Sunday, 27 February 2011

Persistence of oiling in mussel beds three and four years after the Exxon Valdez oil spill

Babcock, MM | Irvine, GV | Harris, PM | Cusick, JA | Rice, SD
PROCEEDINGS OF THE EXXON VALDEZ OIL SPILL SYMPOSIUM. pp. 286-297. American Fisheries Society Symposium. Vol. 18. 

Dense beds of the mussel Mytilus trossulus affected by Exxon Valdez crude oil in Prince William Sound and along the Kenai and Alaska peninsulas were intentionally left untreated during shoreline cleanup activities in 1989-1991. In 1992 and 1993, mussels and sediments from 70 mussel beds in Prince William Sound and 18 beds along the Kenai and Alaska peninsulas were sampled to establish the geographic extent and intensity of Exxon Valdez oil persisting in mussel beds. Sediments collected in 1992 and 1993 from 31 of the oiled mussel beds in the sound had total petroleum hydrocarbon (TPH) concentrations greater than 10,000 mu g/g wet weight. The highest concentrations were in sediments collected from Foul Bay (62,258 plus or minus 1,272 mu g TPH/g, mean plus or minus SE). Five of the 18 beds sampled along the Kenai Peninsula showed sediment TPH concentrations greater than 5,000 mu g/g. The mean concentration of total polynuclear aromatic hydrocarbons (TPAH) in mussels from these same beds ranged up to 8.30 plus or minus 0.26 mu g/g (Squirrel Island) in Prince William Sound and 4.01 plus or minus 1.54 mu g/g along the Kenai Peninsula (Morning Cove, Pye Islands). Polynuclear aromatic hydrocarbon fingerprints of mussel tissue collected from surveyed sites indicated the contaminant source was Exxon Valdez oil. In 1993, mean TPH concentrations in sediments and mean TPAH concentrations in mussels were lower by more than 50% compared with these concentrations in 1992. Some beds showed little reduction in oil. Almost all the beds showing only small decreases in hydrocarbons were in protected, low-energy areas, where there probably was little remobilization of residual oil underlying the beds. This study has produced analytical evidence showing that substantial residual Exxon Valdez oil persists in sediments underlying mussel beds in the area affected by the spill. Residual crude oil is a source of chronic contamination of mussels and their predators. In the more-protected intertidal areas, natural flushing and remobilization of Exxon Valdez oil will be slow; some of these mussel beds potentially can be manually cleaned.

Descriptors: Article Subject Terms Mytilus | contamination | crude oil | mussels | oil removal | oil spills | pollutant persistence | pollution effects | sediment pollution | sediments | water pollution effects | Article Taxonomic Terms Mytilus | Mytilus trossulus | Article Geographic Terms INE, USA, Alaska, Alaska Gulf | INE, USA, Alaska, Alaska Gulf, Prince William Sound | USA, Alaska