The Seagrass that could save oysters from climate change

Seagrass meadows

The impacts of climate change aren’t a distant threat for the Pacific shellfish industry. Acidifying seawater is already causing problems for oyster farms along the West Coast and it’s only expected to get worse.

This has one Bay Area oyster farm looking for ways to adapt by teaming up with scientists, who are studying how the local ecosystem could lend a helping hand.

“We need help,” says Terry Sawyer of Hog Island Oyster Company. “That ‘canary in a coalmine’ analogy drives me crazy, but that’s what we are.”

By that, he means that oysters are an “indicator species” on the frying edge of a changing climate.

Sawyer’s own natural habitat is on the mudflats of Tomales Bay, about 50 miles north of San Francisco, where his oyster operation is located. But a few years ago, he started going to climate change conferences, sitting next to scientists and policymakers.

For Sawyer, these wonky affairs are a necessity. Like a lot of oyster farmers, he buys baby oysters from hatcheries in Oregon and Washington. But starting a decade ago, the hatcheries began having mysterious die-offs.

Scientists eventually identified the main culprit: increasingly acidic seawater.

Carbon Sponge

At least a quarter of the carbon humans put into the atmosphere from burning fossil fuels is absorbed by the ocean. It acts like a carbon sponge, but adding carbon to seawater makes it more acidic. Since the start of the Industrial Revolution, the oceans have become about 30 percent more acidic.

It’s harmful for animals that build shells, like oysters, and spells big trouble for the Pacific shellfish industry, worth more than $100 million.

Sawyer found some help by opening up his oyster farm to a team of scientists. Equipment monitors the water’s acidity in real time, part of a network run by UC Davis’s Bodega Marine Lab.

The oyster farm is also assisting with cutting-edge scientific research, focused on how oysters could get a boost from native plants in Tomales Bay.


On a sunny morning, a team of scientists is scuba-diving in a shallow part of the bay, surrounded by thick, green seagrass, waving in the current.

This seagrass is a glimmer of hope for oyster farmers. Plants, whether it’s a forest or lawn, take up carbon dioxide and use it for photosynthesis.

The seagrass pulls the carbon out of the water, which makes it slightly less acidic.

The researchers are testing whether seagrasses could act as a buffer, protecting the oysters nearby. The approach is being studied around the world in different ecosystems, including near coral reefs, and using bigger marine plants, like kelp.

Read the full article at KQED Science.

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