What’s causing the glowing blue waves in Morro Bay?

Bioluminescent single-cell organisms make the waves glow blue in this photo of Morro Rock.
Bioluminescent single-cell organisms make the waves glow blue in this photo of Morro Rock. Instagram @adamjphotos

If you’ve explored the Morro Bay coastline after dark, you may have seen a blue glow coming from some of the waves breaking along the shoreline.

Adam Trovao and other local photographers recently observed this phenomenon just north of Morro Rock, near the Morro Creek outflow.

“It looks more like a glow stick every time the waves crash,” he said.

Trovao, a Morro Bay landscaper, spotted the glow while taking photos of the Milky Way. It initially looked like city lights reflecting off the water, creating a “nice, bright neon blue,” he said.


A post shared by Wes Bracken (@wes.coast.photo) on

This glow is actually created by bioluminescent dinoflagellates — tiny, single-cell organisms that emit a flash of light when they perceive predators, said Michael Latz, a bioluminescence researcher at the Scripps Institution of Oceanography at UC San Diego.

“They’re always around, but sometimes they get more abundant,” he said.

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A chemical reaction creates the blue-green light, which is meant to startle predators or attract other creatures that might threaten the predators, he said.

Breaking waves can stimulate dinoflagellates’ light reaction, Latz said, describing it as a “burglar alarm-type scenario.” The glow appears more blue in photos because it triggers cameras’ blue color chip, he said.

Bioluminescence is most visible off the California coast in the summer and fall, Latz said. In some parts of the Caribbean, the glow appears year-round and is featured as a tourist attraction, he said.

In Morro Bay, Trovao said more people have visited the spot to check out the neon waves since he posted his photo on Instagram.

“It was very fun to watch,” he said.

Lindsey Holden: 805-781-7939, @lindseyholden27