Relationships between microbial water quality and environmental conditions in coastal recreational waters: the fylde coast, UK

This paper explores ways in which the analysis of microbial data from routine compliance monitoring, in combination with basic environmental data, can provide insight into the factors affecting faecal-indicator organism concentrations in coastal waters. In the case study presented, eight designated bathing waters on the Fylde coast are continuing to exhibit unreliable compliance with the Imperative standards for total coliform (TC) and faecal coliform (FC) concentrations specified in the EU Bathing Water Directive (76/160/EEC), despite significant reductions in geometric mean concentrations following recent major investment in the sewerage infrastructure. Faecal streptococci (FS) concentrations have remained high and have not been improved by the new sewerage schemes. The results suggest that, prior to the schemes, higher bacterial concentrations were strongly associated with rainfall; and sewage sources were important for TC and FC, but less important for FS, which may have been more strongly affected by diffuse catchment sources. In the post-schemes period, catchment sources appear to be of greater significance; rainfall remains as a significant, though less important, predictor; and tide height at time of sampling, together with variables such as sunshine and the proportion of onshore winds (which affect the survival and movement of bacteria that have already entered the coastal waters), assume greater significance. The approach used here provides a cost-effective management tool for the exploratory investigation of any monitoring point that is failing to meet recreational water quality standards.