Porewater and benthic biogeochemistry
Benthic environments in both marine and lacustrine settings are sites where strong geochemical gradients can be observed. Diffusive fluxes of solutes across the sediment-water interface and reaction rates in these environments are controlled by the organic matter quality and bottom water O2 concentrations. Understanding the role of sediments as either a source or a sink for nutrients (either amplifying or alleviating water column eutrophication) is a prerequisite for establishing reliable nutrient budgets at the ecosystem scale.
Our research aims at quantifying benthic diffusive solute fluxes and reaction rates as function of changing environmental conditions and the reactivity of organic matter in aquatic sediments. Flux rates are assessed using a variety of approaches such as whole core and slurry incubations and porewater geochemical profiling techniques. A particular focus lies on the benthic fluxes and porewater geochemistry of dissolved forms of N, including their isotopologues. We are mainly interested in denitrification and other modes of suboxic N2 and N2O production (with potential links to other element cycles). Our research activities seek, for example, to verify links between seasonal variations in benthic N fluxes and variations in the sedimentary microbial community structure, to understand the net isotope effect of benthic N elimination on the DIN pool in the water body, and to assess the relative importance of benthic versus water column transformation processes for ecosystem-scale N budgets.