Date of Award

8-16-2024

Document Type

Open Access Dissertation

Department

Environmental Health Sciences

First Advisor

Geoffrey Scott

Second Advisor

James Pinckney

Abstract

Impacts from anthropogenic activities and climate change are significantly altering nitrogen (N) cycling processes and biological productivity along the freshwater to marine continuum, and the acceleration rate of excessive N and phosphorus (P) concentrations entering aquatic environments is unprecedented. As a result, nutrient pollution is contributing to the increasing magnitude and duration of cyanobacterial harmful algal blooms (cHABs), oxygen (O2) depletion, loss of biodiversity, and impacts to human and ecosystem health. Lake Wateree, South Carolina (SC) is a freshwater drinking and contact recreational water resource with elevated symptoms of eutrophication, including the increasing prevalence of the N2 fixing benthic cyanobacterium Microseira wollei (M. wollei) (formerly Lyngbya wollei).

To understand the environmental factors regulating M. wollei biomass in Lake Wateree, a series of nutrient enrichment bioassays with M. wollei incubations were conducted during the growing season to determine productivity rates and the specific roles and drivers of N and/or P on phytoplankton growth from five sites, and concentrations of the Lyngbya wollei toxins (LWTs) 1, 4, 5, and 6 were determined for each of the bioassays across nutrient treatments and stations. A statistical trend analysis of the historical ambient water quality and nutrient dataset collected by the citizen-scientist organization Lake Wateree Water Watch was conducted to identify spatio-temporal changes in the relationships between temperature, biologically-mediated water column response variables (dissolved oxygen, pH, and turbidity) and nutrients (N and P) to determine any correlations leading to the establishment and increasing magnitude of M. wollei blooms in the lake.

Results from the sequencing and amplification of 16S rRNA data confirmed the identity of M. wollei as the dominant cyanobacteria in Lake Wateree. M. wollei mat primary productivity was not limited by N and/or P in the bioassays conducted using dry weight biomass as an estimate for phytoplankton growth in Lake Wateree during this study, which does not support our hypothesis that the lake is limited by P or N and P. However, a strong seasonality of phytoplankton growth was evident during this experiment, and growth was significantly different between stations. Though there were no significant statistical differences between LWT concentrations and nutrient additions, significant differences between toxin concentrations and station in the current study are consistent with previous investigations of M. wollei in Lake Wateree.

Increasing temperatures, anthropogenic nutrient loading, and climate change will likely continue to contribute to the prevalence, magnitude, and toxicity of cyanobacterial blooms in aquatic ecosystems worldwide, and further assessments in the Catawba-Wateree River Basin and Lake Wateree are needed to identify the causes of increasing N concentrations and determine the point and non-point sources of N and P loading. The control of both N and P in Lake Wateree and upstream will be a significant strategy in reducing the symptoms of cultural eutrophication and preventing potential harmful impacts on human and ecosystem health.

Rights

© 2024, Kara Clyburn

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