Image-based global analysis of the biological carbon pump

• Main Author: Drago, Laetitia
• Other Authors: Laboratoire d'océanographie de Villefranche (LOV), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut de la Mer de Villefranche (IMEV), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Sorbonne Université, Lars Stemmann, Rainer Kiko
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2023
• Subjects: Carbon pump; Imaging; Zooplankton; Particles; Pompe à carbone; Imagerie; Zooplancton; Particules; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; [STAT.ML]Statistics [stat]/Machine Learning [stat.ML]; [INFO.INFO-MO]Computer Science [cs]/Modeling and Simulation; [INFO.INFO-TI]Computer Science [cs]/Image Processing [eess.IV]; North Atlantic
• Online Access: https://theses.hal.science/tel-04483392; https://theses.hal.science/tel-04483392/document; https://theses.hal.science/tel-04483392/file/DRAGO_Laetitia_these_2023.pdf

The biological carbon pump (BCP) plays a central role in the global ocean carbon cycle, transporting carbon from the surface to the deep ocean and sequestering it for long periods. This work aims to analyse two key players of the BCP: zooplankton and particles. To this end, we use in situ imaging data from the Underwater Vision Profiler (UVP5) to investigate two primary axes: 1) the global distribution of zooplankton biomass and 2) carbon export in the context of a North Atlantic spring bloom. Our objectives includes a quantification of global zooplankton biomass, enhancing our comprehension of the BCP via morphological analysis of particles, and assessing and comparing the gravitational flux of detrital particles during a the North Atlantic spring bloom using high-resolution UVP5 data. With the help of UVP5 imagery and machine learning through habitat models using boosted regression trees, we investigate the global distribution of zooplankton biomass and its ecological implications. The results show maximum zooplankton biomass values around 60°N and 55°S and minimum values within the oceanic gyres, with a global biomass dominated by crustaceans and rhizarians. By employing machine learning techniques on globally homogeneous data, this study provides taxonomical insights into the distribution of 19 large zooplankton groups (1-50 mm equivalent spherical diameter). This first protocol estimates global, spatially resolved zooplankton biomass and community composition from in situ imaging observations of individual organisms. In addition, within the unique context of the EXPORTS 2021 campaign, we analyse UVP5 data obtained by deploying three instruments in a highly retentive eddy. After clustering the 1,720,914 images using Morphocluster, a semi-autonomous classification software, we delve into the characteristics of the marine particles, studying their morphology through an oblique framework that follows a plume of detrital particles between the surface and 800 m depth. The results of the plume following approach ...