EDTA chelation and zinc antagonism with cadmium in sediment: effects on the behavior and mortality of two infaunal amphipods
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- Oakden, J.M., Oliver, J.S. & Flegal, A.R. Mar. Biol. (1984) 84: 125. doi:10.1007/BF00392996
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The two species of infaunal amphipod crustaceans Rhepoxynius abronius (Phoxocephalidae) and Eohaustorius sencillus (Haustoriidae) are characteristic of nearshore sandy bottoms along the California (USA) coast, and are highly sensitive to moderate levels of heavy metals. In laboratory experiments, both zinc and the chelator EDTA increased the survival of amphipods in sediment containing otherwise lethal levels of cadmium (8.5 μg g-1), which are representative of moderately polluted environments. In simple choice experiments, amphipods prefer sediment with complexed cadmium. The behavioral and survival patterns of both species were similar in the experiments. EDTA prevented about 50% of the added cadmium from initially being incorporated into the sediment, and increased the rate of cadmium released from the sediment. These data illustrate the limitations of operational definitions of chemical analyses, since weak-acid (0.5 N HCl) leaches that were intended to provide an estimate of the “biologically available” metal concentrations extracted both toxic and EDTA-complexed cadmium species and did not account for their antagonistic interctions with zinc.