Barrow’s goldeneyes are sea ducks that winter in protected nearshore marine waters in Prince William Sound and feed in the intertidal zone, consuming primarily mussels.
Some acute mortality of Barrow’s goldeneyes was observed in the weeks and months immediately following the Exxon Valdez oil spill in March 1989. Total acute mortality of Barrow’s goldeneyes is difficult to determine, given uncertainty in carcass identification and recovery rates, but sea ducks, generally, were vulnerable to acute mortality and constituted approximately 25 percent of the carcasses recovered in Prince William Sound. Given the number of Barrow’s goldeneyes present at the time of the spill, acute mortality was likely in the low thousands.
Of more concern are longer-term effects due to either chronic exposure to oil or indirect effects of trophic web disruption. Because Barrow's goldeneyes occur exclusively in intertidal and shallow subtidal habitats, they would be particularly vulnerable to effects of lingering oil. Similarly, reliance on intertidal invertebrate prey would suggest that Barrow's goldeneyes are particularly vulnerable to disruptions of intertidal communities.
Barrow's goldeneyes have been shown to have higher levels of induction of cytochrome P4501A (CYP1A) in oiled areas compared to unoiled areas. Elevated CYP1A induction in Barrow's goldeneyes from oiled areas of Prince William Sound was documented in 1997 and 2005. While these do not necessarily demonstrate subsequent injury, the potential for individual- or population-level effects of exposure to residual oil is plausible.
Barrow's goldeneyes will have recovered when breeding- and nonbreeding-season demographics and biochemical indicators of hydrocarbon exposure in goldeneyes in oiled areas of Prince William Sound are similar to those of goldeneyes in unoiled areas.
Within their wintering range, Prince William Sound is an important area, supporting between 20,000 and 50,000 wintering individuals. Survey data from the U.S. Fish and Wildlife Service indicated that winter numbers of goldeneyes on oiled areas were stable from 1990–1998, in contrast to significantly increasing numbers on unoiled areas during that same time period. That was interpreted as evidence of lack of recovery, as the prediction would be that lack of continued injury would result in parallel population trajectories and that recovery would be indicated by more positive trajectories on oiled areas. In the most recent published survey (through March 2005), slopes were parallel and stable over time, although this was due primarily to a decrease in goldeneye abundance on unoiled areas.
A study of Barrow’s goldeneye habitat use in oiled and unoiled portions of Prince William Sound found that densities of birds in oiled areas were at expected levels, given the habitat, suggesting that food limitations in the intertidal were not restraining recovery. Lingering oil still remains in intertidal habitats used by Barrow’s goldeneyes, maintaining the possibility of continued exposure and chronic effects.
Interpretation of surveys and habitat selection is constrained by lack of full understanding of Barrow’s goldeneye demography, particularly rates of site fidelity and dispersal. These values have important implications for understanding the process of population recovery.
Lack of elevated CYP1A in oiled relative to unoiled areas suggests that exposure to lingering oil has ceased in the Barrow’s goldeneyes, and thus, that at least part of the recovery objective has been met. Barrow’s goldeneyes are considered to be RECOVERING from the effects of the oil spill.
Click HERE for more information on Trustee Council funded studies of Barrow's goldeneyes.