Weather Words: Seafoam

Have you ever visited the beach only to be greeted by a thick, foamlike substance washing ashore? That's seafoam.

Seafoam is a frothy layer of bubbles that forms on the ocean’s surface when dissolved organic matter — like algae, plankton and decaying plants — gets churned up by wind and waves. When the ocean is agitated, these natural compounds act as surfactants, lowering the surface tension of the water and allowing bubbles to form and persist. The more organic material in the water, the thicker and more stable the foam can become, sometimes blowing onto beaches in large, fluffy drifts that look almost like snow.

While seafoam is a natural occurrence, it can also signal changing environmental conditions. During algal blooms, for instance, the decomposition of large amounts of phytoplankton can create excess organic material that leads to unusually dense or discolored foam. In some cases, if harmful algae are involved, the foam can contain toxins that irritate skin or harm marine life. More often, though, it’s a harmless byproduct of ocean life and energy.

Jennifer Gray is a weather and climate writer for weather.com. She has been covering some of the world's biggest weather and climate stories for the last two decades.