Sulfate reduction is a ubiquitous microbial process and an important pathway for organic matter oxidation in marine sedi-ments;the latter process is referred to as organoclastic sulfate reduction (OSR) [1,2].Yet,microbial sulfate reduction also serves as a methane barrier in marine sediments,preventing the ingress of more than 90％ of the seeping methane,a powerful greenhouse gas,into the ocean through sulfate-driven anaerobic oxidation of methane (AOM) [3,4].Despite of AOM representing an efficient methane sink,large methane release events have been suggested as triggers of extreme climate change in the geological past [5].Sulfate reduction,either in the form of OSR or AOM,produces dis-solved bicarbonate,typically increasing pore-water alkalinity and inducing the formation of authigenic carbonates [6].Authigenic carbonate resulting from sulfate reduction in marine sediments is believed to have played a key role in the carbon cycle in ancient oceans and still does so today [7,8].Therefore,it is crucial to under-stand the global distribution and magnitude of sulfate reduction and its role in oceanic carbon and sulfur cycling.