Assessment of Aquatic Vegetation and Salinity in Coastal Wetlands of Florida Rivers
Estuaries are highly productive ecosystems that occur where rivers flow into the sea and freshwater mixes with saltwater. These unique areas contain diverse plants and organisms that generally follow a gradient where species adapted to freshwater occur at the upstream reaches in the river and marine species occur at the downstream reaches by the sea. Rivers and estuaries provide valuable environmental and economic benefits. Fish and aquatic organisms utilize nursery habitat provided by plant communities including mangroves, salt marshes, and seagrass beds that are common in estuaries and floodplain wetlands that are common along rivers. These habitats support recreational and commercial fisheries that significantly contribute to the national economy of the United States.
Environmental influences can disrupt the balance of freshwater and saltwater in coastal ecosystems. Sea level rise has potential to increase both salinity and duration of inundation in coastal wetlands, with effects on aquatic plants and habitats being uncertain. Changes in rainfall patterns may also influence salinity levels via modified flow rates in rivers, altering the freshwater inputs to coastal wetlands. Alternating periods of low and high river flows, combined with continued sea level rise, may result in extended periods of high and low salinity that alternately approach or exceed the tolerances of freshwater and marine species.
Understanding the changes that are taking place and their influence on coastal habitats is vital for informing resource managers of opportunities to alleviate or minimize the impacts of extreme environmental factors. Rooted aquatic plant communities can be used as an indicator of stability or change in habitats and habitat value to fish and wildlife by examining common and dominant species over time. Salinity data can be examined to evaluate trends along coastal reaches of rivers. With the backing of the State Wildlife Grants program, Freshwater Plants researchers will complete a project during 2025-2027 to document the spatial distribution of common freshwater, brackish, and marine aquatic plants and associated salinity levels in ten rivers along Florida’s gulf coast. Data will be compared to available historical records to examine stability or change to date and may be used as reference data for future assessments of habitat conditions. Rivers selected for study include the Peace River (Charlotte and DeSoto Counties), Manatee River (Manatee County), Chassahowitzka River (Citrus County), Withlacoochee River (Citrus and Levy Counties), Suwannee River (Dixie and Levy Counties), Econfina River (Taylor County), Ochlockonee River (Franklin and Wakulla Counties), Apalachicola River (Franklin and Gulf Counties), Choctawhatchee River (Walton County), and Yellow River (Santa Rosa County).
Aquatic vegetation along the Withlacoochee River. (Top) Near the gulf at the river mouth and (bottom) along the shoreline in the main stem of the river.