Hailey-Hannah Cottet

Biogeochemistry Group

MPI for Marine Microbiology
Celsiusstr. 1
D-28359 Bremen




+49 421 2028-6537

Hailey-Hannah Cottet

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Seagrasses evolved from terrestrial flowering plants approximately 100 million years ago and are adapted to a fully submerged lifestyle in saltwater. Like many other seagrasses, the Mediterranean seagrass Posidonia oceanica thrives despite nitrogen-limited conditions. The high productivity of these so-called ‘blue carbon’ ecosystems suggests that seagrasses have developed various traits to counteract nitrogen limitation. One major trait is the association with N2-fixing microorganisms that convert inert N2 gas into bioavailable ammonia and hence make it available to the plant.

My research aim is to better understand the nutrient acquisition strategies, particularly N2 fixation, in seagrass habitats as well as their role in the export and burial of carbon in these ecosystems.

Main techniques:

  • Stable isotope incubations of different plant tissues to quantify bulk N2 fixation and CO2 fixation rates using elemental analysis and mass spectrometry
  • Analysis of metagenomes and metatranscriptomes to elucidate the identity and abundance of N2-fixing microorganisms and inferring metabolic capacities and interactions
  • Correlative microscopy and single-cell activity measurements using nanoSIMS to visualize and assess the activity of the N2-fixers
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