A Greenpeace ship flies a banner demanding "Stop climate change here" as it welcomes flights into nearby Copenhagen airport. Monday Dec. 7. 2009. (AP Photo/Nanna Kreutzmann/POLFOTO)

“Jeremy Brown, a fisherman from the Pacific Northwest, is pulling things from the ocean he says are so disturbing that he came to Washington to warn U.S. lawmakers about it.  “This is not overfishing, this is something far larger,” said Brown, one of 10 people who met with lawmakers and legislative aides this week on behalf of the Sustainable Fisheries Partnership, a San Francisco-based group that advises seafood producers on fishing practices.

The group said the ocean is becoming more acidic because of carbon-dioxide emissions that are damaging coral reefs, decimating populations of tiny animals at the base of the food chain and eating away at the shells of clams, mussels and oysters.

“Every so often we snag a piece of coral on the gear,” Brown, of Bellingham, Washington, said in an interview. “It doesn’t look healthy, the color has gone out of it. The evidence is that we have instabilities in the system, and this last year was really scary.”

Rajendra Pachauri, chairman of a United Nations scientific advisory panel on climate change, highlighted ocean acidification this week in remarks at the global conference on greenhouse gases in Copenhagen.

World trade in seafood products is valued at $100 billion and feeds 3 billion people, according to the fisheries partnership. That production is threatened by rising acidity, caused by the ocean absorbing more carbon from the atmosphere, and by the effects of agricultural runoff, said Mark Green, a professor of oceanography at St. Joseph’s College of Maine in Portland, who accompanied the fishermen on the trip.

The group met with Republican Senators Susan Collins of Maine and Lisa Murkowski of Alaska and aides to other coastal senators during a three-day visit.

Small snails and other tiny animals at the base of the food chain are disappearing at alarming rates, jeopardizing the health of pink salmon and other fish that feed on them, said Green, who lives on Maine’s Peaks Island.

“What we see with ocean acidification, we are seeing on time scales that are far more rapid than any sort of changes we are seeing on terrestrial systems,” said Green. “People who weren’t able to agree with climate-change science will have an easier time accepting the science on acidification.”

The U.K.-based Marine Climate Change Impacts Partnership reported in April that acidification has increased 30 percent since the start of the industrial revolution, a rate faster than at any time in the last 65 million years

More acidic water eats away at clam, oyster and mussel shells, said Mark Wiegardt, who raises shellfish larvae in Tillamook, Oregon, and sells them to commercial harvesters.

“The shells stop growing and the acidic water literally dissolves the calcium of the shells,” Wiegardt said.

Wiegardt said he has seen an 80 percent cut in production in [...]