Sublethal Effects of Tributyltin on the Hard Shell Clam, Mercenaria mercenaria,
HARBOR BRANCH OCEANOGRAPHIC INST INC FORT PIERCE FL
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Chronic bioassays, lasting at least 7 days, show that veliger stages of clams, Mercenaria mercenaria, are the most sensitive to exposure to tributyltin compounds TBT. Post-set clams survived exposures up to 7.5 micrograms1 for 25 days. No veligers, the planktonic larval stage, however, survived 7 days in 750 ng1. Valve length of veligers, an index of growth, was statistically less than controls in concentrations of 50 ngL and above on day 14 of development. When clam embryos are exposed to TBT, effects on subsequent stages are the most severe, suggesting that TBT exerts its most damaging effects very early in larval development. Data from these studies suggest that acute toxicity to clams would not occur in most habitats due to exposure to TBT from antifouling coatings. Sublethal effects, however, could result from lower exposures typical of some sites. Field observations to assess ecological consequences would be most useful to confirm risk estimates.
- Biological Oceanography