The influence of organic chelators on the toxicity of copper to embryos of the Pacific oyster, Crassostrea gigas.

The effects of copper on the development of Crassostrea gigas embryos were determined with a 48-hr static bioassay. In filtered, sterilized seawater from Bodega Bay, California, the LC100 was 20 microgram Cu/L, and the LC50 was 12 microgram Cu/L. Destruction of the naturally occurring dissolved organic material in the culture water by UV oxidation decreased embryo survival at 10 microgram Cu/L. The addition to seawater of five organic chelators (ethylenediaminetetraacetic acid (EDTA), sodium citrate, glycine, and oxalate at 1 x 10(-6) M, and humic matter at 2 mg/L) increased embryo survival. EDTA and humic matter were the most effective chelators; EDTA significantly increased survival at 100 microgram Cu/L and humic matter did so at 40 microgram Cu/L. The ability of a chelator to increase survival was related to the stability constant of the copper-chelator complex.