Shellfish woes

Posted on The Star Online: 24 Sep 2013 — By Craig Welsh — Oysters are at risk from ocean acidification, as are farmers’ livelihoods.


IT appears at the end of a palm tree-lined drive, not far from piles of hardened black lava: the newest addition to the US Pacific Northwest’s famed oyster industry. Half an ocean from Seattle, on a green patch of island below a tropical volcano, a Washington state oyster family built a 1,800sqm shellfish hatchery.


Ocean acidification left the Nisbet family no choice. Carbon dioxide from fossil fuel emissions had turned sea water in Willapa Bay along Washington’s coast so lethal that young Pacific oysters stopped growing. The same corrosive ocean water got sucked into an Oregon hatchery and routinely killed larvae the family bought as oyster seed. So, the Nisbets became the closest thing the world has seen to ocean acidification refugees. They took out loans and spent US$1mil (RM31mil) and moved half their production 4,800km away to Hilo, Hawaii.

“I was afraid for everything we’d built,” Goose Point Oyster Co founder Dave Nisbet said of the hatchery, which opened last year. “We had to do something.”

Oysters started dying by the billions along the Northwest coast in 2005, and have been struggling ever since. When scientists cautiously linked the deaths to plummeting ocean pH in 2008 and 2009, few outside the West Coast’s US$110 mil industry believed it.

By the time scientists confirmed it early last year, the region’s several hundred oyster growers had become a global harbinger – the first tangible sign anywhere in the world that ocean acidification already was walloping marine life and hurting people.


The blame game

It’s hard to imagine now how far CO2 was from anyone’s mind when the oysters crashed. In 2005, when no young oysters survived in Willapa Bay at all, farmers blamed the vagaries of nature. After two more years with essentially no reproduction, panic set in. Then things got worse. Owners initially suspected bacteria, but shellfish died even when it wasn’t present.

No one, anywhere, could tell the oyster growers what was wrong. Then, they met the oceanographers. Dick Feely, with the National Oceanic and Atmospheric Administration, by the early 2000s was noting a dramatic change off the West Coast. Low pH water naturally occurred hundreds of feet down, where the colder water held more CO2. But that corrosive water was rising swiftly, getting ever closer to the surface where most of the marine life humans care about lived.

In 2007, Feely organised a crew of scientists to measure and track that water from Canada to Mexico. “What surprised us was we actually saw these very corrosive waters for the very first time get to the surface in Northern California,” he said.

That hadn’t been expected for 50 to 100 years. And that wasn’t the worst of it. Because of the way the ocean circulates, the corrosive water that surfaces off Washington, California and Oregon is the result of CO2 that entered the sea decades earlier. Even if emissions get halted immediately, West Coast sea chemistry – unlike the oceans at large – would worsen for several decades before levelling out. It would take 30 to 50 years before the worst of it reached the surface.

Feely published his findings in 2008. He explained to the oyster farmers that when north winds blew, deep ocean water was drawn right to the beach, which meant this newly corrosive water got sucked into the hatchery. Over several years, the hatcheries tested their water using high-tech pH sensors. When the pH was low, baby oysters died within two days. By drawing water only when the pH was normal, shellfish production got back on track.

It wasn’t until 2012 that Feely and a team from Oregon State University finally showed with certainty that acidification had caused the problem. Early this summer OSU professor George Waldbusser demonstrated precisely how. The oysters were not dissolving. They were dying because the corrosive water forced the young animals to use too much energy. Acidification had robbed the water of important minerals, so the oysters worked far harder to extract what they needed to build their shells.


Adapting to change

Waldbusser is still not entirely sure why acidification has not hit other oyster species. It could be because other species, such as the native Olympic, have evolved to be more adaptable to high CO2, or because they rear larvae differently, or spawn at a time of the year when corrosive water is less common. It could also be that acidification is just not quite bad enough yet to do them harm.

For now, no one else has taken as dramatic a step as the Nisbets. The Northwest industry is getting around the problem. Hatcheries have changed the timing of when they draw in water. Scientists installed ocean monitors that give hatchery owners a few days’ notice that conditions will be poor for rearing larvae. Growers are crushing up shells and adding chemicals to the water to make it less corrosive. Shellfish geneticists are working to breed new strains of oysters that are more resistant to low pH water. But no one thinks any of that will work forever.

Currently, the problem only strikes oysters at the early stages of their development, within the first week of life. But, for how long? How would they respond to changes in the food web? – The Seattle Times/McClatchy-Tribune Information Services

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