The most recent studies indicate that key injured resources are no longer being affected by the lingering oil that remains in the substrate of certain beaches. Passive samplers deployed for 10 days in summer 2015 in the intertidal zone of one of the most contaminated beaches detected no Exxon Valdez oil leaching into the water, confirming that the oil remains sequestered in the subsurface and is not biologically available, despite remaining in a largely un-weathered state.
Measures of population status of species such as harlequin ducks and sea otters are now similar between oiled and unoiled sites, indicating recovery from long-term effects of the spill, including consequences of exposure to lingering oil (Esler et al. 2015b).
However, while the natural resource damage from lingering oil is largely abating, twenty-five years of research on the Exxon Valdez Oil Spill has demonstrated the surprising persistence of the toxic components of Exxon Valdez oil in the environment. This research illuminates the long-term effects of the Spill and the chronic damage that took nearly a quarter of a century to abate.
Oil lingering from the 1989 Spill has been identified in discontinuous patches buried in sediments in the intertidal zone of some beaches in western Prince William Sound (PWS), where it was deposited soon after it washed ashore from the Spill. The patches are not visible on the beach surface, as they are buried at average depths between 12 to 18 cm (Fig. 1) and typically under the "armour" of bouldered beaches.