Abstract:

Climate change is affecting ecosystems, both marine and terrestrial, and this makes it critically important to improve our understanding of couplings between environmental change – natural or human-induced - and the biology and ecology of marine organisms. As illustrated in the logo associated with the present Research Topic (RT), this theme is inspired by the dynamics of the North Atlantic subpolar gyre (SPG) and its interaction with the Atlantic inflow (poleward arrow) and the returning cold subarctic watermasses (equatorward arrow) - collectively referred to as the Atlantic Meridional Overturning Circulation (AMOC). During the last ~15 years, research has shed light on the importance key physical drivers, such as the SPG, on the dynamics of all trophic levels in the subpolar North Atlantic (SPNA). The present RT elaborates on linkages between the changing physical and biogeochemical environment and the organisms inhabiting this mid- to high latitude area.
The concept of biogeographical zones and ecoregions with large areas sharing similar physical, biogeochemical and biological characteristics is presently making a come-back in marine science. When two different water masses rest against each other they create frontal zones delineating biogeographic boundaries across which the physical properties and biological assemblages change rapidly over short distances. The outlines of oceanic gyres are determined by such water mass boundaries, and therefore constitute frontal zones and biogeographical boundaries. Changes in gyre size and circulation strength warp the biogeographic morphology directly, as well as regulating the transport of water between biomes. This justifies our inclusion of the word ‘biogeography’ in the title of this RT. The 19 papers compiled in this RT cover the entire SPNA, from the Labrador Sea in southwest, the North Sea and Skagerrak in southeast to the Barents Sea, Svalbard and the Iceland Sea in the north. All trophic levels are represented, with physical oceanography and biogeochemistry here referred to as the 0-th level, primary producers (e.g. phytoplankton, 1st level), secondary producers (e.g. zooplankton, 2nd level) and fish/ predators (3rd level). Unfortunately, no contribution has addressed sea mammals or seabirds. In this editorial, we will introduce each paper by a categorization into the following five recurrent themes: 1) Phenology, 2) Spatial segregation, 3) Biological hotspots, 4) Regime shifts and 5) Long-term trends. The papers generally discuss more than one of these themes, and after their initial introduction, this will be referred to by in-text citations. The trophic levels addressed will also be noted, with several papers addressing more than one level.