Seasonal influences of POC fluxes to water column-benthic coupling in NGOM shelf

Continental shelves connecting the terrestrial and oceanic systems are being disrupted by climate change and human interventions with expected alterations to river discharge, carbon burial, and transport that are mostly unknown at present. In this study, we combined the benthic sedimentary carbon remineralization (bottom-up) and particulate organic carbon (POC) transport (top-down) approach to better understand the carbon cycling in Louisiana shelf which receives a significant discharge from the Mississippi River and is associated with one of the largest seasonal hypoxia in the global ocean. Oxygen (O₂) consumption and dissolved inorganic carbon (DIC) production in sediment were investigated using ex-situ core incubation during May 2023 (peak river discharge) and July 2024 (low river discharge). DIC production rates varied between 16.51 to 33.84 mmol/m²/day and O₂ consumption flux varied from 13.95 to 23.16 mmol /m²/day during the high river discharge in May 2023; whereas DIC flux and O₂ consumption flux increased significantly during low river discharge period in July 2024. ²³⁴Th based water column POC fluxes and surface sediment C accumulation estimates reveal connections between benthic remineralization and accumulation, which appears to be more strongly correlated further from the river outflow. It is important to incorporate benthic carbon fluxes in the nGOM ocean carbon budget and to understand the mechanisms driving the organic carbon remineralization in the adjacent shelf to better constrain its impact on the regional carbon cycle and associated marine ecosystems.

Presentation Preference: Oral

Primary Presenter: Mukseet Mahmood, Louisiana state university (mmahmo8@lsu.edu)

Authors:

Mukseet Mahmood, Louisiana State University  (mmahmo8@lsu.edu)

Kanchan Maiti, Louisiana State University  (kmaiti@lsu.edu)