Sedimentary Pyrite Formation in a Seasonally Oxygen‐Stressed Estuary: Potential Imprints of Microbial Ecology and Position‐Specific Isotope Fractionation

Sedimentary pyrite records are essential for reconstructing paleoenvironmental conditions, but these may be affected by seasonal fluctuations in oxygen concentration and temperature, which can impact bioturbation, sulfide fluxes, distributions of oxidizing microbes (SOMs). To investigate how stress influences surficial (<2 cm) formation, we measured time-series concentrations sulfur isotope (δ34S) compositions along with those potential precursor compounds at a bioturbated shoal site an oxygen-deficient channel Chesapeake Bay. We also radioisotope depth profiles to estimate sedimentation rates bioturbation intensities. Results show that net precipitation was restricted summer early autumn both sites. Pyrite higher apparently more responsive compound the mildly than non-bioturbated site. This disparity driven differences dominant SOM communities between two Despite this, sites' similar δ34S values imply changes have limited effects on here. However, found consistently anomalously lower coeval A steady-state model demonstrates equilibrium position-specific fractionation (PSIF) S8-polysulfide pool create 4.3–7.3‰ gap zero-valent sulfur. study suggests distinct accumulation seasonally dynamic systems, PSIF polysulfide leave imprint records.