The diverse marine life found beneath frozen ice
Scientists discovered a surprising amount of life beneath the polar ice when they searched beneath the ice.
Spend any amount of time looking for polar bears and you will quickly realize how well adapted they are to hunting. Despite their size, it’s difficult to spot creamy-colored bears against the flat white Arctic sea ice that blends into a light grey overcast sky. However, if one is missed, lives will be lost.
It was the summer of the Arctic. I was stationed on the top deck of the RRS James Clark Ross, a UK polar research vessel moored to an ice floe about 800 kilometers (500 miles) from the North Pole. At least two people were on polar bear watch duty whenever a group of scientists went out on the ice. As the BBC’s ship reporter (you can listen to the archived program here) – hardly a necessary role – I spent a lot of my time with binoculars scanning the horizon for one of the few animals on the planet that considers humans to be prey.
If we failed and a bear threatened anyone’s survival, there was a last resort: every group on the ice had a gun and was prepared to shoot a bear to death.
Polar bears are one of the most impressive animals on the planet, and we were fortunate to see several during our week on the ice. From the safety of the ship, we watched as a bear tore at our mooring ropes and smashed in a flight case containing the wrappers from our sandwich lunch. It must have smelled them through the
You might also like:
- The town where wi-fi is banned
- The daring plan to save Arctic ice
- The record-breaking dive under Arctic ice
While the bears were fascinating to watch, the scientists I was following saw them as an impediment to their research. They were more intrigued by the opposite end of the food chain, a hidden and vibrant world of green beneath and within the ice formed by microscopic algae.
“Phytoplankton, which is algae in water, is sometimes referred to as the forests of the sea,” says Karen Frey, a geography professor specializing in polar science at Clark University in Worcester, Massachusetts.
Frey, a frequent Arctic visitor, studies the significance of these microscopic plant-like organisms. “Half of all photosynthesis on the planet occurs in the world’s oceans, which means that the ocean provides half of all oxygen we breathe.” However, life near the North Pole is unusual in comparison to more temperate climates. Photosynthesis is impossible during the winter because it is dark 24 hours a day. “Then, as the Sun returns, you get these massive spring blooms of algae across the region – in the ice and in the water column – and everything higher up the food chain can take advantage of that,” Frey explains.
“The fish arrive, the seals arrive, and the polar bears feed on them, and everything stems from that initial production of biomass in the ocean.”
It’s not only the polar bears that ultimately benefit – fish are a vital source of food for a variety of animals, including people, and essential to the economies of Arctic nations.
Frey’s research suggests there is much more algal life beneath the ice than previously thought. Because the Arctic isn’t a solid sheet of ice but consists of sheets of ice broken up by ponds of melted water, light penetrates the surface like skylights into the world below.
There are plenty more surprises to find beneath the frozen sea even in the Antarctic winter
“There’s enough light in the water column to sustain photosynthesis,” she says, “and that’s pretty remarkable, so there can be quite a productive ecosystem even when sea ice is present.”
Meanwhile, at the other end of the planet, the oceans come alive with plant life in the summer. Even in the dead of winter, there are plenty of surprises to be found beneath the frozen sea. If you’re brave enough.
“It’s -27C (-16F) outside, and you’re essentially immersed in -1.8C (28.7F) water, which is the temperature at which sea water freezes, so you need to stay as warm as possible,” says Nadia Frontier, a British Antarctic Survey (BAS) marine biologist and diver. She is in her lab at the BAS research station in the Antarctic Peninsular when we speak, but thanks to the wonders of satellite internet, we can still connect on Zoom.
Aside from multiple layers of warm and protective clothing, winter diving in Antarctica requires cutting two holes in the sea ice – one to enter the water and one for an emergency exit. This could be used if a seal decided to hunt in the first hole, or if a leopard seal or killer whale approached. Leopard seals are known to be dangerous to humans, and killer whales may also pose a threat.
“The hole is like a bath because it’s such a narrow opening, and your tanks are hitting the edge of the ice because it’s so thick,” Frontier says. “But it’s incredible once you’re in and beneath the ice.”
“I find the explosion of lifeforms absolutely fascinating – you go down underwater and you could have hundreds of different species within a single metre,” she says. These range from microscopic organisms to tiny marine animals to massive sponges, crabs, and starfish.
“And you have virtually every color of the spectrum – from pink sea cucumbers to purple sea fans with blue in them to vibrant yellow sponges.”
“There’s also a phenomenon known as gigantism,” Frontier explains. “Because the water is so cold, it can absorb more oxygen, allowing species to grow to enormous sizes without being limited by a lack of oxygen in the water.”
Life below freezing operates on a different timescale, putting our human lifespans into context. “Some sponges have been dated to be thousands of years old,” says Huw Griffiths, a BAS marine biogeographer.