Variability, Seasonality, and Persistence of Fecal Coliform Bacteria in a Cold-Region, Urban Stream

摘要

Fecal coliform (FC) analyses were conducted on weekly water samples collected from a single watershed over a 2-year period in Anchorage, Alaska. Although peak FC concentrations (> 100 FC/100 mL) were observed primarily during the warmer months, lower FC levels (>20 FC/100 mL) could be observed throughout the year in the urbanized portion of the watershed. Median annual FC counts ranged from 3 FC/100 mL at an undeveloped site to 49 FC/100 mL at one of the urbanized sites. Median FC concentrations were found to be significantly higher in the summer compared to the winter at two locations directly downstream from a lake (p=0.011 and 0.029), but not at the sites upstream or distant from the lake. FC-discharge relationships indicated a significant negative correlation between FC concentration and discharge at two sites (p =0.030 and 0.035) and no significant correlation at the remaining three sites. In total, the results indicated that the water quality was impacted not only by peak　warm season loading events, but also by chronic low-level loading throughout the　year.