‘Impossible’ life discovery under Arctic ice

 Our climate science could change after discovery of ‘Impossible’ life under Arctic ice

Scientists have discovered special yet impossible life forms under Arctic ocean ice, marking a paradigm shift in the climate models. The discovery of special life forms will have climate implications globally. In a research study published in Communications Earth & Environment, the researchers found the microbes called non-cyanobacterial diazotrophs under ice (NCDs) which are responsible for fixing nitrogen but are unable to photosynthesize. It has been discovered that special life forms thriving under Arctic sea ice. Until now, their presence in these dark and frigid conditions wasn't thought possible, and the findings could have global implications for the climate. Nitrogen gas makes up roughly 78% of Earth's atmosphere, and all organisms require it to survive, yet most can't use the element unless it's first converted to ammonia or ammonium.

According to biologist and lead author Lisa von Friesen from the University of Copenhagen, earlier it was believed that nitrogen fixation could not occur under the sea due to dark and frigid conditions. Nitrogen fixation is a historical phenomenon which was limited to warm and tropical waters. “We were wrong,” said study author Lisa after microbes’ discovery in the Central and Eurasian Arctic. Microbes which can grab nitrogen from the air are called nitrogen-fixers, and they provide a foundational resource for entire ecosystems. Historically, scientists believed that in oceans, these organisms were exclusive to warm, tropical waters. Now, we know better. "It was believed that nitrogen fixation could not take place under the sea ice because it was assumed that the living conditions for the organisms that perform nitrogen fixation were too poor," says lead author and biologist Lisa von Friesen.

Historically, oceanic nitrogen-fixers were believed to be exclusive to warm, tropical waters. The first of its kind discovery in the Central and Eurasian Arctic proves it wrong. Only in the last decade or so have researchers begun to consider the Arctic Ocean as an overlooked source of nitrogen-fixing bacteria. While scientists have previously found nitrogen-fixers in cold Arctic waters, von Friesen and her colleagues are the first to discover these microbes under sea ice. Samples from the Central Arctic Ocean and the Eurasian Arctic have revealed a community of thriving microbes called non-cyanobacterial diazotrophs (NCDs). This is a fancy name for bacteria that fix nitrogen but don't photosynthesize.

As per researchers’ observations, although these microbes are not found with evidence of fixing nitrogen in the Arctic, based on the genetic machinery, there is an abundance of evidence that they are actively involved in the region’s nitrogen-fixing activities. Researchers have not yet shown that these microbes are fixing nitrogen in the Arctic, only that they have the genetic machinery to do so. Their distribution and abundance, however, suggest they are closely involved in the region's nitrogen-fixing activity. If that's true, these microscopic life forms could have a global impact. Sea ice decline and the potential impact on nitrogen fixation rates. If it proves right, the discovery of these nearly-impossible microbes could change climate science globally.

Researchers found that the fringes of Arctic sea ice tend to host more nitrogen-fixing bacteria and higher nitrogen-fixing activity. This suggests that as Arctic ice rapidly melts with climate change, more of these unique microbes may proliferate, altering the marine food web and impacting the atmosphere itself. NCDs feed algae, and if algae expand in the Arctic, they could support a richer food web. According to study, the fringes of Arctic sea ice host more non-cyanobacterial diazotrophs and show higher nitrogen-fixing activity. Having been fed on the algae, NCDs could also support the food web under sea ice. "Because algae are the primary food source for small animals such as planktonic crustaceans, which in turn are eaten by small fish, more algae can end up affecting the entire food chain," explains von Friesen.

"Because algae are the primary food source for small animals such as planktonic crustaceans, which in turn are eaten by small fish, more algae can end up affecting the entire food chain," explains von Friesen. Moreover, more algal production could help in carbon sequestration as “the Arctic Ocean will absorb more CO2 because more CO2 will be bound in algae biomass," says marine microbial ecologist Lasse Riemann. More algae in the Arctic could also trap more carbon dioxide from the atmosphere. "If algae production increases, the Arctic Ocean will absorb more CO2 because more CO2 will be bound in algae biomass," says marine microbial ecologist Lasse Riemann. "But biological systems are very complex, so it is hard to make firm predictions, because other mechanisms may pull in the opposite direction." What is clear, Riemann argues, is that nitrogen fixers in the Arctic need to be incorporated into future climate models. "Sea ice melt may, directly or indirectly, stimulate nitrogen fixation," the research team concludes. "We consequently encourage a future modelling effort targeting the magnitude and dynamics of nitrogen fixation in the Arctic Ocean." Given the unprecedented discovery, Riemann suggests that these nitrogen fixers must be included in the future climate models.