Contrasted geographical distribution of N-2 fixation rates and nifH phylotypes in the Coral and Solomon Seas (southwestern Pacific) during austral winter conditions

2015

Article référencé dans le Web of Science WOS:000368907500002

Bonnet Sophie, Rodier Martine, Turk-Kubo K. A., Germineaud C., Menkès Christophe, Ganachaud Alexandre, Cravatte Sophie, Raimbault P., Campbell E., Queroue F., Sarthou G., Desnues Anne, Maes Christophe, Eldin Gérard

Global Biogeochemical Cycles, 2015, 29 (11), p. 1874-1892 ISSN 0886-6236

Biological dinitrogen (N-2) fixation and the distribution of diazotrophic phylotypes were investigated during two cruises in the Coral Sea and the Solomon Sea (southwestern Pacific) during austral winter conditions. N-2 fixation rates were measurable at every station, but integrated (0-150 m) rates were an order of magnitude higher in the Solomon Sea (30 to 5449 mu mol N m(-2) d(-1)) compared to those measured in the Coral Sea (2 to 10(9) mu mol N m(-2) d(-1)). Rates measured in the Solomon Sea were in the upper range (100-1000 mu mol N m(-2) d(-1)) or higher than rates compiled in the global MARine Ecosystem biomass DATa database, indicating that this region has some of the highest N-2 fixation rates reported in the global ocean. While unicellular diazotrophic cyanobacteria from group A (UCYN-A1 and UCYN-A2) and the proteobacteria gamma-24774A11 dominated in the Coral Sea and were correlated with N-2 fixation rates (p < 0.05), Trichodesmium and UCYN-B dominated in the Solomon Sea and were correlated (p < 0.05) with N-2 fixation rates. UCYN-A were totally absent in the Solomon Sea. The biogeographical distribution of diazotrophs is discussed within the context of patterns in measured environmental parameters.

Limnologie physique / Océanographie physique [032] ; Ecologie, systèmes aquatiques [036]

PACIFIQUE ; SALOMON MER ; CORAIL MER

Fonds IRD [F B010066151]

fdi:010066151