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Prokaryotic activity in dark ocean mixing zones (PADOM)

Frontal systems in the surface layer of the ocean are well known for their elevated biological activity. Such boundary systems, however, are not only detectable as vertical boundary layers in the surface ocean, but may also exist in the deeper layers of the ocean as mixing zones of water masses. These deep ocean fronts or ecotones might be particularly important at ocean ridges, canyons and fracture zones. Based on preliminary measurements, we hypothesize that mixing of deep-water masses create ‘hot-spots’ in prokaryotic diversity and activity with a significant influence on the overall biogeochemical cycles of the dark ocean, similarly to the well studied ecotones. Prokaryotic activity in the mixing zone and the parent water masses of the Charlie-Gibbs Fracture Zone in the North Atlantic will be assessed by determining heterotrophic biomass production, ectoenzyme activity and respiration as well as gene expression. Collectively, these data should allow for an in-depth view on the heterogeneity of prokaryotic organic matter cycling in the deep ocean by shedding light on the microbial ecology of deep-water boundary layers. As these mixing zones of major water masses are abundant, they might significantly stimulate overall matter cycling in the dark ocean.

PI: Thomas Reinthaler
PhD Student in project: Alexander Frank