Naturally occurring bioluminescence on the deep-sea floor

In the deep sea, bioluminescence that is not stimulated by the observer is estimated to be extremely low. Observations of naturally occurring bioluminescence, using an ultra-low-light video camera, at a solitary rock populated with sessile fauna revealed bioluminescent activity was 155 times higher than predicted background levels at 2000-3000 m. These findings, from the Mid-Atlantic Ridge (49.022 degrees N, 27.693 degrees W), suggest that, at depths below the penetration of sunlight, complexity in the physical environment may influence the visual environment, with potential effects on the behaviour of mobile deep sea fauna, prompting a reappraisal of the visual environment in the deep sea. (C) 2011 Elsevier B.V. All rights reserved.