Moonlight Drives Ocean-Scale Mass Vertical Migration of Zooplankton during the Arctic Winter

Abstract

In extreme high-latitude marine environments that are without solar illumination in winter, light-mediated patterns of biological migration have historically been considered non-existent [1]. However, diel vertical migration (DVM) of zooplankton has been shown to occur even during the darkest part of the polar night, when illumination levels are exceptionally low [2, 3]. This paradox is, as yet, unexplained. Here, we present evidence of an unexpected uniform behavior across the entire Arctic, in fjord, shelf, slope and open sea, where vertical migrations of zooplankton are driven by lunar illumination. A shift from solar-day (24-hr period) to lunar-day (24.8-hr period) vertical migration takes place in winter when the moon rises above the horizon. Further, mass sinking of zooplankton from the surface waters and accumulation at a depth of ∼50 m occurs every 29.5 days in winter, coincident with the periods of full moon. Moonlight may enable predation of zooplankton by carnivorous zooplankters, fish, and birds now known to feed during the polar night [4]. Although primary production is almost nil at this time, lunar vertical migration (LVM) may facilitate monthly pulses of carbon remineralization, as they occur continuously in illuminated mesopelagic systems [5], due to community respiration of carnivorous and detritivorous zooplankton. The extent of LVM during the winter suggests that the behavior is highly conserved and adaptive and therefore needs to be considered as "baseline" zooplankton activity in a changing Arctic ocean [6-9]. VIDEO ABSTRACT.

High Latitude Epipelagic and Mesopelagic Scattering Layers—A Reference for Future Arctic Ecosystem Change

“…The classical paradigm of biological quiescence during the Arctic polar night, has been challenged by a series of works recently published concerning feeding hyperiid amphipods during Arctic-darkness (Kraft et al, 2013), mass-vertical zooplankton migration during Arctic winter driven by moonlight (Last et al, 2016), and unexpected levels of biological activity during the polar night (Berge et al, 2015). Berge et al (2009) showed that diel vertical migration during the Arctic winter is an important feature of the zooplankton community, especially for copepods in the epipelagial.…”

“…Baseline information regarding physical, chemical, and biological conditions is lacking for many parts of the Arctic (Wassmann and Reigstad, 2011; and crucial information on processes, species interactions, and behaviorial patterns recently uncovered (Berge et al, 2009(Berge et al, , 2014(Berge et al, , 2015Kraft et al, 2013;Last et al, 2016), suggests that current knowledge of the high Arctic marine ecosystem is incomplete. Thus, our understanding of the susceptibility of the Arctic ecosystem to a warmer ocean climate is limited and pathways along which changes will proceed are uncertain.…”

“…Thus, our understanding of the susceptibility of the Arctic ecosystem to a warmer ocean climate is limited and pathways along which changes will proceed are uncertain. Until recently it is the dynamics in the epipelagic zone, mostly focusing on fjord systems, that has been examined (Berge et al, 2009(Berge et al, , 2014(Berge et al, , 2015Kraft et al, 2013;Last et al, 2016). These investigations provide, however, little insight on the deeper living mesopelagic community and the coupling between the epipelagic and the mesopelagic communities (cf.…”

Evidence of Diel Vertical Migration of Mesopelagic Sound-Scattering Organisms in the Arctic

“…Cronin et al, 2016), that can be particularly important during the Arctic winter. Recently published work from this region show that some organisms respond to even very weak variations in light level, and mass-vertical migration during Arctic winter driven by moonlight has been documented (Cohen et al, 2015;Last et al, 2016). However, these studies have focused on zooplankton in the upper 50 m.…”

Plankton and the Invisible Barriers in the Tropical Ocean

“…Diel vertical migration (DVM) is a well-documented behavior among diverse taxa of zooplankton from tropical environments (TrE) [1][2][3] to higher latitude environments [4][5], and the adaptive significance of this behavior has been explained by a wide array of competing hypothesis [6]. The major driving factors of this behavior can be attributed to predator avoidance [7], prevention from light related mortality [8], the bioenergetic advantage [9], and demographic benefits [10].…”