RESPONSE OF INFAUNAL BIVALVES TO THE EXXON VALDEZ OIL SPILL AND RELATED SHORELINE TREATMENT

摘要

Infaunal bivalves monitored in Prince William Sound intertidal sediments between 1990 through 1996 appear to have been affected more by shoreline treatment than by exposure to oil. Lower numbers were observed at oiled but treated (Category 3) sites whereas highest numbers were observed at reference (Category 1) sites. Species richness, very similar at reference and oiled but untreated (Category 2) sites after 1990, declined slightly during the study. Abundance, also quite similar at reference and Category 2 sites, peaked in 1992 or 1993 and then gradually declined through the remaining years. In contrast, averages for Category 3 sites exhibited no apparent trends representing recovery. Differences in both variables were highly significant between reference and Category 2 sites, on one hand, and Category 3 sites, on the other hand. Dominance patterns and behavior provide important insights into the effects of the spill, shoreline treatment, and the recovery process. Mysella tumida, Macoma spp., and Protothaca staminea dominated at reference and Category 2 sites but were far less common at Category 3 sites. These dominant species generally are relatively long-lived, slowly reproducing species that bury up to several centimeters below the surface of stable sediments. Mysella is typically commensal with larger burrowing species that are mostly absent or uncommon at Category 3 sites. In contrast, Hiatella arctica, the dominant at Category 3 sites, is an opportunist that nestles on the surface of disturbed sediments.