@article{fdi:010067752,
  title = {{T}ransfer of diazotroph-derived nitrogen towards non-diazotrophic planktonic communities : a comparative study between {T}richodesmium erythraeum, {C}rocosphaera watsonii and {C}yanothece sp.},
  author = {{B}erthelot, {H}. and {B}onnet, {S}ophie and {G}rosso, {O}. and {C}ornet, {V}. and {B}arani, {A}.},
  editor = {},
  language = {{ENG}},
  abstract = {{B}iological dinitrogen ({N}-2) fixation is the major source of new nitrogen ({N}) for the open ocean, and thus promotes marine productivity, in particular in the vast {N}-depleted regions of the surface ocean. {Y}et, the fate of the diazotroph-derived {N} ({DDN}) in marine ecosystems is poorly understood, and its transfer to auto-and heterotrophic surrounding plankton communities is rarely measured due to technical limitations. {M}oreover, the different diazotrophs involved in {N}-2 fixation ({T}richodesmium spp. vs. {UCYN}) exhibit distinct patterns of {N}-2 fixation and inhabit different ecological niches, thus having potentially different fates in the marine food webs that remain to be explored. {H}ere we used nanometer scale secondary ion mass spectrometry (nano{SIMS}) coupled with {N}-15(2) isotopic labelling and flow cytometry cell sorting to examine the {DDN} transfer to specific groups of natural phytoplankton and bacteria during artificially induced diazotroph blooms in {N}ew {C}aledonia (southwestern {P}acific). {T}he fate of the {DDN} was compared according to the three diazotrophs: the filamentous and colony-forming {T}richodesmium erythraeum ({IMS}101), and the unicellular strains {C}rocosphaera watsonii {WH}8501 and {C}yanothece {ATCC}51142. {A}fter 48 h, 7-17% of the {N}-2 fixed during the experiment was transferred to the dissolved pool and 6-12% was transferred to non-diazotrophic plankton. {T}he transfer was twice as high in the {T}. erythraeum bloom than in the {C}. watsonii and {C}yanothece blooms, which shows that filamentous diazotrophs blooms are more efficient at promoting non-diazotrophic production in {N}-depleted areas. {T}he amount of {DDN} released in the dissolved pool did not appear to be a good indicator of the {DDN} transfer efficiency towards the non-diazotrophic plankton. {I}n contrast, the {N}-15-enrichment of the extracellular ammonium ({NH}4+) pool was a good indicator of the {DDN} transfer efficiency: it was significantly higher in the {T}. erythraeum than in unicellular diazotroph blooms, leading to a {DDN} transfer twice as efficient. {T}his suggests that {NH}4+ was the main pathway of the {DDN} transfer from diazotrophs to non-diazotrophs. {T}he three simulated diazotroph blooms led to significant increases in non-diazotrophic plankton biomass. {T}his increase in biomass was first associated with heterotrophic bacteria followed by phytoplankton, indicating that heterotrophs took the most advantage of the {DDN} in this oligotrophic ecosystem.},
  keywords = {{NOUVELLE} {CALEDONIE} ; {PACIFIQUE}},
  booktitle = {},
  journal = {{B}iogeosciences},
  volume = {13},
  numero = {13},
  pages = {4005--4021},
  ISSN = {1726-4170},
  year = {2016},
  URL = {https://www.documentation.ird.fr/hor/fdi:010067752},
}