Reported July 2006

BACKGROUND: Scientists are now investigating the reason that the ocean sometimes lights up in the dead of night. This glow has mystified sailors for over 400 years. Scientists speculate that the bacterium Vibrio harveyi, a cousin of the microbe that causes cholera, is responsible for milky seas. They have recently been able to capture the first satellite images of a "milky sea." Thanks to satellite imagery, scientists can rush out to investigate these glowing patches of seawater that were previously thought to be just folklore.

WHAT IS BIOLUMINESCENCE? Bioluminescence is the ability of a living organism to emit light. In bioluminescence a chemical reaction triggers an electron to jump to a higher level. Then the electron loses energy and falls back to a lower level, emitting the excess energy in the form of a particle of light. No energy is lost as heat, as in other means of light production, so bioluminescence is often called "cold 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 rods in the human eye (used for night vision) don't discriminate color.

GLOWING BACTERIA: Dinoflagellates are organisms that cause red tides, flashing waves, and the sparkling waves behind boats as they churn through the water, but these organisms must be physically stimulated to produce those brief bright flashes. In contrast, V. harveyi will glow with a continuous light on their own under the right conditions. Those conditions include very high concentrations of the bacterial in order to accumulate enough of the trace chemical that induces this light production. A conservative estimate calls for 40 billion trillion bacteria packed into a space the size of Hawaii. This is equivalent to the number of grains of sand it would take to cover the entire earth with a layer 10 centimeters thick.

The American Society for Microbiology contributed to the information contained in the TV portion of this report.

If you would like more information, please contact:

Naval Research Laboratory: Marine Meteorology Division
Satellite Meteorological Applications Section
(831) 656-4721

American Society for Microbiology
Washington, D.C. 20036-2904
(202) 737-3600
http://www.asm.org

FACTOID...

In Jules Verne's 1870 novel "Twenty Thousand Leagues Under the Sea," the submarine Nautilus at one point traveled through a milky sea. The scene was most likely based on a real report from 19th century sailors.

ON THE WEB...

Milky Seas from Space