What the Heck Is Sea Foam?

Last night, meteorologist Tucker Barnes, from Washington D.C.’s WTTG-TV, was reporting live on Hurricane Irene from Ocean City, Maryland. As the night wore on, Barnes found himself buried in more and more sea foam blowing in from the beach. And Barnes admitted that he had no idea just what he was standing knee-deep in. (“It’s in my face. As you can imagine, it doesn’t taste great.”)

Besides an engine treatment and a blue-green color popular on Fender guitars, what is sea foam, anyway?

I’ve been waiting almost five years to give this answer to a question on the site, and today is my day: It’s just a bunch of random junk.

I’m mostly serious, too. Dissolved organic matter, like protein, fats and a grab bag of other stuff, is constantly being released by sources like dead fish, seaweed and algal blooms, and it's floating around in the ocean. Tides pull some of this stuff in closer to shoreline and as waves break, they churn seawater, air and all this organic matter together likes the world’s grossest milkshake.

The air and the foaming properties of some of the organic compounds help the mixture form bubbles that stick to each other. When waves hit the shore, the foam is often left behind on the beach, and can then be blown around by the wind.

In hurricane conditions like we had last night, water in the ocean is more agitated, leading to an excess of sandy foam, and strong winds are able to carry the foam farther in from the shore. In these conditions, polluted water and sewage from flooded rivers, drainage systems and streets can also make its way to the ocean, creating sea foam with strange colors, odors and various contaminants. Given the conditions last night and the foam’s color, this extra nasty version was probably what Barnes was wading through on the boardwalk.

A Seasonal Delicacy

While sea foam is pretty gross even under normal conditions, it’s an important part of the coastal food web and acts a reservoir of recycled nutrients for some beach-dwelling animals. The menu even changes depending on the season. Researchers studying sea foam in South Carolina in the late 1980s discovered that the foam is composed mostly of macroalgae (seaweeds) in the fall, winter and early spring, and mostly phytoplankton (microscopic plant-like organisms) in the late spring and summer.