title: Identifying avian sources of faecal contamination using sterol analysis.
abstract: Discrimination of the source of faecal pollution in water bodies is an important step in the assessment and mitigation of public health risk. One tool for faecal source tracking is the analysis of faecal sterols which are present in faeces of animals in a range of distinctive ratios. Published ratios are able to discriminate between human and herbivore mammal faecal inputs but are of less value for identifying pollution from wildfowl, which can be a common cause of elevated bacterial indicators in rivers and streams. In this study, the sterol profiles of 50 avian-derived faecal specimens (seagulls, ducks and chickens) were examined alongside those of 57 ruminant faeces and previously published sterol profiles of human wastewater, chicken effluent and animal meatwork effluent. Two novel sterol ratios were identified as specific to avian faecal scats, which, when incorporated into a decision tree with human and herbivore mammal indicative ratios, were able to identify sterols from avian-polluted waterways. For samples where the sterol profile was not consistent with herbivore mammal or human pollution, avian pollution is indicated when the ratio of 24-ethylcholestanol/(24-ethylcholestanol + 24-ethylcoprostanol + 24-ethylepicoprostanol) is ≥0.4 (avian ratio 1) and the ratio of cholestanol/(cholestanol + coprostanol + epicoprostanol) is ≥0.5 (avian ratio 2). When avian pollution is indicated, further confirmation by targeted PCR specific markers can be employed if greater confidence in the pollution source is required. A 66% concordance between sterol ratios and current avian PCR markers was achieved when 56 water samples from polluted waterways were analysed.
authors.affiliation: Institute of Environmental Science and Research Limited, Christchurch Science Centre, PO Box 29-181, Christchurch, New Zealand. megan.devane@esr.cri.nz.
authors.forename: Megan L
authors.initials: ML
authors.lastname: Devane
authors.affiliation: Institute of Environmental Science and Research Limited, Christchurch Science Centre, PO Box 29-181, Christchurch, New Zealand.
authors.forename: David
authors.initials: D
authors.lastname: Wood
authors.affiliation: Institute of Environmental Science and Research Limited, Christchurch Science Centre, PO Box 29-181, Christchurch, New Zealand.
authors.forename: Andrew
authors.initials: A
authors.lastname: Chappell
authors.affiliation: Institute of Environmental Science and Research Limited, Christchurch Science Centre, PO Box 29-181, Christchurch, New Zealand.
authors.forename: Beth
authors.initials: B
authors.lastname: Robson
authors.affiliation: Waterways Centre for Freshwater Management, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.
authors.forename: Jenny
authors.initials: J
authors.lastname: Webster-Brown
authors.affiliation: Institute of Environmental Science and Research Limited, Christchurch Science Centre, PO Box 29-181, Christchurch, New Zealand.
authors.forename: Brent J
authors.initials: BJ
authors.lastname: Gilpin
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000032:analysis; D001717:Birds; D004083:Cholestanol / Q000032:analysis; D004247:DNA / Q000032:analysis; D003663:Decision Trees; D004784:Environmental Monitoring / Q000379:methods*; D005243:Feces / Q000737:chemistry*; D005618:Fresh Water / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D016133:Polymerase Chain Reaction; D013261:Sterols / Q000032:analysis*; D014876:Water Pollution / Q000032:analysis*
chemical_list: D015415:Biomarkers; D013261:Sterols; D004083:Cholestanol; D004247:DNA
keywords: 24-Ethylcholestanol; Avian; Cholestanol; Decision tree; Sterols; Water pollution