Weather Watch

El Niño waves churn up sea foam along the SLO County coast

A swath of foam churned up by big waves coats the wet sand and a couple of border collies at Avila Beach.
A swath of foam churned up by big waves coats the wet sand and a couple of border collies at Avila Beach. The Tribune

Even though the Central Coast hasn’t received the amount of rain hoped for with this season’s very strong El Niño event, numerous Pacific storms have generated plenty of high-energy waves.

As most San Luis Obispo County surfers or fishers will tell you, this year has been one of the most energetic since the last very strong El Niño event in 1997-98. In fact, their observations are verified by the Diablo Canyon nuclear power plant’s waverider buoy database, which can be found at Scripps Institution of Oceanography at

As this year’s breakers lashed the shore, they have whipped up copious amounts of sea foam. Sea foam is common along the Central Coast, especially during high-wave events and periods of plankton blooms.

Irving Berlin wrote the lyric, “to the oceans white with foam,” in the patriotic song “God Bless America,” made famous by Kate Smith. Depending on the type of organic matter in the seawater, the foam can also take on a yellow-brownish hue.

Sea foam is formed by the agitation of seawater caused by crashing waves, especially when it contains large amounts of dissolved organic matter. Along the Central Coast, plankton blooms combined with decaying bits and pieces of red, green and brown algae can put a lot of dissolved organic material in the water column in the form of proteins and fats.

Like fluffy whipped egg whites, the proteins in the seawater become denatured — changed from their natural state — as they are churned by breaking waves in the surf zone.

As the large denatured protein molecules unfold in the churning seawater like origami flowers, the air-loving part of the proteins stick to the air bubbles. The air bubbles in the foam become more persistent through surface tension. This is how sea foam develops.

Because of the persistence and light weight of sea foam, it can easily be blown onshore by winds onto beachfront sidewalks and streets.

Overall, the majority of sea foam is not harmful to humans. In fact, it is often an indication of a healthy and productive ocean ecosystem.

However, when sea foam is made from a harmful algal bloom such as dinoflagellates (red tide), the aerosols from its popping sea foam bubbles can pose a health risk for those with asthma or other respiratory conditions. It can also irritate the eyes of beachgoers.

If sewage, detergents or oils from polluted stormwater are present, the resulting sea foam can be more persistent. Sometimes when the conditions are just right, large amounts of sea foam can accumulate along the coast and conceal large rocks and voids, making hiking along the beaches hazardous.

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Join PG&E employees April 16 to celebrate Earth Day at Montaña de Oro State Park. The event is one of a number of service projects sponsored by PG&E and the California State Parks Foundation. Be sure to dress for outdoor work with long pants, long-sleeved shirt, sturdy shoes, hat, gloves and sunscreen. Snacks and a light lunch will be provided. Bring your own refillable water bottle. Rangers will provide tools and supervision. Please register at the California State Parks website:

John Lindsey’s column is special to The Tribune. He is PG&E’s Diablo Canyon marine meteorologist and a media relations representative. Email him at or follow him on Twitter @PGE_John.