MEPS 144:133-146 (1996)  -  doi:10.3354/meps144133

This study investigates the fate of tributyltin (TBT), a widespread biocide mainly used in antifouling paints, and of its derivative dibutyltin (DBT) in sea anemones Aiptasia pallida exposed via water or food. Experiments were conducted on both symbiotic and aposymbiotic (lacking zooxanthellae) individuals under a 12 h light:12 h dark photoperiod or in total darkness. TBT and DBT concentrations in the animal and vegetal compartments were measured over 24 h, 30 h, 5 d, 7 d and 28 d periods. Uptake and accumulation from seawater, mainly as DBT due to natural degradation of TBT, was found to be dependent on the presence and illumination of zooxanthellae. DBT concentrations in symbiotic anemones exposed to light were roughly twice those found in individuals maintained in total darkness, and about 10 times greater than in aposymbiotic anemones. A peak accumulation in animal and vegetal tissues occurred after 24 to 48 h in all symbiotic anemones. A 28 d exposure of symbiotic anemones to a nominal 50 ng TBT l^-1 resulted in butyltin concentrations under 1 ng mg^-1 dry mass. Accumulation most probably occurs through butyltin uptake by zooxanthellae, while their expulsion from the host acts as a depuration process. The presence of zooxanthellae also seems determinant in the regulation and degradation of butyltin ingested with food. Daily ingestion of TBT-contaminated mussel tissue led to sequential debutylation into DBT and monobutyltin (MBT) in symbiotic A. pallida but not in aposymbiotic ones. Over 7 d, aposymbiotic anemones showed close to 100% retention of ingested TBT, while all butyltin species remained undetected in symbiotic anemones. After 28 d, the retention efficiency was ~68% in symbiotic anemones in which ~59% of the butyltin was in the form of DBT.

Accumulation · Aiptasia pallida · Degradation · Depuration · Dibutyltin · Sea anemone · Tributyltin · Zooxanthellae