The coupling between benthic and pelagic processes plays a fundamental role in marine biogeochemistry since the oceans’ nutrient and carbon inventories are regulated by fluxes across the sediment-seawater interface which are driven by the rain of pelagic material to the seabed and modulated by the chemical composition of ambient bottom waters. The modes and mechanisms of this benthic-pelagic coupling are poorly understood. Moreover, the ongoing anthropogenic perturbation of the natural system affects not only the surface ocean but also the seabed and the biogeochemical fluxes between these two environments. Ocean acidification, deoxygenation and warming will thus induce major changes in benthic element cycling via various direct and indirect effects.
Against this background, the research unit Marine Geosystems studies benthic fluxes across the seabed to better understand the mechanisms of benthic-pelagic coupling and their sensitivity to natural and anthropogenic change. Benthic flux chambers, eddy-correlation techniques, profiling micro-electrodes, in-situ pore water sampling, sediment coring, on-board pore water separation and further sea-going techniques are applied to quantify these fluxes.
Biogeochemical processes at the seafloor in permanently or seasonally oxygen deficient areas are research topics within the SFB 754 ”Climate - Biogeochemistry Interactions in the Tropical Ocean” (http://www.sfb754.de/en/?). Research unit Marine Geosystems covers most of benthic work in SFB 754. Nutrient cycling in the sediments and the benthic boundary layer is quantified by combining field data, including nutrient fluxes determined in situ, with numerical reaction-transport models. The aim of these projects is to provide a greater understanding of the role of sediments in moderating water column elemental budgets in oxygen deficient environments, with an emphasis on phosphorus, nitrogen and iron cycling. The field data is ultimately used to derive vertically-integrated benthic models which can be coupled to general circulation models to assess the importance of the benthos in global ocean biogeochemistry.