Rapid microbial activity in marine sediments significantly enhances silica cycling rates compared to abiotic processes

Silicon, earth’s second most abundant element, cycles via biogeochemical processes in terrestrial and oceanic environments. The marine sediment-water interface is thought to divide biological-dominated (water) from abiotic-dominated (sediment) silica cycling processes. Studies indicate marine extremophile bacteria induce silica precipitation, but the quantitative importance of microorganisms in broader sediment silica cycling remains unexplored. We hypothesize that microorganisms significantly influence sediment silica cycling, challenging the prevailing divide of microbial importance. Within hours, sediment microbes expedited silica sequestration through rapid coupled dissolution/reprecipitation processes in marine deltaic sediment experiments. Using radiotracer silicon-32, we reveal that microbial mediation enhanced silica uptake, surpassing abiotic uptake by 3.6-fold in dilute suspensions (silica < 100 μM) and 3.4-fold in surface sediment porewater simulations. We assert that microorganisms drive significant diagenetic silica cycling rates, facilitating authigenic silica precipitation through previously reported mechanisms from microscopy analysis. This unifies the critical role of microorganisms in Si cycling to both marine pelagic waters and surface sediments. Microbial activity significantly enhances silica cycling rates in marine sediments, surpassing abiotic processes through rapid dissolution and reprecipitation, according to incubation experiments in sediments from the Congo Deep Sea Fan and Mississippi River Plume