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Sedimentary pyrite sulfur isotope compositions preserve signatures of the surface microbial mat environment in sediments underlying low-oxygen cyanobacterial mats.
Geobiology. 2022 01; 20(1):60-78.G

Abstract

The sedimentary pyrite sulfur isotope (δ34 S) record is an archive of ancient microbial sulfur cycling and environmental conditions. Interpretations of pyrite δ34 S signatures in sediments deposited in microbial mat ecosystems are based on studies of modern microbial mat porewater sulfide δ34 S geochemistry. Pyrite δ34 S values often capture δ34 S signatures of porewater sulfide at the location of pyrite formation. However, microbial mats are dynamic environments in which biogeochemical cycling shifts vertically on diurnal cycles. Therefore, there is a need to study how the location of pyrite formation impacts pyrite δ34 S patterns in these dynamic systems. Here, we present diurnal porewater sulfide δ34 S trends and δ34 S values of pyrite and iron monosulfides from Middle Island Sinkhole, Lake Huron. The sediment-water interface of this sinkhole hosts a low-oxygen cyanobacterial mat ecosystem, which serves as a useful location to explore preservation of sedimentary pyrite δ34 S signatures in early Earth environments. Porewater sulfide δ34 S values vary by up to ~25‰ throughout the day due to light-driven changes in surface microbial community activity that propagate downwards, affecting porewater geochemistry as deep as 7.5 cm in the sediment. Progressive consumption of the sulfate reservoir drives δ34 S variability, instead of variations in average cell-specific sulfate reduction rates and/or sulfide oxidation at different depths in the sediment. The δ34 S values of pyrite are similar to porewater sulfide δ34 S values near the mat surface. We suggest that oxidative sulfur cycling and other microbial activity promote pyrite formation in and immediately adjacent to the microbial mat and that iron geochemistry limits further pyrite formation with depth in the sediment. These results imply that primary δ34 S signatures of pyrite deposited in organic-rich, iron-poor microbial mat environments capture information about microbial sulfur cycling and environmental conditions at the mat surface and are only minimally affected by deeper sedimentary processes during early diagenesis.

Authors+Show Affiliations

Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD, USA.Microsensor Group, Max Planck Institute for Marine Microbiology, Bremen, Germany. Department of Earth and Environmental Science, University of Michigan, Ann Arbor, MI, USA.Department of Earth and Environmental Science, University of Michigan, Ann Arbor, MI, USA.Department of Earth and Environmental Science, University of Michigan, Ann Arbor, MI, USA. Exobiology Branch, National Aeronautics and Space Administration Ames Research Center, Mountain View, CA, USA.Department of Earth and Environmental Science, University of Michigan, Ann Arbor, MI, USA. Department of Earth and Planetary Sciences, McGill University, Montreal, QC, Canada.Department of Earth and Environmental Science, University of Michigan, Ann Arbor, MI, USA.Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA.Department of Biological Sciences, Kent State University, Kent, OH, USA.Department of Earth and Environmental Science, University of Michigan, Ann Arbor, MI, USA.Department of Earth and Planetary Sciences, Washington University, Saint Louis, MO, USA.

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

34331395

Citation

Gomes, Maya L., et al. "Sedimentary Pyrite Sulfur Isotope Compositions Preserve Signatures of the Surface Microbial Mat Environment in Sediments Underlying Low-oxygen Cyanobacterial Mats." Geobiology, vol. 20, no. 1, 2022, pp. 60-78.
Gomes ML, Klatt JM, Dick GJ, et al. Sedimentary pyrite sulfur isotope compositions preserve signatures of the surface microbial mat environment in sediments underlying low-oxygen cyanobacterial mats. Geobiology. 2022;20(1):60-78.
Gomes, M. L., Klatt, J. M., Dick, G. J., Grim, S. L., Rico, K. I., Medina, M., Ziebis, W., Kinsman-Costello, L., Sheldon, N. D., & Fike, D. A. (2022). Sedimentary pyrite sulfur isotope compositions preserve signatures of the surface microbial mat environment in sediments underlying low-oxygen cyanobacterial mats. Geobiology, 20(1), 60-78. https://doi.org/10.1111/gbi.12466
Gomes ML, et al. Sedimentary Pyrite Sulfur Isotope Compositions Preserve Signatures of the Surface Microbial Mat Environment in Sediments Underlying Low-oxygen Cyanobacterial Mats. Geobiology. 2022;20(1):60-78. PubMed PMID: 34331395.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Sedimentary pyrite sulfur isotope compositions preserve signatures of the surface microbial mat environment in sediments underlying low-oxygen cyanobacterial mats. AU - Gomes,Maya L, AU - Klatt,Judith M, AU - Dick,Gregory J, AU - Grim,Sharon L, AU - Rico,Kathryn I, AU - Medina,Matthew, AU - Ziebis,Wiebke, AU - Kinsman-Costello,Lauren, AU - Sheldon,Nathan D, AU - Fike,David A, Y1 - 2021/07/31/ PY - 2020/12/21/received PY - 2021/07/10/accepted PY - 2021/8/1/pubmed PY - 2022/3/1/medline PY - 2021/7/31/entrez KW - geomicrobiology KW - microbial mats KW - middle island sinkhole KW - pyrite KW - sulfur isotopes SP - 60 EP - 78 JF - Geobiology JO - Geobiology VL - 20 IS - 1 N2 - The sedimentary pyrite sulfur isotope (δ34 S) record is an archive of ancient microbial sulfur cycling and environmental conditions. Interpretations of pyrite δ34 S signatures in sediments deposited in microbial mat ecosystems are based on studies of modern microbial mat porewater sulfide δ34 S geochemistry. Pyrite δ34 S values often capture δ34 S signatures of porewater sulfide at the location of pyrite formation. However, microbial mats are dynamic environments in which biogeochemical cycling shifts vertically on diurnal cycles. Therefore, there is a need to study how the location of pyrite formation impacts pyrite δ34 S patterns in these dynamic systems. Here, we present diurnal porewater sulfide δ34 S trends and δ34 S values of pyrite and iron monosulfides from Middle Island Sinkhole, Lake Huron. The sediment-water interface of this sinkhole hosts a low-oxygen cyanobacterial mat ecosystem, which serves as a useful location to explore preservation of sedimentary pyrite δ34 S signatures in early Earth environments. Porewater sulfide δ34 S values vary by up to ~25‰ throughout the day due to light-driven changes in surface microbial community activity that propagate downwards, affecting porewater geochemistry as deep as 7.5 cm in the sediment. Progressive consumption of the sulfate reservoir drives δ34 S variability, instead of variations in average cell-specific sulfate reduction rates and/or sulfide oxidation at different depths in the sediment. The δ34 S values of pyrite are similar to porewater sulfide δ34 S values near the mat surface. We suggest that oxidative sulfur cycling and other microbial activity promote pyrite formation in and immediately adjacent to the microbial mat and that iron geochemistry limits further pyrite formation with depth in the sediment. These results imply that primary δ34 S signatures of pyrite deposited in organic-rich, iron-poor microbial mat environments capture information about microbial sulfur cycling and environmental conditions at the mat surface and are only minimally affected by deeper sedimentary processes during early diagenesis. SN - 1472-4669 UR - https://www.unboundmedicine.com/medline/citation/34331395/Sedimentary_pyrite_sulfur_isotope_compositions_preserve_signatures_of_the_surface_microbial_mat_environment_in_sediments_underlying_low_oxygen_cyanobacterial_mats_ L2 - https://doi.org/10.1111/gbi.12466 DB - PRIME DP - Unbound Medicine ER -