Effects Of Chemicals In Thermal Effluent On Homarus americanus Maintained In Aquaculture Systems1

Abstract

ABSTRACTEffects of chemicals in thermal effluent on American lobsters (Homarus americanus) maintained in aquaculture systems were evaluated. Atomic absorption analysis of intake and effluent water samples from three fossil‐fuel generating stations in southern California indicated that chemical additions did not affect concentrations of Cu, Zn, Cd, Co, Cr, Pb, and As in the thermal effluent. Concentrations of these metals in the intake and effluent water at the San Diego Gas & Electric Company's Encina Power Plant were not significantly different than their concentrations in seawater from the Scripps Institution, and were well within the reported ranges for levels of those metals in normal seawater. The amounts of heavy metal chelating agents in Encina effluent were significantly greater than in Encina intake and Scripps seawater.No significant differences were observed in mean concentrations of Cu, Zn, Cd, Pb, Cr, and Co in larval, juvenile and adult lobsters maintained in three water types (Encina effluent, Encina intake and Scripps). Lobsters maintained in Scripps seawater were dissected and metal levels in the gills, hepatopancreas, tail muscles, claw muscles, digestive tract, and exoskeleton were analyzed by atomic absorption. The highest concentrations of Cu, Zn, Co and Cr were found in the gills, while Cd was found in equally high concentrations in the gills and hepatopancreas. The lowest concentrations of Cu, Zn, Cd, and Cr were found in the exoskeleton, while Pb and Co were found in the lowest concentrations in the tail muscle. Regressions of metal levels in tissues of lobsters on carapace length indicated that Hamericanus does not accumulate metals in the tissues, but rather regulates the levels.The 24, 48, 72, and 96 hour median lethal limits for Cu++, Zn++, Cr6+, Co+++, Cd++, Pb++, Cl−, and acids were established for lobster larvae held in static systems. Median effective times also were determined. Median lethal limits for these eight chemicals were all far above levels of the chemicals encountered in the generating station effluents. In most cases they were at least an order of magnitude higher. Longterm bioassays in static systems indicated that growth and survival of larval and juvenile lobsters were similar in Encina effleunt, Encina intake, and Scripps seawater at constant temperature.All of these studies indicate that the thermal effluent from typical generating stations in southern California provides an essentially pollution‐free heated water source for the culture of H. americanus.