Posted on behalf of Wendee Holtcamp, blogging for Nature aboard the research vessel Thomas G. Thompson
We’re halfway through the summer cruise on the RV Thompson, and people have settled into their routines: doing krill grazing experiments, scouting for birds, filtering phytoplankton, gathering fish larvae, collecting mud. The scientists have devised ways to entertain themselves at sea. Today we visited a 2,700 meter-deep station off the continental shelf where we sent Styrofoam cups undersea, attached to the CTD. With around 4,000psi of pressure at that depth, they came back up thimble sized.
And the mud team created a wall for Post-it note science haikus, such as:
Cold van chills my soul
But gas exchange warms my heart
Flux like the seasons
We also skirted past St. George and St. Paul Islands in the Pribilofs. Besides one glorious day of sunshine, the grey days come and go with mist, fog, and rain, so you can imagine everyone’s excitement at the diversion of seeing land – plus, in previous years a lot of pollock, krill, and seabirds were observed here. The Pribs provide nesting grounds for 2.5 million seabirds and the world’s largest breeding site for northern fur seals. We spotted a couple dozen sunning on the rocky shoreline, plus a mother and baby orca. After being hunted to near extinction, the Pribilof fur seal population nearly recovered, and in the 1950s their numbers began steadily dropping; no one knows why. Steller sea lions have also recently declined here. Several Bering Sea Project marine biologists study these species, but not on this cruise. We do have Sarah Jennings and Brian Hoover from the North Pacific Pelagic Seabird Observer Program on board (see below), and they report any marine mammals spotted to the other scientists.
Despite much anticipation, scientists did not catch many fish larvae, krill, or zooplankton in the stations around the Pribilofs. Alexei Pinchuk, a marine scientist on board from University of Alaska-Fairbanks in Seward, found cold-loving amphipods – types of zooplankton – not seen in previous years that may be invading from Arctic seas further north. There are also more cold-weather copepods, the most abundant plankton here.
How is this impacting seabirds? I went up to the pilothouse to scout sky and sea with the bird team. As we approached St. Paul, we started seeing flocks of least auklets – tiny dark birds that they nicknamed ‘flying avocados,’ plus horned and tufted puffins, black-legged kittiwakes, and thick-billed and common murres – ecological equivalents of penguins in the southern hemisphere. But like the aquatic samplers, the bird team also didn’t see as many birds near the Pribilofs as expected.
Hoover and Jennings work under U.S. Fish & Wildlife Service biologist Kathy Kuletz on a broadscale distribution survey of Bering Sea birdlife. Kuletz is concerned about species nesting on these islands. “Seabirds, as apex predators in the marine ecosystem, are highly visible at sea, and their distribution is affected by changes in prey availability,” says Kuletz. “They can only forage so far before it affects their ability to raise chicks. Since about 85% of seabirds in US waters occur in Alaska, where these impacts are greatest, it is an important question for seabird conservation and management, as well as ecosystem management.”
With so many species faring poorly with three icy-cold years in a row, some may wonder whether a warming climate may actually benefit Bering Sea organisms. In an ecosystem used to regular oscillations of colder and warmer years, a general warming trend – or even more extreme fluctuations – will probably benefit some species at the expense of others, causing cascading effects through the ecosystem.
David Shull, chief scientist on board, told me that because the Bering Sea lies right at the interface between the always-frozen Arctic and the always-liquid seas further south it’s a great system to study climate change. “Think of it like a glass of water. At 0°C, it’s ice,” says Shull. “If you increase the temperature by just one degree, it completely changes. And so does everything else.”
NOAA oceanographer and co-chief scientist, Nancy Kachel, added, “What we learn in the Bering Sea will help us understand what the Arctic Sea may be like once it becomes seasonally, rather than permanently, frozen.”
Previous posts:
Wild Weather, Damaged Equipment & the Oscillating Control Hypothesis
Setting sail for climate change research
Images: Wendee Holtcamp