The Arctic polar night is not a period without any biological activity as had been assumed, says a large international team of biologists led by Norwegian scientists. Concealed behind the curtain of darkness is a world of activity, beauty, and ecosystem importance.
Aurora borealis over Norway. Image credit: Carsten / CC BY 2.0.
The researchers sampled the activities of many different species during three consecutive winters in Kongsfjorden, Svalbard, Norway.
“We were inspired to look more closely at what happens during the polar night based on a chance encounter we had on a small boat in the middle of a Svalbard fjord,” said Dr Jørgen Berge of the UiT Arctic University of Norway and the University Centre in Svalbard, Norway, lead author on the study published online in the journal Current Biology.
“Above us was a starry, winter night and below us were countless blue-green ‘stars’ in the deep produced by bioluminescent organisms. The beauty of it was stunning, and the fact that so many organisms were producing light was a strong indication that the system was not in a resting mode.”
Instead of an ecosystem that had entered a resting state, the team found a system buzzing with biological activity.
“The current understanding of Arctic ecosystems is deeply rooted in the classical view of a bottom-up controlled system with strong physical forcing and seasonality in primary-production regimes. Consequently, the Arctic polar night is commonly disregarded as a time of year when biological activities are reduced to a minimum due to a reduced food supply,” the scientists said.
“Based upon a multidisciplinary ecosystem-scale study from the polar night at 79°N, we present an entirely different view. Instead of an ecosystem that has entered a resting state, we document a system with high activity levels and biological interactions across most trophic levels.”
The scientists found, for example, that copepods and other zooplankton were actively reproducing as filter-feeding Iceland scallops kept right on growing. Baited traps with time-lapse cameras revealed an abundant and active community of shallow-water scavengers, including whelks, amphipods, and crabs.
“We were perhaps most surprised by the seabirds. Not only are they there, but they are able to find their preferred food in the total darkness,” Dr Berge said.
“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.”
The findings come at an important moment in time, given a changing climate.
“Our results suggest a different perspective regarding ecosystem function that will be of importance for future environmental management and decision making, especially at a time when Arctic regions are experiencing accelerated environmental change,” the biologists said.
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Jørgen Berge et al. Unexpected Levels of Biological Activity during the Polar Night Offer New Perspectives on a Warming Arctic. Current Biology, published online September 24, 2015; doi: 10.1016/j.cub.2015.08.024
