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Plankton community composition and vertical migration during polar night in Kongsfjorden

Abstract

The polar night in the Arctic is characterized by up to six months of darkness, low temperatures and limited food availability. Biological data on species composition and abundance during this period are scarce due to the logistical challenges posed when sampling these regions. Here, we characterize the plankton community composition during the polar night using water samplers and zooplankton net samples (50, 64, 200, 1500 μm), supplemented by acoustics (ADCPs, 300 kHz), to address a previously unresolved question–which species of zooplankton perform diel vertical migration during the polar night? The protist community (smallest plankton fraction) was mainly represented by ciliates (Strombidiida). In the larger zooplankton fractions (50, 64, 200 μm) the species composition was represented primarily by copepod nauplii and small copepods (e.g., Microcalanus spp., Pseudocalanus spp. and Oithona similis). In the largest zooplankton fraction (>1500 μm), the euphausiid, Thysanoessa inermis, was the most abundant species followed by the chaetognath Parasagitta elegans. Classical DVM was not observed throughout the darkest parts of the polar night (November–mid-January), although, subtle vertical migration patterns were detected in the acoustic data. With the occurrence of a more distinct day–night cycle (i.e., end of January), acoustical DVM signals were observed, paralleled by a classical DVM pattern in February in the largest fractions of zooplankton net samples. We suggest that Thysanoessa spp. are main responsible for the acoustical migration patterns throughout the polar night, although, chaetognaths and copepods may be co-responsible.

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Acknowledgments

The authors would like to thank the crew onboard RV Helmer Hanssen and KV Svalbard for their support and efforts during the cruises. A special thanks to Colin Griffiths and Daniel Vogedes for their assistance in sampling and to Michael Greenacre and Sigrun Jonasdottir for criticism and guidance in stages of manuscript writing. Ship time was provided by UiT—The Arctic University of Norway. This study was funded by two Grants from the Norwegian Research Council: CircA (Project number 214271) and Marine Night (Project number 226417).

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Correspondence to Julie Cornelius Grenvald.

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This article belongs to the special issue on the “Kongsfjorden ecosystem—new views after more than a decade of research,” coordinated by Christian Wiencke and Haakon Hop.

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Grenvald, J.C., Callesen, T.A., Daase, M. et al. Plankton community composition and vertical migration during polar night in Kongsfjorden. Polar Biol 39, 1879–1895 (2016). https://doi.org/10.1007/s00300-016-2015-x

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Keywords

  • Protists
  • Zooplankton
  • Vertical migration
  • Polar night
  • Kongsfjorden
  • Svalbard