Can eelgrass save our oysters from ocean acidification?

California researchers want to find out just how much the oft-maligned underwater plant known as eelgrass can help buffer the impact of ocean acidification on sensitive aquatic species. 

A group from the University of California Davis and UC Santa Cruz was in Orange County’s Upper Newport Bay this week to deploy water chemistry sensors in eelgrass beds that have been planted in the bay as part of an ecosystem restoration project. 

“As humans drive their cars and we burn coal, oil and natural gas, it goes into the atmosphere, and about a third of that CO2 gets absorbed by the ocean every year,” said UC Davis PhD candidate Melissa Ward. “As the ocean absorbs all that CO2 like a sponge, the water becomes more acidic.”

Scientists have found that shellfish, such as oysters and scallops, have trouble building shells in acidic ocean environments . But eelgrass and other seagrasses counter ocean acidification by pulling CO2 out of the water, much like tropical forests do on land.

Eelgrass.

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Orange County Coastkeeper

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Ward and fellow researchers are studying to what degree restored eelgrass beds can counter the effects of ocean acidification on commercial oyster farms and other fisheries.  

"It’s not going to change the whole chemistry of the ocean,” she said. "But it might actually make a measurable impact to the local-scale problems that we’re having.” 

Much of the world’s coastal seagrasses have been destroyed. Just 10 percent of the eelgrass acreage that existed in California in 1850 remains, according to the National Oceanic and Atmospheric Administration . 

In places like Newport Bay, most of the eelgrass was dredged and removed to make way for waterfront homes and docks. In recent years, the nonprofit conservation group Orange County Coastkeeper has been working to restore eelgrass in the bay. 

The state of California now has strict rules about removing eelgrass, which require homeowners and developers to do extensive mitigation and replanting if proposed projects would disturb existing beds. 

The city of Newport recently struck a unique deal with state and federal authorities designed to make it easier for homeowners to do eelgrass mitigation. 

Besides Newport Bay, Ward is also doing eelgrass research in Tomales Bay, north of San Francisco, where commercial oyster farms are threatened by ocean acidification.