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Environmental Effects of Spilled Oil and Response Technologies in the Arctic Report Executive Summary

Environmental Effects of Spilled Oil and Response Technologies in the Arctic

The comprehensive review of research into spilled oil and response technologies in the Arctic marine environment is based on more than 960 literature citations, compiled by a multi-disciplinary team with expertise in understanding arctic food webs; behaviour of oil in surface waters, at depth, and in ice; the effectiveness of oil spill response methods in cold-water surface and subsurface environments; toxicity; and models used to predict individual and population effects in arctic ecosystems.

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The comprehensive review of research into spilled oil and response technologies in the Arctic marine environment is based on more than 650 literature citations, compiled by a multi-disciplinary team with expertise in understanding arctic food webs; behaviour of oil in surface waters, at depth, and in ice; the effectiveness of oil spill response methods in cold-water surface and subsurface environments; toxicity; and models used to predict individual and population effects in arctic ecosystems. 

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Executive Summary

Photo 1-1. Polynya (MODIS)
Photo 1-1. Polynya (MODIS)

The Arctic maritime region is comprised of the Arctic Ocean, six marginal seas, and six deep water basins. The Arctic Ocean is a beta ocean, i.e. it is dominated by a strong halocline which acts to retard mixing and vertical flux of biotic and abiotic materials. The main influx of water is derived from the Atlantic Ocean; waters entering via the Chukchi Sea are minor in comparison due to the shallow sill depths in the areas of the Bering Strait and Chukchi Sea. Most oil and gas production, major shipping routes, and population centers are located near the continental shelf regions, often coincident with the specialized environments of polynyas (free waters within ice) and freshwater discharge from several major river systems. Continental runoff is a major source of freshwater, terrigenous materials and nutrient loads to the Arctic seas. The Arctic Ocean surface layer (ASL) is generally insulated from the warmer and higher salinity bottom water (Atlantic water layer; AWL) by a well-developed halocline (cold halocline layer, CHL). The halocline is a strong barrier to upward mixing by turbulence, and consequently most of the ocean heat flux in the central basins of the Arctic is generated by solar heating through open leads and thin ice during the summer months. Sea ice nomenclature describes age (thickness as it ages), forms (e.g. pancake or brash ice, floes, icebergs), and concentration (i.e. relative ice/sea coverage) [Tables 1-1 and 1-2]. Average multiyear sea ice distribution and thickness changes over time; estimates of ice cover for February/March 2004 - 2008 and February/March 2012 are compared in Figure 1-1. Ice provides habitat for ice algal communities and enhances food resources, whereas solid ice fields may sufficiently retard solar irradiance to reduce primary production. The processes of ice production, salt flux, and heat transfer from leads and polynyas are important contributors to biological productivity and the larger scale climate events in the Arctic, in addition to the overarching seasonal changes in degree of solar radiation. Biological productivity hinges upon solar irradiance and nutrient availability; the availability of these two resources are regulated by the albedo of ice and snow surfaces and the salinity stratification of the Arctic waters.

Table 1-1. Sea ice Formation (Environment Canada 2005)


New Ice

Frazil Ice

Grease Ice


< 10 cm

Fine spicules or plates of ice

Ice crystals have coagulated

Snow, saturated and mixed with water

Nilas, Ice rind

< 10 cm

Young Ice

Grey Ice

Grey-white ice

10 - 30 cm

10 - 15 cm

15 - 30 cm

First-year ice

Thin first-year ice

Thick first-year ice

≥ 30 cm

30 - 70 cm

> 120 cm

Old Ice

Second-year Ice

Multi-year Ice


Variable to 5 m

The changing physical environment in the Arctic consists of extremes in temperature, amount of light, and weather conditions that act upon the pelagic open waters and convergence zones (shorelines, sea surface layers, ice water interfaces, sediment water interfaces, and water convergences). Convergence zones form an environmental compartment (EC) of the Arctic where valuable ecosystem components (VECs) congregate (see Section 2) providing opportunities for alternate exposure pathways and responses resulting from different modes of toxic action (See Section 6). The physical environment also influences the fate of oil (see Sections 3 and 5) and provides opportunities for alternative oil spill response (OSR) actions (see Section 4). The physical environment needs to be well understood because it sets the stage for minimizing short and long term consequences of applying alternative OSR options (see Sections 7-9). For these reasons determining the location of more stable convergence zones (shorelines and sediment water interface environments) and understanding the variations in the location of more mobile convergence zones (ice water interfaces and current convergence zones) are key components in the selection of OSR options to reduce the consequences of an oil spill.

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Figure 1-1. Changing distribution of ice cover (NSID) (Colors indicate ice thickness in meters; blue = 1m, red=5 m)

Table 1-2. Relative ice concentrations [Adapted from Environment Canada 2005] 

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<1/10 Open water

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8/10 Close pack/drift ice

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3/10 Very open drift ice

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9+/10 Very close pack

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6/10 Open drift ice

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Compact/Consolidated Ice

Executive Summary

Photo 2-1. Arctic field study (Jack D Word)

Photo 2-2. Arctic field study (Jack D Word)

Photo 2-3. Arctic field study (Jack D Word)

Photos 2-1, 2-2, 2-3 Arctic field study (Jack D Word)

In order to minimize the potential impacts of an oil spill, valuable ecosystem components (VECs) that potentially become impacted should be indentified. Each compartment where oil might end up contains its own set of VECs with their own sensitivity and resilience to oil. Apart from the identification of VECs, their distributional patterns by life stage within environmental compartments (ECs) both in time and space are of importance. Except for the multi-year ice environments or species that are fixed to demersal or shoreline environments, the organisms and their young undergo seasonal migratory patterns with many species occupying Arctic ECs on a temporary basis. While these distributional patterns for migratory species and resident species are becoming better known, their locations during an oil spill needs to be characterized so that the optimum spill response options with the least amount of environmental consequences to VECs can be identified. Arctic specific VECs tend to congregate at interface habitats like the surface layers at or near the air/water interface (SML), ice edges and under ice environments, polinyas, sediment/water in demersal nearshore and offshore locations, shorelines, and convergence zones for different water masses. Key topics for further study would focus on the importance of these interface habitats for the diversity and long and short term functioning of Arctic ecosystems. Once the main VECs have been identified, research should establish the seasonal distribution patterns of the life stages and population levels of VECs within each EC, especially within the interface environments. Resilience of VECs determines to a large extent the long term population level effects that would occur after an oil spill. For identified VECs a proper and generic resilience metric should be developed so that relevant information on VECs can be applied in net environmental benefit analysis (NEBA) decision making.

Executive Summary

Photo 3-1. Marginal Ice (NOAA)
Photo 3-1. Marginal Ice (NOAA)

Oil is composed of many compounds resulting in mixtures containing a wide range of volatile, semi-volatile, soluble and more recalcitrant compounds. During a spill some of these oil components separate from the oil mixture by evaporation into the air or by solubilizing into the water leaving the more recalcitrant compounds in the weathered oil product where wind and wave action adds water to the mixture (emulsification). Spilled oil in the Artic undergoes the same processes occurring in environments throughout the world. However, the colder temperatures increase the viscosity of oil resulting in slower spreading rates and increased thickness of oil on the sea surface. The slower spreading rates also reduce the area covered by surface oil which may be further reduced by the presence of ice and snow. The thicker layers of oil on the sea surface decrease the surface area of the oil that is available for losses due to evaporation or solubilization and decrease the potential for emulsification especially in heavy ice with dampened wind and wave action. Furthermore, oil that is encapsulated in ice during the fall and winter provides an extended period for oil spill response actions (OSR) to proceed prior to and during spring melt. The most efficient biodegradation of oil occurs within the water column and, to a somewhat lesser degree, at the sea surface. Maximizing the surface area of the oil will increase the efficiency of microbes to reduce oil concentrations. Biodegradation of oil present in or on shorelines or encapsulated in ice is less efficient. The confinement of surface oil along the edges of ice can result in both the encapsulation of oil in freezing ice or the ‘booming’ of oil along ice edges increasing the opportunities for response actions.

Evaluation of the transport and fate of oil residues that remain after application of an OSR is a key component to assessment of long-term ecosystem consequences. In order to formulate a proper net environmental benefit analysis (NEBA) decision framework for Arctic oil spill response it is important to understand the differences in transport and fate of the remaining oil components after OSR actions to and within Arctic environmental compartments (ECs). Important processes include physical, chemical, and biological complexities associated with the transport, fate, exposure, and effects of oil and OSR residuals in the Arctic environment. It is crucial that the underlying processes are understood in a quantitative as well as a qualitative way. Key recommendations therefore include the development of a better understanding of environmental compartment attributes that affect the dissolution, mineralization and biodegradation of oil especially at ice/water interfaces and that decrease or increase resiliency.

Executive Summary

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Photos 4-1 – 4-4. OSR deployment (NOAA)

Four main oil spill response (OSR) strategies exist: natural attenuation, mechanical recovery and containment, in-situ burning, and physical and chemical dispersion of oil. All four are often used in combination and can be used in the Arctic. Selection and application of an oil spill response strategy should be based on both the effective removal of oil for the specific oil and weather conditions and consideration of the information on potential impacts to valuable ecosystem components (VECs) since application of response options will influence the fate of oil in the environment and concomitantly potentially alter the impact to different VECs. The influence of chemically and/or physically dispersed oil on pelagic species is well documented, but biological responses to oil at interfaces (air/water, ice/water, sediment/water and shorelines) has been less documented. Understanding the consequences of OSR actions on the impacts and resilience of VECs within these interface layers needs to be further developed in order to strengthen our ability to select a preferred OSR strategy under each spill scenario using the net environmental benefit analysis (NEBA) process (see Section 9).

Environmental effects related to OSR options have been studied extensively. In order to readily synthesize information that is already available on exposure potential, sensitivity and resilience of VECs, this information should be collated for each OSR technology and corresponding VECs that these technologies potentially impact to improve application of NEBA processes in the Arctic. This compilation of technical data will also facilitate the identification of remaining uncertainties.

Executive Summary

Microbial communities rapidly adapt to increasing abundance of hydrocarbon utilizers in all aquatic environments that have been studied.

Carbon utilization by these microbial populations mineralize complex mixtures of carbon compounds to CO2, degrade complex compounds to smaller molecules, and directly place these carbon atoms into the tissues of the microbial populations.

Microbial communities in the Arctic are adapted to life in this extreme environment and rapidly respond to carbon rich but nitrogen poor petroleum resources. Many of the organisms are unique to this environment while others are similar to those species that also respond to petroleum in other parts of the world.

The speed of microbial utilization of oil is primarily related to the amount of surface area exposed to aerobic processes. Thick layers of oil, physically weathered oil, or oil isolated to less aerobic environments undergo biodegradation more slowly than dispersed oil.

Executive Summary

Photo 6-1: Boreogadus saida (Lionel Camus)
Photo 6-1: Boreogadus saida (Lionel Camus)

This section presents a review of the current knowledge on the effects of oil and treated oil on aquatic Arctic organisms, focusing on available ecotoxicology data from peer-reviewed literature (includes 85 published studies and 14 papers in review). These studies were conducted with a variety of media, test organisms, and experimental designs: 

  • Crude oil was the main test media 
  • Test organisms represented 44 species from 11 taxonomic groups. Where possible, the test species represent vital linkages in the Arctic trophic web (valuable ecosystem components or VECs) 
  • The various experimental designs included spiked and continuous exposures of fresh and/or weathered oil in the presence or absence of dispersant; different preparations of exposure media [water soluble fraction (WSF), water accommodated fraction (WAF and chemically enhanced WAF) and a newly introduced method of oil-in-water dispersions (OWD)]; and reporting of nominal or quantitatively measured exposure concentrations. Results were typically reported in terms of total petroleum hydrocarbons (TPH) or as toxicant-specific compounds (such as naphthalene and its congeners). 

The majority of the toxicity experiments were conducted in laboratories, very few ecotoxicity studies have been conducted with Arctic field experiments. These disparate experimental designs and particularly methods used in quantifying data can lead to variable interpretations of relative toxicity and species sensitivity estimations brought forward to ecological risk assessments and net environmental benefit analyses. Because of the relative difficulty in conducting Arctic toxicology studies at extremely low temperatures with authentic Arctic species, there are relatively few comprehensive investigations. However, relatively recent attention has focused on the issue of relative sensitivity of Arctic species to temperate species and several assessments have similarly concluded that arctic and temperate species show little difference in relative sensitivity when toxicity studies were conducted with similar methodologies. 

Executive Summary

Photo 7-1. Young Arctic cod congregating under ice
Photo 7-1. Young Arctic cod congregating under ice

Assessing the transport of oil and its components and predicting the toxicity of the mixture to exposed organisms is relatively well developed. However, for a NEBA asessment the initial impact of oil and OSR techniques on individual organisms is only a small part of the overall evaluation that needs to be made. Species sensitivity together with parameters like exposure potential, population growth rates, reproduction capacity, population elasticity, and recovery protential will determine the overall population resiliency. Resiliency of the most important Arctic VECs should be further studied and assessed making this a crucial input parameter for NEBA analysis. Population effects modelling can help to study processes that determine populations resilience. Areas needing further development include the following: 

  • Develop resilience metrics for key Arctic populations 
  • Examination of other modes of action including fouling, inhalation exposure and respones, and epithelial tissue exposure and disruption will add to model accuracy. 
  • Extrapolate predicted toxicity effects to populations of key ecosystem components, requiring an assessment of population dynamics (e.g., age class distribution, sensitivity of different age classes, fecundity measures, distribution and connectivity of populations of key species). 
  • Compare natural annual or multi-year variation in populations of VECs to the projected impacts of oil spill residuals on VEC populations. 
  • Comparative evaluation of each oil spill response option (OSR), particularly in terms of on resilience of the environmental compartment (EC) and valuable ecosystem components (VECs). 

Executive Summary

Photo 8-1
Photo 8-1

Contaminant concentrations, persistence and bioavailability influence the potential for impacts on species living within the different environmental compartments. The interface environments (e.g., ice/water, air/water and shorelines) may be the most critical exposure locations where organisms may come into contact with oil at the highest concentrations, e.g. resulting in increased mortalities due to fouling or smothering. Near term biological effects of oil on pelagic invertebrates and fish is relatively well understood not only in the Arctic but also in non-Arctic environments. Near term and longer term impacts on organisms that live along interfaces (air/water, ice/water, sediment/water and shorelines) is less understood not only in the Arctic but also in non-Arctic environments. In general, the biological attributes that control resilience (or recovery potential) within any faunal group include: size or percentage of population impacted, reproductive potential (progeny produced per unit of time), migratory supplementation potential, and the influence of linked effects to higher trophic levels. Resilience assessment is important for properly assessing recovery. It is recommended to further study the elements that determine resilience of Arctic ecosystem components in order to reduce uncertainties in NEBA decision making. 

Executive Summary

Photo 9-1. Oil spill recovery (Gina Coelho)
Photo 9-1. Oil spill recovery (Gina Coelho)

Net Environmental Benefit Analysis (NEBA) is not a new concept and has been broadly implemented to prioritize and guide environmental remediation and restoration efforts aimed at recovering aquatic and terrestrial habitats from excessive contaminant exposure. A NEBA encompasses an environmental risk assessment including identification of sensitive or critical species and/or habitats, evaluation of resource utilization, and a detailed comparison of recovery and restoration plans to ensure optimum benefit is obtained. The focus of this conceptual framework needs to be modified somewhat to effectually lead oil spill response and recovery decisions in the diverse pan-Arctic regions. Our knowledge of Arctic biodiversity and the unique environmental compartments under the severe and changing climatic conditions is increasing rapidly. Information on the complexities of species migration, reproductive patterns, food web dynamics, and toxicological response patterns to oil is enabling at least preliminary comparisons with more temperate environments and the corresponding larger knowledge base. 

Although recent data indicates that toxicological responses fall within similar ranges as temperate and tropical species, potential long-term repercussions from a substantial oil discharge and selection of an oil spill response (OSR) option is less known in terms of a species or population-level impact. Environmental compartments (ECs) are impacted by oil spills at different levels depending on the OSR action(s) that are implemented. The objective of an ecosystem consequence analysis is to maximize the protection of ECs and keystone species that are most sensitive to the residuals of these response actions. 

Unlike oil discharges on land, oil discharge into aquatic systems can become highly mobile and the fate of oil will be influenced by the OSR utilized. Additionally, Arctic environmental conditions influence the behaviour of oil itself: 1) volatilization of lighter fractions may be retarded; 2) Arctic sea ice may sequester and impede the spread of surfaced oil; and 3) extreme cold temperatures may alter natural biodegradation rates. Moreover, extreme winds, pressure ridge formation, and/or winter darkness may force cancellation of certain OSR operations other than natural attenuation. It is likely that spill response decisions for the Arctic may include a step-wise application of multiple OSRs. However, it appears likely that attributes of resiliency to naturally occurring oil seeps and intrinsic abilities of the Arctic populations to respond to seasonal challenges demonstrated by natural inter-annual changes in population recruitment patterns may signify an aptitude for assimilating oil residuals in a timely manner. This section summarizes traditional elements in a NEBA and points out how application under arctic conditions presents new challenges. In the future, the inclusion of an additional paradigm to typical NEBA approaches, i.e. a consideration of long-term ecosystem consequences of utilizing one OSR versus another will be paramount to successful preservation of areas receiving oil in the Arctic. We envision development of an Arctic response consequence analysis tool will help us achieve these goals. 

Executive Summary