The Santa Ana winds that roared through Southern California, creating havoc for firefighters and downing trees and power poles, may also have brought an unexpected problem: water pollution.
High bacteria readings were reported at 14 sites along Orange County's coast from Laguna Beach to Huntington Beach. The pollutants may have been carried from distant inland farms and dairies to the coastal waters by the fierce winds, several experts said.
The spiked readings resulted in warnings to beach swimmers, divers and surfers. There were no beach closures.
County health officials said the findings are unusual because most of the sites, such as Bolsa Chica State Beach, are not near storm drains or creek mouths and there was no rain during the most recent testing period. Storm drains in particular are blamed for funneling pollutants into the ocean.
"One of the causes could be from the high winds that we had for the last few days," said Monica Mazur, a county environmental health division spokeswoman. "But that's only a guess, because there are no scientific studies to rely on."
Orange County has experienced bacteria spikes in the past after offshore winds, but not to this extent. High counts also occur when high surf and high tides combine to flood coastal areas and flush out pollutants, Mazur said.
In Los Angeles, similar bacteria counts failed to materialize, though a few beaches near stream and river mouths where contaminants are found were posted for elevated bacteria counts.
Richard Kebabjian, chief of the recreation health program in Los Angeles County, said he discounted the winds' effect and instead blamed the weekend's high surf and high tides. Sometimes an algae bloom can cause high bacteria readings, he said.
Pinpointing the cause of the elevated readings along the Orange County coast may be impossible. Such source tracking is expensive and currently unavailable at the county level, although several environmental laboratories are working on ways to track sources of pollution.
With gusts reaching more than 100 mph in some places, debris could have included fertilizer and animal waste from inland agricultural areas.
A UC Irvine professor who studies atmospheric physics said bacteria, like pollen, can hitch rides on dust particles from the desert and travel to the sea during large dust storms.
Charles Zender, a professor of earth system science, said that even though dust particles can be as small as one-fifth the width of a human hair, "there's plenty of room for hitchhikers."
Of the three bacteria indicators used in the recent water testing, only the enterococcus was high in recent samples, Mazur said. That indicates the bacteria were not from a fresh source because enterococcus, which comes from warm-blooded mammals and birds, lasts longer in the environment, she said.
Chad Nelsen, the Surfrider Foundation's environmental director, said he finds the wind theory plausible. "We've had dust storms in the Sahara Desert that blow across the Mediterranean Sea, so it's highly likely the Santa Anas were responsible," he said.
Large dust plumes that can carry pollutants often cover entire regions in other parts of the world, Zender said.
Along with thousands of others in Orange County, Zender said he saw a plume of dust coming from the San Gabriel Mountains toward the coast.
The National Aeronautics and Space Administration posted a photograph taken Monday from a satellite on its Web site -- http://naturalhazards.nasa.gov/ -- that showed dust and smoke being blown across California and into the Pacific from winds that raked the interior deserts and other dry areas.
Zender said earth system science helps explain how smoke and ash from volcanoes can cover the globe and how dust storms from Asia travel over the Pacific and can produce spectacular sunsets in California.