FN Archimer Export Format
PT J
TI Programmed cell death in diazotrophs and the fate of organic matter in the western tropical South Pacific Ocean during the OUTPACE cruise
BT 
AF Spungin, Dina
   Belkin, Natalia
   Foster, Rachel
   Stenegren, Marcus
   Caputo, Andrea
   Pujo-Pay, Mireille
   Leblond, Nathalie
   Dupouy, Cecile
   Bonnet, Sophie
   Berman-Frank, Ilana
AS 1:1;2:1;3:2;4:2;5:2;6:3;7:4;8:4;9:5;10:1;
FF 1:;2:;3:;4:;5:;6:;7:;8:;9:;10:;
C1 The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
   Stockholm University, Department of Ecology, Environment and Plant Sciences. Stockholm, Sweden
   Laboratoire d’Océanographie Microbienne - UMR 7321, CNRS - Sorbonne Universités, UPMC Univ Paris 06, Observatoire Océanologique, 66650 Banyuls-sur-mer, France
   Observatoire Océanologique de Villefranche, Laboratoire d’Océanographie de Villefranche, UMR 7093, Villefranche-sur Mer, France
   Aix-Marseille Univ., Univ. Toulon, CNRS/INSU, IRD, UM 110, Mediterranean Institute of Oceanography (MIO) UM 110, 13288, Noumea, New Caledonia
C2 UNIV BAR ILAN, ISRAEL
   UNIV STOCKHOLM, SWEDEN
   UNIV PARIS 06, FRANCE
   OBSERV OCEANOL VILLEFRANCHE, FRANCE
   IRD, FRANCE
IN DOAJ
IF 3.951
TC 0
UR https://archimer.ifremer.fr/doc/00419/53048/53985.pdf
   https://archimer.ifremer.fr/doc/00419/53048/53993.flv
   https://archimer.ifremer.fr/doc/00419/53048/53994.flv
   https://archimer.ifremer.fr/doc/00419/53048/53995.flv
   https://archimer.ifremer.fr/doc/00419/53048/59627.pdf
   https://archimer.ifremer.fr/doc/00419/53048/59628.pdf
LA English
DT Article
CR OUTPACE
BO L'Atalante
AB The fate of diazotroph (N2 fixers) derived carbon (C) and nitrogen (N) and their contribution to vertical export of C and N in the Western Tropical South Pacific Ocean was studied in OUTPACE (Oligotrophy to UlTra-oligotrophy PACific Experiment). Our specific objective during OUTPACE was to determine whether autocatalytic programmed cell death (PCD) is an important mechanism affecting diazotroph mortality and a factor regulating the vertical flux of organic matter and thus the fate of the blooms. We sampled at three long duration (LD) stations of 5 days each (LDA, LDB, and LDC) where drifting sediment traps were deployed at 150, 325 and 500 m depths. LDA and LDB were characterized by high chlorophyll a (Chl a) concentrations (0.2–0.6 µg L−1) and dominated by dense biomass of Trichodesmium as well as UCYN-B and diatom-diazotroph associations (Rhizosolenia with Richelia-detected by microscopy and het-1 nifH copies). Station LDC was located at an ultra-oligotrophic area of the South Pacific gyre with extremely low Chl a concentration (~ 0.02 µg L−1) with limited biomass of diazotrophs predominantly the unicellular UCYN-B. Our measurements of biomass from LDA and LDB yielded high activities of caspase-like and metacaspase proteases that are indicative of PCD in Trichodesmium and other phytoplankton. Metacaspase activity, reported here for the first time from oceanic populations, was highest at the surface of both LDA and LDB, where we also obtained high concentrations of transparent exopolymeric particles (TEP). TEP was negatively correlated with dissolved inorganic phosphorus and positively coupled to both the DOC and POC pools reflecting the typically high production of TEP under nutrient stress and its role as a source of sticky carbon facilitating aggregation and rapid vertical sinking. Evidence for bloom decline was observed at both LDA and LDB. However, the physiological status and rates of decline of the blooms differed between the stations, influencing the amount of accumulated diazotrophic organic matter and mass flux observed in the traps during our experimental time frame. At LDA sediment traps contained the greatest export of particulate matter and significant numbers of both intact and decaying Trichodesmium, UCYN-B, and het-1 compared to LDB where the bloom decline began only 2 days prior to leaving the station and to LDC where no evidence for bloom decline was seen. Substantiating previous findings from laboratory cultures linking PCD to carbon export in Trichodesmium, our results from OUTPACE indicate that induction of PCD by nutrient limitation in high biomass blooms such as Trichodesmium or diatom-diazotroph associations combined with high TEP production facilitates cellular aggregation and bloom termination, and expedites vertical flux to depth 
PY 2018
PD JAN
SO Biogeosciences
SN 1726-4170
PU Copernicus GmbH
VL 15
IS 12
BP 3893
EP 3908
DI 10.5194/bg-2018-3
ID 53048
ER

EF