Coherence among different microbial source tracking markers in a small agricultural stream with and without livestock exclusion practices.

Wilkes, G.A., Brassard, J., Edge, T.A., Gannon, V.P.J., Jokinen, C.C., Jones, T.H., Marti, R., Neumann, N.F., Ruecker, N.J., Sunohara, M., Topp, E., and Lapen, D.R. (2013). "Coherence among different microbial source tracking markers in a small agricultural stream with and without livestock exclusion practices.", Applied and Environmental Microbiology, 79(20), pp. 6207-6219. doi : 10.1128/AEM.01626-13  Access to full text

Abstract

Over 1400 bi-weekly water samples were collected over 6 years from an intermittent stream protected from pasturing cattle, and unprotected from cattle. Host specific Bacteroidales markers, Crytosporidium species/genotypes, viruses and coliphages associated with humans or animals, and bacterial zoonotic pathogens were monitored. Ruminant Bacteroidales markers did not increase downstream of the restricted pasture, relative to upstream monitoring sites; whereas the ruminant Bacteroidales marker increased significantly in the unrestricted cattle access reach. Human Bacteroidales markers significantly increased downstream of homes where septic issues were documented. Wildlife Bacteroidales markers were detected downstream of the protected pasture where stream and riparian habitat was protected, but detections decreased after the unrestricted pasture. A great number of human virus detections were shown to increase downstream of homes, and similar trends were observed for the human Bacteroidales marker. There was considerable interplay among biomarkers with stream flow, season, and localized upstream land uses. There were no, to very weak, associations with Bacteroidales markers and bacterial, viral, and parasitic pathogens. Overall, discrete sample by sample coherence among the different MST markers that expressed a similar microbial source was minimal, but spatial trends were physically meaningful in terms of land use (e.g., beneficial management practice) effects on sources of fecal pollution.

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