High variability in dissolved iron concentrations in the vicinity of the Kerguelen Islands (Southern Ocean)

Fabien Quéroué (1, 2, 3) , Géraldine Sarthou (1) , Hélène Planquette (1) , Eva Bucciarelli (1) , Fanny Chever (1) , Pier van Der Merwe (3) , Delphine Lannuzel (2, 3) , A. T. Townsend (4) , Marie Cheize (1) , Stéphane Blain (5) , Francesco d'Ovidio (6) , Andrew R. Bowie (2, 3)

1 LEMAR - Laboratoire des Sciences de l'Environnement Marin (LEMAR)
2 IMAS - Institute for Marine and Antarctic Studies [Hobart]
3 ACE-CRC - Antarctic Climate and Ecosystems Cooperative Research Centre
4 UTAS - University of Tasmania [Hobart, Australia]
5 LOBB - Laboratoire d'océanographie biologique de Banyuls
6 PEPS - Processus de couplage à Petite Echelle, Ecosystèmes et Prédateurs Supérieurs

Dissolved Fe (dFe) concentrations were measured in the upper 1300 m of the water column in the vicinity of the Kerguelen Islands as part of the second KErguelen Ocean Plateau compared Study (KEOPS2). Concentrations ranged from 0.06 nmol L⁻¹ in offshore, Southern Ocean waters to 3.82 nmol L⁻¹ within Hillsborough Bay, on the north-eastern coast of the Kerguelen Islands. Direct island runoff, glacial melting and resuspended sediments were identified as important inputs of dFe that could potentially fertilise the northern part of the plateau. A significant deep dFe enrichment was observed over the plateau with dFe concentrations increasing up to 1.30 nmol L⁻¹ close to the seafloor, probably due to sediment resuspension and pore water release. Biological uptake was shown to induce a significant decrease in dFe concentrations between two visits (28 days apart) at a station above the plateau. Our work also considered other processes and sources, such as lateral advection of enriched seawater, remineralisation processes, and the influence of the polar front (PF) as a vector for Fe transport. Overall, heterogeneous sources of Fe over and off the Kerguelen Plateau, in addition to strong variability in Fe supply by vertical or horizontal transport, may explain the high variability in dFe concentrations observed during this study.

Mots clés: SEDIMENT; DRAKE PASSAGE; DISTRIBUTIONS; CARBON; PLATEAU; FE; SEA; FERTILIZATION EXPERIMENT; ARCHIPELAGO; EVOLUTION; ACL

Domaines: Sciences de l'environnement; Géophysique [physics.geo-ph]; Biodiversité et Ecologie; Océan, Atmosphère

Fabien Quéroué, Géraldine Sarthou, Hélène Planquette, Eva Bucciarelli, Fanny Chever, et al.. High variability in dissolved iron concentrations in the vicinity of the Kerguelen Islands (Southern Ocean). Biogeosciences, 2015, 12 (12), pp.3869-3883. ⟨10.5194/bg-12-3869-2015⟩. ⟨hal-01207687⟩