Evidence of fish under the last ice of the Arctic

The unknown ecosystem under the last intact ice of the North Pole will now be mapped, following an interdisciplinary expedition in 2021. Already on the spot, they noted that fish swim under the ice.
“We know that there are actively swimming organisms down there, and not plankton,” says researcher Pauline Snoeijs Leijonmalm.

This summer, marine biologist Pauline Snoeijs Leijonmalm went on a research expedition to the North Pole. She, along with other researchers, was going there to research life under the Arctic’s last intact ice – a place where no one had previously researched.

Deep Sea Reporter then interviewed Leijonmalm. One of her high hopes then was to find out if there were fish under the ice, and she didn’t feel like she could know that until she was holding a fish in her hand. The expedition ended last September.

So, did you get to hold a fish in your hand?

– Yes, I did. Though it wasn’t the fish from deep water that I had hoped for – it was from under the ice. It was a juvenile, and we found several smaller fish under the ice. So our conclusion is that these are the same kinds of “fish” that we have observed in the deep sea, but that when the fish get bigger, they go down to greater depths to find more food.

Having used sonar and other equipment, Pauline Snoeijs Leijonmalm is almost certain that there are fish in the deep sea at the North Pole – even though she has not been able to hold a fish from there in her hand.

“On the sonar, we saw how something, which in size seems to be fish, swam away when we came down with our nets. Usually when you make measurements like this, you can trawl and follow the fish.

But this is more difficult to do with two-meter thick ice.

“But we saw how the animals moved on the sonar when we lowered the net. This means that we know that there are actively swimming organisms down there, and not plankton,” says Pauline Snoeijs Leijonmalm, who was chief scientist for the expedition.

Another fish evidence that the researchers have is that they have found fish bones and otoliths (auditory stones) in the sediment on the seabed.

“Through the otoliths, who can give us an age determination, we saw that it was arctic cod and polar cod we had found. They were 10,000 years old. This suggests that there have been fish here before as well.

Now they will map the previously unknown ecosystem

On board the ship were scientists from Belgium, Holland, Sweden, Denmark and Germany. The expedition was interdisciplinary and thus included a combination of biologists, oceanographers, etc. This means that the researchers now hope that they will be able to map the hitherto unknown ecosystem – before the ice has melted away.

“Usually you have expeditions that are either atmospheric research, climate research or you just look at water chemistry. It’s only focused on a certain part of the ecosystem, but we’ve tried to capture everything.

The researchers have also taken over 800 e-DNA samples in the area, a method known for tracking the amount of covid in our wastewater. With the help of these samples, the researchers will find out exactly what kind of animals and plants are found in this extreme place.

But can you really trust a sample like that? How do you know that’s true?

– Yes, it has to do with how many times a dna sequence returns. Sometimes you can pick up a human gene or a Mediterranean shark, because DNA is everywhere. But then you have to look at all the sequences and see how often a dna sequence returns and if it is at the right depth and temperature.

Ice disappears ‘incomprehensibly fast’

But the samples have not yet been analyzed, and it will take a year before we learn in more detail what life in this unknown place looks like. The researchers have also succeeded in getting all countries that may be interested in a commercial fishery in the area to sign an agreement. In that agreement, they promise to wait until 2037 to send trawlers to the central Arctic, and until then scientists will be allowed to investigate the ecosystem. But Pauline Snoeijs Leijonmalm does not believe that any of the countries will want to fish there in the future.

“Today you can’t fish, because there’s still ice up there. But according to our research, there are not enough fish there for it to be interesting. Instead, the area should be protected, as has been done in Antarctica.

Although Pauline has been on research expeditions in the Arctic several times before, she says after this trip that it is completely incomprehensible how quickly the ice disappears.

“Since 1980, the ice has decreased by 40 percent in area and 60 percent in volume. It is completely incomprehensible how fast it goes.

She also believes that this summer’s expedition was her last.

“I’m 65 years old now and it’s pretty tough work. You have to be young and healthy. Healthy I am, but young I am no longer. But you should never say never. However, I will make sure that the next expedition that goes there takes back some fish bones for me.