Produced water an aqueous petroleum waste which is discharged into the marine environment, can be toxic to a variety of developing marine organisms (Baldwin et al., 1992; Raimondi and Schmitt, 1992). Recently, it has been shown that the water soluble fraction of produced water is responsible for the majority of bioactivity (Higashi et al., 1992; Garman et al., Aquatic Toxicol, in press), and that this fraction primarily contains both strontium (Sr) and barium (Ba). We have investigated the effects of soluble Ba and Sr on development in the California mussel (Mytilus californianus) and the white sea urchin (Lytechinus anamesus).

When mussel embryos were exposed to Ba (as barium acetate) and/or Sr (as strontium chloride) through development to the veliger stage, only Ba exhibited bioactivity at the relevant concentrations. Concentrations as low as 100-200 ppb were found to impact embryo development in continual exposures. Embryos were also exposed to Ba in stage-specific pulse-chase experiments, and specific stages of development were affected. Gastrulation was most impacted, and this effect was not reversible following washing in clean seawater; this stage was also most affected by produced water. Exposure of early cleavage stages (blastula) and trochophore larvae to barium did not result in abnormal shell formation or calcification. Sr did not affect the embryos, nor did it modulate the barium effect. The inhibitory concentrations of Ba were similar to those found in effective dilutions of produced water. Furthermore, Ba was also found to inhibit normal pluteus larval development, including skeletogenesis, in sea urchins. We are currently developing an in vitro embryonic cell culture system for assessing the direct effects of both produced water and associated divalent cations on key developmental events.