FOODBORNE UPTAKE AND SUBLETHAL EFFECTS OF COPPER AND ZINC TO FRESH-WATER SNAILS

Snail habitat selection was strongly influenced in this research by me asured copper (Cu) contribution from a power plant discharge. Laborato ry feeding studies showed that the snail Leptoxis praerosa significant ly bioconcentrated Cu when fed aufwuchs containing 564 (+/- 269) mu g Cu g(-1) but did not have significant cellulolytic enzyme activity imp airment. No foodborne zinc (Zn) bioconcentration was found from aufwuc hs containing up to 20 000 (+/- 18 400) mu g Zn g(-1). These results s uggest that water column Cu concentrations leading to impairment via f eeding mechanisms can be an order of magnitude higher than concentrati ons causing impairments via waterborne exposures. Therefore, foodborne uptake might be expected to contribute to toxicity rather than domina te toxicity in most conditions where waterborne concentrations of meta ls occur. Changes in food quality appeared to have a greater overall e ffect on snail populations than foodborne uptake of metals alone. Snai l populations took 2 years to recover following intensive metal treatm ent on the plant discharge and subsequent reduction of measured metal concentrations in both water and aufwuchs.