Currently five of the eight countries bordering the polar region are pursuing exploration and/or development of oil and gas resources in the Arctic [Canada, Greenland (Denmark), Norway, Russia, and the United States]. The changing environmental conditions in the Arctic may provide increased opportunity for development of these resources that were less accessible due to presence of ice in past decades and the improved technological advances for extracting petroleum resources. Activities of the petroleum industry are based on promulgated regulations set by each sovereign nation but there has been a move toward international cooperation and sharing of knowledge related to the technological development required to ensure safe drilling operations as well as spill response preparedness. International, federal, and local agencies from North America, Northern Europe, and Russia are in the process of developing baseline ecosystem and biodiversity assessments and research programs in order to better understand and protect the Arctic marine ecosystem and the communities that rely on these resources. For example, the Arctic Monitoring and Assessment Program (AMAP) has completed a significant effort in publishing comprehensive baseline information on Arctic geo-political activities and regulations, available drilling technologies, spill response initiatives, and potential environmental impacts (AMAP 2010). Additional cooperative research sponsored by joint industry programs (JIP) have augmented the knowledge base associated with the oil and gas industry activities (Sørstrøm et al. 2010; NewFields 2012). These efforts and convened workshops have integrated contributions from the scientific community, governmental agencies, public interest groups, and indigenous people of the Arctic.

Additionally, extensive field and laboratory studies have been conducted to examine the behavior and fate of oil and its potential effects on Arctic resources under the disparate seasonal conditions. Many recent studies have concentrated on understanding the influence of these harsh environmental conditions on the relative sensitivity of Arctic species to additional stressors, the success and rates of microbial degradation of oil compounds, and more recently the resilience of Arctic populations to recover from responses to those stressors. Similar to other parts of the world these investigations have increased our understanding of the basic behavior and movement of oil, its potential effects on VECs and the ultimate fate of released oil in various environmental compartments. The Arctic environment has added complexities resulting from seasonal patterns of ice and light that need to be considered to provide the foundation for development of strategic spill response strategies and evaluation of the environmental consequences of released oil that are very relevant today. Excellent comprehensive reviews have been published in recent years (Potter et al. 2012, Lee et al. 2012, SL Ross et al. 2010; USGS 2011).

The fundamental role of comparing the adverse biological effects of different response options in NEBA requires an information base that identifies VECs within multiple environmental compartments. The potential adverse effects and resiliency of these VEC organisms within each of these various compartments are then compared as a consequence of the OSR actions. These comparisons should examine the acute and long-term effects of spilled oil resulting from the impacts of various response options such as natural attenuation, surface-applied or subsea-injected dispersants, in-situ burning, and mechanical or naturally occurring containment methods followed up by recovery of spilled petroleum in Arctic ecosystems. Review and tabulation of published data, such as toxicity effect concentrations and population recovery times, is a key component of this review. However, the overall objective related to exploration and production projects in the Arctic is not only to tabulate this information or determine the most sensitive end-points that might be considered but to demonstrate the relative differences in the magnitude and duration of effects that might be observed at various ecosystem compartments associated with various response actions. As has been attempted for other regions where new exploration and production activities have been implemented, demonstrating these relative differences will require additional effort aimed at bridging the gap between relatively straightforward measurements of toxicity to arctic species and more complex investigations to assess ecosystem-level or population level impacts and recovery dynamics. This report considers the similarities and differences in species sensitivity between arctic and non-arctic species. To effectively monitor habitat recovery and identify ecologically relevant endpoints for remediation operations in Arctic regions there is a need to increase our knowledge on natural variability among populations and how that variability relates to vulnerability to petroleum exposure.

Prior to the granting of approvals for exploration and production activities, the public seeks increased assurances that industry and the various governmental entities have the capability to ensure safe exploration and extraction of oil as well as the capability to respond to oil spills. To meet these challenges a number of current and emerging oil spill countermeasure technologies have been identified for use in the Arctic. While use of different OSR methods can potentially reduce the impact of spills within the Arctic under various environmental conditions, not all options have been readily accepted by the public and regulators. Lack of endorsement of some OSR options is related to the perceived change in impacts and biodegradation rates that the use of these options in the Arctic marine ecosystem may bring. Several studies have been undertaken to address such concerns for different response measures; however, conflicting interpretations and conclusions impact stakeholders’ confidence. For example, the assumptions that dispersant treated oils are more toxic than undispersed oil, dispersants are more toxic than oil, dispersants reduce the ability of microbes to degrade oil, and Arctic species are more sensitive to oil than non-arctic species are incorrect although all of these assumptions may be proposed as facts by multiple stakeholders.

The purpose of the following section is to describe those key areas that the workgroup recommended for further evaluation based on their critical review of available information. The subjects for further consideration are grouped into major subject headings for this executive summary. Details of the recommendations will be found in each of the sections of the reports.

Arctic conditions influence the behavior and fate of untreated surface oil due to the low temperatures and the presence of different types of ice. Petroleum is generally immiscible in seawater and more so under colder temperatures. Surface oils with lower specific gravity accumulate on the sea surface and spread horizontally with the more volatile or soluble components quickly released into the air or into the water, respectively (NRC 1989; EPPR 2011). The surface oil also encounters disturbance by wind and wave action increasing the exposed surface area of the oil to the vertical transport processes of volatilization and solubilization. The wind and waves also adds water to oil creating oil/water emulsions that become more stable with time. The presence of broken ice with wind and waves enhances the disruption of the surface oil. These physical processes produce small globules of oil that may undergo further physical, chemical and biological weathering, creating aggregations of the heavier residual compounds that remain, eventually producing tar balls. In general, slicks formed in cold water are thicker with less exposed surface areas with reduced spatial coverage than the same oil released under temperate conditions. Laboratory trials have provided Information on key parameters that influence oil spreading under solid ice such as under-ice currents and ice roughness (Potter et al. 2012). In situations that the pour point of oil is above ambient temperature, the physical characteristics of the oil change dramatically with the wax components of the oil precipitating and forming a gel-like semi solid that is resistant to flow and spreading and which also restricts diffusion of volatiles through the slick, effectively reducing evaporation.

Untreated surface oils form slicks that are transported laterally by winds and currents and largely remain on the water surface and in the upper water column. The oil continues to spread on the surface of the ocean forming ribbons of slicks that rapidly spread to approximately 1 mm in thickness and are patchily distributed. Wind and waves break up and drive some of this surface oil into the water column in relatively large globules (>100 µm). The oil slick contains all of the chemical components of the spilled oil less those components that volatilize into the atmosphere or solubilize into the water column under the slick. The maximum concentration of oil is therefore contained in the immediate slick area, potentially exposing organisms that use the water near the air-water interface to the highest petroleum hydrocarbon concentrations that immediately follow a spill event.

The behavior and fate of released petroleum is an important consideration in understanding the potential effects of released petroleum and in evaluating the potential OSR options in the arctic. The spreading and weathering of petroleum in the arctic is complex, influenced by factors such as water temperature, local currents and wind conditions, the presence and absence of seasonal and multi-year ice, effects of pressure in deep water environments and seasonal changes in salinity during the Arctic spring. The presence of ice has been shown to slow the rate of spreading and weathering of surface oil, as well as affecting predictions of spill locations and trajectories. Migration of petroleum into brine channels or fissures in the ice can not only alter fate, but also the species that are potentially exposed and the exposure point concentration. At depth, petroleum is affected by increased pressures and decreased temperatures, resulting in phase shifts and changes in solubility as well as the dynamics of deep water currents and bathymetry. Key considerations included in the review were as follows:

• Cold water temperatures and the presence of ice can dramatically affect the weathering and natural attenuation of oil in the Arctic, but the ice can also trap oil so that OSR options and time available to implement the necessary response can be extended.
• Changes in behavior and fate of petroleum in deep sea environments associated with seeps and well blow-outs or leakage alter the bioavailability of oil components by allowing more volatile components to diffuse into the water where they may form clathrates altering the biodegradation potential and toxicity of those structures.
• Adhesion of oil to particulate matter and how this may affect the potential for uptake into tissues;
• The change in globule size and bioavailability of physically and chemically/OMA dispersed oil under Arctic conditions and,
• The behavior of oil in the absence and presence of ice and how it influences the selection of OSR options.

The microbial degradation potential of oil in the Arctic has been demonstrated and is as effective as this process occurring in lower latitudes when natural communities of Arctic microbes respond to the presence of oil. Microbial response to oil in the Arctic and deep, cold and dark waters are emerging areas of research. While microbial degradation in temperate waters has long been recognized, recent laboratory and field studies have documented microbial degradation of petroleum and dispersed petroleum in these extreme environments. Current research is using analytical chemistry, respirometry, genomics, transcriptomics, and proteomics assays to not only show the presence of oil-degrading species, but measure the response and results of microbial activity upon being exposed to oil. Key considerations included in the review are as follows:

• The presence and effectiveness of microbial communities to degrade oil in the Arctic (in open waters, in the presence of ice, along shorelines and in subtidal sediments);
• The characterization of the microbial community responses and gene expression associated with exposure to oil and aerobic and anaerobic biodegradation and use of hydrocarbons and organosulfur compounds associated with the unresolved complex mixture; and,
• The effects of biodegradation on the toxicity and availability of metabolites created during biological use of oil compounds and the changes that occur in toxicity and further biodegradation resulting from the more recalcitrant residual compounds of oil

There has been substantial research regarding the fate and effects of oil in the Arctic over the past 40 years; studies have been published in a number of different forums including peer-reviewed literature, technical reports, government studies and professional symposia. Additional data exists in a number of different languages, since research has been conducted throughout the North American, European, and Russian Arctic. Finally, important sources of data include emerging datasets from current research and older datasets that may not be as readily found in electronic search engines but nonetheless contain valuable information on environmental conditions and ecological resources. Consideration must also be given to the quality of data available for use. However, the most important aspect of making environmental consequence comparisons for OSR options is the appropriate framing of questions so that the consequences of response actions can be compared appropriately among all environmental compartments.

The physiological, morphological, and behavioral adaptations of Arctic species may alter their sensitivity to petroleum and treated petroleum. To address this concern there have been a number of recent efforts to characterize the sensitivity of Arctic species to treated and untreated petroleum. Evaluations have included pelagic and benthic species, as well as those in close association with the ice. Endpoints that have been evaluated include survival, growth, reproduction, and behavioral effects, as well as molecular, cellular, physiological responses. Custom experimental facilities have been developed for working with chemically and mechanically dispersed oil and water soluble fractions (WSF) of differently weathered oil. Methodologies have been developed by project team members to capture and maintain Arctic species of interest for controlled laboratory studies. The VEC species that have been evaluated to this point have been found to have sensitivities similar to non-Arctic species for oil exposure. Both field and laboratory data have also been integrated with population models to provide estimates of population-level effects from oil exposures (e.g. SYMBIOSES and fishery population analysis). Key considerations included in the review are as follows:

• Recent, historic and ongoing field and laboratory studies evaluating toxicity of petroleum and treated petroleum provided in Species Sensitivity Distributions to compare sensitivity of tested species.
• Different exposure scenarios facilitate different types of evaluations and can dramatically affect comparability of data. Spiked exposures followed by reducing concentrations of oil represent the exposures of stationary species or those present in the water column when oil is undergoing the initial spreading and dilution following the spill event or after application of dispersants or OMA. Exposures to constant concentrations of oil represent zones of concentrated oil observed with neuston associated species and life stages and marine mammals and seabirds that move in and out of the air/water interface. These more constant higher exposure concentrations can also occur when oil is concentrated at edges such as shorelines, convergence zones, and water/ice edges.    
• Endpoints found in the literature review range from body burden assessment to biomarker responses as well as mortality, growth, reproductive, developmental and behavioral responses. The diversity of potential end point assessments range from exposure assessment to end points that have a direct influence on estimating population level response to the oil components. For the purpose of this review, those responses that are better predictors of effects at the individual and population levels are the central focus. Mortality, growth and reproductive endpoints are those most closely associated with population level effects. Reviews on exposure markers will concentrate on demonstrating the relationship of the exposure marker to mortality, growth or reproductive endpoints.
• All toxicity assessments are surrogate measures used to predict the potential effects of oil spills on living resources. As such, data obtained using sub-arctic and temperate species representing different groups of organisms or different environmental compartments may also be useful in augmenting datasets with Arctic species. Recent comparisons of the relative sensitivity of Arctic and non-arctic species suggest that non-arctic species have similar sensitivities warranting a broader evaluation of much larger data sets.
• Additional testing of species that are long-lived, unique to selected habitat types and low in reproductive capacity that have not been evaluated in other regions have been identified during the reviews.

The toxicity of a mixture is characterized based on the analytical approach used to characterize the exposure. Variable conclusions regarding the relative toxicity of oil and water often can be tracked to the test waters being produced by different processes. The water accommodated fraction (WAF) is designed to only introduce the more soluble components into the water column while retaining the less soluble components on the surface of the water. The breaking wave water accommodated fraction (BWWAF) introduces additional physical disturbance, introducing more oil into the water as droplets with increased surface area exposure than occurs with the WAF allowing more of the soluble components to diffuse into the water from the oil droplets. The chemically enhanced water accommodated fraction (CEWAF) reduces the surface tension of the oil and produces much smaller droplets with much larger available surface area for diffusion of the soluble components of the oil. One of the objectives of the ecotoxicology section was to evaluate alternative methods of characterizing exposure.