Toxicity, uptake, and release of the water-soluble fraction of crude oil in different developing stages of the prawn Macrobrachium borellii.

The effects of a water-soluble fraction of light crude oil dissolved in freshwater (WSF) on Macrobrachium borellii exposed at three life stages was evaluated. Adults, larvae (PL), and embryos were exposed to five levels of WSF for 96 h. At 48 and 72 h PL were significantly more sensitive to WSF than adults, though values for 96-h LC50 were not significantly different (1.56 and 1.41 mg/L, respectively). Mortality was never high enough to allow LC50 calculation in embryos, but chronic exposure to WSF increased the mortality near hatching and significantly decreased PL survival compared to the control group. The uptake, accumulation, and depuration of WSF were evaluated in adult prawns (lipid content 1.5% wet wt) exposed to a sublethal concentration for 96 h followed by a 10-d depuration period. Hydrocarbons were rapidly taken up, and after 24 h most of them reached an equilibrium concentration. Increases in the number and alkylation of the aromatic rings enhanced both their accumulation and their retention. When returned to clean freshwater, levels of lighter aromatics dropped rapidly over 12 h. From these studies we conclude that early life stages of M. borellii are not very vulnerable to WSF toxicity, while adults have a rapid uptake and release of most of the contaminating hydrocarbons, probably due to their low lipid levels.