Arctic climate researchers zoom in on plankton
They’re not recognizable like polar bears or whales. But phytoplankton are a key part of life in the Arctic — and now, they’re at the center of a new research effort to predict how the region will respond to climate change.
Almost every animal in the Arctic eats — or eats something that consumes — phytoplankton. They’re tiny specks of algae that usually blossom into big clouds out in the ocean in the springtime.
But that’s not what Kevin Arrigo saw a few years back. He was in the Chukchi Sea for a research cruise funded by NASA.
“The deeper we went into the ice, the more phytoplankton there were. They reached amazing concentrations, to the point where it was the largest bloom anybody had ever seen anywhere in the world’s oceans. And it was under three feet of ice.”
Phytoplankton need two things to grow — nutrients and light.
In the past, scientists have assumed that sun can’t get through thick Arctic sea ice. But as the earth warms up, the ice is thinning out. And it’s definitely easier for light to get through.
“The thing we didn’t know was what the nutrient distributions look like — particularly before the bloom starts, early in the spring,” Arrigo says. “Because nobody’s ever been in the Chukchi Sea, sampling the entire ocean from top to bottom at that time of year.”
That’s what Arrigo set out to do this spring, with a team of about 40 other scientists. They examined the base of Arctic food web in the Chukchi Sea, with a grant from the National Science Foundation.
That paid for a trip aboard the Coast Guard icebreaker Healy. Arrigo says it was an ideal vessel, but there were some roadblocks it couldn’t plow through.
“We were really unlucky in that everything happened late this year. The melt ponds never formed while we were out there. The phytoplankton under the ice never developed because there was never enough ice. But we were really happy with the results because we know now that the whole region — the entire Chukchi Sea — is really prime habitat for these things to develop.”
Bob Pickart is the lead physical oceanographer for this project. He says he’s coming away with hundreds of water samples from up and down the Chukchi Sea — all loaded down with nutrients.
“These nutrients –- they spur the growth of the phytoplankton. And then from there on, it just spirals right up the food chain,” Pickart says. “So it’s like the base of the ecosystem. This is what it’s all about.”
Pickart says there’s a lot of work ahead to analyze the samples. His findings will be shared with other scientists on the team.
“They have to know, why are the nutrients in the water in the first place. How did they get there? Where does the water go? What’s the timing of the water? So they have to know all about the physics of the circulation on the Chukchi Shelf in order to then understand the biology.”
Arrigo is a biologist, and he has his own questions — about the timing of the phytoplankton bloom.
“Productivity has been shifting earlier and earlier, because the ice is melting earlier and earlier. But now the bloom — the productivity — is not even waiting for the ice to melt,” Arrigo says.
If it’s coming earlier than animals are used to:
“What’s going to happen? Are they going to produce their offspring at a point when the bloom’s already happened, it’s too late, there’s no food in the water?”
Arrigo says the best chance of predicting that is to understand how the phytoplankton are interacting with their environment right now.
That’s why the researchers are hoping to return to the Chukchi Sea next year to gather more water samples, and a better look at the bottom of the Arctic food web.