Nutrient composition and phytoplankton community dynamics in the New River Estuary

Inorganic and organic nitrogen loading may be linked to the persistence of algal blooms in the New River estuary. Characterizing these loads and investigating their role in shaping natural phytoplankton assemblages was the focus of this thesis. Water samples from a 10 station transect were analyzed for urea, nitrate, ammonium, orthophosphate, dissolved organic nitrogen, chlorophyll a, salinity, and temperature. Nutrient addition bioassays were run to examine the effects of varying nutrient loads on an estuarine site. Bioassays indicated that dual enrichment by inorganic N and P led to maximum increases in phytoplankton biomass, but additional organics may promote the growth of potentially toxic phytoplankton, including dinoflagellates and cyanobacteria. Evaluating the impact of varying nutrient forms on phytoplankton dynamics is necessary in order to develop strategies to avoid changes in community structure and larger-scale changes in ecosystem health