Toxicological aspects associated with the ecology of Donax trunculus (Bivalvia, Mollusca) in a polluted environment

This study provides data on the ecology and toxicology observed in the popu lation of Donax trunculus, a sand dwelling mussel, in the shallow subtidal of Haifa Bay (Mediterranean Sea, Israel). The studied population of the mus sel forms a dominant fraction in a community of sand-dwelling molluscs in a zone located 5-25 m from the shoreline, and at depths of 20-120 cm, number ing up to 2000 per m(2). Samples of the mussel were collected from three si tes, located within 9 km of shore in Haifa Bay. These included a clean site (Akko), a site polluted by a chemical PVC-polymer industry (Frutarom), and a site polluted with oil and waste from the petrochemical industry (Qiryat Yam). Metal analysis indicated site-dependent variations in levels of cadm ium, lead, copper and mercury in the mussel soft tissues. Copper levels wer e similar in the bivalves collected from all the sites. Levels of mercury w ere significantly higher in specimens from the PVC-polluted site (Frutarom) while levels of cadmium were higher in Akko and Qiryat Yam compared to Fru tarom. Lead residues were found only in Donax from Akko. The residual conte nts of mercury, copper and cadmium were relatively high in the young and no ticeably low in Donax of medium body size. The main site of deposition of m etals was in the soft tissues of the bivalve, but bioaccumulation of metals was also found in the shells. A marked increase in permeability of gills a nd mantle to the fluorescent anionic dye fluorescein (FLU) was detected in Donax from Qiryat Yam and especially Frutarom, compared to the bivalves sam pled from Akko. Multiple foci of enhanced permeability (multiple fluorescen t spots) were detected in all the individuals sampled from Frutarom but non e in the bivalve samples from Akko. Lysosomal accumulation of the metachrom atic fluorescent cationic probe, acridine orange - (AO), was significantly decreased in the tissues of D. trunculus from polluted sites, especially po lluted by the PVC factory. This decrease correlated with lysosomal enlargem ent and the formation of secondary lysosomes. D. trunculus appears to posse ss the most effective biochemical and physiological defense mechanisms enab ling it to survive in habitats of polluted shallow waters, where other sand dwelling mollusc species were absent or found only in waters deeper then 2 .5 m. (C) 1999 Elsevier Science B.V. All rights reserved.