Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - SedSulphOx (Quantification of oxidative sulphur cycling in marine sediments)

Teaser

The goal of this project was to measure transformations of different sulphur compounds in marine sediments, particularly sulphide oxidation to sulphate. Sulphide is produced through microbial sulphate reduction, a key process for the remineralisation of organic matter to CO2...

Summary

The goal of this project was to measure transformations of different sulphur compounds in marine sediments, particularly sulphide oxidation to sulphate. Sulphide is produced through microbial sulphate reduction, a key process for the remineralisation of organic matter to CO2 in the seafloor. Understanding this process is societally relevant because fluxes of inorganic carbon and reduced sulphur from the sediments have a profound effect on the oxygen balance and carbon uptake capacity of coastal waters, which in turn plays a role in regulating atmospheric CO2. Moreover, carbon and nutrient loading to coastal waters such as the Baltic Sea are heightened due to human activities. Such conditions lead to eutrophication of the water column and sulphide release from the sediment. Sulphide is toxic to aerobic organisms such as fish, and negatively impacts the water quality. Knowing how much and how quickly sulphur is cycled in coastal sediments is therefore an important component to better understand broader scale carbon cycling and controls on local water quality. Thus, the overall objective of this project was to quantify sulphide oxidation rates in marine sediments.

Work performed

SUMMARY OF WORK PERFORMED:

MAIN RESULTS: The main results of this work are (1) the development of a method for the quantification of sulphide oxidation rates in sediments, (2) improved constraints on the isotopic signatures of sulphur cycling in sediments and natural environments. Please see below for a discussion of the significance of these results.

EXPLOITATION OF RESULTS:
The results of this project have been presented at multiple meetings and published in various scientific journals (full list below)

LIST OF PRESENTATIONS (only where the PI was the presenter):
Findlay A.J. Sulphide oxidation and intermediate turnover in the environment: Moving towards a more complete description of the environmental sulphur cycle. Invited Keynote presentation, Goldschmidt, August 2018.

Findlay A.J. Biogeochemistry of intermediate sulphur species. International Symposium on Microbial Sulfur Metabolism, April 2018.

This work was also presented by collaborators at Goldschmidt in 2017 and 2018, and by the PI at four departmental seminars at Aarhus University

LIST OF PUBLICATIONS
UNDER REVIEW:
Findlay A.J., Pellerin A., Laufer K., Jørgensen B.B. Quantification of sulphide oxidation rates in sediment. Submitted to Geochim Cosmochim Acta. In revision.

Michaud A., Laufer K., Findlay A.J., Pellerin A., Antler G., Turchyn A.V., Røy H., Jørgensen B.B. Sulfide oxidation in the glacially influenced fjords of western Spitsbergen, Svalbard. Submitted to Geochim Cosmochim Acta. In revision.

PUBLISHED:
Gartman A., Findlay A.J., Hannington M., Garbe-Schönberg D., Jamieson J.W., Kwasnitschka T. (in press) The role of nanoparticles in mediating element deposition and transport at hydrothermal vents. Geochim Cosmochim Acta

Pellerin A., Antler G., Holm S.A., Findlay A.J., Crockford P., Turchyn A., Jørgensen B., Finster K. (2019) Large sulfur isotope fractionation by bacterial sulfide oxidation. Science Advances. 5:eaaw1480

Findlay A.J., Boyko V., Pellerin A., Avetisyan K., Guo Q., Yang X., Kamyshny A. (2019). Sulfide oxidation affects the preservation of sulfur isotope signals. Geology. doi:10.1130/G46153.1

Findlay A.J., Estes E., Gartman A., Yücel M, Kamyshny Jr. A., Luther III G.W. (2019) Iron and sulfide (nano)particle formation and transport in nascent hydrothermal vent plumes. Nat Commun. 10:1597.

Jørgensen B.B., Findlay A.J., Pellerin A. (2019) The biogeochemical sulfur cycle of marine sediments. Frontiers Microbiol. doi:10.3389/fmicb.2019.00849

Wurgarft E., Findlay A.J., Viderovich H., Herut B., Sivan O. (2019) Sulfate reduction rates in the sediments of the Mediterranean continental shelf from combined dissolved inorganic carbon and total alkalinity profiles. Mar Chem. 211, 64-74.

Pellerin A., Antler G., Røy H., Findlay A.J., Beulig F., Turchyn A.V., Jørgensen B.B. (2018) Placing an upper limit on the cryptic sulfur cycle below the sulfate methane transition zone of Baltic Sea sediments. Geochim Cosmochim Acta 329, 74 – 89.

Final results

This project addressed several fundamental questions of the sulphur cycle, which had not been answered by any previous study. The main objective of this project, namely the development and testing of a method to determine sulphide oxidation rates in marine sediments, represents a major step forward in sediment biogeochemistry. It has been known for decades that sulphide is oxidized in sediments, but the rates were unconstrained. We have measured rates for the first time and provided a method that can be reproduced and broadly applied. This work has also led to a deepened understanding of the energy available for carbon degradation in the deep biosphere, which we showed is lower than previously thought.

Findlay A.J., Pellerin A., Laufer K., Jørgensen B.B. Quantification of sulphide oxidation rates in sediment. Submitted to Geochim Cosmochim Acta. In revision.

Pellerin A., Antler G., Røy H., Findlay A.J., Beulig F., Turchyn A.V., Jørgensen B.B. (2018) Placing an upper limit on the cryptic sulfur cycle below the sulfate methane transition zone of Baltic Sea sediments. Geochim Cosmochim Acta 329, 74 – 89.

We have also constrained oxidative sulphur cycling in Arctic sediments, where the balance of processes responsible for carbon degradation to CO2 (including microbial sulphate reduction) is changing due to glacier melting. This work helped bound the importance of microbial sulphate reduction for the carbon cycle in these sediments.

Michaud A., Laufer K., Findlay A.J., Pellerin A., Antler G., Turchyn A.V., Røy H., Jørgensen B.B. Sulfide oxidation in the glacially influenced fjords of western Spitsbergen, Svalbard. Submitted to Geochim Cosmochim Acta. In revision.

Work on this project has also advanced our understanding of stable sulphur isotope distributions. Stable sulphur isotope distributions are widely used to reconstruct biogeochemical processes on the modern Earth, as well as reconstruct past ocean and atmospheric chemistry. The isotopic signature of sulphide oxidation is not well understood, yet affects these interpretations. In particular, we have shown that isotopic signatures previously thought to indicate low amounts of sulphur cycling, and therefore low atmospheric oxygen concentrations, are also consistent with sulphide oxidation. This means that oxygen may have been more important on Earth\'s surface earlier than previously thought.

Pellerin A., Antler G., Holm S.A., Findlay A.J., Crockford P., Turchyn A., Jørgensen B., Finster K. (2019) Large sulfur isotope fractionation by bacterial sulfide oxidation. Science Advances. 5:eaaw1480

Findlay A.J., Boyko V., Pellerin A., Avetisyan K., Guo Q., Yang X., Kamyshny A. (2019). Sulfide oxidation affects the preservation of sulfur isotope signals. Geology. doi:10.1130/G46153.1

Website & more info

More info: http://pure.au.dk/portal/en/persons/alyssa-jean-lehsau-findlay.