Water quality and eutrophication in Tampa Bay, Florida

A water quality model, WASP, was applied to simulate and evaluate the mecha nistic relationships between external nutrient loading and water quality of Tampa Bay, U.S.A. The model quantifies processes governing internal nutrie nt cycling and phytoplankton growth. It estimates the impact of nutrient lo ads on water clarity, a pivotal water quality parameter for seagrass meadow s. The model estimates impacts over long time periods and large areas, usin g tidally-averaged modelling: tidally-averaged impacts were described by di spersion coefficients, calibrated with 1985-1994 salinities. These coeffici ents and monthly freshwater inflows were used to simulate both salinity and eight water quality variables. They involved four interacting systems: dis solved oxygen, phytoplankton, nitrogen and phosphorus concentrations. Model results were compared with monthly measurements and yearly-averaged estima tes for 1985-1994. Tampa Bay was phosphorus enriched and nitrogen limited f or algal growth. A component analysis indicated that the internal nutrient cycling and transport exceeded external loadings (external inputs from the watershed are the ultimate source of nitrogen). Cycling of nitrogen was gov erned primarily by phytoplankton, including growth, death and mineralizatio n of organic-N. (C) 1999 Academic Press.