Effects of sea ice retreat and ocean warming on the Laptev Sea continental slope ecosystem (1993 vs 2012)

Christina Bienhold*, Vibe Schourup-Kristensen, Thomas Krumpen, Eva Maria Nöthig, Frank Wenzhöfer, Meri Korhonen, Myriel Vredenborg, Laura Hehemann, Antje Boetius

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Abstract

The central Arctic Ocean is rapidly changing due to amplified warming and sea ice retreat. Nonetheless, it remains challenging to document and decipher impacts on key ecosystem processes such as primary production and pelagic-benthic coupling, due to limited observations in this remote area. Here we investigated environmental changes at the Laptev Sea continental slope (60-3400 m water depth) from the surface to the seafloor, by replicating sample transects two decades apart. Mean break-up of sea ice occurred earlier and mean freeze-up occurred later in 2012 compared to 1993, extending the ice-free period by more than 30 days. On average, observations and model results showed an annual increase in primary production of 30% and more in the study area in 2012. In contrast, calculated and modelled fluxes of particulate organic carbon (POC) to the seafloor were only slightly higher in 2012 and did not extend as far into the deep Laptev Sea as the increase in primary production, possibly due to a more developed retention system. Nevertheless, benthic surveys revealed a substantial increase in phytodetritus availability at the seafloor along the entire transect from the shelf edge to the deep sea. This calls for carbon input by lateral advection from the shelves, additional input from sea ice, and/or a late summer bloom. We also investigated the composition and activity of bacterial communities at the seafloor and potential linkages to the observed environmental changes. While bacterial abundance, biomass and overall community structure showed no systematic differences between the two contrasting years at all depths, extracellular enzymatic activities had increased as a result of higher food availability. This was partly reflected in higher benthic oxygen uptake, indicating a moderate impact on benthic remineralization rates at the time of sampling. Our results show considerable effects of ocean warming and sea ice loss on the ecosystem from the surface ocean to the seafloor in the Laptev Sea, which are likely to continue in the coming decades.

OriginalsprogEngelsk
Artikelnummer1004959
TidsskriftFrontiers in Marine Science
Vol/bind9
ISSN2296-7745
DOI
StatusUdgivet - 2022

Bibliografisk note

Funding Information:
Funding was received from the ERC Advanced Grant ABYSS (no. 294757) to AB. Additional funding came from the Helmholtz Association and the Max Planck Society. MV was funded by the BMBF project APEAR (#03V01461). This study contributes to the HGF infrastructure program FRAM (Frontiers in Arctic Marine Monitoring). We acknowledge support by the Open Access Publication Funds of Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung.

Funding Information:
Funding was received from the ERC Advanced Grant ABYSS (no. 294757) to AB. Additional funding came from the Helmholtz Association and the Max Planck Society. MV was funded by the BMBF project APEAR (#03V01461). This study contributes to the HGF infrastructure program FRAM (Frontiers in Arctic Marine Monitoring). We acknowledge support by the Open Access Publication Funds of Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung. Acknowledgments

Publisher Copyright:
Copyright © 2022 Bienhold, Schourup-Kristensen, Krumpen, Nöthig, Wenzhöfer, Korhonen, Vredenborg, Hehemann and Boetius.

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