Krill are essential to understanding climate change. But Antarctic voyages have been unable to catch krill for four years.
So scientists took an untested idea into the south seas in hopes of success.
Beneath this thick sea ice is one of the world’s most unappreciated climate warriors.
Antarctic krill are a food source for almost every animal on the ice.
Their home is under threat. The ice that provides protection is melting. Carbon dioxide in the water is killing the young.
To understand the threat of climate change, scientists need to study live krill in laboratories.
But catching krill is notoriously difficult.
This summer, Australian expeditioners set out on a 39-day journey to collect samples using a daring and untested method.
Australia’s new icebreaking vessel, the RSV Nuyina, was loaded with portable aquariums.
It then headed south into dangerous waters, with a plan to deliberately flood a room in the name of science.
The incredible carbon-eating talent of krill
The first glimpse of sea ice past the Antarctic Circle made the importance of the mission clear.
Almost every animal living here — whales, penguins, seals, fish and seabirds — depends on krill for food.
The crew watched as several Adelie penguins and a seal jostled for position on a small disc of ice, with krill likely swimming underneath.
It’s here that Antarctic krill are performing a role that heavy industry and governments across the world are investing billions of dollars trying to mimic — carbon capture and storage.
Krill act as a conveyor belt for carbon, carrying it from the water’s surface to the deep depths, where it can remain for centuries.
Here’s how it happens: first, krill eat algae near the surface containing carbon from the atmosphere.
Then they swim deep below and deposit the carbon as waste, which sinks to the bottom of the ocean – a natural form of carbon capture and storage.
Whales, penguins, seals and fish eat the krill, absorbing more carbon into their own bodies.
When those predators die and sink to the bottom of the ocean, they are consumed by deep-sea creatures.
Other animals can perform this task, but none to the scale of krill — the most abundant animal on Earth.
Estimates of how much carbon is taken deep by Antarctic krill vary greatly, but some studies suggest it could be around 39 million tonnes per year.
Dr Anna Belcher, an ecological biogeochemist at the British Antarctic Survey, said krill provide a “highway for the transport of carbon deeper in the ocean”.
“The deeper in the ocean the sinking faecal pellets get, the longer the carbon they contain is locked away from the atmosphere.”
If the krill population was to decline, carbon levels in the water could increase.
The frontier of climate change
Antarctica offers a chance to watch climate change unfold before your eyes.
If you wait long enough in front of a glacier, you will see sheets of ice from the cliff face collapse into the ocean — another few drops added to rising sea levels.
As waters warm, the amount of frozen ocean is shrinking. In East Antarctica, sea ice has remained relatively stable. But it’s receding faster towards the west.
A 2016 study warned krill habitat could shrink by as much as 80 per cent by 2100.
“We have seen the krill populations move southwards over the last 90 years,” Dr Belcher said.
And there is another predator: trawling vessels, whose commercial opportunities to fish for valuable krill oil are growing as the sea ice cover recedes.
Australian marine biologist Rob King, who has spent his life studying the fragile creatures, said if krill disappeared, it would spell disaster for the entire food chain.
“If the krill population declined in the Southern Ocean, we’d see the big charismatic megafauna that we all associate with this region starting to suffer,” Mr King said.
“Things like the blue whales and fin whales, that are going through a recovery since the end of whaling, would really feel the effects of declining krill.”
What scientists need to find out is the tipping point in carbon dioxide levels that could trigger a population collapse.
The Nuyina’s voyage south is 15 years in the making and informed by decades of trial and error collecting perfect krill samples.
Despite their abundance, catching krill isn’t easy.
Earlier expeditions relied on heavy trawl nets that could be ruined by ice, were difficult to deploy and could damage the krill.
Scientists with competing research projects get limited time on board — and it’s bad luck if there’s no krill around during the allotted time.
It’s been four years since Australian scientists had fresh krill to study, and it’s beginning to compromise their research.
Rob King still remembers returning to Hobart after an Antarctic voyage without a single krill to study in the aquarium.
“I think it was just a lot of time spent on decks of ships wishing you could sample for krill when you couldn’t,” Mr King said.
“When you are in sea ice you just can’t put [fishing] gear in the water when the ship is moving or it will be destroyed.”
Out of that frustration, Mr King pitched an alternative that would make most shipbuilders anxious.
His plan: suck the krill inside by drilling holes into the ship to flood it with icy Antarctic waters.
“The thing about adding a hole into a ship is that if you try and do it to an existing ship, there is an enormous back pressure from the people who want the ship to stay afloat!” Mr King said.
“But if you do it at the very start of a ship’s genesis — so that it can go through all of classification and have it built into the ship — that makes it possible.”
The Nuyina is unusual in that three holes have been deliberately drilled in the hull to allow freezing waters to flood a small room below sea level.
The theory is that Antarctic krill could be sucked inside the ship, where they would spill onto a filter table.
The water would push the animals into a well, where they could be scooped into buckets and taken to aquariums.
The “wet well” is adjacent to the engine hall and there is an obvious risk involved.
If something went wrong, the air-tight door into the flooded room must remain sealed. Scientists needing an escape could climb a ladder out of the room and then close the latch.
Despite more than a decade of planning, expeditioners on this voyage had no idea whether it would actually work.
Understandably, there were some nerves.
The first test began around 2am, when krill usually rise to the surface to feed on phytoplankton.
More than 8,000 Antarctic krill were caught during the ship’s first voyage — the biggest catch in years.
“That is what I always dreamed it could deliver, but you don’t expect to just turn it on and have it like that,” Mr King said.
“It’s the best way to wake up in the morning, to go 200 metres from your cabin down to somewhere you can flick a switch and have live Antarctic krill delivered to you instantly.”
As aquarist Anton Rocconi monitors the health of the Antarctic krill now floating in chilled aquariums, he marvels at a breakthrough that provides “survival rates that you just don’t see in a trawl”.
Mr Rocconi said with so many samples in perfect condition, scientists would be able to run experiments with different temperatures and carbon dioxide levels to truly understand what impact climate change is having.
“Many times, scientists can go to the Antarctic and not be able to catch what they need, so this really improves the chances and really will change the way we do our research,” Mr King said.
One of the riskiest parts of the voyage still remains: getting the temperature-sensitive krill off the ship and safely into Hobart aquariums.
As the ship slowly approaches land, a wandering albatross escorts the crew and cargo.
There are only 10,000 adult pairs of these birds left in the wild.
Its presence is a reminder of what’s at stake as preparations are made for the krill aquariums to be lifted off the ship by cranes and onto the back of trucks waiting at port.
The refrigerated containers must be switched off before being lifted. That means there’s a race against time to get the krill into aquariums before the water temperature exceeds 3.5C in the late January heat.
Like penguins scrambling for food on the ice, the scientists jostle for their krill to be offloaded before crew and cargo.
There is no time to wait for their bags to be unloaded: the scientists race from the port in the truck.
Just days ago, one of the scientists sent a message from a Hobart lab to say some of the Antarctic krill had just bred in captivity.
“It is so relieving and inspiring to know that all of our hard work over the voyage has delivered.”
The ABC travelled to Antarctica with the support of the Australian Antarctic Program.
Reporter: Henry Belot
Photography: Henry Belot, Pete Harmsen
Illustrations: Emma Machan
Production & editing: Jake Evans