alligator Lake 2.6 0.04 Alto Alachua 2.5 0.02 Bay Marion 1.97 0.02 Beakman Lake 3.4 0.01 Bellamy Citrus 0.72 0.04 Brant Hillsborough 1 0.03 Church Hillsborough 2 0.06 Conway North Orange 5.5 0.05 Conway South Orange 5.83 0.04 Dodd Citrus 1.03 0.10 Doe Marion 4.23 0.03 Farles Prairie Lake 4.57 0.05 Grasshopper Lake 2.25 0.02 Hampton Bradford 1.73 0.01 Hernando Citrus 2.27 0.03 Ivanhoe East Orange 2.17 0.07 Little Conway Orange 5.57 0.03 Little Santa Fe Alachua 2 0.01 Magdalene Hillsborough 3.57 0.02 Maurine Hillsborough 1.2 0.04 Melrose Bay Alachua 2.87 0.07 Mill Dam Marion 2.73 0.03 Newnan Alachua 0.65 0.003 Osceola Hillsborough 3.5 0.07 Santa Fe Alachua 3.87 0.02 Sellers Lake 9.2 Starke Orange 1.5 0.13 Stella Putnam 4.27 0.03 Taylor Hillsborough 3.1 0.03 Twin Hillsborough 2.65 0.05 Weir Marion 3 0.01 White Trout Hillsborough 4.8 0.07 Note: n = 31, R2 = 0.03, p value = 0.35.

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20 Table 3-4. Descriptive statistics for maxi mum depth of plant colonization (MDC in meters), Secchi disk (SD in meters), color (PCU), chlor ophyll (g/L), total phosphorus (TP in g/L), and total nitrogen (TN in g/L). Parameter n Minimum Maximum Mean Standard deviation MDC 279 0.7 9.2 3.3 1.9 SD 279 0.2 8.2 2.2 1.5 Color 263 0 430 50 69 Chlorophyll 279 0.5 292 17 34 TP 279 2.1 402 28 40.5 TN 279 43 4550 764 601.2 Figure 3-3. Comparison of a calculated maximu m line to the best-fit line relating yearly Secchi disk depth to the maximu m depth of plant colonization. Table 3-5. Regression equations of the maxi mum depth of submersed plant colonization (MDC in meters) related to color (PCU ), chlorophyll (CHL in g/L), total phosphorus (TP in g/L), and total nitrogen (TN in g/L). Input variable n Equation R2 p value SD 279 log(MDC) = 0.66 log(SD) + 0.30 0.67 < 0.0001 COLOR 262 log(MDC) = -0.29 log( COLOR) + 0.85 0.41 < 0.0001 CHL 279 log(MDC) = -0.28 log(CHL) + 0.71 0.30 < 0.0001 TP 279 log(MDC) = -0.43 log(TP) + 0.99 0.42 < 0.0001 TN 279 log(MDC) = -0.48 log(TN) + 1.79 0.33 < 0.0001 COLOR & CHL 262 log(MDC) = -0.22 log(COLOR) 0.18 log(CHL) + 0.93 0.52 < 0.0001

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21 CHAPTER 4 CONCLUSION For this study, the maximum depth inhabite d by an angiosperm was found at 9.2 m. This was similar to the comments of Hutchi nson (1975), which concluded that, in lakes, most angiosperms are limited to depths of 9 m. There have, however, been a few exceptions of extreme deep water expansion by freshwater angiosperms. For example, Sheldon and Boylen (1977) found Elodea canadensis growing to depths of 12 m in Lake George, New York and Hydrilla verticillata has been found growing to a depth of 15 m in Crystal River (Langeland 1996). This study has confirmed the findings of Ca nfield et al. (1985) that the maximum depth of macrophyte colonization can be predic ted using SD transparency. Furthermore, the maximum depth of plant growth can be predicted reasonably well by light meter measurements. The mean percent of incide nt light at the maxi mum depth of plant colonization was 11% for the Florida lakes studied, which was in agreement with much of the primary literature. Although plant sp ecies, sediment type and slope have been shown to influence aquatic plant growth on an individual lake basis, no significant influences on MDC were found in this st udy when looking among lakes. When those variables (plant species, sediment types, slope) where taken into account, they did not increase the predictive capabilities of the Canfield et al. SD-MDC model. Although this study represents a more compre hensive research effort than those of Canfield et al (1985) to identify and quantif y the environmental determinants of MDC, the findings, nevertheless offer no improvement on the predictive value offered by the

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22 SD measurements reported in that study This suggests that light attenuation, as quantified by SD sampling, is the most important environmental factor in determining MDC. Still, there is substa ntial variability in SD-MDC correlates from one site to another, suggesting that other factors play a causal role. It is possible that much of the variability in the MDC-SD model is due to fluctuations in lakes levels that prevent plant depth from attaining a state of equilibrium. Furthermore, light regimes fluctuate thr ough time causing oscillation in the equilibrium depth at which plants grow. For the 279-la ke-year study, the use of yearly average SD readings helped account for the changing light regimes in which the plants had been growing and to which they were responding th at year, whereas only daily SD readings were used in the 32-lake study. It is significant, therefore, th at if yearly SD transparency values from the Florida LAKEWATCH databa se were used to replace the daily SD values for the 32-lake study, the yearly SD -MDC model accounts for more variablility (R2 = 0.57) than the one using the daily SD values (R2 = 0.46). Obviously, when herbicides are used or wh en grass carp are released into a lake, the depth of plant growth should diminish and could cause lakes to de viate below the best fit SD-MDC line. When the Hernando Chai n of Lakes in Citrus County was visited during the 32-lake study, the water was being sprayed with a herbicide and an island was being built. Many of the areas visited in th is chain had the presence of freshly killed plant material, indicative of continue d plant maintenance control. There are innumerable possible combina tions of environmental variables for a specific site over the course of time and this introduces the elem ent of unquantifiable chance into any predictive value for response by a resident organism The inability of

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23 this current research effort to isolate other specific factors as core determinants makes it seem likely that the range of variation in MDC response from site to site is to be expected. In the final analysis this simply represents a meas urable variation in response to an immeasurably complex inte raction of environmental factors An upper limit line relating MDC to SD was developed and describes light limitation when the MDC response falls on or near the response curve and when MDC values fall below the line, there is some other limiting environmenta l factor. Managers should recognize that the maxi mum MDC model predicts th e upper limit of deepwater growth, but other factors will routinely result in the actual depth of plant colonization less than predicted. The other water chemistry parameters ex amined (color, chlorophyll, TP, and TN) were found to provide reasonable estimate s for predicting the potential depth of macrophyte growth and could be particularly usef ul when SD transparency or E of a lake is unknown. Managers should assess each lake independently and consider what water chemistry variable is the dominant factor in fluencing plant growth. For example, true color would be the best tool to use fo r predicting MDC for a dystrophic lake. Submersed aquatic macrophytes play an inte gral role in the functioning of lake processes, therefore, it is important for managers to understand how submersed plants will respond to changes in lake conditions, such as eutrophication or altered water levels. These models allow managers to assess potenti al changes in plant coverage that might result from changes in light and water chemistry variables.

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APPENDIX A 32-LAKE STUDY DATA

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25Table A-1. Maximum depth of plant colonizatio n (MDC in meters), Secchi disk transpar ency (SD in meters), top, middle, and bott om depths that the light meter was measured (Z top, Z middle, Z bottom in meters), top, middl e, and bottom deck cell light readings (deck top, deck middle, deck bottom in mol s1 m-2 per A), and top, middle, and bottom underwater light readings (Iz top, Iz middle, Iz bottom in mol s-1 m-2 per A), color (PCU), so il type, and plant species identification by station (buoy number) at 32 Florida lakes sampled in 2004. Date Lake County Buoy MDCSD Z top Deck topIz top Z middle Deck middle Iz middle Z bottom Deck bottom Iz bottom Color Soil type Species 10/29/04 Alligator Lake 2 2.6 1 0.6 1427 109.3 1.2 947 30.27 2.1 1306 16.41 65 Or ganic Hydrilla verticillata 10/29/04 Alligator Lake 3 2.5 1 0.6 1359 193.4 1.2 1330 50.59 2.1 1224 15.64 63 Or ganic Hydrilla verticillata 10/29/04 Alligator Lake 6 2.7 0.9 0.6 1367 270.2 1.2 1366 63.79 1.8 1357 34.94 69 Or ganic Hydrilla verticillata 10/22/04 Alto Alachua 2 4.3 0.8 0.5 1288 117.2 1 1320 28.66 1.5 1301 6.3 150 Mix Eleocharis baldwinii 10/22/04 Alto Alachua 6 1.8 0.8 0.75 825 38.95 1.5 1073 5.59 2.3 831.8 0.55 152 Mix Eleocharis baldwinii 10/22/04 Alto Alachua 8 1.4 0.75 0.3 1016 115.6 0.6 773. 3 39.99 0.9 1049 20.15 147 Mix Eleocharis baldwinii 08/11/04 Bay Hillsborough 2 2.9 1.5 1 1895 247.7 2 1893 12.47 2.5 1829 3.24 38 Organic Chara sp. 08/11/04 Bay Hillsborough 3 0.9 B 0.2 1705 1190 0.4 1739 831.2 0.6 1808 609.8 35 Sandy Chara sp. 08/11/04 Bay Hillsborough 4 2.1 B 0. 2 1233 711.2 0.5 1767 677.2 1 1738 374. 7 34 Organic Chara sp. 08/11/04 Bay Hillsborough OWL1 . 1 1727 415.9 2 1734 93.2 2.5 1823 49.68 . 08/3/04 Beakman Lake 3 3.7 B 1 1088 0.13 1.5 1844 0.28 2 2109 0.08 13 Sandy Websteria confervoides 08/3/04 Beakman Lake 5 3.1 B 0.5 1678 808.4 1 1694 825. 6 1.5 1727 485.2 17 Sandy Websteria confervoides 08/3/04 Beakman Lake 6 3.4 B 1 1374 26.38 1.5 1850 42.8 2 1850 24.48 19 Sandy Websteria confervoides 08/3/04 Beakman Lake SD 3.5 . . . . . . 10/16/04 Bellamy Citrus 3 1.3 1.25 0.5 1569 403.6 1 1423 171. 3 1.4 1674 86.35 61 Organic Bacopa caroliniana 10/16/04 Bellamy Citrus 5 0.8 1.75 0.4 1643 472 0.8 1616 318.3 1. 2 1564 179.9 61 Organic Hydrilla verticillata 10/16/04 Bellamy Citrus 6 0.2 1.5 0.5 1567 501.4 1 1569 77.87 1.5 1574 46.46 61 Organic Bacopa caroliniana 10/16/04 Bellamy Citrus OWL1 . 1 1638 238.7 2 1648 47.23 3 1566 7.86 .

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26Table A-1. Continued. Date Lake County Buoy MDCSD Z top Deck topIz top Z middle Deck middle Iz middle Z bottom Deck bottom Iz bottom Color Soil type Species 06/23/04 Brant Hillsborough 2 1 B 0.5 1559 0.26 0.7 1552 0. 22 . 88 Mix Bacopa caroliniana 06/23/04 Brant Hillsborough OW1 1 1 1473 121 1. 5 1525 47.14 2 1572 15.93 89 Organic 06/23/04 Brant Hillsborough OW2 1.25 0.2 1728 684.4 0.4 1637 401. 6 0.6 1721 302.6 89 Organic 08/4/04 Church Hillsborough 1 2 1.5 0.5 2014 849.3 1 2028 516.2 1.5 2005 301.6 28 Mix Chara sp. 08/4/04 Church Hillsborough OW1 1.25 1 1585 492.1 2 1616 149.2 2.5 1580 82.22 31 Mix 08/4/04 Church Hillsborough OW2 1.5 1 2357 566 2 2378 199.1 3 2359 47.66 25 Mix 11/20/04 Conway North Orange 3 5.1 3 1 565.7 160.5 2 559.3 86.14 3 541.4 47.57 7 Mix Vallisneria americana 11/20/04 Conway North Orange 6 5.8 2.6 1 670.9 184.9 2 645.4 100.4 3 646 32.31 8 Mix Potamogeton illinoensis 11/20/04 Conway North Orange 9 5.6 2.75 1 757.3 231.1 2 721.2 107.7 3 699.4 60.76 9 Mix Potamogeton illinoensis 11/20/04 Conway North Orange OWL1 . 1 1384 653.1 2 1371 313.9 3 1370 178.3 . 11/20/04 Conway South Orange 4 5.7 2.5 1 1423 556.9 2 1401 277.6 3 1436 149.8 9 Mix Vallisneria americana 11/20/04 Conway South Orange 5 5.5 2.4 1 1637 578.5 2 1627 279.9 3 1642 146.3 8 Mix Vallisneria americana 11/20/04 Conway South Orange 8 6.3 2.6 1 1508 576.3 2 1647 313.7 3 1692 172.1 8 Mix Nitella sp. 10/16/04 Dodd Citrus 3 0.8 1.25 0.5 935.8 235.4 1 1032 113.9 1.5 1095 35.15 61 Sandy Ludwigia repens 10/16/04 Dodd Citrus 5 2.1 1.25 0.5 1173 149.1 1 1069 109. 1 1.5 1225 41.69 62 Organic Utricularia sp. 10/16/04 Dodd Citrus 6 0.3 1.5 0.4 1366 484.5 0.8 1368 449. 4 1.2 1374 221 63 Organic Hydrochloa caroliniensis 10/16/04 Doe Marion 3 4 3.5 1 1483 529 2 1485 250.9 3 1486 129.5 9 Mix Chara sp. 10/16/04 Doe Marion 5 4.4 3.5 1 1437 563.6 2 1427 220.5 3 1416 116.6 9 Mix Chara sp. 10/16/04 Doe Marion 8 4.3 3.5 1 1524 378.2 2 1566 92.13 3 1552 67.59 14 Mix Chara sp. 9/10/04 Farles Prairie Lake 2 4.9 3.25 1 787. 4 190.2 2 793.9 79.35 3 794 40.76 11 Sandy Myriophyllum heterophyllum 9/10/04 Farles Prairie Lake 7 4.2 3.75 1 1454 250. 1 2 1058 111.5 3 1055 54.57 12 Sandy Utricularia sp. 9/10/04 Farles Prairie Lake 8 4.6 3.25 1 635.9 194.6 2 630.6 74.38 3 626.1 33.09 12 Sandy Myriophyllum heterophyllum 8/6/04 Grasshopper Hillsborough 1 2.8 1.25 0.5 287.5 27.54 1 271.7 4.29 1.3 267.2 0.58 78 Sandy Websteria confe rvoides 8/6/04 Grasshopper Hillsborough 2 1.8 1 0.5 552.4 53.26 1 560.5 17.43 1.5 575 3.31 76 Sandy Utricularia sp. 8/6/04 Grasshopper Hillsborough OW2 1.5 0.5 1177 206.2 1 1158 13.59 1.5 1127 0.2 80 Sandy 8/6/04 Grasshopper Hillsborough OWL1 . 1 873.1 28.69 2 786.6 2.89 3 767.3 0.95 .

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27Table A-1. Continued. Date Lake County Buoy MDCSD Z top Deck topIz top Z middle Deck middle Iz middle Z bottom Deck bottom Iz bottom Color Soil type Species 10/22/04 Hampton Bradford 5 1.7 1 0.4 959.8 197.3 0.8 968.7 76.49 0.9 894.9 52.89 89 Sandy Websteria confervoides 10/22/04 Hampton Bradford 6 1.8 1 0.4 1231 189 0.8 1213 62.69 1.2 1262 40.78 91 Sandy Websteria confervoides 10/22/04 Hampton Bradford 9 1.7 0.8 0.5 1027 133.6 1 1029 53.67 1.4 1041 17.81 87 Sandy Websteria confervoides 10/16/04 Hernando Citrus 1 2.2 1.4 0.75 1067 95.33 1.5 1049 23.79 2.1 1047 1.24 61 Organic Ceratophyllum demersum 10/16/04 Hernando Citrus 2 2 1.5 0.6 1059 135.2 1.2 1054 22.92 1.8 977.5 7.27 62 Organic Ceratophyllum demersum 10/16/04 Hernando Citrus 4 2.6 1.75 1 986.5 79.77 2 970 9.65 2.5 934.2 4.26 56 Organic Ceratophyllum demersum 11/21/04 Ivanhoe Orange 2 2 1 1 1228 392.5 2 1236 150.60 3 1058 108.4 10 Mix Najas guadalupensis 11/21/04 Ivanhoe Orange 3 2.7 1 1 1150 325.4 2 1156 125.40 3 1150 62.35 11 Mix Vallisneria americana 11/21/04 Ivanhoe Orange 6 1.8 1.1 1 1113 214 2 1117 116.30 3 1116 52. 07 9 Sandy Vallisneria americana 11/20/04 Little Conway Orange 5 6.1 1.25 1 1356 293.8 2 1353 92.37 3 1328 30.61 14 Organic Vallisneria americana 11/20/04 Little Conway Orange 6 5.1 1 1 1197 176.6 2 1196 62.83 3 1176 23.21 12 Organic Hydrilla verticillata 11/20/04 Little Conway Orange 9 5. 5 1.75 1 1183 405.3 2 1169 145.60 3 1169 55. 37 12 Organic Hydrilla verticillata 10/18/04 Little Santa Fe Alachua 2 2 0.5 0.3 1257 49.92 0.6 1249 14.47 1.2 1275 0.98 375 Mix Eleocharis baldwinii 10/18/04 Little Santa Fe Alachua 4 2 0.5 0.2 1053 83.82 0.4 1191 28.53 0.6 1072 7.3 381 Mix Eleocharis baldwinii 10/18/04 Little Santa Fe Alachua OW1 0. 4 0.2 818.3 86 0.4 786.6 15.02 0.6 801.2 1.63 399 Mix 08/11/04 Magdalene Hillsborough 1 3.8 2 1 1961 502.5 2 1963 488.00 3 1921 15. 7 29 Organic Unidentified plant 08/11/04 Magdalene Hillsborough 2 3.6 1.75 1 1828 507.7 2 1883 206. 10 3 327.1 2.95 29 Organic Nitella sp. 08/11/04 Magdalene Hillsborough 6 3.3 1.6 1 2093 336.8 2 2094 424.80 3 2059 86. 54 43 Organic Najas guadalupensis 08/4/04 Maurine Hillsborough 1 1.3 B 0.2 1972 620.3 0.4 2064 439.40 0.6 2028 152.4 64 Sandy Bacopa caroliniana 08/4/04 Maurine Hillsborough 5 1 B 0.2 2010 814.8 0.4 2077 679.50 0.6 2052 397.8 64 Sandy Bacopa caroliniana 08/4/04 Maurine Hillsborough 7 1.3 B 0.3 1198 175.4 0.6 1306 109.80 0. 9 1480 85.01 65 Sandy Bacopa caroliniana 08/4/04 Maurine Hillsborough SD 1 . . . . . . 08/12/04 Melrose Bay Alachua 3 2.8 2 1 307. 6 49.92 2 300.9 0.18 2.5 291.8 0.15 27 Mix Mayaca fluviatilis 08/12/04 Melrose Bay Alachua 7 2.8 2 . . . . 27 Mix Mayaca fluviatilis 08/12/04 Melrose Bay Alachua 8 3 2 1 752.9 113.70 2 758.4 32.02 3 738. 3 18.44 26 Mix Mayaca fluviatilis 05/27/04 Mill Dam Marion 4 3 B 1 2031.0 403.20 2 2212 260.80 2.2 2210 323.1 14 Mix Mayaca fluviatilis

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28Table A-1. Continued. Date Lake County Buoy MDCSD Z top Deck topIz top Z middle Deck middle Iz middle Z bottom Deck bottom Iz bottom Color Soil type Species 05/27/04 Mill Dam Marion 7 2.8 3.05 1 588.3 146.7 2 597.9 99.55 3 1811 185.1 15 Sandy Mayaca fluviatilis 05/27/04 Mill Dam Marion 8 2.4 B 1 1878 290.6 2 2182 281.9 . 14 Sandy Mayaca fluviatilis 05/18/04 Newnan Alachua 3 0.9 0.3 0.5 2184 155.4 0.6 2179 106.6 . 112 Organic Ceratophyllum demersum 05/18/04 Newnan Alachua 6 0.4 0.3 0.5 2181 194.3 0.7 2286 90.45 . 96 Organic Ceratophyllum demersum 05/18/04 Newnan Alachua OW1 0.25 0.5 2098 19.37 0. 8 2098 1.16 1 2095 0.19 91 Organic 08/25/04 Osceola Hillsborough 2 3.3 2.1 1 1504 160.8 2 1549 99.87 3 1568 39.18 38 Organic Na jas guadalupensis 08/25/04 Osceola Hillsborough 4 3. 2 2.1 1 1778 389.3 2 1779 382.3 3 1781 53.89 35 Organic Hydrilla verticillata 08/25/04 Osceola Hillsborough 8 4. 0 2.1 1 1794 367.4 2 1732 107.2 3 1695 11.41 37 Organic Utricularia sp. 10/18/04 Santa Fe Alachua 1 3.5 1.4 1 1135 96.34 2 1162 17.47 2.5 1116 9.56 52 Organic Najas guadalupensis 10/18/04 Santa Fe Alachua 2 4.0 1.3 1 1205 103.6 2 1096 7.47 3 1039 3.65 54 Organic Najas guadalupensis 10/18/04 Santa Fe Alachua 3 4.1 1.4 1 999.9 100.7 2 995.2 17.27 3 971.8 0.79 52 Organic Najas guadalupensis 05/13/04 Sellers Lake 2 9.2 5.75 1 2327 1199 2 2335 1035 3 2270 729.9 2 Sandy Utricularia sp. 05/19/04 Starke Orange 1 1. 5 0.75 1 2011 499 1.5 694.6 54.58 . 14 Sandy Vallisneria americana 08/12/04 Stella Putnam 3 4.3 2 1 651.4 143.5 2 650.3 52 3 681.3 19.92 19 Mix Najas guadalupensis 08/12/04 Stella Putnam 7 4.1 2 1 1003 244.7 2 975.2 86.04 3 969.6 37.82 18 Mix Chara sp. 08/12/04 Stella Putnam 8 4.4 2 1 1014 282 2 1019 102. 4 3 989.8 43.92 21 Mix Najas guadalupensis 09/25/04 Taylor Hillsborough 1 3.1 1.5 1 1429 216.6 2 1428 206.5 2.5 1437 55.96 36 Or ganic Eleocharis baldwinii 09/25/04 Taylor Hillsborough OW1 1.5 1 1516 44.8 2 1516 41.3 3 1528 8.93 46 Organic 09/25/04 Taylor Hillsborough OW2 1. 5 1 1481 193.4 2 1480 57.97 3 1525 16.75 41 Organic 06/16/04 Twin Hillsborough 3 2.8 0. 5 1 472.3 28.87 2 474.4 3.13 . 15 Sandy Vallisneria americana 06/16/04 Twin Hillsborough 5 2.5 0.5 1 2028 74.64 . . . 14 Sandy Vallisneria americana 06/16/04 Twin Hillsborough OW1 0.5 1 1946 35. 37 2 2058 22.3 2.5 1956 11.06 16 Sandy 06/1/04 Weir Marion 1 2.9 1.5 1 2065 267.5 2 2118 137.9 2.5 2004 64.73 6 Sandy Nitella sp. 06/1/04 Weir Marion 6 2.8 1.4 1 2007 501.5 2 2064 284.2 2.5 2076 161.8 7 Mix Nitella sp. 06/1/04 Weir Marion 8 3.3 1.5 1 2104 664.9 2 2093 341.7 2.5 2122 296 8 Sandy Nitella sp. 06/16/04 White Trout Hillsborough 1 4. 0 3.5 1 477.7 129.5 2 575.1 77.86 3 511.9 50.1710 Organic Hydrilla verticil lata

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29Table A-1. Continued. Date Lake County Buoy MDCSD Z top Deck topIz top Z middle Deck middle Iz middle Z bottom Deck bottom Iz bottom Color Soil type Species 06/16/04 White Trout Hillsborough 2 5.5 B 0.5 447.4 150.3 0.7 451.3 135.4 0.9 455.4 122.4 10 Organic Vallisneria american a 06/16/04 White Trout Hillsborough 3 5.1 3 1 2153 194.2 2 2188 149.6 3 2184 196. 5 13 Mix Hydrilla verticillata 06/16/04 White Trout Hillsborough 4 4.6 2.75 1 2203 664.4 2 2215 224.7 3 1925 188.8 13 Mix Utricularia sp. Note: SD = Secchi disk transpar ency stations, OW = Open-water stations, OWL = Open-water light stations, B = Secchi disk was visible on lake bottom

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30 APPENDIX B 279-LAKE-YEAR STUDY Table B-1. Maximum depth of plant colonization (MDC in meters), yearly mean Secchi disk transparency (SD in mete rs), color (PCU), chlorophyll ( g/L), total phosphorus (TP in g/L), total nitrogen (TN g/L) for 279 Florida lake years sampled during 1991 to 2004. Year Lake County MDC SD Color Chlorophyll TP TN 1991 Alto Alachua 2.5 5.48 35.50 14.27 17.06 566.06 1991 Boll Green Putnam 4.1 9.60 7.00 1.90 7.40 204.29 1991 Chipco Putnam 3.9 8.16 8.13 3.05 8.19 245.71 1991 Clear Orange 2.2 2.73 18.00 53.21 58.30 1144.55 1991 Erie Leon 2.8 7.80 1.58 7.08 377.50 1991 Fanny Putnam 4.4 8.12 5.00 3.89 6.53 134.72 1991 Georges Putnam 3.4 6.24 6.50 2.26 10.29 101.39 1991 Gillis Putnam 3.3 5.48 9. 50 5.56 8.36 456.11 1991 Grandin Putnam 1.3 2.51 35.00 23.67 40.10 687.67 1991 Little Orange Alachua 2 3.55 90.50 23.33 33.73 980.30 1992 Alice Hillsborough 5.5 16.33 3. 50 1.20 3.77 122.33 1992 Banana Putnam 1.8 3.67 9.09 14.39 709.39 1992 Bass Pasco 2.7 5.04 28.67 17.07 33.56 779.63 1992 Bear Seminole 3 11.97 13.71 3.33 12.51 368.65 1992 Beauclaire Lake 1.7 1.04 58.31 181.87 139.23 3679.33 1992 Bethel Volusia 1.6 3.25 166.80 19.92 139.47 1385.83 1992 Blue Volusia 2.9 3.61 128.00 20.40 35.00 1067.67 1992 Brant Hillsborough 4.5 6.51 65. 52 6.25 20.69 774.44 1992 Broward Putnam 4.3 11.00 6.30 2.46 6.36 180.40 1992 Cherry Lake 3.3 12.76 122.50 3.11 10.37 533.33 1992 Church Hillsborough 4.3 6.88 11.00 5.55 16.45 700.61 1992 Como Putnam 3.4 10.18 3.88 2.00 5.07 158.52 1992 Crenshaw Hillsborough 2.3 5.48 62.83 10.36 21.67 733.61 1992 David St Lucie 1.6 4.50 11.31 3.96 10.87 479.67 1992 De Witt St Lucie 1.9 4.95 21.21 15.96 24.89 764.44 1992 Deborah St Lucie 1.8 5.13 19.20 3.08 17.61 519.72 1992 Dora West Lake 0.9 1.09 43.75 166.40 56.20 3389.00 1992 Dorr Lake 1.3 4.16 70.63 11.82 14.76 411.21 1992 Eaton Marion 1.6 2.61 380.19 3.97 25.92 1009.44 1992 Emma Lake 5.5 13.36 128.09 2.58 8.30 563.64 1992 Emporia Volusia 2.9 8.52 3.20 11.42 754.24

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31 Table B-1. Continued. Year Lake County MDC SD Color Chlorophyll TP TN 1992 Floyd Pasco 2.8 6.83 26.00 3.42 14.47 826.11 1992 Formosa Orange 2.3 3.61 14.54 42.00 38.17 796.11 1992 Georgia Orange 5.3 9.67 18.35 3.56 8.22 535.56 1992 Gertrude Lake 8 16.35 6.28 2.47 7.10 558.61 1992 Halfmoon Marion 3.1 4.31 47.94 9.92 16.47 620.83 1992 Hall Leon 6 13.84 6.31 16.07 23.77 412.58 1992 Hampton Bradford 4.1 6.35 12.06 5.06 11.25 489.72 1992 Hart Orange 1.8 1.97 183.33 3.39 15.08 1143.06 1992 Henderson Citrus 2.7 5.92 151.05 7.61 19.17 898.33 1992 Hernando Citrus 3 7.75 101.78 3.60 10.63 564.00 1992 Hiawatha Hillsborough 5. 2 6.79 36.69 10. 17 15.61 508.89 1992 Hickorynut Orange 5.8 15.46 53.50 1.08 5.88 730.00 1992 Howell Seminole 4 3.16 47.58 46.75 1068.33 1992 Island Marion 0.8 6.04 3.00 2.83 12.99 298.33 1992 Jean St Lucie 2.2 6.33 2.86 10.97 491.94 1992 Jeffery St Lucie 2.2 5.14 10.75 2.00 9.33 520.00 1992 Joanna Lake 3.1 11.95 12.20 2.05 6.33 422.08 1992 Karen St Lucie 2.3 3.84 14.25 22.04 32.89 1086.30 1992 Keene Hillsborough 2.1 5. 10 119.00 12.33 36.23 1149.67 1992 Keystone Hillsborough 3. 7 9.23 98.71 2. 70 9.18 462.73 1992 Kingsley Clay 8.3 21.81 6.43 3.56 4.59 260.74 1992 Kirkland Lake 4.1 10.71 2.37 7.27 357.17 1992 Little Henderson Citrus 2.5 5.91 66.19 9.06 15.67 877.78 1992 Little Weir Marion 3. 4 5.85 10.50 9. 38 12.38 915.83 1992 Ola Orange 6.1 12.03 9.50 3.06 12.08 560.00 1992 Osceola Hillsborough 5.2 15.22 36.50 1. 94 6.25 443.06 1992 Sellers Lake 7.5 20.00 2.50 1.03 3.39 42.50 1992 Seminary Seminole 6.5 15.63 8.42 2.50 8.19 354.44 1993 Bay Orange 3 2.91 21.00 47.77 39.23 1455.13 1993 Bear Seminole 2.2 10.89 9.00 3.15 12.39 391.47 1993 Blue Heron Leon 2.3 2.70 15.00 51.48 55.15 938.48 1993 Conway South Orange 6.8 11.38 7.00 7.67 10.00 440.51 1993 Coon Osceola 1 1.78 217.00 8.37 35.23 1045.00 1993 Cowpen Putnam 3.9 10.23 1.00 1.67 5.00 86.67 1993 Crescent Hillsborough 3.3 7.00 22.00 10. 75 14.75 549.17 1993 Croft Citrus 3.4 12.00 19.00 2.31 6.72 601.28 1993 Crooked Lake 2.8 5.10 15.00 10.36 21.77 971.03 1993 Dead Lady Hillsborough 2. 6 5.65 75.00 31. 23 36.69 1104.62 1993 Diane Leon 4.2 8.31 6.00 2.56 13.19 304.72 1993 Disston Flagler 0.7 1.69 290.00 7.00 25.36 965.76 1993 Eagle Polk 2.8 3.00 10.00 27.50 19.33 1110.00 1993 Egypt Hillsborough 2.5 4.77 12.00 19. 25 20.58 745.00 1993 Elbert Polk 4.9 5.50 9.00 3.33 12.33 553.33 1993 English Putnam 2.8 4.76 35.00 13.33 13.00 870.00 1993 Erie Leon 1.7 5.81 2.89 5.17 419.44 1993 Fannie Polk 1.7 2.14 63.00 27.86 56.00 1133.33 1993 Fredrica Orange 5 10.38 7.00 4.73 12.87 417.33

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32 Table B-1. Continued. Year Lake County MDC SD Color Chlorophyll TP TN 1993 Gillis Putnam 3.4 7.44 6.00 7. 06 9.03 318.06 1993 Grasshopper Lake 4.6 12.38 0.00 1.41 2.05 235.13 1993 Haines Polk 1.8 1.99 55.00 99.10 158.21 1804.62 1993 Halfmoon Hillsborough 3.5 6.89 9.00 6. 13 13.88 533.75 1993 Hamilton Polk 1 3. 63 62.00 8.61 116.33 1042.22 1993 Hampton Bradford 2.7 6.49 28.00 4.74 9.79 511.54 1993 Harney Volusia 1.7 3.40 108.00 8.75 38.56 1157.92 1993 Harris Lake 1.8 2.72 12.00 67.53 31.20 1839.67 1993 Hartridge Polk 4.7 4.62 9.00 1.00 9.00 396.67 1993 Henry Polk 0.9 1.51 295.00 4.60 131.00 1207.33 1993 Higgenbotham Putnam 5.1 11.57 7.00 2.46 5.77 389.49 1993 Highland Orange 2.4 4.17 9.00 22.00 36.13 625.33 1993 Howard Polk 1.6 2.22 20.00 39.23 31.40 1446.67 1993 Idlewild Lake 4 5.30 55.00 10.09 15.64 1005.76 1993 Ivanhoe East Orange 2.6 3.31 14.00 29.48 30.82 770.61 1993 Ivanhoe Middle Orange 3.5 3.91 15.00 24.03 29.58 612.78 1993 Ivanhoe West Orange 2.9 3.05 15.00 29.78 31.85 720.37 1993 Lawsona Orange 1.6 3.46 27.28 82.81 996.11 1993 Little Bass Polk 1.5 2.24 40.00 92.85 344.22 1912.95 1993 Little Halfmoon Hillsborough 3.2 11.19 9.00 2.67 7.58 451.39 1993 Little Santa Fe Alachua 3.4 5.67 54.00 7.33 12.63 528.97 1993 Little Spirit Polk 5. 7 8.00 27.00 5. 58 20.33 704.17 1993 Lizzie Osceola 1.8 4.56 97.00 3.74 15.72 738.72 1993 Marsha Orange 7.8 16.21 13.00 2.64 7.14 391.39 1993 Mary Marion 3.5 14.50 1.00 1.61 2.58 118.61 1993 Rosa Putnam 3 14.69 4.00 6.95 5.59 86.92 1994 Ashby Volusia 2.1 2.56 192.75 3.92 67.14 737.50 1994 Bennett Orange 2.9 7.56 12.88 7.46 18.30 613.70 1994 Conway North Orange 6.9 8.60 6.96 11.88 11.15 534.55 1994 Conway South Orange 6.6 10.49 7.17 9.36 10.09 458.79 1994 Eaton Marion 1.6 2.40 380.19 6.45 22.67 1276.67 1994 Highland Orange 2.4 4.38 13.50 16.42 32.00 620.00 1994 Howell Seminole 3.1 2.67 15.00 32.42 35.83 653.33 1996 Bellamy Citrus 4.3 9.19 31.00 3.04 11.11 687.04 1996 Blue Highlands 4.5 10.89 7.00 4.22 10.22 575.56 1996 Broward Putnam 6.7 15.83 4.00 1.96 6.29 296.46 1996 Clay Highlands 5.2 10.61 8.00 5.45 11.12 459.70 1996 Crews Highlands 1.4 4.37 28.00 5.83 13.77 423.67 1996 Denton Highlands 3.9 23.02 3.00 1.64 3.39 3133.64 1996 Dinner Highlands 6.4 20.27 4.00 1.67 7.67 633.33 1996 Dodd Citrus 3.7 8.70 29.00 4.04 10.78 774.07 1996 Eagle Pond Highlands 1.7 4.19 18.00 13.39 12.50 698.79 1996 Floral City Citrus 1.7 3.64 157.00 12.83 33.44 974.17 1996 Francis Highlands 4.1 6.50 5.00 12.40 14.42 510.33 1996 Hall Leon 9 16.68 6.00 3.52 11.80 320.60 1996 Hampton Citrus 1.8 3.58 111.00 16.43 30.26 929.64 1996 Henderson Citrus 2.7 4.52 107.00 9.79 21.67 960.91

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33 Table B-1. Continued. Year Lake County MDC SD Color Chlorophyll TP TN 1996 Hickorynut Orange 4.6 10.97 19.00 2.85 7.64 694.24 1996 Hill Highlands 3.2 6.15 13.00 5. 81 10.00 347.41 1996 Jackson Highlands 5 11.22 10.00 4.50 12.28 337.78 1996 Josephine Center Highlands 1.2 1.81 92.00 24.97 46.10 959.67 1996 Josephine East Highlands 1 2.46 58.00 24.33 35.30 915.56 1996 Josephine West Highlands 0.8 1.56 127.00 33.40 82.50 1079.33 1996 Lillian Highlands 4.5 8.23 6.00 7. 73 9.58 631.21 1996 Little Henderson Citrus 4 5.00 77.00 8. 83 18.61 932.73 1996 Little Jackson Highlands 2.7 2.94 27.50 52. 78 51.67 1167.41 1996 Little Santa Fe Alachua 3.7 5.41 106.70 6.03 10.85 450.30 1996 Ola Orange 6.6 14.96 8.00 3.42 9.82 525.00 1997 Carroll Hillsborough 4.6 11.00 8.69 2. 33 12.67 463.33 1997 Fanny Putnam 5.1 11.83 3.63 2.28 4.78 129.44 1997 Lily Clay 4 11.50 2.76 2.74 6.33 109.26 1997 Lochloosa Alachua 2.5 2.24 222.00 70.66 52.14 1795.45 1997 Sheelar Clay 6 26.77 1.39 1.62 3.25 87.08 1997 Winnemissett Volusia 6.2 18.75 6.50 0.50 5.75 193.33 1998 Ada Seminole 3.2 8.19 14.00 5.89 16.50 534.67 1998 Alto Alachua 2.5 4.63 83.30 9.36 17.97 586.11 1998 Bay Orange 2.1 3.04 25.63 39.15 37.50 1086.67 1998 Chipco Putnam 5.5 11.86 8.13 5.43 10.50 319.33 1998 Cowpen Putnam 4.5 9.50 1.00 2.78 6.56 193.33 1998 Crooked Lake 1.9 5.71 37.31 7.58 13.94 718.89 1998 Crystal Clay 3.9 7.40 9.00 5.67 11.30 264.67 1998 Dorr Lake 0.7 2.08 70.63 15.60 18.00 499.33 1998 Gillis Putnam 2.2 3.47 10.77 11.47 912.33 1998 Grandin Putnam 1.6 3.95 19.67 28.76 501.21 1998 Grasshopper Lake 3.7 6.39 112.42 3.25 5.72 365.28 1998 Joes Marion 4.2 7.83 11.00 3.88 10.39 598.18 1998 Kingsley Clay 7.5 16.88 6.43 6.96 8.13 323.75 1998 Little Bear Seminole 2. 9 12.49 16.52 3. 17 13.00 474.17 1998 Little Crystal Clay 2. 7 5.87 25.50 7. 78 12.50 330.00 1998 Little Orange Alachua 2.2 2.76 173.65 10.58 129.81 958.33 1998 Little Santa Fe Alachua 3.1 4.41 106.70 11.42 14.56 530.00 1998 Little Weir Marion 3. 5 6.18 10.50 8. 58 11.09 816.67 1998 Lizzie Osceola 1 2.67 98.33 5.30 22.52 744.81 1998 Sellers Lake 7.6 21.00 2.50 1.33 3.50 76.06 1998 Seminary Seminole 5.4 15.49 8.42 2.52 7.94 373.03 1999 Bear Seminole 5.9 13.01 13.71 4.17 14.35 440.42 1999 Beauclaire Lake 1.5 0.78 58.31 291.56 169.44 4551.94 1999 Bennett Orange 3.8 11.15 12.88 2.56 16.74 524.44 1999 Carlton Orange 1 1.06 41.87 219.25 85.97 3572.22 1999 Disston Flagler 0.9 1.29 428.47 4.00 25.67 1074.72 1999 Erie Leon 2.2 4.77 2.25 6.82 457.58 1999 Gatlin Orange 2.7 2. 25 15.64 36.81 21.39 1209.17 1999 Halfmoon Marion 2.2 4.85 47.94 8.00 14.78 774.17

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34 Table B-1. Continued. Year Lake County MDC SD Color Chlorophyll TP TN 1999 Hiawatha Leon 2.6 4.41 174.17 5.39 19.56 520.56 1999 Josephine Center Highlands 1.6 1.82 134.05 20.17 57.47 930.56 1999 Josephine East Highlands 1.8 2.58 87.40 37.70 47.47 1003.67 1999 Josephine West Highlands 1.4 1.53 158.30 19.78 93.72 977.78 1999 June Highlands 3.4 4.97 13.70 17.25 13.78 745.00 1999 Juniper East Walton 3.7 6.93 14.81 6.64 12.94 367.22 1999 Juniper West Walton 3.5 6.67 14.79 5.33 11.56 717.78 1999 Little Conway Orange 8.5 12.51 6.00 3.69 11.50 479.72 1999 Lochloosa Alachua 2.6 1.54 222.00 152.50 62.93 2351.25 1999 Wooten Jefferson 4.2 10.78 4.10 13.52 301.90 2000 Asbury North Clay 6.5 8.50 14.50 7.81 20.56 409.63 2000 Bedford Bradford 2.4 5.64 13.00 11.56 44.33 783.06 2000 Deerback Marion 1.8 8.27 19.56 3.50 10.75 559.58 2000 Dexter Polk 5.3 15.43 9.60 2.25 9.21 425.83 2000 Diane Leon 3.7 4.40 9.07 8.78 22.36 529.72 2000 Eagle Polk 3.6 3.50 9.75 18.54 21.42 807.50 2000 East Pasco 3.6 8.75 16.98 3.39 18.00 582.22 2000 Florida Seminole 2.5 5.14 12.82 33.36 909.44 2000 Hartridge Polk 1.7 4.35 11.00 14.50 20.67 625.00 2000 Henry Polk 1.2 1.31 98.50 8.05 96.24 1122.86 2000 Little Bass Polk 2 1. 33 23.25 148.25 401.64 2643.61 2000 Little Santa Fe Alachua 3.2 5.34 106.70 9.94 15.83 528.61 2001 Arbuckle Polk 1 1.46 269.00 17.44 82.22 1258.33 2001 Big Volusia 2.2 6.00 56.40 5.93 18.57 707.62 2001 Cassidy Holmes 6 18.15 1.33 1.83 4.71 129.58 2001 Conway North Orange 4.6 13.29 6.33 4.00 11.83 366.67 2001 Conway South Orange 7 14.90 7.50 2.58 10.17 359.17 2001 Crooked Polk 5.4 8.16 15.50 3.97 13.53 580.94 2001 De Witt St Lucie 2 3.04 20.50 13. 82 29.94 988.89 2001 Deborah St Lucie 1.7 5.80 19.20 2.25 12.13 508.33 2001 Grayton Walton 1.5 4.42 32.25 3.44 11.92 251.11 2001 Howell Seminole 3.3 2.75 15.00 38.45 41.95 1032.80 2001 Istokpoga Highlands 1.7 2.97 55.25 36.75 55.61 1515.56 2001 Ivanhoe East Orange 1.8 3.63 12.00 30.71 25.74 827.86 2001 Ivanhoe Middle Orange 1.7 4.17 10.50 25.29 27.19 725.24 2001 Ivanhoe West Orange 2.7 4.12 13.00 30.43 35.62 692.86 2001 Josephine Center Highlands 0.8 1.75 105.00 25.08 76.22 1007.78 2001 Josephine East Highlands 1 2.68 70.50 29.36 51.58 944.55 2001 Josephine West Highlands 1.2 1.57 121.00 25.33 111.31 1068.06 2001 Jovita Pasco 4.2 5.79 8.75 10.22 21.47 783.06 2001 June Highlands 4.7 9.03 7.75 6.83 11.11 499.72 2001 Juniper East Walton 3.7 7.64 13.67 6.00 11.18 417.64 2001 Juniper West Walton 2.4 6.93 14.67 7.78 11.42 864.72 2001 Karen St Lucie 1.9 4.82 14.25 5.10 15.53 665.67 2001 Little Wilson Hillsborough 4 5.89 31.00 8. 63 25.44 875.93 2001 Lochloosa Alachua 1.5 1.30 222.00 138.00 89.88 3823.75

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35 Table B-1. Continued. Year Lake County MDC SD Color Chlorophyll TP TN 2001 Margaret St Lucie 2.2 5.02 8.75 6.52 12.19 434.44 2001 Viola Highlands 5.5 14.90 3.00 2.58 7.92 446.67 2002 Bessie Orange 8.6 15.79 8.00 2.06 7.08 479.72 2002 E Miami-Dade 7.8 17.67 3.75 1.41 5.22 321.48 2002 Grassy Highlands 4.7 12.06 11.80 2.69 9.50 716.11 2002 Sellers Lake 8.9 19.83 1.83 1.09 3.33 66.67 2002 Verona Highlands 6.1 14.09 5.10 6.41 10.37 340.37 2003 Alligator Osceola 2. 6 3.37 54.58 5. 11 19.63 875.14 2003 Annie Putnam 3 9.67 9.00 3.78 10.08 428.33 2003 Blue Lake 2 3.27 72.50 5.78 15.67 385.56 2003 Clear Lake 4.8 11.65 14.80 2.64 13.31 502.50 2003 Cliff Broward 4.4 7.33 26.00 5.28 20.89 455.00 2003 Conway North Orange 8 14.30 8.00 3.47 8.73 412.00 2003 Conway South Orange 7.1 14.17 8.00 4.67 10.20 434.00 2003 Delevoe Broward 2.3 6.29 8.00 29.21 44.57 828.57 2003 Farm 13 Indian River 2.1 3.09 85.00 35.94 76.75 1634.44 2003 Florence Seminole 4.2 9.33 11.00 5.00 12.83 518.33 2003 Flynn Hillsborough 1.9 3. 67 63.08 5.97 10.14 1145.28 2003 Formosa Orange 3.4 6.77 14.00 30.21 45.03 856.67 2003 Galilee Putnam 2.5 3.77 8.00 10. 00 15.00 230.00 2003 Highland Miami-Dade 5.2 7.27 17.00 7.00 15.00 462.33 2003 Highland Orange 2.8 3.52 12.00 39.67 50.17 773.33 2003 Istokpoga Highlands 2 2.46 62.00 51.75 64.97 1382.50 2003 Ivanhoe East Orange 2.3 5.91 11.40 14.00 34.72 707.33 2003 Ivanhoe Middle Orange 2.4 6.04 11.73 15.71 26.85 681.30 2003 Ivanhoe West Orange 3.4 6.59 11.65 22.33 29.95 633.67 2003 Jem Lake 3.5 8.98 9.83 5.75 12.06 481.94 2003 John's Orange 1.3 2.54 125.00 16.42 55.97 1298.50 2003 Josephine Center Highlands 1.2 1.55 173.00 22.11 74.36 916.11 2003 Josephine East Highlands 1.2 2.02 113.00 40.61 59.03 1036.39 2003 Josephine West Highlands 1.1 1.55 212.00 17.33 114.33 928.89 2003 Lochloosa Alachua 1.1 2.47 222.00 26.57 36.50 1544.50 2003 Winyah Orange 2 6.83 23.00 30.52 56.57 1019.33 2004 Alto Alachua 2.5 3.37 102.75 13.88 19.58 763.94 2004 Bay Marion 2 3.83 19.00 16.04 24.62 813.11 2004 Bellamy Citrus 0.7 4.76 74.00 9.27 22.90 1207.62 2004 Brant Hillsborough 1 3. 05 107.00 43.50 52.10 1203.67 2004 Church Hillsborough 2 8.10 11.00 4. 81 15.58 656.27 2004 Conway North Orange 5.5 17.00 7.00 2.00 10.33 404.44 2004 Conway South Orange 5.8 12.39 6.50 4.11 10.89 388.89 2004 Dodd Citrus 1.0 5.21 79.75 8.72 19.94 1289.17 2004 Doe Marion 4.2 4.50 4.33 11.33 283.33 2004 Grasshopper Lake 2.2 2.71 208.67 4.36 8.70 958.18 2004 Hampton Bradford 1.7 4.71 10.00 5.25 11.58 490.83 2004 Hernando Citrus 2.3 4.61 71.40 9.08 20.25 1112.08 2004 Ivanhoe East Orange 2.2 4.88 9.50 21.04 17.10 537.62

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36 Table B-1. Continued. Year Lake County MDC SD Color Chlorophyll TP TN 2004 Little Conway Orange 5.6 12.97 8.00 4.11 11.33 496.67 2004 Little Santa Fe Alachua 2 2.91 180.75 6.97 18.77 925.67 2004 Magdalene Hillsborough 3. 6 7.68 32.80 6. 75 19.42 811.39 2004 Maurine Hillsborough 1. 2 6.07 7.26 20.66 801.14 2004 Melrose Bay Alachua 2.9 5.52 41.00 8.80 13.90 562.67 2004 Mill Dam Marion 2.7 9.27 14.00 3. 83 10.27 471.33 2004 Newnan Alachua 0.6 0.97 206.83 223.84 121.64 3479.12 2004 Osceola Hillsborough 3.5 6.89 40.00 7. 08 20.25 847.50 2004 Santa Fe Alachua 3.9 5.34 45.50 8.00 12.13 564.33 2004 Sellers Lake 9.2 18.68 5.00 2.52 4.70 250.30 2004 Starke Orange 1.5 3.48 18.67 25.50 24.67 881.67 2004 Stella Putnam 4.3 8.33 5.50 7.67 598.33 2004 Taylor Hillsborough 3.1 5.95 35.50 8. 00 22.04 717.92 2004 Twin Hillsborough 2.6 3.89 12.50 22. 96 24.70 802.28 2004 Weir Marion 3 6.17 6.92 11.00 13.50 863.33 2004 White Trout Hillsborough 4. 8 9.28 12.60 4. 67 13.67 437.14

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37 LIST OF REFERENCES APHA. 1992. Standard Methods for the Exam ination of Water and Wastewater. 18th Edition. Am. Public Health Assn. Washington, D. C. Bachmann, R. W., M. V. Hoyer, D. E. Canfield, Jr. 2001. Evaluation of recent limnological changes at Lake A popka. Hydrobiologia. 448: 19-26. Barko, J. W., D. Gunnison, and S. R. Carp enter. 1991. Sediment interaction with submersed macrophyte growth and community dynamics. Aquat. Bot. 41: 41-65. Bowling, L. C., M. S. Steane, and P. A. Bays. 1986. The spectral distribution and attenuation of underwater ir radiance in Tasmanian inland water. Freshwater Biol. 16: 331-335. Canfield, D. E., Jr. 1983. Predication of chlor ophyll a concentrations in Florida Lakes: the importance of phosphorus and nitroge n. Water Resour. Bull. 19(2): 255-262. Canfield, D. E., Jr., and L. M. Hodgson. 1983. Predication of Secchi disc depths in Florida lakes: impact of algal biomass and organic color. Hydrobiologia. 99: 5160. Canfield, D. E., Jr., K. A. Langeland, S. B. Linda, and W. T. Haller. 1985. Relations between water transparency and maximu m depth of macrophyte colonization in lakes. J. Aquat. Plant Manage. 23: 25-28. Canfield, D. E., Jr., and M. V. Hoyer. 1988. Regional geology and the chemical and trophic state characteristics of Florida la kes. Lake and Reserv. Manage. 4(1): 2131. Chambers, P. A., and J. Kalff. 1985. Dept h distribution and biomass of submersed aquatic macrophyte communities in relation to Secchi depth. Can. J. fish. Aquat. Sci. 42: 701-709. Cole, G. A. 1983. Textbook of limnology. Third Edition. C. V. Mosby Company. St. Louis, MO. D'Elia, C. F., P. A. Steudler, and N. Corw in. 1977. Determination of total nitrogen in aqueous samples using persulfate di gestion. Limnol. Oceanogr. 22: 760-764.

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38 Duarte, C. M., and J. Kalff. 1986. Littoral sl ope as a predictor of the maximum biomass of submerged macrophyte communities Limnol. Oceanogr. 31(5): 1072-1080. Duarte, C. M., and J. Kalff. 1990. Patterns in the submerged macrophyte biomass of lakes and the importance of the scale of analysis in the interpretation. Can. J. Aquat. Sci. 47: 357-363. Florida LAKEWATCH. 2003. Florida LAKE WATCH annual data summaries 2002. Department of Fisheries and Aquatic Scien ces, University of Florida / Institute of Food and Agricultural Sciences, Gainesville, FL. Havens, K. E. 2003. Submerged aquatic vege tation correlations with depth and light attenuating materials in a shallow subt ropical lake. Hydrobi ologia. 493: 173-186. Holmes, R. W. 1970. The Secchi disk in turb id coastal waters. Limnol. and Oceanogr. 15: 688-694. Hoyer, M. V, T. K Frazer, S. K. Notest ein, and D. E Canfield, Jr. 2004. Vegetative characteristics of three low-lying Florida coastal rivers in relation to flow, light, salinity and nutrients. H ydrobiologia. 528: 31-43. Hudon, C., S. Lalonde., and P. Gagnon. 2000. Ranking the effects of site exposure, plant growth form, water depth, and transparency on aquatic plant biomass. Can J. Fish. Aquat. Sci. 57(Suppl. 1): 31-42. Hutchinson, G. E. 1975. A treatise of lim nology. Vol. 3. Limnological botany. John Wiley and Son, Inc. New York, NY Jupp, B. P., and D. H. N. Spence. 1977. Lim itations on macrophytes in a eutrophic lake, Loch Leven. J. Ecol. 65: 175-186. Langeland, K. A. 1996. Hydrilla verticillata (L.F.) Royle (Hydroch aritaceae), the perfect aquatic weed. Cast anea. 61(3): 293-304. Lind, O. T. 1974. Handbook of common methods in limnology. The C. V. Mosby Company. St Louis, MO. Maristo, L. 1941. Die Seetypen Finnlands auf floristischer und vegetationsphysiognomischer Grundlage. Suom. El ain-ja Kasvitiet. Seuran Vanamon Kasvitiet. Julk. Ann Bot. Soc. Zool. Bot. Vanamo. No. 5: 314. McClave, J. T., and T. Sincich. 2000. Statistics 8th Edition. Prentice Hall. Upper Saddle River, NJ.

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39 Menzel, D. W., and N. Corwin. 1965. The meas urement of total phosphorus in seawater based on the liberation of organically bound fractions by persulfate oxidation. Limnol. and Oceanogr. 10: 280-282. Murphy. J., and J. P. Riley. 1962. A modi fied single solution method for the determination of phosphate in natural waters. Anal. Chim. Acta 27: 31-36. Poole, H. H., and W. R. G. Atkins. 1929. Photo-electric measurement of submarine illumination throughout the year. J. Ma r. Biol. Assoc. U.K. 16: 297-324. Rickett, H. W. 1924. A quantitative study of th e larger aquatic plants of Green Lake, Wisconsin. Trans. Wisc. Acad. Arts Sci. Lett. 21: 381-414. Sartory, D. P., and J. U. Grobbelarr. 1984. Extraction of ch lorophyll a from freshwater phytoplankton for spectrophotometric an alysis. Hydrobiol ogia. 114: 117-187. Scheffer, M. 1998. Ecology of shallow lakes. Chapman & Hall. London, England. Sheldon, R. B., and Boylen, C. W. 1977. Maxi mum depth inhabited by aquatic vascular plants. Am. Midl. Nat. 97(1): 248-254. Van, T. K, W. T. Haller, and G. Bo wes. 1976. Comparison of the photosynthetic characteristics of three submersed aqua tic plants. Plant Physiol. 58: 761-768. Walker, T. A. 1980. A correction to the Pool e and Atkins Secchi Disc/Light-Attenuation Formula. J. Mar. Biol. Ass. U.K. 60: 769-771. Weisner, S. E. B., J. A. Strand, and H. Sandsten. 1997. Mechanisms regulating abundance of submerged vegetation in sh allow eutrophic lakes. Oceologia. 109: 592-599. Zimmerman, R. C., A. Cabello-Pasini, a nd R. S. Alberte. 1994. Modeling daily production of aquatic macrophytes from irra diance measurements: a comparative analysis. Mar. Ecol. Prog. Ser. 114: 185-196.

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40 BIOGRAPHICAL SKETCH Alexis J. Caffrey earned an Associate of Arts degree at Santa Fe Community College in Gainesville, FL. She went on to earn a Bachelor of Science degree at the University of Florida with a major in Wildlife Ecology and Conservation.