Citation
Role of Beaver Impoundments in the Structure and Function of Southern Georgia Streams

Material Information

Title:
Role of Beaver Impoundments in the Structure and Function of Southern Georgia Streams
Creator:
Mcneely, Cody R
Place of Publication:
[Gainesville, Fla.]
Florida
Publisher:
University of Florida
Publication Date:
Language:
english
Physical Description:
1 online resource (53 p.)

Thesis/Dissertation Information

Degree:
Master's ( M.S.)
Degree Grantor:
University of Florida
Degree Disciplines:
Interdisciplinary Ecology
Committee Chair:
Crisman, Thomas L.
Committee Members:
Wise, William R.
Mossa, Joann
Graduation Date:
12/14/2007

Subjects

Subjects / Keywords:
Conductivity ( jstor )
Creeks ( jstor )
Impoundment ( jstor )
Macroinvertebrates ( jstor )
Oxygen ( jstor )
Ponds ( jstor )
Statistical significance ( jstor )
Streams ( jstor )
Turbidity ( jstor )
Water temperature ( jstor )
Interdisciplinary Ecology -- Dissertations, Academic -- UF
anthropogenic, beaver, carbon, climate, function, impoundments, macroinvertebrates, om, stream, structure
Genre:
bibliography ( marcgt )
theses ( marcgt )
government publication (state, provincial, terriorial, dependent) ( marcgt )
born-digital ( sobekcm )
Electronic Thesis or Dissertation
Interdisciplinary Ecology thesis, M.S.

Notes

Abstract:
The North American beaver (Castor canadensis) is one of the few extant mammals able to modify its surrounding landscape dramatically, often complicating its relationship with humans. However, the vast majority of research has been limited to north temperate regions, with almost no data regarding southern beaver populations. The focal point of this study was to understand the impact beaver impoundments on stream systems of warm temperate regions. Two sites in Thomasville, Georgia (Gatling Branch and Unnamed Creek) were selected for this study based on location, morphology, hydrology and active beaver populations. Sampling was conducted from November 2006 through April 2007, with April capturing the effects of extensive anthropogenic construction activities. For each system, two 100-m stretches, upstream and downstream of the beaver pond, and the pond proper were sampled. Measurements and/or samples included chemical / physical parameters (temperature, dissolved oxygen, specific conductivity and total suspended solids), macroinvertebrate communities and benthic organic matter storage. Statistical comparisons were made between compartments (upstream, downstream and pond), sampling periods and compartments relative to sampling period. During the pre-anthropogenic disturbance period, few parameters were longitudinally or temporally significant when compared between sampling compartment and sampling dates. However, effects resulting from beaver activity included changes in organic matter (OM) storage, dissolved oxygen (DO) and invertebrate abundance. Mean upstream OM storage at Unnamed Creek was 6,600 g/m2, while storage within the pond proper increased to 56,000 g/m2, almost an order of magnitude greater. Longitudinal DO at Gatling Branch decreased from 7.6 mg/L upstream to 3.2 mg/L within impounded areas, and was attributed to increased OM loading. Responding to changes in DO, invertebrate abundance at Gatling Branch decreased from 94,000 invertebrates/m2 upstream to 24,000 invertebrates/m2 within the backwater/pond. Longitudinal and temporal effects attributed to human construction activities adjacent to and immediately downstream of the beaver pond at Gatling Branch included intense changes in water temperature, dissolved oxygen, suspended solids (turbidity) and invertebrate abundance. During April, mean water temperature increased from 16 degrees Celsius in undisturbed sections of the stream to over 22 degrees Celsius within backwater/pond and downstream segments. During the same sampling period, mean DO decreased from 6.8 mg/L upstream to 3.9 mg/L within the pond, while mean turbidity increased from 4.6 NTU upstream to 14.7 NTU within and downstream of the beaver pond. In response to these chemical/physical changes, invertebrate abundance during April decreased from 162,000 individuals/m2 upstream to 28,000 individuals/m2 within the backwater / pond area. During this study, the effects of beaver impoundments were limited to invertebrate abundance, dissolved oxygen and OM storage. Conversely, anthropogenic disturbances appear to have much greater effect on stream systems, with dramatic changes in temperature, dissolved oxygen, turbidity and invertebrate communities. Finally, the OM and carbon sequestration potential of these beaver impoundments was tremendous and may offer an overlooked component to counter global climate change. ( en )
General Note:
In the series University of Florida Digital Collections.
General Note:
Includes vita.
Bibliography:
Includes bibliographical references.
Source of Description:
Description based on online resource; title from PDF title page.
Source of Description:
This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Thesis:
Thesis (M.S.)--University of Florida, 2007.
Local:
Adviser: Crisman, Thomas L.
Statement of Responsibility:
by Cody R Mcneely.

Record Information

Source Institution:
UFRGP
Rights Management:
Copyright Mcneely, Cody R. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Classification:
LD1780 2007 ( lcc )

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MERRITT, R. W., AND K. W. CUTMMINGS. 1996. An introduction to the aquatic insects of North
America, (3rd ed.). Kendall Hunt Publishing Co.

MORGAN, L. H. 1986. The American Beaver. Dover Publications.

RAY, A. M., A. J. REBERTUS, AND H. L. RAY. 2001. Macrophyte succession in Minnesota beaver
ponds. Canadian Journal of Botany 79: 487-499.

WETZEL, R. G. 1983. Limnology, (2nd ed.). Saunders College Publishing.

































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Figure 3-9. Longitudinal temperature profile for Unnamed Creek.


Figure 3-10. Longitudinal dissolved oxygen profile for Unnamed Creek.









85,500 and 35,000 invertebrates/m2, TOSpectively). No significance was observed between pond

and downstream segments for any sampling period.

Taxonomic richness was greatest during April, with an average of 4.2 families throughout

the system. Richness during November and January displayed close similarities, averaging 3.8

and 3.5 families, respectively (Figure. 3-14). Mean richness was greatest upstream and lowest

downstream, 4.5 and 3.5 families, respectively. Richness was intermediate within backwater /

pond at 3.8 invertebrate families. No statistical significances between longitudinal taxa richness

and sampling compartment were observed. However, statistical significance was observed

between richness and sampling period, when comparing upstream segments between January and

April (p<0.002), with upstream richness significantly greater during April compared to January

(5.8 and 3 taxa, respectively). There were no significant differences in taxa richness for any other

sampling compartment or period.

Three main feeding guilds were present at Gatling Branch: collector/gatherers, fi1terer

feeders and predators. Although longitudinal variation was observed, collector/gatherers

dominated all sampling compartments and dates, accounting for 85 to 97 percent of total

individuals. Mean abundances of both collector/gatherers and filter feeders were greatest during

April, with 63,500 and 4,300 individuals/m2, TOSpectively. January had the lowest abundance of

collector/gatherers and filterers with 23,000 and 600 individuals/m2, TOSpectively. November was

intermediate at 51,000 and 1,500 individuals/m2, TOSpectively. Predators followed a different

trend with November and January having the greatest abundance, averaging 1,500 and 1,000

individuals/m2, TOSpectively. April had the lowest abundance at 600 individuals/m2

Mean upstream abundance of collector/gatherers was greatest (88,000 individuals/m2,

while downstream and backwater / pond segments were similar with 27,000 and 22,000






























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Figure 3-15. Longitudinal distribution of collector/gatherers at Gatling Branch.


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Figure 3-16. Longitudinal distribution of filter feeders at Gatling Branch.





















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Figure 3-1. Longitudinal distribution of benthic organic matter at Gatling Branch.


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Figure 3-2. Vertical distribution of benthic organic matter at Gatling Branch.









BIOGRAPHICAL SKETCH

Cody Rick McNeely was born in 1980 in Hinsdale, Illinois. The younger of two, he grew

up in Lemont, Illinois, graduating from Lemont High School in 1998. Cody earned his B.S. in

environmental sciences from Benedictine University (BU) in 2003. Upon graduating, he began

working for Carnow Conibear and Associates (CCA) in Chicago, Illinois. While employed with

CCA, his job responsibilities included discovery and oversight in the removal of hazardous

materials. In August 2005, after two years of employment with CCA, Cody decided to pursue his

M. S. in interdisciplinary ecology at the University of Florida (UF). Upon completion of his M. S.

program in December of 2007, he has plans of returning to Chicago and CCA.










Organic Matter and Sedimentation

Benthic organic matter (BOM) samples were collected using a clear PVC coring device 1-

m long and 3.8 cm in diameter. BOM cores were collected at a transect interval of 0, 10, 25, 50,

75 and 100 m upstream and downstream of the beaver pond. Eleven additional cores at Gatling

Branch and five at Unnamed Creek were collected within the pond and backwater areas at 25-m

intervals. Three BOM cores were collected at each location; left bank, center channel / pond and

right bank. Samples consisted of all material down to the sand or clay substrate. Collection began

at the 100-m downstream transect and proceeded upstream to avoid contamination between

segments .

Macroinvertebrate Communities

Macroinvertebrate samples were collected via the same PVC coring device used in BOM

sampling. Macroinvertebrates from Unnamed Creek were collected at a transect interval of 0, 10,

50, and 100 m upstream and downstream of the beaver pond. Three additional samples were

collected within the pond at randomly selected locations. Because of the extensive backwater

area at Gatling Branch, macroinvertebrates were collected at a transect interval of 10, 50, and

100 m upstream of the beaver pond and 0, 10, 50 and 100 m downstream of the impoundment.

Macroinvertebrates were not collected at the 0-m upstream transect. However, two samples were

collected from within the backwater area 10 m upstream from the pond (BWUSP) and 10 m

downstream from the upstream 0-m transect (BWDSE). Three additional samples were collected

within the pond at randomly selected locations. Only one macroinvertebrate sample was

collected at each transect and consisted of all material to a depth of 15 cm. Samples were placed

into one-liter plastic containers and preserved in situ with 70% ethanol containing 0.2 mg/1 of

Rose Bengal stain. Collection began at the 100-m downstream transect and proceeded upstream

to avoid sampling interference between segments.










Longitudinal decreases in DO were attributed to increased organic matter (OM) loading within

impounded areas and increased biological demand for oxygen resulting from decomposition.

Changes in DO during November and January were assumed to result from beaver activity, with

changes during April attributed to construction activities.

Additional impacts resulting from human construction included significant increases in

suspended solids (turbidity) within adj acent stream segments during the April sampling period.

This was attributed to removal of riparian vegetation, combined with poor silt barrier

performance, facilitating increased lateral inputs of particulate material and the observed

turbidity increase between transects BWUSP and DS100. Unlike Hillman et al. (2004), turbidity

did not increase significantly approaching the impoundment outlet or downstream for any other

sampling period at Gatling Branch (pre-disturbance) or Unnamed Creek. With such intense

changes in temperature, dissolved oxygen, turbidity and potentially invertebrate communities,

lotic systems appear to be far more sensitive to anthropogenic disturbances than impoundment

from beavers.

Similar to founding by Collen and Gibson (2001), invertebrate abundance in Gatling

Branch and Unnamed Creek was significantly lower (per unit area) within and downstream of

impounded areas for all sampling periods. The longitudinal decrease in abundance was attributed

to additional stress resulting from reduced DO within beaver impoundments. Although not

examined in the current study, Bertolo and Magnan (2006), and Hagglund and Sj oberg (1999)

suggested that many fish taxa (brown trout, walleye and lake whitefish) experience reduced

abundance within regions of stream affected by beaver. The relationship between an altered food

web (i.e. reduced invertebrate abundance) and subsequent reduction in fish abundance within









Similar to Unnamed Creek, water temperature during November at Gatling Branch

experienced almost no longitudinal variation, likely the result of a well-vegetated riparian zone

and the relatively small surface area of impoundments. However, during January, water

temperature at Gatlin Branch decreased within pond and downstream segments. This very

different pattern was attributed to the beaver population abandoning the impoundment, and the

ability of cooler bottom water to mix and discharge through subsequently degraded sections of

the dam. During April, pond and downstream temperature at Gatling Branch paralleled the

finding of Maxted et al. (2005), with temperature being greatest at the dam and decreasing with

downstream progression. However, increased temperatures were not the result of beaver activity;

rather, the extensive removal of riparian vegetation during construction and resulting increase of

solar radiation. Temporal differences in mean water temperature at Gatling Branch and Unnamed

Creek between November, January and April are presumed to be the result of seasonal variation,

caused by changes in ambient air temperature and length of daylight.

Research conducted in New Zealand suggested that dissolved oxygen (DO) in beaver

ponds and downstream fluctuates temporally, with reduced DO during summer. Decreases in DO

were attributed to increased organic loading and increased decomposition within the beaver pond

(Maxted et al., 2005). During November and April, longitudinal DO decreased dramatically

within the backwater / pond area at Gatling Branch. Similarly, DO levels at Unnamed Creek

greatly decreased within the pond proper during January and April. As suggested by Maxted et

al. (2005), such longitudinal changes in DO at Gatling Branch and Unnamed Creek are likely the

result of increased metabolic processes and rapid consumption of DO within impounded areas.

However, removal of riparian vegetation, combined with poor performance of installed silt

barriers during construction, presumably caused the decrease in DO observed during April at










performance of silt barriers, the result was increased lateral inputs of ions causing the increase in

conductivity observed between transects BWUSP and DS10.

In contrast, January had almost no longitudinal variation in conductivity, presumably

resulting from the continual flow of water through degraded sections of the main dam, which

prevented accumulation of ions in impounded areas. Temporal differences in conductivity at

Gatling Branch and Unnamed Creek between November, January and April are presumed to

reflect seasonal changes in temperature, rate of decomposition and ion production within the

watershed.

Hillman et al. (2004) investigated suspended solids within beaver ponds and found that

concentrations of fine particulate organic and inorganic matter were greatest near the

impoundment outlet and decreased progressively downstream. In contrast, longitudinal turbidity

during November and January sampling periods at Gating Branch and Unnamed Creek was

relatively stable, and presumed the result of an extensive riparian zone that provided bank

stabilization and reduced lateral input of allocthonous material. However, during November,

small increases in turbidity were observed at upstream transect BWDSE and downstream

transect DSO, resulting from interactions between moving waters of the upstream and static water

of the backwater / pond, and the interface between the main beaver dam and downstream. As

found by Hillman et al. (2004), turbidity during April at Gatling Branch increased dramatically

within and downstream of the impoundment. However, increases in turbidity are presumed to

result from construction activities that facilitated increased riparian inputs of particulate material

that caused the observed increase in turbidity between transect BWUSP and DS100, and not

from beaver activity. In contrast, increased turbidity observed downstream during April at

Unnamed Creek was presumed the result of low flow conditions (less than 2 cm in depth) and































O 2007 Cody Rick McNeely










longitudinal proximity of impoundments presumably prevented OM from returning to baseline

conditions, resulting in increasing OM with progression downstream.

Complex vertical profiles were observed for Gatling Branch and Unnamed Creek.

Vertical stratification was presumably the result of precipitation events that introduce large

quantities of allocthonous sand. When the rain event subsides and/or the stream encounters an

impoundment, stream velocity decreases and sand accumulates. Conversely, during periods of

low flow, allocthonous OM will accumulate. Thus, it is suggested that oscillation in stage is the

cause for vertical stratification. The vertical profile for upstream and downstream segments at

Gatling Branch and Unnamed Creek exhibited an indirect relationship between OM and depth,

while a direct relationship existed at stream / impoundment interfaces. This direct relationship

between OM and depth is presumably caused by the predominantly sand substrate that allows for

vertical movement of organic matter and a confining layer of clay that defines the extent of

downward movement. Reduced velocity and increased retention time at stream / impoundment

interface allows biota to process coarse OM, causing a reduction in particle size (Kaplan et al.,

1980, Wetzel 1983). The fine particulate organic matter (FPOM) presumably moves through the

sand substrate, creating a vertical OM profile inverted from upstream and downstream segments.

Sequestered organic matter in aquatic systems represents a significant component of the

global carbon pool. Photosynthetic and respiratory processes within these systems are important

regulators of inorganic carbon (i.e. CO2 and CH4) in the atmosphere (Amundson 2001). The

storage potential of carbon compounds in wetlands, and specifically beaver ponds, can offer

significant contributions to global carbon cycling. Prior to near-extirpation, there was an

estimated 12.5 million beaver ponds in North America trapping hundreds of billions cubic meters

of organic sediment in streams (Butler 2006). The impoundments at Gatling Branch influenced at










LIST OF REFERENCES


A1VIUNDSON, R. 2001. The soil carbon cycle. Annual Reviews of Earth and Planetary Sciences
29: 535-562.

BERTOLO, A., AND P. MAGNAN. 2006. Spatial and environmental correlates of fish community
structure in Canadian shield lakes. Canadian Journal of Fisheries and Aquatic Science 63:
2780-2792.

BUTLER, D. R. 2006. Human induced changes in animal populations and distributions, and the
subsequent effects of fluvial systems. Geomorphology 79: 448-459.

BUTLER, D. R., AND G. P. MALANSON. 1995. Sedimentation rates and patterns in beaver ponds in
a mountain environment. Geomorphology 13: 255-269.

COLLEN, P., AND R. J. GIBSON. 2001. The general ecology of beaver (Castor spp.), as related to
their influence on stream ecosystems and riparian habitats, and the subsequent effects on
fish. Reviews in Fish Biology and Fisheries 10: 439-461.

EVERETT, S., AND J. SCHAEFER. 2006. Florida Beavers. WEC17. University of Florida / IFAS.

FRANCE, R. L. 1997. The importance of beaver lodges in structuring littoral communities in
boreal headwater lakes. Canadian Journal of Zoology 75: 1009-1013.

HAGGLUND, A., AND G. SJOBERG. 1999. Effects of beaver dams on the fish fauna of forest
streams. Forest Ecology and Management 115: 259-266.

HILL1VAN, G. R., J. C. FENG, C. C. FENG, AND Y. H. WANG. 2004. Effects of catchment
characteristics and disturbances on storage and export of dissolved organic carbon in a
boreal headwater stream. Canadian Journal of Fisheries and Aquatic Sciences 61: 1447-
1460.

KAPLAN, L. A., R. A. LARSON, AND T. L. BOTT. 1980. Patterns of dissolved organic carbon.
Limnology and Oceanography 25: 1034-1043.

MARGOLIS, B. E., M. S. CASTRO, AND R. L. RAESLY. 2001. The impact of beaver impoundments
on the water chemistry of two Appalachian streams. Canadian Journal of Fisheries and
Aquatic Sciences 58: 2271-2283.

MAXTED, J. R., C. H. MCCREADY, AND SCARSBROOK. 2005. Effects of small ponds on stream
water quality and macroinvertebrate communities. New Zealand Joumnal of Marine and
Freshwater Research 39: 1069-1084.

MCHALE, M. R., C. P. CIRIVO, M. J. MITCHELL, AND J. J. MCDONNELL. 2004. Wetland nitrogen
dynamics in an Adirondack forested watershed. Hydrological Processes 18: 1853-1870.









velocity and precipitation of OM. In addition, downstream transects 75 and 100 m reside within

a marsh. Calculating baseline stream conditions excluding these transects yielded a much smaller

upstream and downstream mean of 6,600 and 12,000 g/m2, TOSpectively. Using the adjusted

upstream mean, OM storage per area within the pond is almost an order of magnitude greater

than baseline stream conditions (6,600 and 56,000 g/m2, TOSpectively).

Vertical OM profiles for upstream and downstream segments at Unnamed Creek

exhibited an indirect relationship with depth. The interfaces between stream / pond and directly

behind the dam were the exception with vertical profiles exhibiting a direct relationship between

OM and depth (Figure 3-4). Unnamed Creek exhibited the same complex vertical stratification as

Gatling Branch. Thus, each core was similarly divided vertically at the midpoint into larger

upper and lower sections and mean OM calculated for each. Mean upper and lower profiles for

upstream and downstream segments were 10,000 and 8,000 g/m2 and 14,000 and 12,000 g/m2,

respectively. However, mean OM storage for the upper and lower profile at upstream 0 m was

9,000 and 14,000 g/m2, TOSpectively. The OM profile with pond proper was 11,000 and 13,000

g/m2, TOSpectively. However, no significant vertical difference in OM was observed for any

sampling compartment.

Discussion

Investigation of sediment depth and accumulation rates within beaver ponds at Glacier

National Park suggested that sediment volume was strongly correlated with pond area, with rate

of sedimentation greater in ponds than upstream (Butler and Malanson 1995). The longitudinal

OM profile at Unnamed Creek further supports these finding, with greatly increased OM storage

within the pond proper compared to upstream and downstream areas. In contrast, the longitudinal

profile at Gatling Branch was unique in that the downstream segment had the greatest storage per

area basis. This profile is presumed to be the result of a multi-dam system. The relatively close










3-20 Longitudinal distribution of collector/gatherers at Unnamed Creek. ............. .................46

3-21 Longitudinal distribution of filter feeders at Unnamed Creek............. ..__ ........._ ....47

3 -22 Longitudinal distribution of predators at Unnamed Creek. ............_. ......__.............47









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

ROLE OF BEAVER IMPOUNDMENTS IN THE STRUCTURE
AND FUNCTION OF SOUTHERN GEORGIA STREAMS

By

Cody Rick McNeely

December 2007

Chair: Thomas L. Crisman
Major: Interdisciplinary Ecology

The North American beaver (Castor canadensis) is one of the few extant mammals able

to modify its surrounding landscape dramatically, often complicating its relationship with

humans. However, the vast maj ority of research has been limited to north temperate regions,

with almost no data regarding southern beaver populations. The focal point of this study was to

understand the impact beaver impoundments on stream systems of warm temperate regions.

Two sites in Thomasville, Georgia (Gatling Branch and Unnamed Creek) were selected

for this study based on location, morphology, hydrology and active beaver populations.

Sampling was conducted from November 2006 through April 2007, with April capturing the

effects of extensive anthropogenic construction activities. For each system, two 100-m stretches,

upstream and downstream of the beaver pond, and the pond proper were sampled. Measurements

and/or samples included chemical / physical parameters (temperature, dissolved oxygen, specific

conductivity and total suspended solids), macroinvertebrate communities and benthic organic

matter storage. Statistical comparisons were made between compartments (upstream,

downstream and pond), sampling periods and compartments relative to sampling period.

During the pre-anthropogenic disturbance period, few parameters were longitudinally or

temporally significant when compared between sampling compartment and sampling dates.









CHAPTER 4
CONCLUSIONS

The obj ective of this study was to understand the impact of beaver (Castor canadensis)

impoundments on the structure and function of streams in warm temperate, southern Georgia.

The ability of beaver to modify its surrounding landscape considerably has created a complicated

relationship with humans, often leading to wildlife management plans that prescribe their

complete eradication.

Two sites in Thomasville, Georgia were selected for this study (Gatling Branch and

Unnamed Creek), with sampling conducted from November 2006 through April 2007.

Measurements and/or samples included chemical / physical parameters (temperature, dissolved

oxygen, specific conductivity and total suspended solids), macroinvertebrate communities and

benthic organic matter storage. Longitudinal and temporal effects attributed to beaver activity

included changes in dissolved oxygen (DO), invertebrate abundance and benthic organic matter

storage, while effects of construction activities adj acent to pond at Gatling Branch and

immediately downstream included profound changes in water temperature, dissolved oxygen and

suspended solids (turbidity).

Although Maxted et al. (2005) reported increased water temperature within and

downstream of beaver ponds, significant longitudinal changes in temperature were not observed

in Gatling Branch (pre-disturbance) or Unnamed Creek. However, extensive removal of riparian

vegetation along Gatling Branch during human construction activities resulted in increased

sunlight penetration and significant elevation in water temperature within and downstream of the

beaver pond. Observed temporal variations were attributed to external / seasonal influences and

not to beaver activity. As noted by Maxted et al. (2005), decreased dissolved oxygen (DO)

within and downstream of beaver ponds was observed at Gatling Branch and Unnamed Creek.









bacteria that produce cellulase can utilize cellulose in organic matter for energy, creating the

base of the microbial loop. Additional environmental benefits derived from beaver

impoundments include flood control, increased biodiversity and sequestration of organic carbon.

Next to humans, no other extant animal does more to shape its landscape than beaver (Morgan

1986).

This study was conducted because few data or studies on beaver exist for warm temperate

regions. The focal point of this study was to understand how warm-temperate beaver

impoundments in southern Georgia affect organic matter storage, water quality and

macroinvertebrate communities. Investigation of organic matter included quantifying storage

capacity and the potential role of beaver ponds in global carbon cycling. Change in water quality

was assessed by temperature, specific conductivity, dissolved oxygen and turbidity. The structure

and function of macroinvertebrate assemblages included identifying and assigning individuals to

feeding guilds. Previous studies investigating effects of beaver impoundments have been

confined to regions that experience distinct seasonality. This study focused on beaver

impoundments in a region experiencing long growing seasons and moderate winters.









Macroinvertebrates

Samples remained in collection bottles for a minimum of 48 hrs to ensure sufficient

staining with Rose Bengal. To aid in sorting macroinvertebrates, samples were washed through

500-Clm sieves to collect larger and more developed larva, and through 250-Clm sieves to collect

smaller and earlier instar stages. The collected macroinvertebrates were placed into 10-ml glass

vials and labeled with the transect location. Identification was made to lowest practical

taxonomic level to facilitate assignment of individuals to a functional feeding group (Merritt and

Cummings 1996). Using a dissecting microscope, taxonomic identification was determined to

genus for all specimens belonging to the class Insecta. Individuals in the family Chironomidae

were identified to genus after mounting head capsules on slides and using a compound

microscope. Identification was to class and/or family for all other macroinvertebrates.

Statistics

For the purpose of statistical comparison, each system was divided into three treatments;

upstream, downstream and backwater / pond. Using an ANOVA statistical model in SAS,

parameters of organic matter, physical / chemical characteristics and macroinvertebrates were

compared among treatments and sampling dates. Three statistical comparisons were made

relative to treatment: upstream versus downstream, pond versus downstream and upstream

versus pond.









respectively (Figure. 3-9). Mean water temperature was greatest during April (13.9 oC), with

November at 11.1 oC and January at 10.4 oC. Mean longitudinal temperature upstream and

within the pond proper were the same (11.8 oC). Mean temperature was greatest downstream

(12.2 oC). Using an ANOVA model to compare longitudinal temperature between sampling

compartments yielded no statistical significance for any date. However, statistical significance

was noted between longitudinal temperature and sampling period when comparing downstream

and pond segments between January and April and November and April (p<0.001), with

downstream and pond temperature significantly higher during April.

Dissolved oxygen (DO) ranged longitudinally between 1.5 and 3.8 mg/L during

November, with January and April ranging between 5.4 and 7.9 mg/L and 1.1 and 6.5 mg/L,

respectively (Figure. 3-10). Mean DO during April was lowest (2.4 mg/L) and highest during

January (6.8 mg/L). November was intermediate at 2.5 mg/L. Mean longitudinal DO was

greatest upstream and lowest within the pond proper at 4.7 and 3.6 mg/L, respectively. Dissolved

oxygen was intermediate downstream (4.4 mg/L). Using an ANOVA model to compare and

evaluate longitudinal DO between sampling compartments yielded no statistical significance for

any date. However, statistical significance was observed between longitudinal DO and sampling

period when comparing the beaver pond between January and April (p<0.001), with pond DO

significantly greater during the former.

Conductivity ranged longitudinally between 33 and 50 Clm during November, while

January and April ranged between 45 and 52 Clm and 58 and 70 Clm, respectively (Figure. 3-11).

During November, mean conductivity was lowest (38 Clm) and highest during April (65 Clm).

Conductivity during January was intermediate at 48 lm. Mean longitudinal conductivity

upstream and downstream were both 54 Clm, while the pond proper averaged 48 lm. Using SAS























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Figure 3-3. Longitudinal distribution of benthic organic matter at Unnamed Creek.


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0 60


Legend
[ii 2500 7500
O 7500 10000
H 10000 -12500
H 1250-500 -100
5 15000 -17500
Units: g/m2


Figure 3-4. Vertical distribution of benthic organic matter at Unnamed Creek.










































I I Meters


"~~CA enBavesr Pond


SUnnarned Creek

J I /County Boundaries
"';~i e ~ \\Thomas County


460 690


920


Figure 2-2. Aerial map of Unnamed Creek.









However, effects resulting from beaver activity included changes in organic matter (OM)

storage, dissolved oxygen (DO) and invertebrate abundance. Mean upstream OM storage at

Unnamed Creek was 6,600 g/m2, while storage within the pond proper increased to 56,000 g/m2,

almost an order of magnitude greater. Longitudinal DO at Gatling Branch decreased from 7.6

mg/L upstream to 3.2 mg/L within impounded areas, and was attributed to increased OM

loading. Responding to changes in DO, invertebrate abundance at Gatling Branch decreased

from 94,000 invertebrates/m2 upstream to 24,000 invertebrates/m2 within the backwater / pond.

Longitudinal and temporal effects attributed to human construction activities adj acent to

and immediately downstream of the beaver pond at Gatling Branch included intense changes in

water temperature, dissolved oxygen, suspended solids (turbidity) and invertebrate abundance.

During April, mean water temperature increased from 16oC in undisturbed sections of the stream

to over 22oC within backwater / pond and downstream segments. During the same sampling

period, mean DO decreased from 6.8 mg/L upstream to 3.9 mg/L within the pond, while mean

turbidity increased from 4.6 NTU upstream to 14.7 NTU within and downstream of the beaver

pond. In response to these chemical / physical changes, invertebrate abundance during April

decreased from 162,000 individuals/m2 upstream to 28,000 individuals/m2 within the backwater /

pond area.

During this study, the effects of beaver impoundments were limited to invertebrate

abundance, dissolved oxygen and OM storage. Conversely, anthropogenic disturbances appear to

have much greater effect on stream systems, with dramatic changes in temperature, dissolved

oxygen, turbidity and invertebrate communities. Finally, the OM and carbon sequestration

potential of these beaver impoundments was tremendous and may offer an overlooked

component to counter global climate change.






































0 375 750


Legend

SBeaver Pond
Roads

SGatling Branch
SCounty Boundar-ies
Thornas County


1,500 2,250 3,000


Figure 2-1. Aerial map of Gatling Branch.









CHAPTER 3
RESULTS AND DISCUSSION

Benthic Organic Matter

Gatling Branch

The study area at Gatling Branch consisted of 350 m of stream channel and three

impoundments. The main impoundment (Pond 10) was the largest and most central. A second

and slightly smaller impoundment was approximately 250 m upstream (BW225) of the beaver

pond. The third and smallest impoundment was located 100 m downstream (DS 100) of the

beaver pond.

Spatial differences in organic matter (OM) occurred longitudinally throughout the

system, with storage greatest at stream / impoundment interface. Correspondingly, OM storage at

the main impoundment / stream interface was 57,000 g/m2 (Pond 10), while storage at the stream

interface for the two smaller impoundments was 59,000 (BW225), and 53,000 (DS100) g/m2

(Figure. 3-1). Mean OM storage was greatest downstream of the beaver pond (3 8,000 g/m2)

while storage for upstream and backwater / pond were 13,000 and 35,000 g/m2, TOSpectively.

Transects 0 and 10 m upstream (23,000 and 21,000 g/m2, TOSpectively) heavily influenced mean

upstream storage, presumably due to the abrupt decease in velocity and precipitation of OM.

Using the 25, 50, 75 and 100-m transects as a baseline for normal stream condition, a much

smaller upstream mean of 8, 100 g/m2 was calculated. Using an ANOVA model in SAS,

significant longitudinal effects on OM storage were observed between downstream versus

upstream and pond versus upstream (p<0.03) and (p<0.02), respectively, with downstream and

pond segments having significantly greater OM storage compared to upstream. The pond was not

significantly different from downstream.









transect. No statistical significance between longitudinal taxonomic richness and sampling

compartment was observed. However, statistical significance was observed between taxonomic

richness and sampling period. Comparing upstream segments between January and April yielded

significance of (p<0.002), with mean upstream richness greater during April compared to

January (7.3 and 3 taxa, respectively). Statistical significance in richness was not observed for

any other sampling compartment or period.

Three maj or feeding guilds were present at Unnamed Creek: collector/gatherers, filterer

feeders and predators. In contrast to Gatling Branch, collector/gatherers at Unnamed Creek did

not dominate all sampling compartments and dates, instead filter feeders accounted for 12 to 44

percent of total invertebrates. Mean abundance of collector/gatherers was greatest during

November, with an average of 20,000 individuals/m2. Abundance during January and April were

nearly identical, averaging 14,000 and 12,500 individuals/m2, TOSpectively. Mean abundances of

filter feeders was greatest during April and lowest during November, with 7,000 and 2,400

individuals/m2, TOSpectively. Abundance of filter feeders was intermediate during January with

5, 100 individuals/m2. Mean abundance of predators during January and April were similar, with

1,200 and 1,350 individuals/m2, TOSpectively. Predator abundance was lowest during November

at 640 individuals/m2

Mean upstream and pond abundances of collector/gatherers were similar, averaging

20,000 and 18,500 individuals/m2, TOSpectively. Longitudinal abundance of collector/gatherers

was lowest downstream with 9, 100 individuals/m2 (Figure 3-20). Filter feeder abundance was

greatest upstream and lowest within the pond, averaging 6,400 and 3,200 individuals/m2,

respectively. Downstream abundance was intermediate at 4,500 individuals/m2 (Figure. 3-21).

Mean predator abundance was lowest within the pond proper at 670 individuals/m2, while















55



8 450
O
35

25
0c a~ an O



Transect


+ Nov-06 -m- Jan-07 + Apr-07


+ Nov-06 + Jan-07 + Apr-07


Figure 3-7. Longitudinal specific conductivity profile for Gatling Branch.


18

15

S12


9

6

3


8 a w a O O a 8



Transect


Figure 3-8. Longitudinal turbidity profile for Gatling Branch.

































-o- Nov-06 -m- Jan-07 Apr-07


SNov-06 + Jan-07 + Apr-07


80

70

S60

350
C
0 40
O

30

20


0~ ~ a a

Transect


Figure 3-11. Longitudinal specific conductivity profile for Unnamed Creek.


12

10

8

6




2

0


0~~ a a a

Transect


Figure 3-12. Longitudinal turbidity profile for Unnamed Creek.









individuals/m2, TOSpectively (Figure. 3-15). Longitudinal abundance of filter feeders was greatest

upstream and lowest within the pond / backwater with 4,000 and 950 individuals/m2,

respectively. Abundance of filter feeders was intermediate downstream, averaging 1,500

individuals/m2 (Figure. 3-16). Upstream and downstream predator abundance averaged of 2,000

and 660 individuals/cm2, TOSpectively, while average abundance was lowest within the backwater

/ pond segments at 370 individuals/m2 (Figure. 3-17). However, using an ANOVA model for

statistical analysis, no significance between functional feeding groups and sampling

compartment or sampling date was observed.

Unnamed Creek

Mean invertebrate abundance was greatest during November with 23,000 individuals/m2,

while mean abundance for both January and April was 21,000 invertebrates/m2 (Figure. 3-18).

Mean longitudinal abundance was greatest upstream and lowest downstream with 27,900 and

14,800 invertebrates/m2, TOSpectively. The pond proper was intermediate with 22,400

invertebrates/m2. Using an ANOVA model to analyze and compare longitudinal abundance

between sampling compartments yielded no statistical significance. However, statistical

significance was observed between longitudinal abundance and sampling period, when

comparing upstream segments between November and January and April and January (p<0.04)

and (p<0.001), respectively, with upstream abundance during November and April significantly

greater than January (29,500, 42,000 and 11,900 invertebrates/m2, TOSpectively). No temporal

significance was observed between pond and downstream segments for any sampling period.

Taxonomic richness was greatest during April, averaging 5.5 families throughout the

system, while November and January were similar at 3.9 and 4. 1 families, respectively (Figure.

3-19). Mean taxa richness was greatest upstream, averaging 4.8 families per transect.

Downstream and pond richness were the same, with an average of 4.3 invertebrate families per










upstream and downstream averaged 1,300 and 1,100 individuals/m2, TOSpectively (Figure. 3-22).

Using an ANOVA model for statistical analysis, no significance between functional feeding

groups and sampling compartment or sampling date was observed.

Discussion

The relative abundance of macroinvertebrates was significantly elevated in Ontario

beaver ponds, and was attributed to accumulation of coarse woody debris and trapped sediment

within impounded areas (France 1997). However, research Einding by Collen and Gibson (2001),

suggested that invertebrate abundance within beaver ponds decreased per unit area, when

compared to the upstream reach. Similarly, relative abundance of macroinvertebrates within

impounded areas at Gatling Branch was dramatically lower for all sampling periods, while no

significant longitudinal change in abundance was observed in Unnamed Creek. Upstream and

backwater / pond abundance at Gatling Branch averaged 94,000 and 23,600 individuals/m2,

respectively. Longitudinal changes in relative abundance were attributed to decreased DO within

impounded areas. Upstream DO at Gatling Branch averaged 7.6 mg/L, while decreasing to 3.2

mg/L within the beaver pond.

France (1997) suggested increased taxonomic richness within beaver ponds that was

attributed to accumulation of organic debris and trapped sediment within impounded areas,

promoting increased habitat heterogeneity. No significant longitudinal changes in taxonomic

richness at Gatling Branch or Unnamed Creek were observed during this study. However,

temporal significance was noticed between January and April for both Gatling Branch and

Unnamed Creek. Greater upstream richness during April was attributed to longitudinal changes

in dissolved oxygen and the ability to capture larger / more developed instar stages of

invertebrates.









ROLE OF BEAVER IMPOUNDMENTS IN THE STRUCTURE AND
FUNCTION OF SOUTHERN GEORGIA STREAMS























By

CODY RICK McNEELY


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

2007









least 350 m of stream and sequestered more than 42,800 kg of organic matter. In addition, the

single impoundment at Unnamed Creek influenced at least 175 m of stream, sequestering more

than 124,000 kg of organic matter. Beaver activity at Gatling Branch and Unnamed Creek had a

tremendous influence on the longitudinal and vertical distribution of OM, demonstrating the

storage potential of these systems. Serving as large OM (i.e. carbon) sinks, beaver ponds offer an

overlooked component to the complicated problem of global climate change.

Physical Chemical Parameters

Spatial differences in physical and chemical parameters occurred both longitudinally and

temporally in Gatling Branch and Unnamed Creek. November 2006 and January 2007 data for

Gatling Branch were collected prior to anthropogenic disturbance, while April recorded the

effects of extensive construction activities adj acent to pond and downstream transects that began

in mid January 2007. For statistical analysis, each system was divided into three compartments:

upstream, downstream and backwater / pond.

Gatling Branch

Water temperature in Gatling Branch ranged longitudinally between 14.3 and 14.9 oC

during November, while January and April ranged between 9.1 and 10.9 oC and 16.9 and 24.9

oC, respectively (Figure. 3-5). Mean water temperature was 14.7 oC during November, while

January dropped to 10.1 oC. Water temperature was greatest during April (19.4 oC). Mean

longitudinal temperature was greatest within backwater / pond (15.3 oC), with upstream and

downstream segments averaging 14.1 and 14.7 oC, respectively. Using an ANOVA model in

SAS to analyze and compare longitudinal temperature between sampling compartments yielded

no statistical significance for any date. However, statistical significance was observed between

longitudinal temperature and sampling period when comparing downstream and pond segments

between November and April and January and April (p<0.005) and (p<0.001), respectively, with











00

00

00

00

00

00

00


nn ~





Transect


-o- Series 1 + Series2 + Series3


'


+ Nov-06 +e Jan-07 + Apr-07


800


S70(

S60(

E 50(

30

20(
Ca,
- lu(


Figure 3-17. Longitudinal distribution of predators at Gatling Branch.


70000

S60000

g 50000

S40000

S30000

S20000

-10000


0


Transect


Y
O O O O
~n o
(I)
C~ (I) (I)
C~ C~ (I)


Figure 3-18. Longitudinal invertebrate distribution for Unnamed Creek.












45000

37500

S30000


en 22500


8 1sooo



0 0

Trasec


-o Novem ber -m- January -6-April


-o- November -m- January -6 April


Figure 3-21. Longitudinal distribution of filter feeders at Unnamed Creek.


12000


mE10000

.0 8000
E
C
6000


-4000

-c2000

0


0 0 a a a


Transect


O O O O
~n o
(I)
C~ (I) (I)
C~ C~ (I)


Figure 3-22. Longitudinal distribution of predators at Unnamed Creek.









beaver impoundments suggests that beaver have a profound ecological role, ultimately

controlling biological structure within its zone of influence.

In addition to localized changes in ecosystem structure and function, sequestration of

organic matter (OM) within beaver ponds may have global implications. Sequestered organic

matter in aquatic systems (i.e. beaver ponds) represents a significant component of the global

carbon pool, helping to regulate emissions of CO2 and CH4 into the atmosphere through

photosynthetic and respiratory processes (Amundson 2001). Organic carbon storage at Unnamed

Creek occurred at a rate 10 times greater within the pond than upstream, further demonstrating

the storage potential of beaver impoundments. Although the ultimate fate of stored OM is

unknown, this vast carbon storage potential clearly offers an overlooked compartment in the

mitigation of climate change.


































+ Nov-06 +e Jan-07 + Apr-07


250000

"E
2 200000

E
S150000




a, 50000

0


c o o W .. r- C\I 3 o o o o

O Transect


Figure 3-13. Longitudinal invertebrate distribution for Gatling Branch.


8)

V6
Cu



E
o

X2c

c ouc.. -co


O n 0 0 c
Trasec


como


-o- Nov-06 -m Jan-07 -6- Apr-07


Figure 3-14. Longitudinal taxonomic distribution for Gatling Branch.









Physical Chemical Parameters

Physical / chemical parameters (temperature, dissolved oxygen and specific conductivity)

were measured in situ using a YSI 585 field probe. Total suspended solids (turbidity) was

measured in the laboratory by analyzing a 25-ml water sample using a LaMotte 2020

Turbidimeter, and results were reported in nephelometric turbidity units (NTU's). Measurements

from Unnamed Creek were taken at 0, 10, 50, and 100 m upstream and downstream of the beaver

pond. Three additional measurements were taken within the pond at randomly selected locations.

Because of the extensive backwater area at Gatling Branch, measurements were taken at 10, 50,

and 100 m upstream of the beaver pond and 0, 10, 50 and 100 m downstream of the

impoundment. Physical / chemical parameters were not taken at the 0-m upstream transect.

However, two measurements were taken from within the backwater area 10 m upstream from the

pond (BWUSP) and 10 m downstream from the upstream 0-m transect (BWDSE). Three

additional measurements were taken within the pond at randomly selected locations.

Measurements and sample collection began at the 100-m downstream transect and proceeded

upstream to avoid sampling interference between segments.

Laboratory Methods

Loss on Ignition (LOI) Analysis

BOM cores were divided longitudinally into 10-cm segments and homogenized using a

standard mortar and pistil. One sub-sample of 5 cm3 was taken from each homogenized segment

and dried at 60 OC for 48 hrs. Upon removal, a dry weight was obtained using an analytical

balance measuring to three decimals. Each sample was then combusted in a muffle furnace at

550 oC for 5 hrs. Samples were allowed to cool in a desiccator for 8 hrs and weighed again to

obtain ash free dry weight.









The vertical OM profiles for upstream, backwater / pond and downstream exhibited an

indirect relationship with depth, with the exception of the interface between stream and

impoundments, which exhibited a direct relationship between OM and depth (Figure 3-2).

Complex vertical stratification presented difficulties in analyzing core segments. Thus, each core

was divided vertically at the midpoint into larger upper and lower sections, and mean OM for

each section was calculated. Mean OM storage for the upper and lower profile for upstream and

downstream segments were 4,500 and 2,200 g/m2 and 6,900 and 6,000 g/m2, TOSpectively. Mean

backwater / pond storage was 7,000 and 6,100 g/m2, TOSpectively. However, mean OM storage

for the upper and lower profile at upstream 0 m was 5,600 and 8,000 g/m2, TOSpectively. Storage

profiles for both minor impoundments were 5,300 and 9,300 g/m2 (BW225) and 9,200 and

11,000 g/m2 (DS100), respectively. The main impoundment (Pondl0) had an upper and lower

profile of 2,600 and 8,900 g/m2, TOSpectively. However, no significant vertical difference in OM

was observed for any sampling compartment.

Unnamed Creek

Spatial differences in organic matter (OM) storage occurred longitudinally throughout

Unnamed Creek. Storage was greatest at the upstream / pond interface and directly behind the

beaver dam, averaging 93,000 and 71,000 g/m2, TOSpectively (Figure 3-3). Mean OM storage was

greatest within the pond proper (56,000 g/m2), while upstream and downstream storage were

37,000 and 18,000 g/m2, TOSpectively. Using an ANOVA model, significant longitudinal effects

on OM storage were observed between pond versus upstream and pond versus downstream

(p<0.001), with the pond having significantly greater OM storage compared to upstream and

downstream segments. No statistical significance in OM storage was observed between upstream

and downstream segments. Transects 0 and 10 m upstream (93,000 and 92,000 g/m2,

respectively) heavily influenced mean upstream storage, presumably due to the abrupt decease in































SNov-06 +e Jan-07 -6 Apr-07


-o- Nov-06 -m- Jan-07 -6 Apr-07


23

ov20



E1 14

11

8 v Y
coome. 0000~~


Transect


Figure 3-5. Longitudinal temperature profile for Gatling Branch.


10





X 6


4


O \ Y




Transeacts


Figure 3-6. Longitudinal dissolved oxygen profile for Gatling Branch.









Gatling Branch. Analogous to previous months, increased lateral input of fine particulate organic

matter (FPOM) from construction resulted in increased decomposition and biological demand for

oxygen.

The January sampling period at Gatling Branch yielded very different results, with almost

no longitudinal change in dissolved oxygen. During this period, water flowed unimpeded

through degraded sections of the beaver dam. This continuous flow prevented depletion of DO

within the backwater / pond area, resulting in little longitudinal variation. Temporal differences

in mean DO at Gatling Branch and Unnamed Creek between November, January and April are

assumed to be the result of seasonal variation in ambient / water temperature and resulting

changes in saturation of oxygen into water.

The conductive properties of aquatic environments are principally controlled by

watershed geology, soil composition and vegetation. Thus, anion and cation strength (i.e.

specific conductivity) is the result of weathered rock, biogeochemical interactions within the soil

matrix and the storage potential of adj acent terrestrial landscapes. Longitudinal stability of

specific conductivity at Unnamed Creek for all sampling compartments and sampling periods is

presumed the result of stability within the watersheds geology, soils, vegetation and storage

capacity .

Contrary to Unnamed Creek, conductivity during November and April at Gatling Branch

increased within the backwater / pond and downstream segments. The observed increase in

conductivity during November is presumed to be the result of warmer water temperatures,

increased organic decomposition and production of ions within impounded areas. However,

during April, ion storage capacity of the adj acent riparian zone was altered with the near

complete removal of riparian vegetation during construction. When combined with the poor









to compare and analyze longitudinal conductivity between sampling compartments and sampling

periods yielded no statistical significance.

Turbidity at Unnamed Creek ranged longitudinally between 2.3 and 4. 1 NTU during

November, with January and April ranging between 3.1 and 5.3 NTU and 5.0 and 10. 1 NTU,

respectively (Figure. 3-12). Mean turbidity levels during November and January were similar,

3.0 and 3.9 NTU, respectively. Turbidity was greatest during April at 6.1 NTU. Mean

longitudinal turbidity was greatest downstream and lowest within the pond proper at 7.0 and 3.8

NTU, respectively. Turbidity was intermediate upstream, averaging 4.4 NTU. Using an ANOVA

model to evaluate longitudinal turbidity between sampling compartments yielded statistical

significance for downstream versus pond segments (p<0.002), with downstream having greater

turbidity. In addition, statistical significance was observed between turbidity and sampling

period when comparing downstream segments between January and April (p<0.001), with the

latter having significantly increased turbidity downstream.

Discussion

According to research by Maxted et al. (2005), water temperatures in beaver ponds and

downstream fluctuate seasonally, with longitudinal temperatures being stable during winter and

elevated during summer. Increased water temperature was attributed to larger surface area of

ponds and increased adsorption of solar radiation during summer. Longitudinal variation in water

temperature at Unnamed Creek followed this pattern. Upstream and downstream riparian zones

created a nearly closed canopy and provided longitudinal stability in temperature during

November and January, while the large surface area of the beaver pond and limited canopy

protection from the riparian zone allowed for increased sunlight penetration and elevated

temperatures during April.









resulting difficultly in collecting a non-contaminated sampling. Thus, transects DSO, DS10 and

DS50 were omitted from the April dataset at Unnamed Creek.

Macroinvertebrates

Spatial differences in macroinvertebrate communities occurred both longitudinally and

temporally in Gatling Branch and Unnamed Creek. November 2006 and January 2007 sampling

for Gatling Branch were prior to anthropogenic disturbance, while April 2007 recorded the

effects of extensive construction activities adj acent to pond and downstream transects that began

in mid January 2007. Analyses included changes in abundance, taxonomic richness and feeding

guilds, as well as trends within individual invertebrate groups. For statistical analysis, each

system was divided into three compartments: upstream, downstream and backwater / pond.

Gatling Branch

Mean abundance was greatest during April and lowest during January at 68,500 and

25,500 invertebrates/m2, TOSpectively. November was intermediate at 54,000 invertebrates/m2

(Figure. 3-13). Mean longitudinal abundance was greatest upstream (94,000 invertebrates/m2)

while downstream and backwater / pond segments averaged 30,000 and 23,600 invertebrates/m2,

respectively. Using an ANOVA model to analyze and compare longitudinal abundance between

sampling compartments yielded statistical significance for pond versus upstream and

downstream versus upstream segments (p<0.001), with upstream invertebrate abundance

significantly greater than pond and downstream. No significance was observed between pond

and downstream segments. However, statistical significance was observed between longitudinal

abundance and sampling period when comparing upstream segments between November and

January (p<0.04), November and April (p<0.002) and January and April (p<0.001), with

upstream abundance during April significantly greater than November and January (162,000,










upstream segments, (p<0.03) and (p<0.004), respectively, with pond and downstream segments

having higher conductivity. No statistical significance in conductivity was observed in pond

versus downstream. However, statistical significance was observed between longitudinal

conductivity and sampling period when comparing downstream segments between November

and April and January and April (p<0.001), with downstream conductivity greater during April.

No significant temporal changes were observed between November and January sampling

periods.

Turbidity at Gatling Branch ranged longitudinally between 5.1 and 9.0 NTU during

November, while January and April ranged between 5.4 and 7.0 NTU and 4.4 and 16.2 NTU,

respectively (Figure. 3-8). Mean turbidity levels during November and January were similar, 6.0

and 6.5 NTU, respectively, and greatest during April at 10.8 NTU. Mean longitudinal turbidity

was greatest downstream and lowest upstream at 8.9 and 5.8 NTU, respectively. Turbidity was

intermediate within backwater / pond (8.6 NTU). Using an ANOVA model to evaluate

longitudinal turbidity between sampling compartments yielded statistical significance for

downstream versus upstream and pond versus upstream segments (p<0.001), with pond and

downstream segments having significantly greater turbidity. No statistical significance in

turbidity was observed in pond versus downstream. However, statistical significance was

observed between turbidity and sampling period when comparing downstream and pond

segments between November and April and January and April (p<0.001), with pond and

downstream turbidity significantly higher during April. No temporal significance was observed

between November and January.

Unnamed Creek

Water temperature in Unnamed Creek ranged longitudinally between 10.4 and 12.9 oC

during November. January and April ranged between 9.2 and 11.4 oC and 11.4 and 15.7 oC,












10





.- 6


0 4



C i CC







Transect

+ Nov-06 + Jan-07 + Apr-07


Figure 3-19. Longitudinal taxonomic distribution for Unnamed Creek.


70000

60000

$ 50000

S40000

S30000



0

S1 0 0 0,- 00



O O O O TransctC
-o Noeme -m- Jaur o pi

Fiur 32.oniudnaisriuion of colcor/ahrr at Unamdrek









CHAPTER 1
INTTRODUCTION

The late nineteenth and early twentieth centuries witnessed the decline of the North

American beaver from most waterways. Intense human pressure caused the demise of beaver and

left many streams without nature's wetland engineers for almost a century. Among the most

heavily influenced beaver populations were those of the southeastern United States, with

complete extirpation from some regions by the early twentieth century. An aggressive

conservation program has helped North American beaver populations recover. Extensive

migration to southeastern waterways and establishment of healthy populations are prime

evidence of successful conservation efforts (Everett and Schaefer 2006).

As semi-aquatic rodents native to North America and Europe, beaver are the only living

members of the family Castoridae, which contains the single genus Castor. Beavers inhabit

riparian zones of streams as well as the channel. Families typically consist of around eight

members with adults weighing up to 25 kg. The health and productivity of aquatic ecosystems

depend in part on the influence of beaver. Functioning as a keystone species by creating wetland

habitat (McHale et al., 2004), beaver are best known for construction of dams in streams and

lodges in the ponds that form. Construction of lodges is common in temperate regions, with bank

dwelling more prevalent in warm southern regions. Beaver dams are created both as protection

against predators and to provide food access during winter. During dam and lodge construction,

beaver selectively remove riparian tress, creating gaps in canopy cover. This facilitates

macrophyte colonization and proliferation in beaver ponds, resulting in altered nutrient cycling

and aquatic food webs (Ray et al., 2001).

Nutrient sequestration is often considered the most valuable function of a beaver pond. In

addition, beaver ponds accumulate vast quantities of inorganic and organic matter. However,









ACKNOWLEDGMENTS

I would like to express my sincere gratitude to Dr. Thomas Crisman, for his guidance and

editorial assistance made this study possible. In addition, I would like to express my appreciation

to William White and Marcus Griswold, each my friend and colleague, for their field and

laboratory assistance. Finally, I would like to give special thanks to Steve Everett, for his

knowledge and passion in beaver research provided the inspiration for this study.










LIST OF FIGURES


Figure page

2-1 Aerial map of Gatling Branch ................. ...............16...............

2-2 Aerial map of Unnamed Creek. ............. ...............17.....

2-3 Longitudinal profile of water depth at Gatling Branch ......... ................. ...............18

2-4 Longitudinal profile of water depth at Unnamed Creek ................. .........................18

3-1 Longitudinal distribution of benthic organic matter at Gatling Branch. ................... .........3 7

3-2 Vertical distribution of benthic organic matter at Gatling Branch. ............. ..................37

3-3 Longitudinal distribution of benthic organic matter at Unnamed Creek. ..........................38

3-4 Vertical distribution of benthic organic matter at Unnamed Creek ................. ...............38

3-5 Longitudinal temperature profile for Gatling Branch ................. ......... ................39

3-6 Longitudinal dissolved oxygen profile for Gatling Branch. ................... ...............3

3-7 Longitudinal specific conductivity profile for Gatling Branch............... .................4

3-8 Longitudinal turbidity profile for Gatling Branch. ............. ...............40.....

3-9 Longitudinal temperature profile for Unnamed Creek. ............. ...............41.....

3-10 Longitudinal dissolved oxygen profile for Unnamed Creek ................. ............. .......41

3-11 Longitudinal specific conductivity profile for Unnamed Creek. ................... ...............42

3-12 Longitudinal turbidity profile for Unnamed Creek ................. .............................42

3-13 Longitudinal invertebrate distribution for Gatling Branch. ................... ...............4

3-14 Longitudinal taxonomic distribution for Gatling Branch. ............. .....................4

3-15 Longitudinal distribution of collector/gatherers at Gatling Branch ................. ...............44

3-16 Longitudinal distribution of filter feeders at Gatling Branch. ................ ............... .....44

3-17 Longitudinal distribution of predators at Gatling Branch ................. .......................45

3-18 Longitudinal invertebrate distribution for Unnamed Creek. ....._____ ...... .....__.........45

3-19 Longitudinal taxonomic distribution for Unnamed Creek ................. .......__. ..........46









Margolis et al (2001) studied the effects of beaver impoundments on macroinvertebrate

communities of low order Appalachian streams and found that pond and downstream taxonomic

composition and functional feeding groups were strongly correlated with water temperature,

chemistry and dissolved oxygen. Neither Gatling Branch nor Unnamed Creek exhibited

significant longitudinal change in taxa composition or dominate feeding groups, even though

longitudinal and temporal changes in temperature and DO were observed. However, analogous

to relative abundance, significant reduction in abundance within and downstream of the beaver

pond was observed for each feeding group (collector/gatherers, filterers and predators).

Correspondingly, longitudinal changes in the abundance of collector/gatherers and filterers were

attributed to decreased DO within impounded areas. However, longitudinal change in predator

abundance was attributed to the inability for the dominant genus Probezzia spp. (lotic) to inhabit

the deeper waters of the impounded areas (lentic), presumably causing the dramatic reduction of

predators within the beaver ponds (Merritt and Cummings 1996).









downstream and pond temperature significantly greater during April. No temporal significance

was observed between November and January.

Dissolved oxygen (DO) ranged longitudinally between 2.3 and 7.3 mg/L during

November, with January and April ranging between 8.3 and 9.1 mg/L and 3.6 and 7.0 mg/L,

respectively (Figure. 3-6). Mean DO during November was lowest (4.5 mg/L) and January

highest (8.8 mg/L). Dissolved oxygen was intermediate during April at 5.4 mg/L. Mean

longitudinal DO was greatest upstream and lowest within backwater / pond at 7.6 and 5.2 mg/L,

respectively. Dissolved oxygen was intermediate downstream with an average of 5.8 mg/L.

Using an ANOVA model to analyze longitudinal DO between sampling compartments yielded

statistical significance for downstream versus upstream and pond versus upstream segments

(p<0.001), with the upstream having significantly greater DO than pond and downstream. No

statistical significance in DO was observed in pond versus downstream. In addition, statistical

significance was observed between longitudinal DO and sampling period when comparing

downstream and pond segments between November and January and April and January

(p<0.001), with downstream and pond DO significantly greater during January. Comparisons

between November and April sampling periods yielded no temporal significance.

Specific conductivity ranged longitudinally between 45 and 58 Clm during November.

January and April ranged between 40 and 43 Clm and 63 and 80 Clm, respectively (Figure. 3-7).

Mean conductivity during November was intermediate at 54 lm. During January, mean

conductivity was lowest (42 Clm) and during April highest (70 Clm). Mean longitudinal

conductivity was the same for backwater / pond and downstream segments at 57 Clm, while

upstream averaged 52 lm. Using SAS to analyze and evaluate conductivity between sampling

compartments yielded statistical significance for downstream versus upstream and pond versus












TABLE OF CONTENTS


page


ACKNOWLEDGMENTS .............. ...............3.....


LIST OF FIGURES .............. ...............5.....


AB S TRAC T ......_ ................. ............_........7


CHAPTER


1 INTRODUCTION ................. ...............9.......... ......


2 MATERIALS AND METHODS ................. ...............11.......... ....


Site Description ................. ...............11.......... .....
Gatling Branch ................. ...............11.................
Unnamed Creek ................. ...............12.......... ......
Field M ethods ................. ............. .... ...............12.....

Organi c Matter and S edimentati on ................. ...............13........... ..
Macroinvertebrate Communities ................ ...............13.................

Physical Chemical Parameters .............. ...............14....
Laboratory M ethods................. .... .............1
Loss on Ignition (LOI) Analysis............... ...............14
M acroinvertebrates ................. ...............15.......... .....
Stati sti cs ................. ...............15........... ....


3 RE SULT S AND DI SCU SSION ............... .............. 1


Benthic Organic Matter .............. ...............19....
Gatling Branch ................. ...............19.................
Unnamed Creek ................. ...............20.......... ......
Discussion ................. .......... ...............21.......

Physical Chemical Parameters ................. ...............23................
Gatling Branch............... ...............23.
Unnamed Creek ................. ...............25.......... ......
Discussion ................. ...............27.................
M acroinvertebrates .............. ...............3 1....

Gatling Branch ................. ...............3.. 1..............
Unnamed Creek ................. ...............3.. 3..............
Discussion ................. ...............35.................


4 CONCLUSIONS .............. ...............48....


LIST OF REFERENCES ................. ...............51................


BIOGRAPHICAL SKETCH .............. ...............53....





175


150

S125

5 100


0 50 100 150 200 250 300 350 400 450
Distance (m)

-o Novem ber January +- April


Figure 2-3. Longitudinal profile of water depth at Gatling Branch.


210

180

S150

5 120

90


0 25 50 75 100 125 150 175 200 225 250 275
Distance (m)

-o November -e- January April


Figure 2-4. Longitudinal profile of water depth at Unnamed Creek









Unnamed Creek

Unnamed Creek is a low gradient, second-order stream (Strahler method) located in

Thomasville, Georgia (300 52' 32.1" N, 83o 56' 30.7" W). The principal headwater originates

from a seepage wetland, while a secondary headwater originates from channelized overland

flow. Both stream channels flow north to a confluence south of US 84 bypass (Figure 2-2).

USGS classified the flow regime of Unnamed Creek (HUC 3 120002) as intermittent. Mean

bankfull width and mean water depth are 2.1 m and 28 cm, respectively. However, mean water

depth within the reach of stream influenced by beaver activity increased to 55.5 cm (Figure. 2-4).

The substrate of the stream channel is predominantly sand and clay with increasing organic

content approaching the beaver pond from upstream. The stream channel is fully canopied with a

riparian zone dominated by water oak (Quercus nigra), sweetgum (Liquidambar~~~dddd~~~~ddd styraciflua), red

maple (Acer rubrum) and longleaf pine (Pinus palustris). The beaver pond has an approximate

surface area of 2,900 m2 and is located 0. 16 kilometers north of US 35. Constructed primarily

from wood, the dam stands at a height of 0.65 m. Water discharge occurred predominantly as

surface overflow with almost no discharge from the base of the dam.

Field Methods

For each stream, two 100-m stretches, upstream and downstream of the beaver pond and

the beaver pond proper were sampled. Sampling was conducted at Gatling Branch and Unnamed

Creek three times from November 2006 through April 2007 (3 and 4 November 2006, 13 and 14

January 2007 and 6 and 7 April 2007). Benthic organic matter was sampled once at the

beginning of the study. Fieldwork required two days per site, 13 and 14 October 2006 for Gatling

Branch and 20 and 21 October 2006 for Unnamed Creek.









CHAPTER 2
MATERIALS AND IVETHODS

Site Description

Two sites in southern Georgia were selected for this study, Gatling Branch and Unnamed

Creek, based on geographical location, morphology, hydrologic regimes and accessibility. In

addition, both sites had an active beaver population prior to the study that provided

impoundment maintenance and presumed long-term sustainability.

Gatling Branch

Gatling Branch is a low gradient, second-order stream (Strahler method) located in

Thomas County, Georgia (300 5 1' 1 1.3"' N, 83o 54' 00.6"' W). Headwaters of the two first order

streams originate from seepage wetlands and flow south to their confluence north of Georgia

state road 122 (Figure 2-1). USGS (U.S. Geological Survey) classified the flow regime of

Gatling Branch (HUC 3110103) as intermittent, and it has mean bankfull width and mean water

depth of 4.7 m and 9.8 cm, respectively. However, mean water depth within the reach of stream

influenced by beaver activity increased to 46.4 cm (Figure. 2-3). The substrate of the stream

channel is predominantly sand with increasing organic content approaching the beaver pond

from upstream. Upstream of the beaver pond, the channel is fully canopied, and the riparian zone

is dominated by water oak (Quercus nigra), sweetgum (Liquidambar~~~dddd~~~~ddd styraciflua) and willow

(Salix caroliniana). The canopy downstream is sparse and dominated by tulip poplar

(Liriodendron tulipifera). The beaver pond has an approximate surface area of 80 m2 and is

located 1.5 kilometers south of Georgia state road 122. In addition, this site has an extensive

backwater area, extending approximately 250 m upstream of the pond proper. Constructed

primarily from wood and mud, the dam stood an impressive 1.5 m high. Water discharge

occurred predominantly at the base of the dam with surface overflow only during high water.




Full Text

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1 ROLE OF BEAVER IMPOUNDMENTS IN THE STRUCTURE AND FUNCTION OF SOUTHERN GEORGIA STREAMS By CODY RICK McNEELY 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 2007

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2 2007 Cody Rick McNeely

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3 ACKNOWLEDGMENTS I would like to express my sincere gratitude to Dr. Thomas Crisman, for his guidance and editorial assistance made this study possible. In addition, I would like to express my appreciation to William White and Marcus Griswold, each my friend and colleague, for their field and laboratory assistance. Finally, I would like to give special tha nks to Steve Everett, for his knowledge and passion in beaver research provided the inspiration for this study.

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4 TABLE OF CONTENTS page ACKNOWLEDGMENTS...............................................................................................................3 LIST OF FIGURES.........................................................................................................................5 ABSTRACT.....................................................................................................................................7 CHAP TER 1 INTRODUCTION....................................................................................................................9 2 MATERIALS AND METHODS........................................................................................... 11 Site Description......................................................................................................................11 Gatling Branch.................................................................................................................11 Unnamed Creek............................................................................................................... 12 Field Methods.........................................................................................................................12 Organic Matter and Sedimentation.................................................................................. 13 Macroinvertebrate Communities..................................................................................... 13 Physical Chemical Parameters.....................................................................................14 Laboratory Methods............................................................................................................. ...14 Loss on Ignition (LOI) Analysis...................................................................................... 14 Macroinvertebrates..........................................................................................................15 Statistics..................................................................................................................................15 3 RESULTS AND DISCUSSION............................................................................................. 19 Benthic Organic Matter..........................................................................................................19 Gatling Branch.................................................................................................................19 Unnamed Creek............................................................................................................... 20 Discussion..................................................................................................................... ...21 Physical Chemical Parameters............................................................................................. 23 Gatling Branch.................................................................................................................23 Unnamed Creek............................................................................................................... 25 Discussion..................................................................................................................... ...27 Macroinvertebrates.................................................................................................................31 Gatling Branch.................................................................................................................31 Unnamed Creek............................................................................................................... 33 Discussion..................................................................................................................... ...35 4 CONCLUSIONS.................................................................................................................... 48 LIST OF REFERENCES...............................................................................................................51 BIOGRAPHICAL SKETCH.........................................................................................................53

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5 LIST OF FIGURES Figure page 2-1 Aerial map of Gatling Branch............................................................................................ 16 2-2 Aerial map of Unnamed Creek.......................................................................................... 17 2-3 Longitudinal profile of wate r depth at Gatling Branch. ..................................................... 18 2-4 Longitudinal profile of wa ter depth at Unnam ed Creek.................................................... 18 3-1 Longitudinal distribution of benthi c organic m atter at Gatling Branch............................. 37 3-2 Vertical distribution of benthic organic m atter at Gatling Branch.................................... 37 3-3 Longitudinal distributio n of benthic organic m atter at Unnamed Creek........................... 38 3-4 Vertical distribution of benthic organic m atter at Unnamed Creek...................................38 3-5 Longitudinal temperature profile for Gatling Branch. ....................................................... 39 3-6 Longitudinal dissolved oxygen profile for Gatling Branch............................................... 39 3-7 Longitudinal specific conductiv ity p rofile for Gatling Branch.......................................... 40 3-8 Longitudinal turbidity profile for Gatling Branch............................................................. 40 3-9 Longitudinal temperature profile for Unnamed Creek...................................................... 41 3-10 Longitudinal dissolved oxyge n profile for Unna med Creek..............................................41 3-11 Longitudinal specific conductiv ity profile for Unnam ed Creek........................................ 42 3-12 Longitudinal turbidity profile for Unnamed Creek............................................................ 42 3-13 Longitudinal invertebrate distribution for Gatling Branch................................................ 43 3-14 Longitudinal taxonomic dist ribution for Gatling Branch. ................................................. 43 3-15 Longitudinal distributio n of collector/gatherers at Gatling Branch. ..................................44 3-16 Longitudinal distribution of f ilter feeders at Gatling Branch. ........................................... 44 3-17 Longitudinal distri bution of predators at Gatling Branch. ................................................. 45 3-18 Longitudinal invertebrate distribution for Unna med Creek...............................................45 3-19 Longitudinal taxonomic dist ribution for Unna med Creek................................................. 46

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6 3-20 Longitudinal distribu tion of collector/gatherers at Unnam ed Creek................................. 46 3-21 Longitudinal distribution of f ilter feeders at Unnam ed Creek........................................... 47 3-22 Longitudinal distri bution of predators at Unnamed Creek. ...............................................47

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7 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 ROLE OF BEAVER IMPOUNDMEN TS IN THE STRUCTURE AND FUNCTION OF SOUTHERN GEORGIA STREAMS By Cody Rick McNeely December 2007 Chair: Thomas L. Crisman Major: Interdisciplinary Ecology The North American beaver ( Castor canadensis ) is one of the few extant mammals able to modify its surrounding landscape dramatical ly, often complicating its relationship with humans. However, the vast majority of research has been limited to north temperate regions, with almost no data regarding southern beaver po pulations. The focal point of this study was to understand the impact beaver impoundments on st ream systems of warm temperate regions. Two sites in Thomasville, Georgia (Gatli ng Branch and Unnamed Creek) were selected for this study based on location, morphol ogy, hydrology and active beaver populations. Sampling was conducted from November 2006 th rough April 2007, with April capturing the effects of extensive anthropogeni c construction activities. For each system, two 100-m stretches, upstream and downstream of the beaver pond, an d the pond proper were sampled. Measurements and/or samples included chemical / physical para meters (temperature, di ssolved oxygen, specific conductivity and total suspended solids), macroi nvertebrate communities and benthic organic matter storage. Statistical comparisons were made between compartments (upstream, downstream and pond), sampling periods and co mpartments relative to sampling period. During the pre-anthropogenic disturbance period, few parameters were longitudinally or temporally significant when compared between sampling compartment and sampling dates.

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8 However, effects resulting from beaver activ ity included changes in organic matter (OM) storage, dissolved oxygen (DO) and invertebra te abundance. Mean ups tream OM storage at Unnamed Creek was 6,600 g/m2, while storage within the pon d proper increased to 56,000 g/m2, almost an order of magnitude greater. Long itudinal DO at Gatling Br anch decreased from 7.6 mg/L upstream to 3.2 mg/L within impounded ar eas, and was attributed to increased OM loading. Responding to changes in DO, inverteb rate abundance at Gatling Branch decreased from 94,000 invertebrates/m2 upstream to 24,000 invertebrates/m2 within the backwater / pond. Longitudinal and temporal effects attributed to human construction activities adjacent to and immediately downstream of th e beaver pond at Gatling Branch included intense changes in water temperature, dissolved oxygen, suspended solids (turbidity) and in vertebrate abundance. During April, mean water temperature increased from 16oC in undisturbed sections of the stream to over 22oC within backwater / pond and downstream segments. During the same sampling period, mean DO decreased from 6.8 mg/L upstream to 3.9 mg/L within the pond, while mean turbidity increased from 4.6 NTU upstream to 14.7 NTU within and downstream of the beaver pond. In response to these chemical / physical ch anges, invertebrate abundance during April decreased from 162,000 individuals/m2 upstream to 28,000 individuals/m2 within the backwater / pond area. During this study, the effects of beaver impoundments were limited to invertebrate abundance, dissolved oxygen and OM storage. C onversely, anthropogenic dist urbances appear to have much greater effect on stream systems, w ith dramatic changes in temperature, dissolved oxygen, turbidity and invertebrate communitie s. Finally, the OM and carbon sequestration potential of these beaver impoundments wa s tremendous and may offer an overlooked component to counter global climate change.

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9 CHAPTER 1 INTRODUCTION The late n ineteenth and early twentieth cen turies witnessed the decline of the North American beaver from most waterways. Intense human pressure caused the demise of beaver and left many streams without natures wetland engineers for almost a century. Among the most heavily influenced beaver populations were thos e of the southeastern United States, with complete extirpation from some regions by th e early twentieth century. An aggressive conservation program has helped North Ameri can beaver populations recover. Extensive migration to southeastern waterways and es tablishment of healt hy populations are prime evidence of successful conservation efforts (Everett and Schaefer 2006). As semi-aquatic rodents native to North Amer ica and Europe, beaver are the only living members of the family Castoridae, which contai ns the single genus Castor. Beavers inhabit riparian zones of streams as well as the cha nnel. Families typically consist of around eight members with adults weighing up to 25 kg. The health and productivity of aquatic ecosystems depend in part on the influence of beaver. Func tioning as a keystone species by creating wetland habitat (McHale et al ., 2004), beaver are best known for construction of dams in streams and lodges in the ponds that form. Construction of lo dges is common in temperate regions, with bank dwelling more prevalent in warm southern region s. Beaver dams are created both as protection against predators and to provide food access du ring winter. During dam and lodge construction, beaver selectively remove riparian tress, cr eating gaps in canopy c over. This facilitates macrophyte colonization and prolifer ation in beaver ponds, resulting in altered nutrient cycling and aquatic food webs (Ray et al ., 2001). Nutrient sequestration is often considered the most valuab le function of a beaver pond. In addition, beaver ponds accumulate vast quantitie s of inorganic and organic matter. However,

PAGE 10

10 bacteria that produce cellulase can utilize cellulose in organi c matter for energy, creating the base of the microbial loop. Additional envi ronmental benefits derived from beaver impoundments include flood control, increased biodiversity and sequestra tion of organic carbon. Next to humans, no other extant animal does mo re to shape its landscape than beaver (Morgan 1986). This study was conducted because few data or studies on beaver exist for warm temperate regions. The focal point of this study wa s to understand how warm-temperate beaver impoundments in southern Georgia affect or ganic matter storage, water quality and macroinvertebrate communities. Investigation of organic matter included quantifying storage capacity and the potential role of beaver ponds in global carbon cycling. Change in water quality was assessed by temperature, specific conductivit y, dissolved oxygen and turbidity. The structure and function of macroinvertebrate assemblages in cluded identifying and a ssigning individuals to feeding guilds. Previous studi es investigating effects of beaver impoundments have been confined to regions that experience distinct seasonality. This study focused on beaver impoundments in a region experiencing long gr owing seasons and moderate winters.

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11 CHAPTER 2 MATERIALS AND METHODS Site Description Two sites in southern Georgia were select ed for this study, Gatling Branch and Unnamed Creek, based on geographical lo cation, morphology, hydrologic regi mes and accessibility. In addition, both sites had an active beaver population prior to the study that provided impoundment maintenance and presumed long-term sustainability. Gatling Branch Gatling Branch is a low gradient, second-or der stream (Strahler method) located in Thomas County, Georgia (30o 51 11.3 N, 83o 54 00.6 W). Headwaters of the two first order streams originate from seepage wetlands and flow south to their confluence north of Georgia state road 122 (Figure 2-1). USGS (U.S. Geological Survey) classified the flow regime of Gatling Branch (HUC 3110103) as intermittent, a nd it has mean bankfull width and mean water depth of 4.7 m and 9.8 cm, respectively. However, m ean water depth within the reach of stream influenced by beaver activity increased to 46.4 cm (Figure. 2-3). The substrate of the stream channel is predominantly sand with increasi ng organic content approaching the beaver pond from upstream. Upstream of the beaver pond, the ch annel is fully canopied, and the riparian zone is dominated by water oak (Quercus nigra ), sweetgum ( Liquidambar styraciflua ) and willow ( Salix caroliniana ). The canopy downstream is sparse and dominated by tulip poplar ( Liriodendron tulipifera ). The beaver pond has an approximate surface area of 80 m2 and is located 1.5 kilometers south of Georgia state ro ad 122. In addition, this site has an extensive backwater area, extending approximately 250 m upstream of the pond proper. Constructed primarily from wood and mud, the dam stood an impressive 1.5 m high. Water discharge occurred predominantly at the base of the da m with surface overflow only during high water.

PAGE 12

12 Unnamed Creek Unnamed Creek is a low gradient, second-or der stream (Strahler method) located in Thomasville, Georgia (30o 52 32.1 N, 83o 56 30.7 W). The principal headwater originates from a seepage wetland, while a secondary head water originates from channelized overland flow. Both stream channels flow north to a confluence south of US 84 bypass (Figure 2-2). USGS classified the flow regime of Unna med Creek (HUC 3120002) as intermittent. Mean bankfull width and mean water depth are 2.1 m and 28 cm, respectively. However, mean water depth within the reach of stream influenced by beaver activity increased to 55.5 cm (Figure. 2-4). The substrate of the stream channel is predom inantly sand and clay with increasing organic content approaching the beaver pond from upstream. The stream channel is fully canopied with a riparian zone dominated by water oak (Quercus nigra ), sweetgum ( Liquidambar styraciflua ), red maple (Acer rubrum ) and longleaf pine ( Pinus palustris ). The beaver pond has an approximate surface area of 2,900 m2 and is located 0.16 kilometers nort h of US 35. Constructed primarily from wood, the dam stands at a height of 0.65 m. Water discharge occurred predominantly as surface overflow with almost no discharge from the base of the dam. Field Methods For each stream two 100-m stretches, upstr eam and downstream of the beaver pond and the beaver pond proper were sampled. Sampling was conducted at Gatling Branch and Unnamed Creek three times from November 2006 through April 2007 (3 and 4 November 2006, 13 and 14 January 2007 and 6 and 7 April 2007). Benthi c organic matter was sampled once at the beginning of the study. Fieldwork required two da ys per site, 13 and 14 October 2006 for Gatling Branch and 20 and 21 October 2006 for Unnamed Creek.

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13 Organic Matter and Sedimentation Benthic organic m atter (BOM) samples were co llected using a clear PVC coring device 1m long and 3.8 cm in diameter. BOM cores were co llected at a transect interval of 0, 10, 25, 50, 75 and 100 m upstream and downstream of the beav er pond. Eleven additional cores at Gatling Branch and five at Unnamed Creek were collect ed within the pond and backwater areas at 25-m intervals. Three BOM cores were collected at each location; le ft bank, center channel / pond and right bank. Samples consisted of a ll material down to the sand or clay substrate. Collection began at the 100-m downstream transect and proceed ed upstream to avoid contamination between segments. Macroinvertebrate Communities Macroinv ertebrate samples were collected vi a the same PVC coring device used in BOM sampling. Macroinvertebrates from Unnamed Creek were collected at a transect interval of 0, 10, 50, and 100 m upstream and downstream of the beaver pond. Three additional samples were collected within the pond at randomly selected locations. Because of the extensive backwater area at Gatling Branch, macroinvertebrates were collected at a transect interval of 10, 50, and 100 m upstream of the beaver pond and 0, 10, 50 and 100 m downstream of the impoundment. Macroinvertebrates were not collected at the 0m upstream transect. However, two samples were collected from within the backwater area 10 m upstream from the pond (BWUSP) and 10 m downstream from the upstream 0-m transect (BWDSE). Three additional samples were collected within the pond at randomly se lected locations. Only one macroinvertebrate sample was collected at each transect and consisted of all ma terial to a depth of 15 cm. Samples were placed into one-liter plastic containers and preserved in situ with 70 % ethanol contai ning 0.2 mg/l of Rose Bengal stain. Collection began at the 100-m downstream transect and proceeded upstream to avoid sampling interference between segments.

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14 Physical Chemical Parameters Physical / chem ical paramete rs (temperature, dissolved oxyg en and specific conductivity) were measured in situ using a YSI 585 field probe. Total suspended solids (turbidity) was measured in the laboratory by analyzing a 25-ml water sample using a LaMotte 2020 Turbidimeter, and results were reported in neph elometric turbidity units (NTUs). Measurements from Unnamed Creek were taken at 0, 10, 50, and 100 m upstream and downstream of the beaver pond. Three additional measurements were taken w ithin the pond at randomly selected locations. Because of the extensive backwater area at Gatl ing Branch, measurements were taken at 10, 50, and 100 m upstream of the beaver pond and 0, 10, 50 and 100 m downstream of the impoundment. Physical / chemical parameters we re not taken at the 0-m upstream transect. However, two measurements were taken from w ithin the backwater area 10 m upstream from the pond (BWUSP) and 10 m downstream from the upstream 0-m transect (BWDSE). Three additional measurements were taken within the pond at randomly selected locations. Measurements and sample collection began at the 100-m downstream transect and proceeded upstream to avoid sampling interference between segments. Laboratory Methods Loss on Ignition (LOI) Analysis BOM cores were divid ed longitudinally into 10-cm segments and homogenized using a standard mortar and pistil One sub-sample of 5 cm3 was taken from each homogenized segment and dried at 60 C for 48 hrs. Upon removal, a dry wei ght was obtained using an analytical balance measuring to three decimals. Each samp le was then combusted in a muffle furnace at 550 C for 5 hrs. Samples were allowed to cool in a desiccator for 8 hrs and weighed again to obtain ash free dry weight.

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15 Macroinvertebrates Samples remained in collection bottles for a minimum of 48 hrs to ensure sufficient staining with Rose Bengal. To aid in sorting macroinvertebrate s, samples were washed through 500-m sieves to collect larger and more developed larva, and through 250-m sieves to collect smaller and earlier instar stages The collected macroinvertebrates were placed into 10-ml glass vials and labeled with the tran sect location. Identification wa s made to lowest practical taxonomic level to facilitate assignment of indivi duals to a functional fe eding group (Merritt and Cummings 1996). Using a dissectin g microscope, taxonomic identification was determined to genus for all specimens belonging to the class In secta. Individuals in the family Chironomidae were identified to genus after mounting h ead capsules on slides and using a compound microscope. Identification was to class and/or family for all other macroinvertebrates. Statistics For the purpose of statistical comparison, each system was divided into three treatments; upstream, downstream and backwater / pond. Using an ANOVA statistical model in SAS, parameters of organic matter, physical / chemical characterist ics and macroinvertebrates were compared among treatments and sampling dates. Three statistical comp arisons were made relative to treatment: upstream versus downstream, pond versus downstream and upstream versus pond.

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16 Figure 2-1. Aerial map of Gatling Branch.

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17 Figure 2-2. Aerial map of Unnamed Creek.

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18 0 25 50 75 100 125 150 175 050100150200250300350400450Distance (m)Water Depth (cm) November January April Figure 2-3. Longitudinal profile of water depth at Gatling Branch. 0 30 60 90 120 150 180 210 0255075100125150175200225250275 Distance (m)Water Depth (cm) November January April Figure 2-4. Longitudinal profile of water depth at Unnamed Creek

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19 CHAPTER 3 RESULTS AND DISCUSSION Benthic Organic Matter Gatling Branch The study area at Gatling Branch consiste d of 350 m of stream channel and three impoundments. The main impoundment (Pond 10) wa s the largest and most central. A second and slightly smaller impoundment was approxi mately 250 m upstream (BW225) of the beaver pond. The third and smallest impoundment was located 100 m downstream (DS100) of the beaver pond. Spatial differences in organic matter (O M) occurred longitudinally throughout the system, with storage greatest at stream / im poundment interface. Correspondingly, OM storage at the main impoundment / stream interface was 57,000 g/m2 (Pond 10), while storage at the stream interface for the two smaller impoundments was 59,000 (BW225), and 53,000 (DS100) g/m2 (Figure. 3-1). Mean OM storage was great est downstream of the beaver pond (38,000 g/m2), while storage for upstream and backwater / pond were 13,000 and 35,000 g/m2, respectively. Transects 0 and 10 m up stream (23,000 and 21,000 g/m2, respectively) heavily influenced mean upstream storage, presumably due to the abrupt decease in velocity and precipitation of OM. Using the 25, 50, 75 and 100-m transects as a baseline for normal stream condition, a much smaller upstream mean of 8,100 g/m2 was calculated. Using an ANOVA model in SAS, significant longitudinal effects on OM storage were observed between downstream versus upstream and pond versus upstream (p<0.03) and (p<0.02), respectively, with downstream and pond segments having significantly greater OM st orage compared to upstream. The pond was not significantly different from downstream.

PAGE 20

20 The vertical OM profiles for upstream, backwater / pond and downstream exhibited an indirect relationship with de pth, with the exception of the interface between stream and impoundments, which exhibited a direct relatio nship between OM and depth (Figure 3-2). Complex vertical stratification presented difficul ties in analyzing core segments. Thus, each core was divided vertically at the midpoint into larger upper and lower sections, and mean OM for each section was calculated. Mean OM storage for the upper and lower profile for upstream and downstream segments were 4,500 and 2,200 g/m2 and 6,900 and 6,000 g/m2, respectively. Mean backwater / pond storage was 7,000 and 6,100 g/m2, respectively. However, mean OM storage for the upper and lower profile at upstream 0 m was 5,600 and 8,000 g/m2, respectively. Storage profiles for both minor impoundments were 5,300 and 9,300 g/m2 (BW225) and 9,200 and 11,000 g/m2 (DS100), respectively. The main impound ment (Pond10) had an upper and lower profile of 2,600 and 8,900 g/m2, respectively. However, no signifi cant vertical difference in OM was observed for any sampling compartment. Unnamed Creek Spatial differences in organic matter (OM) storage occurred longitudinally throughout Unnamed Creek. Storage was greatest at the upstream / pond interface and directly behind the beaver dam, averaging 93,000 and 71,000 g/m2, respectively (Figure 3-3) Mean OM storage was greatest within the pond proper (56,000 g/m2), while upstream and downstream storage were 37,000 and 18,000 g/m2, respectively. Using an ANOVA model, significant long itudinal effects on OM storage were observed between pond ve rsus upstream and pond versus downstream (p<0.001), with the pond having significantly gr eater OM storage compared to upstream and downstream segments. No statistical significance in OM storage was observed between upstream and downstream segments. Transects 0 and 10 m upstream (93,000 and 92,000 g/m2, respectively) heavily influenced mean upstream st orage, presumably due to the abrupt decease in

PAGE 21

21 velocity and precipitation of OM. In addition, do wnstream transects 75 and 100 m reside within a marsh. Calculating baseline stream conditions ex cluding these transects yielded a much smaller upstream and downstream mean of 6,600 and 12,000 g/m2, respectively. Using the adjusted upstream mean, OM storage per area within the pond is almost an order of magnitude greater than baseline stream co nditions (6,600 and 56,000 g/m2, respectively). Vertical OM profiles for upstream and downstream segments at Unnamed Creek exhibited an indirect relationship with depth. The interfaces between stream / pond and directly behind the dam were the exception with vertical profiles exhibiting a dir ect relationship between OM and depth (Figure 3-4). Unnamed Creek exhibite d the same complex vertical stratification as Gatling Branch. Thus, each core was similarly divi ded vertically at the midpoint into larger upper and lower sections and mean OM calcula ted for each. Mean upper and lower profiles for upstream and downstream segments were 10,000 and 8,000 g/m2 and 14,000 and 12,000 g/m2, respectively. However, mean OM storage for the upper and lower profile at upstream 0 m was 9,000 and 14,000 g/m2, respectively. The OM profile with pond proper was 11,000 and 13,000 g/m2, respectively. However, no significant verti cal difference in OM was observed for any sampling compartment. Discussion Investigation of sediment depth and accumula tion rates within beaver ponds at Glacier National Park suggested that se diment volume was strongly corre lated with pond area, with rate of sedimentation greater in ponds than upstrea m (Butler and Malanson 1995). The longitudinal OM profile at Unnamed Creek further supports th ese finding, with greatly increased OM storage within the pond proper compared to upstream and downstream areas. In contrast, the longitudinal profile at Gatling Branch was unique in that the downstream segment had the greatest storage per area basis. This profile is presumed to be the result of a multi-dam system. The relatively close

PAGE 22

22 longitudinal proximity of impoundments presumably prevented OM from re turning to baseline conditions, resulting in increasing OM with progression downstream. Complex vertical profiles were observe d for Gatling Branch and Unnamed Creek. Vertical stratification was presumably the resu lt of precipitation events that introduce large quantities of allocthonous sand. When the rain even t subsides and/or the stream encounters an impoundment, stream velocity decreases and sand accumulates. Conversely, during periods of low flow, allocthonous OM will accumulate. Thus, it is suggested that oscill ation in stage is the cause for vertical stratification. The vertical profile for upstrea m and downstream segments at Gatling Branch and Unnamed Creek exhibited an indirect relationship between OM and depth, while a direct relationship existe d at stream / impoundment inte rfaces. This direct relationship between OM and depth is presumably caused by th e predominantly sand substrate that allows for vertical movement of organic matter and a confin ing layer of clay that defines the extent of downward movement. Reduced velocity and increas ed retention time at stream / impoundment interface allows biota to process coarse OM, causing a reduction in particle size (Kaplan et al., 1980, Wetzel 1983). The fine particulate organic matter (FPOM) presumably moves through the sand substrate, creating a vertic al OM profile inverted from upstream and downstream segments. Sequestered organic matter in aquatic system s represents a significant component of the global carbon pool. Photosynthetic and respiratory processes within these systems are important regulators of inorganic carbon (i.e. CO2 and CH4) in the atmosphere (Amundson 2001). The storage potential of car bon compounds in wetlands, and sp ecifically beaver ponds, can offer significant contributions to gl obal carbon cycling. Prior to ne ar-extirpation, there was an estimated 12.5 million beaver ponds in North Amer ica trapping hundreds of billions cubic meters of organic sediment in streams (Butler 2006). Th e impoundments at Gatling Branch influenced at

PAGE 23

23 least 350 m of stream and sequestered more th an 42,800 kg of organic matter. In addition, the single impoundment at Unnamed Cr eek influenced at least 175 m of stream, sequestering more than 124,000 kg of organic matter. Beaver activity at Gatling Br anch and Unnamed Creek had a tremendous influence on the longitudinal and vertical distribution of OM, demonstrating the storage potential of thes e systems. Serving as large OM (i.e. carbon) sinks, beaver ponds offer an overlooked component to the complicated problem of global climate change. Physical Chemical Parameters Spatial differences in physical and chem ical parameters occurred both longitudinally and temporally in Gatling Branch and Unnamed Creek. November 2006 and January 2007 data for Gatling Branch were collected prior to anthropog enic disturbance, while April recorded the effects of extensive construction activities adj acent to pond and downstream transects that began in mid January 2007. For statistical analysis, each system was divided into three compartments: upstream, downstream and backwater / pond. Gatling Branch Water temperature in Gatling Branch ranged longitudinally between 14.3 and 14.9 oC during November, while January and April ranged between 9.1 and 10.9 oC and 16.9 and 24.9 oC, respectively (Figure. 3-5). Mean water temperature was 14.7 oC during November, while January dropped to 10.1 oC. Water temperature was greatest during April (19.4 oC). Mean longitudinal temperature was great est within backwater / pond (15.3 oC), with upstream and downstream segments averaging 14.1 and 14.7 oC, respectively. Using an ANOVA model in SAS to analyze and compare longitudinal temper ature between sampling compartments yielded no statistical significance for any date. However, statistical significance was observed between longitudinal temperature and sampling period when comparing downstream and pond segments between November and April and January and Ap ril (p<0.005) and (p<0. 001), respectively, with

PAGE 24

24 downstream and pond temperature si gnificantly greater during April. No temporal significance was observed between November and January. Dissolved oxygen (DO) ranged longit udinally between 2.3 and 7.3 mg/L during November, with January and April ranging between 8.3 and 9.1 mg/L and 3.6 and 7.0 mg/L, respectively (Figure. 3-6). Mean DO during November was lowest (4.5 mg/L) and January highest (8.8 mg/L). Dissolved oxygen was inte rmediate during April at 5.4 mg/L. Mean longitudinal DO was greatest upstream and lowest within backwater / pond at 7.6 and 5.2 mg/L, respectively. Dissolved oxygen was intermedia te downstream with an average of 5.8 mg/L. Using an ANOVA model to analyze longitudina l DO between sampling compartments yielded statistical significance for downstream versus upstream and pond versus upstream segments (p<0.001), with the upstream having significantl y greater DO than pond and downstream. No statistical significance in DO was observed in p ond versus downstream. In addition, statistical significance was observed between longitudinal DO and sampling period when comparing downstream and pond segments between November and January and April and January (p<0.001), with downstream and pond DO significan tly greater during January. Comparisons between November and April sampling peri ods yielded no temporal significance. Specific conductivity ranged longitudina lly between 45 and 58 m during November. January and April ranged betw een 40 and 43 m and 63 and 80 m, respectively (Figure. 3-7). Mean conductivity during Nove mber was intermediate at 54 m. During January, mean conductivity was lowest (42 m) and during Ap ril highest (70 m). Mean longitudinal conductivity was the same for backwater / pond and downstream segments at 57 m, while upstream averaged 52 m. Using SAS to analy ze and evaluate conductivity between sampling compartments yielded statistical significance for downstream versus upstream and pond versus

PAGE 25

25 upstream segments, (p<0.03) and (p<0.004), respectively, with pond and downstream segments having higher conductivity. No st atistical significan ce in conductivity was observed in pond versus downstream. However, statistical si gnificance was observed between longitudinal conductivity and sampling period when comparing downstream segments between November and April and January and April (p<0.001), with downstream conductivity greater during April. No significant temporal cha nges were observed between November and January sampling periods. Turbidity at Gatling Branch ranged long itudinally between 5.1 and 9.0 NTU during November, while January and April ranged between 5.4 and 7.0 NTU and 4.4 and 16.2 NTU, respectively (Figure. 3-8). Mean turbidity levels during November and January were similar, 6.0 and 6.5 NTU, respectively, and greatest during Ap ril at 10.8 NTU. Mean longitudinal turbidity was greatest downstream and lowest upstream at 8.9 and 5.8 NTU, respectively. Turbidity was intermediate within backwa ter / pond (8.6 NTU). Using an ANOVA model to evaluate longitudinal turbidity between sampling compar tments yielded statistical significance for downstream versus upstream and pond versus upstream segments (p<0.001), with pond and downstream segments having significantly greate r turbidity. No statistical significance in turbidity was observed in pond versus downstream. However, statistical significance was observed between turbidity and sampling pe riod when comparing downstream and pond segments between November and April and January and April (p<0.001), with pond and downstream turbidity significantly higher during April. No temporal si gnificance was observed between November and January. Unnamed Creek Water temperature in Unnamed Creek ranged longitudinally between 10.4 and 12.9 oC during November. January and April ranged between 9.2 and 11.4 oC and 11.4 and 15.7 oC,

PAGE 26

26 respectively (Figure. 3-9). Mean water te mperature was greate st during April (13.9 oC), with November at 11.1 oC and January at 10.4 oC. Mean longitudinal temperature upstream and within the pond proper were the same (11.8 oC). Mean temperature was greatest downstream (12.2 oC). Using an ANOVA model to compare long itudinal temperature between sampling compartments yielded no statistical significance fo r any date. However, st atistical significance was noted between longitudinal temperature an d sampling period when comparing downstream and pond segments between January and April and November and April (p<0.001), with downstream and pond temperature si gnificantly higher during April. Dissolved oxygen (DO) ranged longit udinally between 1.5 and 3.8 mg/L during November, with January and April ranging between 5.4 and 7.9 mg/L and 1.1 and 6.5 mg/L, respectively (Figure. 3-10). Mean DO during April was lowest (2.4 mg/L) and highest during January (6.8 mg/L). November was intermed iate at 2.5 mg/L. Mean longitudinal DO was greatest upstream and lowest within the pond prop er at 4.7 and 3.6 mg/L, respectively. Dissolved oxygen was intermediate downstream (4.4 mg/L ). Using an ANOVA model to compare and evaluate longitudinal DO between sampling compar tments yielded no statis tical significance for any date. However, statistical significance was obse rved between longitudinal DO and sampling period when comparing the beaver pond between January and April (p<0.001), with pond DO significantly greater during the former. Conductivity ranged longitudinally between 33 and 50 m during November, while January and April ranged betw een 45 and 52 m and 58 and 70 m, respectively (Figure. 3-11). During November, mean conductivity was lowest (38 m) and highest during April (65 m). Conductivity during January was intermediate at 48 m. Mean longitudinal conductivity upstream and downstream were both 54 m, while the pond proper averaged 48 m. Using SAS

PAGE 27

27 to compare and analyze longitudinal conductivity between sampling compartments and sampling periods yielded no sta tistical significance. Turbidity at Unnamed Creek ranged long itudinally between 2.3 and 4.1 NTU during November, with January and April ranging between 3.1 and 5.3 NTU and 5.0 and 10.1 NTU, respectively (Figure. 3-12). Mean turbidity leve ls during November and January were similar, 3.0 and 3.9 NTU, respectively. Turbidity was greatest during Apr il at 6.1 NTU. Mean longitudinal turbidity was greates t downstream and lowest within the pond proper at 7.0 and 3.8 NTU, respectively. Turbidity was intermediate upstream, averaging 4.4 NTU. Using an ANOVA model to evaluate longitudinal turbidity between sampling compartments yielded statistical significance for downstream versus pond segments (p<0.002), with downstream having greater turbidity. In addition, statisti cal significance was observed be tween turbidity and sampling period when comparing downstream segments be tween January and April (p<0.001), with the latter having significantly increased turbidity downstream. Discussion According to research by Maxted et al (2005), water temperatures in beaver ponds and downstream fluctuate seasonally, with longitudinal temperatures be ing stable during winter and elevated during summer. Increased water temperat ure was attributed to larger surface area of ponds and increased adsorption of solar radiation during summer. L ongitudinal variation in water temperature at Unnamed Creek followed this pa ttern. Upstream and downstream riparian zones created a nearly closed canopy and provided l ongitudinal stability in temperature during November and January, while the large su rface area of the beaver pond and limited canopy protection from the riparian zone allowed for increased sunlight penetration and elevated temperatures during April.

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28 Similar to Unnamed Creek, water temperat ure during November at Gatling Branch experienced almost no longitudinal variation, likely the result of a well-vegetated riparian zone and the relatively small surface area of impoundments. However, during January, water temperature at Gatlin Branch decreased within pond and dow nstream segments. This very different pattern was attribut ed to the beaver population abandoning the impoundment, and the ability of cooler bottom water to mix and discharge through s ubsequently degraded sections of the dam. During April, pond and downstream te mperature at Gatling Branch paralleled the finding of Maxted et al (2005), with temperature being greate st at the dam and decreasing with downstream progression. However, increased temperat ures were not the resu lt of beaver activity; rather, the extensive removal of riparian vegetation during construc tion and resulting increase of solar radiation. Temporal differences in mean water temperature at Gatling Branch and Unnamed Creek between November, January and April are presumed to be the result of seasonal variation, caused by changes in ambient air te mperature and length of daylight. Research conducted in New Zealand suggest ed that dissolved oxygen (DO) in beaver ponds and downstream fluctuates temporally, wi th reduced DO during su mmer. Decreases in DO were attributed to increased organic loading and increased decomposition within the beaver pond (Maxted et al ., 2005). During November and April, l ongitudinal DO decreased dramatically within the backwater / pond area at Gatling Br anch. Similarly, DO levels at Unnamed Creek greatly decreased within the pond proper during January and Apr il. As suggested by Maxted et al. (2005), such longitudinal changes in DO at Gatling Branch and Unnamed Creek are likely the result of increased metabolic processes and ra pid consumption of DO within impounded areas. However, removal of riparian vegetation, comb ined with poor performa nce of installed silt barriers during construction, presumably caused the decrease in DO observed during April at

PAGE 29

29 Gatling Branch. Analogous to previous months, increased lateral input of fine particulate organic matter (FPOM) from construction resulted in in creased decomposition and biological demand for oxygen. The January sampling period at Gatling Branch yielded very different results, with almost no longitudinal change in dissolved oxygen. Du ring this period, water flowed unimpeded through degraded sections of the beaver dam. This continuous flow prevented depletion of DO within the backwater / pond area, resulting in litt le longitudinal variati on. Temporal differences in mean DO at Gatling Branch and Unnamed Cr eek between November, January and April are assumed to be the result of seasonal variati on in ambient / water temperature and resulting changes in saturation of oxygen into water. The conductive properties of aquatic envi ronments are principally controlled by watershed geology, soil composition and vegeta tion. Thus, anion and cation strength (i.e. specific conductivity) is the result of weathered ro ck, biogeochemical interactions within the soil matrix and the storage potential of adjacent te rrestrial landscapes. L ongitudinal stability of specific conductivity at Unnamed Creek for all sampling compartments and sampling periods is presumed the result of stability within the watersheds geology, soils, vegetation and storage capacity. Contrary to Unnamed Creek, conductivity dur ing November and April at Gatling Branch increased within the backwater / pond and dow nstream segments. The observed increase in conductivity during November is presumed to be the result of warmer water temperatures, increased organic decomposition and production of ions within impounded areas. However, during April, ion storage capacity of the adjacen t riparian zone was altered with the near complete removal of riparian vegetation duri ng construction. When combined with the poor

PAGE 30

30 performance of silt barriers, the result was increa sed lateral inputs of ions causing the increase in conductivity observed between transects BWUSP and DS10. In contrast, January had almost no longitudinal variation in conductivity, presumably resulting from the continual flow of water through de graded sections of the main dam, which prevented accumulation of ions in impounded areas. Temporal differences in conductivity at Gatling Branch and Unnamed Creek between Nove mber, January and April are presumed to reflect seasonal changes in temperature, rate of decomposition and ion production within the watershed. Hillman et al. (2004) investigated susp ended solids within beaver ponds and found that concentrations of fine partic ulate organic and inorganic ma tter were greatest near the impoundment outlet and decreased progressively dow nstream. In contrast, longitudinal turbidity during November and January sampling periods at Gating Branch and Unnamed Creek was relatively stable, and presumed the result of an extensive riparian zone that provided bank stabilization and reduced lateral input of allocthonous materi al. However, during November, small increases in turbidity were observed at upstream transect BWDSE and downstream transect DS0, resulting from interactions betwee n moving waters of the upstream and static water of the backwater / pond, and the interface betw een the main beaver dam and downstream. As found by Hillman et al. (2004), turbidity during April at Gatl ing Branch increased dramatically within and downstream of the impoundment. Howe ver, increases in turbidity are presumed to result from construction activities that facilitated increased riparian inputs of particulate material that caused the observed increase in turbid ity between transect BWUSP and DS100, and not from beaver activity. In contrast, increased turbidity observed downstream during April at Unnamed Creek was presumed the result of low fl ow conditions (less than 2 cm in depth) and

PAGE 31

31 resulting difficultly in collecting a non-contam inated sampling. Thus, transects DS0, DS10 and DS50 were omitted from the April dataset at Unnamed Creek. Macroinvertebrates Spatial differences in m acroinvertebrate communities occurred both longitudinally and temporally in Gatling Branch and Unnamed Creek. November 2006 and January 2007 sampling for Gatling Branch were prior to anthropogeni c disturbance, while April 2007 recorded the effects of extensive construction activities adj acent to pond and downstream transects that began in mid January 2007. Analyses included change s in abundance, taxonomic richness and feeding guilds, as well as trends within individual inve rtebrate groups. For statistical analysis, each system was divided into three compartments: upstream, downstream and backwater / pond. Gatling Branch Mean abundance was greates t during April and lowest during January at 68,500 and 25,500 invertebrates/m2, respectively. November was inte rmediate at 54,000 invertebrates/m2 (Figure. 3-13). Mean longitudinal abundance was greatest upstream (94,000 invertebrates/m2), while downstream and backwater / pond segmen ts averaged 30,000 and 23,600 invertebrates/m2, respectively. Using an ANOVA model to analyz e and compare longitudinal abundance between sampling compartments yielded statistical significance for pond versus upstream and downstream versus upstream segments (p<0.001 ), with upstream invertebrate abundance significantly greater than pond and downstream. No signi ficance was observed between pond and downstream segments. However, statistica l significance was observe d between longitudinal abundance and sampling period when comparing upstream segments between November and January (p<0.04), November and April (p<0.00 2) and January and April (p<0.001), with upstream abundance during April significantly greater than November and January (162,000,

PAGE 32

32 85,500 and 35,000 invertebrates/m2, respectively). No significance was observed between pond and downstream segments for any sampling period. Taxonomic richness was greatest during April, with an average of 4.2 families throughout the system. Richness during November and January displayed cl ose similarities, averaging 3.8 and 3.5 families, respectively (Figure. 3-14). Mean richness was greatest upstream and lowest downstream, 4.5 and 3.5 families, respectively. Ric hness was intermediate within backwater / pond at 3.8 invertebrate families. No statistical significances between longitudinal taxa richness and sampling compartment were observed. Howe ver, statistical significance was observed between richness and sampling period, when comp aring upstream segments between January and April (p<0.002), with upstream richness significantly greater dur ing April compared to January (5.8 and 3 taxa, respectively). There were no signif icant differences in taxa richness for any other sampling compartment or period. Three main feeding guilds were present at Gatling Branch: collector/gatherers, filterer feeders and predators. Although longitudinal variation was observed, collector/gatherers dominated all sampling compartments and date s, accounting for 85 to 97 percent of total individuals. Mean abundances of both collector/gatherers and filte r feeders were greatest during April, with 63,500 and 4,300 individuals/m2, respectively. January had the lowest abundance of collector/gatherers and filterers with 23,000 and 600 individuals/m2, respectively. November was intermediate at 51,000 and 1,500 individuals/m2, respectively. Predators followed a different trend with November and January having the greatest abundance, averaging 1,500 and 1,000 individuals/m2, respectively. April had the lowest abundance at 600 individuals/m2. Mean upstream abundance of collector/g atherers was greatest (88,000 individuals/m2), while downstream and backwater / pond se gments were similar with 27,000 and 22,000

PAGE 33

33 individuals/m2, respectively (Figure. 3-15). Longitudinal abundance of filter f eeders was greatest upstream and lowest within the pond / backwater with 4,000 and 950 individuals/m2, respectively. Abundance of filter feeders wa s intermediate downstream, averaging 1,500 individuals/m2 (Figure. 3-16). Upstream and downstream predator abundance averaged of 2,000 and 660 individuals/cm2, respectively, while average abundan ce was lowest within the backwater / pond segments at 370 individuals/m2 (Figure. 3-17). However, using an ANOVA model for statistical analysis, no si gnificance between functional feeding groups and sampling compartment or sampling date was observed. Unnamed Creek Mean invertebrate abundance was greates t during November with 23,000 individuals/m2, while mean abundance for both January and April was 21,000 invertebrates/m2 (Figure. 3-18). Mean longitudinal abundance was greatest ups tream and lowest downstream with 27,900 and 14,800 invertebrates/m2, respectively. The pond proper was intermediate with 22,400 invertebrates/m2. Using an ANOVA model to analyze and compare longitudinal abundance between sampling compartments yielded no stat istical significance. However, statistical significance was observed betw een longitudinal abundance and sampling period, when comparing upstream segments between November and January and April and January (p<0.04) and (p<0.001), respectively, with upstream a bundance during November and April significantly greater than January (29, 500, 42,000 and 11,900 invertebrates/m2, respectively). No temporal significance was observed between pond and downstream segments for any sampling period. Taxonomic richness was greatest during April, averaging 5.5 families throughout the system, while November and January were simila r at 3.9 and 4.1 families, respectively (Figure. 3-19). Mean taxa richness was greatest upstream, averaging 4.8 families per transect. Downstream and pond richness were the same, with an average of 4.3 invertebrate families per

PAGE 34

34 transect. No statistical signi ficance between longitudinal ta xonomic richness and sampling compartment was observed. However, statistica l significance was obser ved between taxonomic richness and sampling period. Comparing upstream segments between January and April yielded significance of (p<0.002), with mean upstream richness greater during April compared to January (7.3 and 3 taxa, respectively). Statisti cal significance in richne ss was not observed for any other sampling compartment or period. Three major feeding guilds were present at Unnamed Creek: collect or/gatherers, filterer feeders and predators. In contra st to Gatling Branch, collector/g atherers at Unnamed Creek did not dominate all sampling compartments and date s, instead filter feeder s accounted for 12 to 44 percent of total invertebrates. Mean abundance of collector/g atherers was greatest during November, with an average of 20,000 individuals/m2. Abundance during January and April were nearly identical, averaging 14,000 and 12,500 individuals/m2, respectively. Mean abundances of filter feeders was greatest during April a nd lowest during November, with 7,000 and 2,400 individuals/m2, respectively. Abundance of filter feeders was intermediate during January with 5,100 individuals/m2. Mean abundance of predators during January and April were similar, with 1,200 and 1,350 individuals/m2, respectively. Predator abundan ce was lowest during November at 640 individuals/m2. Mean upstream and pond abundances of colle ctor/gatherers were similar, averaging 20,000 and 18,500 individuals/m2, respectively. Longitudinal abunda nce of collector/gatherers was lowest downstream with 9,100 individuals/m2 (Figure 3-20). Filter feeder abundance was greatest upstream and lowest within th e pond, averaging 6,400 and 3,200 individuals/m2, respectively. Downstream abundance was intermediate at 4,500 individuals/m2 (Figure. 3-21). Mean predator abundance was lowest with in the pond proper at 670 individuals/m2, while

PAGE 35

35 upstream and downstream averag ed 1,300 and 1,100 individuals/m2, respectively (Figure. 3-22). Using an ANOVA model for statistical analysis no significance between functional feeding groups and sampling compartment or sampling date was observed. Discussion The relative abundance of macroinvertebrate s was significantly elevated in Ontario beaver ponds, and was attributed to accumulati on of coarse woody debris and trapped sediment within impounded areas (France 1997). However, research finding by Collen and Gibson (2001), suggested that invert ebrate abundance within beaver ponds decreased per unit area, when compared to the upstream reach. Similarly, re lative abundance of macr oinvertebrates within impounded areas at Gatling Branch was dramatically lower for all sampling periods, while no significant longitudinal change in abundance wa s observed in Unnamed Creek. Upstream and backwater / pond abundance at Gatling Branch averaged 94,000 and 23,600 individuals/m2, respectively. Longitudinal change s in relative abundance were attr ibuted to decreased DO within impounded areas. Upstream DO at Gatling Branch averaged 7.6 mg/L, while decreasing to 3.2 mg/L within the beaver pond. France (1997) suggested increased taxonomi c richness within beaver ponds that was attributed to accumulation of organic debris and trapped sediment within impounded areas, promoting increased habitat heterogeneity. No significant longitudinal changes in taxonomic richness at Gatling Branch or Unnamed Creek were observe d during this study. However, temporal significance was noticed between Ja nuary and April for both Gatling Branch and Unnamed Creek. Greater upstream richness during April was attri buted to longitudinal changes in dissolved oxygen and the ability to capture larger / more develope d instar stages of invertebrates.

PAGE 36

36 Margolis et al. (2001) studied the effects of beav er impoundments on macroinvertebrate communities of low order Appalachian stream s and found that pond and downstream taxonomic composition and functional feedi ng groups were strongly correlat ed with water temperature, chemistry and dissolved oxygen. Neither Gatl ing Branch nor Unnamed Creek exhibited significant longitudinal change in taxa com position or dominate feeding groups, even though longitudinal and temporal changes in temper ature and DO were observed. However, analogous to relative abundance, significant reduction in abundance within and downstream of the beaver pond was observed for each feeding group (colle ctor/gatherers, filtere rs and predators). Correspondingly, longitudinal changes in the abundance of collector/g atherers and filterers were attributed to decreased DO within impounded areas. However, longitudinal change in predator abundance was attributed to the in ability for the dominant genus Probezzia spp. (lotic) to inhabit the deeper waters of the impounde d areas (lentic), presumably cau sing the dramatic reduction of predators within the beaver ponds (Merritt and Cummings 1996).

PAGE 37

37 0 10000 20000 30000 40000 50000 60000 70000US 100 US 75 US 50 US 25 US 10 US 0 BW 225 BW 200 BW 175 BW 150 BW 125 BW 100 BW 75 BW 50 BW 25 Pond 10 Pond 0 DS 0 DS 10 DS 25 DS 50 DS 75 DS 100TransectOrganic Matter (g/m2) Figure 3-1. Longitudinal distribution of benthic organic matter at Gatling Branch. 0 10 20 30 40 50 60 70 80 90US 100 US 75 US 50 US 25 US 10 US 0 BW 225 BW 200 BW 175 BW 150 BW 125 BW 100 BW 75 BW 50 BW 25 Pon 10 Pond 0 DS 0 DS 10 DS 25 DS 50 DS 75 DS 100TransectCore Depth (cm) 0 5000 5000 7500 7500 10000 10000 12500 12500 15000 LegendUnits: g/m2 Figure 3-2. Vertical distribution of be nthic organic matter at Gatling Branch.

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38 0 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000US 100 US 75 US 50 US 25 US 10 US 0 Pond 75 Pond 50 Pond 25 Pond 10 Pond 0 DS 0 DS 10 DS 25 DS 50 DS 75 DS 100TransectOrganic Matter (g/m2) Figure 3-3. Longitudinal dist ribution of benthic organic matter at Unnamed Creek. 0 10 20 30 40 50 60 70 80 90US 100 US 75 US 50 US 25 US 10 US 0 Pond 75 Pond 50 Pond 25 Pond 10 Pond 0 DS 0 DS 10 DS 25 DS 50 DS 75 DS 100TransectCore Depth (cm) 2500 7500 7500 10000 10000 12500 12500 15000 15000 17500 LegendUnits: g/m2 Figure 3-4. Vertical distribution of be nthic organic matter at Unnamed Creek.

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39 8 11 14 17 20 23 26US 100 US 50 US 10 BW DSE BW USP Pond 1 Pond 2 Pond 3 DS 0 DS 10 DS 50 DS 100TransectTemperature (Co) Nov-06 Jan-07 Apr-07 Figure 3-5. Longitudinal temperat ure profile for Gatling Branch. 2 4 6 8 10US 100 US 50 US 10 BW DSE BW USP Pond 1 Pond 2 Pond 3 DS 0 DS 10 DS 50 DS 100TransectsDissolved Oxygen (mg/L ) Nov-06 Jan-07 Apr-07 Figure 3-6. Longitudinal dissolved oxygen profile for Gatling Branch.

PAGE 40

40 25 35 45 55 65 75 85US 100 US 50 US 10 BW DSE BW USP Pond 1 Pond 2 Pond 3 DS 0 DS 10 DS 50 DS 100TransectConductivity (um) Nov-06 Jan-07 Apr-07 Figure 3-7. Longitudinal specific co nductivity profile for Gatling Branch. 3 6 9 12 15 18US 100 US 50 US 10 BW DSE BW USP Pond 1 Pond 2 Pond 3 DS 0 DS 10 DS 50 DS 100TransectTurbidity (NTU ) Nov-06 Jan-07 Apr-07 Figure 3-8. Longitudinal turbidit y profile for Gatling Branch.

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41 6 8 10 12 14 16 18US 100 US 50 US 10 US 0 Pond 1 Pond 2 Pond 3 DS 0 DS 10 DS 50 DS 100TransectTemperature (Co) Nov-06 Jan-07 Apr-07 Figure 3-9. Longitudinal temperat ure profile for Unnamed Creek. 0 2 4 6 8 10US 100 US 50 US 10 US 0 Pond 1 Pond 2 Pond 3 DS 0 DS 10 DS 50 DS 100TransectDissolved Oxygen (mg/L ) Nov-06 Jan-07 Apr-07 Figure 3-10. Longitudinal dissolved oxygen profile for Unnamed Creek.

PAGE 42

42 20 30 40 50 60 70 80US 100 US 50 US 10 US 0 Pond 1 Pond 2 Pond 3 DS 0 DS 10 DS 50 DS 100TransectConductivity (um) Nov-06 Jan-07 Apr-07 Figure 3-11. Longitudinal specific conductivity profile for Unnamed Creek. 0 2 4 6 8 10 12US 100 US 50 US 10 US 0 Pond 1 Pond 2 Pond 3 DS 0 DS 10 DS 50 DS 100TransectTurbidity (NTU ) Nov-06 Jan-07 Apr-07 Figure 3-12. Longitudinal turbid ity profile for Unnamed Creek.

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43 0 50000 100000 150000 200000 250000US 100 US 50 US 10 BW DSE BW USP Pond 1 Pond 2 Pond 3 DS 0 DS 10 DS 50 DS 100TransectInvertebrates (number/m2) Nov-06 Jan-07 Apr-07 Figure 3-13. Longitudinal invertebrate distribution for Gatling Branch. 0 2 4 6 8US 100 US 50 US 10 BW DSE BW USP Pond 1 Pond 2 Pond 3 DS 0 DS 10 DS 50 DS 100TransectTaxonomic Richness Nov-06 Jan-07 Apr-07 Figure 3-14. Longitudinal taxonomic distribution for Gatling Branch.

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44 0 40000 80000 120000 160000 200000US 100 US 50 US 10 BW DSE BW USP Pond 1 Pond 2 Pond 3 DS 0 DS 10 DS 50 DS 100TransectInvertebrates (number/m2) November January April Figure 3-15. Longitudinal distribution of collector/gatherers at Gatling Branch. 0 2000 4000 6000 8000 10000 12000 14000US 100 US 50 US 10 BW DSE BW USP Pond 1 Pond 2 Pond 3 DS 0 DS 10 DS 50 DS 100TransectInvertebrates (number/m2) November January April Figure 3-16. Longitudinal distribution of filter feeders at Gatling Branch.

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45 0 1000 2000 3000 4000 5000 6000 7000 8000US 100 US 50 US 10 BW DSE BW USP Pond 1 Pond 2 Pond 3 DS 0 DS 10 DS 50 DS 100TransectInvertebrates (number/m2) Series1 Series2 Series3 Figure 3-17. Longitudinal distributio n of predators at Gatling Branch. 0 10000 20000 30000 40000 50000 60000 70000US 100 US 50 US 10 US 0 Pond 1 Pond 2 Pond 3 DS 0 DS 10 DS 50 DS 100TransectInvertebrates (number/m2) Nov-06 Jan-07 Apr-07 Figure 3-18. Longitudinal invertebra te distribution for Unnamed Creek.

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46 0 2 4 6 8 10US 100 US 50 US 10 US 0 Pond 1 Pond 2 Pond 3 DS 0 DS 10 DS 50 DS 100TransectTaxonomic Richness Nov-06 Jan-07 Apr-07 Figure 3-19. Longitudinal taxonomic distribution for Unnamed Creek. 0 10000 20000 30000 40000 50000 60000 70000US 100 US 50 US 10 US 0 Pond 1 Pond 2 Pond 3 DS 0 DS 10 DS 50 DS 100TransectInvertebrates (number/m2) November January April Figure 3-20. Longitudinal distribution of collector/gatherers at Unnamed Creek.

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47 0 7500 15000 22500 30000 37500 45000US 100 US 50 US 10 US 0 Pond 1 Pond 2 Pond 3 DS 0 DS 10 DS 50 DS 100TransectInvertevrates (number/m2) November January April Figure 3-21. Longitudinal distribution of filter feeders at Unnamed Creek. 0 2000 4000 6000 8000 10000 12000US 100 US 50 US 10 US 0 Pond 1 Pond 2 Pond 3 DS 0 DS 10 DS 50 DS 100TransectInvertebrates (number/m2) November January April Figure 3-22. Longitudinal distributio n of predators at Unnamed Creek.

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48 CHAPTER 4 CONCLUSIONS The objective of this study was to understand the impact of beaver (Castor canadensis) impoundments on the structure and function of str eams in warm temperate, southern Georgia. The ability of beaver to modify its surrounding landscape considerably ha s created a complicated relationship with humans, often leading to wildlife management plans that prescribe their complete eradication. Two sites in Thomasville, Georgia were se lected for this study (Gatling Branch and Unnamed Creek), with sampling conducted from November 2006 through April 2007. Measurements and/or samples included chemical / physical parameters (temperature, dissolved oxygen, specific conductivity and total suspended solids), macroinvertebr ate communities and benthic organic matter storage. Longitudinal and te mporal effects attributed to beaver activity included changes in dissolved oxygen (DO), invert ebrate abundance and benthic organic matter storage, while effects of construction activities adjacent to pond at Gatling Branch and immediately downstream included profound changes in water temperature, dissolved oxygen and suspended solids (turbidity). Although Maxted et al (2005) reported increased water temperature within and downstream of beaver ponds, signi ficant longitudinal changes in temperature were not observed in Gatling Branch (pre-disturban ce) or Unnamed Creek. However, extensive removal of riparian vegetation along Gatling Branch during human c onstruction activities resulted in increased sunlight penetration and significan t elevation in water temperatur e within and downstream of the beaver pond. Observed temporal variations were at tributed to external / seasonal influences and not to beaver activity. As noted by Maxted et al (2005), decreased dissolved oxygen (DO) within and downstream of beaver ponds was observed at Gatling Branch and Unnamed Creek.

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49 Longitudinal decreases in DO were attributed to increased organic matter (OM) loading within impounded areas and increased biological dema nd for oxygen resulting from decomposition. Changes in DO during November a nd January were assumed to result from beaver activity, with changes during April attributed to construction activities. Additional impacts resulting from human cons truction included significant increases in suspended solids (turbidity) within adjacent stream segments during the April sampling period. This was attributed to removal of riparian vegetation, combined with poor silt barrier performance, facilitating increased lateral i nputs of particulate mate rial and the observed turbidity increase between transects BWUSP and DS100. Unlike Hillman et al (2004), turbidity did not increase significantly approaching the impoundment outlet or downstream for any other sampling period at Gatling Branch (pre-disturb ance) or Unnamed Creek. With such intense changes in temperature, dissolved oxygen, turb idity and potentially invertebrate communities, lotic systems appear to be far more sensitive to anthropogenic disturba nces than impoundment from beavers. Similar to founding by Collen and Gibson (2001), invertebrate abundance in Gatling Branch and Unnamed Creek was significantly lowe r (per unit area) within and downstream of impounded areas for all sampling pe riods. The longitudinal decrease in abundance was attributed to additional stress resulting from reduced DO within beaver impoundments. Although not examined in the current study, Bertolo and Magnan (2006), and Hagglund and Sjoberg (1999) suggested that many fish taxa (brown trout, walleye and lake whitefish) experience reduced abundance within regions of stream affected by beaver. The relationship between an altered food web (i.e. reduced invertebrate abundance) and subsequent reduc tion in fish abundance within

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50 beaver impoundments suggests that beaver have a profound ecological role, ultimately controlling biological st ructure within its zone of influence. In addition to localized changes in ecosyst em structure and function, sequestration of organic matter (OM) within beaver ponds may have global implications. Sequestered organic matter in aquatic systems (i.e. beaver ponds) repr esents a significant co mponent of the global carbon pool, helping to regulate emissions of CO2 and CH4 into the atmosphere through photosynthetic and respiratory pr ocesses (Amundson 2001). Organi c carbon storage at Unnamed Creek occurred at a rate 10 times greater with in the pond than upstream, further demonstrating the storage potential of beaver impoundments. Although the ultimate fate of stored OM is unknown, this vast carbon storage potential clearly offers an overlooked compartment in the mitigation of climate change.

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51 LIST OF REFERENCES AMUNDSON, R. 2001. The soil carbon cycle. Annual Reviews of Eart h and Planetary Sciences 29: 535-562. BERTOLO, A., AND P. MAGNAN. 2006. Spatial and environmental correlates of fish community structure in Canadian shield lakes. Canadi an Journal of Fisheries and Aquatic Science 63: 2780-2792. BUTLER, D. R. 2006. Human induced changes in anim al populations and distributions, and the subsequent effects of fluvial systems. Geomorphology 79: 448-459. BUTLER, D. R., AND G. P. MALANSON. 1995. Sedimentation rates and patterns in beaver ponds in a mountain environment. Geomorphology 13: 255-269. COLLEN, P., AND R. J. GIBSON. 2001. The general ecology of beaver (Castor spp.), as related to their influence on stream ecosystems and ripari an habitats, and the subsequent effects on fish. Reviews in Fish Biology and Fisheries 10: 439-461. EVERETT, S., AND J. SCHAEFER. 2006. Florida Beavers. WEC17. University of Florida / IFAS. FRANCE, R. L. 1997. The importance of beaver lodge s in structuring littoral communities in boreal headwater lakes. Ca nadian Journal of Zoology 75: 1009-1013. HAGGLUND, A., AND G. SJOBERG. 1999. Effects of beaver dams on the fish fauna of forest streams. Forest Ecology and Management 115: 259-266. HILLMAN, G. R., J. C. FENG, C. C. FENG, AND Y. H. WANG. 2004. Effects of catchment characteristics and disturbances on storage and export of dissolved organic carbon in a boreal headwater stream. Canadian Journa l of Fisheries and Aquatic Sciences 61: 14471460. KAPLAN, L. A., R. A. LARSON, AND T. L. BOTT. 1980. Patterns of dissolved organic carbon. Limnology and Oceanography 25: 1034-1043. MARGOLIS, B. E., M.S. CASTRO, AND R. L. RAESLY. 2001. The impact of beaver impoundments on the water chemistry of two Appalachian st reams. Canadian Jour nal of Fisheries and Aquatic Sciences 58: 2271-2283. MAXTED, J. R., C. H. MCCREADY, AND SCARSBROOK. 2005. Effects of small ponds on stream water quality and macroinvertebrate communitie s. New Zealand Journal of Marine and Freshwater Research 39: 1069-1084. MCHALE, M. R., C. P. CIRMO, M. J. MITCHELL, AND J. J. MCDONNELL. 2004. Wetland nitrogen dynamics in an Adirondack forested watershed. Hydrological Processes 18: 1853-1870.

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52 MERRITT, R. W., AND K. W. CUMMINGS. 1996. An introduction to the aquatic insects of North America, (3rd ed.). Kendall Hunt Publishing Co. MORGAN, L. H. 1986. The American B eaver. Dover Publications. RAY, A. M., A. J. REBERTUS, AND H. L. RAY. 2001. Macrophyte succession in Minnesota beaver ponds. Canadian Journal of Botany 79: 487-499. WETZEL, R. G. 1983. Limnology, (2nd ed.). Saunders College Publishing.

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53 BIOGRAPHICAL SKETCH Cody Rick McNeely was born in 1980 in Hins dale, Illinois. The younger of two, he grew up in Lem ont, Illinois, graduating from Lemont High School in 1998. Cody earned his B.S. in environmental sciences from Benedictine Univ ersity (BU) in 2003. Upon graduating, he began working for Carnow Conibear and Associates (CCA) in Chicago, Illinois. While employed with CCA, his job responsibilities incl uded discovery and oversight in the removal of hazardous materials. In August 2005, after two years of employment with CCA, Cody decided to pursue his M.S. in interdisciplinary ecology at the Univers ity of Florida (UF). Upon completion of his M.S. program in December of 2007, he has plans of returning to Chicago and CCA.