World's seas bear brunt of industrial emissions

Last of three parts

As she stared down into a wide-mouthed plastic jar aboard the R/V Discoverer, Victoria Fabry peered into the future.

The marine snails she was studying — graceful creatures with wing-like feet that help them glide through the water — had started to dissolve.

Fabry was taken aback. The button-sized snails, called pteropods, are hardy animals that swirl in dense patches in some of the world's coldest seas. In 20 years of studying the snails, a vital ingredient in the polar food supply, the marine biologist from California State University, San Marcos, had never seen such damage.

In a brief experiment aboard the federal research vessel plowing through rough Alaskan seas, the pteropods were sealed in jars. The carbon dioxide they exhaled made the water inside more acidic. Though slight, this change in water chemistry ravaged the snails' translucent shells. After 36 hours, they were pitted and covered with white spots.

The one-liter jars of seawater were a microcosm of change now occurring invisibly throughout the world's vast, open seas.

As industrial activity pumps massive amounts of carbon dioxide into the environment, more of the gas is being absorbed by the oceans. As a result, seawater is becoming more acidic, and a variety of sea creatures await the same dismal fate as Fabry's pteropods.

The greenhouse gas, best known for accumulating in the atmosphere and heating the planet, is entering the ocean at a rate of nearly 1 million tons per hour — 10 times the natural rate.

Scientists report that the seas are more acidic today than they have been in at least 650,000 years. At the current rate of increase, ocean acidity is expected, by the end of this century, to be 2 ½ times what it was before the Industrial Revolution began 200 years ago. Such a change would devastate many species of fish and other animals that have thrived in chemically stable seawater for millions of years.

Less likely to be harmed are algae, sea grasses and other primitive forms of life that are already proliferating at the expense of fish, marine mammals and corals.

In a matter of decades, the world's remaining coral reefs could be too brittle to withstand pounding waves. Shells could become too fragile to protect their occupants. By the end of the century, much of the polar ocean is expected to be as acidified as the water that wrought such damage on the pteropods aboard the Discoverer.

Some marine biologists predict that altered acid levels will disrupt fisheries by melting away the bottom rungs of the food chain — tiny planktonic plants and animals that provide the basic nutrition for all living things in the sea.

Fabry, who recently testified on the issue before the U.S. Senate, told policymakers that the impact on marine life could be "direct and profound."

"The potential is there to have a devastating impact," Fabry said, "for the oceans to be very, very different in the near future than they are today."

The oceans have been a natural sponge for carbon dioxide for eons. Especially after calamities such as asteroid strikes, they have acted as a global safety valve, soaking up excess CO2 and preventing catastrophic overheating of the planet.

If not for the oceans, the Earth would have warmed by 2 degrees instead of 1 over the past century, scientists say. Glaciers would be disappearing faster than they are, droughts would be more widespread, and rising sea levels would be more pronounced.

When carbon dioxide is added to the ocean gradually, it does little harm. Some of it is taken up during photosynthesis by microscopic plants called phytoplankton. Some of it is used by microorganisms to build shells.

Today, however, the addition of carbon dioxide to the seas is anything but gradual.

Scientists estimate that nearly 500 billion tons of the gas have been absorbed by the oceans since 1800. That is more than a fourth of all the CO2 that humanity has emitted into the atmosphere since the start of the Industrial Revolution. Eventually, 80 percent of all human-generated carbon dioxide is expected to find its way into the sea.

When CO2 mixes with seawater, it creates carbonic acid, the weak acid in carbonated drinks.

Increased acidity reduces the abundance of chemical forms of a mineral called calcium carbonate, which corals and other sea animals need to build shells and skeletons. It also slows the growth of the animals within those shells.

Even slightly acidified seawater is toxic to the eggs and larvae of some fish species. In others, including amberjack and halibut, it can cause heart attacks, experiments show. Acidified waters also tend to asphyxiate animals that require a lot of oxygen, such as fast-swimming squid.

The pH scale, a measure of how acidic or alkaline a substance is, ranges from 1 to 14, with 7 being neutral. The lower the pH, the greater the acidity. Each number represents a tenfold change in acidity or alkalinity.

For more than a decade, teams led by Richard Feely, a chemical oceanographer at the National Oceanic and Atmospheric Administration's Pacific Marine Environmental Laboratory in Seattle, have traveled from Antarctica to the Aleutian Islands, taking tens of thousands of water samples to gauge how the ocean's acidity is changing.

By comparing these measurements to past levels of carbon dioxide preserved in ice cores, the researchers determined that the average pH of the ocean surface has declined since the beginning of the Industrial Revolution by 0.1 units, from 8.16 to 8.05.

Geological records show that such a change has not occurred in 650,000 years, Feely said.

In April, Feely returned from a cruise to the North Pacific, where he took pH measurements at locations the team first sampled in 1991. This time, Feely's group found that the average pH in surface waters had dropped an additional 0.025 units in 15 years — a relatively large change for such a short time.

The measurements confirm those taken in the 1990s and indicate that forecasts of increased acidity are on target, Feely said.

If CO2 emissions continue at their current pace, the pH of the ocean is expected to dip to 7.9 or lower by the end of the century — a 150 percent change.

The last time ocean chemistry underwent such a radical change "was when the dinosaurs went extinct," said Ken Caldeira, an expert on ocean chemistry and carbon dioxide at the Carnegie Institution's department of global ecology.

Until recently, the ocean was seen as a potential reservoir for greenhouse gases. Scientists explored the possibility that carbon dioxide could be trapped in smokestacks, compressed into a gooey liquid and piped directly into the deep sea.

Then the results of Jim Barry's experiments started trickling in.

A biologist at the Monterey Bay Aquarium Research Institute in Monterey, Calif., Barry wanted to know what would happen to sea creatures in the vicinity of a large dose of carbon dioxide.

He anchored a set of small plastic rings onto the seafloor to create an enclosure and sent a robot down to squirt liquid carbon dioxide into the surrounding water. Then he waited to see what would happen to animals in the enclosures and those that happened to swim through the CO2 cloud.

Sea stars, sea cucumbers and sea urchins died immediately. Eighty percent of animals within three feet of the carbon dioxide died. Animals 15 feet away also perished in large numbers.

"When they were adjacent to the CO2 plume, pretty much, it killed everything," Barry said.

Experiments in Germany, Norway and Japan produced similar results. The evidence persuaded the U.S. Department of Energy to pull the plug after having spent $22 million in the last six years on such research, including Barry's. Instead, the department will study the possibility of storing carbon dioxide in the ground and on decreasing emissions at their source.

Scientists say the acidification of the oceans won't be arrested unless CO2 emissions from factories, power plants and automobiles are substantially reduced. Even now, the problem may be irreversible.

"One thing we know for certain is it's not going to be a good thing for the ocean," Barry said. "We just don't know how bad it will be."