On May 2, 2014, OR&R Senior Scientist Alan Mearns presented a talk at the session "Spill prevention, preparedness and response issues in the Salish Sea and Pacific Northwest" on uptake and depuration of PAHs in mussels following the May 2012 DeepSea diesel spill in Penn Cove, Washington.

Dr. Mearns’ jointly-authored (Shigenaka, Meyer and Drury) talk was given at the 2014 Salish Sea Ecosystem Conference , held in Seattle from April 30 through May 2.

Major points of the talk were: mariculture mussels submerged 1 to 2 meters below the surface, were contaminated by the spill, and that depuration was extremely slow (4 months) compared to much of the literature suggesting depuration rates in clean water on the order of several weeks.

Abstract: Diesel spills are common in Northwest coastal waters but there is little information about the rate at which exposed shellfish might purge bioaccumulated hydrocarbons. The literature suggests a few weeks. We tested that hypothesis following a May 2012 discharge of diesel from a sunken fishing vessel located adjacent to a mussel farm in Penn Cove, Washington. Using an adaptive monitoring strategy, mussels were collected on four occasions following the spill and removal of the derelict vessel and analyzed for 43 polycyclic aromatic hydrocarbons (PAHs). PAHs were elevated 5 days into the spill but did not exceed seafood safety guidelines. The biological half-life of total PAH whole soft tissue concentrations was on the order of four to five months, a much longer depuration time than previously suspected. The reason for the slow depuration was not determined, but may due to slow exchange of cove water with clean water from Admiralty Inlet and Puget Sound, a process that supports local larval retention and stresses the need to prevent fuel spills in shellfish growing areas.

For further information, contact Alan.Mearns@noaa.gov.

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