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Combining Watershed Variables with PCR-based Methods for Better Characterization and Management of Fecal Pollution in Small Streams
Citation:
PEED, L., C. T. NIETCH, C. A. KELTY, K. WHITE-FALLON, J. C. BLANNON, M. C. MECKES, M. SIVAGANESAN, R. A. HAUGLAND, O. C. SHANKS, AND T. Mooney. Combining Watershed Variables with PCR-based Methods for Better Characterization and Management of Fecal Pollution in Small Streams. Presented at ISES 2009, Minneapolis, MN, November 04, 2009.
Impact/Purpose:
To inform the public.
Description:
Ability to distinguish between human and animal fecal pollution is important for risk assessment and watershed management, particularly in bodies of water used as sources of drinking water or for recreation. PCR-based methods were used to determine the source of fecal pollution and to characterize the relationship between fecal pollution and land use, surface water nutrients, precipitation, and other in-stream indicators of water quality. Stream water samples (n = 193) were collected monthly over a two year period from ten channels draining subwatersheds with different land use intensities. The sampling effort was part of a multidisciplinary program designed to characterize and manage water quality in the 320,000 acre East Fork Watershed of Southwestern Ohio. PCR-based methods included 14 PCR and quantitative real-time PCR (qPCR) assays that detect enterococci, E. coli, Bacteroidales as well as human- and bovine-associated genetic markers. Human-specific qPCR assays tested positive for 20-45% of subwatershed samples and >94% of samples were positive with general fecal indicator assays suggesting routine occurrence of fecal pollution in all streams. An analysis of variance indicated that when there was > 0.25 inches of rainfall within 24 hours (wet season) prior to sampling there was a significant increase in genetic marker concentrations for all qPCR assays (p < 0.05). Simple linear regression analysis indicated a significant effect (p < 0.05) between all human-associated genetic marker concentrations and septic tank density for wet season samples suggesting that failing septic systems are a major source of pollution after rain events. Our data analyses demonstrate that combining PCR-based measurements of fecal contamination with land use trends and water quality variables can provide a more complete understanding of microbial pollution, leading to more focused watershed management efforts.
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