Sea Change
An acid peril is rising from the depths and falling from the air. It kills local oysters and threatens everything that lives in the sea.
Meanwhile, V. tubiashii struck at other hatcheries and oyster farms—in Willapa Bay, on the Hood Canal, all the way up to British Columbia. Willapa growers who’d formerly relied on natural spawning to replenish their beds had to buy hatchery seed, which grew increasingly scarce. The Pacific Coast Shellfish Growers Association announced a “seed supply crisis” and implored members to pony up for research at Whiskey Creek to find the cause.
In 2008 scientists from Oregon State University started monitoring Whiskey Creek’s water chemistry; NOAA scientists from Seattle monitored the waters offshore. Their data together revealed that the die-offs coincided with spikes in the water’s acidity (or, more precisely, with drops in its alkalinity, since seawater is mildly alkaline). These spikes reflected surges of cold water from deep offshore, stirred up by what Wiegardt says were unusually intense winds: “There was a direct correlation between upwelling events, aggressive northwest winds, and our inability to grow larvae.”
Often this upwelled water had more than three times the relative acidity of the surface waters where oysters grow. It even looked different, says Wiegardt: “It’s bluish-gray, with a distinct charcoal look. It looks dead.” But it didn’t harm adult oysters—only their larvae.
Whiskey Creek and the Northwest’s other shellfish hatcheries had become accidental laboratories for one of the hottest, and most worrisome, questions in ocean and climate studies—a phenomenon so new to science that the term for it, ocean acidification, was coined just seven years ago.
When Jeremy Brown headed out for salmon last spring, the herring and needlefish that the salmon usually feed on were missing, both from his echo sounder and from the bellies of the salmon he caught: “They just weren’t showing up where you’d expect to find them.” He wonders if acidification might be the reason; these small fish feed on pteropods and other shelled zooplankton.
The role of carbon in the die-offs at Whiskey Creek is much more firmly established. Even a seeming anomaly—the fact that only oyster larvae died while grown oysters thrived—pointed to acidification. Many marine animals, including coral and pteropods, sheath themselves with aragonite, a carbonate crystal that dissolves readily as the pH of their aquatic environment drops. Others, including mature oysters, build shells of calcite, a much more resistant crystal.
Wiegardt and Cudd had their culprit. But correcting the problem, even in the confined quarters of a hatchery tank, is another matter. Simply buffering the water to make it more alkaline doesn’t work, says Wiegardt: “Seawater chemistry is very complex. There are lots of trace elements there”—and upwellings of carbonated water may affect their balances, too.
Ocean acidification and global warming share a common cause; the seas have absorbed an estimated third of the CO2 released into the atmosphere since the Industrial Revolution, and their average acidity has risen about 30 percent. But the link between recent warming and the carbonated water that’s welled up and struck Whiskey Creek is at best indirect. Scientists can date water by its chemical signature, and these upwellings contain “old water” that’s sat in the deep for 50 years or more. But OSU shellfish aquaculturist Chris Langdon, who’s monitored Whiskey Creek, says that old water’s acidity may still reflect recent emissions: Increasing CO2 in the atmosphere can stimulate bumper plankton blooms that die, sink, and rot, acidifying deep old water. And the winds that then stir up that water may themselves result from surface warming.
Published: March 2010
Thanks for an excellent article.
We know what the cause is… and we know what to do about it.
The obstructions now are political