NUTRIENT AND PHYTOPLANKTON DYNAMICS IN A SEWAGE-IMPACTED GULF-COAST ESTUARY - A FIELD-TEST OF THE PEG-MODEL AND EQUILIBRIUM RESOURCE COMPETITION THEORY

Eutrophication and noxious bloom events are becoming more prevalent wi th increasing anthropogenic activities. To lessen ecological damage, t here is a need to develop phytoplankton management programs aimed at e nhancing growth of beneficial algae. The success of such management sc hemes will be dependent on the predictability of phytoplankton success ion within the target system to a controlled perturbation. Freshwater lakes appear to exhibit a degree of predictability as described by the PEG-model and Equilibrium Resource Competition theory. We investigate d whether these concepts could be applied to a marine system, the Nuec es River estuary, Texas. The PEG-model predicted nicely the initial oc currence of edible phytoplankton forms after a favorable nutrient pert urbation. Equilibrium Resource Competition theory, however, only succe ssfully predicted the occurrence of major phytoplankton taxa immediate ly after a nutrient perturbation. Systemwide correlations between N:P and cyanobacteria, green algae, and diatoms were poor. In the Nueces R iver estuary, succession within the phytoplankton community showed a d egree of predictability to nutrient perturbations. Therefore, manageme nt of the phytoplankton community composition may be possible. The PEG -model appears to be a useful guide for a phytoplankton management sch eme, while the utility of Equilibrium Resource Competition may be limi ted.