Effects of exposure source, worm density, and sex on DDT bioaccumulation and toxicity in the marine polychaete Neanthes arenaceodentata

The influence of exposure source, worm density, and sex on the bioaccumulat ion and toxicity of C-14-labeled DDT was evaluated for Neanthes arenaceoden tata. Emergent juvenile worms were exposed to DDT-spiked sediment (SED), DD T-spiked supplemental food (TetraMarin; TM), or a combination of both (SEDT M) in 28-d toxicity experiments. The DDT concentrations in the sediment and in the food were equal on an organic carbon basis. Higher body residues we re attained under the TM exposure compared to SED, indicating the importanc e of nonsedimentary organic matter as a source for contaminant uptake. The DDT was more bioavailable when associated with TetraMarin compared to sedim ent indicating that factors other than sorption to organic carbon can influ ence contaminant bioavailability. Body residues as high as 0.5 mol/g wet we ight were not associated with decreased survival, suggesting general narcos is as the mode of lethal toxicity of DDT to N. arenaceodentata. Most of the body burden was DDT unmetabolized compound (similar to 70%). Reduced growt h, observed under all exposures, was significant at lower concentrations wh en worms were fed DDT-spiked food (TM and SEDTM). Neanthes arenaceodentata may have detected the presence of DDT in the TetraMarin and decreased their feeding rate, at the cost of reduced growth. The influence of worm density on DDT toxicity and bioaccumulation was examined by exposing one or five w orms per beaker (74 and 370 worms/m(2), respectively) to spiked sediment. A lthough higher body residues were attained under low density, worms exposed in groups of five were significantly more sensitive to the effects of DDT on growth. Sex also had a large influence on DDT uptake kinetics. In sedime nt exposures (SED) to a trace concentration, the uptake clearance rate (mg( OC)/g lipids/h) was two times more efficient and the elimination rate was f ive times faster in mature males than in mature females.