Determination of the Most Influential Factors in the Concentration of Bacteria in Coastal Waters

Abstract

Control of water quality of coastal waters is essential to ensure the safety of bathers. Therefore, the current legislation establishes maximum concentration levels of faecal bacteria, in particular Escherichia coli and intestinal Enterococci. After several studies, it is known that there are environmental and physical factors such as the level of urbanization of the beach, sediment type, rainfall, salinity and water temperature, which influence the concentration of these bacteria. However, there are many other factors, such as the morphology of the beach, its orientation relative to waves and the proximity of spills, that can affect the survival of these bacteria and therefore directly influence the water quality in the coastal zone. In this article, 270 beaches between the provinces of Valencia and Granada (Spain) were analysed. It was observed that the local factors that further affect the concentration of faecal bacteria in coastal water are the presence of meadows of Posidonia oceanica, the orientation of the beach with respect to the direction of the most common incident waves and the agricultural discharges in the sea.