This project determines the effects of chemically dispersed and biodegraded oils. Research provided a quantitative assessment of the rate of biodegradation of the components under a range of conditions found in the UK and cold US waters. Decision makers will use this information when choosing appropriate response options. The UK partners are the Maritime and Coast Guard Agency, the Department of the Environment for Rural Areas, and the Department of Trade and Industries.
The Alaska North Slope Oil and Corexit 9527 were shipped from the Ohmsett facility to Plymouth laboratory in the UK in 2003. The UK government supplied Forties Crude Oil and Super-dispersant 25. Plymouth labs conducted laboratory analyses using the 2 oil and 2 dispersants.
Many organizations utilize a range of bioindicators including the two organisms used in this study. The mussel, Mytilus edulis, was used to determine any detrimental effects of oil in the water column, and the amphipod, Corophium volutator, to measure the risk posed by oil trapped in sediments. Quantitative assessment of the rates of biodegradation of the major and minor components of each oil was made at 8 and 15-C, with and without each of the relevant dispersants. No significant enhancement of biodegradation of the whole oils was observed when dispersants were used and it was noted that the major losses over the study period were due to evaporation.
The experiments showed that although chemically dispersed oil may initially impact mussels and amphipods to a greater extent than would untreated oil, the organisms are mostly able to recover to the same extent as control organisms or to those exposed to oil alone. The exception to this were some exposures of Corexit-9527 dispersed water-accommodated fractions of ANS oil to mussels and amphipods where dispersion led to the highest concentrations of oil in the water and sediments.
A presentation of the results was made at the 15th annual SETAC conference in Lille, France on May 23, 2005.