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Resupply of mesopelagic dissolved iron controlled by particulate iron composition
journal contribution
posted on 2023-05-20, 10:44 authored by Bressac, M, Guieu, C, Ellwood, MJ, Tagliabue, A, Wagener, T, Emmanuel LaurenceauEmmanuel Laurenceau, Whitby, H, Sarthou, G, Philip BoydPhilip BoydThe dissolved iron supply controls half of the oceans’ primary productivity. Resupply by the remineralization of sinking particles, and subsequent vertical mixing, largely sustains this productivity. However, our understanding of the drivers of dissolved iron resupply, and their influence on its vertical distribution across the oceans, is still limited due to sparse observations. There is a lack of empirical evidence as to what controls the subsurface iron remineralization due to difficulties in studying mesopelagic biogeochemistry. Here we present estimates of particulate transformations to dissolved iron, concurrent oxygen consumption and iron-binding ligand replenishment based on in situ mesopelagic experiments. Dissolved iron regeneration efficiencies (that is, replenishment over oxygen consumption) were 10- to 100-fold higher in low-dust subantarctic waters relative to higher-dust Mediterranean sites. Regeneration efficiencies are heavily influenced by particle composition. Their make-up dictates ligand release, controls scavenging, modulates ballasting and may lead to the differential remineralization of biogenic versus lithogenic iron. At high-dust sites, these processes together increase the iron remineralization length scale. Modelling reveals that in oceanic regions near deserts, enhanced lithogenic fluxes deepen the ferricline, which alter the vertical patterns of dissolved iron replenishment, and set its redistribution at the global scale. Such wide-ranging regeneration efficiencies drive different vertical patterns in dissolved iron replenishment across oceanic provinces.
History
Publication title
Nature GeoscienceVolume
12Pagination
995-1000ISSN
1752-0894Department/School
Institute for Marine and Antarctic StudiesPublisher
Nature Publishing GroupPlace of publication
United KingdomRights statement
© The Author(s), under exclusive licence to Springer Nature Limited 2019Repository Status
- Restricted