Sea foam is likely created by a combination of factors. Decaying organic matter such as fish, plant life and microscopic organisms, seaweed excretions, and other proteins, and in some cases pollutants, are all carried on tiny air bubbles whipped up by tidal movements. As currents reach the shore and a wave forms, the air bubbles well up to the surface sticking together. The wave crashes and the foam is delivered to shore.
The amount of foam created on a shore at any given time can vary as factors fluctuate. A phytoplankton bloom is microscopic algae that can reproduce so quickly when conditions are right, that the biomass can be seen from space. It can discolor seawater to a brown or reddish color, giving rise to the name, red tide, though scientists prefer “algae bloom” since the color varies and the bloom is unrelated to tidal movement. Harmful algae blooms will produce natural toxins and deplete dissolved oxygen levels in the area, triggering a sudden die-off of local marine life. The sudden increase in organic waste can contribute to greater amounts of sea foam.
Human products also contribute to sea foam, including run off from farms, factory waste and sewer spills. Foam resulting from pollutants is often brown, though foam caused by a red tide or other organic sources might also appear brownish. Generally, foam not created by pollutants or algae blooms is white.
In 2007, sea foam was linked to the deaths and stranding of hundreds of migrating seabirds on the Monterey Coast in California. Scientists were initially stumped when the birds were found coated with a yellowish greenish substance, matting the feathers. This caused the feathers to lose their insulating property, and 207 birds died from the cold sea while 550 others were stranded. Scientists eventually linked a recent nontoxic algae bloom that had resulted in foam with the problematic residue on the birds.
Another quite different event also occurred in 2007. While most beachcombers experience sea foam as relatively small pockets of foamy bubbles, in some cases circumstances come together to form colossal amounts of the airy froth. In August of this year surfers on the water in Yamba, Australia just north of Sydney were in for a big surprise. A literal wall of sea foam came drifting in to envelop the beach. The foam dwarfed beachgoers, covering the shore, even pushing up on to nearby buildings including the lifeguard center. The bizarre scene, dubbed the “Cappuccino Coast,” was captured in photos so unbelievable that fact-finding websites were approached to determine their authenticity.