Microbial indicators of faecal contamination in waters and sediments of beach bathing zones

This study presents the results obtained of the microbial characterization of waters and sediments of 18 coastal bathing zones of the south-western coast of the Iberian Peninsula. To make this characterization, two indicators of faecal contamination have been selected: faecal coliforms (FC) and Clostridium perfringens (CP). The results show that low concentrations of FC and CP in water not necessarily implies that their concentration in sediment and elutriates has to be low as well. The highest concentrations were found in locations close to the mouth of rivers, and in beaches of low energy and hence low water renewal, and high accumulation of fine sediments. The concentrations of FC were lower than those obtained for CP in most of the sampling locations. Although quality standards for bathing waters do not take the parameter CP into account, it has been demonstrated that it should be a good indicator of faecal contamination.