News - Local News

POSTED: Sunday, Jun. 21, 2009

WWU researcher studying how climate change affects Bering Sea ecosystem

BELLINGHAM - David Shull's study of the critters living in the mud at the bottom of the Bering Sea could help reveal how climate change is affecting the world's largest commercial fishery, as well as the people and wildlife dependent on that region in Alaska.

Shull, an assistant professor of environmental science at Huxley College of the Environment, is among 94 scientists from 10 states and two countries who have teamed up for a $52 million study of the ecosystem of the eastern Bering Sea shelf, which lies between the Aleutian Islands and St. Lawrence Island.

They hope to put together "a holistic picture of how climate change affects the Bering Sea, all the way up the food chain to people," Shull said of the larger effort, which began in 2007 and will continue until 2012.

Shull's research is being funded by a four-year grant from the National Science Foundation that totals $367,764. It's set to end next August, unless Shull gets the additional funding he's seeking.

His focus is on benthos, which are the organisms such as worms and clams living in the sediment on the sea floor. He has traveled to the remote region, which is covered by ice in winter, since 2007 for his research. He left in mid-June for more field work, this time on board the 280-foot research vessel Knorr.

He'll be on the ship until mid-July. Also on board and participating in the study is Maggie Esch, a Western Washington University graduate student.

Why does the Bering Sea matter?

"It's incredibly productive and important," the 43-year-old Shull said.

Nearly half of the seafood eaten in the U.S. comes from that part of the world, and much of the commercial fishing fleet plying its waters is moored in Seattle. Some of the fishers live in Bellingham. The sea's catch is valued at some $1 billion annually. (The tough fishers who work the Bering's frigid, deadly waters - and the sea itself - have been made famous by the "Deadliest Catch" series on Discovery Channel).

The indigenous Yup'ik and Aleuts have for centuries depended on that ecosystem's abundance for their very survival. About 36 million seabirds breed in the region, while whales and seals travel great distance to feed and mate there.

At the root of that abundance is the interaction between melting sea ice and the currents that bring in nutrients from the North Pacific Ocean to fertilize algae blooms. The algae feed tiny animals called zooplanktons, which in turn are eaten by larger creatures, and on up the food chain.

Part of the scientists' research focuses on the annual advance and retreat of that sea ice, and the factors affecting it. In winter, ice forms and advances for as much as 558 miles, until it more or less covers the sea.

But, there's also a century-long warming trend that is affecting the Bering Sea, Shull said, and satellite images taken over the past three decades show the ice is retreating earlier and earlier.

Within the larger trend are 10- to 20-year cycles that affect how warm or cold the sea will be in any given year. Shull's research during the past three seasons has occurred during cold years.

Still, the sea is warming overall and scientists hypothesize that shift - bringing with it thinner ice - will affect the abundance and distribution of fish in the region. That, in turn, could mean a change in the home ports for commercial fishermen.

In mid-June, Shull flew into Dutch Harbor in Alaska, where he boarded the Knorr. Temperatures will be warmer than those he experienced during earlier trips in April through May, when they hovered at freezing or below.

During those spring trips, Shull and other scientists did their research on the U.S. Coast Guard ice breaker Healy, as they looked for and found massive algae blooms on the edges of the ice.

"There was so much algae in the water, it was like soup. It was like a real thick ... like a French onion soup," Shull said.

To look at what's going on beneath the water and ice, Shull uses a piece of equipment called a multi-corer. It slowly pushes cylindrical tubes into the mud on the sea floor and lifts out undisturbed samples, which include the overlying water. The multi-corer has taken samples from as deep as 11/2 miles underwater.

He's analyzing the samples to look at the impact of climate change on the creatures in the mud, which are affected by the timing of the retreating sea ice.

In a cold year, for example, the ice melts back slowly enough that light helps stimulate a massive algae bloom, or growth. That algae forms the building block of the food web and in turn jump-starts the sea's productivity. In a cold year, Shull believes, that algae - or phytoplankton - finds its way down to the critters at the bottom, where they become food.

In a warm year, the ice melts while it's too dark for the algae to start growing on the ice's edge. That takes longer for the region's food network to start.

"But by that time, krill and other (zoo) planktons, their numbers are elevated and they eat all the algae and it never makes it to the bottom," Shull said.

That in turn could affect the nutrients the creatures in the mud can put back into the water, with possibly widespread repercussions going all the way up the food chain to people.

"The big picture, then, is that as the Bering Sea warms - this is the big hypothesis that drives my research - there's less organic matter hitting the sea floor, the fewer animals inhabit the sediment, the rate of sediment flushing is less so that reduces nutrient recycling back into the water column," Shull explained.

He added: "So, potentially, as the ice melts back earlier and earlier and you have fewer animals living in the sediment and there's less efficient recycling of nutrients, overall productivity could drop."

LEARN MORE

Additional information about the Bering Sea, its importance and the six-year study into its ecosystem may be found online at:

• bsierp.nprb.org - Discusses the six-year study conducted by a team of 94 scientists, including David H. Shull, an assistant professor of environmental science at Western Washington University's Huxley College of the Environment. His Web site is ac.wwu.edu.

• beringclimate.noaa.gov - Information gathered and presented by the National Oceanic and Atmospheric Administration.

• polardiscovery.whoi.edu - Woods Hole Oceanographic Institution, which features information about the Bering Sea's ecosystem.