Assessment of Bivalve Recovery on Treated Mixed-Soft Beaches In Prince William Sound, 2000

National Oceanic and Atmospheric Administration treatment effects studies from 1989 through 1997 suggested that bivalve assemblages on beaches in Prince William Sound treated with high-pressure washing were severely injured in terms of abundance, species composition, and function. Restoration Project 040574 assessed the generality and persistence of this apparent injury to this assemblage by sampling various treated and untreated sites in 2002. We found that the initial conclusions were accurate, indicating that a considerable proportion of mixed-soft beaches in treated areas of the sound remained extremely disturbed and that these beaches are functionally impaired in terms of their ability to support foraging by humans and damaged nearshore vertebrate predators such as sea otters 13 years after the spill. Large, long-lived hard-shell clams remained 66% less abundant at Treated sites than at Reference sites. We also found that standard sediment properties did not appear implicated in lagging recovery. But, based on several lines of evidence, we deduced that a major cause for the delay was the disruption of surface armoring (a stratified organization of mixed-soft shoreline sediments common in southcentral Alaska), an effect of beach washing. Based on the apparent recovery trajectory, we predict that recovery to pre-spill status will take several more decades. We also found that sedimentary components and the biota in the armored mixed-soft sediments in Prince William Sound do not respond according to traditionally described paradigms for homogeneous sediments.
Citation: Lees, D. C., and W. B. Driskell. 2007. Assessment of Bivalve Recovery on Treated Mixed-Soft Beaches in Prince William Sound, Alaska. Exxon Valdez Oil Spill Restoration Project Final Report (Restoration Project 040574). National Oceanic & Atmospheric Administration National Marine Fisheries Service, Office of Oil Spill Damage & Restoration, Auke Bay, Alaska.