'Community Composition and Size Distribution of Mesozooplankton in the Upper Kilometer of the Global Ocean'

Here, we provides a novel comprehensive analysis of zooplankton vertical zonation, community composition and size structure in the upper kilometer of all ocean basins. We explored the 3-dimentional (3D) distribution of multinet samples from 57 stations, over 5 different layers from the surface to the first kilometer of the deep sea, during the Tara Oceans expedition (2009-2013). Samples were processed with an imaging method and sorted in 19 taxa as well as among 72 size classes, from 0.29 to 17.73mm. The concentration and mean size of zooplankton decreased with latitude, from the poles to the equator. Concentration decreased with depth, from surface to 900m depth, while mean size increased. Zooplankton concentration and mean size were more homogeneous in the interior, deeper regions of the ocean compared to the surface. A redundancy analysis (RDA) suggested that the structure of zooplankton communities in the mesopelagic layer depends on the type and productivity of phytoplankton at the surface and subsequent export of organic matter towards deeper layers. In the interior of the sea, temperature, particle, and oxygen concentrations are the dominant factors that explain the variability in community composition. The comparison of community structure between ocean basins reveals that the greatest difference occurs in the epipelagic layer while the differences decrease with depth.