To understand how [ocean acidification] will alter the seas, The Seattle Times crisscrossed the Pacific Ocean from Papua New Guinea to Alaska, interviewed nearly 150 experts and people most likely to be affected, and reviewed most of the peer-reviewed studies.

The Times found that ocean acidification is helping push the seas toward a great unraveling that threatens to scramble marine life on a scale almost too big to fathom — and far faster than first expected.

Already, it has killed billions of oysters along the Washington coast and at nearby hatcheries. It’s helped destroy mussels on some Northwest shores. It is a suspect in the softening of clam shells and in the death of some baby scallops. It already is dissolving tiny plankton, called pteropods, in Antarctica that are eaten by many ocean creatures — and that wasn’t expected for 25 years.

The problem: When carbon dioxide mixes with water, it takes on a corrosive power that erodes some animals’ shells or skeletons. It also robs the water of ingredients animals use to grow shells in the first place.

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Sea-chemistry changes are coming as the oceans also warm, and that’s expected to frequently amplify the impacts.

This transformation — once not expected until the end of the century — will be well under way, particularly along the West Coast, before today’s preschoolers reach middle age.

“I used to think it was kind of hard to make things in the ocean go extinct,” said James Barry, of the Monterey Bay Aquarium Research Institute in California. “But this change we’re seeing is happening so fast it’s almost instantaneous. I think it might be so important that we see large levels, high rates of extinction.”

Globally, the world can arrest much of the damage by bringing down CO2 emissions soon. But the longer it takes, the more permanent these changes become.

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Species’ reaction to high CO2 can vary dramatically. Acidification can kill baby abalone and some crabs, deform squid and weaken brittle stars while making it tough for corals to grow. It tends to increase sea grasses, which can be good, and boost the toxicity of red tides, which is not. It makes many creatures less resilient to heavy metal pollution.

Roughly a quarter of organisms studied by researchers in laboratories actually do better in high CO2. Another quarter seem unaffected. But entire marine systems are built around the remaining half of susceptible plants and animals.

“Yes, there will be winners and losers, but the winners will mostly be the weeds,” said Ken Caldeira, a climate expert at Stanford’s Carnegie Institution for Science, who helped popularize the term ocean acidification.

Many species, from sea urchins to abalone, do show some capacity to adapt to high CO2. But they may not have time.

“It’s almost like an arms race,” said Gretchen Hofmann, a marine biologist at theUniversity of California, Santa Barbara. “We can see that the potential for rapid evolution is there. The question is, will the changes be so rapid and extreme that it will outstrip what they’re capable of?”

Already, the oceans have grown 30 percent more acidic since the dawn of the industrial revolution — 15 percent since the 1990s. By the end of this century, scientists predict, seas may be 150 percent more acidic than they were in the 18th century.

In fact, the current shift has come so quickly that scientists five years ago saw chemical changes off the U.S. West Coast that hadn’t been expected for half a century.

Read the entire story on SF Gate.