Microbial Indicators of Eutrophication in Everglades Wetlands

Nutrient loading has been implicated as a major cause of ecological changes in Everglades Wetlands. The main objective of this study was to assess changes in microbial indicators in response to nutrient loading across the Everglades landscape. Soil chemical, physical, and microbial properties were measured for nutrient-impacted and oligotrophic sites within Water Conservation Area (WCA)-1, WCA-2a, WCA-3a, and Taylor Slough of Everglades National Park. Impacts of nutrient loading were most evident by the development of gradients in floc and soil total P from peripheral to interior areas of all wetlands following the paths of surface water flow. Floc was more responsive to nutrient loading than the underlying soil. The sensitive indicators of eutrophication were floc and soil total P, microbial biomass P, and mineralized P. Total P averaged 185 and 140% greater for nutrient-impacted than oligotrophic areas for floc and soil (0-3 cm), respectively. Microbial biomass P averaged 97 and 52% higher at nutrient-impacted than oligotrophic areas for floc and soil, respectively. Mineralized P was the most sensitive indicator of eutrophication, being 689 and 135% higher at nutrient-impacted than oligotrophic areas for floc and soil, respectively. Microbial indicators in WCA-3a and Taylor Slough were more responsive to nutrient loading than in WCA-1 and WCA-2a, which received higher P loads. Delineation of nutrient-impacted and oligotrophic areas in Everglades wetlands may serve as a baseline to assess future impacts of eutrophication. The consistent pattern in the response of microbial processes to nutrient loading across the range of conditions in different Everglades wetlands demonstrates their suitability as sensitive indicators of eutrophication.