SUBLETHAL EFFECTS OF CONTAMINANTS ON THE METABOLISM OF 
METALS AND ORGANIC COMPOUNDS IN THE BAY MUSSEL 
Florence L. Harrison and John P. Knezovich 
Environmental Sciences Division 
Lawrence Livermore National Laboratory 
Livermore, CA 94550 
Abstract 
Biochemical mechanisms for the detoxification of metals and 
organic compounds in the bay mussel Mvtilus edulis were 
investigated. Mussels exposed to increased levels of copper in 
the laboratory were shown to have proteins that bind and thereby 
detoxify some metals. Chronic exposure to metals can cause 
saturation of the detoxification system, however, and result in 
metal interaction with sensitive enzymes and proteins. Accord¬ 
ingly, mussels from contaminated ecosystems (South San Francisco 
Bay and near municipal outfalls in the Southern California 
Bight) were shown to have increased levels of metals in meta¬ 
bolic pools as compared to mussels from a relatively pristine 
ecosystem (Tomales Bay). 
The ability of mussels to metabolize a trace organic 
contaminant (o-toluidine) was defined. Mussels were shown to 
metabolically activate this compound to a mutagenic form and 
also to detoxify it via basal metabolic pathways. Mussels from 
a contaminated site in San Francisco Bay demonstrated a dimin¬ 
ished ability to handle this contaminant as evidenced by a 
overall reduction in metabolic rate. Continuing research on 
mechanisms of biochemical adaptation will provide a better 
understanding of the adaptive capabilities of mussels from 
pristine and contaminated ecosystem. 
Introduction 
Organisms present in aquatic environments may be exposed 
continually to low concentrations of a variety of metals and 
organic compounds from anthropogenic sources. Concentrations of 
these contaminants in the environment are generally below those 
that cause mortality, but they may be sufficiently high to af¬ 
fect adversely an organism's growth rate, reproductive success, 
or ability to compete with other species in the ecosystem. 
Organisms may respond to such sublethal stress through the 
evolution of reproductive, behavorial, and physiological strate¬ 
gies that confer biological resilience. The goal of our re¬ 
search is to understand the limits of adaptation of basic bio¬ 
chemical processes that confer resilience to aquatic organisms. 
Our experiments are designed to obtain results that provide a 
better understanding of the basic mechanisms used by aquatic 
animals to handle increased quantities of trace metals and 
organic compounds in the environment. 
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