Biogeochemical Response of the Everglades Landscape to Eutrophication

The response of soil biogeochemical properties to external nutrient loading may serve as sensitive indicators of eutrophication in wetland ecosystems. We investigated the effects of nutrient loading on the distribution of soil C, N and P in four wetlands of the Florida Everglades: Water Conservation Area (WCA)-1, WCA-2a, WCA-3a and Taylor Slough. The nutrient-impacted zones extended from water-inflow points into interior areas and varied greatly between wetlands, from 0.5 km in WCA-1, 7 km in WCA-2a, 3 km in WCA-3a and 12 km in Taylor Slough. Nutrient loading effects on soil properties were similar among all wetlands regardless of background nutrient levels. Total P levels in oligotrophic areas varied considerably, from 205 to 619 mg kg for floc and from 200 to 553 mg kg for soil (0-3 cm). Floc had greater assimilative capacity for P 1 1 than underlying soil. Assessment of the impacts of eutrophication indicated that P-related parameters were best suited as indicators. The most sensitive indicator with the greatest response to nutrient loading was NaHCO -Pi 3 (labile P). Labile P was 1973% greater in floc and 727% greater in soil for impacted compared to oligotrophic areas. Soil C and N properties were more indirectly related to nutrient loading through the influence of plant production and organic matter dynamics. Delineation of impacted and oligotrophic wetland areas in the Everglades ecosystem may serve as a baseline to assess future responses of biogeochemical properties to eutrophication.