Beach Walks with Dr. Joe Breezy Days and Sea Foam By Dr. Joe Richardson As we move into fall on Tybee, we will see an increase in breezy days when the wind is blowing onto the beach from offshore. On these days, we are likely to notice sea foam accumulating on the beach. When it happens, I’ll often get asked about all that foam, where does it come from, and what causes it. Since it is something a Tybee beachcomber is likely to see during this time of the year, I thought I’d write about it this month. First though, what it isn’t. Too often people assume that sea foam is the result of poor water quality in the inshore zone. Sea foam, like we see it, is not due to pollution. You might see pictures of polluted waters where detergents or other foam-producing substances have spilled into an area 26 TYBEE BEACHCOMBER | OCT 2017 and caused suds, bubbles and foam. But that is not the case or cause of our beach sea foam. Our shoreline sea foam is due to oil in the seawater. But hold on! It’s not petroleum or pollution-type oil. Instead it is more like vegetable oil. Lots of the microscopic algae, or phytoplankton that live in the inshore water, produce oil as their food and energy reserve inside their cells. There are benefits to this. Oil can store lots of chemical energy in a small space, so tiny oil droplets are a great way to store the excess energy the algal cells make when doing photosynthesis. Secondly, the tiny oil droplets inside help the algal cells to float or keep from sinking. And if you are a water-dwelling organism that depends on sunlight to make your own energy for survival, you need to be able to stay near the surface. So anything that helps you from sinking is a beneficial adaptation. Our coastal water has lots of phytoplankton in it. And with all these algal cells, there are also lots of microscopic animals, zooplankton, that eat the algae. In fact, the main reason our water is green and slightly cloudy, rather than crystal clear, is because we have so much plankton in it. These tiny, live particles make the water cloudy, but they also provide the basis of the food chain that so many of our bigger animals depend on. As the phytoplankton manufacture oil, they also leak it. When they die, they leak it. When they are eaten and their consumers die, they also leak it into the water. So this sort of “vegetable” oil is a natural component of sea water, especially in places like ours where the water is rich with these tiny algae. On days when the wind is blowing, stirring up the ocean and the waves are white-capping, the oils get worked toward the surface. If the wind is blowing from offshore toward the beach, this imperceptible film of oil gets constantly blown onto shore. As the film catches the blowing air, that oily film forms bubbles. And as the wind continues to blow, all those bubbles result in piles of foam that accumulates on the shoreline. So, on days when the wind is right, you might see sea foam. But remember, it’s not due to pollution, but rather is due to our plankton-rich, healthy sea water. Dr. Joe Richardson is a retired marine science professor with 35+ years of research and teaching experience along GA and the southeastern coast and Bahamas. Besides research, he conducts Tybee Beach Ecology Trips year round (www.TybeeBeachEcology.com) and frequently posts pictures of what they are finding on his Tybee Beach Ecology Trips Facebook page.
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