{"id":6497,"date":"2019-11-04T10:09:49","date_gmt":"2019-11-04T09:09:49","guid":{"rendered":"https:\/\/www.mio.osupytheas.fr\/fr\/la-nature-du-fer-exporte-joue-un-role-majeur-dans-son-cycle-oceanique\/"},"modified":"2019-11-04T10:09:49","modified_gmt":"2019-11-04T09:09:49","slug":"the-nature-of-the-iron-exported-plays-a-major-role-in-its-oceanic-cycle","status":"publish","type":"post","link":"https:\/\/www.mio.osupytheas.fr\/en\/la-nature-du-fer-exporte-joue-un-role-majeur-dans-son-cycle-oceanique\/","title":{"rendered":"The nature of the iron exported plays a major role in its oceanic cycle"},"content":{"rendered":"
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For the first time, an international team, including our MIO colleague Thibaut Wagener, has made in situ observations of bacterial iron regeneration in the mesopelagic zone - the 'black' ocean where no light penetrates - of the Southern Ocean and the Mediterranean Sea. By combining these observations with numerical simulations of the PISCES biogeochemical model, the researchers highlighted the contrasting roles of biogenic iron and lithogenic iron in the mesopelagic zone. They demonstrated that the biogenic or lithogenic nature of the particulate iron exported to the deep sea controlled the replenishment of this deep reservoir with dissolved iron on a global scale.<\/p>

The mesopelagic zone (located between the base of the euphotic layer and 1000 m depth) represents a major reservoir of dissolved iron, a chemical element that plays a key role in controlling primary oceanic production on a global scale. As this area is difficult to explore, our knowledge of the mesopelagic iron cycle, a major component of its oceanic cycle, is limited to the systematic decoupling observed between the depth of iron remineralisation and that of other major elements such as carbon or nitrogen. A better understanding of iron regeneration in this zone of the deep ocean is therefore a major scientific challenge if we are to better describe the global distribution of dissolved iron and improve its representation in biogeochemical models.<\/p>

This lack of knowledge of mesopelagic iron regeneration is linked in particular to the difficulty of studying the biogeochemistry of the mesopelagic zone in situ. With the recent development of the RESPIRE and TM-RESPIRE traps\/incubators, it is now possible to measure simultaneously and in situ the rates of bacterial remineralisation of the flow of matter exported to the depths and the release of dissolved iron associated with the degradation of this matter.
Thanks to these innovative instruments, an international research team1 has been able to carry out these measurements for the first time in two contrasting areas of the ocean: the Southern Ocean and the Mediterranean Sea2. These two environments are characterised by very different surface productivity and atmospheric inputs of lithogenic matter (from rocks): in the Southern Ocean, the export of particulate iron is mainly carried by biogenic particles (from living organisms), whereas in the Mediterranean, the lithogenic component dominates.<\/p>

The study shows that the efficiency of iron regeneration is one to two orders of magnitude higher when iron fluxes are essentially biogenic than when lithogenic material is present. The replenishment of dissolved iron in the mesopelagic reservoir is therefore strongly conditioned by the composition of the particulate iron exported (i.e. biogenic or lithogenic). Although lithogenic particles of desert origin are considered to be a major source of dissolved iron for the surface ocean, it appears that several complex processes make these particles a trap for dissolved iron in the mesopelagic zone.<\/p>

These in situ measurements have enabled an initial parameterisation of mesopelagic iron regeneration, which has been integrated into the PISCES biogeochemical model. These new numerical simulations reveal that the combined effect of lithogenic particles and ocean dynamics is responsible for a major redistribution of dissolved iron in the first 1000 m of the water column, not only in regions close to deserts but also on the scale of the global ocean. In a context of climate change and aridification, these effects would be accentuated, with major repercussions on the efficiency of the biological carbon pump.<\/p>

Source<\/p>

Bressac M., C. Guieu, M.J. Ellwood, A. Tagliabue, T. Wagener, E.C. Laurenceau-Cornec, H. Whitby, G. Sarthou, P.W. Boyd. Resupply of mesopelagic dissolved iron controlled by particulate iron composition. Nature Geoscience, 2019, doi:10.1038\/s41561-019-0476-6.<\/p><\/div><\/div><\/div> <\/div> <\/div> <\/div> <\/div> <\/div><\/div>","protected":false},"excerpt":{"rendered":"

Pour la premi\u00e8re fois, une \u00e9quipe internationale dont fait partie notre coll\u00e9gue du MIO, Thibaut Wagener, a r\u00e9alis\u00e9 des observations in situ de la r\u00e9g\u00e9n\u00e9ration bact\u00e9rienne du fer dans la […]<\/p>\n","protected":false},"author":1,"featured_media":4489,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-6497","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-actualites"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.mio.osupytheas.fr\/en\/wp-json\/wp\/v2\/posts\/6497","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.mio.osupytheas.fr\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.mio.osupytheas.fr\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.mio.osupytheas.fr\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.mio.osupytheas.fr\/en\/wp-json\/wp\/v2\/comments?post=6497"}],"version-history":[{"count":0,"href":"https:\/\/www.mio.osupytheas.fr\/en\/wp-json\/wp\/v2\/posts\/6497\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.mio.osupytheas.fr\/en\/wp-json\/wp\/v2\/media\/4489"}],"wp:attachment":[{"href":"https:\/\/www.mio.osupytheas.fr\/en\/wp-json\/wp\/v2\/media?parent=6497"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.mio.osupytheas.fr\/en\/wp-json\/wp\/v2\/categories?post=6497"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.mio.osupytheas.fr\/en\/wp-json\/wp\/v2\/tags?post=6497"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}