Spatial variability of biogeochemical processes in the Rhône River prodelta evidenced by DIC, TA and oxygen benthic fluxes.

River-dominated ocean margins (RiOMars) and their benthic compartments play a key role in coastal carbon cycling by coupling high organic matter inputs with intense benthic biogeochemical processing and burial. This data set includes the benthic fluxes of dissolved inorganic carbon (DIC), total alkalinity (TA), and total oxygen uptake (TOU) along a transect influenced by the Rhône River organic matter inputs, providing new insights on sediment-water exchanges and their implications for coastal acidification. Benthic fluxes were measured ex situ with the incubation of sediment cores during two sampling cruises at the end of spring 2018 and 2022. This data set reveals a pronounced biogeochemical offshore gradient along the transect, primarily driven by riverine organic matter inputs. Stations closest to the river mouth exhibit high benthic fluxes of DIC and TA, with fluxes averaging 54 ± 20 mmol m-2 d-1 for DIC, 30 ± 21 mmol m-2 d-1 for TA and 27 ± 14 mmol m-2 d-1 for O2. In contrast, distal offshore stations show much lower fluxes indicating lower biogeochemical recycling of organic matter: 8 ± 3  mmol m-2 d-1 for DIC, -1 ± 2  mmol m-2 d-1 for TA and 9 ± 2  mmol m-2 d-1 for O2.