E. coli bacteria

E. coli are bacteria found in the stomachs of warm blooded animals which find their way into streams through feces. E coli can cause intestinal and extra-intestinal infections and are often a marker for other bacteria that can cause disease. High E.coli counts can be attributed to a number of sources, including stock animals, human septic tanks or other wildlife native to the region in question.

1..Some seasonal variation can be seen in the presence of E.coli in the Nequasset Watershed. Specifically (as indicated during the months of September, October, and November on the graph), E.coli counts rise during the fall months (with colony counts ranging from 10 colonies/100ml to over 800 colonies/100ml) and then decline as soon as winter sets in (i.e., periods where no sampling site exceeded a count of more than 10 colonies/100ml) , remaining consistently low during most of December, and all of January, February, and March (a slight increase during the month of April indicates that with temperature increases producing melting snow, surface runoff can connect with new and old sources of E.coli). Given that E.coli is brought into the watershed sampling sites by surface runoff, the higher presence of the bacteria during the fall indicates that this water is indeed flowing freely into the sampling sites, whereas during the winter months, when the water is frozen, E.coli has fewer opportunities to be brought into the sampling sites.

Wetland area at Indian Road

2. Our findings also indicate higher levels of E.coli at two sampling sites (Nequasset Stream at Indian Road [842, 322 colonies/100ml on 9/27/07 and 10/4/07 respectively] and at the Meadow Road Tributary [462, 698 colonies/100ml on 9/27/07 and 10/4/07 respectively], the latter of which will be discussed in item #3) during the fall period mentioned above. To account for this, the geography of this particular area of the watershed must be taken into account. The sampling site at Indian Road lies directly below a drainage area for a large wetland area; thus, given the presence of various wildlife in the wetlands (including, for example, ducks, other waterfowl, beavers, etc), the E.coli presence in the water is much higher than it would be for an area not lying below a wetland area.

3. The tributary at Meadow Road falls in a similar area (below a wetland), taking in the water in which a higher presence of E.coli can be found, most likely due to both wildlife (similar to the sampling site at Indian Road) and the fact that a farm lies directly upstream. In addition, more widespread development near Meadow Road also likely contributes to the higher presence of E.coli, given urban factors that normally affect the bacterial presence in water (i.e., leaking septic tanks)