Project GB2

Biogeochemical processes fueling sub-seafloor life: transformations of C, S, and Fe

K.-U. Hinrichs, T. Ferdelman, M. Friedrich, V. Heuer, S. Kasten
M. Elvert, B. Koch, Y.-S. Lin, J.M. Mogollon, F. Schmidt, M. Zabel

Background

Sub-seafloor sediments harbor a substantial fraction of Earth’s biomass in the form of poorly explored microbial communities. These microbial communities mediate cycles of C, S, Fe, P, and N and influence the chemical speciation of these elements in the ocean. While microbial activity in shallow sediments is mainly controlled by the availability of organic matter and/or dissolved electron acceptors, other, so far unidentified factors appear to impact the activity of the sub-seafloor biosphere. This project seeks to better constrain key biogeochemical mechanisms in the sub-seafloor. To this end, we investigate how sub-seafloor microbes use particle-bound metal oxides for respiration. We want to find out if they can transform complex organic matter into low-molecular-weight compounds that serve as microbial substrates. And we are particularly interested in reactive sulfur species that might play a role for the deep biosphere due to the mechanisms by which they interact with Fe and organic matter.

Back to Geosphere-Biosphere Interactions

Research Questions

Which processes and microorganisms drive the reduction of iron and manganese below the sulfate/methane transition zone (SMTZ)?
To what extent are the reactions of sulfur intermediates with dissolved organic carbon and ferric iron-bearing minerals driven by microbes?
What are the (precursor-product) relationships between the composition of dissolved organic matter (DOM), the formation of terminal substrates, and the biogeochemical regime?
(How) do microorganisms mediate reactions of sulfur intermediates with DOM and ferric iron-bearing minerals and what are the consequences for the mobility of P and N?