Is Ambient Light during the High Arctic Polar Night Sufficient to Act as a Visual Cue for Zooplankton?
Date
2015-06-03
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Publisher
PLOS (Public Library of Science)
Abstract
The light regime is an ecologically important factor in pelagic habitats, influencing a range of
biological processes. However, the availability and importance of light to these processes in
high Arctic zooplankton communities during periods of 'complete' darkness (polar night) are
poorly studied. Here we characterized the ambient light regime throughout the diel cycle
during the high Arctic polar night, and ask whether visual systems of Arctic zooplankton can
detect the low levels of irradiance available at this time. To this end, light measurements
with a purpose-built irradiance sensor and coupled all-sky digital photographs were used to
characterize diel skylight irradiance patterns over 24 hours at 79°N in January 2014 and
2015. Subsequent skylight spectral irradiance and in-water optical property measurements
were used to model the underwater light field as a function of depth, which was then weighted
by the electrophysiologically determined visual spectral sensitivity of a dominant high
Arctic zooplankter, Thysanoessa inermis. Irradiance in air ranged between 1–1.5 x 10-5
μmol photons m-2 s-1 (400–700 nm) in clear weather conditions at noon and with the moon
below the horizon, hence values reflect only solar illumination. Radiative transfer modelling
generated underwater light fields with peak transmission at blue-green wavelengths, with a
465 nm transmission maximum in shallow water shifting to 485 nm with depth. To the eye of
a zooplankter, light from the surface to 75 m exhibits a maximum at 485 nm, with longer
wavelengths (>600 nm) being of little visual significance. Our data are the first quantitative
characterisation, including absolute intensities, spectral composition and photoperiod of biologically
relevant solar ambient light in the high Arctic during the polar night, and indicate
that some species of Arctic zooplankton are able to detect and utilize ambient light down to
20–30m depth during the Arctic polar night.
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Citation
Cohen JH, Berge J, Moline MA, Sørensen AJ, Last K, Falk-Petersen S, et al. (2015) Is Ambient Light during the High Arctic Polar Night Sufficient to Act as a Visual Cue for Zooplankton? PLoS ONE 10 (6): e0126247. doi:10.1371/journal.pone.0126247