Will Climate Change Disrupt the Arctic Ecosystem?

After long, dark winters, sunlight returns to the Bering Sea in spring, re-launching a bountiful food chain that fills the Arctic with life. In March 2008, an ambitious research team, led by biologist Carin Ashjian of Woods Hole Oceanographic Institution (WHOI), launched into the Bering Sea to learn more about how its complex ecosystem works and how it may be affected by impending climate change.

As increasing sunlight penetrates the sea ice, ice algae grow on its underside. Rising temperatures begin to melt the ice, releasing the algae that drifts through the ocean and to the seafloor. The algae become food for planktonic copepods and krill and seafloor-dwelling urchins and mussels—lower links in the ocean food chain that feed fish, seabirds, whales, seals, walruses, polar bears, and humans at the top. Will Earth’s changing climate, proceeding fastest in the vulnerable Arctic region, disrupt the choreography of this age-old ecosystem?

To find out, 46 researchers with various scientific expertise, from 18 universities, research institutions, and agencies, headed on a 39-day voyage on the U. S. Coast Guard Cutter Healy from March to May 2008 for a coordinated study of the marine ecosystem.

The research team sampled in nearly 200 locations across the Bering Sea using a variety of oceanographic tools to collect water, seafloor sediment, and plant and animal plankton, and to take video of plankton and of algae growing under the ice. Some researchers measured plankton growth and reproduction as spring progressed, tracking temperature and nutrient levels in the water  that influence spring plankton growth. Other researchers observed seabirds. The Healy, an icebreaker, worked not only in open water, but near the retreating ice edge, and in areas of thick ice where researchers disembarked to take ice cores and used a small remotely operated vehicle to survey under the ice for ice algae.

This was the second of three Bering Sea cruises on Healy planned for 2008, part of a large six-year project from 2007 to 2012. The first cruise, in mid-to-late March, was near St. Lawrence Island, a large remote island in the north Bering Sea where scientists studied walrus and their food supply and collected seawater, sediment, and biological specimens.

During the second cruise, Ashjian flew by helicopter from the ship to St. Lawrence Island, where she met with native hunters in the village of Gambell and told them about the research project and its findings.

“The hunters are very aware of and interested in ongoing climate change in the Bering Sea,” she said. “It was interesting hearing their insights into the changing of the seasons, how the ocean and ice are changing in recent years, and how this is impacting the distribution of the animals on which they depend for food—whales, seals, walrus, birds, and crabs.”

The cruise yielded valuable information about the current state of the Bering Sea, Ashjian said, though it was an exceptionally icy spring that delayed the full phytoplankton bloom. Ashjian said scientists gained insights into the important role of sea ice and ice algae in the Arctic ecosystem.

The cruise was supported by a partnership of the National Science Foundation’s Bering Sea Ecosystem (BEST) program and the North Pacific Research Board’s Bering Sea Integrated Ecosystem Research Program (BSIERP).