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Giant Rivers in the Sky Wipe Out Mass Numbers of Oysters

Looking for something new to worry about? A recent study found that giant invisible rivers in the sky carrying up to 15 times the amount of water in the Mississippi River can cause severe flooding and nearly wiped out an entire species of oysters in California in 2011. Need more? Climate change is making them worse. Crying yet? The oysters may come back eventually but they’ll be smaller and have less aphrodisiac powers. Oh, the humanity!

This shows us one way in which extreme events might affect coastal ecosystems. Oysters can help buffer shorelines and enhance biodiversity, but this is one facet of climate change that might be a hurdle for oyster restoration efforts in San Francisco Bay.

While working on his Ph.D. at the UC Davis Bodega Marine Laboratory in 2010, National Estuarine Research Reserve (NERR) fellow Brian Cheng was studying oysters, not giant invisible rivers in the sky. Specifically, he and colleagues were studying wild Olympia oysters at China Camp State Park in northern San Francisco Bay. Normal density at the park is 3,000 oysters per square meter, compared to 100 oysters per square meter in the next most populated site.

Wild oysters on the shoreline at China Camp Beach in San Francisco Bay in 2011. Nearly all of them died following an atmospheric river event in 2011. Credit: Brian Cheng/UC Davis

Wild oysters on the shoreline at China Camp Beach in San Francisco Bay in 2011. Nearly all of them died following an atmospheric river event in 2011. Credit: Brian Cheng/UC Davis

And then, in March 2011, nearly all of the Camp State oysters mysteriously died.

Cheng and his team determined the die-off was caused by low salinity from the freshwater discharge into the bay from rainfall over the Sierra Nevada. Three massive atmospheric river storms occurred immediately before the event. For the first time, they were able to link the rivers in the sky to a disaster other than flooding.

According to Cheng’s report in the current edition of the journal Proceedings of the Royal Society B, atmospheric rivers are a known meteorological phenomenon consisting of long, narrow tubes of concentrated moisture flowing through the lower atmosphere. The largest can hold up to 15 times the water in the Mississippi and the deluges they cause can drop half of California’s annual rainfall in less than two weeks.

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Satellite image of an atmospheric river getting ready to hit California

The wild oyster die-off in China Camp affected many of the smaller oyster populations as well, which were already suffering. Cheng believes the huge numbers in China Camp fed the other areas with young oysters. While it looks like they’re coming back, they’re not coming back strong.

On the one hand, it’s good news that despite the mass die-off, a few years later, they came back. But it’s not as simple as that. These new oysters are smaller and less fertile, and that may have consequences for restoring oysters in San Francisco Bay.

Olympia oysters are underwater canaries in the coal mine, so their demise at the watery hands of giant rivers in the sky means other species – and eventually humans – will be vulnerable soon.

Perhaps the thought of no more oyster-fueled nights of passion will convince the powers that be to move on climate change.