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Stop #12: Lake Okeechobee, FL
Featured Herp: Softshell Turtles (genus Apalone)

view of water and sawgrass
The Everglades, also known as the "River of Grass"

East Aiken students arrived near Lake Okeechobee on November 22, 1999, when they officially entered "South Florida." There are few places in the world that can compare to South Florida as a place where students can study the dramatic impacts that humans can have on the environment.

South Florida in the 1700ís was very different from the area today. Water flowed down the winding Kissimmee River, into Lake Okeechobee, and sometimes out into the Everglades (Note: much more information will be presented on the Everglades ecosystem in the next few weeks). Between Lake Okeechobee and the tip of Florida lay the Everglades, a "River of Grass" 100 miles (162 km) wide in places, where a sheet of shallow water flowed slowly southward to Florida Bay. The soil south of Lake Okeechobee was incredibly deep and fertile, a result of thousands of years of accumulation and breakdown of rich plant material.

Lake Okeechobee itself is an inland remains of what once was a shallow sea, the Pamlico Sea, which covered much of South Florida 100,000 years ago. The present day lake is the second largest (after Lake Michigan) freshwater lake in the continental U.S.-- it is 45 miles (73 km) across and approximately 730 square miles (1900 square km or 185,000 hectares) in area. The average depth is only about 10-12 feet (3-3.7 meters). It is no surprise that the Seminole Indians named it Lake Okeechobee, or "Big Water."

South Florida canals are used to control flooding and irrigate cropland

A few years after Florida gained statehood in 1845, the new Floridians began to talk of draining the southern part of the state. It took awhile, but by the 1930ís over 400 miles of drainage canals had been constructed. Levees were built south of Lake Okeechobee to prevent flooding during severe storms. A large Agricultural Area and several Water Conservation Areas were established. In short, the natural timing and amount of water flowing southward from Lake Okeechobee were altered dramatically. What this has meant to the habitats and animals of South Florida will be discussed more fully in coming weeks.

For more detailed information on Lake Okeechobee and Everglades history, visit: Nova Southeastern University studies, Everglades water history, and Okeechobee history.


Softshell Turtles (genus Apalone) and Environmental Contaminants

closeup of softshell head

Three species of softshell turtles occur in the Southeast, and all three can be found in parts of Florida. One species, the Florida softshell, ranges throughout all of Florida, and has a strong preference for lake habitats. Lake Okeechobee, as the "Mother of all Florida lakes," is excellent softshell habitat.

Softshell turtles take their name from the leathery skin that covers their carapace (the upper part of the shell). The skin-covered shell is an adaptation that allows softshells to remain underwater for long time periods, as they can actually take in oxygen and rid their bodies of carbon dioxide through the blood-vessel rich skin while they are submerged. When softshells are out of the water, however, their bodies lose water faster than bony-shelled turtles, and dehydration can be a concern. It is also possible that the ability to "breathe" through the skin makes softshells more sensitive than other turtles to some water-borne chemical pollutants.

swimming softshell

Environmental contaminants, in the form of chemicals that have been released into an ecosystem, are of increasing concern to many scientists who study wildlife. Partners in Amphibian and Reptile Conservation (PARC, the parent organization of SPARC), has identified environmental pollutants as one of the six major threats to reptile and amphibian populations. Contaminants may cause many detrimental effects in wildlife, some of which are obvious, but some of which may be more subtle. In other words, whereas an oil or a pesticide spill may kill animals in the area of the release, some contaminants may cause harm after many months or years of exposure.

side view of head
southeastern distribution

The study of the effects of contaminants on organisms is called toxicology. Both amphibians and reptiles are relatively understudied when it comes to effects of contaminants on wild populations. The fact that many herp species appear to be sensitive to very small concentrations of contaminants [for example, amphibian sensitivity to nitrates in fertilizer runoff (click here to learn more), or alligator and turtle sensitivity to some pesticides] is noteworthy, and needs additional research by scientists.

>Softshell Turtle Fact Sheet

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