Oregon scientists unlock new clues about how acid oceans kill shellfish, opening doors to potential solutions

Photo by the Associated Press

Photo by the Associated Press

Could the solution to ocean acidification and its deadly effects on shellfish lie in a bottle of Tums? New research from Oregon State University scientists suggests it could.

According to a study published in the journal Nature Climate Change, the real cause of the phenomenon that’s killing oysters, mussels and other shellfish up and down the Pacific coast isn’t heightened carbon dioxide and ocean pH levels alone, as previously thought.

Rather, human-caused carbon dioxide pollution plays a role in a more complex equation. The water’s overall saturation state – a term used to describe its corrosiveness to larval bivalve shells – ultimately determines whether the larvae are able to create a shell.

They have 48 hours to do so after hatching, or else they die. They can’t eat without a shell, so if the process is delayed the larva starves.

Calcium carbonate, a chemical in bivalve shells, plays a key role. George Waldbusser, an Oregon State University ecologist and biochemist who led the study, said typically “the oceans are supersaturated with it.” That makes shell-building easy.

But carbon dioxide neutralizes carbonate ions, so when it enters the ocean, a concurrent influx of carbonate ions is needed to offset the effect. As long as this balance remains intact, shellfish larvae can tolerate carbon dioxide levels 10 times higher than currently found in the ocean, the scientists found.

In the past, that has happened naturally. For instance, tectonic shifts in the earth’s crust have created volcanoes that increase oceanic carbon dioxide levels. That seismic activity also shook the earth, weathering rock surfaces and loosening carbonate that eventually landed in the ocean.

Human-generated carbon, however, is upsetting the balance, the OSU team found.

Waldbusser said his team’s discovery could lead to “a major shift in perspective” among scientists working to reverse ocean acidification.

This is where the Tums come in.

Calcium carbonate is the main ingredient in the heartburn-soothing pills. In theory, the ocean’s balance could be re-established by infusing the water with carbonate – something that’s already being done in some commercial shellfish hatcheries.

But achieving similar results on a global scale is trickier, Waldbusser said. For starters, mining for limestone – a rock rich in calcium carbonate – would create new environmental impacts. Plus, limestone sprinkled into the ocean wouldn’t dissolve until the water was already undersaturated.

At that point, he said, “It’s already too late for the bivalve larvae.”

Kelly House, The Oregonian, 15 december 2014. Article.

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