Megginnis Arm, Lake Jackson
Lake Iamonia
Harriman Pond
McCord Pond
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:
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).
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) |
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 |
McCord
Pond |
Harriman Pond |
Lake
Iamonia |
Lake Jackson (US 27) (4 ha) |
|
Salamanders |
|
|
|
|
|
|
Frogs |
>1
>1
|
>1
>1
|
6
1
|
>1
>1
|
- 1
|
|
Snakes |
1
|
-
|
-
|
-
|
-
|
|
Lizards |
-
|
-
|
2
|
1
|
1
|
|
Turtles |
1 64
|
2 11
|
4 11
|
- - |
>1 - |
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
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
