Ocean acidification may be trouble for Alaskan fish

Yereth Rosen, Reuters 3 Sep 09;

ANCHORAGE, Alaska (Reuters) - The waters off Alaska, teeming with enough fish to support more than half the U.S. commercial seafood catch, face a new threat -- increasing acidification from the same atmospheric carbon linked to global warming.

Although nobody knows for sure what the effects of higher acidity levels will be, reports of smaller salmon catches are worrying scientists and cast a pall over the state's $3.6 billion fishing industry.

"These waters are becoming corrosive and harmful to marine organisms," said Jeremy Mathis, an oceanographer with the University of Alaska Fairbanks' School of Fisheries and Ocean Sciences.

"I can tell you unequivocally, and I think 99.9 percent of scientists would agree, the polar oceans are becoming more acidic faster than the tropical oceans," said Mathis. "What we can't do is tell you the exact rate at which that is happening."

Mathis last month released findings that water samples from the Gulf of Alaska were growing noticeably acidic. He found similar results in Alaska's Bering and Chukchi Seas.

Around the nation, the U.S. National Oceanic and Atmospheric Administration (NOAA) has 40 to 60 scientists working at least part time on the subject, said Doug DeMaster, director of the agency's Alaska Fisheries Science Center.

"We view it as the evil twin of all the problems associated with global warming," said DeMaster, who is based in Juneau. It is a subject NOAA takes seriously, he said, but it still does not have enough knowledge to predict the effects.

HEATING UP FAST

The chemical process resulting in ocean acidification is simple: Carbon dioxide combines with molecules in the water to make carbonic acid. "It's exactly what happens when you make club soda," said Jeff Short, a retired NOAA researcher now a Juneau-based advocate with the environmental group Oceana.

The very characteristics that make waters off Alaska the sites of world-class fisheries also cause high rates of carbon absorption.

Cold water holds more carbon dioxide than warm water. The abundant phytoplankton in the water also absorbs carbon. And the shallow continental shelf that is so important to the teeming marine life prevents significant mixing with deeper waters to dilute the carbon.

All those factors "precondition the water to become acidic faster than the tropical Pacific, for example," said Mathis. Because of that, the far-north waters off Alaska are showing acidification effects earlier than waters in other parts of the world, according to Mathis' research.

Early effects are already apparent in Antarctic waters, where marine snails are less able to form their shells. Those snails are small, but are vital to the marine food chain, scientists say.

It is unclear what the effects will be over time, said Short, who previously worked on a laboratory project testing the effects of acidic waters on crab development.

"When you change the acidity in the ocean, it changes so many things that it's really difficult to figure how it's all going to wash out," he said.

FISHING INDUSTRY WORRIED

Questions are already being raised about some poor salmon catches in normally dependable fishing areas. Commercial and sport fishermen on the Kenai Peninsula south of Anchorage have reported that salmon are on average about 20 percent smaller than their normal size, Mathis said.

"While we can't say that's because of ocean acidification, we can say that ocean acidification is going to set the stage for those types of results," he said.

Signs of acidification are worrying Alaska fishermen.

"I'd say probably on a scale of 1 to 10, it would be 20 or 30," said Mark Vinsel, executive director of United Fishermen of Alaska, the state's largest commercial fishing organization. "It's dire, and it's a big concern."

The wholesale value of Alaska's commercial seafood catch was $3.6 billion in 2007, with much of the activity concentrated in the Bering Sea, according to a recent study by a private economic consultant. In addition, sport fishing in Alaska is an industry worth nearly $1.4 billion, according to the state Department of Fish and Game.

Given the financial issues at stake, researchers are rushing to examine potential impacts to fisheries.

Mathis is making voyages in mid-September to check ocean conditions in the Gulf of Alaska and Bering Sea, while other scientists are studying the impact on Alaskan pollock and shellfish.

Research on the subject is just beginning, said Mike Sigler, who is leading ocean-acidification studies for the Alaska Fisheries Science Center. "There's no effects directly attributable to ocean acidification. But I think the problem is we don't understand the effects," said Sigler.

(Reporting by Yereth Rosen, editing by Bill Rigby and Todd Eastham)