Quantifying Sargassum and Carbon Export from Satellites to the Seafloor in the Great Atlantic Sargassum Belt (GASB)

For over a decade, unprecedented amounts of the brown seaweed Sargassum have been accumulating in the Great Atlantic Sargassum Belt (GASB), acting as a source of Sargassum strandings on shores of the Caribbean, Brazil, western Africa and parts of the Gulf of Mexico. Quantifying holopelagic Sargassum biomass in this large region is challenging and has relied primarily on satellite imaging providing synoptic estimates of surface coverage, but with limited ground-truthing or understanding of carbon export to the seafloor. Here we provide an in-situ estimate of the amount of holopelagic Sargassum biomass from the surface to the seafloor using data collected during a summer 2024 research expedition from Guadeloupe to Cape Verde through the GASB. We used satellite imagery linked to shipboard camera surveys of surface coverage, measurement of biomass inside mats, sub-surface traps to quantify sinking Sargassum, and tethered camera surveys to quantify the amount of Sargassum reaching the sea floor. Elemental analyses of selected Sargassum samples allow us to provide an estimate of the amount of carbon that Sargassum mats sequester and how much of this carbon is exported to the sea floor.

Presentation Preference: Oral

Primary Presenter: Linda Amaral Zettler, NIOZ Royal Netherlands Institute for Sea Research / Univ. of Amsterdam, Netherlands (linda.amaral-zettler@nioz.nl)

Authors:

Linda Amaral-Zettler, NIOZ Royal Netherlands Institute for Sea Research / University of Amsterdam  (linda.amaral-zettler@nioz.nl)

Magalie Baudrimont, University of Bordeaux  (magalie.baudrimont@u-bordeaux.fr)

Sam van Duivenvoorde, NIOZ Royal Netherlands Institute for Sea Research / Vrije Universiteit Amsterdam  (sam.vanduivenvoorde@gmail.com)

Mar Fernandez-Mendez, Alfred Wegener Institute for Marine and Polar Research  (mar.fernandez-mendez@awi.de)

Elizabeth Gower, Massachusetts Institute of Technology - Woods Hole Oceanographic Institution Joint Program  (elizabeth.gower@whoi.edu)

Marine Guilbaud, University of Bordeaux  (marine.guilbaud@etudiant.univ-lr.fr)

Débora Héroin, University of Bordeaux  (debora.heroin@u-bordeaux.fr)

Chuanmin Hu, University of South Florida  (huc@usf.edu)

Eden Magaña, National Autonomous University of Mexico  (eden.maga@cmarl.unam.mx)

Darshika Manral, Utrecht University  (d.manral@uu.nl)

Dennis McGillicuddy, Woods Hole Oceanographic Institution  (dmcgillicuddy@whoi.edu)

Anna Michel, Woods Hole Oceanographic Institution  (amichel@whoi.edu)

Furu Mienis, NIOZ Royal Netherlands Institute for Sea Research  (furu.mienis@nioz.nl)

Fabio Nauer, NIOZ Royal Netherlands Institute for Sea Research  (fabio.nauer@nioz.nl)

Pierre-Yves Pascal, University of the Antilles  (pierreyves.pascal@gmail.com)

Julia Schnetzer, Alfred Wegener Institute for Marine and Polar Research  (jschnetzer@gmail.com)

Erik van Sebille, Utrecht University  (e.vansebille@uu.nl)

Jesser de Souza-Filho, Federal University of Pernambuco  (jesser.fidelis@gmail.com)

Jan-Berend Stuut, NIOZ Royal Netherlands Institute for Sea Research / Vrije Universiteit Amsterdam  (jan-berend.stuut@nioz.nl)

Sully Sullivan, University of South Florida  (sarahgsully@gmail.com)

Brigitta van Tussenbroek, National Autonomous University of Mexico  (vantuss@cmarl.unam.mx)

Juliane Vasconcelos, Federal University of Pernambuco  (bernardijuliane@gmail.com)

Robin de Vries, The Ocean Cleanup  (robin.devries@theoceancleanup.com)

Leon Wuis, NIOZ Royal Netherlands Institute for Sea Research  (leon.wuis@nioz.nl)

Erik Zettler, NIOZ Royal Netherlands Institute for Sea Research  (erik.zettler@nioz.nl)