Microbiological quality of bathing waters versus sanitary regulation and beach users practices. A case study in Marseille

The Mediterranean shoreline receive a large number of tourists motivated by the pleasant and sunny beaches. The attractiveness and attendance to these areas are closely linked to the ability to swim. The quality of bathing water is governed by the standards set by the EC Bathing Water Directive (2006/7/EC). These standards consider fecal indicator bacteria (E. coli and intestinal enterococci) to assess the microbiological water quality. Bacteria abundance in water is controlled during the summer season under the responsibility of the Regional Health Agencies (ARS), with a frequency that varies according to the beaches. An interdisciplinary approach of bathing water quality carried out between 2016 and 2018 on three urban beaches in the city of Marseille (France), involving geographers, microbiologists and hydrologists, made it possible to address three issues: • do the operating sampling strategy developed for monitoring the health quality of bathing water lead to an appropriate assessment of the quality of bathing water on a day-to-day basis? • can bathing water quality be related to the number and behaviours of beach users? • is the public appreciation of the quality of urban beaches on the Marseilles coast agree the actual water quality? The methodology used consisted in sampling and analyzing bathing waters on an hourly basis (8am-8pm over several consecutive days), jointly with quantification of beach attendance and detailed structured user questionnaire surveys. The obtained results make it possible to assess and compare the hourly and daily variability of the microbiological quality of bathing waters with the number of users and their assessment of the quality of the beaches, as well as their management.