Impact of Storm Water Treatment Drainage Flow On Phosphorus Forms of L-40 Canal Surrounding ARM Loxahatchee National Wildlife Refuge.

ARM Loxahatchee National Wildlife Refuge is one of three conservation areas in south Florida designed to provide water storage and flood control, and habitat for native fish and wildlife. Most of the Everglades, including the refuge, developed as a rainfall driven system with surface waters low in nutrients. Increases in drainage flow of agricultural and urban runoff water through the Stormwater Treatment Area (STA-1E) may suspend and transport light organic sediments and nutrients to receiving canals which could negatively impact the fragile ecosystem inside the refuge. Our objective was to measure the effect of drainage flow from STA-1E on different phosphorus (P) forms: Total P (TP), total dissolved P (TDP), particulate P (PP), and soluble reactive P (SRP) in the L40 Canal. The canal was sampled in 12 locations; three above and nine below the STA-1E discharge; along 32 km of the canal, and was monitored for three Water Years (May 2006- April 2009). During high drainage flow conditions TP concentrations were significantly lower (p<0.05) than during no drainage flow conditions, where as SRP concentrations were significantly higher (p<0.05) during high drainage flow conditions than during no drainage flow conditions. Particulate P concentrations were higher near the discharge point and leveled off along the L-40 canal; however particulate transport and deposition occurring during flow conditions resulted in a higher PP build-up towards the south end of the canal. Results suggest that P forms in L40 Canal are driven by both drainage flow conditions and the composition of underlying canal sediments.