A glowing sea
Q: This past Sunday [Sep. 4, 2005], my boyfriend and I were
at the end of a dock on Mission Bay in San Diego. When we stepped hard on the
dock, it made the fish jump. They looked like little glow sticks underwater! I
then stuck my foot in the water and moved it about. The water glowed green in
the direction of the movement. My boyfriend jumped in, moved his arms and legs,
and he looked like a glowing angel. It was the most amazing thing I have seen.
What caused this and why? We asked the hotel but they said they had never seen
anything like it. (Sarah, Birmingham, Michigan)
Little microscopic creatures (called Lingulodinium polyedrum) that glow
in the dark caused the alluring strange display that night.
Lingulodinium polyedrum, a well armored organism. Scanning electron
microscope image. [Courtesy of J.Woodland Hastings ©, used with permission]
The phenomenon you saw happened something like this. During
this past winter, the creatures ó single-celled algae that convert light to
chemical energy through photosynthesis, much like plants ó lived in modest
numbers about 30 feet (10 m) below the surface. They rose to the surface daily,
captured the Sunís energy, and sunk at night to the 30-foot depth. But then,
perhaps in February, they sensed conditions were ripe for growth. We do not know
what triggers the change. We cannot predict when it will happen. We do not
understand what motivates these creatures.
Slowly, over the next few months, the population grew. Most
individuals split to create two where one formerly existed. A few mated by two
cells fusing together to form a fertilized ovum and then later dividing to
reproduce. The population surged ("bloomed" as the biologists say) reaching, by
June, up to hundreds or thousands of L. polyedrum cells in each
milliliter of seawater. The population increased by a factor of about 250.
As the sea warmed with warm summer days, the organisms
ascended to form a dense layer near the surface. Millions of cells swam in the
dock waters by the time you arrived in September. A single teaspoon contained
Letís zoom in on one of these golden-brown creatures ó one
that is approximately the size of a
(50 microns) and covered with a sheath of cellulose plates. It looks like a
porous armor-plated soccer ball and is a species of dinoflagellates. See figure
That September night, this fellow ó flailing his two flagella
(whip-like appendages) in a counterclockwise direction ó swam near the dock.
It knew it was night and controls its luminescence through a
24-hour day-night rhythm. The one-celled creature tells time and was ready to
foot plopped in beside it (and a few million of its close friends), roiling the
waters. The tiny L. polyedrum glowed a blue light as they always do when
disturbed. See figure. Thatís the light you saw. They flash when a predator
touches them. Moreover, they emit blue light ó a color that can be seen farther
than most other colors underwater.
The bluish halo around the organisms in this fantastic
image is similar to the glow they create through bioluminescence. Hastings,
however, generated the imaged glow by shining a light on the creatures
(luminescence). [Courtesy of J.Woodland Hastings ©, used with permission]
Why? Presumably as a burglar alarm to either warn away
predators (for example, shrimp) or to attract visual predators (for instance,
fish) to eat the shrimp that are eating them, says
Peter JS Franks, professor of biological oceanography at Scripps Institution
"Bioluminescence may be thought of as a bag of tricks..." says
Woodland Hastings, a Paul C. Mangelsdorf , Professor of Natural Sciences at
Harvard University. Different creatures use it in different ways for different
defense, like the dinoflagellatesí burglar alarm
communication, like firefly courtship and mating
offence, like flashlight fish luring of prey
The L. polyedrum species create a cold chemical light
in a manner similar to how fireflies generate light but with notable
"The phenomenon is not only rare: in the different groups that
do emit light, the biochemical and physiological mechanisms responsible for it
are very different...," says Hastings.
Most bioluminescent creatures make light by combining oxygen
with two important chemicals:
- Luciferin, a water-soluble pigment, which is present in the
cells of all organisms that make light. In dinoflagellates, itís related to
- Luciferase, which starts the chemicals combining and
increases the speed with which they combine; it's an enzyme that acts as a
The luciferin and luciferase chemicals, however, are
chemically different among the various creatures, since the different organisms
evolved their ability to create light separately and at different times.
Initially, luciferin reacts with specie-dependent chemicals
and oxygen to form intermediate luciferase-bound peroxides that break down to
give a product in an excited state ó an extremely high-energy, unstable
chemical. The new chemical does not last long but falls to a lower-energy state,
and emits light.
Bioluminescence is a "curiosity of nature", involving genes
and proteins that are mostly unrelated. "How many times this [bioluminescence]
may have occurred is difficult to say, but it has been estimated that
present-day luminous organisms come from as many as 30 different evolutionarily
distinct organisms," says Hastings.
Only some dinoflagellates (like our lambent friend, L.
polyedrum), bacteria, mushrooms, cnidaria (jellyfish), annelids
(earthworms), mollusks, crustacea (shrimp), insects, and fish can luminesce.
Bioluminescence occurs mainly among marine life. We donít know why. Moreover, at
midocean depths (200 to 1200 m) over 95% of individual fish, shrimp, and squid
Mammals, birds, reptiles, amphibians, and true plants lack the
Scripps Institution of Oceanography:
Patterns in dense
phytoplankton blooms by Peter Franks
Research by J. Woodland Hastings
Hastings, J.W. (1998) Bioluminescence. (N. Sperelakis, ed.),
In: Cell Physiology, 2nd Edition, Academic Press, NY., pp.984-1000.
Hastings, J. W., Liu, L., and Schultz, W. (2005) Dinoflagellate Bioluminescence
and its Circadian Regulation In, Bioluminescence (John Lee, Editor), The
Digital Photobiology Compendium (Dennis P. Valenzeno, Editor), click "Preview
Modules" then "Bioluminescence: Ocean"
University of Liverpool:
Lingulodinium polyedrum (Stein) Dodge, 1989
for biological timing
University of Calgary:
Dinoflagellates by Andrew MacRae
bioluminescence web page
Seaís eerie glow seen from space
(Answered Nov. 22, 2005)