Seasonal Variability of Nutrient Limitation and Impacts on Phytoplankton Community Composition in the Albemarle Sound (2023)
Undergraduate: Maxfield Palmer
Faculty Advisor: Nathan Hall
Department: Earth, Marine, and Environmental Sciences
Nutrient input into fresh and brackish water systems induces phytoplankton growth. Cyanobacteria, a harmful algal bloom-forming phytoplankton is influenced by nitrate and phosphate input into watersheds. Harmful algal blooms are formed through rapid growth of a phytoplankton species and can cause a stark decrease in water quality of the area surrounding the bloom through release of cyanotoxins as well as starving the ecosystem of oxygen. Permits for agricultural runoff and industrial wastewater have waste limits on phosphate and ammonium but not nitrate, a common nutrient used in phytoplankton growth. During 3 different seasons, a series of bioassays were conducted to determine whether nitrate, phosphate, or both nutrients were limiting to the growth of the cyanobacteria along with other common phytoplankton taxa in the region. High pressure liquid chromatography (HPLC) was used to analyze pigment composition of collected and treated water samples. CHEMTAX, a program used to determine percent of total biomass each phytoplankton taxa composes, was used on HPLC outputs and results were analyzed for significance using a one-way ANOVA followed by Tukey-HSD tests for significant results. Bioassays showed that in most sites, limitation is being caused by nitrate in the water or a combination of nitrate and phosphate, leading to conclusions being drawn regarding waste permits needing to include limits on nitrate input into watersheds to avoid harmful water quality impacts in the Albemarle Sound.
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