Deep-sea low-light radiometer system

Abstract

Two single-waveband low-light radiometers were developed to characterize properties of the underwater light field relevant to biological camouflage at mesopelagic ocean depths. Phenomena of interest were vertical changes in downward irradiance of ambient light at wavelengths near 470 nm and 560 nm, and flashes from bioluminescent organisms. Depth profiles were acquired at multiple deep stations in different geographic regions. Results indicate significant irradiance magnitudes at 560 nm, providing direct evidence of energy transfer as described by Raman scattering. Analysis of a night profile yielded multiple examples of bioluminescent flashes. The selection of high-sensitivity, high-speed silicon photomultipliers as detectors enabled measurement of spectrally-resolved irradiance to greater than 400 m depth.

Dissolved oxygen as a constraint on daytime deep scattering layer depth in the southern California current ecosystem

“…Neither the effects of differential shading due to plankton patchiness nor midwater bioluminescence heave been considered here. The ability to determine the DSL response to light levels would be enhanced by direct in situ light measurements (e.g., Haag et al 2014). Furthermore, there were some segments of the backscatter data where the algorithm failed to detect an upper DSL boundary due to heightened backscatter throughout the upper water column.…”