SANTA ROSA BEACH - Come to Topsail Hill Preserve State Park and discover a natural feature that sets it apart from other recreational and natural areas in the world; rare natural coastal dune lakes. These lakes are so rare that they are considered globally imperiled by the Florida Natural Areas Inventory. Currently there is not a consensus on what defines a coastal dune lake. The locations of coastal dune lakes include New Zealand, Australia, Madagascar, the Northwestern United States and Northwest Florida. With 15 coastal dunes lakes, Walton County has the highest concentration of coastal dune lakes in the world. Topsail Hill Preserve State Park has three major coastal dune lakes, including Morris, Campbell and Stallworth Lakes, and two minor unnamed coastal dune lakes encompassing more than 170 acres of these freshwater lakes.
Visitors come from all over the world to see these rare lakes at Topsail Hill.
Coastal dune lakes are unique from other lakes or lagoons due to their intermittent connection to the Gulf of Mexico. They form in many ways, such as wind activity in arid regions where wind erodes rock and redistributes sand. U.S. coastal dune lakes in the Gulf Coast were most likely relic lagoons shaped by both erosional forces of wind and waves. These same forces still affect the lakes today.
Coastal dune lakes within Topsail Hill Preserve State Park are separated from the Gulf of Mexico by sands that form beach and dune systems. Freshwater seeps laterally into the lakes through the sand.
When these lakes reach their maximum capacity of holding freshwater due to rain and groundwater seepage, the weakest area of sand around the bank separating the lake from the Gulf, “blows out.” This creates an outfall connecting the lakes to the Gulf. The outfall will fill with sand at various rates of time plugging the outfall.
This dynamic process that opens and closes the outfall creating its intermittent connection to the Gulf is unique to coastal dune lakes. Some coastal dune lakes are connected to the Gulf through their outfall for long periods of time and outfalls of other lakes rarely open.
The amount of saltwater in coastal dune lakes varies from lake to lake depending on how long its outfall is open to the Gulf. Another significant source of saltwater in coastal dune lakes is from storms that push saltwater into the lakes through the outfall or overwash from dunes.
Dune lakes provide habitat and forage for a diversity of plants and animals that range from fresh, estuarine, to marine. This allows several different types of plants and animals to use this environment. While the outfall is open and freshwater is being released from the lake, tidal water and marine organisms enter the lake. Migratory birds rely on the coastal dune lakes within Topsail Hill Preserve State Park as a refuge on an arduous journey along their route. The lakes and the habitats around them, including maritime hammocks, are used heavily by neo-tropical birds as stopover sites for resting, feeding, and cover during spring and fall migrations. While walking along the lake, you may find wading birds foraging, such as beautiful egrets, or birds of prey such as ospreys and hawks.
Campbell and Morris Lake are important for research due to the lack of urban interface surrounding them, unlike the other lakes in Walton County. Currently, Campbell Lake is part of a hydrology study the Choctawhatchee Basin Alliance contracted with University of Florida. There are three lakes in Walton County that have wells that monitor the groundwater nutrients flowing into them: Draper, Camp Creek and Campbell.
“Campbell Lake was chosen as a control because it doesn’t have homes surrounding it,” said Sarah Kalinoski of the Choctawhatchee Basin Alliance. “We are hoping to expand this study in the hope that it will draw more Ph.D. students into researching the coastal dune lakes.”
Trained volunteers with Choctawhatchee Basin Alliance’s Coastal Dune Lake Program take pride in monitoring these important lakes. The Coastal Dune Lake Program is a team effort where volunteers work with CBA and researchers at the University of Florida’s Lakewatch Program to collect basic information and contribute to the understanding of Florida’s lakes.
If you are interested in receiving training and becoming a CBA volunteer or supporting Lakewatch in your community, contact Sarah Kalinoski at cdlakes@owcc.net.
Leda Suydan is park service specialist at Topsail Hill Park and Preserve. You can reach her at (850) 267-0299 or at leda.suydan@dep.state.fl.us.