Mangrove forests dominate the downstream end of the Greater Florida Everglades. Restoration of the Everglades has concentrated on surface water flow. We measured rates of sediment (surface) elevation change and soil accretion in relation to both surface and groundwater elevation at six sites in the lower Everglades, including freshwater marsh and mangrove habitats. Three sites were located along the two major distributaries of the Everglades: Shark River and Lostmans River. Accretion was negligible in upstream, freshwater marsh sites and greatest in downstream mangrove forest sites. Sediment elevation changes were substantial at all sites. More importantly, the pattern of sediment elevation change differed from upstream to downstream, and was different between downstream sites on each river. The rate of sediment elevation change was related to the rate of groundwater elevation change at many, but not all, sites. For freshwater sites, as groundwater elevation increased, sediment elevation decreased, an unexpected finding. For downstream, mangrove sites, a weak positive relationship was found whereby increasing groundwater elevations lead to increasing sediment surface elevation. Important seasonal patterns also appear to be present indicating that subsurface processes (root growth, decomposition, water storage) may play important roles in marsh / mangrove surface elevation. If restoration of freshwater sheetflow in the upstream Everglades leads to increased groundwater elevations in the downstream system, mangrove forests may be able to keep even with current rates of sea level rise.

¹Tom_J_Smith@usgs.gov U.S. Geological Survey, Center for Coastal & Regional Marine Studies, 600 Fourth St., South, St. Petersburg, FL 33701 United States ²Don_Cahoon@usgs.gov U.S. Geological Survey, Center for Coastal & Regional Marine Studies, 600 Fourth St., South, St. Petersburg, FL 33701 United States