Evaluation of bioaccumulation and photo-induced toxicity of fluoranthene in larval and adult life-stages of Chironomus tentans.

Abstract

Laboratory sediment tests were conducted to evaluate the bioaccumulation and photo-induced toxicity of fluoranthene in larval and adult life-stages of the midge, Chironomus tentans. In the first of 2 experiments, fourth-instar and adult C. tentans exposed to spiked sediments (204 microg fluoranthene/g dry weight) were collected for determination of fluoranthene tissue concentrations and toxicity after ultraviolet (UV) radiation treatment in the absence of sediment (water-only). Fluoranthene tissue concentrations in larvae collected after a 72-hour exposure period were 7 times greater than concentrations in adults collected on emergence from the same spiked sediments. Fluoranthene-exposed adults were tolerant of UV exposure (100% survival after 7 hours), whereas larvae were sensitive (0% survival after 1 hour). In the second experiment, C. tentans larvae were exposed for 96 hours to 2 sediment treatments (170 and 54 microg fluoranthene/g dry weight), after which fluoranthene tissue concentrations were determined and UV exposures conducted under water-only versus sediment conditions. Exposure to UV radiation, in conjunction with sediment, provided larvae with significant protection from photo-induced toxicity compared with the water-only exposure. Adults that emerged from the 2 sediment treatments were also analyzed for fluoranthene tissue residues and exposed to UV radiation. Fluoranthene tissue residues were higher in adult female than in adult male midges, but exuviae from both sexes contained higher fluoranthene concentrations than whole-body tissue, thus demonstrating that the molting process is a possible detoxification mechanism. Consistent with the greater tissue residue concentrations, female midges demonstrated a significant decrease in survival under UV exposure compared with male midges. These studies indicated that both the burrowing behavior of the larvae and the elimination of fluoranthene in molted exuviae are protective mechanisms against photo-enhanced PAH toxicity in this species.