It has been known for some time that some shallow-water corals use fluorescence as a protective mechanism:
...the pink and purple fluorescence in shallow waters act as a kind of
sunscreen. The fluorescent pigments absorb damaging wavelengths of light
and emit it as pink or purple light, protecting the single-celled
organisms called zooxanthellae that live symbiotically inside coral.
Zooxanthellae are photosynthetic and they provide the coral with food in
exchange for shelter.
But now the phenomenon has been observed in coral at low-light depths:
Coral may be converting blue light into orange-red light that penetrates
deeper into the coral tissue, where photosynthetic zooxanthellae live.
Fluorescence, by definition, is the absorption of light in one color and
the emission in another... Blue light may be good at penetrating water and for photosynthesis, but
it doesn’t penetrate the coral’s tissues well. And zooxanthellae can
live deep inside coral...
Mikhail Matz,
a coral scientist at the University of Texas at Austin, says he’s not
yet convinced this completely explains the function of the fluorescent
pigment in deep water corals. As humans with eyes, we tend focus on the
light coming from these coral. But maybe the glow isn’t the point. “The
fluorescence may not be the important aspect. It could be a side
effect,” he says. It could be that fluorescent proteins are actually
there just to absorb light as the part of some metabolism, and the glow
that we see is incidental to its true purpose.
More at
The Atlantic. The paper is at
Proc Roy Soc B.
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