Culture of bioluminescent plankton glowing bright blue as it is bubbled into a flask. This plankton is the tropical marine dinoflagellate Pyrocystis noctiluca. It forms huge swarms in warm seas, photosynthesising during the day. At night the swarms produce light when disturbed, through a chemical reaction involving a luciferin molecule being oxidised by a luciferase enzyme. P. noctiluca produces its luciferin from its chlorophyll. As seen here, it only glows when disturbed: during the bubbling it glows brightly, but as soon as this stops it turns off. This is thought to have evolved as a defensive measure. Some small predators will not eat glowing plankton, as it shines through their transparent bodies and makes them more visible to predators. In addition to this, by revealing the wakes of larger predators, the glowing plankton highlights its predators' positions to their own predators. Cultured at the Culture Collection of Algae at the University of Cologne, Germany.