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Mussel ( Mytilus galloprovincialis (Lamarck, 1819)) is directly exposed to sea water contamination that elicits significant physiological and cellular response, although its extent mounted in aquaculture-reared in comparison to wild bivalve populations is scarcely known. Therefore, we have compared contamination biomarkers in mussels from reared (Marina farm) and wild, anthropogenically affected site (Vranjic Bay). While predictably, the levels of metals (Cu, Cd, Pb, Zn, Fe, and Hg) in whole bivalve tissues determined by atomic absorption spectrophotometry resulted in significantly higher concentrations in wild mussels, accompanied by elevated number of apoptotic cells in gills, the activity of multixenobiotic resistance defense mechanism (MXR), measured as the accumulation rate of model substrate rhodamine B (RB) gave contrasting results. The functional RB assay evidenced a lower MXR efflux activity in the gill tissue of wild mussels, indicating two possible scenarios that will need further focus: (1) persisting sea water pollution increased cell damage of bivalve gill cells and consequently led to leakage of the RB into cytoplasm and dysfunctional MXR efflux in wild mussels; or/and (2) a mixture of different toxic compounds present in Vranjic Bay sea water induced oversaturation of MXR efflux, inducing elevated accumulation of the dye. Consequently, it seems that an efficient physiological functioning of MXR in wild mussels is strongly hampered by existence of an unknown quantity of sea water pollutants that may endanger intrinsic organismal defense system and lead toward the enhancement of toxicity. [ABSTRACT FROM AUTHOR]

Caffeine, a biologically active drug with many known molecular targets, is recognized as a contaminant of marine systems. Although the concentrations of caffeine reported from aquatic systems are low (ng/l-μg/l), harmful ecological effects not detected by traditional toxicity tests could occur as a result of caffeine contamination. We used Hsp70, a molecular biomarker of cellular stress, to investigate the sub-lethal cellular toxicity of environmentally relevant concentrations of caffeine on the mussel Mytilus californianus, a dominant species in the rocky intertidal zone along the Oregon Coast. Hsp70 concentrations in the gill and mantle tissue of mussels exposed to 0.05, 0.2, and 0.5 μg/l of caffeine for 10, 20, and 30 days were compared to basal levels in control mussels. Hsp70 in the gill tissue of M. californianus had an initial attenuation of the stress protein followed by a significant up-regulation relative to controls in all but the 0.5 μg/l treatment. Hsp70 in the mantle tissue of mussels exposed to caffeine did not differ from control mussels. This study provides laboratory evidence that environmentally relevant concentrations of caffeine can exert an effect on M. californianus gill tissue at the molecular-level. [ABSTRACT FROM AUTHOR]