The Earth’s oceans have been absorbing massive amounts of gasses released by burning fossil fuels, and the resulting acidification of seawater is threatening one of mankind’s most popular aphrodisiacs: oysters.
Photo via Flickr user Jeffrey Bary
Ah, progress. Since the advent of the Industrial Revolution two centuries ago, our world has crowded with technological advancements of stunning innovation: the steam engine. The railroad. The Banana Bunker. But there's been another, far less desirable thing filling our world over the past two hundred years: two trillion tons of carbon dioxide gas, the result of all the fossil fuels we've burned to power our Herculean efforts. A full quarter of the gas has been absorbed by Earth's oceans, and the resulting acidification of seawater is threatening one of mankind's primary aphrodisiacs: oysters.
Ocean life around the world is struggling to adapt to waters that are 30 percent more acidic than they were in the 19th century, but the species most at risk are shellfish such as oysters, clams, and mussels. These tasty invertebrates form their shells of calcium carbonate, a mineral that abounds in the oceans but whose ions are made less available when carbon dioxide interacts with water molecules. When those ions aren't available, tiny and vulnerable baby shellfish aren't able to build their shells and die in mass numbers.
It's a problem with which Bill Dewey of Washington State's Taylor Shellfish Farms is all too familiar. The family-owned shellfish farm is the largest in the country and has raised clams, geoducks, mussels, and oysters since the 1890s. But around 2006, Dewey said, the farm's oyster larvae—which, in order to survive and grow, must begin to form their shell within two days of hatching—began dying off at rates that at first seemed inexplicable.
"That's when things started to shift," he said. "And we weren't sure why. At first we thought it was a bacteria-related problem, and we took all the necessary steps to address that. It didn't work."
Over the next year, Dewey said, the production problems only got worse, culminating in a catastrophic 2008-2009 season when 75 percent of the farm's larvae, which are grown in temperature-controlled tanks and feed on farm-grown algae, died off before forming their shells. And the problem wasn't limited to the Taylor farm: all along Pacific Northwest coastlines—where shellfish farming is a traditional and vital part of the local economy, providing more than 3,000 jobs and creating about $3 million in annual revenue—shellfish larva were perishing in record numbers. One Washington farm, Goose Point Oysters, even spent $1 million to move its larvae-raising operations to Hilo, Hawaii, fearing a total collapse of the business if growing conditions on the west coast continued to decline.
The worst part of the crisis, Dewey said, was the lack of a clear explanation for the oysters' deaths. The conundrum wasn't solved until the National Oceanic and Atmospheric Administration, an arm of the US Department of Commerce, came to the northwest to figure out what was killing the oysters once and for all. Using $500,000 of federal grant money, NOAA visited shellfish farms including Taylor and installed sophisticated water quality monitoring equipment. That's when the culprit—ocean acidification as a result of carbon emissions—was discovered.
Farmers in the Pacific Northwest operate under particularly fraught conditions. Due to natural seasonal "upwellings" of normally low-lying coastal seawater, they have to deal with water that's even higher in carbon dioxide content than it is in most places in the world. As Richard Feely, a NOAA oceanographer and one of the world's authorities on ocean acidification, explained, surface water that becomes saturated with carbon dioxide tends to sink to the ocean floor. But at the eastern boundary of a large ocean—like the Pacific—northwest winds that are particularly strong from April through October drive surface water away from the coastline, and water from the ocean floor gets sucked up onto the coast to takes its place.
"The combined effects of carbon dioxide absorption and these upwellings have led to a pH of 7.7," Feely said, "where the pH of healthy ocean water is 8.1."
Since that catastrophic 2008 season—and after investing a whole lot of money in research—Taylor Shellfish Farms has developed a workaround that, for now, is keeping its baby oysters healthy. Using sodium bicarbonate, workers can control the pH level in the oyster larvae tanks, and by the time the oysters are transferred to the nursery waters where they grow larger, their shells are solid enough to withstand higher-acidity waters. It's an easy solution, Dewey said, and best of all, it's cheap, running the farm only about $14 a day.
But Dewey said he's all too aware that the remedy is temporary at best and that his entire industry remains on the precipice.
"If we stick to our same old ways, conditions will get far worse," he said. "We've learned that the ocean isn't as big as we thought it was. It's already 30 percent more acidic than it was 250 years ago, and by the end of this century it will be 150 percent more acidic. People need to wake up."
Feely, the oceanographer, concurred. He pointed out that smaller crustaceans such as terrapod snails—a critical source of food for the finfish, like salmon and pollock, that we love to eat—are also dissolving in seawater, and the collapse of the oceans' food chain could soon cause a food crisis. So the next time you revel in the glories of technology—$10,000 Japanese toilets, the newest version of Candy Crush—take a moment to consider the fate of the humble sea snail.