Due to rising atmospheric carbon dioxide, alterations in pathways of the biological carbon pump (BCP) mediated by pelagic organisms as a major component of carbon export in the ocean need to be understood.  This study compares the BCP of two adjacent Norwegian fjords with similar topography but different pelagic ecosystems, one more classically fish dominated and one dominated by the deep-sea medusa Periphylla periphylla. A multitude of catching devices (MultiNets) and imaging instruments (UVP5, PELAGIOS) were compared in this study. This allowed to understand differing pathways of the BCP and identify possible sampling biases or knowledge gaps resulting from instruments used. We also hypothesized that the presence of mesopelagic fish species can be detected in the seabed sediment of the fjord by using the relatively new approach of using sedimentary environmental DNA (eDNA). Results indicate major differences between the fjord ecosystems that can be seen across all the different instruments used. High appendicularian abundances in one fjord were found mainly by the data collected with the UVP5, which was validated by video material gathered with the PELAGIOS. Copepods could mainly be detected using the MultiNets and UVP5 as they were too small to identify exactly using the PELAGIOS. Additionally, this study gives a first record of P. periphylla occurring in the Masfjord, which is typically used to represent a classical fjord ecosystem structure. All findings suggest a lower carbon sequestration rate in the P. periphylla dominated Lurefjord, due to BCP pathway alterations.

Primary Presenter: Kea Witting, GEOMAR Helmholtz Centre for Ocean Research Kiel (kwitting@geomar.de)

Authors:

Kea Witting, GEOMAR Helmholtz Centre for Ocean Research Kiel  (kwitting@geomar.de)

Henk-Jan Hoving, GEOMAR Helmholtz Centre for Ocean Research Kiel  (hhoving@geomar.de)

Dong-gyun Kim, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar-und Meeresforschung (AWI) Bremerhaven  (dong-gyun.kim@awi.de)

Klas Ove Möller, Helmholtz-Zentrum Hereon  (klas.moeller@hereon.de)

Andreas Rogge, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar-und Meeresforschung (AWI) Bremerhaven  (andreas.rogge@awi.de)

Morten Iversen, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar-und Meeresforschung (AWI) Bremerhaven  (morten.iversen@awi.de)

Barbara Niehoff, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar-und Meeresforschung (AWI) Bremerhaven  (barbara.niehoff@awi.de)

Helena Hauss, NORCE Norwegian Research Centre  (heha@norceresearch.no)