Anoxia-Related Biogeochemistry of North Indian Ocean

Complex interactions between microbial communities and geochemical processes drive the major element cycles control function of marine sediments as a dynamic reservoir organic matter. Sulfate reduction is globally dominant pathway anaerobic mineralisation main source sulfide. The effective re-oxidation this sulfide at direct or indirect expense oxygen prerequisite for aerobic life on our planet. Although largely hidden beneath oxic sediment surface, sulfur cycle therefore critical Earth’s redox state. This Geochemical Perspectives begins with brief primer description my own scientific journey through nearly fifty years studies geochemistry microbiology. Among objectives these were to quantify identify behind them. Radiotracers in combination chemical analyses have thereby been used extensively laboratory experiments, supported by diverse molecular microbiological methods. following sections discuss sulfate reduction, oxidation disproportionation inorganic intermediates, especially elemental thiosulfate. experimental approaches enable analysis how environmental factors such substrate concentration temperature affect process rates concurrent cryptic cycle. energy chemolithotrophic bacteria, including fascinating big bacteria cable supports their dark CO2 fixation, which produces new biomass. During burial aging sediments, predominant change cascade reactions, rate matter degradation drops continuously over many orders magnitude. pathways age turnover are discussed. In deep methanic zone, only few percent entire remains, provides small boost methane oxidation. stable isotopes provide an additional tool understand diagenetic processes, whereby isotope fractionation open system diagenesis generate differential diffusion flux isotopes. relation carbon seabed contribution methane, paper discusses global budget role different depth regions ocean - from coast sea. published estimates parameters evaluated compared. Finally, looks future perspectives respect gaps current understanding need further studies.