Cream with your Coffee – What Causes Beach Foam

Now that is a strange title I hear you say. Cream with your Coffee is a wee joke we have for whenever we see the beach foam – seriously looks like you could scoop some up and add it to your cuppa. All jokes aside though it is really interesting to know what actually causes that “cream”. In this blog I’m going to explain to you the science behind the beach foam you see washed up on the beach during a stormy sea.

When we see the beach foam many of us automatically think of it as pollution – the rough seas grabbing all the scum in the ocean and then dumping it on the beach. Previously that is what I’d always thought, and walking through it, well that was a definite “oohh yuk! moment” . If you thought that too well we were wrong (*) – it is far from pollution and in fact generally only occurs on clean beaches. I know, clean beaches and New Zealand is renowned as having some of the cleanest beaches in the world – hence why we see all this “sea scum”.

Turns out beach foam in NZ generally has nothing to do with pollution. It is actually a natural phenomenon, a natural product of one of the world’s purest and most natural landscapes, drawn from both land and sea and associated with many of the NZ surf beaches and the tiny organisms that live there.

David Bellamy’s “Moa’s Ark the Voyage of New Zealand” sums it up best.

“From the land comes a solution of history, natural chemicals dissolved from the forest soil and made of the remains of mosses, tree ferns, podocarps and flowering plants.  This gold-tinted tincture of natural history then mixes and mingles with the abundant slippums that protect the kelp and other seaweeds from abrasion, to produce this natural detergent-like complex which is then beaten into foam and what we see on our beaches.”

Like all detergents, it picks up and holds all manner of things including not only plants and animal plankton – all of which are far too small to see with the naked eye, but also tiny bits of debris and fine silt.  National Institute of Water and Atmospheric Research marine ecologist and plankton specialist Janet Bradford describes the foam being made up of smashed up cells of phytoplankton, single-celled algae and the nutrients they release when pounded by waves on these surf beaches.  Janet says high energy surf beaches have their own special ecosystem dominated by diatoms, some of which live only in this environment.  Diatoms can look brown or even like black oil – hence the colour of the foam, making it look like a form of pollution.

The major driving force behind the whole process is wave action.  Waves pump water through the sand thus releasing nitrates and other nutrients.  Waves also set up certain circulation patterns in the water that trap these nutrients in the surf zone.  Wave action not only smashes up the diatoms and other phytoplankton that make up the bloom, but also pulls in air bubbles to produce foam.  This foam is typical of exposed sandy beaches, particularly West Coast beaches of New Zealand.

The wonderment of nature – rather than being inhospitable places to live, NZ beaches that are constantly pounded by waves are actually full of life and beach foam is not a sign of pollution but in fact the outward sign of their enormous productivity.

Another reason the West Coast has to be one of the best places in the world to visit – it is just a bonus that we live here!

Jan  and Stephen run Breakers Boutique Accommodation on the Punakaiki Coastline – north of Greymouth and is based overlooking the Nine Mile Beach – one of the great surf beaches on the West Coast and a great location for beach foam.

*Disclaimer Not all beach foam is harmless, unfortunately in some parts of the world due to human activities there is an element of toxic pollution included.