The analysis showed that the biomasses of krill and capelin tended to increase in years with low sea ice cover, whereas the biomasses of copepods and amphipods tended to decrease.
The dominant krill species have their main living area further south, and increased warming in the central and northern Barents Sea is expected to expand the habitable space for krill northwards. However, the analysis showed that, as capelin biomass also tends to increase in warm years, the boost in krill biomass may only be temporary, as predation pressure on the krill may increase. Whether krill biomass will increase or decrease in a warmer climate therefore depends on what happens to their main predator, the capelin.
For the predominantly arctic copepods in the region, it is simpler. The direct effect of warming is shown to be negative. In addition, they are likely to face increased predation in a warmer climate. For these copepods, both the short-term and the longer-term effects of warming are therefore negative.
This shows the importance of assessing potential feedback mechanisms between higher and lower trophic levels when studying climate effects on marine ecosystems.