Coherence among Different Microbial Source Tracking Markers in a Small Agricultural Stream with or without Livestock Exclusion Practices
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ABSTRACT
Over 1,400 water samples were collected biweekly over 6 years from an intermittent stream protected and unprotected from pasturing cattle. The samples were monitored for host-specific
Bacteroidales
markers,
Cryptosporidium
species/genotypes, viruses and coliphages associated with humans or animals, and bacterial zoonotic pathogens. Ruminant
Bacteroidales
markers did not increase within the restricted cattle access reach of the stream, 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 cattle exclusion practice where stream and riparian habitat was protected, but detections decreased after the unrestricted pasture, where the stream and riparian zone was unprotected from livestock. Detection of a large number of human viruses was 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 the cattle exclusion practices. 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 microbial source tracking 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.
