Oysters on Acid

C. gigas 4day shallow_tif__004 copyThe oceans are about 30 percent more acidic than they were a century ago, and scientists are beginning to understand the consequences for marine ecosystems. Oysters may provide an early warning of what’s to come.

George Waldbusser, a biogeochemist in the College of Earth, Ocean, and Atmospheric Sciences, and Elizabeth Brunner, a master’s student, conducted an experiment with oyster larvae, which are about the width of a human hair. One group of larvae was grown in water from deep in Puget Sound. Its level of acidity was equivalent to that forecast for the global ocean in the next 100 years. Another was grown in surface water under current conditions. The researchers used scanning electron microscopy to compare larval development after four days in the Taylors shellfish hatchery in Washington state.

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Their images show clearly that oyster larvae falter when they are grown in acidified water. A small misshapen shell (left) dooms them to a life cut short. That’s because shell development is required for other stages of oyster growth, says Waldbusser, who uses SEM to study the dynamics of the process. “It’s really important that they get the shell built in a short window of time. Increasing atmospheric CO2 levels will shrink the window for initial shell formation.”