Can Giant Seaweed Decarbonize the Oceans?

It’s green, slimy, and rubbery, and it can grow as tall as an eight-storey building. Marine kelp may also be at least a partial answer to a problem causing alarm among biologists and gourmands, if not yet most of the wider public: the acidification of the oceans.

“The worry is that ocean acidification is going to slow the growth of cultured oysters, mussels, and others to a point where they’re not going to be sustainable or profitable in the future,” said Nichole Price, one of the scientists involved in the research.

As human emissions of carbon dioxide have exceeded the capacity of the planet’s atmosphere to metabolize the gas, as much as 40% of the output has been absorbed in seawater. That has slowed atmospheric warming, but lowered the pH of the water as the carbon reacts with other elements to form carbonic acid. The more acidic the water, the harder it is for crustaceans, including economically significant species like oysters, clams, crabs, mussels, and shrimp, to form shells.

Kelp—a variety of marine algae bigger than most plants—absorbs carbon from the sea to form its structure, just as terrestrial trees do. Initial tests in Washington State, where ocean acidification threatens a shellfish industry worth US$184 million a year, found a “halo” of higher pH (less acidity) around kelp growths, ABC News reports.

Now Microsoft co-founder Paul Allen is funding research to determine whether plantations of fast-growing kelp can remove enough carbon from seawater to protect nearby shellfish. A research team will grow sugar and bull kelp in Hood Canal, in Puget Sound west of Seattle, and monitor the chemistry of its water to figure out much dissolved CO2 the growing kelp is taking up.

Growing kelp near shellfish farms won’t solve the larger global acidification problem, researcher Price admits. But it might help mitigate it on a small, local scale.