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item Sigua, Gilbert

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/25/2004
Publication Date: 3/12/2004
Citation: Sigua, G.C. 2004. Basin wide assessment of nitrogen and phosphorus loadings in the indian river lagoon, florida. Orlando Florida March 12-13,2004 Meeting Abstract. Florida Academy Abstract Book. p. 15.

Interpretive Summary:

Technical Abstract: Establishment of a watershed scale seagrass-based nutrient load assessment is the major aim of water quality management in the Indian River Lagoon (IRL). The development of such targets requires information on nutrient concentration, external nutrient loading rates, sediment nutrient flux estimates, and rate estimates of nutrient turnover (uptake and release) among the major plant communities in the IRL. There is growing evidence that the ecological and biological integrity of the lagoon has declined during the last 50 years, probably due to the decline in water quality. Best estimate loadings should incorporate watershed-scale wet and dry deposition, surface water, groundwater, sediment nutrient flux, and point source effluent discharge data. On the average, the IRL is receiving annual external loadings of 832,645 and 94,476 kg of total nitrogen (TN) and total phosphorus (TP), respectively from stormwater discharges and agricultural runoff. The average internal cycling of TN and TP from sediment deposits in the IRL was about 42,640 kg TN and 1,050 kg TP per year. Indirect evidence suggests that atmospheric deposition has played a role in the ongoing nutrient enrichment in the IRL. The estimated total atmospheric deposition of TN and TP was about 32,940 and 824 kg per year, while groundwater contribution was about 84,920 and 24,275 kg per year, respectively to the surface waters of the IRL. The estimated annual contribution of point effluent discharge was about 60,408 kg TN and 7,248 kg TP. In total, the IRL basin is receiving an annual loading of about 1,053,553 kg TN and 127,873 kg TP. With these results, it is clear that the current rate of nutrient loadings is causing a shift in the primary producers of the IRL from macrophyte to phytoplankton- or algal-based system. The goal is to reverse that shift, to attain and maintain a macrophyte-based estuarine system in the IRL.