Alan Wright1, K.R. Reddy1, and Susan Newman2. (1) University of Florida, Everglades Research & Education Center, 3200 E. Palm Beach Rd., Belle Glade, FL 33430, (2) South Florida Water Management District, West Palm Beach, FL 32611
Soil chemical properties may serve as sensitive indicators of nutrient loading to wetland ecosystems. We investigated the effects of nutrient loading on the distribution of soil C, N, and P along enrichment gradients in four wetlands of the 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 chemical properties were similar among all wetlands regardless of background nutrient levels. Total P levels in oligotrophic areas varied considerably between wetlands, from 205 to 619 mg kg-1 for floc and from 200 to 553 mg kg-1 for soil (0-3 cm). Floc had greater assimilative capacity for P than underlying soil, as all P fractions were highest in floc. Assessment of the impacts of nutrient loading indicated that P-related parameters were best suited as indicators. The most sensitive indicator with the greatest response to nutrient loading was NaHCO3-Pi (labile P). Labile P was 1973% greater in floc and 727% greater in soil for impacted than 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 impacts of nutrient loading.