Light plays a critical role in the functioning of the marine environment. In the dark ocean, bioluminescent organisms are the only visually relevant sources of light. Cameras of different sensitivities were used to compare the density of pelagic bioluminescent sources (BL) of different light intensities at a regional scale: the image-intensified charge-coupled device for deep-sea research (ICDeep), an image-intensified silicon intensifier target (ISIT) camera and a silicon intensifier target (SIT) camera. Pelagic ICDeep values were higher than ISIT measurements by a mean factor of 7.6 in the Mediterranean Sea and 3.5 in the Atlantic Ocean. Atlantic ISIT values were higher than SIT values by a mean factor of 4.5. Standardising bioluminescence measurements to the near-seafloor (0-400 m above bottom) layer, BLNSF, a logarithmic decrease with depth was observed from three independent datasets (slopes not significantly different): ISIT (Atlantic, Mediterranean), ICDeep (Mediterranean). Intercepts from ICDeep measurements were higher than ISIT measurements by a factor of 4.4. From these trends, a conversion factor to calculate benthopelagic plankton biomass from near-seafloor BLNSF density was derived. Calibration of the ICDeep enabled calculation of the minimum intensity of source visible to that camera. BLNSF sources of low-light intensity (a parts per thousand yen1.4 x 10(-7) W m(-2)) outnumber fourfold sources of greater intensity (> ca. 10(-6) W m(-2) (lambda (peak) = 470 nm). This reveals a high abundance of low-light bioluminescent sources in the marine environment, with mean pelagic densities of 33.15 sources m(-3) (Atlantic) and 6.79 sources m(-3) (Mediterranean) between 500 and 1500 m depth.
Bibliographical noteDate of Acceptance: 03/07/2015
Acknowledgments J.C. was funded by UK NERC studentship (NE/F012020/1). J.A. was funded by Ramon y Cajal program (MICINN). We also thank G.P. Gasparini (leader RV Urania cruise), H. Kontoyiannis (leader RV Aegaeo cruises), Dr. F. Sardá (leader RV Sarmiento de Gamboa cruise) and colleagues for facilitating on board work
- neutrino telescope
- marine animals
- NE Atlantic