If you have been on a beach at night this summer, you may have observed a fascinating phenomenon: As the waves break, the dark water suddenly lights up in a blue or blue-green glow. In Danish, this is called and it’s a mesmerising example of bioluminescence that appears along Denmark’s coasts. But why does it happen and where can you see the glowing waves yourself? The reason for the seemingly magical phenomenon has less to do with magic and more to do with a specific kind of algae – more precisely, tiny spherical organisms called Even though, it is not the only kind of algae that can produce light, it is the most common type in Denmark and the rest of the northern European, explains Catharina Cecilie Marcussen, of the Øresundsakvariet (Øresund Aquarium).
The Øresundsakvariet is a smaller saltwater aquarium and part of the Department of Biology at the University of Copenhagen. If the algae are disturbed, for example when a wave breaks or someone swims in it, they start to glow. The light is created by chemical reaction between a substance called luciferin, the enzyme luciferase and oxygen.
This process is called bioluminescence, which describes the production and emission of light by living organisms. The produced light is also a so called “cold light”, because the process generates almost no heat. Algae aren’t the only organisms that can produce light, bioluminescence occurs widely among animals and plants.
A popular animal that uses bioluminescence is the fir.