Effect of environmental factors on the distribution of different bacterial populations in a shellfish farming area of the lagoon of Bizerte (Northern Tunisia)
The present study aimed to assess the influence of abiotic parameters on the distribution of various viable bacterial populations in the most productive mussel farming area in the Bizerte Lagoon (Northern Tunisia). A monitoring survey was carried out over one year (September 2004 ‐ August 2005), within all the farming tables at the station. Bacterial enumerations of total coliforms (CT), fecal enterococci (EF), Vibrionaceae (VB) and cultivable heterotrophic bacteria (BHC) were carried out for surface water, mussels (Mytilus galloprovincialis) and sediments. These bacterial counts were correlated with water temperature, dissolved oxygen, salinity, pH, rainfall and sunshine, which were periodically measured at all points within the sampling area. The survey of the bacteriological parameters revealed high bacterial counts during the whole monitoring period, especially in the mussels and sediments, as well as seasonal variability. Statistical analyses revealed positive correlation between the loads of fecal pollutants and rainfall during the winter period, and between the loads of Vibrionaceae and salinity and temperature during the summer period. These results highlight the negative anthropogenic bacterial effect within the mussel farming areas: sewage discharges in winter, and the growth of autochthonous pathogenic bacteria during the summer period, have a considerable influence on the mussel culture in the Bizerte Lagoon.