Mussels as biological indicators of pollution

Mussels have been extensively utilized in the past as a biological indicator of pollution in monitoring programs. The reason for this choice is that the mussel is a sessile, filter-feeding organism, able to accumulate within its tissues many of the contaminants (pesticides, hydrocarbons, metals, etc.) present in sea water. In addition, mussels show a wide geographical distribution, thus permitting the survey of extensive coastal areas. The contaminants accumulated in the tissues of mussels may cause a "stress syndrome" with alteration to their physiology. To quantify this stress, the utilization of "stress indices" has been proposed. Parameters are identified whose variations may be related to the general physiological status of mussels (general stress indices) and others that may indicate the effects exerted by particular classes of contaminants (specific stress indices). Taken together, the variations of these parameters at molecular, cellular or organism level may provide information on the stress syndrome of the animals and on its repercussions at the population level. The results of a recent workshop in which this strategy of environmental control was applied have confirmed the validity of this approach in the assessment of the degree of coastal contamination and in the determination of the biological effects of pollutants.