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ORIGINAL RESEARCH article

Front. Mar. Sci.
Sec. Deep-Sea Environments and Ecology
Volume 11 - 2024 | doi: 10.3389/fmars.2024.1363542

Water mass characteristics and hydrodynamics at an inshore versus an offshore mid-Norwegian cold-water coral reef habitat

Provisionally accepted
Janina V. Büscher Janina V. Büscher 1,2*Katriina Juva Katriina Juva 3Sascha Floegel Sascha Floegel 3Max Wisshak Max Wisshak 4Andres Rüggeberg Andres Rüggeberg 5Ulf Riebesell Ulf Riebesell 2Armin U. Form Armin U. Form 2
  • 1 School of Geography and Environmental Sciences, Ulster University, Coleraine, United Kingdom
  • 2 Department of Marine Biogeochemistry, GEOMAR Helmholtz Center for Ocean Research Kiel, Helmholtz Association of German Research Centres (HZ), Kiel, Schleswig-Holstein, Germany
  • 3 Department of Ocean Circulation and Climate Dynamics, GEOMAR Helmholtz Center for Ocean Research Kiel, Helmholtz Association of German Research Centres (HZ), Kiel, Schleswig-Holstein, Germany
  • 4 Marine Research Department, Senckenberg am Meer Wilhelmshaven, Wilhelmshaven, Germany
  • 5 Department of Geosciences, Université de Fribourg, Fribourg, Fribourg, Switzerland

The final, formatted version of the article will be published soon.

    Cold-water coral reefs form complex benthic habitats, supporting thousands of species. The broadscale environmental tolerances of reef-forming species such as Lophelia pertusa are well studied, but small-scale differences between different reef settings have received little attention so far. The controlling factors of thriving cold-water coral reefs and how these habitats differ in terms of framework extent, coral colony morphology, and associated fauna could reveal how these benthic ecosystems form and expand. Information on the natural range of environmental fluctuations could provide a better understanding of the resilience of such ecosystems towards environmental changes. Our study aimed to elaborate small-scale forces on local hydrodynamics and oceanographic parameters at two geographically close but contrasting reef sites in mid-Norway. We investigated natural fluctuations and the seasonal variability of environmental conditions of an inshore and an offshore Lophelia-dominated reef over an annual cycle by time series monitoring of physical properties by benthic landers and water sampling for biogeochemical variables using CTD casts. The flow fields at the extensive reef on the offshore Sula Ridge and a bank reef at Nord-Leksa in a fjord-system differed regarding both short-term and seasonal levels. The inshore flow field was strong and tidally driven, whereas the offshore flow field was slower with large seasonal variability. The local flow regimes and the seasonal atmospheric forcing could explain the observed seasonality of the hydrographic variables and the observed inter-annual variability in biogeochemical variables. Comparison with a flow model showed that the natural short-term and seasonal variability are driven by small-scale forcing that is not represented in model analyses. These results suggest that local hydrodynamics together with sea-floor topography control the reef extent and the morphology of cold-water coral colonies.

    Keywords: Cold-water Corals, Lophelia pertusa, Desmophyllum pertusum, long-term monitoring, Benthic landers, Environmental characteristics, biogeochemistry, Coral morphology British English language style is preferred

    Received: 30 Dec 2023; Accepted: 16 Jul 2024.

    Copyright: © 2024 Büscher, Juva, Floegel, Wisshak, Rüggeberg, Riebesell and Form. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Janina V. Büscher, School of Geography and Environmental Sciences, Ulster University, Coleraine, United Kingdom

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