Oyster larvae are being killed by acidification of seawater
- 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 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.
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.
Because of the way seawater circulates around the world, the deep water now washing ashore in Oregon and Washington is actually 30 to 50 years old and absorbed its CO2 long before the fall of the Berlin Wall. This time lag is important because oceans absorb about 50 percent of the CO2 released by burning fossil fuels, emissions that have been rising dramatically in recent decades. According to the National Oceanic and Atmospheric Administration (NOAA) ocean acidity has increased approximately 30 percent since the Industrial Revolution, and if we continue our current rate of carbon emissions, global oceans could be 150 percent more acidic by the end of the century than they have been for 20 million years.
Click here to read full article at Yale Environment 360
Click here to visit Department of Fisheries and Oceans page on ocean acidification
Download the website sponsorship guide