Ocean acidification and its effects on Pacific oyster larvae
Photo courtesy of Michael Monroe and Oregon Sea Grant.
THE SUN CHIPS AWAY at the marine layer on this swiftly warming May morning in the bay. On the estuary’s muddy banks, clammers dressed in knee-high rubber boots dig in the dark sludge, while throughout the bay other aquatic farmers dredge for their prize: oysters.
The oysters are Crassostrea gigas, commonly called the Pacific oyster. These “giant oysters” measure from 3 to 15 inches long. They’re huge moneymakers for global aquaculture, and they have a special relationship to this place. This is Netarts Bay, Oregon, the center of the state’s oyster industry and home to the Whiskey Creek Shellfish Hatchery, one of the nation’s largest producers of Pacific oyster larvae. Hatcheries such as Whiskey Creek are linchpins for industry. That’s because the Pacific oyster is originally from Japan, and here on the west coast its delicate larvae grow wild in only a handful of places. For oyster growers from California to Canada to succeed, hatcheries must raise larvae. Unfortunately, as an incident at Whiskey Creek proved, the larvae are under siege.
In 2007, Pacific oyster larvae at Whiskey Creek started dying en masse. Oregon State University scientists later pinned the crime on ocean acidification. This is the term many are using to describe what’s happening in the world’s oceans as excessive atmospheric carbon dioxide (CO2)—a product of human industry’s hunger for fossil fuels—is dissolved in seawater. Once it’s in the ocean, CO2 forms carbonic acid, which lowers the water’s pH level, making it more acidic. The consensus is that ocean acidification is just getting started. As CO2 is continually pumped into the air, the world’s oceans are expected to slide further toward the acid side of the spectrum, and that, say researchers, won’t be good for animals like the Pacific oyster. That’s because oysters and other mollusks make their shells from calcium carbonate, which is becoming increasingly susceptible to breaking down in our ever-more corrosive seas. This is what happened at Whiskey Creek: the seawater in which the hatchery was raising its larvae had succumbed to ocean acidification; the larvae struggled to make shells, and died. But this isn’t the whole story.
Today, with Oregon Sea Grant’s help, OSU researchers are continuing to investigate ocean acidification’s nefarious ways. They’re gaining a better understanding of oyster larvae’s response to the phenomenon. They’re developing better seawater monitoring techniques. And they’re connecting with stakeholders in an effort to develop useful diagnostic tools for hatcheries and growers. Yet getting to this point took time. When the hatchery’s larvae started dying, it was mystifying.
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