Salt Lake is influenced by relict salt water-water that has remained under layers of sand and shell for thousands of years, since the land was under the sea. Over time this salt water mixed with fresh water in the upper aquifer.
Scientist William McLane surveyed lakes along the St. Johns River in the late 1940s and early 1950s. He found salinities in Salt Lake as high as 10,700 parts per million, about one-third the salinity of the Atlantic Ocean at the mouth of the St. Johns River. McLane also found breeding populations of five marine crustaceans, two marine worms, and nine saltwater fish.
The salinity of the soil also influences the marsh vegetation surrounding the lake. In some places, the soil is so salty that it can be tolerated only by one plant species called glasswort.
The site of a former cattle operation on unimproved pastures, Salt Lake WMA still contains many native plant communities. The area is part of a transitional zone between temperate and subtropical climates, so it has plant communities and species from both climates.
Some natural communities have been altered because in the past natural fires have not been allowed to burn. Historic cattle and forest management practices have also modified them.
Much of the Salt Lake landscape has not been burned in 20 years or more. FWC has implemented a prescribed burning program in the pine flatwoods, scrub, and selected marsh communities. In many places, roller chopping will be required before burning can be carried out. Prescribed fire is used to reduce hazardous fuel accumulation and to increase species diversity of both flora and fauna. Fire is a natural force in Salt Lake's uplands and marshes, and many native plants and animals are adapted to it. In fact, they require fire to survive. Managers aim to create a mosaic of burned and unburned areas to increase habitat diversity.