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The glittering light seen in seawater at night can be attributed to bioluminescence, a handy evolutionary phenomenon that gives certain land and sea creatures the ability to glow in the dark. Why do some organisms glow? We fished around the Yahoo! Bioluminescence category to shed some light on this creature feature. We learned that scientists believe the ability to glow probably originated in ocean organisms and was
used for the following: - Finding or attracting prey -- Just like the glow-in-the-dark bait used by fishermen at night, bioluminescent organisms use their eerie light to attract prey in the dark waters of the ocean.
- Defense against predators -- The ability to glow can be used as a clever decoy. Some squid and shrimp produce a glowing cloud at night, allowing them to escape attack. Plankton use flashes of light to startle their predators.
- Communication -- Some animals, such as fireflies or polychates (bristle worms), use bioluminensce for mating purposes. The males attract females with flashy light shows.
Another purpose of bioluminescence is simply to provide light. Since most of
the Earth's oceans are pitch black at night, tiny plants like these dinoflagellates help provide the primary source of light in the waters. These may be the source of the ethereal glow you witnessed. Other bioluminescent ocean organisms range from bacteria to fungi to some fish and even a few sharks. So now you're wondering how do these creatures glow? An organic molecule called luciferin produces light, while an enzyme named luciferase acts as the catalyst that causes oxidation. The resulting oxyluciferin is the light you see. The blue wavelength transmits farthest in water, and most organisms don't absorb longer or shorter wavelengths, so the majority of
bioluminescent sea creatures emit the blue-green hue you describe. There are exceptions, however. For example, fish in the Malacosteid (loosejaw) family emit red light as a cunning predatory feature. Most marine creatures can't see the red light, so the wily fish can use this light to sneak up on their prey. To learn more about bioluminescence, check out this enlightening FAQ on the matter.
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