Have you ever looked out on the water at night and observed the water glowing? The glow is generally shades of blues or greens. It seems to occur when the water is disturbed by anything from a moving fish to a paddle swept through the water. Many people have observed this spectacular sight and they often have questions.
What’s causing this glow?
The glow is caused by bioluminescent (say “bye-oh-loom-in-ESS-ent”) plants and animals. Bioluminescence is the term used to describe light produced by living things. In our area, the glowing light is most often the result of bioluminescent dinoflagellates (say “die-no-FLAJ-uh-lets”), which are tiny drifting algae-like organisms. But many organisms produce a similar glow, including small single-celled bacteria and larger animals such as comb jellies.
What causes these organisms to glow?
Plants and animals that bioluminesce possess light-producing organs that emit light through a chemical reaction. This chemical reaction involves a light producing protein called luciferin (say “loo-SIFF-er-in”). Luciferins store energy. The energy is released in the form of photons, or light, by enzymes called luciferases.
Why do organisms glow?
Some organisms glow to attract a mate, as is the case in fireflies. Others glow to attract prey. An example of this would be the deepwater anglerfish, which dangles its glowing lure to attract potential prey. Others glow to evade predators. The thought is that when light is shined on a predator, it may worry so much about being eaten itself that it avoids the glowing prey.
Are there other ways in which organisms glow?
Although most glows in the water are the result of bioluminescence, some organisms have the ability to fluoresce.
Fluorescence is similar to bioluminescence, but the trigger is changed. Instead of luciferin and luciferase, fluorescence is triggered when a pigment absorbs light from an outside source. Fluorescence is able to produce the widest spectrum of colors, but the light produced is only visible while the trigger is present.
Phosphorescence (say “fos-four-ESS-ense”) is similar to fluorescence except that it is more stable, so the glow will last after the trigger has been removed. Glow-in-the-dark stickers phosphoresce.
So it’s not phosphorus in the water?
Sometimes people get words confused. In this case, phosphorescence and phosphorus sound similar, and people are more familiar with phosphorus. But our nocturnal glowing water has nothing to do with phosphorus or phosphate pollution. Bioluminescent organisms are a natural part of a healthy marine ecosystem.
Betty Staugler is the Charlotte County extension agent for the Florida Sea Grant Program. Contact her at firstname.lastname@example.org or 941-764-4346.