Does Rainfall Affect the Amount of Coliform in Janes Creek?

Overview

Objectives/Goals My objective was to learn if rain effected the amount of coliform bacteria in Janes Creek. Methods/Materials Water samples were taken from three different sites along Janes Creek before rainfall. Samples were put through Presumptive and Confirmed Tests to determine the Most Probable Number of coliform per 100 ml of water (MPN/100 ml) and to identify the type of coliform. These steps were repeated after it rained one inch in 48 hours. Results There was a huge increase in coliform after it rained. Before rain, Site 1 had an MPN/100 ml of 240, Site 2 had an MPN of about 240. Site 3 hand an MPN of 23. After rain, Site 1 had and MPN of more than 4,400 and the bacteria was all E. coli. Site 2 had an MPN of more than 2,400 and less than 11,000. Site 3 had an MPN of more than 2400 and less than 11,000. The bacteria in the medium from Site 3 produces less gas and less cloudiness than Site 3, leading me to think Site 2 had more coliform than Site 3. Conclusions/Discussion The location and surrounding geography of each site were the main factors in the amount of increase and type of coliform present. Site 1 had a cow pasture right next to it leading to the large increase in E. coli from fecal contamination. Site 2 was not located next to any cow pastures so all the run-off that ran into the stream only contained sediment leading to the increase in E. aerogenes. Site 3 was also not located near any cow pastures and is below a logging area leading to a lot of sediment in the creek and a large increase in E. aerogenes. If I were to do this experiment again I would order or make my own media to have more tubes and plates so I could repeat my experiment.

Competition history

• CSEF 2002 Environmental Science (Junior Division Only) · Entry J0911

Resources

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