Ocean acidification may pose bigger threat to marine life than warming

Ocean acidification has long been considered “the other carbon problem”, taking a back seat to discussions about global warming.

In reality, scientists are beginning to see signs indicating that ocean acidification is a serious and immediate threat.

The Gulf of Maine, for example, is exhibiting signs of acidification, both real and speculative. Mark Green, professor at St. Joseph’s College studies the effects of acidic muds on survival of juvenile shellfish. Green studies clams in Casco Bay and points out that ”a huge amount of these juvenile clams are dissolving when they hit the sediment.” Clams from this area were once thought to be disappearing due to predators. Green’s research points to acidification as the main culprit.

These clams, and other organisms with hard shells made of calcium carbonate, are dissolving because of increased acidity. The ocean acts like a sponge to absorb about 25% of the carbon dioxide in our atmosphere. It is carbon dioxide, that when introduced into water forms an acid that reduces a buffering compound called carbonate. Carbonate is an essential compound that these organisms use to form protective shells. When these organisms can’t make a proper shell it is left vulnerable to predators, diseases and other stressors.

Other researchers in the Gulf of Maine are studying the impacts of acidification on the hardening of lobster shells and even the growth of tiny, calcium carbonate covered phytoplankton that are the base of the food chain. William Balch of Bigelow Laboratory in Boothbay Harbor has seen a reduction in these types of phytoplankton in the Gulf of Maine and in locations like the Patagonian shelf off of Argentina. While these drops in abundance are only speculated to be the result of acidification, Balch points out that is important to have a baseline to study the effects of an acidified ocean on plankton. ”That’s the bottom of the marine food web, on which all life in the ocean depends.”

For decades, many people assumed any excess carbon dioxide would be absorbed by the ocean with no change to the acidity of the ocean. ”But it turns out, if you produce the quantities of carbon dioxide that we’ve been producing, the buffering effect is not there,” he said. ”When all is said and done, I think it might be the more significant problem.”

– Tara Duffy, Blue Ocean Institute Graduate Intern, Stony Brook University

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