Vertical migration of pelagic and mesopelagic scatterers from ADCP backscatter data in the Southern Norwegian Sea

Records of backscatter and vertical velocity obtained from moored Acoustic DopplerCurrent Profilers (ADCP) enabled new insights into the dynamics of deep scattering layers (DSLs) and diel vertical migration (DVM) of mesopelagic biomass between these deep layers and the near-surface photic zone in th...

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Bibliographic Details
Published in:Frontiers in Marine Science
Main Authors: Cisewski, Boris, Hatun, Hjalmar, Kristiansen, Inga, Hansen, Bogi, Larsen, Karin Margretha H., Eliasen, Solva Karadottir, Jacobsen, Jan Arge
Format: Article in Journal/Newspaper
Language:English
Published: 2021
Subjects:
Text
article
ddc:570
diel vertical migration > ADCP backscatter > seasonal cycles > deep scattering layer > Southern Norwegian Sea > mesopelagic fish > zooplankton
Norwegian Sea
Copepods
Online Access:https://doi.org/10.3389/fmars.2020.542386
https://www.openagrar.de/receive/openagrar_mods_00066380
https://www.openagrar.de/servlets/MCRFileNodeServlet/openagrar_derivate_00035500/dn063248.pdf
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Summary:Records of backscatter and vertical velocity obtained from moored Acoustic DopplerCurrent Profilers (ADCP) enabled new insights into the dynamics of deep scattering layers (DSLs) and diel vertical migration (DVM) of mesopelagic biomass between these deep layers and the near-surface photic zone in the southern Norwegian Sea. The DSL exhibits characteristic vertical movement on inter-monthly time scales, which is associated with undulations of the main pycnocline between the warm Atlantic waterand the underlying colder water masses. Timing of the DVM is closely linked to the day-night light cycle—decent from the photic zone just before sunrise and ascent immediately after sunset. Seasonal variations are also evident, with the highest DVM activity and lowest depth averaged mean volume backscatter strength (MVBS) duringspring. This suggests that both oceanographic and optical conditions are driving the complex dynamics of pelagic and mesopelagic activity in this region. We hypothesizethat the increased abundance of calanoid copepods in the near-surface layer during spring increases the motivation for vertical migration of pelagic and mesopelagic species, which therefore can explain the increased DVM activity during this season.

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