DEVELOPMENTAL EFFECTS OF BARIUM EXPOSURE IN A MARINE BIVALVE (MYTILUS-CALIFORNIANUS)

Previous reports indicated that barium (Ba) and/or strontium (Sr) were primarily responsible for the toxicity of a southern California produ ced water to developing marine embryos; To further investigate toxicit y of Ba and Sr in seawater, mussel embryos (Mytilus californianus) wer e subjected to static exposures of barium acetate and strontium chlori de from fertilization through veliger formation. Only Ba exhibited bio activity at environmentally relevant levels. Adverse effects occurred between 200 and 900 mu g/L (ppb); higher concentrations were associate d with decreased toxicity and apparent precipitation of Ba salts from seawater. Nominal Ba exposure concentrations between 100 and 900 mu g/ L yielded measured concentrations of 100 to 550 mu g/L soluble Ba when analyzed by inductively coupled argon plasma emission spectroscopy. A dverse developmental effects included abnormal shell calcification and embryo morphology. Exposure of embryos to Ba in stage-specific experi ments revealed that developmental stages were differentially affected, though they exhibited similar abnormalities. Gastrulae were the most sensitive, while blastula and trochophore larvae were less so. Adverse effects in embryos exposed during the gastrula stage were not reversi ble despite washing and return to clean seawater. These findings are a mong the first to demonstrate that low concentrations of soluble Ba in seawater can be toxic and are of potential concern in the marine envi ronment.