Characterization of physicochemical properties, phosphorus (P) fractions and P release of the Everglades Agricultural Area (EAA) canal sediments

Nutrient enrichment from the EAA particularly P is thought to be responsible for the ecosystem changes in the Everglades. Reduction of P loads from the EAA farms through the implementation of Best Management Practices (BMP) have been going on since 1995. Nevertheless years of P loading the EAA canal sediments portends that the sediments can act as P sources affecting water quality in downstream ecosystems for years to come.;Sediment physicochemical properties of the EAA farm and main canals were analyzed. The pH of the canal sediments varied from 7.1 to 8.0 and organic matter content ranged from 20 to 70%. Phosphorus fractionation indicated that the majority of P compounds in the sediments exist as Ca and Mg P, which is generally regarded as stable, but that can be released P over time. Unlike the sediments from the downstream ecosystems organic P content was insignificant and comprised about 6-13% of total P. Phosphorus release from Miami canal was greater than both WPB and Ocean canal. Equilibrium Phosphorus Concentration (EPC) measurements were used to identify sediments either as P sources or sinks. Higher P release from Miami canal sediments resulted in higher EPC values compared to WPB and Ocean canal. The EPC values of Miami canal ranged from 0.07 to 0.15 mg L -1, WPB canal 0.02 to 0.05 mg L -1 and Ocean canal from 0.03 to 0.08 mg L-1. Comparing the EPCw values with the canal water column SRP concentrations, it was concluded that portions of Miami canal and Ocean canal were functioning as a P source. Thus the EAA main canals are the new P sources in addition to the established P sources to the Everglades including the agricultural farms, water from lake Okeechobee. Attempts to reduce P concentrations in the main canals by management of the farm canals can be compensated by P release from the main canal themselves. Thus maintenance and management of the main canals in at least the portions that were found functioning as P source is critical in order to reduce P loads to the Everglades.