Tuesday, June 21, 2005 | Beachgoers know of it as a “red tide,” but at La Jolla Shores on Monday, a concentration of non-toxic, single-celled organisms tinted the crowded waters a deep brown.

The organisms, called dinoflagellates, accumulate at unpredictable intervals according to water currents and weather patterns, said Peter Franks, a professor at Scripps Institution of Oceanography. Although the change in water color may seem strange, the cells are completely harmless, Franks said.

This year’s dominant species, the golden brown-colored Lingulodinium polyedrum, is also bioluminescent, giving off a blue flash when disturbed – which should make nighttime trips to the beach rather interesting for the next two weeks.

“Breaking waves, swimming fish, surfers, swimmers and kayakers will all be lit up with a blue glow at night. Even your footsteps will sparkle in the sand,” Franks said.

Franks believes the cells have been in the water since February, waiting for weather conditions to warm up in order to grow denser. Their concentrations are highest around noon, when weaker winds allow the organisms to congregate near the surface to carry out photosynthesis.

– IAN PORT, Voice Contributing Writer

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