Ocean acidification is posing a threat to marine life
NORMANBY ISLAND, Papua New Guinea — Katharina Fabricius plunged from a dive boat into the Pacific Ocean of tomorrow.
A bleak portrait emerged: Instead of tiered jungles of branching, leafy corals, Fabricius saw mud, stubby spires and squat boulder corals. Snails and clams were mostly gone, as were worms, colorful sea squirts and ornate feather stars.
Instead of a brilliant coral reef like the one living a few hundred yards away, what the Australian Institute of Marine Sciences ecologist found resembled a slimy lake bottom. The cause: carbon dioxide.
In this volcanic region, pure CO2 escapes naturally through cracks in the ocean floor, altering the water’s chemistry the same way rising CO2 from cars and power plants is changing the marine world.
As a result, this isolated bay offers a chilling view of the future of the seas under ocean acidification.
As the burning of coal, oil and natural gas belches carbon dioxide into the air, a quarter of it gets absorbed by the seas, changing ocean chemistry faster than at any time in human history.
To understand how that 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 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.
New science shows ocean acidification also can bedevil fish and the animals that eat them, from sharks to whales and seabirds. Shifting sea chemistry can cripple the reefs where fish live, rewire fish brains and attack what fish eat.
Those changes pose risks for food supplies, from the fillets used in McDonald’s fish sandwiches to the crab legs sold at seafood markets. Both are brought to the world by a Northwest fishing industry that nets half the nation’s catch.
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 underway, particularly along the West Coast, before today’s preschoolers reach middle age.
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.
The country isn’t doing much about it. 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.
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.
Many species, from sea urchins to abalone, do show some capacity to adapt to high CO2. But they may not have time.
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.
Meanwhile, the Arctic and Antarctic are shifting even more rapidly because deep, cold seas absorb more CO2. The West Coast has seen consequences sooner because strong winds draw its CO2-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, scientists predict, half the West Coast’s surface waters will be that corrosive every day.
These chemical changes threaten to reduce the variety of life in the sea.
In six trips to Papua New Guinea, Fabricius was surprised to see sea cucumbers and urchins living near the carbon-dioxide vents, but shrimp and crab were almost nonexistent. She saw fewer hard corals than on healthy reefs nearby, and only 8 percent as many soft corals. Reefs were less intricate, offering fewer places for animals to hide. Sea grasses flourished but were less diverse. There was twice as much fleshy algae.
Corals, she said “are suffering, and they are incredibly important.”
And study after study shows the same thing — the more reefs collapse and fleshy algae spreads, the more fish simply disappear. That loss comes at a price.
One-sixth of animal protein consumed by humans comes from marine fish — in some cultures nearly all of it. Fish also account for three-quarters of the money made from ocean catches.
Yet reefs are just one way shifting ocean chemistry can harm fish.
In 2007, American biologist Danielle Dixson, then a graduate student at Australia’s James Cook University, was studying the important ways clownfish use their noses to navigate the ocean. Then she bumped into James Cook professor Philip Munday.
Munday had been trying to see if carbon dioxide hurt fish. The pair decided, on a whim, to see if CO2 altered how fish use their noses. Their findings were a shock.
Exposed to high CO2, the fish lost their ability to distinguish among odors. Since clownfish use smell to stay safe, the scientists then exposed baby fish in high-CO2 water to 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 CO2 changed many reef fishes’ senses and behaviors: their sight, hearing, the propensity to turn left or right. Most important, that caused them to die two to five times more often.
Last year, researchers figured out why. Elevated CO2 disrupts brain signaling in a manner common among many fish. The clownfish story, in other words, was no longer just about clownfish.
So scientists have been testing the most important fish in America: pollock. Fishermen in Alaska catch roughly 3 billion pounds of pollock valued commercially at $1 billion a year in the North Pacific.
After tracking clownfish research, government scientists in Oregon exposed young pollock to high CO2 and introduced the scent of what they eat. The fish struggled to recognize their food.
It’s too soon to say how that might affect pollock fishing. Some tropical fish raised in high-CO2 water gave birth to young that adjusted to their new environment. Pollock might respond the same way. But the fish also might not.
“We don’t yet know whether it’s going to be a really severe impact or a modest impact,” said NOAA biologist Thomas Hurst. 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 brain damage is not even the biggest threat to commercial fish.
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 later this century would begin to burn through their shells.
But they were alarmed late in 2012 when researchers announced pteropods in Antarctica were dissolving already in waters less corrosive than those often found off Washington and Oregon.
That matters because 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. And so little ocean monitoring is done of creatures at the bottom of the marine food chain, there’s no telling yet if other plankton species are experiencing changes, too.
So, to understand the future of the marine food web, government computer modelers have been studying how sea-chemistry changes could reverberate through the ocean. Their initial results, looking at just the U.S. West Coast, are disturbing.
NOAA Researcher Isaac Kaplan’s early work projects potentially significant declines in sharks, skates and rays, some types of flounder, rockfish and sole, and Pacific whiting, also known as hake, the most frequently caught commercial fish off the West Coast.
Such changes could hit the West Coast economy hard. But in other parts of the world, the stakes are even higher.
On a warm Papua New Guinea night, a quarter-mile from the carbon-dioxide vents, Edwin Morioga and Ridley Guma sat in the dark in a canoe and prepped spears.
Villagers here 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.
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. Amid the coral away from the carbon-dioxide vents, marine life is still plentiful.
In an instant, Morioga saw a flash. He took a breath and dived, stabbing a rabbitfish — his first catch of the night from what remains one of the world’s healthiest reefs.
At least for now.