Sinking through the inky ocean, it would seem that there is little light at depth: but you'd be wrong. 'In the mesopelagic realm [200 m] bioluminescence [light produced by animals] is very common', says Snke Johnsen from Duke University, USA, explaining that many creatures are capable of producing light, yet rarely do so. But how much light do the inhabitants of the ocean floor (benthos) generate? Explaining that some bioluminescence is generated when organisms collide, Johnsen says, 'In the benthos you have a current moving over complicated ground with all the things in the water banging into it, so one idea was that there would be a fair amount of bioluminescence.' However, few people have visited this remote and inhospitable habitat. Intrigued by the animals that dwell there and the possibility that bioluminescent bacteria coating the ocean floor might glow faintly, long time collaborators Tamara Frank, Sonke Johnsen, Steven Haddock, Edith Widder and Charles Messing teamed up to find out just how much light is produced by seabed residents. The team discovered that bioluminescent animals are relatively rare but blue-green bioluminescence produced when plankton collide with obstacles is relatively common. They also found that deep-sea predators have incredibly sensitive colour vision and they publish their discoveries in a pair of papers in the Journal of Experimental Biology at http:/jeb.biologists.org.
Descending to the bottom of the ocean near the Bahamas in Harbor Branch Oceanographic's Johnson- Sea-Link submersible, switching off all the lights and adapting to the darkness, the group were amazed to find themselves continually surrounded by tiny flashes of light as bioluminescent plankton collided with coral and boulders strewn across the floor. However, there was no evidence of the all-pervasive glow produced by bioluminescent bacteria that the team had hoped to find. 'We weren't in re
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The Company of Biologists