Changes in Ecosystem Structure and Composition Influence Groundwater Chemistry in Herbaceous Wetlands.

Along coasts, biologically diverse terrestrial wetlands and marine ecosystems maintain complex hydrological connections that influence groundwater quality. The coastline of Florida's panhandle is home to globally rare coastal dune lakes that are hydrologically influenced by unique wet prairies within their watersheds. Little is known regarding how changes in ecosystem structure and composition of wet prairies influences groundwater chemistry within these coastal dune lake watersheds. To identify how physical and biological characteristics of terrestrial wetlands influence water chemistry, we analyzed water quality parameters along an upland to wetland gradient of shrub-encroached and fire-maintained wetlands within four of Florida's coastal dune lake watersheds between 2018 and 2021. Shrub-encroached wetlands had significantly higher (p ≤ 0.01) specific conductivity, salinity, acidity, and ion concentrations (Cl−, SO42−, K+, Na+, and Mg2+) than fire-maintained wetlands. Ions in groundwater were similar across the upland to wetland gradient with exception of chloride which was significantly lower (p ≤ 0.01) at upper slope positions where encroaching shrubs were less dense. The sulfate in groundwater was twice that of streams and salinity was most concentrated at the bottom slope positions. As results show that shrub encroachment has a measurable relationship with water chemistry, restoration of herbaceous wetlands through shrub removal may improve water quality and minimize future impacts to Florida's coastal dune lakes. [ABSTRACT FROM AUTHOR]