Schematic diagram of Arctic-specific conditions that affect microbial degradation of oil spills:
A) Sea ice and icebergs hamper wind/wave-induced mixing in the upper water column and cause a thicker oil slick, which, in combination with low temperature, reduces evaporation, dispersion and dissolution. All these effect result in larger oil droplets, which microbes cannot degrade.
B) Most oil compounds are not soluble in water. Therefore, the bacteria form a biofilm on the oil droplets in order to be able to consume the oil compounds. A small fraction of the oil compounds is water-soluble and thus consumed by both biofilm and free-living bacteria.
C) Oil-mineral and oil-phytoplankton aggregates, which may enhance oil sedimentation ('dirty blizzards'), are formed upon interaction with sediment plumes from glaciers and phytoplankton blooms, respectively.
D) Photooxidation by ultraviolet radiation from sunlight can be important, espectially during summer. Ultraviolet light helps degrading oil molecules, but at the same time, the oil toxicity towards marine organisms may increase.
E) Deep mixing of the water column and upwelling cause nutrient replenishment. Oceanographical conditions may thus be important to provide fresh nutrients for oil-eating microbes.