When Oceans Glow In The Dark

Oct 23, 2011 By Deepa Gopal
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For nearly 400 years, mariners have talked about oceans turning milky, blue or red as their ships sailed thought the waters of the Pacific or Indian Ocean. The phenomenon even appears in Jules Verne's "20,000 League Under the Sea"! Last month, surfers off the coast of California caught pictures of blue and red ocean waves. 

Scientists now know that these glows are caused by "bioluminescent" bacteria known as dinoflagellates. When billions of these creatures join together, the oceans may turn brown during the day, but they are a sight to behold at night time. 

What is bioluminescence?

Bioluminescence is the ability of a living organism to emit light. The most common color of bioluminescent light produced by marine organisms is blue, which is also the color that penetrates farthest through water. In "milky seas," this light appears white because the human eye cannot discriminate colors at night time. 

Scientists had not understood what exactly causes these bacteria to glow, until now. When there is any movement in the ocean water -- say a wave or a surfer swimming through the waters, the disturbance sends little electric pulses through the cells of the bacteria. This causes the release of luciferase, a protein in the cells, that produces light. 

Are there other such glowing creatures?

Many of you may have seen fireflies or glow worms at night. However, most bioluminescent creatures live in the oceans, in the poorly lit twilight zone. In some parts of the ocean, these glowing creatures are the only source of light.

Why do these creatures glow? It may be to find food, find a mate, attract prey, communicate or as a self defense. One theory suggests that when small fishes eat a bioluminescent plankton, it emits a light to attract larger fish that might prey on the smaller fishes!

Researchers have been exploiting the fluorescent nature of the bacteria to develop living ink -- a way to encode secret messages and for anti-counterfeiting. Simple messages can be encoded by genetically engineering bacteria to produce different fluorescent colored proteins, which can then be observed under the correct wavelength of light. 

Here is a wonderful video on some amazing deep-sea creatures that exhibit bioluminescence.