Investigating Diatom Community Dynamics in Tobler Creek: A Recovering Agricultural Stream on Milledgeville’s Beloved Andalusia Farm

Sydney Brown, Georgia College & State University


Protecting the biological and ecological integrity is one of the major goals of the Clean Water Act. Agricultural processes can degrade stream ecosystem health by introducing nutrients, causing tolerant taxa to proliferate and outcompete sensitive taxa. Reference streams serve as comparisons to streams with questionable ecological status, with reference criteria being set based off of the 25th percentile of streams per ecoregion. Middle Georgia falls within region IV and ecoregion IX, with criteria set for total phosphorus and total nitrogen as 0.037 mg/L and 0.69 mg/L, respectively. Diatoms, a group of algae with cell walls composed of glass, serve as sensitive bioindicators which respond to varying environmental conditions. In this study, our study site is Tobler Creek, on the site of Andalusia Farm. Andalusia Farm served as a 41- hectares cotton plantation to cattle farm to hay farm and finally was donated as a museum in 1980. In 2022, it was declared a National Historic Landmark by the National Parks Services. Based on water quality monitoring in 2011, Tobler Creek did not meet reference criteria for nutrients, but did in 2022. Diatom community metrics showed significant increase in water quality in response to nutrient recovery. Additionally, diatom-specific metrics indicated increase of tolerant taxa to degradation driven by sedimentation. While limiting nutrients can improve trophic status of a stream, other factors like soil erosion can negatively impact aquatic ecosystems.