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Contribution of Electroactive Humic Substances to the Iron-Binding Ligands Released During Microbial Remineralization of Sinking Particles

Whitby, Hannah; Bressac , Matthieu; Sarthou, Geraldine; Ellwood, Michael; Guieu , Cecile; Boyd, Philip W

Description

Iron is a key micronutrient in seawater, but concentrations would be negligible without the presence of organic ligands. The processes influencing the ligand pool composition are poorly constrained, limiting our understanding of the controls on dissolved iron distributions. To address this, the release of iron and iron‐binding ligands during the microbial remineralization of sinking particles was investigated by deploying in situ particle interceptor/incubator devices at subsurface sites in the...[Show more]

dc.contributor.authorWhitby, Hannah
dc.contributor.authorBressac , Matthieu
dc.contributor.authorSarthou, Geraldine
dc.contributor.authorEllwood, Michael
dc.contributor.authorGuieu , Cecile
dc.contributor.authorBoyd, Philip W
dc.date.accessioned2021-01-11T03:38:07Z
dc.date.available2021-01-11T03:38:07Z
dc.identifier.issn0094-8276
dc.identifier.urihttp://hdl.handle.net/1885/219268
dc.description.abstractIron is a key micronutrient in seawater, but concentrations would be negligible without the presence of organic ligands. The processes influencing the ligand pool composition are poorly constrained, limiting our understanding of the controls on dissolved iron distributions. To address this, the release of iron and iron‐binding ligands during the microbial remineralization of sinking particles was investigated by deploying in situ particle interceptor/incubator devices at subsurface sites in the Mediterranean Sea and Subantarctic. Analyses revealed that the pool of released ligands was largely dominated by electroactive humic substances (74 ±28%). The release of ligands during remineralization ensured that concurrently released iron remained in solution, which is crucial for iron regeneration. This study presents compelling evidence of the key role of humic ligands in the subsurface replenishment of dissolved iron and thus on the wider oceanic dissolved iron inventory, which ultimately controls the magnitude of iron resupplied to the euphotic zone. PLAIN LANGUAGE SUMMARY: Microscopic plants and animals in seawater require nutrients to survive. One of these key nutrients is iron, dissolved in seawater at very low concentrations. The growth of around half of the microscopic life in the upper ocean is dependent on the availability of this dissolved iron. These organisms form the bottom of the food chain, and their growth is linked to marine productivity and the drawdown of carbon into the deep ocean, in turn influencing climate change. Because iron tends to not dissolve easily in seawater, it must bind with compounds known as ligands, which help keep iron dissolved. However, processes controlling the composition of this ligand pool are poorly understood. As material sinks through the water column, it is broken down by marine microbes, releasing iron and ligands. Here we have studied the release of iron, ligands, and a specific type of ligand known as humic substances, during the microbial degradation of sinking particles. By doing this, we have identified a large fraction of the released ligand pool. This furthers our understanding of the processes controlling dissolved iron concentrations and distributions in ocean waters, providing key information for biogeochemical modeling and for calculating carbon sequestration in seawater.
dc.description.sponsorshipM. B. was funded by the European Union Seventh Framework Programme (FP7/ 2007‐2013) under grant agreement no. (PIOF‐GA‐2012‐626734). This study is a contribution to the PEACETIME project (https://doi.org/10.17600/ 17000300), a joint initiative of the MERMEX and ChArMEx components supported by CNRS‐INSU, IFREMER, CEA, and Météo‐France as part of the programme MISTRALS coordinated by INSU. H. W. was supported by the “Laboratoire d'Excellence” LabexMER (ANR‐10‐LABX‐19) and by the EU FP7 Marie Curie actions (PCOFUND‐GA‐2013‐609102), through the PRESTIGE programme coordinated by Campus France. This research was financially supported under Australian Research Council's Discovery (DP170102108 and DP130100679) and Laureate Awards (FL160100131).
dc.format.mimetypeapplication/pdf
dc.language.isoen_AU
dc.publisherAmerican Geophysical Union
dc.rights©2020. The Authors
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/
dc.sourceGeophysical Research Letters
dc.titleContribution of Electroactive Humic Substances to the Iron-Binding Ligands Released During Microbial Remineralization of Sinking Particles
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume47
dc.date.issued2020
local.identifier.absfor040502 - Chemical Oceanography
local.identifier.ariespublicationa383154xPUB11130
local.publisher.urlhttps://www.wiley.com/en-gb
local.type.statusPublished Version
local.contributor.affiliationWhitby, Hannah, University of Liverpool
local.contributor.affiliationBressac , Matthieu, University of Tasmania
local.contributor.affiliationSarthou, Geraldine, CNRS
local.contributor.affiliationEllwood, Michael, College of Science, ANU
local.contributor.affiliationGuieu , Cecile, New York University in Abu Dhabi
local.contributor.affiliationBoyd, Philip W, University of Tasmania
dc.relationhttp://purl.org/au-research/grants/arc/DP170102108
dc.relationhttp://purl.org/au-research/grants/arc/DP130100679
dc.relationhttp://purl.org/au-research/grants/arc/FL160100131
local.bibliographicCitation.issue7
local.bibliographicCitation.startpage1
local.bibliographicCitation.lastpage11
local.identifier.doi10.1029/2019GL086685
local.identifier.absseo961104 - Physical and Chemical Conditions of Water in Marine Environments
dc.date.updated2020-11-02T04:16:57Z
dcterms.accessRightsOpen Access
dc.provenanceThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
dc.rights.licenseCreative Commons Attribution License
CollectionsANU Research Publications

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