How crushed shells are helping restore Bay Area oyster and clam ecosystems, combat climate change

SAN FRANCISCO (KGO) -- At San Francisco's Presidio, wildlife ecologists are using nesting pods made with ground-up oyster shells, designed to attract and nurture tiny, growing oysters. It's a shoreline project that may eventually help their broader ecosystem.

"We anticipate more oysters coming in, and not just more coming in and settling, but those that settle, survive and grow, and hopefully can reproduce on their own seeding more of the Bay with their planktonic larvae," explains ecologist Jonathan Young.
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Meanwhile, a short drive north along the Sonoma County coast, researchers from UC Davis are also using ground-up shells, this time from clams. Their goal is to help combat a threat from climate change. It's caused by pollution from fossil fuels that are making seawater more acidic.

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"The idea that I am working on is that purposeful addition of shell material into sediments can interact with that acidic seawater, and actually buffer against the changes that we're seeing due to the climate change," says researcher Hannah Hensel.

Hensel began collecting the shells near the UC Davis Marine Laboratory at Bodega Bay. She wanted to learn if an acid-buffering calcium component in the shells could help keep the tidal habitat less acidic, first testing her theory in lab experiments.
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"So we did see a buffering effect," she says. "And in addition to the chemistry changing and data suggesting that that was the case, we also saw with the clam growth, that the clams grown with shell hash grew more shell than those without it."

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Hensel is hoping that mixing shells into the squishy breeding ground can help young clams survive and develop in a more balanced shoreline environment, even if surrounding oceans become more acidic.

Meanwhile, back at the Presidio, Young says the shell-laced Oyster pods are also having success. The pods are drawing in residents attracted to the chemistry of their new homes, which they may associate with the optimal breeding environment.
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"Which means planktonic larvae floating around the Bay have found these structures, have landed on these structures and had been growing on these structures," Young explains.



Ultimately, they are two research projects, both leveraging nature-based techniques, to create a healthier ecosystem for California.

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