Investigation on the temporal variation and source tracking of faecal bacteria in a forest dominated watershed (Comox Lake), British Columbia, Canada.

Aims: The aims of this study were to investigate the temporal variation in Escherichia coli density and its sources at the drinking water intake of Comox Lake for a period of 3 years (2011-2013).

Methods And Results: Density of E. coli was assessed by standard membrane filtration method. Source tracking of E. coli were done by using BOX-A1R-based rep-PCR DNA fingerprinting method. Over the years, the mean E. coli density ranged from nondetectable to 9·8 CFU 100 ml(-1) . The density of E. coli in each of the years did not show any significant difference (P > 0·05); however, a comparatively higher density was observed during the fall. Wildlife was (64·28%, 153/238) identified as the major contributing source of E. coli, followed by human (18·06%, 43/238) and unknown sources (17·64%, 42/238). Although the sources were varied by year and season, over all, the predominant contributing sources were black bear, human, unknown, elk, horse and gull.

Conclusions: The findings of this investigation identified the multiple animal sources contributing faecal bacteria into the drinking water intake of Comox Lake and their varying temporal occurrence.

Significance And Impact Of The Study: The results of this study can reliably inform the authorities about the most vulnerable period (season) of faecal bacterial loading and their potential sources in the lake for improving risk assessment and pollution mitigation.