Will Climate Change Disrupt the Arctic Ecosystem?
WHOI biologist led ambitious expedition to the Bering Sea aboard the icebreaker Healy
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).
Slideshow
Slideshow
- In the spring of 2008, WHOI biologist Carin Ashjian led an expedition to the edge of the sea ice in the Bering Sea aboard the U.S. icebreaker Healy to study how climate change may affect organisms at the base of the Arctic food chain. (Photo by Carin Ashjian, Woods Hole Oceanographic Institution)
- From the deck of the USCGC Healy in the Bering Sea, WHOI research associate Phil Alatalo (left) and LTJG Stephen Elliot (right) deploy the Video Plankton Recorder, a towed instrument that takes images of small plankton near the bottom of the marine food chain. (Photo by Carin Ashjian, Woods Hole Oceanographic Institution)
- During her spring 2008 research cruise to study the Bering Sea ecosystem, chief scientist Carin Ashjian of Woods Hole Oceanographic Institution visited St. Lawrence Island. There, she met with hunters Tom Antoghame (left) and Merlin Koonooka (right) to hear their insights into the changing Arctic climate. (Photo by Jeffrey Stewart, U.S. Coast Guard)
- The icebreaker USCG Healy carried researchers to sample in nearly 200 locations in the Bering Sea, indicated by green dots on the red cruise track. The Alaskan coast is on the right, the Russian coast at the top left, the Aleutian Islands in the bottom right corner, and St. Lawrence Island is at the top center. (Map by Tom Bolmer, Woods Hole Oceanographic Institution)
- "By April 11," WHOI biologist Carin Ashjian wrote in a dispatch from the field, "the ice has increasing amounts of ice algae growing in and on the underside of the slabs, so that when the ice is turned over as the ship passes, the bottom is brown with algae. The darker brown color is ice algae growing in and on the ice underside. This algae is eaten by animals living in the ice or that scrape algae off the underside of the ice. The algae also eventually falls off of the ice and may be eaten by plankton in the water column or sink to the seafloor where it is eaten by the benthos (seafloor-swelling organisms)."
(Photo by Carin Ashjian, Woods Hole Oceanographic Institution) - On a separate expedition, Andrew Juhl, a scientist at Lamont-Doheryt Earth Observatory, took this photo of a freshly extracted sea ice core pulled from a hole drilled in the ice. The brown-colored band at the bottom of the ice core shows algae that grow the underside of the ice. (Photo by Andrew Juhl, Lamont-Doherty Earth Observatory)
- In this microscopic view of a thin section of natural sea ice, note the open spaces within the ice matrix (sea ice is porous, unlike freshwater ice). Ice algae (diatoms) live within these open spaces. These pigmented organisms discolor the bottom layer of ice cores.
(Photo by Christopher Krembs, University of Washington)
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- Carin Ashjian's Lab My research focuses on a variety of problems in biological oceanography and zooplankton ecology and particularly on how physical and biological processes together define zooplankton biogeography, structuring of zooplankton communities and populations, zooplankton population abundance, and the transformation of organic material.
- The Bering Sea Integrated Ecosystem Research Program
- Life in the Arctic An article by Carin Ashjian from Oceanus magazine
- Writer Gaelin Rosenwax wrote about Carin Ashjian's cruise aboard USCGC Healy
- Abandoned Walrus Calves Reported in the Arctic from Oceanus magazine