Microbial Source Tracking in Two Southern Maine Watersheds

November 9, 2018

Each year, bacterial contamination forces the closure of hundreds of acres of clam flats in southern Maine. These are the same bacteria that can pose a health risk at popular swimming beaches. Fecal coliform and E. coli bacteria are used as indicators that other, more harmful, pathogens may be present in coastal waters. But since wildlife, domestic animals, and humans can all be sources of fecal coliform, it is difficult for managers to identify the exact source of the bacteria.

This project (view the entire MST site) employed a technique known as microbial tracking to identify the sources of bacteria found in water samples taken by volunteers. The project focused on two watersheds in southern Maine. In the Webhannet watershed, which is densely developed and located entirely within the town of Wells, 18 percent of contamination was found to be of human origin and nine percent was traced to pets. In contrast, only three percent of contamination was traced to humans in the undeveloped Little River watershed, which spans mostly wooded land in Wells and Kennebunk. Researchers were surprised, then, when 22 percent of bacteria were traced to pet waste (mostly cats). The results of the Microbial Source Tracking study are being used by scientists and municipalities to develop strategies to reduce levels of bacterial contamination that affect clam flats and swimming beaches.

Microbial Source Tracking Reports for the Webhannet and Merriland/Branch/Little River (MBLR) Watersheds

Press Release 10/18/2000: New Grant Awarded to Study Microbial Source Tracking in Two Southern Maine Watersheds