2013 update on sea otter studies to assess recovery from the 1989 <i>Exxon Valdez</i> oil spill, Prince William Sound, Alaska

Abstract

For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment-visit http://www.usgs.gov or call 1-888-ASK-USGS For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprodTo order this and other USGS information products, visit http://store.usgs.gov Suggested citation: Ballachey, B.E., Monson, D.H., Esslinger, G.G., Kloecker, K., Bodkin, J., Bowen, L., and Miles, A.K., 2014, 2013 update on sea otter studies to assess recovery from the 1989 Exxon Valdez oil spill, Prince William Sound, Alaska: U.S. Geological Survey Open-File Report 2014-1030, 40 p., http://dx.doi.org/10.3133/ofr20141030. ISSN 2331ISSN -1258 Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted material contained within this report. Executive SummaryOn March 24, 1989, the tanker vessel Exxon Valdez ran aground in Prince William Sound, Alaska, spilling an estimated 42 million liters of Prudhoe Bay crude oil. Oil spread in a southwesterly direction and was deposited on shores and waters in western Prince William Sound (WPWS). The sea otter (Enhydra lutris) was one of more than 20 nearshore species considered to have been injured by the spill. Since 1989, the U.S. Geological Survey has led a research program to evaluate effects of the spill on sea otters and assess progress toward recovery, as defined by demographic and biochemical indicators. Here, we provide an update on the status of sea otter populations in WPWS, presenting findings through 2013. To assess recovery based on demographic indicators, we used aerial surveys to estimate abundance and annual collections of sea otter carcasses to evaluate patterns in ages-at-death. To assess recovery based on biochemical indicators, we quantified transcription rates for a suite of genes selected as potential indicators of oil exposure in sea otters based on laboratory studies of a related species, the mink (Mustela vison). In our most recent assessment of sea otter recovery, which incorporated results from a subset of studies through 2009, we concluded that recovery of sea otters in WPWS was underway. This conclusion was based on increasing abundance throughout WPWS, including increasing numbers at northern Knight Island, an area that was heavily oiled in 1989 and where the local sea otter population had previously shown protracted injury and lack of recovery. However, we did not conclude that the WPWS sea otter population had fully recovered, due to indications of continuing reduced survival and exposure to lingering oil in sea otters at Knight Island, at least through 2009. Based on data available through 2013, we now conclude that the status of sea otters-at all spatial scales within WPWS-is consistent with the designation of recovery fro...

Gene Transcript Profiling in Sea Otters Post-Exxon Valdez Oil Spill: A Tool for Marine Ecosystem Health Assessment

“…However, several studies on sea otter demographics indicated that by 2012, the WPWS sea otter population had returned to pre-spill conditions. While sea otter abundance at the scale of WPWS had demonstrated modest increases since 1993, areas most severely impacted by oil-related mortality did not return to pre-spill numbers until 2011 [8]. The numerical recovery of sea otters was supported by improved survival of sea otters after 2009, with a return to rates observed prior to the spill [4,8,55].…”

“…The effects of the 1989 Exxon Valdez oil spill (EVOS) on nearshore marine vertebrates in Prince William Sound, Alaska, including the sea otter (Enhydra lutris), have continued for more than two decades [1][2][3][4][5][6][7][8][9]. A series of long-term studies demonstrated a lack of recovery of sea otters through at least 2009 [1,4,[6][7][8][9], based on reduced rates of survival and exposure to residual oil in western Prince William Sound (WPWS), although the importance of continuing exposure as a factor constraining sea otter recovery has been debated [10][11][12]. To evaluate population health and recovery of sea otters and other species potentially affected by the spill, the Exxon Valdez Oil Spill Trustee Council established physiologic (based on biomarkers indicating exposure to aromatic hydrocarbons) and demographic (based on a return to expected abundance or reproduction/survival rates) criteria.…”

Lactation and resource limitation affect stress responses, thyroid hormones, immune function, and antioxidant capacity of sea otters (Enhydra lutris)

“…Conversely, sea otter populations in both Washington and SE Alaska were established by re‐introduction in 1969 and 1970 (Jameson et al., ; Kenyon, ), and thus, our resource‐limited samples from these regions come from subpopulations that have only recently reached carrying capacity. Similarly, sea otters in western Prince William Sound are believed to have been at carrying capacity for several decades, although this population was depleted by the Exxon Valdez Oil Spill in 1989, and only recently has recovered to the point that resources are once again the primary limiting factor (Ballachey et al., ; Monson, Doak, Ballachey, & Bodkin, ; Monson, Doak, Ballachey, Johnson, & Bodkin, ).…”

“…have been at or near carrying capacity for many decades (Tinker et al, 2017). Conversely, sea otter populations in both Washington and SE Alaska were established by re-introduction in 1969 and 1970 (Jameson et al, 1982;Kenyon, 1969) (Ballachey et al, 2014;Monson, Doak, Ballachey, & Bodkin, 2011;Monson, Doak, Ballachey, Johnson, & Bodkin, 2000).…”

Effects of Macondo Oil on Phytoplankton from Grand Isle, Louisiana

“…Although much of the literature on the impacts of oil spills on marine organisms has concerned macrofauna [5][6][7][8], the impact of spilled oil on plants is potentially quite serious because plants are important determinants of the physical stability and resilience of coastal marine ecosystems [3], and of course photosynthetic organisms are responsible for producing much of the organic carbon that provides biomass and energy for the heterotrophic community. Although macrophytes such as Spartina alterniflora and Juncus roemerianus account for much of the resilience of salt marshes to perturbations such as hurricane storm surges, carbon and sulfur stable isotope studies have shown that the organic carbon in primary consumers in the Great Sippewissett marsh in Massachusetts and the Sapelo Island marsh in Georgia are derived about equally from Spartina and phytoplankton [9,10].…”