14:30–14:45 | ABSTRACT 1154
LINKING DISSOLVED ORGANIC CARBON PRODUCTION TO CARBON SEQUESTRATION IN THE NORTH ATLANTIC SUBTROPICAL GYRE
Understanding how oceanic carbon sequestration emerges from coupled biological, physical, and microbial processes remains a major challenge, particularly in oligotrophic regions where direct observations are limited. Here, we use multi-platform optical observations to investigate carbon sequestration multi-pathways in the central North Atlantic Subtropical Gyre. We combined Biogeochemical-Argo float measurements with satellite ocean color products and a four-dimensional reconstruction physical export of organic carbon fields. Key bio-optical variables, including particulate backscattering (bbp), chlorophyll-a, and fluorescent dissolved organic matter (FDOM), are used to characterize carbon stocks, export, and microbial processing. The robust relationship between FDOM and apparent oxygen utilization (AOU) provides an optical proxy for microbial carbon pump (MCP) efficiency, representing the transformation of labile dissolved organic carbon (DOC) into refractory DOC in the mesopelagic ocean. Optical observations further indicate that particle size distribution helps regulate the POC export process in oligotrophic waters. Surface-produced particulate and dissolved organic carbon (POC and DOC) are exported to depth through physical injection processes, with POC accounting for approximately half of the total BCP export. Variability in surface POC and DOC export is tightly linked to subsequent increases in MCP activity, with a lag of about 6 to 7 months, reflecting microbial transfer of DOC into long-lived refractory forms in the depth. Our work demonstrates that a robust, multi-platform optical observation framework for deriving biogeochemical quantities helps reveal a mechanistic link between organic carbon export, DOC transformation, and long-term carbon sequestration.
Mengyu Li, CNR ISMAR, [email protected], https://orcid.org/0000-0003-0939-7406
Marco Bellacicco, CNR ISMAR, [email protected], https://orcid.org/0000-0002-0477-173X
Gemma Kulk, Marine Processes and Observations, Plymouth Marine Laboratory, [email protected], https://orcid.org/0000-0002-0224-7547
Bror Jönsson, Ocean Process Analysis Lab, University of New Hampshire, [email protected], https://orcid.org/0000-0001-9580-3129
Mayra Rodriguez, Marine Processes and Observations, Plymouth Marine Laboratory, [email protected], https://orcid.org/0000-0002-0936-4201
Bruno Buongiorno Nardelli, CNR ISMAR (Napoli), [email protected], https://orcid.org/0000-0002-3416-7189
Xuerong Sun, Faculty of Environment, Science and Economy, University of Exeter, [email protected], https://orcid.org/0000-0003-4855-6692
Giovanni La Forgia, CNR ISMAR, [email protected], https://orcid.org/0000-0002-8543-6369
Emanuele Organelli, CNR ISMAR, [email protected], https://orcid.org/0000-0001-8191-8179
