A new threat to the Chesapeake’s oysters | WYPR

A new threat to the Chesapeake’s oysters

Sep 1, 2017

Just as Maryland and Virginia are in the middle of ambitious oyster restoration efforts in Chesapeake Bay tributaries, a new threat has appeared; excess acid in the deeper waters.

According to new research out of the University of Delaware, deeper bay waters—30 to 50 feet—are becoming more acidic. That means carbon dioxide is dissolving in the water, which could potentially hurt oysters.

UD researcher Wei-Jun Cai explains that shellfish need a compound called calcium carbonate to help build their shells. If the pH of the water is low, meaning it’s more acidic, and the carbonate saturation is low, "that would be harmful," he said. "They have to be above a certain level to be saturated in the carbonate."

Without a certain level of calcium carbonate, shells would dissolve and oysters wouldn’t be able to rebuild them.

Cai is part of a 16-person research team that collected water samples in America’s largest estuary to study oxygen and pH. They analyzed changes in water chemistry by measuring pH, oxygen and dissolved in-organic carbon.

The pH of the water, Cai said, is near 7.2. That's acidic for water. He says his team will next look at how to apply their research to preserv-ing shellfish in the bay.

"To restoring the bay, we need a different aspect [approach]. For example, we need to reduce nutrient input," Cai said.

His team also is building a model to predict how pH changes in the surface water.

Journal reference: Wei-Jun Cai, Wei-Jen Huang, George W. Luther III, Denis Pierrot, Ming Li, Jeremy Testa, Ming Xue, Andrew Joesoef, Roger Mann, Jean Brodeur, Yuan-Yuan Xu, Baoshon Chen, Najid Hussain, George W. Waldbusser, Jeffrey Cornwell, & W. Michael Kemp. Redox reactions and weak buffering capacity lead to acidification in the Chesapeake Bay. Nature Communications: 8:369. DOI: 10.1038/s41467-017-00417-7.

Additional information: This study received funding through the National Oceanic and Atmospheric Administration, National Science Foundation, NASA, Delaware Sea Grant and University of Delaware.