by Andy O’Brien
Free Press news story
In the coming weeks, the Maine Legislature will consider several bond proposals, including a bipartisan measure aimed at tackling the monumental problem of ocean acidification (OA) in the Gulf of Maine. LD 998, sponsored by Rep. Wayne Parry (R-Arundel) and Rep. Mick Devin (D-Newcastle), would ask voters to approve a bond to borrow $3 million to be used to collect data, monitor waterways and test ocean acidity along the Maine coast and study its impact on wildlife and commercial shellfish species.
“Maine faces a tremendous, fast-evolving environmental challenge,” said Sebastian Belle, executive director of the Maine Aquaculture Association, in testimony last June. “The implications of ocean acidification are only beginning to be understood, but one thing is clear, unless we have the tools to accurately monitor ocean acidification trends, we will be unable to react in terms of management and policy decisions.”
While there is still a lot scientists don’t know regarding the effects of ocean acidification, there is virtual consensus among scientists that about a quarter of the carbon dioxide emitted from fossil fuels and deforestation gets sequestered in the oceans, says University of New Hampshire OA expert Joe Salisbury. As the C02 gets absorbed into the ocean it reacts with seawater to form corrosive carbonic acid, which reduces the alkalinity of the water and inhibits the formation of the molecule calcium carbonate. Valuable commercial shellfish species like clams, lobsters, mussels, shrimp, scallops, oysters and sea urchins use calcium carbonate as the building blocks to form their shells. With fewer calcium carbonate molecules, they have to spend more energy for shell production, which hinders their ability to grow. If the water gets too acidic, it can even dissolve shells.
“There is no argument about this. This is really simple high school chemistry,” said Salisbury at the Fishermen’s Forum on March 5.
Under ordinary circumstances, the ocean can naturally buffer excess C02. But ever since the Industrial Revolution, humans have emitted so much carbon dioxide into the air and water that chemical changes are happening much faster than at any time during the past 200,000 years. As a result, many scientists believe that ocean life may not be able to adapt to it fast enough. According to scientificic measurements, ocean acidity has already increased by 30 percent since the Industrial Revolution.
Salisbury noted that the Gulf of Maine is particularly susceptible to acidification because it receives so much fresh water from the region’s many large rivers, as well as cold, fresh water from the Gulf of St. Lawrence, and snow and ice melt from the Arctic via the Labrador Current. The region’s complex flow of water compounds the acidifying effect because carbon dioxide is more soluble in cold water and fresh water has lower concentrations of carbonate and calcium ions. In other words, we send Canada polluted air and they send us back acidified water, said Salisbury.
Salisbury said that if the pH level, which is a measure of acidity ranging from 0-14, goes below 1.6, it can have a very detrimental effect on shellfish. He said that pH levels fluctuate, but it’s about 2 to 2.2 in the Gulf of Maine right now. Salisbury said that future carbon releases will likely cause carbonate ion concentrations to go down even further based on projections by the Intergovernmental Panel on Climate Change.
“Ocean acidification from atmospheric increases in C02 is real. It’s not debatable,” Salisbury continued. “In some areas it’s happening faster than others. This coastal variability from a variety of sources really puts a lot of organisms at or in threshold conditions, even now as we speak. The northwestern Atlantic, where we live, is particularly sensitive to OA, and it could change really quickly based on water mass changes and we really need to know a lot more.”
Bill Mook, who owns Mook Sea Farm in Walpole, told forum participants that the carbonate chemistry in the sea water has been a problem for his business, but he has been able to mitigate it by buffering the water. He noted that 30 years ago the salinity of the water was about 30 parts per million (ppm), but it has dropped in recent years. At the same time, he said, the average concentration of carbon dioxide has increased by about 36 ppm.
“Hatcheries are definitely the canaries in the coal mine,” said Mook. “The window of conditions that are going to be sufficient for natural bivalve larvae is going to continue to close and you’re going to see less predictable recruitment. And that’s what you’re seeing in a lot of places.”
Dan Small, who studies lobsters at St. Francis Xavier University in Nova Scotia, noted that there has been very little research done on the effects of ocean acidification on lobsters, which he said is because earlier studies showed they are relatively tolerant to changes in the carbon chemistry of the oceans. As a result, marine researchers have focused more energy on sensitive species like oysters. However, Small said that increased levels of C02 are impacting the internal chemistry of lobsters by lowering the pH in their blood.
“Lobsters, other crustaceans and all shellfish species need to keep pH at a constant level in order for them to maintain function, in order for them to go about their daily lives without any hassle,” said Small.
He said that while lobsters are able to regulate their internal pH better than other sea animals like echinoderms (star fish, sea urchins and sea cucumbers) and bivalves (clams, oysters, mussels and scallops), the process also requires them to use energy that they would otherwise use to build their shells and reproduce. He said while much more research needs to be done on lobsters, he noted that studies on crabs in the UK have indicated that increased levels of ocean acidity can decrease their feeding rates because they have less energy to hunt for food. Small also pointed to a 2014 study published in the Journal of Shellfish by researchers at the Sven Lovén Centre for Marine Sciences in Kristineberg, Sweden, which found that not only did OA increase the mortality of northern shrimp, but it also negatively affected their taste.
“The shrimps cultured in conditions representative of the present ocean were preferred three times more than shrimps exposed to ‘future ocean’ conditions for three weeks,” the researchers reported.
Meanwhile, Mook said that he hopes Maine policy makers will be able to take a proactive approach to the problem and look at how OA impacts the entire Gulf of Maine ecosystem rather than just individual species.
“We need to demand that the government spends more money in establishing monitoring systems and doing the thoughtful, correct research that’s going to provide businesses like mine with enough information so that we can do a little more planning and come up with strategies to cope with all of this,” said Mook. “We can’t avert crises if we don’t know about them and information is really key to our survival.”
