Radio Script
1998

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Sea Changes in North Pacific
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STORY: No one could have predicted that salmon returns to Alaska over the past couple of years would have collapsed exactly when they did, but scientists have been expecting salmon runs to become smaller.

Milo Adkison is an assistant professor of fisheries at the University of Alaska Fairbanks.

ADKISON: "Predicting when it's going to happen is really difficult. But the idea that it's bound to happen is pretty obvious to anyone who knows much about the history of Alaska's salmon fisheries."

Adkison says salmon returns to Alaska have always fluctuated on a kind of boom and bust cycle. For the past 20 years or so, salmon returns to Alaska have often set new records. But there are signs the boom may be coming to an end. Last summer, for example, the strongest El Nino in 50 years warmed the North Pacific Ocean. The damaging effect it had on the food chain was almost instant. First to go were the plankton. Then the fish that feed on plankton disappeared. Finally, scientists and fishermen reported seeing thousands of dead seabirds.

Tom Weingartner is an oceanographer at the University of Alaska Fairbanks.

Weingartner: "It's a little hard to say what the time scales are, because there are a variety of time scales, but we have seen some rather striking ones in the last year or so. Last summer, we noticed an unusual warming that was confined to the surface layers of the Gulf of Alaska and the Bering Sea. Those temperature changes were about two to three degrees above normal beginning about the middle of the summer, and continuing through the fall. Beyond the fall, the temperature changes were even more dramatic. They weren't confined to just the surface, but at least in the Gulf of Alaska they extended down at least 250 meters or so on the continental shelf. They were about two to three degrees above normal and they continued through the spring. Those are large changes for the ocean. It's a lot of heat."

Those few degrees threw a monkey wrench into the ecosystem in the short term, and it may have been enough to lower salmon returns. But scientists say there are even more ominous long-term changes occurring at sea. One such change is a decline in the ocean's production of plankton, the single most important species in the ocean food chain.

Don Schell is a researcher and director of the Institute of Marine Science at the University of Alaska Fairbanks. He calculated ocean productivity by measuring the amount of carbon in the baleen of bowhead whales. The carbon comes from the whale's consumption of plankton. Bowhead whales add a layer of baleen each year, much like tree rings. Scientists can examine the layers of baleen and measure how ocean productivity has changed over time.

SCHELL: "The record shows that from 1946 to 1963 everything went along fairly smoothly at a relatively high level of productivity. And then in the mid-60s it increased and peaked at around 1965, 1966. Then ocean plankton productivity began a steady decline and since the mid-1970s it has gone down and down and down. The last samples we have from 1994, 1995 and 1996 show the lowest primary productivity in the Bering Sea over this 50-year period."

The story told in the baleen of bowhead whales is helping scientists explain the decline of species such as Steller sea lions, seabirds and fish that ultimately depend on plankton. Schell says the overall productivity of the North Pacific Ocean has declined some 40 percent. That means the ocean may not be able to support the variety of sea life that it once did.

OUTRO: For Arctic Science Journeys, this is Doug Schneider, reporting from Fairbanks, Alaska.