Fate of a new silicone-based oil-treating agent and its effects on marine microbial communities

A new silicone-based agent was developed to treat and recover oil slicks an d various floating oily residues that are often observed in marinas and har bors. As part of its ecotoxicologic assessment, the fate of the treating ag ent alone or combined with crude oil, and the effects on natural microbial communities were studied in estuarine mesocosms (3.5 m(3)) over a 9-week pe riod. The ability of the in situ formed silicone layer to trap an oil slick at the water surface was highlighted by a significative reduction in the v olatilization, natural dispersion, and sedimentation of the treated oil. Th e treatment favored the dissolution of light aromatic hydrocarbons such as methyl-naphthalenes but these compounds were rapidly biodegraded in the wat er column. The agent alone, as well as the treated or untreated oil, had no effect on the biomass and photosynthetic ability of the phytoplankton comm unity entrapped in the mesocosms. A significant stimulation of oil-degradin g bacteria was noted in mesocosms containing treated and untreated oil slic ks. On the basis of these results, we conclude that the use of a silicone-b ased treating agent could be an effective countermeasure to an oil spill, w ith neither deleterious effects to natural microbial communities nor to lon g-term biodegradation of the unrecovered oil residues.