The acidification of the world’s oceans from an excess of CO2 emissions has already begun, as evidenced recently by the widespread mortality of oyster larvae in the Pacific Northwest. Scientists say this is just a harbinger of things to come if greenhouse gas emissions continue to soar. — By Elizabeth Grossman
Standing on the shores of Netarts Bay in Oregon on a sunny fall morning, it’s hard to imagine that the fate of the oysters being raised here at the Whiskey Creek Shellfish Hatchery is being determined by what came out of smokestacks and tailpipes in the 1960s and ‘70s. But this rural coastal spot and the shellfish it has nurtured for centuries are a bellwether of one of the most palpable changes being caused by global carbon dioxide emissions —ocean acidification.
It was here, from 2006 to 2008, that oyster larvae began dying dramatically, with hatchery owners Mark Wiegardt and his wife, Sue Cudd, experiencing larvae losses of 70 to 80 percent. “Historically we’ve had larvae mortalities,” says Wiegardt, but those deaths were usually related to bacteria. After spending thousands of dollars to disinfect and filter out pathogens, the hatchery’s oyster larvae were still dying.
Finally, the couple enlisted the help of Burke Hales, a biogeochemist and ocean ecologist at Oregon State University. He soon homed in on the carbon chemistry of the water. “My wife sent a few samples in and Hales said someone had screwed up the samples because the [dissolved CO2 gas] level was so ridiculously high,” says Wiegardt, a fourth-generation oyster farmer. But the measurements were accurate. What the Whiskey Creek hatchery was experiencing was acidic seawater, caused by the ocean absorbing excessive amounts of CO2 from the air.
Ocean acidification — which makes it difficult for shellfish, corals, sea urchins, and other creatures to form the shells or calcium-based structures
The region’s thriving oyster hatcheries have had to scramble to adapt to these increases in acidity.
they need to live — was supposed to be a problem of the future. But because of patterns of ocean circulation, Pacific Northwest shellfish are already on the front lines of these potentially devastating changes in ocean chemistry. Colder, more acidic waters are welling up from the depths of the Pacific Ocean and streaming ashore in the fjords, bays, and estuaries of Oregon, Washington, and British Columbia, exacting an environmental and economic toll on the region’s famed oysters.
For the past six years, wild oysters in Willapa Bay, Washington, have failed to reproduce successfully because corrosive waters have prevented oyster larvae from forming shells. Wild oysters in Puget Sound and off the east coast of Vancouver Island also have experienced reproductive failure because of acidic waters. Other wild oyster beds in the Pacific Northwest have sustained losses in recent years at the same time that scientists have been measuring alarmingly corrosive water along the Pacific coast.
The region’s thriving oyster hatcheries have had to scramble to adapt to these increases in acidity, which pose a threat to their very existence. Some of the largest operations, such as Whiskey Creek, are buffering the water in which they grow their larvae, essentially giving their tanks a dose of antacid in the form of sodium bicarbonate.
While the operation may look modest — a handful of small buildings just yards from the shore of a wide bay — Whiskey Creek is one of the largest suppliers of oyster seed on the West Coast. Its baby oysters are grown all along the U.S. Pacific coast, where the oyster industry is currently valued at about $73 million annually. Washington’s Taylor Shellfish Hatchery — the country’s largest producer of farmed shellfish and one of the largest oyster producers — has also experienced dramatic losses. Its hatchery on Hood Canal, which has had some of the Pacific Northwest’s highest levels of ocean acidification, experienced the loss of about three-quarters of its oyster larvae before the owners began buffering the high acidity.
Together, Whiskey Creek and Taylor Shellfish, which also raises clams and mussels, account for most of the West Coast’s commercial shellfish production. Oysters are the biggest product, making up more than 80 percent of the Pacific coast shellfish produced and more than 60 percent of the revenue. According to industry and federal officials, the West Coast oyster industry generates about 3,000 jobs and has a total annual economic impact of about $207 million — significant numbers for their coastal communities.
The situation at the hatcheries has improved substantially in the past couple of years, thanks largely to an ongoing, intensive scientific monitoring effort and to measures to control the pH of seawater in the tanks where oyster larvae are raised. But ocean acidification continues apace, which makes understanding what’s been happening to Whiskey Creek oysters vital to grasping what will eventually threaten every ocean organism that builds a shell or coral branch.
Read the rest of the story on Yale environment 360.