Effects of Exposure Source, Worm Density, and Sex on DDT Bioaccumulation and Toxicity in the Marinepolychaete Neanthes Arenaceodentata

Abstract

Abstract-The influence of exposure source, worm density, and sex on the bioaccumulation and toxicity of 14 C-labeled DDT was evaluated for Neanthes arenaceodentata. Emergent juvenile worms were exposed to DDT-spiked sediment (SED), DDT-spiked supplemental food (TetraMarin; TM), or a combination of both (SEDTM) 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 were attained under the TM exposure compared to SED, indicating the importance of nonsedimentary organic matter as a source for contaminant uptake. The DDT was more bioavailable when associated with TetraMarin compared to sediment, indicating that factors other than sorption to organic carbon can influence contaminant bioavailability. Body residues as high as 0.5 mol/g wet weight were not associated with decreased survival, suggesting general narcosis as the mode of lethal toxicity of DDT to N. arenaceodentata. Most of the body burden was DDT unmetabolized compound (ϳ70%). Reduced growth, observed under all exposures, was significant at lower concentrations when 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 worms per beaker (74 and 370 worms/m 2 , respectively) to spiked sediment. Although 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 sediment 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 five times faster in mature males than in mature females.

The Effect of Organism Density on Bioaccumulation of Contaminants from Sediment in Three Aquatic Test Species: A Case for Standardizing to Sediment Organic Carbon

“…were exposed to sediment from site 2, the concentration of PCBs in the overlying water was approximately1.8 times higher in the standard volume treatment than the other two treatments (although measured at trace amounts; Table S3). In part, this supports the explanation for differential accumulation offered by Lotufo et al (2000), in that higher organism density may have caused increased bioturbation and movement of contaminant from the sediment and/or porewater into the overlying water. However, concentrations of PCBs in the overlying water of the 50:1 and 27:1 treatments in the present study were not different from each other (Table S3).…”

“…The present study is different from the other two studies in that it examines a much narrower range of organism densities (approximately 1.5 to 3.59 difference between treatments vs. 2 to 109 in Kukkonen and Landrum (1994) and 59 in Lotufo et al (2000)). Bioaccumulation tests in these other studies were conducted with spiked sediment and the use of radiolabeled compounds and were able to use relatively few and small organisms.…”

“…Lyytikäinen et al (2007) transplanted L. variegatus into fresh sediment at regular intervals during 12 days to investigate the depletion of the rapidly desorbing (labile) fraction of Polycyclic aromatic hydrocarbons (PAHs) from sediment and porewater and found that this had a minor effect on bioaccumulation in this species. In contrast, Lotufo et al (2000) observed greater bioaccumulation in the marine polychaete Neanthes arenaceodentata when organisms were exposed to sediment individually compared with groups of five. These results suggest that additional testing of the loading density of test organisms is warranted to determine its affect on bioaccumulation to standardize this component in bioaccumulation methods.…”

“…In our study, PCBs in overlying water were detected at trace amounts, or were lower than detection limits, with no apparent trends across treatments, suggesting that movement of PCBs to the overlying water was not affected by the density of the worms (Table S3). Lotufo et al (2000) assessed how exposure source, worm density, and sex affected the toxicity and bioaccumulation of DDT in the marine polychaete N. arenaceodentata. The polychaete worms were exposed individually or in groups of five to 50 ml sediment spiked with a range of concentrations of DDT.…”

“…Apart from the studies by Kukkonen and Landrum (1994) and Lotufo et al (2000), we are not aware of any other studies that have investigated whether and how bioaccumulation in test species is affected by the density of organisms. The present study is different from the other two studies in that it examines a much narrower range of organism densities (approximately 1.5 to 3.59 difference between treatments vs. 2 to 109 in Kukkonen and Landrum (1994) and 59 in Lotufo et al (2000)).…”