How do bioluminescent waves occur

In this new lesson of the Windy.app Meteorological Textbook (WMT) and newsletter for better weather forecasting you will learn more about bioluminescent wave and how it works.

Red tides or algal blooms

About one percent of the world’s biomass is phytoplankton — tiny algae that drift with currents through oceans, seas and other bodies of water and serve as food for aquatic creatures.

There’s more phytoplankton at ares where there are more nutrients in the water. When these nutrients are particularly abundant, phytoplankton grows so fast that it colors the surface layer of water — green or red-brown, depending on the main algal species.

When people notice red-brown water near shore, it is called the red tide, although a more correct term is algal bloom (because it has nothing to do with tides).

Red tides

The glow of the sea

In the daytime, the red tide does look red. But when it gets dark, the magic happens — the waves crashing on the shore begin to glow blue or bluish-green inside, and so bright that they attract Instagram users from all around.

The thing is that some phytoplankton species are bioluminescent — they have the ability to release light as a result of chemical reactions inside the creature.

Most often, the glow is due to the unicellular Noctiluca scintillans algae, which release light in response to external stimuli — in this case to the coastal waves throwing them from side to side. Currents, surfs, ships and even ordinary fish can also make them glow.

The glow can also be observed far away from shore — this is due to bacteria that emit light without any irritants. This glow is also called the milky sea.

The glow of the sea

The danger of red tides

Ships and fish moving through Noctiluca scintillans will leave a beautiful glowing trail. The same will happen to someone who decides to swim there — all his movements in the water will be accompanied by a bluish aura.

Although it is safe for most people to swim in the red tide, in some cases algae can cause skin irritation and burning in the eyes — then you should immediately return to the shore and wash your skin and eyes.

Red tides are particularly harmful not to people, but to marine ecosystems. The phytoplankton layer can sometimes be thick enough to deprive oxygen and kill species that live deeper. Dead fish can be washed ashore for up to two weeks after and the accompanying bacteria can already seriously harm people — swimming around dead fish is not smart.

Toxins (including paralysing) released from algae often accumulate in shellfish — oysters and mussels — it is better not to catch or eat those after a red tide.

Although this is a natural phenomenon (nutrients can be raised from the bottom by an ordinary storm), sufficient evidence indicates that blooms can also be caused by garbage that creates a nutrient environment for the algae in coastal waters. Therefore, no matter how beautiful red tides and the night glow of the water are, one should remember that for many marine species they turn into an ecological disaster that may well be a consequence of human activity.

Text: Windy.app team

Cover photo: Unsplash