Bioaccumulation and toxicity of tributyltin to a burrowing heart urchin and an amphipod in spiked, silty marine sediments

The presence of tributyltin (TBT) in silty sediments is regarded as along-t erm threat to marine and estuarine environments due to its persistence. The bioaccumulation kinetics and toxicity of TBT in the deposit-feeding heart urchin Echinocardium cordatum was studied in silty sediment spiked with TBT and equilibrated prior to the 28-d exposure. An additional 10-d acute toxi city test was carried out with the burrowing amphipod Corophium volutator i n the same sediment. Because E. cordatum has a low lipid content and appare ntly high elimination and metabolic rates, only a moderate degree of TBT bi oaccumulation was observed, with biota-sediment accumulation factors (BASFs ) of 0.09 to 0.21 (dry weight basis) and biota accumulation factors (BAFs) of 180 to 843 (wet weight basis). The lethal body residue in E. cordatum (s oft tissue and skeleton) was 0.8 to 3.4 nmol TBT+/g wet weight which, consi dering the differences in lipid content, is comparable to data on other tax onomic groups. For E. cordatum and C. volutator, the LC50s for pore water ( 222 and 329 ng Sn/L) were also close to reported values for aquatic and ben thic organisms. The TBT concentrations in the pore water of the silty sedim ent were much lower than might be expected from the octanol-water partition coefficient. The measured sediment-water partitioning coefficient K-p was 8,700 L/kg dry weight. Consequently, toxicity was observed at a relatively high TBT concentration in the bulk sediment with LC50s for E. cordatum and C. volutator of 1,594 and 2,185 ng Sn/g dry weight, respectively. The resul ts show that TBT is highly toxic to the benthic species investigated and so rption in the silly sediment strongly reduced the bioavailability of the co mpound.