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VelVet elVis:
PhotograPhing Fluorescence underwater
TexT and PhoTos by eThan daniels
Warm liquid shadows enveloped me as I descended into a dark
void along one of Buyat Bay’s many reefs. This was not to be a
typical Indonesian night dive. My dive buddy, marine biologist
Geoff Cook, flipped on his torch to reveal a slope of hard and
soft coral colonies with polyps extended to feed on nocturnal
plankton. A moment later, we both slipped orange shades over
our masks. Then, positioning a filter over the torch’s bright
white beam, Cook adapted the lighting to reveal previously
invisible fluorescent emissions from reef creatures. Voila!
The world in front of us became intensely different and alien.
Amid the inky darkness, various hues of neon yellows, greens,
oranges and reds glowed under the deep blue wavelengths of
light emanating from Cook’s torch. The scene’s colors faintly
reminded me of a very hip velvet Elvis painting that used to
adorn my college apartment’s wall, surreally glowing under
ultraviolet light.
Reef fluorescence occurs when short wavelengths of
light — i.e., blues — are absorbed by marine animals and
re-emitted at longer wavelengths — greens, yellows or
reds. So, in essence, the animals are not reflecting light, as
is normal, but producing it. Fluorescence may play more
of a role in color underwater than in terrestrial ecosystems
because the spectrum of emitted light contrasts with the
predominantly blue wavelengths that reach deepest in water.
During the day, fluorescence occurs but is overwhelmed
by ambient sunlight. Once the sun goes down, however,
organisms’ fluorescent proteins can be “excited” by shining
an intense ultraviolet, blue or green light on them. To capture
the otherworldly colors radiating from the surrounding reef,
I used specially designed excitation filters manufactured by
NightSea Inc. The filters were strapped onto the front of my
two strobes to convert white light into the blue light that
stimulates fluorescence. I used an orange filter on the front
of my macro lens to block the reflected blue excitation light,
allowing only the longer wavelengths of the fluorescence to
reach the camera’s sensor.
Fluorescence is never bright in comparison to ambient
light, even at night, so moving slowly and swimming close to
the reef was essential for finding appropriate subjects. Since
the light transmitting through the barrier filter was rather
weak, I varied the camera’s ISO quite a bit, shooting most
images at approximately 1/60 sec, f/5.6 and between 400
and 3200 ISO. My strobes, set on full power, were placed
very near the subjects, providing as much excitation light as
possible. I found out while experimenting with fluorescence
photography that if an organism does not contain
fluorescent proteins it will not produce any light no matter
how close or powerful the strobes!
Cook and I hovered near the reef and began to gaze more
closely into the shadows, distinguishing tiny organisms
that we never imagined would have fluorescent pigments.
I stared at the intricate polyps of a soft coral colony that
radiated a faint green. Between the polyps were tiny red
fragments swaying back and forth in the gentle current.
Bringing my mask within centimeters of the colony, I
identified the red bits as skeleton shrimp, each no longer
than a few millimeters. These planktivorous amphipods
looked like predatory extraterrestrials inexplicably bathed in
vibrant red fluorescence.
Scientists from the University of Tübingen in Germany
recently speculated fluorescence in fish may be used for
communication or to attract other fish. Might it also be a
type of camouflage for use against predators or prey that
can detect particular wavelengths of light? Whatever the
case, these colors and pigments must have some time-
proven evolutionary benefit since such a wide array of reef
organisms produces them. Sponges, cnidarians, annelids,
crustaceans, mollusks, echinoderms and even some sharks
have been shown to produce fluorescent emissions.
Photographing fluorescence underwater has opened a
universe of unanswered questions about the advantages it
confers on the variety of creatures that use it. As biologist
E.O. Wilson once intimated, the more that organisms
become better understood, the greater the value that will
be placed upon them
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