USING TESTATE AMOEBAE AS BIOINDICATORS OF WATER QUALITY AND ECOSYSTEM HEALTH IN THE STONES RIVER WATERSHED IN MURFREESBORO, TN

Tennessee is one of the fastest growing states in the nation. Increasing populations can lead to issues with managing waste. Middle Point Landfill in Murfreesboro is an 808-acre facility that accepts 3,700 tons of waste a day from 34 counties across Tennessee. In 2022, the city of Murfreesboro filed suit in federal court against the owners of the landfill alleging that toxic substances had been released into the East Fork of the Stones River by the landfill. This claim has been denied by the owners of the Middle Point Landfill, who have blamed the adjacent smaller Rutherford County Landfill. In this project, we will analyze ecosystem health in the Stones River watershed by analyzing the populations of testate amoebae. These microscopic, unicellular protozoans are found in sediment from freshwater localities, produce a mineralized shell, and have been shown in numerous previous studies to respond to environmental changes. They are considered to be bioindicators that can serve as a proxy for ecosystem health.

Several other issues are affecting the water quality within the watershed, including urban and residential runoff and infestations of invasive aquatic plant species, including parrot-feather or Myriophyllum aquaticum; water primrose or Ludwigia sp.; and alligator weed or Alternanthera philoxeroides. A study within the waterbodies within the Stones River watershed in 2017 showed eutrophication and hypoxia with high ammonia and chlorine levels in the water. This project focuses upon eight locations within the watershed, including locations up- and downstream of the Middle Point Landfill on the East Fork of the Stones River.

Initial results from the East Fork of the Stones River show that testate amoebae were absent from the sample immediately downstream from the landfill. Further downstream we found both opportunistic species, such as Centropyxis aculeata, and species found in areas with high levels of organic content, such as Difflugia oblonga. This population is similar to the population found in a sample from the West Fork. Samples from the wetlands infested with invasive aquatic species show high abundances of Difflugia, indicating higher organic content. Final results will include statistical analyses of populations from each location.