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The silicon cycle at “la Méthode Scientifique” radio program, May 5, 2021 at 4pm

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Silicon. Why should we be interested in this element? Because it is particularly abundant in the form of silica and silicate minerals on the planet Earth and on other terrestrial planets (Mercury, Venus, Mars). If on Earth living organisms are based on the carbon cycle, essential organisms of marine life (diatoms, radiolarians, a good part of sponges, …) require silicon to build their internal or external structures. Without silicon, the biological carbon pump loses much of its efficiency. What are the sources and sinks of silicon in the ocean? What is the production of biogenic silica in the ocean? How is the silicon cycle evolving in response to climate change and anthropogenic perturbations?

These are the questions that Paul Tréguer (LEMAR, IUEM-UBO) answered on France Culture, during the program “La Méthode Scientifique” on Wednesday, May 5, at 4:00 pm, a program to which Anne Alexandre (CEREGE, CNRS) was also invited.

 

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Radiolarians and the silicon cycle: Natalia Llopis-Monferrer’s work in the spotlight!

The American Geophysical Union (AGU) has declared “Research Spotlight” the recent article by Natalia Llopis-Monferrer in “Global Biogeochemical Cycles” on the importance of radiolarians (marine planktonic organisms) in the silicon cycle of the world ocean.

This recent work re-evaluates the role of these tiny protists, which could contribute up to one-fifth of the world’s silica production by marine organisms.

Natalia Llopis-Monferer is a spanish student at LEMAR (UMR 6539). She is co-supervised by Aude Leynaert (CNRS), Fabrice Not (SBR) and Paul Tréguer (UBO).

Read the “EOS” article (Sciences News by AGU)

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Sponge skeletons as an important sink of silicon in the global oceans

Silicon (Si) is a pivotal element in the biogeochemical and ecological functioning of the ocean. The marine Si cycle is thought to be in internal equilibrium, but the recent discovery of Si entries through groundwater and glacial melting have increased the known Si inputs relative to the outputs in the global oceans. Known outputs are due to the burying of diatom skeletons or their conversion into authigenic clay by reverse weathering. Here we show that non-phototrophic organisms, such as sponges and radiolarians, also facilitate significant Si burial through their siliceous skeletons. Microscopic examination and digestion of sediments revealed that most burial occurs through sponge skeletons, which, being unusually resistant to dissolution, had passed unnoticed in the biogeochemical inventories of sediments. The preservation of sponge spicules in sediments was 45.2 ± 27.4%, but only 6.8 ± 10.1% for radiolarian testa and 8% for diatom frustules. Sponges lead to a global burial flux of 1.71 ± 1.61 TmolSi yr−1 and only 0.09 ± 0.05 TmolSi yr−1 occurs through radiolarians. Collectively, these two non-phototrophically produced silicas increase the Si output of the ocean to 12.8 TmolSi yr−1, which accounts for a previously ignored sink that is necessary to adequately assess the global balance of the marine Si cycle.

References

Maldonado, M., López-Acosta, M., Sitjà, C., García-Puig, M., Galobart, C., Ercilla, G., & Leynaert, A. (2019). Sponge skeletons as an important sink of silicon in the global oceans. Nature Geoscience. https://doi.org/10.1038/s41561-019-0430-7

 

Read the publication

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The Silicon Cycle: The Forgotten Silicified

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Le cycle du silicium est une thématique historique du LEMAR qui possède une forte visibilité internationale grâce à notre implication dans les programmes et consortium internationaux comme BioGeoSCAPES, IMBER, IODP, GEOTRACES, OPALEO, PAGES et SILICAMICS. Nous avons développé une approche transdisciplinaire, incluant la chimie, la biogéochimie, la paléo-océanographie, la biochimie, la physiologie, la biologie et, nouvellement, la génomique. Nous utilisons par ailleurs différents outils expérimentaux et de modélisation et des approches multi-échelles, depuis des expériences au laboratoire qui permettent de mieux comprendre les processus influençant le cycle du Si jusqu’à de grandes campagnes internationales d’observation du milieu naturel. Le «Si-group» a initié en 2015 le cycle de conférences internationales SILICAMICS autour du rôle des organismes silicifiants dans le fonctionnement des écosystèmes marins et dans les cycles biogéochimiques océaniques. SILICAMICS s’est poursuivie au Canada en 2018, et une 3 ème édition est en préparation en Chine (2021). Suite à ces conférences, l’article de Nature Geoscience (Tréguer et al., 2018) combine les compétences d’experts en physique, biogéochimie, génomique et modélisation pour faire le point sur l’efficacité d’export des diatomées ; l’issue spéciale de Frontiers in Marine Science (Moriceau et al. 2019) rassemble 12 articles couvrant les thèmes de SILICAMICS et deux ANRs (BIOPSIS et RADICAL) ont vu le jour, mettant en évidence la nécessité de réévaluer le rôle des silicifiés oubliés dans le cycle du Si (voir AR2.2 CHIBIDO). Ces épisodes ont de plus été moteurs dans la création d’un consortium puis d’une école internationale et cours en ligne (Silica School) réunissant 31 instituts de recherche de 12 pays. De nombreux chercheurs invités régulièrement au LEMAR garantissent le dynamisme et la visibilité de cette thématique du LEMAR au niveau international.

 

Pour en savoir plus :

Le cycle du silicium dans l’océan moderne : https://www-iuem.univ-brest.fr/cycle-du-silicium-dans-locean/

Research topic dans Frontiers in Marine Sciences: Biogeochemistry and Genomics of Silicification and Silicifiers

New Recognition for Major Players in the Ocean’s Silicon Cycle

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Role of complex trophic interactions in biogeochemical cycles

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Noctiluca scintillans variashttp://planktonnet.awi.de (provided under a Creative Commons Attribution 3.0 License)

In the ocean, trophic interactions between individuals are still mainly represented in a predator-prey pattern. However, meta-analyses of taxonomic co-occurrences, made possible by advances in molecular biology, suggest that many planktonic organisms are involved in complex interactions ranging from facultative predation to symbiosis to mutualism. While these relationships appear to be the rule rather than the exception in the ocean, research efforts are focused on a few emblematic examples. In CHIBIDO, we are trying to identify new interactions and are particularly interested in mixotrophic organisms (both phototrophic and phagotrophic), the trophic mode of the majority of dinoflagellates, and in diazotrophs that often live in symbiosis with other organisms. To better understand the role of trophic interactions on biogeochemical cycles (especially nitrogen and carbon), it is necessary to couple tools.

The team is internationally recognised for its expertise in the use of 13 C and 15 N stable isotopes to quantify oceanic fluxes. In recent years, it has coupled this approach with new tools (e.g. nanoSIMS or flow cytometry sorting) that make it possible to visualise and quantify fluxes between the environment and organisms and/or between organisms.

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Tag Archive for: silicon cycle

Glass

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RadiCal

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GreenEdge

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BIOPSIS

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Tag Archive for: silicon cycle

Lucie CASSARINO

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