Typology of Plankton Communities seen by In Situ Imaging, from the Epi to the Mesopelagic Layers of the Global Ocean

Thelma Panaiotis1, Marcel Babin2, Tristan Biard3, Francois Carlotti4, Laurent Coppola1, Lionel Guidi1, Helena Hauss5, Lee Karp-Boss6, Rainer Kiko5, Fabien Lombard1, Andrew M. P. McDonnell7, Marc Picheral8, Andreas Rogge9,10, Anya M Waite11, Jean Olivier Irisson1 and Lars Stemmann1, (1)Laboratoire d'Océanographie de Villefranche (LOV), UMR 7093, Sorbonne Université, Villefranche-sur-Mer, France, (2)Takuvik Joint International Laboratory, Université Laval & CNRS, Québec, QC, Canada, (3)Laboratoire d'Océanologie et de Géosciences (LOG), UMR 8187, Université du Littoral Côte d'Opale, Wimereux, France, (4)CNRS - Aix Marseille University, Mediterranean Institute of Oceanography, Marseille, France, (5)GEOMAR Helmholtz Centre for Ocean Research, Kiel, Germany, (6)University of Maine, Orono, ME, United States, (7)University of Alaska Fairbanks, Fairbanks, AK, United States, (8)Laboratoire d’Océanographie de Villefranche (LOV), UMR 7093, Sorbonne Université, Villefranche-sur-Mer, France, (9)Institute for Ecosystem Research, Kiel University, Kiel, Germany, (10)Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research, Bremerhaven, Germany, (11)Ocean Frontier Institute, Dalhousie University, Halifax, NS, Canada
Several attempts have been made at partitioning marine ecosystems in large biomes, like terrestrial ecosystems. This remains difficult due to the lack of synoptic observations of the open ocean. A consensus has been found for vertical partitions and several propositions have been made for horizontal partitions, mainly based on biogeochemical signatures combining in situ optical data (fluorescence, light attenuation), remote sensing, and possibly biogeochemical model output. Yet, the consistency between these mostly biogeochemical partitions and the spatial distribution of larger (> 600 µm) planktonic organisms remains an open question.

We studied the distribution of plankton communities and their relationship with their immediate environment by analysing a global data set of ~3000 vertical CTD profiles equipped with an Underwater Vision Profiler 5 (UVP5). This represents over 700 000 images of large mesozooplankton, colonies of phytoplankton, and marine snow. Multivariate statistical ordination and regression methods were used to describe patterns in community composition and their correlation with environmental variables in three layers of the upper kilometer of the ocean (epi-, upper-meso- and lower-meso-pelagic).

Three types of plankton communities emerged: Trichodesmium-dominated in the intertropical band, Copepoda-dominated at high latitudes, or Rhizaria-dominated elsewhere; the mesopelagic layers lacked Trichodesmium. The comparison between the distribution of these communities and a set of existing biogeographical partitions of the ocean suggested that the structure of plankton communities described above is mostly driven by basin-level environmental conditions rather than the conditions in the immediate vicinity of the sampling site.