No sleeping with the fishes during dark polar night

A new study reveals that marine life is as active as ever, even in the depths of the dark polar night. The findings might affect how many viewed the polar night as a safe time for change.

Courtesy of Prof. Geir Johnsen/NTNU
This photograph shows the shrimp Lebbeus polaris on the blade of a Laminaria species. Contrary to previous assumptions, underwater life in the Arctic continues actively reproducing, feeding, growing, and hunting even during the long polar night, according to a new study published Thursday in the journal Current Biology.

As winter creeps in, life on land might slow down, but life in the water keeps going at full speed.

The ocean and sea life are bustling during the long polar night, a new study shows. A team of about 100 scientists has spent the past three winters cataloging the activity of underwater life in an icy fjord and its findings go against the common belief.

“We have basically assumed that when it is dark, there is no primary production and there is no activity. The system is just waiting for the light to return,” senior author Jorgen Berge, from The Arctic University of Norway and the University Centre on Svalbard, told BBC News.

Professor Berge’s team has nearly disproved the popular misconception. The team’s data shows that many species of underwater life were actively reproducing, feeding, growing, and hunting even during the long polar night.

Some of the activity even came from above. An unknown amount of seabirds stayed in the fjord area where Berge’s team was studying, despite the cold winter. These seabirds continued to hunt and find their prey. They were able to locate their preferred food even in the dark.

“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 know that they do,” Berge said in a press release.

The study and research was inspired by a chance encounter while on a boat in the Svalbard fjord.

"Above us was a starry, winter night and below us were countless blue-green 'stars' in the deep…. The fact that so many organisms were producing light was a strong indication that the system was not in a resting mode,” Berge said. 

The team surveyed the variety of life in the fjord, the rates of reproduction, and the rates of respiration. All pointed to active underwater life.

The findings come at an interesting time, as climate change continues to grip the planet. It raises more questions of how animals will continue to adapt to a gradually warmer environment and whether the changes will affect winter patterns. 

“It turns out that the dark polar night is an important period for reproduction in a number of organisms, and, as such, it is probably more sensitive than other parts of the year," Berge said.

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