Influence of the Environmental Factors on Contamination of Mediterranean Mussels (Mytilus galloprovincialis)

Harvesting areas in Slovenia are monitored for contamination with E. coli as pollution indicator bacteria. According to contamination levels, areas are classified into A, B or C category. An A category means that there is less than 700 E. coli MPN/100 g of the shellfish flesh and intervalvular fluid. Mussels from the areas with the established A category are placed on the market directly, whereas shellfish from areas classified as B or C category undergo a depurating process. The aim of our research was to gain detailed insight into the contamination with E. coli as well as with some other microorganisms and heavy metals. We also took into account possible factors affecting the contamination of seawater and shellfish (e.g. marine currents, rainfall, tides). During a one-year period 34 samplings at three shellfish harvesting areas and one wild area were carried out (306 samples). Higher levels of contamination were observed in colder parts of the year (spring, winter) and at the time of heavy rainfalls. Correlation between E. coli number in mussels and enterococci in seawater was statistically significant. To ensure safety of the mussels it is therefore important to carry out increased number of samplings at critical periods of the year.