As CO2 levels increase in the atmosphere, near-shore waters are becoming more acidic, which can hurt the shell strength of marine organisms. The early stages of shell growth are sensitive to increasingly corrosive seawater, reports a new study, and it's causing commercial oyster operations in the Pacific Northwest to fail.

Young oysters begin shell building very quickly, so that within 48 hours they can begin feeding. The researchers found that oysters can start building calcium carbonate shells within 12 hours after fertilization, when they're just 1/100th the diameter of a human hair.

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But in acidic water, the oysters need to exert more energy for shell building and have less for swimming and getting food, the researchers say.

"The hatcheries call it 'lazy larvae syndrome' because these tiny oysters just sink in the water and stop swimming," said George Waldbusser of Oregon State, the lead author of the paper.

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A very small change in ocean chemistry leads to oysters that can't grow shells properly, the researchers said.

"These organisms have really sensitive windows to ocean acidification -- even more sensitive than we thought," Waldbusser said.

The findings were reported this week in the journal Nature Climate Change.