The Biogeochemistry of Electroactive Humic Substances and Its Connection to Iron Chemistry in the North East Atlantic and the Western Mediterranean Sea

Type Article
Date 2018-08
Language English
Author(s) Dulaquais Gabriel1, Waeles Mathieu1, Gerringa Loes J. A.2, Middag RobORCID2, Rijkenberg Micha J. A.2, Riso Ricardo1
Affiliation(s) 1 : Univ Bretagne Occidentale, Inst Univ Europeen Mer, Lab Sci Environm Marin CNRS UMR 6539, Plouzane, France.
2 : Univ Utrecht, NIOZ Royal Netherlands Inst Sea Res, Dept Ocean Syst OCS, Texel, Netherlands.
Source Journal Of Geophysical Research-oceans (2169-9275) (Amer Geophysical Union), 2018-08 , Vol. 123 , N. 8 , P. 5481-5499
DOI 10.1029/2018JC014211
WOS© Times Cited 11
Keyword(s) humic substances, iron, Mediterranean Sea, biogeochemistry, GEOTRACES
Abstract

We present the zonal distribution of electroactive humic-like substances (eHS) along a section from Offshore Portugal in the North East Atlantic to the Sicily Channel in the Mediterranean Sea. The concentrations were normalized to Suwannee River Fulvic Acid and ranged from 11g/L to 81g/L. The vertical distributions were typical of those previously reported for dissolved organic carbon in the Mediterranean Sea. High eHS concentrations were measured in surface water and concentrations decreased with depth before increasing again toward benthic maxima measured at some stations. We estimate that eHS represented a relatively small fraction of the natural organic matter in the Mediterranean Sea (2-5%) but considering their important role in the complexation and the solubility of key trace elements (e.g., iron and copper), the eHS cycle could influence the entire biogeochemistry of these marine systems. We identified key processes controlling the concentration of eHS. While biologically mediated production was the major source of eHS, riverine and rain inputs as well as sediment release were also likely external sources. Low eHS concentrations at subsurface depths pointed to photodegradation as a possible sink of eHS, but degradation by heterotrophic bacteria seemed to be the main sink in the deep sea. Finally, we found a positive correlation between dissolved iron and eHS concentrations. Estimation of eHS contribution to iron binding ligand concentrations indicates the complexation of iron by eHS in the Mediterranean Sea. These observations suggest links between the cycles of eHS and iron in the Mediterranean Sea.

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How to cite 

Dulaquais Gabriel, Waeles Mathieu, Gerringa Loes J. A., Middag Rob, Rijkenberg Micha J. A., Riso Ricardo (2018). The Biogeochemistry of Electroactive Humic Substances and Its Connection to Iron Chemistry in the North East Atlantic and the Western Mediterranean Sea. Journal Of Geophysical Research-oceans, 123(8), 5481-5499. Publisher's official version : https://doi.org/10.1029/2018JC014211 , Open Access version : https://archimer.ifremer.fr/doc/00616/72781/