Lessons from 10 Years of Post-Exxon Valdez Monitoring on Intertidal Shorelines

Abstract

ABSTRACT Intertidal shorelines impacted by the Exxon Valdez oil spill have been monitored by the National Oceanic and Atmospheric Administration (NOAA) since late 1989. Originally intended to document oil fate and impacts of hot-water high-pressure washing, the program evolved into a comprehensive examination of long-term recovery processes in these environments. Annual field sampling and laboratory and statistical analyses are combined to document trends in biology, chemistry, and geomorphology of 26 sites in Prince William Sound. Recovery processes in shoreline ecosystems occur over different time frames, depending on the particular measure and scale used. Using a geomorphological measure, most boulder/cobble sites where berm relocation was carried out to remove subsurface oil took 1–2 years to return to pre-treatment configurations. Mean levels of polyaromatic hydrocarbons in mussels from oiled sites remained elevated for approximately 3–4 years after the spill. Abundance trends for most epibiota species at mid intertidal zones from oiled sites were parallel to those from unoiled sites after 1–2 years. Longer lasting impacts were found for infaunal species at low elevations, perhaps related to changes in grain size composition at washed sites. Some impacts from oiling remained at sensitive sites through at least 1997, including subsurface oiling, species abundance differences, and patchy areas of sediment and bivalve contamination from polyaromatic hydrocarbons.