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Organisation d’une session du Congrès Future Earth 2 IMBER Open Science Conference

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Bernard Quéguiner (MIO) co-organise une session spéciale "The Multiple Pathways of the Biological Pump" dans le cadre du congrès Future Earth 2 IMBER Open Science Conference qui se tiendra à Brest du 16 au 21 juin 2019. Plus d’informations sur le site web du congrès http://www.imber.info/en/events/osc/2019 (remise des abstracts avant le 1er décembre 2018, inscriptions anticipées jusqu’au 31 mars 2019, inscriptions au plein tarif jusqu’au 15 mai 2019)

The Multiple Pathways of the Biological Pump

Conveners : Frédéric Planchon (LEMAR), Clara Manno (BAS), Bernard Quéguiner (MIO), Emmanuel Laurenceau-Cornec (ACE-CRC), Anna Belcher (BAS), Stephanie Henson (NOC)

The Biological Carbon Pump (BCP), the transfer to the deep sea of organic carbon fixed at the surface by marine organisms, is a key driver of atmospheric CO2 levels and an essential component of Earth climate. Despite substantial advances made during the past decades, our understanding of the magnitude and variability of the BCP remains limited. Global-scale model estimates of surface carbon export are still largely divergent (range from 5 to 13 Pg C yr-1) and have an uncertainty range that is as large as the total amount of CO2 emitted annually by anthropogenic activities. Reducing this uncertainty represents a major scientific challenge and is required to infer realistic predictions of the global carbon cycle, and by extension, of climate change.

Understanding needs to be improved first at the process level. How organic carbon produced by autotrophic organisms is transferred at depth, reprocessed by heterotrophic food webs, and/or transferred through pelagic food webs up to top predators is still an open question. It is now well assumed that bacterial degradation, along with phytoplankton community structure, and assimilation/excretion by zooplanktonic organisms (including high trophic levels such as fish and/or gelatinous organisms) are important processes to consider. But, how does the heterotrophic community structure control the fate of carbon in the mesopelagic zone, and can we quantify this ? For instance, zooplankton can perform large vertical migrations and actively transport carbon downwards through respiration and the production of fast sinking faecal pellets, but they can also consume and respire sinking particles.

This session will also focus at the observational level. Despite numerous and comprehensive field studies, large regions of the global ocean still remain severely under-sampled precluding a comprehensive view of the spatio-temporal variability of the surface and deep carbon export. This is particularly true for the Southern and Indian Oceans, which have received disproportionally low attention in comparison to other oceanic regions. Methodologies to study carbon fluxes have greatly improved in recent years. The advent of new generation instruments such as autonomous profilers or in situ optical imaging systems have allowed to reach unprecedented details on the characteristics of the sinking particle flux. What did we learn by implementing these new methodologies ? Do these techniques compare with classical methods (moored/free-drifting sediment traps, marine snow catchers, radiotracers, nutrients/DIC budgets) ? These are among the questions we would like to address during this session. We encourage submissions of field, experimental and modelling studies that have been carried out recently and focused on the general topic of the BCP.