Whether human activity is responsible for the spike in carbon dioxide in the atmosphere or not, one result that must be dealt with is ocean acidification.

That was the consensus of a panel that addressed those attending Clam Day at the Maine Fishermen’s Forum March 3 at the Samoset Resort.

Thursday’s session was moderated by Sherman Hoyt of the University of Maine Cooperative Extension and Sea Grant, and included presentations from Joseph Salisbury of the Ocean Processing Analysis Laboratory of the University of New Hampshire at Durham, N.H.; biologist Mark Green of Saint Joseph’s College in Standish; Bill Mook of Mook Sea Farm in Damariscotta; and Chad Coffin, president of Maine Clammers Association.

Salisbury, who lived in South Portland for most of his life and was a fisherman in his teens and 20s, said he worked in a lab to learn about ocean acidification.

He said increased CO2 in the atmosphere and water led to increased acid in the ocean.

“This is happening quickly within our lifetime,” Salisbury said.

He said while there was controversy about the question of human contributions to climate change, “I’m not here to talk about climate change. There’s no debate that increased fossil fuel in the atmosphere is causing the ocean to become more acidic.”

He said that 7.5 million metric tons of fossil fuel emissions created 1.5 million metric tons of carbon in the atmosphere each year.

“About half of that stays in the atmosphere,” Salisbury said. “A quarter to a third gets taken back up by the land surface in biomass such as trees and plants. Another quarter or so ends up in the ocean.”

Using slides and a video clip, Salisbury showed the audience in the Penobscot Bay Room of the Samoset Resort how measures of atmospheric CO2 made since the 1950s in Hawaii and 1970s at the South Pole showed a steady increase in the southern hemisphere and a more variable pattern in the north that began to accelerate about 30 years ago.

“There is an unmistakable trend that this is going up,” he said. “This is not since the ice age or the dinosaurs. This is since 1980.”

He said CO2 had increased and the pH level had decreased at the same time. In chemistry, pH is a measure of the acidity or basicity of a solution that is solvent in water. The lower the pH number, the more acidic a liquid is, with pure water at room temperature considered neutral at a pH of around 7.0.

“There’s a really good correlation between the two,” said Salisbury. He said during his 55-year lifetime the pH level of the oceans had dropped 0.125 points.

“It seems small, but if this change occurred in your bloodstream, you’d be suffering from acidosis and you would die,” he said.

Winners and losers appear as carbon dioxide affects shell development

Salisbury said increased CO2 in ocean water led to higher acid levels and was related to a reduction in the amount of carbonate, a buffer for ocean acidity.

“It’s the same thing that’s in Tums or Rolaids,” he said.

The acid neutralizes carbonate, which shellfish need to build exoskeletons. Salisbury said CO2 came from land as well as the atmosphere.

“River water is very acidic,” he said.

He said that clams, periwinkles, bay scallops and algae respond negatively, while blue crab, shrimp and lobster seemed to benefit, growing shells at a faster rate in acid conditions.

“The pH change we’re seeing now is faster than in the past 159 million years,” said Salisbury. “Much faster.”

He said the last time a similar spike was seen was 60 million years ago, when 90 percent of species using carbonate for shell creation became extinct.

Shells deteriorate in days

Salisbury’s slides showed that softshell clam larvae in water with a pH of 7.5 were unable to build resilient shells.

“If it doesn’t kill [them] it’s a lot of stress,” he said.

A study of mud taken from South Portland flats showed that 50 percent of the mud tested was too acidic for shellfish to grow.

“As pH goes up, mortality goes down,” he said. “It’s 100 percent at 7.3,” he said.

In the course of seven days at that level, 0.2 millimeter larvae showed serious decay, with holes and jagged edges appearing in their shells.

“We’re not talking about hydrochloric acid,” Salisbury said. “We’reĀ putting them in mud.”

He said the only mitigation for CO2 in the atmosphere is to wean society off the use of carbon-based fuels.

Oyster farmer sees problems at hatchery

Bill Mook of Mook Sea Farm said he began to see acid-damaged shells in 2005 at a Virginia calm hatchery.

He described research done by shellfish farmers and harvesters on the West Coast that showed lower pH levels led to acidification that damaged shells.

Longer days with sunshine improved conditions, he said.

Mook said one of the challenges facing his industry was the hazard acidification presented to phytoplankton, the micro-algae that are developing shellfish larvae’s main food. His facility grows its own phytoplankton. Mook said a sudden and serious drop in phytoplankton blooms alerted him to the problem, and that a similar drop at a Virginia clam hatchery indicated that the issue was not a local one.

Mook said the challenge has led him and other hatchery owners to develop scientific protocols for testing that could be useful to scientists seeking the causes of acidification and possible ways to mitigate its damage.

Clammers, environmental advocates join effort to understand acidification

Maine Clammers Association President Chad Coffin offered the services of his members in expanding testing of clamflats. He said 81 municipal regulatory programs in the state have law enforcement personnel who could take samples and send them to centralized laboratories.

He also offered to provide harvest data that might prevent non-productive flats from being seeded.

“Throwing down seed in the wrong place is throwing away money,” said Coffin.

There was some discussion of the potential to mitigate acidification of clamflats by mixing shells back into the sand.

While the proper mix of ground shells could restore some of the lost balance to the flats, the panel agreed that this would need to be done in a consistent and measurable way.

Consistency would also be required if volunteers helped with testing, said Salisbury.

“We need a very accurate measurement,” he said, adding accurate information about pH levels in the mud where clams grow would be very valuable.

Joe Payne of Friends of Casco Bay said his group recently tested a number of instruments and settled on one that costs less than $100 and gave reliable results. He suggested that volunteer monitors work through his organization to develop a protocol for testing the clamflats and calibrate the instruments they would use.

Finally, biologist Mark Green urged interested parties to work together to have an approved plan so state and federal regulators would accept the data they collected.

The discussion about the affects of ocean acidification on Maine’s fisheries is scheduled to continue Saturday, March 5, when Maine Lobstermen’s Association President David Cousins will replace Coffin on the panel.

The Maine Fishermen’s Forum will continue through March 5 at the Samoset Resort. For more information, visit mainefishermensforum.org.

The Herald Gazette Reporter Shlomit Auciello can be reached at 207-236-8511 or by e-mail at sauciello@villagesoup.com.