The Everglades Stormwater Treatment Areas are comprised of multiple wetland cells, many of which have extremely long flow paths (up to 4.7 km). The large size of these wetlands facilitates effective P removal. The spatial diversity in micro-environments, in turn, can influence phosphorus (P) removal and cycling within the wetland.

In order to characterize phosphorus removal and cycling within an STA flow path, we collected water samples over 3 years from locations along nine transects established perpendicular to flow within Stormwater Treatment Area 2 (STA 2) Cell 3. This 898-ha wetland receives primarily agricultural drainage water (ADW) and is dominated by submerged aquatic vegetation (SAV). Samples were characterized with respect to total P, soluble reactive P (SRP), dissolved organic P (DOP) and particulate P (PP) concentrations.

Our sampling efforts revealed several unique factors related to internal P cycling within STAs. First, outflow region TP concentrations typically were lower during moderate to high loading events than under more stagnant conditions. Second, we observed considerable spatial variation in PP levels within the wetland, particularly during stagnant conditions. The elevated PP concentrations under stagnant conditions may be related to internal P cycling processes, such as proliferation of phytoplankton supported by sediment P release.