Climate Change May Help Oysters — and Their Enemies

Warming waters help oysters grow, but also work to the advantage of their predators.

Climate change in the California region may have the potential to help oyster populations in the decades and centuries to come, according to a new study in the journal Functional EcologyFunctional Ecology. Oysters grow more rapidly in warmer waters, and so, assuming an ever-available food supply, should be able to increase their population as waters warm along the coast. That's good not only for people who like to eat them, but also for the other plants and animals that rely on them for habitat - and for coastal communities, as extensive oyster reefs can protect against storm surges and sea level rise.

So, good news all around, then? Everybody wins, right?

Welllllll, not so fast.

Climate change is not occurring in a vacuum, after all. The ecosystems it affects have almost all already been changed by human activities. In the case of oysters, the United States population has been reduced by an estimated 88 percent, due largely to overfishing and habitat change, while the Golden State's oysters are forced to contend with two invasive predatory snail species: the Atlantic and Japanese oyster drills.

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If oysters dream, then oyster drills are surely the stuff of their worst nightmares.

"To me, it's the worst way to go," said lead author Brian Cheng, a doctoral candidate at UC Davis Bodega Marine Laboratory at the time of the study and currently a postdoctoral fellow at the Smithsonian Environmental Research Center. "Imagine you're an oyster. You have a suit of armor you wear and that you cannot move. Imagine there was something that could crawl onto you and begin blasting away on your shell of armor. Imagine they could secrete acid and use a file-like tongue to bore tiny little holes into the shell. Then they insert their tongue and tear away bits of flesh, eating you alive. Once the hole is made, the oyster is basically done."

And, while warmer temperatures are good for oyster growth, in the short-to-medium term they're even better for oyster drills.

"The optimum temperature is probably already here for Japanese drills, or could possibly be here with the next 1 degree Celsius of warming," Cheng told Seeker. "For Atlantic drills, the optimum is a bit farther out. But leading up to the optimum, we have increased foraging, increased growth. So even though oyster growth itself also appears to be favored by warmer temperatures, it's not clear that that would outpace consumption by their enemies."

Remove the drills, however, and theoretically the oysters could do just fine. And the good news is, it's entirely possible - if a tad labor-intensive - to do just that.

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"For a start, they're snails so they don't move very fast," said Cheng. "They're very easy to identify: They don't look like other snails that are found in the same habitat." And, unlike many other marine species, they do not lay eggs that disperse in the water column; rather, their eggs hatch, as baby snails, on the beach. Plus, they're seasonal: There are peak periods to target for snail removal.

It's an illustration, said Cheng, of the cumulative impacts of human activities, but also of how, while battling global warming can be daunting, there are other ways in which people can help protect species and ecosystems against its effects.

"I think it's worthwhile to consider the big picture," Cheng said. "And while obviously we should be thinking about climate change and greenhouse gas emissions, there are some problems, such as invasive species, that people around, say, San Francisco Bay can do something about. It can seem like such a grand challenge to think about greenhouse gas emissions; here's something we can do right now on a local scale that can have enormous impact."

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