Bioaccumulation test with Tubificid Sludgeworms in artificial media - development of a standardisable method

Lipophilic chemicals entering aquatic ecosystems often tend to adsorb to se diments. Although often not bioavailable to pelagic organisms, these compou nds can be subject to bioaccumulation and thus pose a potential threat for sediment-dwelling organisms. The assessment of bioaccumulation is currently based on the extrapolation of fish bioconcentration data. Thus, measuring the bioaccumulation in benthic organisms gives more detailed information on the hazard of chemicals for aquatic ecosystems. The freshwater tubificids Tubifex tubifex and Limnodrilus hoffmeisteri were chosen as test organisms. Breeding of the oligochaetes as well as bioaccumulation studies were carri ed out in a system consisting of artificial sediment and reconstituted wate r. C-14-lindane (gamma-hexachlorocyclohexane, gamma-HCH) and C-14-hexachlor obenzene (HCB) served as model substances. Additionally, C-14-3,4-dichloroa niline (3,4-DCA) was tested. Uptake and elimination of lindane and HCB were examined. Bioaccumulation factors (BAF) were determined from the ratio of concentration in oligochaete tissue to concentration in sediment. The tubif icids accumulated C-14-lindane, C-14-HCB, and C-14-3,4-DCA by factors of 4. 7 (mean value; n = 4), 6.6 (mean value; n = 4) and 13.2, respectively, base d on wet weight and radioactive concentrations. No major metabolites were d etected in worms, sediment and water. Elimination kinetics were examined fo r C-14-lindane and C-14-HCB. When transferred to clean sediment, the worms eliminated both test substances rapidly and nearly completely. The tubifici d bioaccumulation factors are contrasted with corresponding fish bioconcent ration factors from literature. The presented data indicate once more that the assessment of bioaccumulation based exclusively on lipophilicity and on the extrapolation of fish bioconcentration data to other organisms or envi ronmental compartments is not appropriate.