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Dr. Hannah Marchant


Biogeochemistry Group

MPI for Marine Microbiology
Celsiusstr. 1
D-28359 Bremen




+49 421 2028-6306

Dr. Hannah Marchant

My research focuses on the microbial ecology and biogeochemistry of coastal sediments, encompassing beaches, intertidal flats and the subtidal sediments of the continental shelves. These environments are disproportionately affected by anthropgenic activities which leads to coastal erosion, sea-level rise, warming and eutrophication. Therefore, I am particularly passionate about not only deciphering the cycling of carbon and nutrients in these sediments, but linking such transformations to the microorganisms that carry them out. It is only by examining both that we will be able to predict the responses of coastal sediments to continuing climatic pressure.

I largely focus on sandy sediments, as these cover the vast majority of the continental shelves. Unlike muds, sands are permeable in nature. As a result, the interaction between sediment topography (in the form of small ripples) and bottom water movement causes advective flow of porewater within sands, supplying and removing electron donors and acceptors at velocities orders of magnitude higher than diffusion. This enhanced porewater supply, combined with apparently highly adapted microbial communities, leads to intense biogeochemical cycling and activity in sandy permeable sediments. As a result they can act as a biocatalytic filter, removing anthropogenic pollutants such as nitrate from the coastal zone and reducing it to inert dinitrogen gas.

Research interests

  • Nitrogen cycling rates and microbial communities in sandy sediments; from beaches to the shelf break
  • The influence of dynamic redox conditions on nitrogen cycling communities
  • Nitrogen cycling pathways, oxygen dynamics and the fate of DOM at sites of groundwater seepage and within the seawater recirculation zone on beaches
  • The impact of nutrient and carbon degradation in shelf sediments on material laterally advected to the open ocean and deep seafloor


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