Interaction of mineral elements in sea water and shell of oysters (Crassostrea virginica (Gmelin)) cultured in controlled and natural systems

The interaction is reported of selected chemical elements (cadmium, calcium, copper, iron, magnesium, manganese, strontium, and zinc) in cultured sea water, with soft tissues, prismatic calcite of the right valve, and foliated calcite of right and left valves of genetically similar American oysters, Crassostrea virginica (Gmelin) grown in a natural habitat and in two environmentally controlled experimental systems (flow-through and recycle). The addition of trace elements as algal nutrients in ambient sea water was reflected in higher concentrations of trace metals in shells and soft tissues of oysters grown in experimental systems. Calcium was relatively uniformly distributed in major regions of valves from the three habitats, even though its concentration fluctuated widely in sea water in experimental systems. Magnesium and strontium were most concentrated in valves of oysters grown in the recycle system (magnesium in the prismatic layer of the shell and strontium in the foliated calcite). Iron was uniformly distributed. Cadmium, copper, manganese, and zinc were most concentrated in the prismatic calcite of valves from the flow-through system. In soft tissues, calcium was more concentrated in oysters from experimental systems than in those from the natural habitat. Manganese was about equally distributed in soft tissues from the three habitats, whereas copper and iron were more concentrated in soft tissues in experimental systems than in the natural habitat, and were many times more concentrated in soft tissues than in valves from all three habitats. As concentrations of magnesium, strontium, mangenese, zinc, and cadmium increased in valves in experimental systems, pigmentation of valves decreased. The study confirmed the capacity of oysters to concentrate several elements in their valves as concentration of these elements increased in ambient sea water and disclosed the heterogeneous distribution of these elements in major regions of the valves.