Abstract
Freshwater sediment-dwelling Lumbriculus variegatus is known to serve as a vector for the transfer of contaminants from sediments to higher trophic level organisms, but limited data exist on the bioaccumulation of chemicals associated with sediments containing high total organic carbon (TOC). In the current study, sediments from the north shore area of Lake Apopka (Florida, USA), containing very high TOC [39 % (w/w)], were spiked with four chemicals-p,p'-dichlorordiphenyldichloroethylene (p,p'-DDE), dieldrin, fipronil, and triclosan-individually or in a mixture of the four and then used for bioaccumulation studies. Tissue concentrations of chemicals in L. variegatus were measured at 2, 7, 14, 21, and 28 days of exposure, and the bioaccumulation potential was evaluated using biosediment accumulation factors [BSAF (goc/glipid)]. Increase in total body burdens of all four chemicals in L. variegatus was rapid at day 2 and reached a steady-state level after 7 days in both single and mixture experiments. Tissue concentrations of fipronil peaked after 2 days and then decreased by 70 % in sediment experiments suggesting that in addition to the degradation of fipronil that occurred in the sediment, L. variegatus may also be able to metabolize fipronil. The calculated 28-day BSAF values varied among the chemicals and increased in the order fipronil (1.1) < triclosan (1.4) < dieldrin (21.8) < p,p'-DDE (49.8) in correspondence with the increasing degree of their hydrophobicity. The relatively high BSAF values for p,p'-DDE and dieldrin probably resulted from lower-than-expected sorption of chemicals to sediment organic matter either due to the nature of the plant-derived organic matter, as a result of the relatively short equilibration time among the various compartments, or due to ingestion of sediment particles by the worms.