English
norskBlar i forfatter "Cohen, Jonathan H."
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All-sky camera system providing high temporal resolution annual time series of irradiance in the arctic
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-23)The ArcLight observatory provides hourly continuous time series of light regime data (intensity, spectral composition, and photoperiod) from the Arctic, Svalbard at 79° N. Until now, no complete annual time series of biologically relevant light has been provided from the high Arctic due to insufficient sensitivity of commercial light sensors during the Polar Night. We describe a camera system providing ... -
Artificial light during the polar night disrupts Arctic fish and zooplankton behavior down to 200 m depth
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-05)For organisms that remain active in one of the last undisturbed and pristine dark environments on the planet—the Arctic Polar Night—the moon, stars and aurora borealis may provide important cues to guide distribution and behaviours, including predator-prey interactions. With a changing climate and increased human activities in the Arctic, such natural light sources will in many places be masked by ... -
Bioluminescence as an ecological factor during high Arctic polar night
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016)Bioluminescence commonly influences pelagic trophic interactions at mesopelagic depths. Here we characterize a vertical gradient in structure of a generally low species diversity bioluminescent community at shallower epipelagic depths during the polar night period in a high Arctic fjord with in situ bathyphotometric sampling. Bioluminescence potential of the community increased with depth to a peak ... -
Is ambient light during the high Arctic polar night sufficient to act as a visual cue for zooplankton?
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015-06-03)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 ... -
Light in the Polar Night
(Chapter; Bokkapittel, 2020)How much light isa vailable for biological processes during Polar Night? This question appears simple enough. But the reality is that conventional light sen- sors for measuring visible light (~350 to ~700 nm) have not been sensitive enough to answer it. Beyond this technical challenge, “light” is a general term that must be qualified in terms of “light climate” before it has meaning for biological ... -
A marine zooplankton community vertically structured by light across diel to interannual timescales
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-24)The predation risk of many aquatic taxa is dominated by visually searching predators, commonly a function of ambient light. Several studies propose that changes in visual predation will become a major climate-change impact on polar marine ecosystems. The High Arctic experiences extreme seasonality in the light environment, from 24 h light to 24 h darkness, and therefore provides a natural laboratory ... -
New insights into the biology of Calanus spp. (Copepoda) males in the Arctic
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018)Adult males of <i>Calanus</i> copepods in the Arctic are mainly observed between late autumn and late spring, and are seldom recorded during summer. Due to logistical constraints, there are still relatively few studies on zooplankton in high-latitude regions during the winter, and subsequently, little is known about <i>Calanus</i> males. Here, we present data on abundance, spatial distribution, ... -
Pelagic organisms avoid white, blue, and red artificial light from scientific instruments
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-22)In situ observations of pelagic fish and zooplankton with optical instruments usually rely on external light sources. However, artificial light may attract or repulse marine organisms, which results in biased measurements. It is often assumed that most pelagic organisms do not perceive the red part of the visible spectrum and that red light can be used for underwater optical measurements of biological ... -
Photoperiodism and overwintering in boreal and sub-Arctic Calanus finmarchicus populations
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-08)The copepod Calanus finmarchicus, a key species in the North Atlantic, generally spends the non-productive season by descending into deep waters and entering diapause, a physiological state characterized by reduced metabolism and arrested development. In the open ocean, overwintering depths are below 600 m, where temperature and light conditions are favourable to initiate diapause. However, C. ... -
Photophysiological cycles in Arctic krill are entrained by weak midday twilight during the Polar Night
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-19)Light plays a fundamental role in the ecology of organisms in nearly all habitats on Earth and is central for processes such as vision and the entrainment of the circadian clock. The poles represent extreme light regimes with an annual light cycle including periods of Midnight Sun and Polar Night. The Arctic Ocean extends to the North Pole, and marine light extremes reach their maximum extent in ... -
Spectral and RGB analysis of the light climate and its ecological impacts using an all-sky camera system in the Arctic
(Journal article; Tidsskriftartikkel, 2023-06-21)The ArcLight observatory provides an hourly continuous time series of all-sky images providing light climate data (intensity, spectral composition, and photoperiod) from the Arctic (Svalbard at 79°N). Until recently, no complete annual time series of light climate relevant for biological processes has been provided from the high Arctic because of insufficient sensitivity of commercial light sensors ... -
Use of an Autonomous Surface Vehicle reveals small-scale diel vertical migrations of zooplankton and susceptibility to light pollution under low solar irradiance
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-01-10)Light is a major cue for nearly all life on Earth. However, most of our knowledge concerning the importance of light is based on organisms’ response to light during daytime, including the dusk and dawn phase. When it is dark, light is most often considered as pollution, with increasing appreciation of its negative ecological effects. Using an Autonomous Surface Vehicle fitted with a hyperspectral ...
