On Thursday, May 21 at 13:00, in the salle Egée at MIO, Ronnie N. Glud and Peter Stief, from the HADAL group at Southern Denmark University, will present their work during a special joint seminar.
Salle Egée & Zoom link
The seminars will be held in English. There will be 2 full days of scientific discussion with Ronnie and Peter at MIO on Thursday 21, and at CEREGE on Friday 22, to encourage collaborations between our institutes. If you wish to take part in those discussions, please contact the organisers Christian Tamburini or Olivier Sulpis.
Hoping to see many of you there !
Christian & Olivier
Presentation by Ronnie N. Glud
Ronnie N. Glud will give a presentation about « Life and element cycling in the deepest oceanic realm ».
Abstract : The hadal zone represents the deepest and most scantly explored marine habitat on Earth. The hadal ocean covers >2 million km2 and include 27 long, narrow trench systems, that stretch along tectonic subduction zones. Hadal exploration is challenging, but recent technical advances have provided new possibilities to explore the deep and have drastically enhanced our knowledge on life and biogeochemistry in the deepest oceanic realm.
It has now been documented that trenches act as depocenters for organic material, and they appear to represent globally important sites of carbon sequestration, but at the same time they act as biological hotspots for deep sea life flourishing at extreme hydrostatic pressure. Microbial mineralization rate along trench axes is highly intensified as compared to adjacent abyssal plains, and in the most active trench systems early diagenesis includes the complete redox sequence of anaerobic mineralization known from coastal sediments. The intensified mineralization is mediated at extreme hydrostatic pressure by largely unexplored communities, and preliminary investigations suggest that hadal biomes are distinct but surprisingly diverse. Recent findings also document that trench act as depositories for anthropogenic pollutants and can hold surprisingly high inventories of persistent organic pollutants.
Hadal trenches are unique but highly dynamic deep-sea environment, and their function or importance cannot be understood by extrapolating our insights from the ambient ocean. The presentation will provide an overview on the status of hadal biogeochemical research and discuss the many unresolved questions and paradigms that will spark hadal research in the coming years.
Presentation by Peter Stief
Then, Peter Stief will present his work about « Marine snow under pressure: Successive transformations of diatom aggregates sinking along experimental pressure gradients ».
Abstract : The best described transformation of sinking marine snow particles is their microbial degradation in the surface ocean, which strongly attenuates the vertical carbon flux into the deep ocean. In contrast, the fate of particles reaching the high-pressure environment of the deep ocean remains elusive, in part due to methodological constraints. Here, we introduce rotating pressure cylinders in which the continuous pressure increase experienced by sinking particles can be simulated. Increasing pressure levels gradually inhibit microbial respiration and growth associated with fast-sinking diatom aggregates, suggesting carbon preservation during the descent to the deep ocean. Dissolved organic carbon leaking from diatom aggregates at high pressure levels is consequently still labile and may feed the dissolved organic matter pool of the deep ocean. Pressure incubations of deep-ocean microbial communities reveal their superior carbon mineralization potential compared to surface-ocean microbial communities. Import of relatively labile organic carbon and colonization by pressure-tolerant microbes render the deep ocean a site of active carbon cycling.
