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At night, a red tide glows blue along the San Diego County coast

September 29, 2011 |  9:28 pm

Find a dark spot on the San Diego County coastline after night falls and you might be be treated to a spectacular neon blue light show.

Bioluminescent waves, which glow a vivid blue as they crash ashore, have been dazzling nighttime visitors to the beach this week. Photographers have been snapping photos of the otherworldly surf as it has increased in intensity over the last few days.

The electric blue glow is caused by an algae bloom commonly referred to as a “red tide.” The organism,  a phytoplankton called Lingulodinium polyedrum, has bloomed since late August, turning the water a brownish-red color in the daytime, according to UC San Diego scientists.

The movement of the waves turns the tide a brilliant blue, visible only after night falls.

It’s caused by a chemical reaction on the cellular level, according to Scripps Institution of Oceanography Professor Peter J. Franks, who calls the phytoplankton “my favorite dinoflagellate.”

“Why favorite?” Franks wrote in an email Q&A posted on the blog Deep-Sea News. “Because it’s intensely bioluminescent. When jostled, each organism will give off a flash of blue light created by a chemical reaction within the cell. When billions and billions of cells are jostled -- say, by a breaking wave -- you get a seriously spectacular flash of light.”

Though it is hard to predict how long it will last, experts say it could stick around for several more weeks or months.

The algae produces a mild toxin that can accumulate in some sea creatures, but it is not harmful to people. It is safe to swim in too, UC San Diego experts said, though increased ear and sinus infections have been reported during blooms.

The striking surf has awed nighttime visitors to the San Diego-area shoreline, who have shared photographic evidence widely online.

The glowing images have lit up blogs and social networks, awing observers like Kevin Baird, who posted a photo of the bioluminescent surf on his Twitter feed, likening it to “SpongeBob's aurora borealis.”

“How do i recreate that in my reef tank?” Jeremy von Kuster wondered after watching the red tide Wednesday night at Torrey Pines.

Any sort of fast motion can agitate the plankton--breaking waves, swimming fish and even footprints in the wet sand. For an eerie experiment, try capturing some ocean water in a bottle and shaking it to generate a vivid glow.

One family at Tamarack Beach in Carlsbad was collecting the seawater in bottles to generate just that effect, the North County Times described: "If you dump the bottles in the toilet and turn off the lights, it will light up the whole bowl,” Duane Collings, of Oceanside, told the newspaper. “It's a trip.”

--Tony Barboza

Photo: A visitor near the pier in Oceanside, Calif.,  watches flashes of neon blue in the crashing waves. Credit: Don Bartletti / Los Angeles Times