The cold, dark winters of the Arctic are often considered hostile and lifeless. In fact, it’s long been presumed that the ecosystem simply “shuts down” during winter, only to be kick-started when the warming rays of the Sun return each spring. But it seems that this idea couldn’t be further from the truth, and that during the polar night, the Arctic is abuzz with activity.
Because plants form the base of most food chains, it was assumed that as there was no sunlight – and thus no photosynthesis – little would be going on in this region during the extended winter months. But after spending three consecutive winters conducting extensive sampling of the marine ecosystems, a team of over 100 researchers found the place to be teeming with biodiversity and biological activity.
Time-lapse footage of an Atlantic cod being devoured by scavengers during the polar night. Piotr Bałazy/YouTube
This new research will fundamentally change the way scientists look at what is generally seen as a harsh, unforgiving environment. “The dark polar night is not a period without any biological activity [as had been assumed],” says Jørgen Berge, one of the many co-authors of the study published in Current Biology. “Concealed behind the curtain of darkness is a world of activity, beauty, and ecosystem importance.”
It was while conducting a different study on tiny aquatic animals called zooplankton just off Svalbard that Berge began thinking there might be more to the Arctic winter. During the survey, the sea lit up with “countless blue-green stars” as the zooplankton produced bioluminescent light, suggesting that the ecosystem was far from being in a “resting mode.” Extensive surveys over the following winters, including the use of time-lapse cameras and baited traps, revealed how zooplankton were actually actively reproducing, while scallops kept on growing, and scavengers scoured the seabeds.
An overwintering black guillemot in Kongsfjorden, Svalbard. Prof Geir Johnsen/NTNU
One of the most surprising finds was that even during the pitch-black days, some seabirds decided to stay put rather than migrate. “Not only are they there, but they are able to find their preferred food in the total darkness,” said Berge. “We do not know how they are able to do this, and we do not know how common it is for seabirds to overwinter at these latitudes. But we [now] know that they do.” He suspects that some of the birds might be feeding on krill, which can also have bioluminescent properties, and thus might be advertising their whereabouts to the hungry birds.
With the shrinking of the sea ice opening up the icy waters for new shipping lanes, oil exploitation, and tourism, the research highlights how these dark months can no longer be assumed to be a “safe” period during which the ecosystems are quiet. In fact, with a number of organisms using the season to reproduce, it is probably more sensitive than at other times of the year.