Gradients of subsurface water toxicity to oyster larvae in bays and harbors in California and their relation to mussel watch bioaccumulation data

Crassostrea gigas larval toxicity tests were conducted on subsurface water samples collected from various California harbors ranging from San Francisco Bay to Newport Bay in southern California. The purpose of this study was to evaluate this test as an ambient toxicity monitoring tool and to attempt correlation of toxicity data with tissue contaminant concentrations. Los Angeles, Moss Landing and Richmond harbors showed trends of increasing toxicity with distance from the mouth of each harbor. These results were also compared to synthetic organic and metal tissue contaminant data collected by the California State Mussel Watch program. Increasing toxicity was significantly correlated with increasing tissue concentrations of lead, copper, silver, zinc, chlordane, endosulfan, dieldrin and PCB in some harbors (Richmond, Moss Landing, Los Angeles and Newport). Other harbors (Monterey, Santa Cruz and Redwood Creek) showed no correlations. However when data from all the harbors were combined there were no significant correlations between bioassay toxicity and contaminants found in mussels. For individual harbors, it is recommended that both accumulation data and bioassay data should be used in conjunction to assess toxicity in harbors.