Scientists baffled by ‘impossible’ life hidden beneath Arctic sea ice

Scientists have been left baffled after finding ‘impossible’ life thriving at the north pole.

The tiny microorganisms, invisible to the naked eye, live just beneath the frozen surface of the central Arctic Ocean.

Discovered by experts at the University of Copenhagen in Denmark, these bacteria survive on dissolved organic matter in the cold water. 

They also need to convert nitrogen to survive, but bewilderingly, the gas is generally in short supply in the Arctic Ocean. 

So how exactly the creatures are thriving in the water has left the scientists scratching their heads. 

‘[We] have discovered an important phenomenon beneath the Arctic sea ice that was previously thought impossible,’ they say in a statement. 

‘This phenomenon could have implications for the food chain and the carbon budget in the cold north.’ 

The researchers also warn that there is less sea ice in the Arctic than there should be due to global warming, which may actually help the organisms to survive. 

According to the researchers, the tiny organisms are officially known as ‘non-cyanobacterial diazotrophs’.

These are ‘nitrogen-fixing’ bacteria, meaning they need to convert atmospheric nitrogen into a usable form of nitrogen, such as ammonium, to stay alive.

Unlike other many other underwater bacteria, non-cyanobacterial diazotrophs (NCDs) do not photosynthesize. 

The team’s field work involved measurements of nitrogen fixation from water samples at 13 different Arctic locations from aboard the research ship RV Polarstern.

The experts found a surprising high nitrogen fixation rates, especially at the ice edge, where the ice melts most actively.

What’s odd is that nitrogen is in relatively short supply in the Arctic Ocean, meaning nitrogen fixers shouldn’t be able to thrive there. 

‘Until now, it was believed that nitrogen fixation could not take place under the sea ice,’ said study author Dr Lisa W. von Friesen.  

‘It was assumed that the living conditions for the organisms that perform nitrogen fixation were too poor. We were wrong.’

In the Arctic Ocean, NCDs and other bacteria feed on dissolved organic matter released by algae, among other things.

In return, the bacteria release the ‘fixed’ nitrogen (ammonium), which helps algae in the surrounding water to grow.

Unfortunately, too much algae growth in the Arctic can be bad news as it can lead to out of control ‘algal blooms’ which are toxic and harmful to fish, shellfish, marine mammals and more.  

According to Dr von Friesen, the results suggest the potential for algae production in the Arctic has been underestimated.

What’s more, climate change is likely the ultimate cause of the observed changes.  

In the Arctic, sea ice goes through a seasonal cycle each year, spreading in the autumn and winter and then receding in the spring and summer. 

But due to climate change, temperatures are getting higher overall and the Arctic sea ice extent is getting lower on average.

Researchers warn that the Arctic is warming at rates up to four times faster than the global average, which has caused major declines in sea ice coverage, age, and thickness. 

According to the researchers, areas of actively-melting sea ice generally have more nitrogen fixation compared with ice-covered parts of the Arctic. 

It seems likely therefore that climate change is to blame for this elevated pattern of nitrogen fixation that they have observed. 

Strangely, stretches of open water have similar levels of nitrogen as ice-covered areas, but the team aren’t sure why this is. 

The study, published in Communications Earth & Environment, is the first to show the phenomenon of nitrogen fixation occurs beneath sea ice even in the central Arctic.

Therefore, nitrogen fixation should be considered ‘in the equation’ when people try to predict what will happen to the Arctic Ocean in the coming decades as sea ice declines, the authors add. 

WHAT IS THE NITROGEN CYCLE?

Nitrogen (N) makes up almost 80 per cent of our atmosphere and is essential for plants and animals.

The carbon-nitrogen bond is one of the most abundant in organic chemistry. 

Animals need it to to make proteins, which forms everything we need to live. 

In plants it forms the basis of enzymes, proteins and chlorophyll.

Ecosystems need nitrogen and other nutrients to absorb carbon dioxide pollution and there is a limited amount available in plants and soil. 

However, it is inert and most useful to life when turned into nitrates or nitrogen compounds.

The nitrogen cycle is the process by which the element is used and then fed back into the system.

Nitrogen-fixing organisms convert nitrogen into the soil from the air. 

Lightening is another way in which nitrogen reaches the soil from the air.

Nitrification is the process by which ammonia (a compound of nitrogen and hydrogen) that is in the soil is converted into nitrates by bacteria. 

Plants then take up these nitrates through their roots.  

When the plant dies this nitrogen is goes back into the soil. 

Alternatively if the plant is eaten by an animal the nitrogen returns to the soil in their waste.