Uptake, depuration, and toxicity of dissolved and sediment-bound fluoranthene in the polychaete, Capitella sp. I.

Deposit-feeders may be important in facilitating the removal of organic contaminants from bulk sediment. The relationship between uptake route (water vs sediment), depuration and toxicity was investigated in the deposit-feeding polychaete Capitella species I. Individual worms were exposed either to dissolved (i.e., < 0.45 micron) fluoranthene (FLU) (water-only treatment [WO]), or both to dissolved and sediment-bound FLU (porewater and sediment [PWS] treatment). The porewater concentration of dissolved FLU in PWS was set approximately equal to the dissolved concentration in WO (0, 50 micrograms FLU l-1). Fluoranthene marginally affected growth in WO worms (6 d exposure) but not in PWS worms (5 d exposure). The final body-burdens in PWS and WO worms were 141.2 and 99.5 micrograms total FLU equivalents (g dry wt worm)-1, respectively. Sediment-bound FLU was calculated to contribute at least 30% and up to as much as 91% of the total amount taken up by PWS worms. Water-only treatment worms retained all of the FLU during the subsequent depuration (4 d), whereas PWS worms decreased both the weight-specific (t1/2 = 0.95 d) and the total-body burden (t1/2 = 7.8 d), suggesting both active excretion and dilution of FLU body burden as a result of growth. Thus, our results indicate that the sediment-associated pool is an important route of uptake in Capitella sp. I, and that such deposit feeders may be important for remobilization of sediment-associated contaminants, such as fluoranthene.