The dataset includes the porewater, surface water, and sediment geochemical data associated with the publication The unique biogeochemical role of carbonate-associated organic matter in a subtropical seagrass meadow Communications Earth and Environment, 2024. Modern surficial sediment cores (25 to 35 cm in length) were collected for porewater and sediment geochemical analysis at Bob Allen Keys, Florida Bay, USA on November 12, 2019. These sediment cores were collected from regions of relatively high and relatively low seagrass density (HD and LD, respectively), with seagrass biomass included in the sediment cores, and were collected as push cores 10 cm inner diameter. For solid phase analysis, one core was collected per seagrass density. For porewaters, 2 cores with drilled rhizon holes were collected per seagrass density. Solid phase data includes the total inorganic carbon content, the total organic carbon content, the atomic total organic carbon to total nitrogen ratio, and the delta-34 S stable isotopic value of chromium reducible sulfur. Porewater data includes the dissolved iron concentration, the delta-34 S stable isotopic value of dissolved sulfide and sulfate, and the delta-18 O stable isotopic value of sulfate. Additional samples were collected from the outlet of the Taylor Slough river, surface waters and porewater from Bob Allen (collected with a porewater sipper) for dissolved organic carbon concentration and delta-13 C composition, as well as absorbance at 254 nm. The data was collected to address the question of whether seagrass presence could contribute to increased sulfide oxidation in addition to increased sulfurization of organic matter, and whether this sulfide oxidation would lead to connectivity between particulate carbonate-associated organic matter and the dissolved organic matter pool. Molecular analysis of this dissolved organic matter and carbonate-associated organic matter (via FT ICR MS) which is also associated with the scientific publication is provided via open science framework (https://osf.io.vphzr/ at DOI 10.17605/OSF.IO/VPHZR). The sediment cores were also used for additional measurements published on Figshare (https://doi.org/10.6084/m9.figshare.16852792.v1).
