Warming climate alters Antarctic ecosystems

By Eric Niiler

Marine ecologist Dan Costa first came to Antarctica as a graduate student in 1979. Now a professor at the University of California, Santa Cruz, Costa and one of his own grad students look for Weddell seals at a spot on the Ross Sea ice edge, a few miles from the main US Antarctic base at McMurdo Sound. The seals are easy to spot – they’re huge black blobs sunning themselves on the white ice.

It’s all that ice that attracts most climate researchers to Antarctica. The frozen continent holds more than two thirds of the planet’s fresh water, and as it heats up rapidly, the possibility of much of that ice melting makes Antarctica ground zero for climate change research.

But scientists like Costa are also examining what climate change is doing to Antarctic creatures and ecosystems.

Costa stops his snowmobile about 50 feet away from the seals and walks across the snow toward one of them. The animals don’t seem disturbed by people. Costa’s able to walk right up to one to check out its coat and evaluate whether it has yet gone through its seasonal molt, or shedding of its winter fur. Costa needs to know because he uses these seals to explore the waters under the ice with a special device attached to the animal’s head, which he can do only when the seals have already molted.

The female seal breathes heavily as Costa checks it out and establishes that it hasn’t molted, and so can’t yet be fitted with the device.

If it could, Costa would anesthetize the seal, shave a patch of the top of her head and glue on the small instrument with plain old hardware store epoxy. He says the critters don’t seem to mind.

“It will come up from anesthesia and it will take off, he says.

“Well, actually, it will just sit here.”

Lazy on land, the seals swim long distances underwater for fish. With one of Costa’s gizmos along for the ride, these foraging trips give him data he needs to better understand the ecosystem in waters here near McMurdo Sound. He can then compare it with data he’s collected using elephant and crab eater seals in the sea off the Antarctic Peninsula two thousand miles away

The climate there is rapidly changing. Since the 1950s, the waters around the peninsula have warmed roughly a-half degree Celsius, or almost one degree Fahrenheit, while the air temperature has jumped six degrees Celsius, or almost 11 degrees Fahrenheit. This means there’s less sea ice for the elephant and crab eater seals there to haul out on to rest, mate and molt.

Costa says his data suggests that while elephant seals here in the colder Ross Sea are still prospering, the seals off the peninsula are having a tough time.

Meanwhile, other researchers here are finding that the warmer waters are like a welcome mat to some other species.

Evolutionary biologist Sven Thatje, of the University of Southampton in England, has just produced what he says is the first compelling evidence that bottom-dwelling king crabs are moving into Antarctic waters.
Spying on bottom-dwelling creatures

Thatje recently returned to McMurdo after two months at sea aboard the Swedish icebreaker Oden, which towed a submarine of sorts to spy on bottom-dwelling creatures. Thatje found large populations of the crabs over 30 miles of transects along the western Antarctica peninsula.

That might not sound like a big deal, but Thatje sure thinks it is.

“It was quite impressive,” he says. And the consequences could be significant.

Cold waters have kept crabs away from Antarctica for 40 million. That means bottom-dwelling mussels, brittle stars, and sea urchins don’t have any defenses against them. They have thinner shells, for example. Meanwhile clams and worms, which usually burrow under the sea floor elsewhere, hang out on the bottom here in Antarctica and are also easy pickings for crabs.

“The Antarctic shelf communities are quite unique.” Thatje says. “And this is the result of tens of millions of years of evolution in isolation.”

But with the warming sea, that isolation is starting break down. Thatje predicted the crab invasion several years ago but was surprised at seeing so many arrive so quickly.

“The pace of changes that we are observing here in the Antarctic, which is the remotest continent on this planet, is quite frightening,” Thatje says.

He and his colleagues will spend the next few months analyzing 120,000 images from the seabed off the Antarctic Peninsula. He still doesn’t know if the crabs will invade and then leave, or colonize the area and destroy a diverse sea bottom world. But for scientists like him, it’s clear that the climate and the ecosystem are tightly linked.

It’s the same for ecologist David Ainley, who’s been studying penguins in Antarctica for more than 40 years. Ainley works for the Bay Area ecological consulting firm H.T. Harvey and Associates. He’s currently focused on a colony of Adelie penguins on Cape Royds, a 20 minute helicopter flight from McMurdo.

On a recent visit, the Cape Royds flock was made up mostly of young Adelies huddled together waiting for their parents to return with food, along with what Ainley calls “teenagers” investigating the scene and the learning the appropriate sorts of social sorts of responses to one another.
Penguins may benefit from climate change

Ainley says his research shows that this penguin population is doing well and is even benefiting from climate change, as increasing winds over the Ross Sea create more openings in the ice and make it easier for the penguins to get food.

Ainley says human activity has helped this population of penguins in other ways as well, such as eliminating some of their competitors for food, first through whaling in the 20th century and now through fishing for species like the Antarctic toothfish, also known as the orange roughy.

But as with seals, it’s a different story for penguins farther north on the Antarctic Peninsula, where the water and air are warming and sea ice is disappearing. Ainley says Adelie penguins there have declined by 90 percent in the past 20 years.

“It’s like removing the trees from the forest and the songbirds are going away,” Ainley says. “It’s the same thing. If you remove the ice, then this species is going to go away.”

Ainley predicts the Adelies on the Antarctic Peninsula won’t last more than a few decades. And the consequences could ripple through the ecosystem.

If the penguins, seals or other top predators disappear, Ainley says that opens the door to things like algae blooms and toxic jellyfish, changes which are already occurring in other parts of the Southern Ocean.

Not a simple story

“So there’s a lot of things going on,” Ainley says. “It’s definitely not a simple story.”

But it’s a story that Ainley believes will be told more and more as climate change begins to affect other parts of the world as well.

Ainley says he believes the tipping point has already been reached here in Antarctica, and that the pace of change will only get faster. That’s why he’s pushing some of the 60 nations that govern the continent to declare the Ross Sea a marine protected reserve.

He says the Ross Sea, at least, is expected to stay cold, so it may become the planet’s last refuge of both year-round ice and the animals that need it to live.