Topical Area: Water Quality & Nutrient Dymanics (Poster Only)

Frank P. Parker and Daniel L. Childers, Southeast Environmental Research Program, Department of Biological Sciences, Florida International University, Miami, FL ; Christopher Madden, Everglades Systems Research Division, South Florida Water Management District, West Palm Beach, FL

Everglades restoration efforts are focusing on large-scale changes in water delivery to Everglades wetlands. These changes include increased water inputs and associated changes in nutrient regimes in a freshwater-estuarine system that we are currently studying in eastern Everglades National Park (ENP). In 1997, a levee was removed from along the major drainage canal that delineates the northern boundary of this ENP Panhandle region in order to increase sheetflow through these wetlands and to Florida Bay. Between this canal and the estuary, wetlands range from sawgrass marsh to mixed Cladium-Rhizophora wetland to scrub red mangrove forest, respectively. Our ENP Panhandle sampling began in Fall 1997, at which point over half of the levee had already been removed. We established a wetland transect roughly normal to the canal and behind the remaining levee. Throughout the remaining 1997 wet season, we sampled water overlying the sawgrass marsh along this transect both intensively (every 3 hours for 48 hours) and extensively (every 2 days continuously). Approximately halfway through our sampling, levee removal was completed.

Our water chemistry data from before and after levee removal show that nutrient concentrations in wetland surface water more than doubled after removal of the levee, from about 0.2 to 0.4 m M TP and from about 45 to 140 m M TN. When combined with the large increase in wetland sheetflow from the new inputs of canal water, this represents a significant increase in nutrient loading to the ENP Panhandle wetlands and perhaps even to the Florida Bay estuary. However, the sawgrass marsh within 3 km of the canal appears to be removing much of this nutrient load. Interestingly, this wetland uptake phenomenon did not immediately show up as increased porewater nutrients in these wetlands. Furthermore, cores taken before and after levee removal show an inhibition of C mineralization (via aerobic respiration, sulfate reduction, and methanogenesis) in wetland soils receiving increased canal inflows; this in spite of the fact that C decompositional processes in Everglades wetland soils are strongly phosphorus limited. We have not yet observed any changes in soil porewater salinities or sawgrass productivity since the levee was removed and sheetflow increased, but we would anticipate a significant lag in response by such parameters—and levee removal was only completed in late October 1997.

We will continue to quantify these parameters over the next 3 years, along 2 parallel transects. Additionally, we will extend our transects through the mangrove wetland zone and to the Florida Bay confluence, and we will construct and sample replicate flumes immediately adjacent to the canal edge, to more accurately quantify nutrient uptake and transformations by the sawgrass marsh. Thus, our research will continue to quantify how freshwater wetlands in the ENP Panhandle region are mediating the quantity and quality of additional water inflow that reaches the Florida Bay estuary, in response to Everglades restoration efforts.