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The ocean glows with undersea life which makes its own light. These animals living on the ocean floor, beyond the reach of sunlight, have evolved this bioluminescence for camouflage, to find mates or to repel or confuse predators. They also have a sort of color vision which combines sensitivity to blue and ultraviolet light. Their detection of these shorter wavelengths may provide them a way to ensure they grab food, not poison. Two new studies published this week in Experimental Biology illuminate the scene on the sea floor. Duke University biologist Sonke Johnsen was among a crew of scientists on a submersible vehicle that explored the ocean bottom at three sites near the Bahamas. “Our original guess was that actually the whole sea floor might have a dim glow from bacteria," Johnsen says. "There are a number of bacteria that glow continually as they are breaking down dead animals and things of that sort.” But that wasn’t the case. Using the vehicle’s robotic arm, they gently tapped the coral, crabs and anything else that moved to see which seabed creatures emitted light. Only 20 percent did, compared to 90 percent of the species that populate the open ocean higher in the water column. Johnsen, who led the bioluminescence study, says the plankton produced a different color from the animals that ate them. “It is very, very blue. It’s like a blue LED. It’s just this beautiful, beautiful pure blue. Much of the light from the animals on the sea floor was green, or at least greener, and so you end up with this world where you have little blue flashes of light in the water and then green light whenever anything is touched on the bottom.” | 
