Date of Award

Fall 12-10-2021

Document Type

Thesis

Degree Name

Master of Biological Science (MBioSci)

Department

Biology

First Advisor

Dr. Kalina Manoylov

Abstract

Aquatic habitats are frequently studied after a major water quality problem like the occurrence of an algal bloom. In this study, A proactive rather than a reactive response was considered, where the complexity of conditions conducive to uncontrolled cell growth were studied before a bloom took place by sampling regularly. This study aimed to monitor water quality by monthly sampling of algal communities for approximately one year. As the base of the aquatic food web, algae are a highly diverse group of organisms with varying sensitivity to physical and chemical changes in the environment. Four shallow sites were monitored at Lake Sinclair, GA once a month from November 2019 to October 2020, and four deep sites were monitored from May to August 2020 for conductivity, DO, pH and water temperature along with the algal community composition. Algal biomass was estimated in the field (analyzing algal mats attached to rocks or sand), and in the lab (analyzing composite samples). Algae that were alive at the time of collection were enumerated and identified to the lowest taxonomic unit. 192 samples were collected at midday and processed within hours. An ANOVA two-factor test was performed on the average chlorophyll-a concentration for each month and each site. The difference in average total chlorophyll-a among sites within habitat (shallow and deep) and through time were not significantly different. Habitat differences for dissolved oxygen (DO) were different for shallow and deep sites. Surface water temperature was not significantly different within the shallow and deep sites. DO was never below 4 mg/L, and chlorophyll-a production was higher in the shallow habitats. A total of 58 algal taxa are displayed in this study. Species richness was significantly higher in shallow sites where there was a maximum documentation of 78 species. There was taxonomic heterogeneity between the sites with toxigenic cyanobacteria documented in 28% of shallow sites and 22.9% of deep sites. The population density of toxigenic cyanobacteria was never above 5,000 cells/ml in any site, too low to potentially trigger production of cyanotoxins. However, in June, one of the triplicate samples taken at site 5, a deep site, had a toxigenic Aphanocapsa sp. 5 experience relative abundance at 29.41% of the total algal community. Chain forming diatoms dominated deep sites, but cyanobacteria were commonly documented in low abundance, represented by filamentous cyanobacteria Phormidium sp. The total biomass, measured as total chlorophyll-a, were significantly different between shallow and deep sites. Using the EPA developed tool for linking potential for toxic bloom to chlorophyll-a, concentrations higher than 39 µg/L were considered possible indicators for toxic algal bloom development. The highest chlorophyll-a concentration was documented only in shallow sites at 487.4 µg/L, but blooms were never recorded and cyanotoxins were not detected. Regional consideration of water mixing, siltation, and low light availability despite high temperatures potentially prevented blooms. Generally low nutrient conditions maintained a diverse algal community that did not develop into a monospecific growth.

Available for download on Tuesday, May 23, 2023

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