Sea Foam: The Natural Phenomenon Behind Britain's Coastal Foam

AI Summary

Sea foam appearing around Britain's coast is a natural phenomenon caused by algae blooms and weather conditions, not pollution. This harmless foam, primarily from phaeocystis algae, forms through wave action and wind patterns, creating distinctive patterns along shorelines.

The Lead

At this time of year a sinister-looking substance can often be sighted around Britain's coast: a frothy foam piled up along the shoreline or appearing in long ribbons offshore. People sometimes assume this foam is the result of pollution or sewage dumping. In fact it is a common natural phenomenon produced by a combination of algae and weather.

The Science Behind Sea Foam

Sea algae start to grow in April as conditions warm. The most common sort, phaeocystis, is not toxic and forms part of the marine food chain. When the algal bloom dies it leaves a brown scum of organic material with surfactant properties, which, like soap, lowers the surface tension of the water.

Formation of Coastal Foam

These natural surfactants create foam when the water is disturbed. Breaking waves churn up the water and produce yellowish-brown foam along the shoreline. This may be so abundant that fragments blow about like thistledown.

Wind Patterns and Foam Lines

Wind blowing over the sea creates rotating horizontal cylinders of water, like submerged rolling pins. These rotating currents, known as Langmuir circulation, push water downward at one point and up in another. Sea foam gathers in long parallel lines in the calm sections, known as windrows, foam lines, or drift lines.

Understanding the Appearance and Smell

Sea foam may look unnatural, as well as unsightly, and it sometimes smells foul. But it is generally natural and harmless.