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Binding of hydrophobic organic and metal contaminants to particulate and dissolved organic matter (POM and DOM) in aquatic systems affects the availability of contaminants and their subsequent dose to biota. Eutrophic systems that contain high levels of organic sorbents will have lower concentrations of freely dissolved, readily available toxicant, thus reducing the exposure of the biota. In more oligotrophic systems with lower levels of sorbents, toxic exposure may be greater. These interactions suggest a relationship between the trophic state of an ecosystem and its susceptibility to toxic effects. Studies on the binding of organic contaminants to POM and DOM and its effects on toxicant accumulation are reviewed. The role of system productivity on adverse effects is explored by computer simulations, using a combined fate and effects model to evaluate the impacts of naphthalene on the production dynamics and contaminant body burden in different model populations when the concentration of POM varied from 0 to 10 mg C/L. Higher levels of POM decreased body burdens and moderated the reduction in productivity resulting from the exposure to naphthalene. Any interpretation of functional tests used to evaluate hazardous substances should consider the interaction between the trophic state of the system and the potentialmore » dose of toxicant available to biota.« less |
