Pacific Swell

Southern California environment news and trends

Increasingly acidic ocean dissolving key marine snails along West Coast

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Federal scientists say an increasingly acidic ocean is dissolving tiny snails key to the marine food web along the West Coast.

Their research, published in the Proceedings of the Royal Society B, is the first evidence that shows how changing ocean chemistry is harming pteropods, which are delicate, free-swimming marine snails known to feed salmon and other fish.

Ocean chemistry is changing because of greenhouse gases. Sea water absorbs about a third of the planet’s atmospheric carbon, changing the pH of the water.

But Richard Feely, a scientist for the National Oceanographic and Atmospheric Administration and co-author on the paper, says greenhouse gases are only part of the reason the West Coast is especially vulnerable to this ocean acidification.

The other problem is the way deep Pacific water — heavy in carbonic acid — moves up over the edge of the continent.

“Along our coast we have a natural upwelling process,” he said. “That pulls water from deeper depths all the way to the beach and then it goes outward from the surface at the beach.”

Very few studies have looked at what more corrosive water does to marine animals by sampling them in the Pacific Ocean itself. So NOAA’s Marine Environmental Lab took a closer look at pteropods at sites between Washington State and Mexico.

Lead author Nina Bednarsek says she observed how coastal waters break down and eat away at the snails’ smooth shells.  

“Once you have dissolution on the shell, you have exposed crystals,” she said. But the microscopic crystal rods, once exposed, keep breaking down, “and then instead of long rods, you have these cauliflower-like crystals,” she added. 

Tiny pteropods with roughed up shells are now twice as common as a couple hundred years ago. The NOAA team says an acidic ocean could help triple that by the year 2050 – faster than expected. They don’t know how that might send ripple effects up the food chain.

NOAA is still puzzling out how an acidic ocean affects fish, oysters, and other shellfish. But they say with projections of a more and more corrosive ocean, those impacts are only likely to get bigger.

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