The review of the biodegradation of 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. Determine effects oil properties may have on biodegradation under Arctic conditions. The physico-chemical characteristics and weathering conditions of different oils at low temperatures may vary considerably, having impacts on biodegradation efficiencies and should be considered for further research, for instance, in the relationship between biodegradation and oil appearance (e.g. viscosity, dispersibility, resurfacing) after a spill. Temperature-related biodegradation data used in models, often based on Q10-approaches, may show erroneous results at very low temperatures, probably due to physical changes in the oil. 
2. Further document the rates of weathering of stranded oil. Oil residuals from treated or untreated oil undergo different rates of weathering when transferred to sandy beaches or cobble beaches, under or within annual or multi-year ice and within lagoons or near estuaries. Stranded oil has a different potential for release of oil from those compartments and thus longer or shorter periods of time where localized re-oiling of adjacent locations occurs. 
3. Explore options of enhanced bioremediation with biostimulation and/or bioaugmentation. Biostimulation at very low temperatures where hydrocarbon biodegradation is apparent should be a research issue. Accelerated biodegradation has mainly been investigated by adding fertilizer formulations to improve the oil biodegradation capabilities of natural microbial populations. Biostimulation is regarded as a relevant tool for removal of stranded oil residues as an extension of mechanical treatment. Several formulations of fertilizers have been tested experimentally and under real spill situations. Oleophilic fertilizers have proven more efficient than inorganic nutrients, but available formulations seem to have reduced effects at very low temperatures, such as in marine ice (Gerdes and Dieckmann 2006). Bioaugmentation seems to be less efficient than biostimulation, although some experimental studies have combined the two remediation options. However, several oil cleanup products have been marketed in recent years, including bacteria. Further development of techniques for the enrichment of site-specific oil-degrading communities may therefore be of relevance to combine with other remediation techniques. 

The recommendations presented below indicate where increased knowledge of biodegradation processes 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. Investigate potential for recalcitrant effects of oil and consequences of oil spill response strategies (OSRs).    There is a need to better understand what happens to the unrecovered oil once released and distributed to different Environmental Compartments (ECs) in Arctic environments, such as surface slicks, and under ice or onshore stranding.  In order to meet these objectives, we recommend conducting a series of laboratory experiments to determine the persistence, rate and extent of biodegradation in relevant Arctic systems, including surface water, ice and sediment under Arctic marine conditions to further our understanding of the biodegradable and recalcitrant oil dynamics in these compartments.
2. Examine the influence of ice on biodegradation rates.  Marine ice poses a particular challenge to the indigenous microbes, which require the ability to survive and be metabolically active at sub-zero temperatures and at high salt concentrations.  Microbial metabolism has been demonstrated in marine ice, and populations have been stimulated by oil in the ice.  However, the extent of hydrocarbon biodegradation in Arctic ice requires more attention.
3. Improve knowledge of degradation rates of dispersed oil and oil in the water column and in other Arctic environmental compartments.  More information is needed on how employment of different oil spill response strategies would affect biodegradation rates and oil movement to different compartments.  For investigations of OSR strategies, we suggest studies be conducted with chemically dispersed oil. These studies include experiments relevant for the following compartments and conditions:
   1. The seawater surface with droplets entering the surface creating a surface film/sheen
   2. The water column, creating physically or chemically generated dispersions and maintaining these in the water column
   3. Subtidal seabed, examining the biodegradation of oil remaining on the seabed after particle integration
   4. Oil in marine ice, with dissolution of water-soluble components to the brine channels in the ice
   5. Shoreline sediments, examining the biodegradation of oil stranded in areas that are ‘primed’ by prior exposure to oil compared with biodegradation in areas that are ‘naïve’ or previously unexposed to oil