Abstract
Water resources situated in areas with underlying karst geology are particularly vulnerable to fecal pollution. In such vulnerable systems, microbial source tracking (MST) methods are useful tools to elucidate the pathways of both animal and human fecal pollution, leading to more accurate water use risk assessments. Here, we describe the application of a MST toolbox using both culture-dependent bacteriophage and molecular-dependent 16S rRNA assays at spring and well sites in the karstic St Imier Valley, Switzerland. Culture-dependent and molecular-dependent marker performance varied significantly, with the 16S rRNA assays displaying greater sensitivity than their phage counterpart; HF183 was the best performing human wastewater-associated marker while Rum2Bac was the best performing ruminant marker. Differences were observed in pollution regimes between the well and spring sampling sites, with the spring water being more degraded than the well site. Our results inform the choice of marker selection for MST studies and highlight differences in microbial water quality between well and spring karst sites.
Highlights
Karst areas are an important source of drinking water throughout the world, with Switzerland drawing 80% of its drinking water from groundwater aquifers (Tripet )
Contamination of important drinking water resources by fecal pollution may lead to outbreaks of illness and economic degradation (Beaudeau et al ), with human fecal pollution representing a greater risk to water users than animal fecal pollution (Soller et al )
The aims of this paper are: (i) to compare the sensitivity of culture- and molecular-dependent Microbial source tracking (MST) indicators in two highly vulnerable karst catchments; and (ii) to trial 16S rRNA Bacteroidales indicators not previously used in Switzerland
Summary
Karst areas are an important source of drinking water throughout the world, with Switzerland drawing 80% of its drinking water from groundwater aquifers (Tripet ). Sinkholes, and other conduits which are characteristic of karst systems, facilitate the rapid movement of water from the terrestrial surface to receiving subterranean waterbodies, with rainfall-driven influx of microbial pollution a particular problem (Pronk et al ; Sinreich et al ; Diston et al ). This rainfall-driven overland flow may transport a range of human and animal pollutants to water resources in karst systems and as karst systems have short water retention times, in the order of hours as opposed. Microbial source tracking (MST) techniques are powerful tools, able to identify the sources of pollution in catchments
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