Shellfish genetics could be the key to climate change adaptation

A recent NOAA study found that by 2040, Alaskan shellfish hatcheries may no longer be sustainable because of ocean acidification, unless serious mitigation efforts are put in place. We recently reported on a hatchery in Oregon that’s become a model for adapting to these different conditions. But the long term solution may actually lie in shellfish genes.

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Diagram of upwelling which is a cycle of seasonal winds pushing newer oxygen-rich water off the surface of the ocean and older, nutrient and CO2 rich water rising up to take its place causing a lot of pH fluctuation. (Image courtesy of NOAA)
Diagram of upwelling which is a cycle of seasonal winds pushing newer oxygen-rich water off the surface of the ocean and older, nutrient and CO2 rich water rising up to take its place causing a lot of pH fluctuation. (Image courtesy of NOAA)

Evolution and resiliency are the buzzwords for a sustainable mariculture industry in Alaska, a state that is particularly vulnerable.

“And Alaska is going to be the test bed unfortunately for informing us for how the rest of the ecosystem will respond to ocean acidification,” says Jeremy Mathis, a NOAA oceanographer who worked on the recent study based at the Alutiiq Pride Shellfish Hatchery in Seward.

One short-term solution hatcheries are testing is injecting the acidic ocean water with carbonates that are needed for organisms like clams and mussels to develop hard shells.

But in the long term, Mathis says they may need to turn to genetics for answers.

“Ideally we can start looking at species that are more resilient to ocean acidification and adapting the commercial fisheries and commercial processing to animals that have that robustness to tolerate ocean acidification as opposed to the ones that are more vulnerable to it,” says Mathis.

That’s where scientists like Gretchen Hofmann come in. She’s a marine biology professor at the University of California, Santa Barbara.

“I work on marine invertebrates and sometimes fish and we study how they respond to their environment. We would call it environment-organism interactions and lately we’ve been interested in how these organisms will respond to future changes in ocean pH and ocean warming,” says Hofmann.

She’s a leader in what Mathis calls the emerging field of genetic adaptability.

“So it really just started with a conversation with oceanographers who were thinking about this and from there, we started to do experiments, and then we started to ask deeper questions about whether or not organisms could adapt to these changes in the ocean and even if there are already genotypes and strains of organisms that are able to handle a low pH condition,” says Hofmann.

She says the first experiments they did were a bit too basic for Mother Nature. They’d take species, put them in water with different pH, and see how they’d react. That didn’t reflect natural variations in ocean conditions.

“What we found was that there wasn’t just this straight line, no pH change, but that pH was going up and down sometimes quite dramatically,” says Hofmann.

Alaskan waters, for example, are very cold and have shifting pH depending on the seasons, fresh water inputs, and how much CO2-rich glacial melt is present.

From Washington to California, the coast is subject to a phenomenon known as upwelling, which is a cycle of seasonal winds pushing newer oxygen-rich water off the surface of the ocean and older, nutrient and CO2 rich water rising up to take its place. That means a lot of pH fluctuation.

So, Hofmann says they shifted their sea urchin research to take upwelling into account.

“And we formed the hypothesis to test that the adults from the place where there was a lot of low pH exposure would be genetically different from the wimpy ones that did not experience all that pH stress,” says Hofmann.

They found that the urchins from areas with upwelling had a different genetic signature from those who weren’t and their progeny, or babies, were more tolerant of acidic water.

“It was even more interesting because it looked like the trait of being able to tolerate that low pH, that was heritable,” says Hofmann.

She points to work being done in New Zealand, where different types of green-shelled mussels are being cross-bred to develop a new resistant and adaptive strain.

So, an Alaskan hatchery, for example, could choose to make the shift from some common species being raised now to ones that selectively favor that trait.

But it also may mean letting go of consumer preference for certain types of clams, mussels, and other shellfish that just don’t measure up.

“These are things that we should be taking a strong look at because it could be that there are other strains of shellfish that could be used that would be more successful in a mariculture setting. But, it is a very thorny issue and one that I think science could bring a lot of daylight to, I think, if we work together on it,” says Hofmann.

Hofmann says it’s important for industry and scientists to start partnering now, to get ahead of the game as much as possible.

“The first thing we have to do though is get carbon dioxide emission levels under control and then we can deal with the damage that has already been done through mitigation and adaptation strategies,” says Mathis.

Because, the problem will only get worse with each coming year.