Zooplankton size distribution in the Atlantic Ocean: recent estimates from a global pelagic size structure database and relationships with environmental factors

Abstract

International audiencePlankton ecologists have long used the Normalized Biomass Size Spectrum (NBSS) as a common framework to study the size distribution of aquatic bacteria, phytoplankton, and zooplankton across various temporal and spatial scales. Systematic NBSS measurements have shown that its shape varies across ecosystems and could be used as an indicator of the state of the ecosystem. Indeed, NBSS slopes typically indicate how efficiently biomass is transferred across sizes, impacting the throughput of the biological carbon pump. Zooplankton, in particular, influences the carbon pump by feeding on and repackaging phytoplankton production, as well as respiring O2 at rates that may exceed its replenishment, contributing to the existence of Oxygen Minimum Zones (OMZ) located in the Pacific, Indian, and Atlantic Oceans. Using a range of non-intrusive imaging devices, which produce community composition datasets along with complementary size measurements of individual organisms, we investigate the size distribution of zooplankton in the Atlantic Ocean. As part of our ongoing efforts to create a Pelagic Size Structure database (PSSdb, https://www.st.nmfs.noaa.gov/copepod/pssdb/), we will present a regional assessment of zooplankton NBSSs computed at different scales and compare them to estimates generated at the global scale. We will also investigate the response of zooplankton to environmental factors, including low concentrations of dissolved O2, to foresee how the gatekeepers of the marine biological carbon pump may be impacted by future anthropogenic pressures