A model of phytoplankton competition for limiting and nonlimiting nutrients: Implications for development of estuarine and nearshore management schemes

The global increase of noxious bloom occurrences has increased the need for phytoplankton management schemes. Such schemes require the ability to predict phytoplankton succession. Equilibrium Resource Competition theory, which is popular for predicting succession in lake systems, may not be useful in more dynamic environments, such as estuaries and coastal waters. We developed a mathematical model better suited to nonsteady state conditions. Our model incorporated luxury consumption of nonlimiting nutrients and cell starvation processes into a cell-quota-based nutrient-phytoplankton scheme. Nutrient pools described included nitrogen and phosphorus. Phytoplankton groups characterized in the model were a phosphorus-specialist, a nitrogen-specialist, and an intermediate group. We emphasized competition for nutrients under conditions of continuous and pulsing nutrient supply, as well as different nutrient loading ratios. Our results suggest that delivering nutrients in a pulsing fashion produces dramatic differences in phytoplankton community composition over a given period, that is, reduction of accumulated biomass of slower growing algae. Coastal managers may be able to inhibit initiation of slow-growing noxious blooms in estuaries and coastal waters by pulsing nutrients inputs from point sources, such as sewage treatment plants.