Lights in the Deep
In two papers published in December 2006, scientists from Oceanlab, University of Aberdeen, National Oceanography Centre Southampton and University of Bristol announced the discovery of mysterious lights on the deep sea floor of the Atlantic Ocean.
In the deep sea beyond the reach of sunlight the only light is bioluminescence produced by animals and bacteria living there. Many deep-sea animals have light-producing organs on their bodies but observation of these lights in action in nature has been very rare. Normally what is seen, are flashes stimulated by agitation of water by propellers or motion of a submarine. Using a new 'stealth' unmanned vehicle that lands on the sea floor with a high sensitivity camera the team have recorded spontaneous displays by small abyssal creatures feeding at bait.
Prof Monty Priede said
"We have seen three kinds of displays, single flashes of light, animals swimming along producing repeated flashes of light and animals squirting a luminescent substance into the water".
A single animal swimming along producing repeated flashes of light. |
Several animals squirting a luminescent substance into the water creating an underwater fireworks display. |
On the deep sea floor of the Atlantic Ocean the team have recorded 30 such events per hour at 1000m depth and 3 per hour at 4000m at a standard bait comprising a single dead mackerel. “We imagine a dead whale on the sea floor would be surrounded by lights making a vivid display in the darkness of the abyss”. The problem is that submersibles that visit such sites normally have their lights on and create too much disturbance to see these effects .
Research has revealed 2 hotspots of deep sea bioluminescence in the Atlantic Ocean. One at 3200m depth off tropical West Africa where during one of the observations, two animals were recorded flashing and squirting luminescence apparently responding to one another.
Off West Africa at a depth of 3200m, are the two animals (on the right) interacting with each other using their light displays? |
Off the West coast of Ireland at 1000m depth there are some super-luminescent hotspots where so many animals squirt luminescence into the water that a football-sized ball of light is produced .
A fantastic display of luminescence observed at 1000m depth where some of the light explosions produced are the size of footballs. |
The source of light remains a mystery but is likely to be small shrimp-like creatures swimming above the sea floor. The team think they have identified the culprits off the Western Ireland but are waiting for independent checking of their work by scientific referees. It is also not known why the animals produce light, but the squirting of luminescent material is likely to be a defence mechanism. While the predators are blinded or distracted by the ball of light, the shrimp makes its escape.
"So far we have only discovered two hotspots of deep sea light, we are convinced there is much more to be discovered".
The Team
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Further information
Priede I.G., Bagley P.M., Way S., Herring P.J. & Partridge J.C. (2006) Bioluminescence in the deep sea: Free-fall lander observations in the Atlantic Ocean off Cape Verde. Deep-Sea Research I. 53 : 1272–1283. doi:10.1016/j.dsr.2006.05.004.
Gillibrand E.J.V., Bagley P.M., Jamieson A., Herring P.J., Partridge J.C., Collins M.A., Milne R. & Priede I.G. (2006) Deep Sea Benthic Bioluminescence at Artificial Food falls, 1000 to 4800m depth, in the Porcupine Seabight and Abyssal Plain, North East Atlantic Ocean. Marine Biology. 149: doi: 10.1007/s00227-006-0407-
Email: oceanlab@abdn.ac.uk