Date of Award

Spring 2021

Document Type

Open Access Thesis

Department

Marine Science

First Advisor

James L. Pinckney

Abstract

Increased urban and suburban population growth along the South Carolina (SC) coast has led to a rise in impervious surfaces, altering the course of stormwater runoff events. The construction of stormwater detention ponds (SDPs) is one of the many ways to best mitigate the flow of this water. In their function as natural pollutant traps, SDPs often contain increased levels of nutrients (nitrogen, N and phosphorus, P), which can lead to eutrophication. Under these high eutrophic conditions, primary production is overstimulated, and the formation of phytoplankton blooms, including harmful algal blooms (HABs) can occur. In recent decades, the forms of nitrogen (N) exported to coastal waters have changed, with more than half of all N fertilizers being urea-based. Research has also shown species-specific differences to various concentrations and forms of fixed N. More specifically, that cyanobacteria seem to thrive under higher concentrations of ammonium and urea. Furthermore, the photophysiology of freshwater phytoplankton has been studied to assess nutrient stress, lipid content, effects of UV radiation, and bloom dynamics, with less research on specific photo-physiological parameters in response to nutrients. However, there is a limited number of studies that has utilized Pulse Amplitude Modulated fluorometry to assess the photosynthetic efficiency and photophysiology of freshwater, phytoplankton communities in the North Inlet-Winyah Bay region.This proposed work aimed to examine the seasonal variability and photophysiology of phytoplankton communities in a one SDP over a short-term period in response to urea. These effects were tested using nutrient addition bioassays under a 72 h incubation conducted every 14-days. Phytoplankton community composition varied throughout the season, coinciding with changes in nutrient concentration. Cyanobacteria made up a small percentage (<30%) of the total phytoplankton community and it was concluded that they exhibited an insignificant, and weak response to urea additions. Urea additions also did not significantly increase the photophysiology of this phytoplankton community, except for the photosynthetic efficiency, Fv/Fm.

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