Source tracking of escherichia coli in a freshwater lake in Northwestern Ontario (Boulevard Lake, Thunder Bay)

Abstract

Escherichia coli is regularly used as a fecal indicator bacteria (FIB) in recreational waters but its persistence in the environment brings its use into doubt. A secondary FIB known as Bacteroides has been under a lot of research lately. Because Bacteroides can be measured with quantitative PCR (qPCR) techniques easily, this makes it an effective FIB to detect fecal contamination. Boulevard Lake in Thunder Bay, Ontario experiences instances of elevated levels of E. coli throughout the summer seasons. For the 2011 season the Bacteroides 16S rDNA markers were monitored and compared with the E. coli population. As both of these FIB are found in feces, influxes of fecal contamination would see increases in both populations. The planktonic E. coli population densities exceeded the Canadian Recreational Water Quality Guidelines of 2.30 log CFU 100ml-1 two times throughout the summer season. These were measured at 2.86 and 2.38 log CFU 100 ml-1 on July 21, 2011 and September 2, 2011, respectively. The Bacteroides biomarkers did have any significant increases during these peak periods of E. coli with p > 0.05. This would suggest that the increased levels of E. coli may not have been due to fecal contaminants. Further investigations with a microbial source tracking approach will provide insights to the potential source(s) of E. coli in Boulevard Lake. For both 2010 and 2011, the planktonic E. coli population at Boulevard Lake was monitored.