No one likes to arrive at the beach to find a layer of sea foam on the shoreline, in the waves, or further out behind the breakers – especially if it is a disconcerting brown or yellow colour! Foams, however, are global in their presence in the aquatic natural environment including on streams, rivers, lakes, and sea water. Each coastal region has slightly differing conditions determining the formation of sea foam, ocean foam, beach foam, or spume, regardless of what you call it, however, the general principle is the same. Like wanting to run a bubble bath, the formation of sea foam needs two things: the first is something to reduce the surface tension of the water, and the second is something to stir up and froth up the water. For your bubble bath these would be soap and running water, while for sea foam these would be dissolved organic matter (usually) and strong surface winds or waves breaking on the beach.
Sea water contains a whole variety of items including dissolved salts, proteins, fats, dead algae, pollutants, as well as other organic and artificial matter which comes from phytoplankton blooms, seaweed or even terrestrial plants. Some of these are natural detergent-like compounds that collect in the surface microlayer. It is these compounds that reduce the water’s surface tension, and when the water is stirred up form persistent bubbles. These bubbles can be foamy, slimy, oily, and a can be a variety of colours, with a variety of smells! Consistency, colour, and smell can be attributed to what compounds are in the water forming the foam, though sometimes colour can be due to sand, dust and dirt particles that get trapped within the foam.
Although it may look unpleasant, most sea foam is not harmful to humans, and is in fact a sign of a natural and productive marine ecosystem. However, there are rare occasions when sea foam can have harmful effects on both humans and the environment, such as when harmful algal blooms (such as red tide) occur and decay near shore, or when the sea foam concentrates pesticides and natural toxins.
Written by: Minke Witteveen
For further reading:
- Elert, E. 2012. FYI: What is sea foam? Where does it come from? And is it dangerous? Accessed: 2016-08-28. URL: popsci.com/science/article/2012-11/fyi-what-causes-sea-foam-and-it-dangerous
- National Ocean Service. 2016. What is sea foam? Accessed: 2016-08-28. URL: http://oceanservice.noaa.gov/facts/seafoam.html
- Schilling, K. and Zessner, M. 2011. Foam in the aquatic environment. Water Research 45: 4355-4366.