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This aquatic grass could help shellfish threatened by ocean acidification

An increase in carbon emissions are showing up not only in the air, but also in water. Now researchers and shellfish farmers are teaming up to see how marine plants can help stave off the effects of ocean acidification. Special correspondent Jes Burns of Oregon Public Broadcasting reports.

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  • Judy Woodruff:

    An increase in carbon emissions are showing up not only in the air, but also in water.

    As Oregon Public Broadcasting's Jes Burns reports, researchers and shellfish farmers are teaming up to see how marine plants can help stave off the effects of ocean acidification.

    This report was produced in collaboration with the public media partnership EarthFix and is part of this week's Leading Edge series, which focuses on science, tech and medicine.

  • Jes Burns:

    Tide is money at Baywater Shellfish farm West of Seattle.

  • Woman:

    These geoduck are so big.

  • Jes Burns:

    The tide flat is exposed for only a few hours a day, and there's work to be done in the geoduck clam patch, pulling tube.

  • Man:

    These guys are really hard to pull out.

  • Jes Burns:

    The tubes kept the clams safe the first two years of their lives. Joth Davis owns Baywater, part of the Pacific Northwest's $200 million shellfish industry. He grows geoduck for export and other clams and oysters for local markets on the West Coast. But both his business and the industry are in trouble.

  • Joth Davis:

    It's just more difficult to raise oyster larvae these days than it used to be. They used to be kind of weedy, and you could grow oyster larvae easily. Now it's not the case.

  • Jes Burns:

    That's because the ocean's chemistry is changing. It's called ocean acidification.

    And it's in part caused by people pumping carbon dioxide into the atmosphere at unprecedented rates. The ocean acts like a giant carbon sponge. And all that extra CO2 causes the pH of the seawater to decrease.

    But it's not really the acid that's hurting shellfish. Baby oysters use certain compounds to build their shells. The same chemical reaction that lowers the pH of the water transforms those building blocks into something the oysters can't use.

    And the more carbon there is, the more difficult it could become for any sea creature with a shell to survive; 250 miles south, along Oregon's coast, scientists like George Waldbusser are discovering a common aquatic plant called eelgrass could make a big difference.

    Eelgrass is like other plants that use photosynthesis. It gets energy by absorbing sunlight and carbon dioxide. And that could lessen the effects of ocean acidification.

  • George Waldbusser:

    They're the same species of oysters. On this shell, what we have are Pacific oyster larvae or juveniles. All these dark areas are individual oysters. And these have been grown in the eelgrass bed.

    And then, on this shell, we have again small oysters, fewer of them, and much smaller that have been grown not in the eelgrass bed.

  • Jes Burns:

    Fellow Oregon State University researcher Caitlin Magel has been stopping at estuaries in Oregon and Washington, taking random samples from the flats.

    She's trying to get a handle on just how much carbon these shallow eelgrass beds are pulling out of the water by sampling the plants' shoots and roots.

  • Caitlin Magel:

    They have this below-ground carbon storage that can lead to long-term sequestration of carbon.

  • Jes Burns:

    Eelgrass could benefit shellfish growers in different ways.

  • Caitlin Magel:

    It could be grown in and amongst, for instance, an oyster aquaculture bed. Or, in the case of a shellfish hatchery, they could pinpoint where they're drawing their water in from, so that they are drawing from within an eelgrass bed.

  • Jes Burns:

    And that water would have more of those shell-building compounds needed by the oysters to grow.

    Back at Baywater, Joth Davis wants to take the idea of using ocean plants to sequester carbon to a new, deeper and tastier level.

  • Joth Davis:

    We got some fresh sugar kelp. It's a little tough, but it's definitely edible and yummy.

  • Jes Burns:

    A team organized by Davis and Puget Sound Restoration Fund director Betsy Peabody has been tracking kelp growth at a nearby test plot.

  • Betsy Peabody:

    What we're trying to do is deliberately grow kelp within a specific area, and thereby remove CO2, and measure whether or not that improves conditions locally.

    You could create, in theory, a kind of seaweed filter, you know, a curtain around where you're growing shellfish.

  • Jes Burns:

    Much of the kelp is more than six feet long, and that mass of algae is evidence of carbon pulled from the water.

  • Joth Davis:

    I'm looking at interspersing shellfish in baskets, hanging below buoys, and then every other line would be kelp. Between the two of them, we will be able to harvest kelp and shellfish.

  • Jes Burns:

    Marine plants aren't likely to provide relief from carbon emissions on a broad scale.

    But for shellfish growers and researchers in the Pacific Northwest, the greener grass on the other side of ocean acidification is beginning to look more like tide-swept eelgrass and towering forests of kelp.

    For "PBS NewsHour," I'm Jes Burns on Washington's Hood Canal.

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