A third experiment was performed to determined the effect of 
exposure to copper for longer periods of time than were used in 
the first two experiments. Mussels wee exposed to 10 and 25 ug 
Cu/L for 21 weeks. In those that were exposed to 25 ug Cu/L, 
there were large increases in the quantities of copper associ¬ 
ated with both the HMW and LMW proteins, whereas in those 
exposed to 10 ug Cu/L, there were large increases only in the 
LMW proteins (Figure 5). These results indicate that detoxifi¬ 
cation provided by the MT found in the LMW protein was adequate 
to prevent built-up of copper in the HMW protein fraction that 
contains enzymes critical for normal metabolism. 
In field studies we investigated the kinds and quantities of 
metals associated with these same proteins in populations from a 
pristine environment (Tomales Bay, CA) and in those from a con¬ 
taminated environment (South San Francisco Bay). In addition, 
we participated in a mussel-transplant study with Dr. John 
Martin (California Department of Fish and Game); bagged mussels 
from Tomales Bay were distributed in an array near a municipal 
outfall in the Southern California Bight and sampled sequential¬ 
ly with time. 
Field populations of mussels from the two sites were found 
to differ in the distribution of metals between the LMW and HMW 
metalloproteins (Table 1). It is apparent that the South San 
Francisco Bay mussel were contaminated highly with copper and 
cadmium. In mussels transplanted from Tomales Bay to the White 
Point outfall in the Southern California Bight, the concentra¬ 
tions of metals associated with the LMW and HMW proteins in¬ 
creased significantly after 1- and 3-month exposure to the 
effluent (Table 2). Copper, cadmium, and zinc were rapidly 
accumulated in the LMW protein fraction containing the MT, and 
some displacement of the essential metal, Zn, may have occurred. 
However, interpretation of the results was confounded because no 
measurements of the levels of MT were made. We currently have a 
methodology for quantifying MT, and in our future transplanta¬ 
tion studies, we will follow both the concentration of MT and 
the metals associated with both LMW and HMW metalloproteins. 
Results from these kinds of experiments will provide a better 
understanding of metal metabolism and adaptive capabilities of 
mussels from pristine and metal-contaminated ecosystems. 
Organic Compound Metabolism 
Marine bivalve molluscs efficiently concentrate organic 
chemicals present in the water. Whether an organism will be 
harmed by accumulated contaminants is determined largely by its 
ability to transform them into more water-soluble (detoxified) 
forms. Some metabolic transformations, however, result in the 
production of activated compounds that are more toxic than the 
original contaminants. 
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