Date of Award
Master of Science (MS)
Dr. Kalina Manoylov
Dr. Christine Mutiti
Dr. Dave Bachoon
Streams play vital roles to surrounding communities and provide essential ecosystem services. The protection of streams is important, legally protected under the Clean Water Act (CWA) and can be monitored through the continuous analyses of biological data, like algal or other aquatic communities. Diatoms are a group of algae characterized by rigid glass cell walls and ubiquitous distribution. They are typically identified using the morphological species concept and an ever-varying range of sizes may pose challenges in the identification process. However, when identified and applied correctly, diatoms are robust bioindicators. This research identifies and analyzes low-impact sites across the Southeastern United States in attempts to identify reference sites. Three study sites within two different projects were analyzed: Tobler Creek, a recovering agricultural stream on the site of Andalusia Farm; Upper Three Runs Creek (UTRC), a reference site protected by the Department of Energy (DOE); and Murder Creek, a low-impact stream located that has been continuously monitored within the Oconee National Forest. Given a 31- year recovery period (2011), Tobler Creek did not meet nutrient reference criteria but did with an additional 11-year recovery (2022). From 2011 to 2022, Tobler Creek was found to display positive ecological values, such as species richness and diversity, in response to recovery. However, degradation was still signaled from diatom metrics, detecting high percentage of sediment tolerant taxa dominating communities. Gomphonema parvulum, a taxon traditionally thought to be tolerant of high nutrients, was in high abundance in 2011 and low in 2022. Analyses of Southeastern low-impact streams found G. parvulum still dominating UTRC in 2018, a reference site. This opens new questions about adaptations, ecological preferences, and life history of this taxon. Morphological responses were assessed across the Southeastern United States, and found that in UTRC, G. parvulum had a significant reduction in frustule sizes from 1956 to 2018, at the population level. However, in Tobler Creek, frustule lengths significantly varied monthly whereas there was no significant difference from 2011 to 2022. When cultured, frustules had significantly varied morphological responses from populations sampled from natural environments. Monocultures provide evidence that environmental conditions influence diatom morphology to some extent, as well as rates of sexual and asexual reproduction, and evolution of population morphologies of G. parvulum in UTRC is detected. Tobler Creek can serve as a model for recovery of abiotic and biotic properties in degraded streams whereas G. parvulum populations in UTRC is a case-study for population responses of this ubiquitous taxon to environmental conditions.
Brown, Sydney, "Community and Population Dynamics of Diatoms in Recovering Agricultural Stream and Ubiquitous Taxon in Low-Impact Sites Across Southeastern United States" (2023). Biology Theses. 29.
Available for download on Monday, May 04, 2026