@article{fdi:010072470,
  title = {{D}istribution and drivers of symbiotic and free-living diazotrophic cyanobacteria in the western tropical {S}outh {P}acific},
  author = {{S}tenegren, {M}. and {C}aputo, {A}. and {B}erg, {C}. and {B}onnet, {S}ophie and {F}oster, {R}. {A}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he abundance and distribution of cyanobacterial diazotrophs were quantified in two regions ({M}elanesian archipelago, {MA}; and subtropical gyre, {SG}) of the western tropical {S}outh {P}acific using nif{H} quantitative polymerase chain reaction (q{PCR}) assays. {UCYN}-{A}1 and {A}2 host populations were quantified using 18{S} r{RNA} q{PCR} assays including one newly developed assay. {A}ll phylotypes were detected in the upper photic zone (0-50 m), with higher abundances in the {MA} region. {T}richodesmium and {UCYN}-{B} dominated and ranged from 2.18 x 10(2) to 9.41 x 10(6) and 1.10 x 10(2) to 2.78 x 10(6) nif{H} copies {L}-1, respectively. {H}et-1 (symbiont of {R}hizosolenia diatoms) was the next most abundant (1.40 x 10(1)-1.74 x 10(5) nif{H} copies {L}-1) and co-occurred with het-2 and het-3. {UCYN}-{A}1 and {A}2 were the least abundant diazotrophs and were below detection (bd) in 63 and 79, respectively, of 120 samples. {I}n addition, in up to 39% of samples in which {UCYN}-{A}1 and {A}2 were detected, their respective hosts were bd. {P}airwise comparisons of the nif{H} abundances and various environmental parameters supported two groups: a deep-dwelling group (45 m) comprised of {UCYN}-{A}1 and {A}2 and a surface group (0-15 m) comprised of {T}richodesmium, het-1 and het-2. {T}emperature and photosynthetically active radiation were positively correlated with the surface group, while {UCYN}-{A}1 and {A}2 were positively correlated with depth, salinity, and oxygen. {S}imilarly, in a meta-analysis of 11 external datasets, all diazotrophs, except {UCYN}-{A} were correlated with temperature. {C}ombined, our results indicate that conditions favoring the {UCYN}-{A} symbiosis differ from those of diatom diazotroph associations and free-living cyanobacterial diazotrophs.},
  keywords = {{PACIFIQUE} {SUD} ; {ZONE} {TROPICALE}},
  booktitle = {},
  journal = {{B}iogeosciences},
  volume = {15},
  numero = {5},
  pages = {1559--1578},
  ISSN = {1726-4170},
  year = {2018},
  DOI = {10.5194/bg-15-1559-2018},
  URL = {https://www.documentation.ird.fr/hor/fdi:010072470},
}