Scientists have discovered special life forms thriving beneath Arctic sea ice. Until now, it was thought that their presence in these dark and icy conditions was impossible. These findings could have global implications for the climate.
Nitrogen gas makes up approximately 78% of the Earth’s atmosphere, and all organisms need it to survive. However, most cannot use the element – unless it is first converted into ammonia or ammonium.
Microbes that can capture nitrogen from the air are called nitrogen fixers, and they provide a fundamental resource for entire ecosystems.
Historically, scientists believed that oceans were exclusive to warm, tropical waters. However, a study last week in Nature revealed that this is not the case.
“It was thought that nitrogen fixation could not take place under sea ice because it was assumed that the living conditions for the organisms that carry out nitrogen fixation were too poor,” lead author and biologist told . Lisa von Friesenfrom the University of Copenhagen (Denmark). “We were mistaken.”
Only in the last decade have researchers begun to consider the Ocean Arctic as a neglected source of nitrogen-fixing bacteria.
Although scientists have previously found nitrogen fixers in cold Arctic waters, this study is the first to discover these microbes under sea ice.
Samples from the Central Arctic Ocean and Eurasian Arctic have revealed a thriving community of microbes called non-cyanobacterial diazotrophs (NCDs). This is a fancy name for bacteria that fix nitrogen but do not carry out photosynthesis.
Researchers have not yet demonstrated that these microbes are actually fixing nitrogen in the Arctic, only that they have the genetic machinery to do so. Their distribution and abundance, however, suggest that they are intimately involved in the region’s nitrogen fixation activity.
“Global impact”
Researchers have found that Arctic sea ice margins tend to harbor more nitrogen-fixing bacteria and higher nitrogen-fixing activity.
This suggests that as Arctic ice rapidly melts under climate change, more of these unique microbes could proliferate, altering the marine food web and affecting the atmosphere itself.
