An Evaluation of Bacterial Source Tracking of Faecal Bathing Water Pollution in the Kingsbridge Estuary, UK

This study aims to monitor the quality of marine bathing water and associated freshwater, in and out of the bathing season, and to evaluate bacterial source tracking using Polymerase Chain Reaction (PCR) to recognize human or animal sources of the contamination. Sediments were also monitored as a potential reservoir of indicator bacteria. The marine bathing water samples met with EU standards directives 2006/7/EC but increased significantly out of the season.

PCR was applied to detect the Bacteroides 16S rDNA gene in bathing water and sediment samples by using primers HF183F, CF128F, HoF597F, PF163F and Bac32F coupled with Bac708R primer, to successfully detect human, cow, horse, pig and general Bacteroides markers respectively. This host-specific PCR showed Bacteroides marker from a human origin in the sediment of stream, also cow Bacteroides marker appeared positive in the stream water and sediment and the beach sediment. All samples displayed positive results with general Bacteroides marker, whereas no horse markers and pig markers were detected in them. Thus whilst the bathing water remained excellent with no human markers detected on the beach, sediments upstream did indicate human faecal contamination which could act as a reservoir for bacterial pollution which may be released under certain weather conditions. The positive cow marker CF128F in water and sediment of the stream indicates that FIB are primarily due to cow faecal contamination at this site. PCR-based tracking has thus helped our knowledge of this situation; however, the persistence of these markers over time is yet to be investigated.