Source tracking faecal contamination in an urbanised and a rural waterway in the Nelson-Tasman region, New Zealand

Abstract

Microbial contamination of New Zealand's rivers, lakes and coastal waters can pose a risk to human health through both recreational contact and the consumption of contaminated shellfish. Microbial source tracking (MST) methods provide a means to identify potential contaminant sources, which can lead to high faecal indicator bacteria concentrations and elevated human health risk because of associated pathogens. Eight MST markers, including general, ruminant and human-associated Bacteroidales markers, a duck-associated E2 marker, a gull-associated Catellicoccus marimammalium marker and three additional human markers [Enterococcus faecium esp gene, Methanobrevibacter smithii nifH gene, and human polyomaviruses (HPyVs)] were tested for host specificity and sensitivity using an array of animal faecal samples of known origin and wastewater samples. The cross-reactivity identified for some of the markers, although limited, signals a need to validate overseas markers further in New Zealand before employing them in field studies. Application of MST markers on water samples collected from an urbanised section of the Maitai River (Nelson, New Zealand) identified the presence of faecal contamination originating from humans, ruminants and birds. Human faecal contamination was present in the lower section of the Matai River, and in stormwater drains entering the river, in association with elevated faecal coliform concentrations. Application of the markers to the rural Little Sydney Stream (near Motueka, Tasman district, NZ) identified faecal contamination derived from ruminants, which is consistent with the agricultural (pasture) use of the catchment. This study indicates that some of the markers developed overseas can be used effectively to track sources of microbial contamination in New Zealand watersheds.