ASSESSMENT OF WATER QUALITY THROUGH THE STUDY OF THECAMOEBIAN POPULATIONS IN TODDS LAKE, RUTHERFORD COUNTY, TN

Water quality is a topic of global concern, thus it is important that we study organisms that lend insight to water quality. Our research focused on the analysis of thecamoebians, also known as testate amoebae, which are microscopic organisms that inhabit aquatic sediment. These thecamoebians were found in sediment samples taken from Todds Lake, an artificial reservoir in Rutherford County, Tennessee. Todds Lake is located in a residential subdivision and is crossed by a major four lane road. To assess the water quality of Todds Lake, sediment samples were taken from the lake bed by hand and by use of an Ekman Grab Sampler then washed through 500 𝜇m and 45 𝜇m sieves. The dominant species found in all samples was Centropyxis aculeata. In samples REU105 and REU114 Centropyxis aculeata “aculeata” was the most prevalent strain while in samples REU102 and REU111 Centropyxis aculeata “discoides” was the most prevalent strain. In REU102 the species Cyclopyxis kahli was also dominant. The thecamoebians were removed from samples under a binocular microscope, sorted, and counted by species. Percentages of centropyxids in samples varied from 50% in REU102 to 86% in REU105 and species richness, using Margalef’s richness index, varied from 1.47 in REU102 to 2.07 in REU111. Shannon Diversity Index (SDI) values were calculated for each sample and values ranged from 1.09 in REU108 to 1.76 in REU114. These values indicate that all samples are from moderate environments. Healthy environments tend to have SDI values above 2.5 and unhealthy environments tend to have values below 0.5. Sample REU114 had the highest SDI value and the second highest species richness. It was collected in the center of the lake further from the road than either REU102 or REU105 and possibly further from sources of pollution than the other samples. Centropyxids are opportunistic generalists that are better able to withstand stress within an environment than other thecamoebians and they were the dominant species in all samples. Cyclopyxis kahli is common in soils and could be indicative of soil erosion. It is found in REU102, the only sample taken from the section of Todds Lake located south of the road. The high number of centropyxids and the moderate SDI values show that the Todds Lake ecosystem is stressed, however further research is needed to determine the sources of stress.