Composition of diatom communities and their contribution to plankton biomass in the naturally iron fertilized region of Kerguelen in the Southern Ocean
|Author(s)||Lasbleiz Marine1, Leblanc Karine1, Armand Leanne K.2, Christaki Urania3, Georges Clement3, Obernosterer Ingrid4, Queguiner Bernard1|
|Affiliation(s)||1 : Aix Marseille Univ, Univ Toulon, CNRS, INSU,IRD,MIO,UM 110, F-13288 Marseille 09, France.
2 : Macquarie Univ, Dept Biol Sci, N Ryde, NSW 2109, Australia.
3 : ULCO, CNRS, UMR8187 LOG, INSU, 32 Ave Foch, F-62930 Wimereux, France.
4 : UPMC, Univ Paris 06, Lab Oceanog Microbienne LOMIC, CNRS,Observ Oceanol,Sorbonne Univ, F-66650 Banyuls Sur Mer, France.
|Source||Fems Microbiology Ecology (0168-6496) (Oxford Univ Press), 2016-11 , Vol. 92 , N. 11 , P. fix171 (1-6)|
|WOS© Times Cited||24|
|Keyword(s)||diatoms, carbon biomass, plankton community structure, natural iron fertilization, 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 with 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.|