Study of microbiological pollution of a pleasure boat harbour using mussels as bioindicators

The bacteriological analysis of samples of the mussel Mytilus galloprovincialis, used as a biological indicator, has shown a microbiological pollution of Saint Gervais harbour in the gulf of Fos. Experiments were carried out with the use of classical tests (faecal coliforms, faecal streptococci, salmonellae) taking into account the study of the environmental factors able to modify the physiological activity of mussels (wind, rain, temperature, salinity, turbidity). The highest values, which sometimes widely exceeded the French and European guidelines regarding edible shellfish, were revealed in summer but also during the weekends of Whitsun and All Saints' day, times when boat activity was greatest. The absence of storm and wastewater outlets and the stability of the meteorological conditions at the times of sampling show that this pollution is directly connected to the pleasure boats, the toilets of which flow into the harbour in most cases. The present study of this small harbour demonstrates the importance of boats being fitted with toilets to prevent the flow of faecal material into the ambient waters.