PHOSPHORUS STORAGE CAPACITY OF UPLANDS, WETLANDS AND STREAMS OF THE LAKE OKEECHOBEE WATERSHED, FLORIDA

Lake Okeechobee, a subtropical, shallow lake in south Florida, is seve rely affected from eutrophication resulting from non-point source agri cultural phosphorus (P) loading. The Lower Kissimmee River and Taylor Creek/Nubbin Slough watersheds are major contributors of P to Lake Oke echobee with 57% of the total P load attributed to these two watershed s. Major land use in these watersheds are dairy and beef pastures. Soi ls are dominated by Spodosols. The P storage capacity of uplands, wetl ands and streams in the Lake Okeechobee Watershed was estimated based on the analysis of soil and vegetation, and imports of P into the wate rshed. Results showed that about 70% of the total P imported into the watershed is stored in uplands, and an additional 18% is stored in wet lands and streams. Phosphorus retention in soils was strongly associat ed with Al and Fe oxides and total organic carbon. Phosphorus storage in vegetation was found to be short-term and accounted for less than 5 % of the total P storage, Phosphorus retention characteristics of soil s and sediments suggest that about 75% and 45% of the storage capacity is still available for additional retention in uplands, wetlands and stream sediments, respectively. Although the watershed has a large cap acity to store P, continuous loading can decrease the P buffering capa city of soils and sediments and increase P levels in surface and sub-s urface flow.