Differentiating Lithogenic Supplies, Water Mass Transport, and Biological Processes On and Off the Kerguelen Plateau Using Rare Earth Element Concentrations and Neodymium Isotopic Compositions
|Author(s)||Grenier Melanie1, 2, Garcia-Solsona Ester1, 3, 7, Lemaitre Nolwenn1, 4, 8, Trull Thomas W.2, 5, Bouvier Vincent1, 9, Nonnotte Philippe6, Van Beek Pieter1, Souhaut Marc1, Lacan Francois1, Jeandel Catherine1|
|Affiliation(s)||1 : Univ Toulouse, IRD, CNRS, CNES,LEGOS, Toulouse, France.
2 : Univ Tasmania, Antarctic Climate & Ecosyst CRC, Hobart, Tas, Australia.
3 : Univ Autonoma Barcelona, Inst Ciencia & Tecnol Ambientals, Bellaterra, Spain.
4 : Univ Bretagne Occidentale, Lab Sci Environm Marin LEMAR, Brest, France.
5 : CSIRO Oceans & Atmosphere, Hobart, Tas, Australia.
6 : Univ Bretagne Occidentale, CNRS, IRD, IUEM,Lab Geosci Ocean,UMR6539, Technopole Brest Iroise, Plouzane, France.
7 : Univ Barcelona, Fac Ciencies Terra, Dept Dinam Terra & Ocea, GRC Geociencies Marines, Barcelona, Spain.
8 : Swiss Fed Inst Technol, Inst Geochem & Petrol, Dept Earth Sci, Zurich, Switzerland.
9 : Univ Toulouse, CNRS, IRD, CNES,GET, Toulouse, France.
|Source||Frontiers In Marine Science (Frontiers Media Sa), 2018-11 , Vol. 5 , N. 426 , P. 28p.|
|WOS© Times Cited||11|
|Keyword(s)||Southern Ocean, Kerguelen Islands, rare earth elements, fractionation, anomalies, lithogenic, biologic, GEOTRACES|
Distributions of dissolved rare earth element (REE) concentrations and neodymium isotopic compositions (expressed as epsilon(Nd)) of seawater over and off the Kerguelen Plateau in the Southern Ocean are presented. The sampling took place during the austral spring bloom in October-November 2011 (KEOPS2 project, GEOTRACES process study) and aimed to further the investigations of the KEOPS1 austral summer study in terms of sources and transport of lithogenic material, and to investigate the impact of local biogeochemical cycles on the REE distributions. The REE signature of the coastal eastern Kerguelen Islands waters was characterized by negative europium anomalies (Eu/Eu*) and negative epsilon(Nd) in filtered samples. By contrast, the unfiltered sample showed a positive Eu/Eu* and more radiogenic epsilon(Nd). These distinct signatures could reflect either differential dissolution of the local flood basalt minerals or differential leaching of local trachyte veins. The dissolved Kerguelen coastal REE patterns differ from those observed close to Heard Island, these latter featuring a positive Eu/Eu* and a less radiogenic epsilon(Nd)(Zhang et al., 2008). These differences enabled us to trace the transport of waters (tagged by the Kerguelen REE signature) 200 km downstream from the coastal area, north of the Polar Front. Northward transport of the central Plateau shallow waters, enriched by both local vertical supplies and lateral advection of inputs from Heard Island, was also evident. However, the transport of Kerguelen inputs southeastward across the Polar Front could not be discerned (possibly as a result of rapid dilution or scavenging of REE signatures), although evidence for such transport was found previously using Ra isotopes (Sanial et al., 2015). Comparison of the REE patterns at stations sampled prior, during and at the demise of the bloom revealed diverse fractionations, including production of significant lanthanum and europium anomalies, which are tentatively ascribed to chemical reactions with various inorganic and biogenic phases, including surface coatings, barite crystals, and biogenic silica.