Unraveling the Source of Fecal Contamination in Thornapple Lake
Location
Hager-Lubbers Exhibition Hall
Description
Purpose: Michigan’s recreational beaches are routinely monitored for E. coli. Elevated levels indicate that fecal matter contaminates the lake and, if levels exceed EGLE’s threshold for full body contact, the beach is closed. A contamination source must be identified before remediation can occur. Subject: We partnered with Barry-Eaton District Health Department to determine the source of frequent E. coli contamination of Thornapple Lake (Hastings, Michigan). Methods and Materials: We sampled sites from the lake and its tributaries weekly from May-August. Escherichia coli numbers were determined using Colilert and DNA was extracted from filtered water samples. Host-specific fecal bacteria (human (HF183 and HumM2) and cow (CowM2)) were quantified in the extracted DNA by qPCR along with E.coli (EC23S). Analyses: Most Probable Number (MPN) was determined by Colilert using manufacture provided tables. Results: We found that EC23S and HF183 were correlated when E. coli counts by Colilert were high. Our second human marker (HumM2) was far less sensitive in that it rarely occurred at levels that exceeded the lower limit of quantification (LLOQ) even when HF183 levels were high. Our cow marker (CowM2) rarely exceeded the LLOQ. Conclusions: Human fecal contamination contributes to the E. coli found in Thornapple lake. Our work shows that presence of a contamination source is much easier to prove than its absence since markers range by orders of magnitude in their sensitivity. Our work attests to the important role that molecular techniques can play in the field of environmental health when results are properly interpreted.
Unraveling the Source of Fecal Contamination in Thornapple Lake
Hager-Lubbers Exhibition Hall
Purpose: Michigan’s recreational beaches are routinely monitored for E. coli. Elevated levels indicate that fecal matter contaminates the lake and, if levels exceed EGLE’s threshold for full body contact, the beach is closed. A contamination source must be identified before remediation can occur. Subject: We partnered with Barry-Eaton District Health Department to determine the source of frequent E. coli contamination of Thornapple Lake (Hastings, Michigan). Methods and Materials: We sampled sites from the lake and its tributaries weekly from May-August. Escherichia coli numbers were determined using Colilert and DNA was extracted from filtered water samples. Host-specific fecal bacteria (human (HF183 and HumM2) and cow (CowM2)) were quantified in the extracted DNA by qPCR along with E.coli (EC23S). Analyses: Most Probable Number (MPN) was determined by Colilert using manufacture provided tables. Results: We found that EC23S and HF183 were correlated when E. coli counts by Colilert were high. Our second human marker (HumM2) was far less sensitive in that it rarely occurred at levels that exceeded the lower limit of quantification (LLOQ) even when HF183 levels were high. Our cow marker (CowM2) rarely exceeded the LLOQ. Conclusions: Human fecal contamination contributes to the E. coli found in Thornapple lake. Our work shows that presence of a contamination source is much easier to prove than its absence since markers range by orders of magnitude in their sensitivity. Our work attests to the important role that molecular techniques can play in the field of environmental health when results are properly interpreted.