CO2-caused acidification causing rapid, major changes

ClimateWire, 23 April 2010 - When oyster larvae began dying in record numbers at Pacific Northwest hatcheries in 2008, shellfish farmers weren't sure what was happening.

Growers quickly realized that a bacterium, Vibrio tubiashii , played a role. They worked with scientists to design new filtration systems to keep the bacteria out of the ocean water that feeds the tanks where oyster larvae grow to seed. But that didn't solve the problem.

"That's when we folks turned to pH and realized that the Vibrio was secondary to that," said Bill Dewey of Taylor Shellfish Farms, a family-run business that has farmed shellfish in the Pacific Northwest for more than 100 years.

The ocean water growers were pumping into their tanks was more acidic than normal -- so acidic that it was dissolving the shells of the oyster larvae faster than the larvae could grow them.

Taylor Shellfish Farms and other Pacific Northwest shellfish growers believe theirs is one of the first fisheries affected by ocean acidification -- a phenomenon caused by the same carbon dioxide emissions that drive climate change. Scientists say it could reshape life in the world's seas, from the tiny plankton at the base of the food web on up to fish and shellfish species that show up on dinner plates.

"The chemistry of the ocean is changing at an unprecedented rate and magnitude due to anthropogenic carbon dioxide emissions," warned a report released yesterday by the National Academy of Sciences. "The rate of change exceeds any known to have occurred for at least the past hundreds of thousands of years."

30 percent more acidic than at the dawn of industrial age

Having absorbed one-third of the CO2 produced by human activities over the last two centuries, oceans are now 30 percent more acidic than they were at the start of the Industrial Revolution. By the end of the century, if CO2 emissions continue on the current trajectory, the world's oceans could become 150 percent more acidic.

In the Pacific Northwest, acidification is intensified by seasonal upwelling, a natural ocean circulation pattern that pulls water from the deep ocean onto the continental shelf each spring.

A 2008 study led by Richard Feely, a scientist at the National Oceanic and Atmospheric Administration's Seattle lab, found evidence that waters off the Pacific coasts of Canada, the United States and Mexico have reached levels of acidity scientists had predicted wouldn't occur until 2050.

The researchers found that water stirred up by the annual upwelling is now rich in carbon dioxide -- absorbed by the oceans about 50 years ago, when CO2 emissions were much lower -- that gradually made its way down to water about 150 meters below the ocean surface.

"What's most troubling to me is that the water that's coming up in these upwelling events is 50 years old," said Taylor Shellfish Farms' Dewey. "Even if we stop our CO2 emissions today, we still have 50 years of hurt coming before it starts to get better."

Sixty percent of the oyster larvae at the Taylor hatchery on Dabob Bay in Quilcene, Wash., died in 2008. Eighty percent died last year. The company is coping, in part, by moving more of its oyster operations to its facility in Kona, Hawaii.

"We've been expanding that facility as rapidly as we can to take on additional oyster larvae production," Dewey said. "We produce seed for our company but also sell seed to oyster farmers up and down the West Coast and all over the world. When we have that kind of production problem, that affects other growers, as well."

Acclimate or go extinct

James Barry, a marine biologist at the Monterey Bay Aquarium Research Institute who helped write the National Academy of Sciences report, said marine species faced with more acidic waters have limited options: Begin to acclimate, which in the course of a few generations may produce genetic adaptations, or go extinct.

But experts say it's still hard to predict how ocean acidification might transform marine ecosystems.

A 2008 study by J. Timothy Wootton at the University of Chicago documented changes in mussel beds off Tatoosh Island, Wash., that scientists linked to a drop in pH. As water there became more acidic, the number of mussels and stalk barnacles dropped. But other organisms thrived, including including smaller acorn barnacles that also build calcium carbonate shells.

And at Taylor Shellfish Farms, some species have proved to be more adaptable than others.

"We're not seeing it with clams," Dewey said. "We're able to buffer the seawater in the hatchery water to allow us to grow clams and mussels. But that does not work for oysters. Something else is going on where the ocean chemistry is keeping the ocean larvae from surviving."

On a global scale, Barry said a major cause for concern is recent research that suggests the world's coral reefs, which support fisheries and tourism, "are in real trouble" due to a combination of changing ocean chemistry and other environmental problems, like destructive fishing practices.

"The changes we expect to occur by the end of this century will be the largest and most rapid ocean chemistry shift in hundreds of thousands of years," he said.

Looking for a research strategy

The issue hasn't escaped lawmakers' attention. A law enacted last year directs the federal government to create a wide-ranging strategy to monitor, analyze and predict the course of ocean acidification.

The National Academy of Sciences study released yesterday aims to help federal agencies understand where research is needed. It recommends, among other things, modifying the U.S. ocean observing network to measure different factors related to ocean acidification and monitoring marine life to understand how biological systems will respond to changes in ocean chemistry.

Such research is urgently needed, the report noted: "Despite the potential for socioeconomic impacts to occur in coral reef systems, aquaculture, fisheries and other sectors, there is not currently enough information to assess these impacts, much less develop plans to mitigate or adapt to them."

At a Senate hearing yesterday, a commercial fisherman who trawls the waters of the Gulf of Mexico made a more emotional plea for government action.

Donald Waters, who described himself as a fisherman "for the better part of four decades," said ocean acidification hasn't affected his business catching red snapper and king mackerel out of his home port in Pensacola, Fla. But he said he fears what the future may bring.

"To me, this is just devastating," he said. "It's something you can't imagine -- if you lost the jobs, the men, the boats -- if our oceans turned more or less poison."

Dewey, the Taylor Shellfish Farms spokesman, is also looking to the future.

"The one thing that's daunting about this particular issue is that to resolve what's causing it -- it's massive," he said. "It's convincing the world that they need to stop emitting so much CO2. And so that is what makes it different than a lot of the problems we face ... [but] we're still optimistic that science can help us adapt our hatchery processes."

Author Lauren Morello Publication Date 23 Apr 2010 Document Type News articles Issue/Topic Ecosystems Energy & Climate Source ClimateWire Include In RSS Business & Sustainable Development News Energy & Climate News