Gulf Watch Alaska Long-term Monitoring Program - Evaluating Chronic Exposure of Harlequin Ducks and Sea Otters to Lingering Exxon Valdez Oil in Western Prince William Sound. Exxon Valdez Oil Spill Restoration Project Final Report (Restoration Project 12120114-Q)

Esler, Daniel; Bowen, Lizabeth; Miles, A; Ballachey, Brenda; Bodkin, Jim

Harlequin Ducks: For the first time since the 1989 Exxon Valdez Oil Spill, we found that average cytochrome P4501A induction (as measured by EROD activity) during March 2013 was not elevated in wintering harlequin ducks captured in areas of Prince William Sound oiled by the spill, relative to those captured in unoiled areas. Another metric of oil exposure (the incidence of individuals with elevated cytochrome P4501A induction) was consistent with this result, as it also showed similar values between oiled and unoiled areas. We interpret these findings to indicate that exposure of harlequin ducks to residual Exxon Valdez oil abated within 24 years after the original spill. These findings follow results from 2011, which showed reductions since 2009 in these metrics on oiled areas relative to unoiled and hence progress towards abatement of exposure, despite continued differences between areas in 2011,. The data presented in this report add to a growing body of literature indicating that persistence of oil in the environment, and exposure of wildlife to that oil, can occur over much longer time frames than previously assumed. These data may be used to define the duration of exposure (nearly two and a half decades) for one of the wildlife species most likely to suffer extended exposure. Sea Otters: Gene transcription patterns in sea otters were used to evaluate recovery of sea otters from the 1989 EVOS. In 2008, we sampled sea otter blood from oiled and unoiled areas of WPWS and compared gene transcripts from these samples to those from sea otters in captivity and wild sea otters from the Alaska Peninsula. We concluded that sea otters from oiled areas had gene transcription patterns consistent with chronic, low-grade exposure to organic compounds (Miles et al. 2012). In 2012, we resampled sea otters from the same areas of WPWS to determine if gene transcription patterns observed in 2008 persisted. Herein we present gene transcription data on sea otters from WPWS in 2008 and 2012, and include results from sea otters sampled from the Alaska Peninsula, Katmai, Clam Lagoon (Adak Island), Kodiak Island, and captive aquaria populations, as well as results from sea otters captured in WPWS in 2006, 2007 and 2010 but not reported previously. The 2006, 2007, and 2008 WPWS samples are referred to as PWS1, and the 2010 and 2012 samples as PWS2. Cluster analysis of gene transcription patterns was used in two statistical multivariate approaches, non-metric multidimensional scaling (NMDS) and heatmap analysis, and revealed similar results. The majority of sea otters sampled separated into 3 distinctive clusters: Cluster 1 - Kodiak and PWS1; Cluster 2 - Clam Lagoon and PWS2; and Cluster 3 - Katmai, Alaska Peninsula, and captive sea otters. Heatmap analysis showed lower relative transcription in Cluster 2 sea otters, higher relative transcription in Cluster 1 otters, and mixed transcriptional responses in Cluster 3 sea otters. The PWS2 sea otters exhibited transcript patterns consistent with a nutritional deficit or alternate resource allocation regime, which may be associated with an inability to mount effective responses to pathogens, contaminants, or stress. Overall suppression of the transcription response precluded concluding that sea otters from WPWS in 2012 showed no molecular signs of exposure to lingering oil.