In the Caribbean, glowing organisms don't just make for a visual spectacle, but also have finely honed visual systems that may allow bottom dwellers to distinguish what's a meal and what's poison, a sort of color-coding vision.
Bioluminescence, light given off through a chemical reaction in living creatures, has long piqued the curiosity of researchers since Greek philosopher Aniximenes found that light emanated from water when struck by an oar nearly 2,500 years ago.
Since then, oceanographers have identified many bioluminescent organisms, including the sorts of plankton that Aniximenes would have seen, but little remains known about the phenomenon at the ocean bottom.
Researchers ventured in the Johnson-Sea-Link submersible to nearly half a mile below the ocean surface in what could be the world’s first manned hunt for bioluminescent creatures in the benthic zone, the ecological niche of the seabed.
"If you sit there with the lights out, you'll see this little light show as plankton run into different habitats," study researcher Sönke Johnsen, a sensory biologist at Duke University, told LiveScience. "There is no substitute for actually being in that habitat to understand what it's like to be those animals, plus it's a great deal of fun."
The team of oceanographers surveyed the bottom of the Caribbean Sea at two different sites at a depth unreachable by natural light and to their surprise found that while few organisms could light up, what light there was came from jostled plankton.