title: Composition of diatom communities and their contribution to plankton biomass in the naturally iron-fertilized region of Kerguelen in the Southern Ocean.
abstract: In the naturally iron-fertilized surface waters of the northern Kerguelen Plateau region, the early spring diatom community composition and contribution to plankton carbon biomass were investigated and compared with the high nutrient, low chlorophyll (HNLC) surrounding waters. The large iron-induced blooms were dominated by small diatom species belonging to the genera Chaetoceros (Hyalochaete) and Thalassiosira, which rapidly responded to the onset of favorable light-conditions in the meander of the Polar Front. In comparison, the iron-limited HNLC area was typically characterized by autotrophic nanoeukaryote-dominated communities and by larger and more heavily silicified diatom species (e.g. Fragilariopsis spp.). Our results support the hypothesis that diatoms are valuable vectors of carbon export to depth in naturally iron-fertilized systems of the Southern Ocean. Furthermore, our results corroborate observations of the exported diatom assemblage from a sediment trap deployed in the iron-fertilized area, whereby the dominant Chaetoceros (Hyalochaete) cells were less efficiently exported than the less abundant, yet heavily silicified, cells of Thalassionema nitzschioides and Fragilariopsis kerguelensis Our observations emphasize the strong influence of species-specific diatom cell properties combined with trophic interactions on matter export efficiency, and illustrate the tight link between the specific composition of phytoplankton communities and the biogeochemical properties characterizing the study area.
authors: Aix-Marseille Université, Université de Toulon, CNRS/INSU, IRD, MIO, UM 110, 13288, Marseille, Cedex 09, France Marine.lasbleiz@gmail.com.
authors: Marine
authors: M
authors: Lasbleiz
authors: Aix-Marseille Université, Université de Toulon, CNRS/INSU, IRD, MIO, UM 110, 13288, Marseille, Cedex 09, France.
authors: Karine
authors: K
authors: Leblanc
authors: Department of Biological Sciences, Macquarie University, North Ryde, New South Wales, 2109, Australia.
authors: Leanne K
authors: LK
authors: Armand
authors: INSU-CNRS, UMR8187 LOG, Laboratoire d'Océanologie et des Géosciences, Université du Littoral Côte d'Opale, ULCO, 32 avenue Foch, 62930 Wimereux, France.
authors: Urania
authors: U
authors: Christaki
authors: INSU-CNRS, UMR8187 LOG, Laboratoire d'Océanologie et des Géosciences, Université du Littoral Côte d'Opale, ULCO, 32 avenue Foch, 62930 Wimereux, France.
authors: Clément
authors: C
authors: Georges
authors: CNRS, Sorbonne Universités, UPMC Univ Paris 06, Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire Océanologique, F-66650 Banyuls/mer, France.
authors: Ingrid
authors: I
authors: Obernosterer
authors: Aix-Marseille Université, Université de Toulon, CNRS/INSU, IRD, MIO, UM 110, 13288, Marseille, Cedex 09, France.
authors: Bernard
authors: B
authors: Quéguiner
mesh_terms: D001105:Archaea / Q000302:isolation & purification / Q000378:metabolism*; D001419:Bacteria / Q000302:isolation & purification / Q000378:metabolism*; D044822:Biodiversity; D018533:Biomass; D002244:Carbon / Q000032:analysis / Q000378:metabolism; D002734:Chlorophyll; D017377:Diatoms / Q000145:classification* / Q000378:metabolism*; D019156:Indian Ocean; D007501:Iron / Q000378:metabolism; D009792:Oceans and Seas; D010839:Phytoplankton / Q000378:metabolism*; D012621:Seasons
chemical_list: D002734:Chlorophyll; D002244:Carbon; D007501:Iron
keywords: Southern Ocean; carbon biomass; diatoms; natural iron fertilization; plankton community structure