The Arctic Ocean has long been seen as a nutrient-poor environment, where a lack of nitrogen limits the growth of microscopic algae that form the base of the marine food web. But new research suggests that this picture may be incomplete.
Scientists have found that nitrogen fixation, a process that converts dissolved nitrogen gas into a form usable by living organisms, is taking place across large parts of the Arctic Ocean, including beneath sea ice. This process is carried out by specialised microbes and was previously thought to be of little importance in such cold, ice-covered waters.
The researchers observed nitrogen fixation under a wide range of conditions, from thick sea ice to the more dynamic zones at the ice edge. Activity was particularly strong near melting ice and in areas where algae were already thriving. Even in fully ice-covered regions, measurable levels were detected.
One of the most striking findings is that this process appears to be closely linked to biological productivity. In other words, the more active the ecosystem becomes, the more nitrogen is generated to support further growth. This points to a potential feedback loop in which Arctic marine life helps sustain itself as conditions change.
The study also challenges assumptions about which organisms are responsible. Instead of the cyanobacteria typically associated with nitrogen fixation in warmer oceans, the Arctic process seems to be dominated by other, less studied microbes rather than the cyanobacteria typically responsible in warmer oceans.
As sea ice continues to retreat, more light reaches the ocean surface, fuelling the growth of algae. The newly identified nitrogen source could further enhance this trend.
Together, these findings suggest that the Arctic Ocean may be more self-sustaining and dynamic than previously understood, with important consequences for ecosystems and the region’s role in the global climate system.
Léa Zinsli, PolarJournal