Reservoirs are crucial carbon sinks that rely on carbon sedimentation and sequestration exceeding CO₂ and CH₄ emissions. Acid polysaccharides (APs) released by phytoplankton and bacteria promote carbon sedimentation by coagulating into particulates that are exported towards sediments when ballasted by minerals or detritus. The Mediterranean region experiences seasonal fluctuations that influence biological productivity in reservoirs, such as Saharan dust deposition. Despite the importance of carbon sedimentation, there is limited research on the factors driving this process. This study identifies the main drivers behind the sedimentation of APs and particulate organic carbon (POC) in a eutrophic Mediterranean reservoir and infers the degree of synchrony between these drivers and carbon sedimentation. Results indicate a marked seasonality in APs and POC sedimentation, with the highest levels occurring in summer and fall associated with biological productivity. APs sedimentation ranged from 7.23 to 849.30 mg C m^-2 d^-1, and POC sedimentation ranged from 30.28 to 1327.70 mg C m^-2 d^-1. The POC and APs sedimentation are synchronized, while Saharan dust deposition and chlorophyll-a promote POC sedimentation with a four-week time lag. APs sedimentation is synchronized with cyanobacteria abundance, divalent cations with a two-week lag, and prokaryotic abundance with a four-week time lag. These findings highlight the importance of acidic polysaccharides in promoting carbon export to sediments and the complex interplay of biotic and chemical factors.

Primary Presenter: Andres Martinez-Garcia, University of Granada (andresmartinezgarcia2@gmail.com)

Authors:

Andrés Martínez-García, University of Granada/ Escuela de Doctorado de Ciencias, Tecnologías e Ingenierías (EDCTI)  (andmargar@ugr.es)

Ignacio Peralta-Maraver, University of Granada  (peraltamaraver@ugr.es)

Eva Rodríguez-Velasco, peraltamaraver@ugr.es  (erodvel@ugr.es)

Gema Batanero, University of Granada  ()

Míriam García-Alguacil, University of Granada  (mga00043@ugr.es)

Félix Picazo, University of Granada  (fpicazo@ugr.es)

Juan Calvo, University of Granada  ()

Rafael Morales-Baquero, University of Granada  ()

Francisco Rueda, University of Granada  ()

Isabel Reche, University of Granada  (ireche@ugr.es)