Bioaccumulation and toxicity of fluoranthene in the estuarine oligochaete Monopylephorus rubroniveus

The tolerance of the estuarine oligochaete Monopylephorus rubroniveus to fluoranthene was characterized both in the presence and absence of ultraviolet (UV) radiation. Using waterborne exposures, the 72-h median lethal concentration (LC50) and median lethal dose (LD50) were 0.7 (95% CI, 0.4–0.8) μg/L and 8.0 (5.6–9.6) μg/g worm dry weight, respectively, in the presence of UV radiation [UV-A=64.7±1.0 μW/cm2 (mean±standard deviation)]. In the absence of UV radiation, little mortality was observed, even at the water solubility limits of fluoranthene (120.4 μg/L). Mean bioconcentration factors across all treatments was 10,893±2828. Using sediment exposures, little mortality was observed following 10 days at concentrations as high as 3912 μg fluoranthene/g sediment dry weight in both the presence of UV radiation (UV-A=108.4±1.3 μW/cm2) and its absence. Bioaccumulation of sediment-associated fluoranthene was comparatively high and varied little among the five sediment treatments. The results of the present study demonstrate that M. rubroniveus is (1) sensitive to waterborne fluoranthene in the presence of UV radiation and (2) highly tolerant of fluoranthene in the presence of sediment, despite the ability to bioaccumulate fluoranthene to comparatively high levels. These findings suggest that those environmental factors which could potentially increase their exposure to UV radiation need to be considered when assessing the overall risk of fluoranthene to M. rubroniveus.