@article{fdi:010047492, title = {{H}igh abundance of diazotrophic picocyanobacteria (< 3 mu m) in a {S}outhwest {P}acific coral lagoon}, author = {{B}iegala, {I}sabelle and {R}aimbault, {P}.}, editor = {}, language = {{ENG}}, abstract = {{I}n the present study we detected unicellular diazotrophic cyanobacteria along a nutrient gradient in {N}ew {C}aledonia's coral lagoon (24 000 km(2)) using whole-cell hybridization of specific {N}itro821 probes ({TSA}-{FISH}, {T}yramide {S}ignal {A}mplification of {F}luorescent {I}n {S}itu {H}ybridization). {T}he specificity of this probe was confirmed on cultures and in the natural environment, {S}urprisingly, the community of {N}itro821-targeted cells was numerically dominated by picocyanobacteria (97%, 1 to 1.5 mu m). {T}hese organisms were either free living (63%), recovered with the 0.2 to 3 mu m size fraction or associated (37%) to particles or planktonic dinoflagellates from larger size fractions (3 to 10 mu m and >10 mu m). {D}iazotrophic picocyanobacterial abundance ranged from 3 to 140 cells ml(-1) along the nutrient gradient and was highest at the oligotrophic lagoonal station. {T}hese cells may contribute to {N}-2 fixation from the < 10 mu m size fraction (4.4 to 8 nmol {N}-1 24 h(-1)), which was 4 times higher than the >10 mu m size fraction (0 to 1.9 nmol {N}-1 24 h(-1)). {I}n addition, in the middle of the lagoon daylight {N}-15(2) fixation could explain 78% of {N}-15(2) fixation over 24 h. {T}he results presented in the present study reveal for the first time a significant concentration of photosynthetic diazotrophs within the marine picoplankton community.}, keywords = {diazotrophs ; cyanobacteria ; picoplankton ; {FISH} ; {P}acific ; coral lagoon ; symbiosis}, booktitle = {}, journal = {{A}quatic {M}icrobial {E}cology}, volume = {51}, numero = {1}, pages = {45--53}, ISSN = {0948-3055}, year = {2008}, DOI = {10.3354/ame01185}, URL = {https://www.documentation.ird.fr/hor/fdi:010047492}, }