Spatial and temporal phosphorus distribution changes in a large wetland ecosystem

Abstract

Long‐ and short‐term changes in the spatial distribution of surface water phosphorus concentrations were assessed for the Everglades wetland (USA) from 12 years of monitoring data. Changes in phosphorus spatial distributions, before and after implementation of measures to reduce phosphorus, including stormwater treatment areas (STAs) and best management practices (BMPs), were used to evaluate the effect of the remediation strategies in the naturally oligotrophic wetland. Results showed a clear spatial and temporal gradient in phosphorus concentrations, with highest total phosphorus (TP) reaching 200μg/L in the northern Water Conservation Areas (WCAs) because of canal inflow from the Everglades Agricultural Area (EAA). Long‐term records of TP concentrations from 1995 to 2007 showed declines in Water Conservation Area WCA1 during the dry season (−5.1%). Short‐term changes (2003–2007) showed increasing trends in TP concentrations elsewhere in the Everglades, mainly in the southern areas: WCA3 and Everglades National Park (ENP). From 2003 to 2007, phosphorus increased by 7.4% per year in the ENP during the dry season. The area of the Everglades that exceeded the 10μg/L surface water TP concentration ecological threshold was quantified and showed a long‐term overall decline. However, except for the ENP, more than 65% of the Everglades surface area exceeded the 10μg/L water quality threshold in 2007. During recent years, ENP and WCA3 surface areas that exceeded the alternative 15 μg/L annual geometric mean slightly increased, confirming the need to closely monitor these two regions.