Florida's Stormwater Treatment Areas (STAs) are large artificial freshwater wetlands designed to naturally remove nutrients (especially phosphate) from water. Everglades wetlands are naturally poor in nutrients, and there is considerable concern that phosphate leaching from fertilizers used in agriculture may be harming Everglades ecosystems and causing fundamental changes in biodiversity. Managed by the South Florida Water Management District (SFWMD), the STAs are designed to naturally remove this phosphate: water is pumped from agricultural areas into the STAs, wherein phosphate is taken up by plants (such as cattails and hydrilla) and stored in their biomass. STAs are remarkably effective: dissolved phosphate concentrations decrease from 150 parts per billion (ppb) to 10-15 ppb as water flows through them. This leads to a pronounced gradient in phosphate concentrations within the STAs, which makes them ideal laboratories for studying how nutrient levels might affect the abundance and distribution of aquatic organisms in Everglades wetlands. This interdisciplinary project addresses several important knowledge gaps, as identified by SFWMD personnel and Everglades researchers. First, we propose to GIS-map phosphate concentrations in STA 3/4, the largest of the STAs (indeed, the largest artificial wetland in the world), using water quality data routinely collected by SFWMD. Second, we propose to collect data on the biodiversity, abundance and distribution of macroinvertebrates (such as insects, shrimp, and snails) and fishes at sites with differing concentrations of phosphorus, and explore how phosphorus levels affect diversity and shape communities of aquatic organisms under the controlled conditions of STA 3/4. Third, we propose to use two sentinel fish species to examine how phosphorus levels affect fish growth, physiological condition, reproduction, and general health in this system.