In the deep sea, creatures give off their own light. But bottom-dwelling animals don't bioluminesce, or give off as much light as creatures floating in the water column at similar depths, according to a new study.
Duke biologist Sonke Johnsen and his collaborators collected species of starfish, sea cucumbers, brittle stars, sea lilies, crustaceans, octopi, coral, sea pens, anemones, sponges, and one sea worm from three ocean-bottom sites near the Bahamas using the Johnson-Sea-Link submersible during a 2009 research cruise.
On board a ship, the scientists stimulated the animals with lights and chemicals to see which ones gave off their own light and photographed the results. Surprisingly, less than 20 percent of the collected creatures glowed, and most gave off light in greener wavelengths, compared to species that live at the same depths but don't live on the sea bottom.
The observations, which the team describes in the Sept. 6 Journal of Experimental Biology, also suggest that the bioluminescence happening at these sites comes primarily from plankton that glow after bumping into filter feeders protruding into their path.
Citation: Light and vision in the deep-sea benthos II: Bioluminescence at 500-1000 m depth in the Bahamian Islands. Johnsen, S., et. al. (2012). Journal of Experimental Biology.