Ocean acidification, the lesser-known twin of climate change, threatens to scramble marine life on a scale almost too big to fathom.

NORMANBY ISLAND, Papua New Guinea — Katharina Fabricius plunged from a dive boat into the Pacific Ocean of tomorrow.

She kicked through blue water until she spotted a ceramic tile attached to the bottom of a reef.

A year earlier, the ecologist from the Australian Institute of Marine Science had placed this small square near a fissure in the sea floor where gas bubbles up from the earth. She hoped the next generation of baby corals would settle on it and take root.

Fabricius yanked a knife from her ankle holster, unscrewed the plate and pulled it close. Even underwater the problem was clear. Tiles from healthy reefs nearby were covered with budding coral colonies in starbursts of red, yellow, pink and blue. This plate was coated with a filthy film of algae and fringed with hairy sprigs of seaweed.

Instead of a brilliant new coral reef, what sprouted here resembled a slimy lake bottom.

Isolating the cause was easy. Only one thing separated this spot from the lush tropical reefs a few hundred yards away.

Carbon dioxide.

In this volcanic region, pure CO 2 escapes naturally through cracks in the ocean floor. The gas bubbles alter the water’s chemistry the same way rising CO 2 from cars and power plants is quickly changing the marine world.

In fact, the water chemistry here is exactly what scientists predict most of the seas will be like in 60 to 80 years.

That makes this isolated splash of coral reef a chilling vision of our future oceans.

‘ High rates of extinction’ to come?

Imagine every person on Earth tossing a hunk of CO 2 as heavy as a bowling ball into the sea. That’s what we do to the oceans every day.

Burning fossil fuels, such as coal, oil and natural gas, belches carbon dioxide into the air. But a quarter of that CO 2 then gets absorbed by the seas — eight pounds per person per day, about 20 trillion pounds a year.

Scientists once considered that entirely good news, since it removed CO 2 from the sky. Some even proposed piping more emissions to the sea.

But all that CO 2 is changing the chemistry of the ocean faster than at any time in human history. Now the phenomenon known as ocean acidification — the lesser-known twin of climate change — 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.

Here’s why: When CO 2 mixes with water it takes on a corrosive power that erodes some animals’ shells or skeletons. It lowers the pH, making oceans more acidic and sour, and robs the water of ingredients animals use to grow shells in the first place.

Acidification wasn’t supposed to start doing its damage until much later this century.

Instead, changing sea chemistry already has killed billions of oysters along the Washington coast and at a hatchery that draws water from Hood Canal. It’s helping destroy mussels on some Northwest shores. It is a suspect in the softening of clam shells and in the death of baby scallops. It is dissolving a tiny plankton species eaten by many ocean creatures, from auklets and puffins to fish and whales — and that had not been expected for another 25 years.

And this is just the beginning.

Ocean acidification also can bedevil fish and the animals that eat them, including sharks, whales, seabirds and, of course, bigger fish. Shifting sea chemistry can cripple the reefs where fish live, rewire fish brains and attack what fish eat.

Those changes pose risks for our food, too, from the frozen fish sticks pulled from the grocer’s freezer to the fillets used in McDonald’s fish sandwiches, to the crab legs displayed at Pike Place Market, all brought to the world by a Northwest fishing industry that nets half the nation’s catch.

And this chemical change is not happening in a vacuum.

Island reefs of Papua New Guinea offer a window on our future, while fishing ports in Alaska and along the Washington coast show how the deterioration of food webs could strike close to home.

Globally, overfishing remains a scourge. But souring seas and ocean warming are expected to reduce even more of the plants and animals we depend on for food and income. The changes will increase ocean pests, such as jellyfish, and make the system more vulnerable to disasters and disease. The transformation will be well under way by the time 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, we can arrest much of the damage if we bring down CO 2 soon. But if we do not, the bad news won’t stop. And the longer we wait, the more permanent the change gets.

“There’s a train wreck coming and we are in a position to slow that down and make it not so bad,” said Stephen Palumbi, a professor of evolutionary and marine biology at Stanford University. “But if we don’t start now the wreck will be enormous.”

You might think that would lend the problem urgency. So far, it has not.

Combined nationwide spending on acidification research for eight federal agencies, including grants to university scientists by the National Science Foundation, totals about $30 million a year — less than the annual budget for the coastal Washington city of Hoquiam, population 10,000.

The federal government has spent more some years just studying sea lions in Alaska.

So to understand how acidification could transform marine life, The Seattle Times crisscrossed the world’s greatest ocean, from the sun-dappled reefs of the South Pacific to the ice-encrusted surface of the Bering Sea.

How much carbon are we putting into the ocean? Mark Nowlin / The Seattle Times

Acidification will strike every ocean, and no one can predict exactly how things will look — the seas are too complex for that.

But the island reefs of Papua New Guinea’s Milne Bay province offer a window on our future, while fishing ports in Alaska and along the Washington coast show how damage to fish brains and the deterioration of food webs may strike close to home.

A disturbing glimpse of the future

Papua New Guinea’s Solomon Sea island vents are remarkable because of where they are: in shallow waters normally fringed by coral reefs as striking as fields of wildflowers.

These remnants of earthquakes or eruptions come in all shapes: mini-geysers, a giant crack that burps basketball-size blobs of gas, rows of pinprick holes in the sand that exhale curtains of Champagne bubbles.

As Fabricius glided through earlier this year, a bleak portrait emerged.

Instead of tiered jungles of branching, leafy reefs or a watery Eden of delicate corals arrayed in fans, she saw mud, stubby spires and squat boulder corals. Snails and clams were mostly gone, as were most of a reef’s usual residents: worms, colorful sea squirts and ornate feather stars.

The culprit: excess carbon dioxide. When CO 2 hits seawater it becomes carbonic acid — the same weak acid found in club soda — and releases hydrogen ions, reducing the water’s pH. This chemical change robs the water of carbonate ions, a critical building block for many marine organisms. Clams rely on that carbonate, as do corals, lobsters, shrimp, crabs, barnacles, sand dollars, cucumbers and sea urchins.

In Puget Sound, for example, 30 percent of marine life — some 600 species — draws upon carbonate ions to grow.

Reaction to high CO 2 varies by species. Acidification can kill baby abalone and some crabs, deform squid and weaken brittle stars while making it tough for corals to grow. It can 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 actually do better in high CO 2 . Another quarter seem unaffected. But entire marine systems are built around the remaining half of susceptible plants and animals.

“What does well in disturbed environments are invasive generalists,” said Ken Caldeira, a climate expert at Stanford’s Carnegie Institution for Science, who helped popularize the term ocean acidification. “The ones that do poorly are the more highly evolved specialists. Yes, there will be winners and losers, but the winners will mostly be the weeds.”

Many species, from sea urchins to abalone, have some capacity to adapt to high CO 2 . But it’s not clear if they will have the time.

“It’s almost like an arms race,” said Gretchen Hofmann, a marine biologist at the University 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?”

That is the underlying problem: The pace of change has caught everyone off guard.

Already, the oceans have grown 30 percent more acidic since the dawn of the industrial revolution — 15 percent just 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.

The oceans are corroding faster than they did during past periods of marine extinctions that were linked to souring seas. Even 55 million years ago, the rate of change was 10 times slower than today. The current shift has come so quickly that scientists five years ago saw chemical changes off the West Coast not expected for half a century.

And the seas are souring even faster in some places.

The Arctic and Antarctic have shifted more rapidly than other waters around the world because deep, cold seas absorb more CO 2 . The U.S. West Coast has simply seen consequences sooner because strong winds draw its CO 2 -rich water to the surface where vulnerable shellfish live.

Sea chemistry in the Northwest already is so bad during some windy periods that it kills young oysters in Washington’s Willapa Bay. In less than 40 years, half the West Coast’s surface waters are expected to be that corrosive every day.

That threatens to reduce the variety of life in the sea.

“That loss of biodiversity should matter to people just like a lack of diversity in your stock portfolio should bother people,” said Jeremy Mathis, an oceanographer with the National Oceanic and Atmospheric Administration. “It works exactly the same way. If you go all-in on one stock and that stock crashes, you’re stuck.”

Katharina Fabricius sees plenty of reason to worry.

In six trips to Papua New Guinea, she found sea cucumbers and urchins living near the vents, but the shrimp and crab she expected to see instead were almost nonexistent. She saw only 60 percent as many hard corals as she did on healthy reefs nearby. Only 8 percent as many soft corals survived, and one species dominated. The reefs that remained were less intricate, offering fewer places for animals to hide. Dull, rounded boulder corals, which seemed to thrive, still grew a third slower than normal. Sea grasses flourished but were less diverse. There was twice as much fleshy algae.

“We’re seeing sea-grass meadows as green as golf lawns,” Fabricius said. “But corals are suffering, and they are incredibly important.”

Corals protect shorelines from erosion and severe weather and provide a dormitory where staggering varieties of life seek shelter. Those tiny plants and animals then become food for other creatures. Study after study shows the same thing — the more reefs collapse and fleshy algae spreads, the less we see of important tropical fish: wrasses, tangs, damselfish, parrotfish.

Those losses come at a price.

One-sixth of animal protein consumed by humans comes from marine fish — in some cultures nearly all of it. The vast majority of wild seafood is fish, and fish account for three-quarters of the money made from ocean catches.

Yet reefs are just the first of many ways ocean-chemistry shifts could hit seafood.

Scientists once thought fish would dodge the worst direct effects of acidification. Now it appears that might be wrong — a fact researchers learned almost by accident.

Losing Nemo: Fish harmed, with deadly results

In 2007, American biologist Danielle Dixson arrived in Papua New Guinea hoping to find out how Nemo got home.

Clownfish live in waggling anemones near coral reefs, often near islands. Scientists suspected they traced their way through the sea by following their noses. But how?

Solving this riddle would help uncover one of acidification’s most haunting problems: its ability to scramble fish behavior.

Dixson, then a graduate student at Australia’s James Cook University, wanted to find the olfactory cue that drew clownfish back to the reef. She tested smells from different water. She tested dirt. Nothing was quite right, until she looked up.

Since Papua New Guinea’s island rain forests drape over the sea, Dixson took five island plants and spread the scent of their leaves in water. Young clownfish immediately swam toward the smell.

Back in Australia, she prepared to repeat the experiment in a lab. There she bumped into Philip Munday.

Munday, a James Cook University professor, had been trying to see if carbon dioxide hurts fish. He checked everything: weight, survival, reproduction. No obvious problems surfaced, which came as no surprise. Fish are excellent at altering blood chemistry to accommodate changing seas.

But he wanted to do more tests. He asked Dixson if she minded raising some extra clownfish for him.

On a whim they decided: Why not see if CO 2 altered how fish use their noses?

“We thought, ‘let’s just combine the two experiments and see how it goes,’ not expecting that we’d see anything,” Munday said.

CO 2 -rich seas can scramble fish behavior Mark Nowlin / The Seattle Times

Surprises came right away. Exposed to high CO 2 , the fish quit distinguishing between odors and were equally attracted to every scent. Since clownfish use smell to stay safe, the duo then exposed babies in high-CO 2 water to dottybacks and rock cod — bigger fish that eat young clownfish.

Normal clownfish always avoided the danger. The exposed fish lost all fear. They swam straight at predators.

Over the next few years, scientists learned CO 2 changed many reef fishes’ senses and behaviors: sight, hearing, the propensity to turn left or right. Baby reef fish exposed to high CO 2 and placed back in the wild died five times more often. Even when baby reef fish and predators were both exposed to high CO 2 , young fish were bolder, ventured farther from home — and died twice as often.

Only last year did researchers learn why: Elevated CO 2 disrupts brain signaling in a manner common among many fish.

The clownfish story, in other words, was no longer just about clownfish.

By then, another American living in Australia, marine scientist Jodie Rummer, was learning that high CO 2 boosted aerobic capacity for some tropical fish, transforming them into super athletes. Yet even some of these fish showed behavioral problems. Rummer called it “dumb jock syndrome.”

“You might expect that a more athletic fish can be better at chasing food, or be better at getting away from a predator, or finding a mate,” she said. “But if their cognitive function — or their brain — is compromised under these high-CO 2 conditions, they might make bad choices. They might turn the wrong direction and end up right in a predator’s mouth.”

Most of this research had been limited to a select few tropical species. But scientists knew it wouldn’t take much for behavioral problems to impact consumers.

Acidification need only harm the wrong fish.

Big warning for high-stakes fishery

Across the Pacific Ocean from Papua New Guinea, Tom Enlow climbed a set of stairs in Dutch Harbor, Alaska, a thousand miles out in the Aleutian Islands chain. He arrived on the sorting line of a fish-processing plant owned by Redmond-based UniSea.

Behind Enlow, giant vacuum hoses spit thousands of oily walleye pollock onto a conveyor.

Pollock “is the lifeblood of our local economy, certainly, and the state’s economy, and one of the largest industries on the Northwest and West Coast,” said Enlow, the plant’s manager.

The North Pacific pollock catch is so big it sounds almost absurd. Fleets of fishermen and factory trawlers haul in 3 billion pounds annually. No other North American fishery operates on this scale. Seafood companies reel in $1 billion a year from that catch.

Pollock gets carved into frozen fish sticks, sold overseas as roe and imitation crab, or packed in blocks. McDonald’s runs television commercials trumpeting the Bering Sea fishermen who supply pollock for Filet-O-Fish sandwiches.

So pollock was among the first species the U.S. government tested in high-CO 2 water. Results late last year brought no surprise: Acidification would hurt neither the fish’s body nor its growth. Adult and young seemed physically unharmed.

But after tracking clownfish research, government scientists in Oregon tried new tests.

After smelling prey, pollock scout around and hunt it down. So NOAA biologist Thomas Hurst exposed young pollock to high CO 2 and introduced the scent of what they eat. Some of the fish struggled to recognize their food.

“In some of the very early work it looks like pollock may show some of the same kinds of deficits that are seen in coral-reef fishes,” Hurst said.

It’s too soon to say how — or even if — that would affect pollock fishing. Some tropical fish raised in high-CO 2 water gave birth to young that adjusted to their new environment. Pollock might respond the same way.

But the fish also might not. And a lot rides on the outcome, particularly in the Northwest.

Dutch Harbor might as well be a distant Seattle suburb. Washington businesses or residents often own or run its trawlers, crab boats and processors. Employees typically come from the Puget Sound region. Even the former five-term mayor of Unalaska, Dutch Harbor’s municipal government, used to fish out of Ballard.

“We don’t yet know whether it’s going to be a really severe impact or a modest impact,” Hurst said. But “if the fish is less able to recognize the scent of its prey and then therefore locate food when it’s foraging out in the wild, obviously that’s going to have negative impacts for growth and then survival in the long run.”

And that’s just one species. Similar tests are under way for rockfish, cod, several kinds of crab and sharks.

But brain damage is not even the biggest threat to commercial fish.

Key link in food chain dissolving

All over the ocean, usually too small to see, flutter beautiful, nearly see-through creatures called pteropods, also known as sea butterflies. Scientists have known for years that plummeting ocean pH eventually would begin to burn through their shells.

Few people would find that significant save for one fact: Many things eat pteropods.

Birds, fish and mammals, from pollock to whales, feast on this abundant ocean snack. Pteropods make up half the diet of baby pink salmon and get eaten by other fish, such as herring, that then get swallowed by larger animals.

So scientists were alarmed late in 2012 when researchers announced that pteropods in Antarctica were dissolving right now in waters less corrosive than those often found off Washington and Oregon. What did that mean for the Northwest?

The United States does so little monitoring of marine systems that we know almost nothing about the health of creatures that form the bottom of the ocean food chain — things like pteropods, krill or other important zooplankton called copepods. The most-studied animals remain those we catch. Little is known about the things they eat.

Replay a live chat Reporter Craig Welch, along with NOAA oceanographers Jeremy Mathis and Richard Feely, answer reader questions. See chat replay →

Computer modelers such as Isaac Kaplan, at NOAA in Seattle, are scrambling to figure out how sea-chemistry changes could reverberate through the ocean.

Initial results are disturbing.

“Right now, for acidification in particular,” Kaplan said, “the risks look pretty substantial.”

Kaplan tracks the Pacific coast — temperature, pH levels, currents, salinity. He incorporates studies that detail how CO 2 impacts creatures. Then he extrapolates how all those variables are likely to affect the fish people catch.

While the models are rough and uncertainty is high — too many elements cannot be controlled — the trend is clear.

Kaplan’s early work predicts significant declines in sharks, skates and rays, some types of flounder and sole, and Pacific whiting, also known as hake, the most frequently caught commercial fish off the coast of Washington, Oregon and California.

“Some species will go up, some species will go down,” said Phil Levin, ecosystems leader for NOAA’s Northwest Fisheries Science Center in Seattle. “On balance, it looks to us like most of the commercially caught fish species will go down.”

Fearing ‘a mess for this little town’

The findings confound those who rely on commercial fish.

Capt. Ben Downs stood atop the wheelhouse of the F/V Pacific Dove, in Westport, Grays Harbor County, on a recent summer day as he rolled on a fresh coat of whitewash. Downs spent years piloting one of the coast’s biggest whiting boats. This day he was prepping for shrimp fishing.

“The early warnings are there. We’ve seen the first wave that hit the oysters. We’re just hoping it doesn’t come our way.” Dave Fraser Who runs a hake fishing cooperative

“The ocean is always changing,” Downs said. Nearby a ship offloaded whiting at the city’s largest processor. “This is nothing different. I’ve battled the ocean all my life.”

Yet even a skeptic like Downs sees the stakes.

Coastwide, fishermen bring in tens of million pounds of whiting a year. It’s the biggest product at Westport’s fish plant, which at times employs a quarter of the city’s workforce.

“If the hake went away, it’d be a mess for this little town,” he said. “Astoria, Oregon, same thing. Newport, Oregon, same thing.”

Dave Fraser, who runs a whiting fishing cooperative, wasn’t skeptical, but weary. Fishermen already face tangible crises daily: the dollar’s value swinging wildly against the yen; quotas falling based on routine marine shifts.

“Being able to focus on something 10 or 20 years away … it’s hard,” he said. “The early warnings are there. We’ve seen the first wave that hit the oysters. We’re just hoping it doesn’t come our way.”

It is a problem not limited to fishing fleets.

“If you go 100 miles from the coast, most people say, ‘Why do I care about ocean acidification?’ ” Mathis, at NOAA, said. “Convincing a farmer in Iowa or a teacher in Kansas to care about ocean acidification is our challenge.”

He measures progress by the drop in emails from angry Alaskans challenging his findings.

“Acidification is very real: There isn’t any doubt it’s happening,” said Clem Tillion, a former Republican Alaska state Senate president, even though he still denies human contributions to global warming. “It’s obvious. And it’s going to be devastating.”

At stake: food for rural people

On a warm Papua New Guinea night, a quarter-mile from Fabricius’ CO 2 vents, Edwin Morioga and Ridley Guma sat in the dark in a canoe and prepped their spears.

The rain-forest jungles of Milne Bay are home to wallabies, flying rodents, cockatoos and butterflies the size of dinner plates. Villagers raise taro, yams and other vegetables. Many know increasing storms and rising seas someday will force them to move their sago tree huts to higher ground.

But with a quarter of a million people spread across 600 islands, the threat to food may be more significant.

Most of their protein comes from the sea. Fishermen unspool hand lines to collect sweetlips and sea perch. They gather shrimp and crustaceans. And at night they dodge tiger sharks and saltwater crocodiles to spear small fish from beneath bountiful corals.

Globally, the sea provides the primary source of animal protein for a billion people. Many, like Morioga and Guma, have few alternatives.

The pair slipped into the water and floated face down, flashlights trained on the reef. Neither knew much about Fabricius’ acidification research. But they agreed they did not want CO 2 from the West or an industrializing Asia transforming their reefs into places resembling the desolate nearby bubble sites.

Away from the vents, amid the coral, life of all kinds is still plentiful.

In an instant, Morioga saw a flash. He took a breath and dived, stabbing beneath a branching coral. After a pause, Morioga surfaced.

On the end of his spear writhed a tiny rabbitfish, his first catch of the night from what remains one of the world’s healthiest reefs.

At least for now.