FN Archimer Export Format
PT J
TI Unveiling the Si cycle using isotopes in an iron fertilized zone of the Southern Ocean: from mixed layer supply to export
BT 
AF CLOSSET, Ivia
   CARDINAL, Damien
   REMBAUVILLE, Mathieu
   THIL, Francois
   BLAIN, Stephane
AS 1:1;2:1;3:2;4:3;5:2;
FF 1:;2:;3:;4:;5:;
C1 Univ Paris 06, Sorbonne Univ, UPMC, CNRS,IRD,MNHN,LOCEAN Lab, 4 Pl Jussieu, F-75005 Paris, France.
   Univ Paris 06, Sorbonne Univ, UPMC, CNRS,Lab Oceanog Microbienne LOMIC,Observ Oceanol, F-66650 Banyuls Sur Mer, France.
   CNRS, Lab Sci Climat & Environm, F-91190 Gif Sur Yvette, France.
C2 UNIV PARIS 06, FRANCE
   UNIV PARIS 06, FRANCE
   CNRS, FRANCE
IF 3.851
TC 9
UR https://archimer.ifremer.fr/doc/00344/45528/45085.pdf
   https://archimer.ifremer.fr/doc/00344/45528/45086.pdf
   https://archimer.ifremer.fr/doc/00344/45528/47268.pdf
   https://archimer.ifremer.fr/doc/00344/45528/47269.pdf
LA English
DT Article
CR MD 188 / KEOPS 2
BO Marion Dufresne
AB A massive diatom-bloom is observed annually in the surface waters of the naturally Fe-fertilized Kerguelen Plateau (Southern Ocean). In this study, silicon isotopic signatures (δ30Si) of silicic acid (DSi) and suspended biogenic silica (BSi) were investigated in the whole water column with an unprecedented spatial resolution in this region, during the KEOPS-2 experiment (spring 2011). We use δ30Si measurements to track the silicon sources that fuel the bloom, and investigate the seasonal evolution of Si biogeochemical cycle in the iron fertilized area. We compare the results from a HNLC reference station with stations characterized by different degrees of iron enrichment and bloom conditions. Dissolved and particulate δ30Si signatures were generally highly variable in the upper 500 m, reflecting the effect of the intense silicon utilization in spring, while they were quite homogeneous in deeper waters. The Si-isotopic and mass balance identified a unique WW Si-source for the iron-fertilized area originating from the southeastern Kerguelen Plateau and spreading northward. However, when reaching a retroflection of the Polar Front (PF), the δ30Si composition of WW silicic acid pool was getting progressively heavier. This would result from sequential diapycnal mixings between these initial WW and ML water masses, highlighting the strong circulation of surface waters that defined this zone. When comparing the results from the two KEOPS expeditions, the relationship between DSi depletion, BSi production and their isotopic composition appears decoupled in the iron fertilized area. This seasonal decoupling could help to explain the low apparent fractionation factor observed here in the ML at the end of summer. Taking into account these considerations, we refined the seasonal net BSi production in the ML of the iron-fertilized area to 3.0 ± 0.3 mol Si m−2 y−1, that was exclusively sustained by surface water phytoplankton populations. These insights confirm that the isotopic composition of dissolved and particulate silicon is a promising tool to improve our understanding on the Si-biogeochemical cycle since the isotopic and mass balance allows resolving the processes involved i.e. uptake, dissolution, mixing
PY 2016
PD NOV
SO Biogeosciences
SN 1726-4170
PU Copernicus Gesellschaft Mbh
VL 13
IS 21
UT 000387455900003
BP 6049
EP 6066
DI 10.5194/bg-13-6049-2016
ID 45528
ER

EF