Sea water isn’t pure like fresh water. It contains lots of tiny particles that, when agitated, create a soapy substance known as sea foam.
This natural phenomenon occurs throughout the world, although the circumstances that cause it form vary from region to region.
Sea foam is generally a sign of a healthy ocean but, in some circumstances, can endanger the lives of both sea birds and humans.
What is Sea Foam?
Sea water contains dissolved organic matter, including proteins, fats, dead algae, detergents, and various other organic material and artificial matter.
When the seawater is agitated by breaking waves and strong winds, these compounds act as foaming agents, also known as surfactants.
In turbulent conditions, these compounds trap air, forming sea foam bubbles that stick to one another “through surface tension.”
Natural detergents reduce the speed at which water drains from the bubble wall, making the bubbles more stable.
Ocean foam forms when water and air mix with a surfuctant. This sticky substance increases the surface tension, causing the bubbles to adhere to one another, creating a soap like foam.
What Causes Foam in the Ocean and Beaches?
Beach foam is a mechanical and chemical phenomenon caused by two factors – agitation of the water and high concentrations of organic matter.
If you fill a glass with sea water, you’ll see lots of tiny particles floating around. If you shake that ocean water vigorously, tiny bubbles will start to form on the surface.
In the ocean, this foam formation occurs on a much larger scale, especially when there is a combination of strong on shore winds and algae decay offshore.
Thick sea foams usually occur when harmful algal blooms decay near the shore.
The decomposing particles from the algal materials are washed onto the beach and churned by the waves. This biological debris reacts with the air and water, creating a thick sea foam.
Industrial waste, fertilizers, and even ocean sewage can also contribute to the formation of sea foam, by adding artificial surfactants to the ocean.
These pollutants stick to the surface of both air and water, creating a more stable and potentially toxic foam.
Is Sea Foam Dangerous?
Most sea foam is naturally occurring, completely harmless, and indicative of a productive ocean ecosystem.
However, when large harmful algal blooms decompose close to shore, there can negatively impact human health and the environment.
During an algal bloom, popping sea foam bubbles is one way the algal toxins are released into the air.
Once airborne, these toxins can irritate the eyes and lungs of beach goers, presenting a potential health risk, especially to those suffering from respiratory conditions such as asthma.
What Happens if you Eat Foam?
Sea foam looks extremely inviting – a bit like swimming in a pool full of marshmallows, but experts say you should avoid contact it, and definitely not attempt eating it.
Although sea foam is completely harmless, it probably won’t taste very nice, and certainly nowhere near as delectable as marshmallows!
I imagine it would be more like an extremely salty mousse with a sprinkling of sand and bacteria!
Some sea foams contain harmful toxins that would be potentially dangerous when ingested.
Not only can sea foams be contaminated by harmful algal blooms, but they can also contain sewage and other pollutants, especially after heavy rain or snow.
What Happens if you Swim in Sea Foam?
In some circumstances, it’s perfectly safe to swim in sea foam, but in others, it could prove life-threatening.
Swimming in a naturally occurring sea foam containing dissolved salt, proteins and other organic matter shouldn’t present any immediate health risks.
Where the sea foam is particularly thick or contaimated by harmful algal blooms, it can be potentially dangerous.
On the Gulf Coast beaches, blooms of Karenia brevis contaminate the sea foam, causing potential respiratory problems for those that attempt to swim in it.
In extreme conditions, strong winds and high waves cause such a thick sea foam to form that it creates a layer of gloop on the surface of the water that makes swimming extremely dangerous.
In 2020, five experienced surfers lost their lives off the coast of Scheveningen district of The Hague in the Netherlands.
The surfers headed out into a churning sea thick with foam and “vanished under a “man-sized” layer of sea foam.”
The foam made it almost impossible for surfers to get back on their boards when they fell off.
According to local official Pat Smith, “They disappeared under the foam like it was some sort of avalanche.”
The “man-sized foam layer at sea and on the beach” also complicated the rescue operation, resulting in just one man being rescued.
Is Sea Foam Toxic or Dangerous to Sea Life?
Most sea occurring on the sea surface contains organic matter such as dissolved salts, proteins, and other biological debris.
As such, it’s completely harmless. When a decaying algal bloom contaminates the foam with surfactants or wetting agents, however, the results can be deadly.
In 2007, David Jessup from California’s Marine Wildlife Veterinary Care and Research Center collected the bodies of over 200 dead birds, along with “550 stranded and seriously ill individuals.”
The dead birds, which included grebes, loons, and fulmars had succumbed to fatal hypothermia caused by amino acids associated with algal blooms, also known as red tides.
These amino acids are “powerful surfactants” that caused the birds to lose their “repellent ability” and become water-logged.
A similar event occurred in the Pacific Northwest in 2009, killing thousands of seabirds and stripping many others of their waterproofing.
How can we Reduce the Amount of Foam in the Ocean?
Although sea foam is a natural phenomenon, human activities can amplify it, so by changing the way we live, we can reduce the amount of foam in the ocean.
Naturally, sea foam is most prevalent in areas where there are high concentrations of organic matter and algae in the water.
When “compounds produced from petroleum production and transport, synthetic surfactants, and pesticide use” are added, they accumulate on the sea surface microlayer, contributing to the formation of sea foam.
Researchers from the Vienna Institute of Technology suspect that algal blooms “gather strength from sewage and nutrient-dense runoff—and detergent or other chemicals in the water,” creating thicker, more toxic sea foams.
According to Matthew Reidenbach, an environmental scientist at the University of Virginia, “The surest way to prevent foam is to limit the sewage, detergents, and other anthropogenic runoff entering the water in the first place.”
Some believe that altering the pH of the ocean could reduce the amount of foam because “basic water is more prone to foaming than acidic water,” but Reidenbach says this “not feasible on a big scale.”
Ocean foam forms when waves and wind agitate sea water, activating the particles within it.
When air, water, and some kind of surfactant combine, they reduce surface tension, giving greater stability to the bubbles that form on the surface. This stability is what differentiates beach foam from sea spray.
This naturally occurring foam is completely harmless, but when algal blooms decay near to shore, they contaminate that foam with algal toxins that are potentially damaging to the environment and human health.
Very thick layers of sea foam can also be fatal, trapping swimmers and surfers underwater.
Some types of natural, organic sea foams are almost as dangerous as those contaminated with pesticides or ocean sewage, producing amino acids that strip sea birds of their natural waterproofing.
Although beach foam is a natural phenomenon, human activities can contribute to it, making it thicker and more dangerous.
Limiting the amount of waste we pump into the ocean could reduce the frequency of dangerous sea foam events, making our beaches and seas safer for everyone.
Nicky is a British adventurer and animal lover who spends her time exploring the natural world and writing about her experiences. Whether on horseback, underwater, running, hiking or just standing with a fishing rod in hand, she embraces everything her adopted home of South Africa has to offer.