USING RECENT THECAMOEBIAN ASSEMBLAGES TO DETERMINE WATER QUALITY OF TODDS LAKE, RUTHERFORD COUNTY, TENNESSEE

Todds Lake is an artificially dammed reservoir for the city of Murfreesboro in Tennessee. It is located in the Stones River watershed, is surrounded by urban development, and receives runoff from one of the fastest growing cities in the United States. As it is a relatively small lake it is an ideal location for undergraduate research projects and the study of thecamoebians, shelled microscopic invertebrates that have been used previously as pollution indicators, and is ideal for undergraduates as it requires no special equipment other than light microscopes. Two previous studies used thecamoebians to assess environmental change within the northern section of Todds Lake. This study examines the recent past and present quality of water contained in the southern portion of Todds Lake, which is separated from the northern section by a major roadway and is surrounded by fewer residential subdivisions. This study analyzes thecamoebian communities found in surface sediments and a core sample and compares them with communities collected from a retention pond located within four miles of Todds Lake. Very few thecamoebians were recovered from substrate sediment samples and most of the shells that were observed using light microscopy were not salvageable. The only species recovered from the surface sediment were members of the opportunistic species Centropyxis indicating a stressed environment. Analysis of the 2-3 cm interval of the core reveals centropyxids and small numbers of Difflugia. Similar species were recovered from the retention pond but species of Difflugia are more common in the retention pond than centropyxids. Data collected in our study suggests that the southern section of Todds Lake may be a stressed environment due to the low quantity of opportunistic species. Higher abundances of Difflugia are indicative of eutrophic environments and are seen in the northern section of Todds Lake and the retention pond, but not in the southern section of the lake.