Effects of Lake Sediment Removal on Amphibians and Reptiles

 

Research by Matthew J. Aresco and Margaret S. Gunzburger

 

Department of Biological Science, Florida State University, Tallahassee, Florida 32306-1100

phone: (850) 644-9820

email: aresco@lakejacksonturtles.org, mgunzburger@usgs.gov


Page Contents:


Background

Mechanical sediment removal, also called muck removal,  has become an established fisheries management technique for lakes throughout Florida with millions of dollars budgeted and expended annually in these efforts.  In 2001, the Florida legislature began an annual appropriation of about $5.5 million through 2010 to the Florida Fish and Wildlife Conservation Commission (FFWCC), primarily for sediment (muck) removal (Allen, 1999).  The FFWCC Aquatic Resource Enhancement plan for fiscal year 2001-2002 estimated funding needs of $8.7 million for these projects (FFWCC, 2001).  The goal of these projects is usually the removal of organic sediment and aquatic vegetation for purported enhancement to sport fisheries (e.g., centrarchids) and boater access, and is referred to as “fisheries enhancement” or “lake habitat restoration or enhancement” by the FFWCC Division of Fisheries.  Several government and agency documents report on the effect of sediment removal on sport fisheries, but peer-reviewed literature on the effects of sediment removal on other fish and wildlife is scarce.  The 2001 Justification Review of the FFWCC by the State of Florida stated that data on the effectiveness of FFWCC lake restoration projects are limited and that FFWCC staff does not usually conduct rigorous studies to assess the effects of these projects (State of Florida, 2001).  Despite the dearth of data on the long-term effects of sediment removal on lake ecosystems, large-scale sediment removal is scheduled for at least 31 lakes by the FFWCC from 2001-2020 (Allen, 1999).

There are limited data on the effects of sediment removal on fish and invertebrate populations.  An evaluation of sediment removal on fisheries in Lake Tohopekaliga in central Florida consisted of comparisons between treated and control areas after sediment removal but did not include data before sediment removal (Moyer et al., 1995).  Sport fish (largemouth bass, sunfish) were captured at higher frequencies in treated sites than control sites (Moyer at al., 1995).  Conversely, abundance of other fish including bowfin (Amia calva), gar (Lepisosteus sp.), and poeciliids was greater in control sites than treated sites (Moyer et al., 1995).  After sediment removal at Lake Tohopekaliga, total macroinvertebrate taxa, diversity, and density was lower on treated areas than control areas, probably due to the complete removal of live and decomposing aquatic vegetation (Butler et al., 1992).  At Lake Kissimmee, Florida, the effects of sediment removal on fish and plant communities were monitored at two sites for three years post-treatment (Tugend, 2001).  This study suggests that changes in habitat after sediment removal may result in a shift in the dominant fish from poeciliids to Seminole killifish (Fundulus seminolis) and other open water species (Tugend, 2001).  However, the purported benefit of this change in fish community to the lake ecosystem or to sport fisheries is not clear. 

Sediment removal operations may be undertaken for goals other than fisheries enhancement.  In natural wetlands converted to stormwater ponds in suburban areas, sediment removal may be performed during drought periods to increase the volume of stormwater such ponds can accommodate.  In some cases, contaminants or high nutrient loads (e.g., phosphorus) may accumulate in organic sediment and mechanical excavation may be performed to remove these contaminants or excess nutrients from lakes and ponds.  However, media coverage that equates all sediment removal operations to "cleaning up" lakes may create a misconception by the public that decomposing organic sediment on lake bottoms is unnatural and equivalent to pollution and thus, is detrimental to wildlife, water quality, and recreation (Ritchie, 2000). 


Our Research

The objective of our research was to quantify the effect of sediment removal operations on herpetofauna populations at 5 sites in Leon Co., Florida.  Three sites were sections of large, natural lakes; at these sites only a portion of the lake area was treated with sediment removal.  The other 2 sites were suburban ponds that had been previously modified to serve as stormwater ponds, the entire area of these ponds was treated with sediment removal.  

We visited each site daily during the sediment removal process and collected animals overturned by the machinery.  We recorded the number of each species of frog, salamander, turtle, lizard, and snake we found at each site.  Live animals were released as close as possible to the site of capture, and dead animals were preserved for donation to the Florida State Museum Herpetology collection in Gainesville, FL. 

 

Megginnis Arm, Lake Jackson

Lake Iamonia

 

Harriman Pond

McCord Pond

 

Amphibians and Reptiles of Florida Lakes

Florida's shallow lakes with abundant aquatic vegetation and organic sediment are characterized by a diverse ecosystem of vertebrates, including many species of amphibians and reptiles (herpetofauna).  In some cases, the biomass of herpetofauna may exceed that of fish in a lake.  Species of reptiles and amphibians occupy all trophic levels, from primary consumers (tadpoles, cooter turtles) to top predators (softshell turtles, amphiumas), and are important parts of lake ecosystems.    

Salamander

Two-toed amphiuma (Amphiuma means)

Frog

Bullfrog (Rana catesbeiana)

Turtle

Musk turtle (Sternotherus odoratus)

Lizard

Eastern glass lizard (Ophisaurus ventralis)

Snake

Mud snake (Farancia abacura)

Results

Table 1.  Number of individuals of 26 species of reptiles and amphibians collected at 5 sites in Leon Co., Florida during muck removal operations from Dec. 1999-Dec. 2000.  These numbers are minimum estimates, we probably did not rescue all animals at each site.  The majority of animals were collected on the surface of the ground after being turned over by machinery.  At some sites we trapped turtles in drying pools prior to the beginning of dredging operations.

 

 

 

Megginnis Arm 
(1.8 ha) 

McCord Pond 
(0.81 ha)

 Harriman Pond 
(0.41 ha)

Lake Iamonia
(1.7 ha)

Lake Jackson (US 27) (4 ha)

Salamanders
Amphiuma means
Siren lacertina 


30
66


62
43



189


63 
8


11
49

Frogs
Hyla cinerea
Hyla chrysoscelis
Rana catesbeiana
Rana 
  sphenocephala
Bufo terrestris 
Gastrophryne
      carolinensis 

>1
-
>1
>1

>1
1

>1
>1
6
9

>1
-

6

 7 
4


>1

-
>1

>1
>1 

-
-
-
-

1
-

Snakes
Nerodia floridana
Nerodia fasciata
Seminatrix pygea 
Farancia abacura 
Coluber constrictor 
Elaphe obsoleta 
Agkistrodon
       piscivorous 
Lampropeltis getula 
Cemophora coccinea


6
1
6
3
-
-
1

1
-


-
2
-
-
-
1
-

-
-


-
1
-
-
-
-
-

-
-


-
-
-
-
1
-
-

-
1


-
-
-
-
2
-
-

-
-

Lizards
Ophisaurus ventralis 
Scincella lateralis 

-
-

-
-

2
-

1
-

1
1

Turtles
Trachemys scripta
Pseudemys floridana
Sternotherus 
        odoratus 
Kinosternon 
       subrubrum 
Chelydra serpentina
Apalone ferox 
Terrapene carolina 


3
-
4

1

64
1
-


195
30
43

2

11
23
-


69
19
4

4

11
-
-


-
1
3

-

-
-
-


-
-
5

>1

-
-
-

 


Conclusions

 

The results of this research have been presented at three scientific meetings: Florida Lake Management Society (May 2001), Joint Annual Meeting of SSAR/HL/ASIH (July 2002), and PARC Southeast Regional Working Group  (Oct 2002).  In addition, a manuscript of the results of this research has been published:

Aresco, M.J., and M. S. Gunzburger.  2004.  Effects of large-scale sediment removal on populations of herpetofauna in Florida wetlands.  Journal of Herpetology 38(2):275-279.


Literature Cited and Links to More Information on Sediment Removal

Allen, H.  1999.  Clear vision for lake enhancement.  Florida Fish and Wildlife Conservation Commission, Division of Fisheries, Fisheries Updates, Tallahassee, FL. Available online

Butler, R. S., E. J. Moyer, M. W. Hulon, and V. P. Williams.  1992.  Littoral zone invertebrate communities as affected by a habitat restoration project on Lake Tohopekaliga, Florida.  Journal of Freshwater Ecology 7:317-328.

Florida Fish and Wildlife Conservation Commission.  2001.  Proposed aquatic resources enhancement work plan for 2001-2002.  Tallahassee, FL

Moyer, E. J., M. W. Hulon, J. J. Sweatman, R. S. Butler, V. P. Williams.  1995.  Fishery responses to habitat restoration in Lake Tohopekaliga, Florida.  North American Journal of Fisheries Management 15: 591-595. 

Ritchie, B.  2000.  Drought will help fish, boats: it’s a great time to clean up Lake Iamonia.  Tallahassee Democrat.  2000 Jun 21:1A (col. 1), 2A (col 1).

State of Florida.  2001.  Justification Review, Florida Fish and Wildlife Conservation Commission. Office of Program Policy Analysis and Government Accountability.  Report No. 01-48. Available as a pdf file

Tugend, K. I.  2001.  Changes in the plant and fish communities in enhanced littoral areas of Lake Kissimmee, Florida, following a major habitat enhancement.  Unpubl. Thesis, Univ. of Florida, Gainesville. 

 

 


Site last updated 19 August 2006