Criteria for oil spill recovery: a case study of the intertidal community of Prince William Sound, Alaska, following the Exxon Valdez oil spill.

Marine intertidal organisms in Prince William Sound were exposed to crude oil following the TN Exxon Valdez oil spill in 1989. The intertidal communities were also subjected to mechanical disturbance during invasive oil spill remediation and cleanup efforts. Using monitoring data collected from 1989 to 1997, impacts and eventual recovery were assessed at oiled but uncleaned sites and oiled and cleaned study areas. A statistical model where recovery was defined as parallelism between the time profiles at control and oiled sites was evaluated. Statistical analysis and graphical presentations of the data suggest intertidal epibiota communities recovered from the oil spill by 1992 at the oiled sites and by 1994 at the oiled and remediated sites. Empirical data from the intertidal monitoring program supports the use of tests of parallelism in evaluating recovery and the need to avoid simply the comparison of sample means from control and oiled sites.