JAUNTS : Glittering Shoreline Is Really Visit by Red Tide : Heavy rains, runoff have triggered one of the longest-lasting buildups of microscopic organisms to visit the coast in years.

If you go to the beach after dark these days, you’ll see a dazzling light show as the surf breaks on shore in a burst of sparkling glitter.

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The phenomenon is called red tide. It’s caused by a massive buildup of microscopic organisms in the plankton, turning the water a murky brown by day but producing a stunning, bioluminescence at night.

“At night, the waves give off a bluish light as they break on the shore--and (if you kick) the wet sand, (you) can send ‘sparks’ flying,” said Dan Richards, a marine biologist at the Channel Islands National Park visitor center.

Red tides usually occur briefly during the summer. But heavy rains and runoff have triggered one of the largest and longest-lasting red tides to visit the Southern California coast in years.

“This is the most I’ve ever seen,” Richards said. “It’s pretty incredible.”

This year’s red tide has been spotted from Point Conception to San Diego. No one knows how long it will stick around.

“As long as we have rain bringing the nutrients into the water, there’s a pretty good chance of it,” said Gary Davis, a marine biologist for the National Biological Service at the visitor center.

Despite the intensity of the current red tide, seeing it after dark is not a sure thing along the county coastline. Davis suggested trying the Ventura River north to Summerland. But he has also seen some “really nice patches” down the coast from Ventura.

“It’s kind of like grunion; it’s very hard to predict where” it will show up, he said.

When you see the breaking surf sparkle or a boat wake glitter, you’ll know it’s the red tide. Put some water in a jar, shake it up and you’ll see sparks.

Fish spotters flying over the water use the bioluminescence to direct boats to schools of mackerel. “I’ve even witnessed pelicans feeding on anchovies at night guided by the luminescence,” Richards said.

Red tides are nothing new. The Bible mentions the River Nile turning blood red, and Homer’s “Iliad” notes similar phenomena.

The tides can be found in many parts of the world. The color of the water ranges from yellow to brown to deep red, depending on the density of the single-cell organisms--called dinoflagellates--in the plankton.

Why the bluish sparkle to the water at night? It happens when the water is disturbed, such as a wave breaking. A chemical reaction in each cell probably produces a tiny bit of light, which becomes visible when the organisms multiply by the millions, scientists say.

During the day, the murky water is a turnoff to surfers but generally not harmful. “It should be of no concern to surfers,” Davis said.

But fish sometimes die during red tides because the microscopic organisms deplete the oxygen in the water. Some red tides have been associated with shellfish poisoning, but the current tides in this area are considered nontoxic, scientists say.

But they can set off sparks.

Jane Hulse, who spends as much time as possible out of doors, is a regular contributor to Ventura County Life. If you have any outdoor recreational news, send it to her at Ventura County Life, 5200 Valentine Road, Suite 140, Ventura 93003, or send faxes to 658-5576.