Rising acidity poses peril to many varieties of sea life

`Profound' effect feared from industrial carbon dioxide emissions

August 03, 2006|By USHA LEE MCFARLING | USHA LEE MCFARLING,LOS ANGELES TIMES

THE MARINE SNAILS SHE WAS STUDYING — 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 winglike 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 liter jars of sea water were a microcosm of change occurring invisibly throughout the world's seas.

As industrial activity pumps huge amounts of carbon dioxide into the environment, more of the gas is being absorbed by the oceans. As a result, sea water is becoming more acidic, and a variety of sea creatures could be facing the same fate as Fabry's pteropods.

The greenhouse gas, best known for accumulating in the atmosphere and heating up the planet, is entering the ocean at a rate of nearly 1 million tons an 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 1/2 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 sea water for millions of years.

Less likely to be harmed are algae, sea grasses and other primitive forms of life that are 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 caused such damage to the pteropods aboard the Discoverer.

Some marine biologists predict that altered acid levels will disrupt fisheries by eroding 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 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 carbon dioxide and preventing catastrophic overheating of the planet.

If not for the oceans, the Earth would have warmed by 2 degrees instead of 1 degree over the past century, scientists say.

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. After their inhabitants die, the empty shells rain down on the seafloor. (The white cliffs of Dover in England are composed of untold numbers of these planktonic creatures.)

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 carbon dioxide 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 carbon dioxide mixes with sea water, it creates carbonic acid, the weak acid in carbonated drinks.

Increased acidity reduces the abundance of chemical forms of 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.

Scientists say the acidification of the oceans won't be arrested unless carbon dioxide emissions from factories, power plants and automobiles are substantially reduced. Even now, the problem might 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."

Usha Lee McFarling writes for the Los Angeles Times.

For the full-length article and the first four parts of the series, go to baltimoresun.com/oceans.

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