@article{fdi:010066054,
  title = {{D}iazotroph community succession during the {VAHINE} mesocosm experiment ({N}ew {C}aledonia lagoon)},
  author = {{T}urk-{K}ubo, {K}. {A}. and {F}rank, {I}. {E}. and {H}ogan, {M}. {E}. and {D}esnues, {A}nne and {B}onnet, {S}ophie and {Z}ehr, {J}. {P}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he {VAHINE} mesocosm experiment, conducted in the low-nutrient low-chlorophyll waters of the {N}oumea lagoon (coastal {N}ew {C}aledonia) was designed to trace the incorporation of nitrogen ({N}) fixed by diazotrophs into the food web, using large volume (50 m(3)) mesocosms. {T}his experiment provided a unique opportunity to study the succession of different {N}-2-fixing microorganisms (diazotrophs) and calculate in situ net growth and mortality rates in response to fertilization with dissolved inorganic phosphate ({DIP}) over a 23-day period, using quantitative polymerase chain reaction (q{PCR}) assays targeting widely distributed marine diazotroph lineages. {I}nside the mesocosms, the most abundant diazotroph was the heterocyst-forming {R}ichelia associated with {R}hizosolenia ({H}et-1) in the first half of the experiment, while unicellular cyanobacterial {G}roup {C} ({UCYN}-{C}) became abundant during the second half of the experiment. {D}ecreasing {DIP} concentrations following the fertilization event and increasing temperatures were significantly correlated with increasing abundances of {UCYN}-{C}. {M}aximum net growth rates for {UCYN}-{C} were calculated to range between 1.23 +/- 0.07 and 2.16 +/- 0.07 d(-1) in the mesocosms, which are among the highest growth rates reported for diazotrophs. {O}utside the mesocosms in the {N}ew {C}aledonia lagoon, {UCYN}-{C} abundances remained low, despite increasing temperatures, suggesting that the microbial community response to the {DIP} fertilization created conditions favorable for {UCYN}-{C} growth inside the mesocosms. {D}iazotroph community composition analysis using {PCR} targeting a component of the nitrogenase gene (nif{H}) verified that diazotrophs targeted in q{PCR} assays were collectively among the major lineages in the lagoon and mesocosm samples, with the exception of {C}rocosphaera-like phylotypes, where sequence types not typically seen in the oligotrophic ocean grew in the mesocosms. {M}aximum net growth and mortality rates for nine diazotroph phylotypes throughout the 23-day experiment were variable between mesocosms, and repeated fluctuations between periods of net growth and mortality were commonly observed. {T}he field population of diazotrophs in the {N}ew {C}aledonian lagoon waters appeared to be dominated by {H}et-1 over the course of the study period. {H}owever, results from both q{PCR} and {PCR} analysis indicated a diverse field population of diazotrophs was present in the lagoon at the time of sampling. {T}wo ecotypes of the {B}raarudosphaera bigelowii symbiont unicellular group {A} ({UCYN}-{A}) were present simultaneously in the lagoon, with the recently described {B}. bigelowii/{UCYN}-{A}2 association present at higher abundances than the {B}. bigelowii/{UCYN}-{A}1 association.},
  keywords = {{NOUVELLE} {CALEDONIE} ; {NOUMEA} {LAGON}},
  booktitle = {},
  journal = {{B}iogeosciences},
  volume = {12},
  numero = {24},
  pages = {7435--7452},
  ISSN = {1726-4170},
  year = {2015},
  URL = {https://www.documentation.ird.fr/hor/fdi:010066054},
}