A multiproxy approach to constrain the origin of the natural fertilisation on the Kerguelen plateau

• Published in: Geochimica et Cosmochimica Acta
• Main Authors: Jeandel, C, Bourquin, M, Bowie, AR, Bucciareilli, E, Chever, F, DeHairs, F, Jacquet, S, Lacan, F, Sarthou, G, Van Beek, P, Venchiarutti, C, Zhang, Y, Blain, S
• Format: Text
• Language: English
• Published: Pergamon-Elsevier Science Ltd 2007
• Subjects: Earth Sciences; Oceanography; Chemical Oceanography; Austral; Heard Island; Kerguelen
• Online Access: https://doi.org/10.1016/j.gca.2007.06.018; http://ecite.utas.edu.au/71377

The Kerguelen Ocean and Plateau compared Study (KEOPS) took place during the austral summer (19 Jan-13 Feb 2005, R/V Marion-Dufresne, 68-78E/ 49-52S sector). One of the KEOPS objectives was to determine the mechanisms responsible for the bloom occurring on the Kerguelen plateau and allocated to natural fertilisation due to island inputs. Coupled with physical measurements, a multi-proxy investigation was carried out in order to better c onstrain thesources of iron, but also the water mass and particle pathways. REE concentration and Nd isotopes suggest that weathering of Heard Island brings significant amounts of iron to plateau waters (Zhang et al., in rev.), in agreement with radium isotopes (van Beek et al., in rev.) and consistent with total dissolvable and particulate iron results. Th isotopes allow thequantification of particle settling velocities on and off the Kerguelen plateau and the identification of strong boundary scavenging along the south-east Kerguelen slope, likely due to the occurrence of nepheloid layers (Venchiarutti et al, subm.). Slow particle settling velocities are observed on the Kerguelenplateau, consistent with the high mineralization rates characterizing this area, deduced from the barite concentrations which were used as proxy for twilight zone mineralization of organic matter (Jacquet et al., in rev.).This talk highlights the main results deduced from each proxy, underlining both coherences and contradictions. A synthetic and simplified scheme of the potential sources and sinks of iron over the plateau is finally discussed.