title: 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.
authors.affiliation: Scottish Association for Marine Science, Oban, Argyll PA37 1QA, UK. Electronic address: kim.last@sams.ac.uk.
authors.forename: Kim S
authors.initials: KS
authors.lastname: Last
authors.affiliation: Scottish Association for Marine Science, Oban, Argyll PA37 1QA, UK.
authors.forename: Laura
authors.initials: L
authors.lastname: Hobbs
authors.affiliation: Department for Arctic and Marine Biology, Faculty for Biosciences, Fisheries and Economics, UiT, The Arctic University of Norway, 9037 Tromsø, Norway; University Centre in Svalbard, Pb 156, 9171 Longyearbyen, Norway.
authors.forename: Jørgen
authors.initials: J
authors.lastname: Berge
authors.affiliation: Gatty Marine Laboratory, Pelagic Ecology Research Group, Scottish Oceans Institute, University of St Andrews, East Sands, St Andrews, Fife KY16 8LB, UK.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Brierley
authors.affiliation: Scottish Association for Marine Science, Oban, Argyll PA37 1QA, UK; Department for Arctic and Marine Biology, Faculty for Biosciences, Fisheries and Economics, UiT, The Arctic University of Norway, 9037 Tromsø, Norway.
authors.forename: Finlo
authors.initials: F
authors.lastname: Cottier
mesh_terms: D025041:Animal Migration / Q000502:physiology*; D000818:Animals; D001110:Arctic Regions; D001717:Birds; D005399:Fishes; D008027:Light; D008954:Models, Biological; D016081:Moon; D009792:Oceans and Seas; D012621:Seasons; D015048:Zooplankton