EFFECTS OF A RAPIDLY URBANIZING ENVIRONMENT ON WATER QUALITY: A CASE STUDY FROM MURFREESBORO, TN

Murfreesboro, Tennessee is one of the fastest growing cities in the state and was the location of a six week undergraduate research project focusing on water quality. Black Fox Spring (BFS), Murfree Spring (MS) and the associated wetlands (MSW), and Todds Lake (TL) are water bodies that are connected through a groundwater system and affected by urban and residential runoff and impacted by the invasive plant species, parrot-feather or Myriophyllum aquaticum.

During this research project water quality was tested in two ways. First, traditional water quality indicator tests were conducted. These parameters include pH, dissolved oxygen (DO), ammonia, chlorine, copper, hardness, iron, nitrate, nitrite, phosphate, temperature and total dissolved solids (TDS). The second approach was the use of bioindicators known as testate amoebae. These microscopic unicellular protozoans are found in freshwater localities, have a mineralized shell, and have been shown in many studies to be responsive to environmental changes.

Results indicate eutrophication conditions in BFS with a spike in ammonia values and testate amoebae assemblages dominated by the opportunistic species, Centropyxis aculeata, which is tolerant of poor water quality environments. Chlorine concentrations are higher than the EPA freshwater threshold in most sampled locations with a spike in MSW. The coefficient of variation is very high (144%) in MSW suggesting the input of chlorine into the wetlands by in situ point sources. This location also had the lowest DO values (4.3 ppm). Testate amoebae populations were low in MSW and dominated by Difflugia oblonga “tenuis,” a species often found in areas with high levels of organic content. Even though the wetlands are relatively shallow, the density of the invasive parrot-feather, in addition to a dam, is allowing almost no water flow and is contributing to the stagnation of the water. DO in TL (i.e. 9ppm) and MS (i.e. 6.7ppm) is in the healthy range for most samples, which is reflected in healthier populations of testate amoebae with higher diversities dominated by a range of species including Difflugia oblonga, Centropyxis acuelata and Mediolus corona.