26 June 2010

RANDOM EXCERPT: BIOLUMINESCENCE

Photo by Phil Hart. And, by the way, well worth a visit to his website for his explanation of the complex factors that led to this photograph. Plus more really beautiful images of bioluminescence.
I wrote about bioluminescence, the brilliant aurora stirred by motion in the nighttime sea, in THE FRAGILE EDGE. Here's an excerpt:
The light show we observe near the surface, at least as we understand it, is produced largely by the dinoflagellates—those unicellular plants possessing microscopic whiplike tails that enable them to move, however slightly, this way and that. Large creatures such as you or me or a spinner dolphin will activate billions of these bioluminescent plants as we move through the surface layer of the nighttime waters. Even small zooplankton, for instance, the predatory krill traveling on their swimmerets, will find themselves spotlighted.
As to why plants in the sea produce bioluminescence, a hypothesis known as the burglar alarm theory postulates that the chemical production of light acts as a visual siren: the plants turn on their lights when their predators (for example, krill) are in motion, illuminating them so that their predators (for example, lanternfish) can catch the krill and eat them first.
Tricksy.

You can read a classic science paper on the phenomenon: 
Mark V. Abrahams and Linda D. Townsend. Bioluminescence in Dinoflagellates: A Test of the Burglar Alarm Hypothesis (pdf). Ecology, Vol. 74, No. 1 (Jan., 1993), pp. 258-260

Photo from here.
More about bioluminescence from THE FRAGILE EDGE, an excerpt about sailing the Pacific one stormy winter:

In the trough between the swells, an incandescent waterfall of radiance tumbled from the wave breaking directly ahead. Time and again, we sailed into this cascade, which outlined the bow of the sailboat in a vibrating aura of electric blue and electric green. Behind us, our wake writhed like an aquamarine serpent before fading from view over the precipice of the receding wave.
Most nights schools of dolphins—generally common dolphins (Delphinus delphis)—arrived seemingly out of nowhere to ride our bow-wave. Alone on watch in the open-air cockpit, I would glimpse a streak of blueish-green heading towards the bow, looking for all the world like a torpedo until it porpoised through the surface to breathe. The first streak was invariably followed by others, sometimes dozens, all racing across the beam, carving glowing turns before settling into bow-riding position: on their sides, tail flukes nearly touching the bow as it hobby-horsed through the swells. No matter how violent the action of the bow, the dolphins held fast in their position, their bodies outlined in the pulsing blue light of an underwater St. Elmo’s fire. 
Common dolphins were not the only cetaceans we encountered in the course of these bioluminescent nights. We also came upon migrating gray whales headed for their breeding lagoons on the western coast of the Baja Peninsula. Their bioluminescent wakes mimicked the wakes of boats. If conditions were right, when the whales blew, the plugs of water covering their blowholes flared into faint, blue-green mists of luminous organisms, as if the behemoths were exhaling pixie dust.

Photo by Jed Sundwall, courtesy Wikimedia Commons.
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