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The great American oyster collapse

Acidification of the world's oceans is believed to be behind plummet in oyster population in the US' Pacific Northwest.

Last updated: 21 Jul 2014 10:01
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Willapa Bay is an ideal place to farm oysters.

Vast swathes of the bay, in the northwestern US state of Washington, are exposed at low tide - making it an ideal place for oyster cultivation. It's one of the most productive oyster farming areas in the US.

But just over 10 years ago, the dynamic in the bay and other parts of the Pacific Northwest changed: Oysters started dying off, a development believed to be linked to climate change.

Dave Nisbet has been in the oyster business since 1975, when he started growing oysters on a small plot in Willapa Bay. He then opened his own business. The Nisbet Oyster Company, a family-owned operation, has been processing oysters since 1978. Nisbet's daughter Kathleen Nisbet-Moncy has worked every job in the company, and is now the plant manager, overseeing the processing of nearly one million kilogrammes of oysters a year.

In 2002, the Nisbets began noticing a drop in the number of oysters growing on their farm. But it wasn't until 2008, when they had problems obtaining enough oyster larvae from their supplier, that things started to look dire. Oyster farmers often rely on hatcheries to produce larvae, also known as seed. The hatcheries produce millions of seed that farmers buy and raise to adult size. But the hatchery the Nisbets use also saw their oyster larvae dying off in large numbers.

"It was at the point where we had nothing, so what do you do with nothing? The hatcheries were just barely pumping out a trickle, and that's all we could get," Kathleen told Al Jazeera.

Oyster larvae dying off

Nisbet and other shellfish growers in the state worked with oceanographers to determine the problem. The cause? A rise in the acidity of the water along Washington State's coast. Researchers linked this rise in acidity to the ocean's increased absorption of carbon dioxide emissions, which come in large part from burning fossil fuels.

We've already pushed our ecosystems in ways that we wish we hadn't. But we have to be real about mitigating those impacts on our ecosystems.

- Ruth Gates, research professor at the Hawaii Institute of Marine Biology

In 2008, Nobel Prize-winning climate scientist Richard Feely and four other researchers published a paper in the journal Science stating that since the beginning of the industrial era, the oceans have absorbed billions of tons of carbon emissions, raising the acidity of seawater.

Oyster larvae were dying off because the water was too acidic for them to build up the calcium carbonate they needed to form protective shells.

By 2012, the Nisbet Oyster Company saw a 42 percent decline in production. For Dave, the crisis meant the viability of his business was in jeopardy.

The Nisbets also worried about the effects on their community. The town of South Bend, home to about 1,600 people, is just a few kilometres from the Nisbet company's oyster beds. The company employs at least 70 people from South Bend, depending on the season. The shellfish industry generates about $100m annually in Washington State, and disruption of oyster farming would have been a blow to the local economy.

In 2012, the Washington State government released a report by a Nobel Prize-winning scientist, ocean researchers, shellfish growers, and other experts on the problem of ocean acidification. They made 42 recommendations for action, some of which have been implemented at the state level.

But Kathleen argues that more needs to be done on a national level to study how the oceans' rising acidity will affect the livelihood of coastal workers. "Our federal government, they need to really put it in their forefront and acknowledge that it's here and start working with people to come up with a solution to mitigate these problems," she told Al Jazeera. "There are a lot of industries on the coast that this is going to begin to affect. They've seen it in crab, they've seen it in other species as well."

Dave says reversing the acidification is probably not possible. "I think at this point you're not going to change the outcome. You can mitigate the outcome."

That view is based on scientific work: Researchers say the best thing to do is adapt to what humans have done to the world's oceans. Ruth Gates, a research professor at the Hawaii Institute of Marine Biology, studies how corals are affected by changing ocean acidity and temperature, changes that she says are linked.

Like oysters, corals need to absorb calcium carbonate to create their shells, and the impact of humans on ocean life has been enormous. "We've already pushed our ecosystems in ways that we wish we hadn't. But we have to be real about mitigating those impacts on our ecosystems," she told Al Jazeera.

'The canary in the mineshaft'

For the Nisbets, that meant starting their own hatchery in Hawaii, where the problem of ocean acidification hasn't yet been felt. In 2009, Dave worked with the University of Hawaii in Hilo to conduct a pilot programme raising oyster seed. It's been so successful that the Nisbets predict by next year they will be completely integrated, using only the seed they get from Hawaii in their oyster production.

Standing in the oyster beds at low tide, Kathleen picks up several of the Nisbet oysters - shellfish almost the size of her palm, with a distinctive deep, fluted shell. "If we would not have made the decisions we made, we would not be standing here," she says.

And while scientists have linked climate change and pollution of the world's oceans to problems with oysters and corals, there are still questions about how other species of ocean life will be affected. Gates says the world is like an island inside a large bubble. "In that bubble is a lot of carbon dioxide that we're pumping in. So we're increasing those carbon dioxide levels inside the balloon. And that forces the carbon dioxide into the ocean globally to decrease the pH [and] make the water more acidic... We can project exactly how acidic it's going to be; what we don't understand is exactly how it will influence the biology of the organisms."

The difficulties oyster farmers are facing is the beginning of what could be a larger, worldwide problem. "I think the oyster industry is kind of the canary in the mineshaft," Dave Nisbet says. "I think we're kind of the first ones, the first ones to really identify and be able to have a direct linkage to the acidification part of global warming."

By making the link between climate change and its effects on oysters, shellfish farmers have been able to save their baby oysters for now. But the acidity levels in the oceans are still rising, and the effect that will have on oysters once they've formed their shells and grow into adults is unknown.  

"What happens when things get even more acidic?" Dave asks. "That needs to be identified. I'm not sure we know the answer yet."

The answer to his question could determine whether oysters will continue to grow in Willapa Bay, and whether oyster farmers like Dave Nisbet are able to stay in business.

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Al Jazeera
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