Toxicity and bioaccumulation of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin in long‐term tests with the freshwater benthic invertebrates Chironomus tentans and Lumbriculus variegatus

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Abstract
Two species of freshwater benthic invertebrates, Chironomus tentans and Lumbriculus variegatus, were exposed to three dietary concentrations of 2,3,7,8‐ tetrachlorodibenzo‐p‐dioxin (TCDD), and toxicity and bioaccumulation were determined. No toxic effects were observed in full life cycle tests with either species at tissue residue concentrations up to 9,533 ng TCDD/g lipid. The observed lack of sensitivity of the two species to TCDD was consistent with a presumed absence of the aryl hydrocarbon receptor in aquatic invertebrates. Predictions of lipid‐normalized tissue concentrations were made based on lipid‐normalized TCDD concentrations in the food and were within 15% of targeted concentrations in both species. Depuration studies indicated that TCDD elimination followed first‐order kinetics, with elimination rate constants of 0.0014 to 0.0022 h−1 for L. variegatus and 0.0070 to 0.0099 h−1 for C. tentans. Half‐lives ranged from 315 to 495 h in L. variegatus and from 70 to 99 h in C. tentans. The ability of invertebrates to accumulate relatively high concentrations of TCDD in the absence of toxic effects may be relevant to the transfer of contaminants through aquatic food webs to potentially sensitive vertebrate species.

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