An extended ice-free season has expanded opportunities for oil and gas exploration in the Arctic and has increased the need to better understand the environmental consequences of oil spill response alternatives under Arctic conditions. Oil spill counter measures include physical removal, the application of chemical or physical dispersants, and in-situ burning, as well as emerging technologies such as chemical herders and oil-mineral aggregates (OMAs).  Oil spill responders need to quickly evaluate the best treatment options for the event at hand that will cause the least amount of environmental perturbations.  This requires a multi-tiered assessment of interactive attributes and processes, such as:

• What are the chemical components of the oil spilled? How would the toxic fraction be characterized?
• What volume of oil was released and what is the probable fate of the oil if untreated? – If treated with chemical dispersants or oil/mineral aggregates?
• What VECs might be impacted by short- and long-term releases?

Each of these different alternatives may alter the fate, bioavailability and potential environmental impacts of a release.  Numerical models are available to describe the fate and spreading of the oil (e.g.DREAM, OSCAR) or to predict the population levels effects of a release (e.g. SYMBIOSES).  However, in order to link the composition and fate of released petroleum to predictions of the potential population level impacts, toxicological data is required (see Figure 6-1).   The oil and gas industry is compiling and centralizing an adequate ecotoxicity database to be used as an integral part of forecasting probable effects caused by an oil spill in order to best mitigate the environmental damages, both short term and long term.  Knowledge about the relative toxicity consequences of each scenario is necessary to ensure that the most effective spill response option is chosen.  Often the most effective treatment may be a combination of spill response options. 

This section reviews the current knowledge on the effects of oil and treated oil on aquatic Arctic organisms, focusing on available ecotoxicology data available in the peer-reviewed literature. Approximately 85 peer-reviewed publications and 14 papers in preparation have been reviewed. These publications evaluate the sensitivities of 44 species from 11 different taxonomic groups. Data on 14 algae species and six bacteria species could be identified in the literature. Additionally, four papers address effects on communities.  Nine papers reported toxicity studies conducted at relatively high temperature (i.e. 10^oC) with boreal species that occur in the Arctic for a portion of their life history. Eight papers have been identified reporting baseline levels of biomarkers and/or petroleum related contaminant levels. The majority of the studies have been conducted with crude oil or single polycyclic aromatic compounds. One paper described a field trial of releasing oil in the field in order to study the short and long term impact with or without any response. There is a large variety in exposure methods, oil type and treatments, complicating the interpretation and application of these data in risk assessment procedures. Different exposure systems and exposure quantifications may lead to different interpretations on the relative toxicity of oil and treated oil. 

Figure 6-1. Toxicity empirical data (outlined in red) are used in advanced predictive models (e.g. PETROTOX, EPISUITE, QSAR, OSCAR, TLM)

There is a substantial body of data regarding the toxicity of oil to aquatic organisms.  A majority of the existing toxicity data is for acute lethality of oil-water mixtures to temperate species (DeHoop et al. 2011; Word and Gardiner In prep).  More recent research efforts have begun to focus on Arctic test organisms and have included sublethal endpoints to acute and chronic exposures, as well as acute lethality.  The following paper presents a summary of existing toxicological studies on the effects of oil and treated oil on pelagic, ice, and benthic community species.  This review includes toxicological studies on Arctic and boreal species that are available in the scientific literature, including peer-reviewed journal articles, published books, and meetings proceedings.  Scientific papers that have been accepted for publication were also included.  Papers that have been submitted but have not yet been accepted are referred to here, but were not included in the summary data tables.  Reports published in the peer-reviewed literature and in books offer the advantage of being openly available as well as representing a high level of professional review to ensure data quality.  References were further evaluated for the use of acceptable test methods and controls, including use of standardized methods for test media preparation and exposure and analytical chemistry, where present.   Our review focuses on species that lend themselves to controlled laboratory toxicity tests with oil and treated oil using standardized test methods.  For aquatic species this is typically limited to fish and invertebrate species.  This review does not include seabirds and mammals.  Laboratory exposures to oil and treated oil with upper trophic levels are problematic due to complex routes of exposure, long term response times, and ethical considerations.  In a review to oil toxicity on sea birds, Leighton (1993) notes that there are three different ways in which such oils may affect birds.  External contamination of plumage is the most common form of exposure. Feathers are coated in oil, they become matted, and lose their critical properties of water repellency, insulation, and flight. Death results from combinations of hypothermia, starvation, and drowning.  Avian embryos are highly sensitive to oil that contaminates the egg shell; amounts as little as 1–10 μL are lethal to embryos during the first half of incubation. Birds ingest oil when preening oiled plumage or ingesting oiled nutrients. At least three toxic effects of ingested oil are well documented: a nonspecific response as a stressor that is additive or synergistic with those of other stressors, impairments in reproduction ranging from lowered fertility to abandonment of reproductive effort, and severe oxidative damage to red blood cells. The effect of oil pollution on bird populations is very difficult to document and is likely to remain uncertain due to the many ecological factors that may occur in association with an oil spill event.

Similarly, the mammalian VECs (baleen and toothed whales, ice seals, polar bears, and walruses) cannot be studied using standard laboratory testing models.  Much of the data regarding oil and treated oil effects on marine mammals rely on field exposures during spill events in uncontrolled exposures (Geraci and St. Aubin 1989).  Furthermore, effects occur over a long period of time and rely more sub-lethal effects based on biomarker studies.  Important routes of exposure can include dermal exposure, inhalation at the sea surface, and ingestion.  As with seabirds, dermal contact is an important route of exposure for marine mammals (Engelhardt 1983; NRC 2003).  Baleen whales may also be impacted by oil fouling of the baleen (Braithwaite et al. 1983).  Feeding studies with captive seals (Engelhardt 1982) have been associated with changes in blood chemistry and immune system function.

There is a body of evidence that Arctic species are not more sensitive than temperate species to petroleum related compounds (single PAH, chemically dispersed, physically dispersed) when using acute toxicity tests. Moreover, there is a growing body of information that indicates that chemically dispersed oil may not be more toxic than physically dispersed oil. Some studies reveal that species assemblages and community functioning respond differently in the Arctic in response to oil exposure when compared to temperate communities. More effort could be devoted to study subtle long-term effects at the community and population level either by carrying out higher tier exposure studies or by extrapolating individual responses to population and community level effects using predictive models.

The methods for evaluating the toxicity of oil-water emulsions, physically and chemically dispersed oil and oil in sediment are varied and have evolved over the recent decades.  While there are accepted methodologies for test media preparation and exposure, there is still a wide range of methods applied.  Methods for preparing petroleum-water mixtures for toxicity testing were first developed by Anderson et al. (1974) and have been modified by several investigators to create more consistent petroleum-water and petroleum-dispersant mixtures.  Other guidance documents, such as those provided by UNESCO, the American Society for Testing and Materials (ASTM), and the US Environmental Protection Agency (USEPA) provide standardized test methods that may be adopted for conducting toxicity tests with fish and invertebrates.  The Chemical Response to Oil Spills Ecological Effects Research Forum (CROSERF) program developed and published methods for creating preparation of WAF as well as CEWAF and conducting toxicity tests (Aurand and Coelho 2005).  Since the procedures were put forth by the CROSERF program, they have been critically reviewed by Barron (2003), Clark et al. (2001), and Nordtug and Oistein (2007).  Barron (2003) suggested changes to the CROSERF methods that would make exposures more suitable for understanding effects in open, cold-water environments.  Other groups (SINTEF, Akvaplan-Niva, and NOAA) have developed methods for creating oil-water dispersions (OWD).  Many of the studies summarized here have included methods developed by CROSERF with the modifications to better emulate conditions in the Arctic.  A summary of several key considerations are presented in the following sections.

The type of exposure that is used in toxicity evaluations may influence the effect-level estimates for individual species. Two different types of exposures, continuous and spiked exposures, are commonly used in laboratory evaluations of oil and treated oil. Continuous exposures are conducted with a constant dose throughout the test period. This is accomplished by either performing renewals with newly prepared test media or by performing static tests. Continuous exposures represent a maximum exposure to test media and represent field conditions where the petroleum concentrations are expected to be more or less constant over the period of several days to weeks. Spiked exposures are conducted with the doses that are highest at test initiation and then decrease throughout the test period. A number of researchers have noted that spiked exposures better mimic the petroleum exposures in the water column, particularly when chemical dispersants are used (Singer et al. 1991; Gardiner et al. 2013, in press; Fuller et al. 2004). When conducted side-by-side, continuous exposures typically show lower LC50 or EC50 estimates (greater toxicity) than spiked exposures (Singer et al. 1991). It is therefore important to consider the toxicity exposure method and the spill scenario when applying toxicity data to ecosystem-level evaluations of OSRs for different environmental compartments. 

The test media can be prepared in a number of ways, with each method having advantages and disadvantages. In the following literature review, water-soluble fractions (WSF) are typically created using a generator column or gravel column. In such preparations, water is pushed through an oil-coated matrix, with the soluble fractions “dosing” the seawater. Recently, SINTEF developed a droplet generator that allows for the formation of physical dispersions with neutrally buoyant droplets of a diameter similar to chemically dispersed oil. This allows for a more direct comparison of physically and chemically dispersed oil. 

Water-soluble fractions (WSF) represent the soluble fractions of oil and are typically created using a generator column or gravel column. In such preparations, water is pushed through an oil-coated matrix, with the soluble fractions “dosing” the seawater. Oil is coated on to granular materials (e.g. gravel, or glass beads) and contained in a column having an entry port and exit port to accommodate the flow of filtered seawater through the column. Generally, fresh oil is added initially and naturally weathers over time. Adult female Calanus glacialis and Calanus finmarchicus were exposed to water soluble fraction (WSF) crude oil in a continuous flow experiment; hatching success of eggs and production of fecal pellets were assessed (Jensen and Carroll 2010). The WSF solutions were prepared by pumping filtered seawater through columns containing glass beads coated with crude oil (Duesterloh et al. 2002; Camus and Olsen 2008). Chemical analyses of WSF for both experiments included polynuclear aromatic hydrocarbons (PAH; based on USEPAs 16 priority compounds). Authors noted that for the C. glacialis experiment only 4 PAHs of the 16 analytes measured exceeded detection limits in the low and high dose treatments (naphthalene, fluorene, phenanthrene, and acenaphthylene). The low dose (3.6 μg/L PAH) treatment had a much lower naphthalene concentration relative to the high dose treatment. Total concentrations of 16 PAHs gradually decreased over time (naphthalene decreased more rapidly whereas heavier compounds were more stable). Results from C. glacialis tests showed no significant differences between highest treatment (10.4 μg/L PAH) and controls for cumulative egg or fecal pellet production; however, hatching success was significantly reduced. Exposure of C. finmarchicus to 7.0 μg/L PAH reduced feeding efficiency of adults. 

Water-accommodated fractions (WAF) are a preparation method where oil is placed over a volume of seawater and mixed with a magnetic stirrer, generally for 18 to 24-hours. The amount of mixing energy may vary, but is typically adjusted such that visible oil droplets do not become entrained in the seawater. The mixing period is then followed by a “resting” period which allows larger oil droplets to rise to the surface. The test media are removed via a port at the bottom on the mixing container. WAF preparations are intended to include the dissolved fraction and the smaller, neutrally buoyant oil droplets. A dispersant can be added to the WAF preparation to create a dispersed WAF or Chemically-Enhanced WAF (CEWAF). Methods for preparing petroleum-water mixtures for laboratory toxicity testing were first developed by Anderson et al. (1974) and have since been modified by several investigators to create more consistent petroleum-water and petroleum-dispersant mixtures that are more representative of field conditions (Singer et al. 2000, Nordtug and Oistein 2007, Aurand and Coelho 2005; Barron 2003, Clark et al. 2001). Many of the studies conducted with Arctic species have been conducted with WAF or CEWAF preparations. 

An additional method has been developed to create oil-in-water preparations that may better approximate the distribution of smaller, neutrally buoyant oil droplets in the physically dispersed oil. Nordtug et al. (2008) present a method for continuous and predictable in-line production of oil dispersions with defined size distribution of oil droplets based on theoretical models for droplet formation. Test solutions enter the experimental chamber via multiple nozzles which create turbulent dispersions of oil droplets and water soluble components. The mean droplet size and the droplet size distribution was determined by a combination of energy input (flow rate) and the number of nozzles used. The system enables simultaneous comparison between the effects of different concentrations of the dispersion and their corresponding water soluble fractions and the net effects of the oil droplet fractions. Flow-through into each individual exposure chamber was controlled by pumping exposure solution out near the surface, causing fresh solution to flow passively by entrainment into the chamber at a corresponding rate. Chemical measurements have been used to verify concentrations and quality of the dispersions and water soluble phases. The hydrocarbon profiles of the oil and the dispersions were very similar, whereas only a fraction of the components are in the dissolved phase. Tests with early life stage cod larvae (Gadus morhua) and copepods (C. finmarchicus) have been conducted with OWD preparations, allowing for evaluations of both the toxicity associated the dissolved fractions as well as adhesion of particulate oil (Olsvik et al. 2010 and Melbye et al. 2006). 

The type of oil used in test media preparation may affect toxicity, as well as factors like fresh or weathered oil is used. After oil is released into the environment, its chemical and physical characteristics change through processes of: evaporation, dispersion, emulsification, dissolution, oxidation, and biodegradation. The weathering process is described in more detail in other sections of this report. For laboratory toxicity studies, typically weathering is simulated by evaporation causing a loss of the most volatile hydrocarbons and a reduction in the oil volume. The volatile hydrocarbons generally represent the more acutely toxic fractions of oil. It is important to note that the evaporative weathering only accounts for one portion of the weathering process. Many studies are conducted with fresh oil as it represents a worst-case scenario, particularly for acute toxicity estimates. There have been several toxicity studies with Arctic species that have used weathered oil in test media. 

Photo 6-2: Preparing for bioassay test under Arctic conditions (William Gardiner)

The manner in which exposure concentrations are presented can also affect the usefulness and comparability of data. Measured effects concentrations may be reported as a percentage of the original test media (nominal concentrations) or as measured concentrations. Toxicity reported as nominal concentrations represent a percentage of a particular loading rate and are most closely tied to the laboratory method. Nominal concentrations are perhaps the most difficult data to relate to field data or to use in models, unless coupled with measured concentrations of hydrocarbons. Measured concentrations can include several analytical methods for expressing petroleum hydrocarbons. TPH are the most commonly reported measure for both laboratory and field studies. As such, they allow for comparisons between lab and field exposures. However, TPH includes many petroleum compounds that do not contribute to toxicity. This can be a significant source of variability and error when using toxicity data in models. Total petroleum aromatic hydrocarbons (PAHs) are believed to be more specific to the toxic fractions; however, this measure also includes non-toxic fractions. Finally, toxicity may be expressed in terms of a specific compound, such as naphthalene or 2-methylnaphthalene. While this removes the concern of including too many compounds, it also may not account for toxicity associated with secondary hydrocarbons. In many cases, it is important to understand how data are being applied and their limitations. 

Historically, the toxicity of oil, dispersed oil and single compounds was evaluated using continuous exposures, with test concentrations remaining more or less constant over the test period. In some cases, such as dispersed oil in open water, this may overestimate exposure. In such cases, spiked, or declining exposures have been used to better simulate field conditions (Photo 6-2). Each exposure method may be appropriate depending on the application of the data (e.g. spiked exposures for dispersed oil and continuous exposures for oil in ice). This topic is dealt with later in this chapter. 

Where possible, test species that are included in toxicity studies are valuable ecosystem components (VECs) that represent the relevant environmental compartments potentially exposed to oil or treated oil. The VECs that were selected for the Arctic are discussed in Chapter 2. However, species that are VECs do not necessarily lend themselves to toxicity studies. Characteristics for suitable test organisms include the following: 

• A sensitivity to oil and treated oil; 
• Relative abundance and an availability for collection or culture; 
• The ability to withstand laboratory handling; 
• Meaningful and measurable endpoints over the time period of the study; 
• Native to the site-specific conditions (e.g. cold water). 

There were toxicity data for a number of Arctic VECs including copepods, Arctic and Atlantic cod, sculpin, capelin, ice amphipods, benthic amphipods, crab, shrimp, and echinoderms. While there were toxicity data for a number of the VECs, in many cases the data are limited and endpoints. The suitability of data for conducting ecosystem-level evaluation of different OSR alternatives is considerably more limited, with copepods and Arctic cod having the most complete data sets. 

Endpoints, or measures of effect, are dependent upon the test organism and the study goal. In general, toxicity is expressed as a dose-response to a certain concentration of test media. The most common endpoint is mortality, with the median Lethal Concentration (or LC50) being that concentration of test media that will cause 50 % mortality to the exposed organisms. Sub-lethal effects such as growth or reproduction are usually expressed as a median Effect Concentration (EC50) representing the concentration at which 50 % of the exposed organisms have a significant change in those end-points. These indicators are often extrapolated to an assessment endpoint depending on the purpose of the assessment. Effect concentrations can for example be used to assess environmental threshold values like a Predicted Environmental No-effects Concentration (PNEC) or to construct a species sensitivity distribution used to assess the fraction of species that is at risk. Other common measures of toxicity include No-observed Effect Concentrations (NOEC) and Lowest-Observed Effects Concentrations (LOEC). 

In order to evaluate population or ecosystem level effects, there are a variety of extrapolation models that utilize the toxicity endpoints (e.g. LC50) as input. Population models coupled with field-collected data on the distribution, abundance, natural mortality and fecundity are used to predict population level effects associated with modeled exposure scenarios. Simulated exposures using physical fates models such as the Integrated Oil Spill Impact Model System (SIMAP) allow for different spill and response scenarios to be evaluated. Gallaway et al. (2007; 2013, in prep) used toxicity data from laboratory exposures of Arctic cod to WAF and CEWAF, field collected data from the western Beaufort Sea, and the SIMAP model simulations to predict potential population effects from physically and chemically treated oil in open water. 

Another approach to population models is to incorporate many ecological components of an ecosystem to predict the potential cascade effects and repercussion in the trophic chain over time (Peterson et al. (2003). An example of such a model is the SYMBIOSES model that is under development for the Barents Sea (Carroll and Smit 2011; DeLaender et al. 2010). The main objective of such an impact analysis tool is to examine extent of effects on a VEC (e.g. larval Arctic cod) that result in significant effects on fish recruitment and stock size. While this is similar to the goal of the model used by Gallaway et al. (2007; in prep), this ecosystem approach considers indirect effects of a discharge that originates from ecological interactions. Data used to quantify effects of oil associated compounds on the Arctic trophic linkages include many food web links from the planktonic community to fish larvae and adult fish. 

The SYMBIOSES model integrates food web analyses of the structure and functions of the whole microbial and plankton community of the Barents Sea (bacteria, protozoa, phytoplankton, zooplankton, fish eggs and fish larvae) in terms of response to oil; for instance using an in situ mesocosm experiment. Today, such mesocosms exist and can be used in boreal or Arctic ecosystems to address plankton community responses to petroleum discharges (Hjorth et al. 2008). The mesocosm could be deployed in the Arctic waters during the ice free season especially at the peak of the phytoplankton bloom when the ice break-ups occur. While mesocosms represent an increase in the level of complexity of exposure design, they are subject to similar artifacts as laboratory studies. Interactions observed in the laboratory should be confirmed with field data when possible. 

Empirical toxicity data may also be used as part of predictive environmental fate and effect models that aim to integrate the chemical relationship of petrochemicals with prevailing biological processes (Figure 6-1). To form a holistic ecosystem perspective, complex relationships have been simplified according to basic assumptions, such as: 1) Hydrocarbon block and Quantitative Structure Activity Relationship (QSAR) models, i.e. hydrocarbons sharing similar structure and physiochemical properties will behave similarly in the environment; 2) Partitioning theory, i.e. chemicals belonging to similar structural groups will partition to organic carbon, water, and biological membranes in a similar manner and further, most hydrocarbons partition to lipids within the organisms (e.g. Target Lipid Model; McGrath et al. 2004)); 3) Critical body residues (CBR) coupled with median effect levels will provide a good estimation of impact or injury at the species level of investigation (threshold response levels have been summarized for many species groups); 4) Sensitivity of early life stages – incorporation of data representing early life stage endpoints result in the most conservative estimation of population disruption (e.g. OECD guidelines have been set for fish embryo toxicity; LC50 values greater than 100 mg/L are considered non-toxic). 

Hydrocarbon models, such as PETROTOX, organize the numerous hydrocarbon compounds in solution into structurally based ‘blocks’. If the behavior and toxicity of each block is known, the model can represent the relative predicted toxic activity level of the combined compounds present in different environmental compartments and estimate the resulting toxicity. Such an approach relies on laboratory estimates of toxicity for a variety of hydrocarbon constituents. This model assumes additivity of the toxicity for each block which may not necessarily be true. At this point in time, the quantity and quality of data with specific hydrocarbons for Arctic species are limited, however, if temperate data are also used, this approach may be feasible. 

The CBR approach couples toxicity data with tissue residue levels to predict effects. Such an approach is based on the premise that the toxicity of oil and treated oil is related to those hydrocarbons taken into the tissues. While this may have merit for exposures that occur over a long enough period to allow for uptake, it does not account for acute effects from short term exposures or physical effects due to adhesion. This method also relies on tissue residue data which are limited for Arctic species. 

Table 6-1 presents a summary of Arctic-relevant studies included in this review (link).  These studies are summarized in the following sub-sections.

Amphipods are the most studied in toxicity testing with 11 different species. This is not surprising since amphipods are a very diverse and abundant taxa with species represented in all aquatic habitats of the arctic and they are relatively easy to catch and maintain in a laboratory. Fish and bivalves share an equal number of 8 species per group.  The predominant number of studies are the Arctic or Polar cod (Boreogadus saida) and the North East Atlantic cod (Gadus morhua) followed by the decapods (4 species), gastropods (4), copepods (3), isopod (2), Mysidacea (2) and lastly pycnogonidae (1) Cnidaria (1) and echinoderms (1). Although only three copepods species have been used in laboratory testing, a considerable number of studies have been identified: 14 papers with toxicity tests performed at low temperature, 4 at warmer temperature, and 9 papers are in preparation.  A few studies (5) report community level effects, either as a mesocosm or field study with relatively few studies (9) that examined the impact on the early life stages (4 with copepods, 3 with fish species, and one with amphipod).

Five different animal species (1 fish, 1 copepod and 3 amphipod species) have been used in toxicity testing comprising a total number of 31 studies. Five papers have investigated the biological effects of petroleum related compounds on sea ice bacteria and algae.

Toxicity data evaluating the effects of oil and treated oil on pelagic communities were dominated by studies on three species of copepods (14 studies) and fish (20 studies).  Two studies dealt with the effects of oil on water-column phytoplankton.  None of the studies included euphausiids (krill).

The benthic compartment has the most diverse group of species used in ecotoxicological research with 32 different animal species dominated by crustaceans (17 species) and molluscs (11 species). Threemacroalgae species have also been reported. Eight studies at the community level (whole community, meiofauna, microalgae and bacteria) could be identified.

The growth of different Arctic marine phytoplankton and macroalgae exposed to oil in seawater and Corexit (formulation not provided in paper) dispersant were evaluated by Hsiao (1978).  Primary production rates varied with type and concentration of crude oil and species composition.  Diatom growth (Chaetoserus septentrionalis, Navicula bahusiensis and Nitzschia delicatissima) was inhibited at 10 days of exposure at 10 ppm; whereas, growth in green flagellate (Chlamydomonas pulsatilla) was stimulated by two different oil treatments.   Primary production of natural populations of phytoplankton from different locations in the Beaufort Sea ranged from stimulation to inhibition.  Primary production of macroalgae (Laminaria saccharina and Phyllophora truncate) collected from the Beaufort Sea was inhibited by the different oil treatments. 

The effects of oil and dispersed oil exposure on the macroalgae Stictyosiphon tortilis, Dictyosiphon foeniculaceus, and Pilayella littoralis were evaluated during a surface and subsea field release of weathered oil dispersed with Corexit® 9527 (Cross et al. 1987a).  There were no detectable adverse effects on biomass, diversity, or reproductive condition of the shallow subtidal macroalgae.  Similarly Cross (1987) found no decrease in cell densities, chlorophyll a concentrations or productivity in the ice algal communities dominated by the pennate diatoms Nitzschia grunowii and N. frigida; there was some evidence of slightly increased production in the untreated oil exposures.  Exposure concentrations in the sea ice were estimated to be 0.15 to 0.28 ppm in the oil-only exposures and 5.8 to 36.5 ppm in the dispersed oil exposures.  Cross (1987) notes that the first measures of production and biomass were made approximately two days after dispersed oil application and any immediate and transitory effects would not have been detected for any of the oil treatments.

In more controlled laboratory conditions, Van Baalen and O’Donnell (1984) grew cultures of the sympagic diatoms Nitzchia sp and Chaetoceros sp. collected from the ice edge in the Bering Sea the presence of two crude oils and two fuel oils.  Growth inhibition was observed for Nitschia sp. at concentrations >50 ppm for both the crude oil and fuel oil treatments.  Chaetoceros sp. growth was inhibited at concentrations between 50 and 500 ppm.  For both species, effects were greater in the 0°C treatments than in the 10 °C treatments.

Results of studies with Arctic phytoplankton and macroalgae are somewhat equivocal.  However, based on these studies there appears to be inhibition of sea ice algae and phytoplankton in the presence of oil and dispersed oil.  However, this effect does not appear to persist if petroleum concentrations decrease.  Effects may persist in sea ice if petroleum is incorporated into the sea ice.

The mysid (Mysis oculata) is an epibenthic shallow-water invertebrate that is common throughout the coastal waters of the Arctic (Photo 6-3).  Mysis relicta is a boreal pelagic mysid found in colder waters of Baltic and Barents Sea.  Both species represent a component of fish diets, as well as some marine mammals and birds.  Mysids are considered sensitive indicators of aquatic toxicity and the temperate mysid,Americamysis bahia is one of the most common laboratory test species.

Photo 6-3: Mysid from Kongsfjorden (Ida Beathe Overjordet)

Photo 6-4: Calanus finmarchicus (Bjørn Hansen)

Photo 6-5: Calanus glacialis (Bjørn Hansen)

Acute lethal toxicity levels were derived for young-of-the-year mysids (M. oculata) exposed to oil in water dispersions (OWD) and WSF of Norman wells crude oil (Riebel and Percy 1990).  The 96-hour LC₅₀s for continuous exposures to OWD were 4.51 to 7.57 ppm nominal.  In the water-soluble fractions, LC₅₀ values were approximately 0.5 ppm nominal.  No apparent physical effects were observed in the OWD treatment.  The 96-h LC₅₀ for the mysid M. relicta was 2.7 ppm, in continuous exposures to water-soluble fractions of Cook Inlet crude oil.

As noted above, there have been a number of studies focusing on the sensitivity of Arctic copepods to oil and treated oil.  Copepods are an Arctic keystone species, transferring energy from lower to higher trophic levels of the Arctic and sub-Arctic food web (Photos 6-4, 6-5). 

Hansen et al. (2011) evaluated the survival and WAF-mediated induction of the gene encoding glutathione S-transferase (GST) for the Arctic copepod Calanus glacialis and the boreal copepod C. finmarchicus exposed to water-accommodated fractions of oil.  The 96-h LC₅₀values differed between the two species with the Arctic copepod being less sensitive than the temperate-boreal species.  However, LC₅₀s were similar when copepods were observed for a longer period of time.  The lipid-rich copepods survived longer than lipid-poor copepods at the same exposure concentration. In terms of GST expression, both species showed concentration-dependent and exposure time-dependent trends. The Arctic copepod appeared to respond slower and with a lower intensity indicating that a delayed response and that longer test duration is required to observe effects.

Photo 6-6. C. glacialis (Jack D Word)

Gardiner et al. (2013) found similar results in tests with water-accommodated fractions and chemically dispersed WAF preparations, conducting 12-day spiked exposures with C. glacialis (Photo 6-6).  The mean LC₅₀ for WAF with fresh Alaska North Slope crude was 4 ppm TPH, similar to the range of values (2.5 – 9.6 ppm) of Hansen et al. (2011) and Nordtug et al. (2013).   The mean LC₅₀ for the dispersed WAF was 22 ppm and 62 ppm for early season and late seasonC. glacialis.  Similar to Hansen et al. (2011) the low lipid reserves likely affected the sensitivity of copepods in the early season.  Gardiner et al. (2013) found that when expressed as total PAH or parent naphthalene, the relative toxicity of the WAF and dispersed WAF was more similar, showing that TPH is a gross measure of exposure concentration and includes numerous constituents that do not contribute to toxicity.

Hansen et al. (2012) used a newly develop droplet generator to create physical dispersions of oil with droplets of a similar size distribution as those from chemically dispersed oil.  When the toxicity of the physical dispersions to C. finmarchicus were compared to those of the chemical dispersion, the 96-h LC₅₀s differed by a factor of 1.6, whereas the LC₁₀ (that concentrations the causes 10% mortality) and LC₉₀ (that concentration that causes 90% mortality) differed by factors of 2.9 and 0.9, showing that at high effects levels, there was little difference between the physically and chemically dispersed oil and indicating that the full dose-response curve should be considered in risk assessments.

Jensen and Carroll (2010) evaluated the effects of continuous sublethal WSF exposures on reproduction and feeding for C. glacialis and C. finmarchicus.  A reduction in feeding was observed for C. finmarchicus at concentrations of 7 ppb total PAH and a decrease in egg hatching success was observed forC. glacialis.  

Photo 6-7. In situ burning test (Liv-Guri Faksness)

Faksness et al. (2012) conducted one of the few toxicity testing programs with the residuals of in-situ burning (Photo 6-7).  Seawater samples and oil collected immediately after in-situburning were evaluated for chemical composition and toxicity.  Acute toxicity tests with the marine copepod C. finmarchicus showed no increase in toxicity in the underlying water after in-situ burning.

A number of studies have evaluated the effects of pyrene on copepods including survival, egg hatching, development time and dynamic energy budget for C. glacialis and C. finmarchicus (Hjorth and Nielsen 2011; Grenvald et al. 2013; Klok et al. 2012, 2014).  Copepod survival and gene expression have also been evaluated for exposures with naphthalene.  Recent efforts are focusing on coupling copepod toxicity data with models for uptake and population level effects (Hansen et al., in preparation) and in many ways the data on copepods are perhaps the most complete for Arctic species.

An additional study conducted with C. finmarchicus by Melbye et al. (2001) focused on the uptake of hydrocarbons from dispersed oil droplets using a flow-through system with a drop generator.  This study was designed to specifically examine the uptake and bioaccumulation of the oil droplets.  The dispersion was created by using an ultrasonic probe and mixing 6.05 g of Totalfina oil in 500 mL of seawater for 10 minutes.  Water and organism tissues were collected and monitored over specific intervals throughout 14 days of testing. The copepods were field collected from the Trondheim fjord.  This species was chosen for uptake studies of dispersed oil because it actively filters water for particles in the 10 – 50µm size range.

As reported in Melbye et al. (2001), C. finmarchicus accumulated hydrocarbons in the concentration range of 200 to 1000 ppb, based on analysis of the stock solution.  The uptake of physically dispersed oil did increase from 7 to 14 days but results also showed that a significant portion of the oil was adsorbed to the outside surface of the copepods.

Photo 6-8 Amphipod (Jack D Word)

Amphipods are an essential component of the ice, benthic, and pelagic communities, forming a link between lower trophic levels (e.g. algae and copepods) and upper trophic levels (Photo 6-8).  Amphipods have also been used as sensitive indicators of toxicity in both sediments and waters, particularly hyperiid and gammarid amphipods.  Existing data include benthic, epibenthic, and sea ice amphipods.  Studies with hyperiid amphipods, an important prey resource, were not identified. The sea ice amphipod Gammarus wilkitzkii has been tested with water-soluble fractions of crude oil.  Hatlen et al. (2009) evaluated mortality, respiration, molting and oxidative stress of water-soluble fractions of crude oil on the Arctic ice amphipod, G. wilkitzkii in continuous exposures using rock-column oil-generator column.  No mortality or molting effects were observed at test concentrations ranging from 120 to 764 ppb total PAH; however, respiration effects and oxidative stress was observed indicating sub-lethal effects.  Camus and Olsen (2008) exposed eggs of the ice amphipod G. wilkitzkii to water-soluble fractions of crude oil for 30 days using continuous-flow oil generator columns.  A significant increase in embryo aberrations was observed in the highest test concentration (55 ppm total PAH in overlying water on Day 0).  Other sublethal endpoints, such as energy allocation and oxidative stress, have been evaluated for G. wilkitzkii in similar exposures.  Olsen et al. (2008) evaluated the energy budget of ovigerous females of G. wilkitzkii in continuous exposures to water soluble fractions of crude oil.  Sublethal exposures ranged from 5 to 55 ppm total PAH, decreasing over the 30-day exposure period.  Protein levels were significantly higher in the 10 ppm total PAH dose, potentially indicating a stress response.  Other measures of energy allocation were unaffected by the WSF preparations.

Two other sympagic (ice-associated) amphipods (Gammaracanthus loricatus and Onismus nanseni) were tested in a similar water-soluble fraction generator column (Carls and Korn 1985) with Cook Inlet crude oil.  The 8-day LC₅₀ concentrations were 3.7 ppm and >1.7 ppm total PAH, respectively.  As has been shown with other Arctic species, there was a delayed response in the tests with ice amphipods, with 8-day or longer exposures better representing toxicity.

Benthic amphipods are commonly used in toxicity testing in many regulatory programs and can be sensitive indicators of impacts to nearshore or shelf benthic communities.  There have been numerous toxicity studies evaluating the effects of oil, dispersed oil, and individual PAHs on amphipods.   Benthic amphipods G. zaddachi, O. affinis, Anonyx nugax had LC₅₀s ranging from 2.3 to 8 ppm total PAH in water dispersions. 

Tests with single PAH compounds have included total naphthalene and 2-methylnapthalene.  Carls and Korn (1985) report 96-h and 8-d median lethal concentrations for O. nanseni, A. nugax, and G. loricatusranging from 2.2 to 3.5 ppm.  Olsen et al. (2011) report 2-methylnaphalene 96-h LC₅₀ values of 1.34 and 1.92 ppm for the amphipods Gammarus sp. and A. nugax.  In each case the relative sensitivity to single PAH compounds was remarkably similar to other species within the phylum (Pandalus borealis, Sclerocrangon boreas, Mysis sp.).

Photo 6-9: Decapod crab larvae (Ida Beathe Overjordet)

Photo 6-10: Larval shrimp (Bjørn Hansen)

Echinoderms, molluscs, and epibenthic decapods (Photo 6-9) play an important role in supporting upper trophic levels (e.g. the clams Serripes sp. and Mya sp.), support fisheries (Pandalus borealis), and are known to be sensitive indicators of toxicity (Strongylocentrotus droebachiensis).  Olsen et al. (2011) report data for a number of benthic organisms tested with 2-methylnaphthalene including Chlamys islandica (scallop) adult S. droebachiensis (sea urchin), Acmea tessulata (gastropod snail), Littorina littorea (gastropod snail), Margarites helisina (gastropod snail), Pandalus borealis (shrimp; Photo 6-10), and Nympon gracile (sea spider).  Among the most sensitive were S. droebachiensis and A. tessulata whereas the snail M. helisina and the sea spider were the least sensitive.  The amphipods Gammarus sp. and A. nugax and the fish B. saida were also included in this evaluation.  The amphipods were similarly sensitive to other benthic invertebrates, while the B. saida was among the most sensitive to 2-methylnaphthalene.  This study represents one of the most comprehensive datasets for benthic and epibenthic species and is used to compare arctic and temperate species using species sensitivity distributions.

The effects of oil in sediment and dispersed oil have also been evaluated with the clams Mya truncata (Camus et al. 2003; Mageau et al. 1987) and Serripes groenlandica (Mageau et al. 1987), the sea urchin S. droebachiensis(Mageau et al. 1987) and the crab Hya araneus (Camus et al.  2002) and Chionocetes bairdi (Perkins et al. 2003).

Photo 6-11: Arctic cod (Brian Hester)

Photo 6-12: Arctic cod in acclimation tank (Lionel Camus)

Relatively few Arctic fish species have been tested with oil and treated oil.  Understandably, the majority of available data are for the Arctic cod, Boreogadus saida.  Arctic cod are ubiquitous throughout the Arctic, representing a critical link between the zooplankton community and higher trophic levels (e.g. seals, beluga whales).  B. saida is a truly pan-Arctic, occupying nearshore, pelagic, and sea ice habitats, residing both at depth and near the surface waters, depending upon age and season (Photos 6-11, 6-12).  The sensitivity of Arctic cod has been evaluated for both oil and dispersed oil.  Gardiner et al. (2013) conducted spiked exposures one-year-old B. saida with WAF and dispersed WAF to emulate open-water pelagic conditions.  Median-lethal concentrations were reported for TPH, total PAHs, and parent naphthalene.  Data were then used to compare the relative sensitivity of Arctic and temperate species using species sensitivity distributions.   Carls and Korn (1985) also report median lethal concentrations to 8-day continuous exposures of water soluble fractions (total PAH) and naphthalene. 

Chronic exposures have been conducted both with water-soluble fractions and oil-dosed food.  Nahrgang et al. (2009) conducted a series of studies with B. saida, exposing the fish to water-soluble fractions of oil, injecting fish with benzo (a) pyrene, and feeding prey items exposed to crude oil.  Following chronic (4 weeks) exposure to water soluble fractions, biomarkers showed evidence of PAH uptake and genotoxicty.  Christiansen (2000) and Christiansen and George (1995) evaluated the effects of oil-contaminated prey on cod appetite, growth and osmoregulation.  Food contaminated with 200 or 400 ppm crude oil did not affect appetite but resulted in decreased growth; foods contaminated with concentrations of 500 ppm were rejected.

Capelin (Mallotus villosus) is a keystone fish species, particularly in the Barents Sea.  As with B. saida, M. villosus represent the trophic link between zooplankton and larger fish, birds, and marine mammals.  Despite their importance, there were few studies evaluating the toxicity of oil or dispersed oil with capelin.  Khan and Payne (2005) exposed capelin to oil and dispersed oil (Hibernia and Corexit 9527) in continuous flow-through tests of 96-h.  Similarly, Frantzen et al. (2012) evaluated the toxicity of crude oil to M. villosus embryos.  Concentrations of 46 ppb total PAHs increased embryo mortality rates and decreased hatching success. 

Photo 6-13: Myoxocephalus sp. (William Gardiner)

Sculpin (Myoxocephalus sp.) are among the most common demersal fish species in the Arctic.  Toxicity tests have been conducted with oil and dispersed oil (Photo 6-13).  Gardiner et al. (2013) conducted spiked exposures to WAF and dispersed WAF with larvalMyoxocephalus sp.  Median lethal concentrations were generally lower than those for the Arctic cod; however, the sensitivity was similar when older cohorts of larval sculpin were compared.  Carls and Korn (1985) exposed the sculpin, Oncocottus hexacornis to water-soluble fractions of Cook Inlet crude, with median lethal concentrations >1.7 ppm total PAH.

Table 6-1.  Toxicological Investigations

Approximately 56 studies have been conducted with crude oil.  There have been a number of different oil types included in the different testing programs, as well as different types of preparations with untreated (soluble fraction or physically dispersed) or treated oil (chemical dispersant or ISB). Peer-reviewed studies with photochemically enhanced toxicity (photooxidation) with Arctic species are not available. However, photoenhanced toxicity of physically and chemically dispersed Alaska North Slope crude oil has been evaluated with Pacific herring eggs and larvae (Clupea pallasi; Barron et al. 2003). 

Exposure systems vary between studies although there is an increasing trend to harmonize the approaches between laboratories.  Studies have been conducted as continuous or declining exposures, with WAF, dispersed WAF, or physical dispersions.  It is noteworthy that relatively few types of chemical dispersants have been used in toxicity studies, primarily Corexit®9500 and Dasic Slickgone. The vast majority of the exposures were waterborne and five studies were diet borne exposures.

Relatively few studies have included weathered oil.  There are some studies (e.g. Hansen et al. (in prep) have tested weathered and unweathered oil with the copepod C. finmarchicus. Given that OSR response times may be delayed in the Arctic due to the potential distances and inclement weather, this should be a future focus of study.

Single PAH toxicity data are an important component in developing predictive models and for comparing effects between different OSR alternatives.  Most studies performed with single compounds included 2-methyl naphthalene, naphthalene, and pyrene.  Fewer studies have evaluated benzo(a)pyrene and phenanthrene and primarily when evaluating uptake and tissue residues.  The naphthalene compounds are often included in testing programs since they are predominant in the crude oil and are known to elicit most of the acute toxicity.  Pyrene and benzo(a)pyrene have been used as model compounds to study a specific biological mechanism (uptake rate, metabolism, enzyme induction).

An increasing number of research programs are being conducted with Arctic species exposed to chemically dispersed oil and physically dispersed oil. Such data allow for a direct comparison of two OSR alternatives and provides responders with information to determine whether chemical dispersants should be used on an oil spill in the Arctic.  For Arctic species this research has focused on calanoid copepods and fish larvae (e.g. Hansen et al. 2012; Gardiner et al. 2013).  An additional paper in preparation addressed the same issues with shallow water benthic species (Frantzen et al. 2013, in prep.). While only two chemical dispersants were used (Corexit®9500 and Dasic Slickgone) and three different exposure systems between laboratories were employed, the investigators concluded that the same concentration of chemically dispersed oil is not more toxic than physically dispersed oil.  These conclusions suggest that chemical dispersants do not increase the toxicity of oil.

Arctic species require a longer period of time to exhibit effects associated with petroleum exposures.  A number of researchers have noted that Arctic species of fish (B. saida) and copepods (C. glacialis and C. hyperboreus) require up to 12-days to show effects associated with acute exposures in either spiked or typical 96-hour continuous exposures (Chapman and Riddle 2005; Olsen et al. 2011, Gardiner et al. 2013; Hansen et al. 2013).  Many factors may affect the increased response time of Arctic species to oil and treated oil.  Arctic species have a number of morphological and physiological adaptations to survive at cold temperatures (e.g. lipid stores, decreased metabolic rates for some larger body size compared to temperate counterparts, and slower digestion) that may affect toxic responses (DeHoop et al. 2011; Olsen et al. 2011).

Currently there are limited data regarding the toxicity of physically and chemically dispersed oil to Arctic species compared to the substantial body of data for sub-arctic, temperate, and tropical species.  Table 6-2 summarizes data from a subset of the available data reported for median lethal concentrations of oil and dispersed oil mixtures in spiked exposures, as well as 2-methyl-naphthalene and total naphthalene in continuous exposures.  For each of the different test treatments, there is a high degree of overlap among the different test species and phyla.  This is consistent with the comparisons among larger data sets that have included both Arctic and temperate species (Figures 6-2 and 6-3).

While regionally specific toxicity data are ideal, the practical challenges of testing Arctic species in standard laboratory tests provide incentive to determine if previous research on a broader array of species from different regions can be extrapolated to Arctic species. Some studies have attempted to answer the question whether the Arctic species are more or less sensitive to oil components than the temperate species at the individual level: using bivalves (Baussant et al. 2009), fish (Skadsheim et al. 2009, Christiansen et al. 1996; Ingebritsen et al. 2000), decapods (Perkins et al. 2005), copepods (Hansen et al. 2011; Jensen et al. 2008; Jensen and Carroll 2010; Hjorth and Nielsen 2011; Grenvald et al. 2013; Word and Gardiner, in preparation). Interestingly, Hansen et al. (2011) found that lipid rich individuals C. glacialis survived longer than the lipid-poor C. finmarchicus individuals exposed to crude oil highlighting that lipids which are crucial to most arctic species can influence the results of toxicity tests. Furthermore, Christiansen et al. (1996) and Ingebritsen et al. (2000) revealed that the cold water adapted kidney of the polar cod (the kidney is aglomerular to retain the antifreeze biomolecule in the blood) may prevent excretion of contaminants via the urine. Although the specific physiological cold water adaptation may render the B. saida more susceptible to contaminants, there is no evidence that this fish is more vulnerable than other fish.

Olsen et al. (2011) ran acute toxicity tests with Arctic and temperate species with a single PAH (2-methyl naphthalene) and developed species sensitivity distributions (SSD) which could be compared statistically. This study indicated that median estimates for the hazardous concentrations affecting 5 and 50 percent of the species (HC₅ and HC₅₀) based on both the NOEC and LC₅₀ estimates were less than a factor 2 higher for temperate species than for Arctic species and were not statistically different. The authors concluded that there was no regional differences in tolerance to 2-methyl naphthalene either at the species level (LC₅₀ and NOEC) or at the aggregated species level (HC₅ and HC₅₀).  Further they conclude that the values of survival metrics established for temperate regions are transferrable to the Arctic.  These findings are supported by Word and Gardiner (in prep) who compare the relative sensitivity of Arctic and non-Arctic species using measured and literature data. They come to a similar conclusion for parent naphthalene, WAF, and CEWAF in spiked exposures (see Figures 6-2 and 6-3).

Table 6-2.  Summary of Median Lethal Concentrations for Four Major Phyla

Figure 6-2. Species-sensitivity distribution curves comparing the relative sensitivity for Arctic (solid line) and temperate (dashed line) species to for 2-methylnaphthalene based on (A) LC50s, and (B) No effect concentrations.
[Thin dashed lines represent 95% confidence intervals (Olsen et al. 2011)].

Figure 6-3. The relative sensitivity of arctic and temperate species to naphthalene, WAF, and CEWAF exposures (Word and Gardiner, in prep)

A third study by DeHoop et al. (2011) also used the SSD approach to evaluate the relative sensitivity of naphthalene, 2-methylnaphthalene, and crude oil across data sets from a variety of literature sources.  The results support the general conclusion of Olsen et al. (2011) that values of survival metrics for temperate regions are transferrable to the Arctic for the chemical 2-methyl naphthalene, naphthalene, and physically and chemically dispersed crude oil as long as extrapolation techniques are properly applied and uncertainties are taken into consideration.

In assignment of risk for regulatory purposes, it is assumed that if species at the individual level are protected then higher levels of biological organizations (e.g. populations, communities, and ecosystems) will also be protected.  This implies that if there are similarities in the sensitivity of temperate and Arctic species, then they will be similarly sensitive at the population or community level.  However, a mesocosm study at the community level (Olsen 2007a) demonstrated that Arctic benthic communities may respond to oil-related compounds differently than temperate communities. Indeed, by measuring respiration, community structure and sediment characteristics as response variables of sediment community exposed to crude oil no effects could be observed with the temperate benthic communities as opposed to the Arctic sediment community. The authors highlighted that the effects were mainly due to differences in community structure and functioning between the two ecosystems.  Although the potential influences of a non-pristine temperate community could not be ruled out.  This study highlights the need to properly extrapolate from individual test models to population level for a proper environmental consequences analysis (ECA).

There has been a considerable effort in the past five to ten years to better understand the sensitivity of Arctic species to oil and treated oil, with nearly half of the identified studies published in the last five years.  Most of the recent studies provide relatively good information for risk assessment and biomonitoring, especially for the pelagic ecosystem and for assessing the toxicity of chemically or physically dispersed oil.

The copepod dataset is among the most complete for Arctic species, particularly for acute lethality.  Current data exist for oil-water dispersions, dispersed oil, ISB residuals, and single compounds.  There are similar data evaluating oil and chemically dispersed oil for pelagic fish, particularly Arctic cod (B. saida) and Atlantic cod (G. morhua).  For acute-lethal endpoints, data sets could be expanded with qualified data from boreal or temperate data sets.  There is also an emerging dataset regarding sublethal endpoints for copepods and cod; however, this dataset is still limited.  Other pelagic VECs that have little or no data (e.g. capelin, hyperiid amphipods, C. hyperboreus, and Arctogadus glacialis) as well as other types of petroleum hydrocarbons (e.g. ISB residuals) should be a focus of future efforts.   

Ice communities are a unique component of the Arctic and their ecology has been a focus over the past decade.  Recent toxicity studies have dramatically increased our understanding of effects of oil and dispersed oil on ice amphipods, an important component of the ice community.  These acute toxicity data are suitable for use in evaluating the effects of oil in ice.  However, additional work is necessary to better understand effects and exposures of oil and treated oil in and near sea ice and sublethal effects. 

There is a substantial amount of data on the effects of oil and treated oil on temperate benthic communities; however few data exist for Arctic species.  Based on the study by Olsen et al. (2011) some data on temperate species may be applicable for Arctic species however, the data supporting this conclusion are limited.  Further evaluations with other single PAHs, oil and treated oil for targeted species designed to strengthen this conclusion will dramatically improve the available data for benthic intertidal and subtidal communities.

The review of the ecotoxicology of oil and treated oil in the Arctic described by the authors in this section led to suggestions of further research which can reduce remaining uncertainties.  The more generic suggestions compiled from this review are summarized below while recommendations that are important for improving Arctic NEBA are listed separately.

1. Bunker oil and other fuel oils:  As the ship traffic increases in the Arctic, fuel oils are the most likely petroleum compound to be released.  The consequences of accidental discharges of bunker oil need to be better understood, particularly considering that currently limited technical solutions exist to recover bunker oil mixed with sea ice (communication by the coastal administration of Norway).
2. Chemical dispersants: a limited number of chemical dispersants have been tested.  Indeed only Corexit® 9500 (NALCO 2013) and Dasic Slickgone (DASIC 2013) could be found in the recent literature while many other dispersants exist on the market and could potentially be used during an oil spill response. In order to select the best response option, it is important to understand the performance characteristics of chemical dispersants in low temperature applications.
3. Ecotoxicological studies:
   1. To complement the existing lethal toxicity dataset, we recommend conducting toxicity studies to better characterize the effects of dispersed oil, including both acute and chronic exposures.  Where appropriate, longer-term studies should be conducted with treated and untreated oil focusing on ecosystem/species recovery.  Such long-term toxicity data can be used in combination with experiences from cold-water spills (e.g. Exxon Valdez) to identify critical factor for effects/recovery (See Ecosystem Recovery Section).
   2. Single PAHs:  Toxicity data with single compounds provide an important tool for comparing the toxicity of different OSRs, as well as providing model input.
   3. Herding chemicals:  Chemical herding agents are a promising enhancement for spill response amendment under certain conditions.  Examine the effects of herder chemicals that concentrate surface oil and are relatively unknown to date.
   4. Photooxidation: sea ice species living at the surface of the sea can be exposed to oil whose toxicity has been enhanced following exposure to UV, this could be addressed as part of a larger effort to resolve this issue for any marine spill (this issue is not unique to the arctic, and we do not have sufficient resolution for arctic or temperate exposures).
   5. Examine modes of action:  Knowledge of the quantitative effect of oil droplets and soluble components of oil on biota is also of great importance.  Examinations of toxicity modes of action need to address chemical uptake, body burdens and the narcosis related responses but also need to address the potential for the direct effects of fouling and implications of impacts of soluble or volatile compounds on epithelial tissues, especially those related to respiration.  
4. Community level assessments:  As the need for an ecosystem management approach has been growing over the last few years, there is a need to move from single species toxicity tests towards community studies to produce data with the highest ecological possible relevance with a specific focus on the structural and functional changes. One methodological approach as discussed earlier would be the use of in situ and other mesocosms and also to work with early life stage impacts that can be fed into population and possibly ecosystem models.

Photo 6-14: Pelagic Hyperiid amphipod Themisto sp (Bjørn Hansen).

The recommendations presented below indicate where increased knowledge of ecotoxicology would result in reducing existing uncertainties in NEBA assessments.  No prioritization has been made to the list; for some of the recommendations, surrogate data may be already available.

1. Toxicity studies of weathered and unweathered OSR residuals.  Given the remoteness of the Arctic and the inclement weather, it is possible that responders will be treating weathered oil.  The toxicity of oil weathered under Arctic winter conditions is less well understood.  Priorities for toxicity data production should be defined based on the need for input into existing impact assessment tools which will be used by the stakeholders.
   1. ECs coupled with VEC test species:  In non-pelagic environments (surface microlayer, intertidal, shallow subtidal, deep water species, annual and multi-year ice); Pelagic: weathered oil
      • Create exposures to constant droplet size and concentration of OSR residuals; determine biological responses (survival, growth, lipid content, possible fecundity measure); determine impacts due to dissolved fraction and risk to pelagic organisms
      • Conduct in-situ assessment of rate of benthic recovery from controlled oil exposure
   2. Endpoints:  fouling, mortality, uptake and narcosis, histopathology associated with measured chemical concentration in exposure media.
   3. Exposures:  spiked, low constant dose, multiple spiked to simulate re-oiling (e.g. Droplet generator studies).  Although LC50 are used for regulatory risk assessment, the ecotoxicological information that they provide is often not environmentally relevant since the amount of oil tested far exceeds potential environmental concentrations.
   4. Evaluate SSD curves   Evaluate SSD curves for weathered and fresh oils for various modes of action.
   5. Evaluate consequences of OSR strategies.  To date there are very few toxicity studies that have been conducted with certain types of OSRs, most notably ISB residues and OMAs.  A full evaluation of OSR alternatives will require additional toxicity data for targeted VECs, defined by the anticipated fate of the treated oil.Additionally, very few chemical dispersants have been fully evaluated for acute and chronic effects.
2. Augmentation of relative sensitivity dataset. The relative sensitivity assessment of arctic versus temperate species conducted by several authors indicates that the toxicity database for Arctic studies could be augmented with data from temperate species.  Further data are required for sublethal and chronic effects of oil and treated oil before the data can be extrapolated from temperate studies.  Data on benthic species and subtidal communities are sparse.  Further information is also needed for other Arctic VECs such as nearshore fish (e.g. capelin), sea ice, microlayer, and higher trophic groups (such as birds and mammals).
3. Improve model relationships
   1. Impacts due to volatile fractions of oil.  Volatilization of hydrocarbons exposes marine mammals and seabirds to respiratory impacts (greatest with natural attenuation, herder application, mechanical recovery, ISB); exposure needs to model concentrations near air/water interface.
   2. Encompass all modes of toxic action

Authors Dr. Lionel Camus [Akvaplan Niva], Dr. Jack Q. Word and William W Gardiner [ENVIRON], Dr. Bjorn H Hansen [SINTEF], Steinar Sanni [IRIS], Dr. Oleg Titov [PINRO], Dr. James Clark [HDR/EM&A] 

Access Database Summaries 

Oil Toxicity data: TPH, TPAH, or single compounds 

Dispersed oil toxicity data: Corexit 9500, Corexit 9527, combined data 

Corexit-only exposures: Corexit 9500, Corexit 9527, combined data