ratio of the mean concentrations for the outfall 

 and control samples (Table 2). 



It seems clear from these data that rock scallops 

 living inshore of the JWPCP discharge accumu- 

 late trace metals at above-normal levels. Applica- 

 tion of the 2-sided Mann-Whitney U Test (Tate 

 and Clelland 1957), a nonparametric test which 

 assumes neither normality nor homogeneity of 

 variance, indicated that, in 10 of the 19 compari- 

 sons, the experimental (JWPCP) results are sig- 

 nificantly different from those of the controls (Ta- 

 ble 1). In all 10 of these cases the experimental 

 means are higher. 



In our past studies with molluscan bioin- 

 dicators, we have generally used digestive gland 

 concentrations to locate possible metal contami- 

 nation because concentrations are usually higher 

 in this tissue than in the gonad or adductor muscle 

 (Alexander and Young 1976; Eganhouse and 

 Young 1976). However, these values may not be 

 representative of the degree to which metals are 

 actually incorporated into the body tissues be- 

 cause the digestive gland sample may contain in- 

 gested particulates contaminated by metals that 

 are not biologically available. Therefore, the 

 gonad and muscle contamination ratios found in 

 this study are of special interest. In 7 of the 12 

 comparisons, the experimental results were found 

 to be significantly higher than those of the controls 

 (Table 2). For five of the six metals measurable 

 (lead was undetectable in these tissues), at least 

 one of the two contamination ratios is essentially 

 ^2. In addition, we found the mean concentration 

 (±1 SE) of total mercury in adductor muscle of 

 three Palos Verdes scallops to be 0.059 ±0.005 

 mg/wet kg. This value is more than twice the mean 

 concentration measured in three island specimens 

 (0.027 ±0.008 mg/wet kg). However, it should be 

 noted that mercury levels in the Palos Verdes 

 specimens were still an order of magnitude below 

 the U.S. Food and Drug Administration action 



Table 2. — Contamination factors' for seven metals in three 

 tissues of rock scallops from the Palos Verdes outfall zone and 

 island control stations. Factors indicate experimental to control 

 ratios for mean concentrations (Table 1). 



level of 0.5 mg/wet kg in seafood intended for in- 

 terstate commerce. 



As shown in Table 1, the mean concentration of 

 lead in the digestive gland of the outfall scallops 

 was 9.3 mg/wet kg, approximately 100 and 200 

 times the upper limit concentrations measured in 

 the gonadal and muscle tissues, respectively. 

 These results indicate that elevated concentra- 

 tions of other metals measured in the gonad and 

 muscle tissues were not caused by contamination 

 from the digestive gland during dissection. Thus, 

 rock scallops exposed to municipal discharges do 

 appear to be capable of physiologically incorporat- 

 ing at least six potentially toxic trace metals in 

 their gonadal or muscle tissue to levels at least 

 twice normal concentrations. 



The mean values for cadmium in the digestive 

 gland and gonads of the Palos Verdes specimens 

 were somewhat lower than those for the island 

 controls (Table 1 ); the respective outfall-to-control 

 ratios were 0.80 and 0.92. We have made similar 

 observations in previous studies of metals in 

 flatfish taken by trawl from the two areas (de Goeij 

 et al. 1974; McDermott, Alexander, Young, and 

 Mearns 1976). Liver tissue from Dover sole, Mi- 

 crostonms pacificus, collected during 1971-72 and 

 known by their high DDT levels and high inci- 

 dence of fin erosion disease to have inhabited the 

 highly contaminated sediments, were shown by 

 neutron activation analysis to have significantly 

 lower concentrations of cadmium than did the liv- 

 ers of island control specimens; the outfall-to- 

 control ratio was 0.33 (de Goeij et al. 1974). 

 Analyses of subsequent collections (1972-73) 

 using a different laboratory and analytical 

 technique (arc emission spectroscopy) confirmed 

 this observation, yielding an outfall-to-control 

 ratio of 0.59 (McDermott, Alexander, Young, and 

 Mearns 1976). In addition, analyses by atomic ab- 

 sorption spectroscopy recently conducted in our 

 laboratory revealed depressed cadmium concen- 

 trations in livers of diseased flatfish collected dur- 

 ing 1976 and 1977 off Palos Verdes Peninsula and 

 in Seattle's Duwamish River Estuary (two regions 

 highly contaminated by chlorinated hydrocar- 

 bons); relative to control levels, the corresponding 

 concentration ratios were 0.60 and 0.30, respec- 

 tively."* Further, analyses of digestive glands of 

 intertidal mussels we collected at the base of the 



'Single and double asterisks indicate significant differences between ex- 

 perimental and control results at P<0.05 and P 0.01. respectively 



■•Sherwood, M. J. 1977. Fin erosion disease and liver chemis- 

 try: Los Angeles and Seattle. In Coastal water research project 

 annual report, p. 213-219. South. Calif. Coastal Water Res. Proj., 

 El Segundo. NTIS PB274463/AS. 



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