A fjord full of krill

Krill. Picture: Gérald Darnis

Krill. Picture: Gérald Darnis

When most people think of krill their first thoughts are of Omega-3 capsules and food for whales in Antarctica. Whereas at least 4 species of krill are abundant around Svalbard and in the Barents Sea, they have rarely been found in high abundances in west coast fjords. Thus, we were surprised to see dense concentrations of highly active krill in Kongsfjorden in the middle of the Polar night. What sustains such activity? Their primary food source from spring to autumn is thought to be phytoplankton, which are all but absent at this time of year. Their guts show no evidence of any recent food consumption, further mystifying Polar-night researchers. Are they living from lipid reserves, or perhaps consuming transparent microorganisms like protozoans? This remains to be determined.

Krill are a central player in the CircA project, which investigates circadian rhythms in zooplankton during winter, their causes, and ecological consequences. PhD stipendiate Julie Grenvald is on board Helmer Hanssen tracking their daily abundance rhythms throughout the water column, sampling for analysis of their feeding preferences, and preserving samples for later genetic analyses. Gérald Darnis, a post-doctoral associate on the CircA project, investigates their role in carbon and nitrogen cycling. Finally, these high abundances of krill are accompanied in the water column by predatory fish, such as Atlantic cod, polar cod, haddock, juvenile herring, and juvenile redfish. The presence of such an active food web with krill as a central player during the Polar night is one of the most exciting discoveries of this expedition. But like all new discoveries, it leaves us with more questions than answers.

Gérald Darnis, Julie Grenvald, Paul Renaud

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