@article{fdi:010090306,
  title = {{T}he {B}ay of {B}engal : an enigmatic diazotrophic niche},
  author = {{S}axena, {H}. and {S}ahoo, {D}. and {N}azirahmed, {S}. and {C}haudhari, {D}. and {R}ahi, {P}. and {K}umar, {S}. and {B}enavides, {M}ar and {K}rishna, {A}. {V}. and {S}udheer, {A}. {K}. and {S}ingh, {A}.},
  editor = {},
  language = {{ENG}},
  abstract = {{B}iological dinitrogen ({N}-2) fixation is meagerly explored in the {B}ay of {B}engal ({B}ay). {S}tratified, warm, oligotrophic (but relatively high iron and phosphate) and oxygen minimum zone ({OMZ}) waters of the {B}ay might be a niche for diazotrophs. {T}herefore, we conducted {N}-2 fixation rate measurements during the spring inter-monsoon in the euphotic zone, the {OMZ} and below the {OMZ} down to 1,500 m depth near the coastal and in the central {B}ay. {W}e further assessed primary production and cyanobacterial community composition along with their potential environmental controlling parameters. {N}-2 fixation rates in the euphotic zone were low (0.02-0.38 nmol {N} {L}-1 d(-1)) and their contribution to primary production was small (<2%). {D}espite conducive conditions for diazotrophy in the {B}ay, the reason for the relatively low euphotic zone and {OMZ} {N}-2 fixation rates remained unclear and enigmatic. {I}nterestingly, significantly higher {N}-2 fixation rates occurred below the {OMZ} (>600 m depth), ranging from 0.06 to 0.11 nmol {N} {L}-1 d(-1) where oxygen concentrations ranged between 0.5 and 1.6 m{L} {L}-1, rather than within the {OMZ} where rates ranged from 0.02 to 0.08 nmol {N} {L}-1 d(-1) and oxygen concentrations were <= 0.5 m{L} {L}-1. {E}uphotic zone {N}-2 fixation showed seasonality in the {B}ay with increasing rates from spring to summer season, perhaps owing to increasing {F}e flux as the summer monsoon approaches its peak. {P}lain {L}anguage {S}ummary {T}he growth of marine phytoplankton is primarily limited by the reactive forms of nitrogen. {D}initrogen-fixing organisms (termed "diazotrophs") supplement this need by providing a natural fertilizer-ammonium. {D}iazotrophs prefer phosphate and iron-rich, but reactive nitrogen-deficit waters. {T}herefore, the oligotrophic {B}ay of {B}engal (the northeastern {I}ndian {O}cean) with excess phosphate relative to reactive nitrogen and high iron input could be a potential niche for diazotrophy. {H}owever, our results indicate that {N}-2 fixation rates were low and supported less than 2% of organic matter formation in the {B}ay of {B}engal during the spring inter-monsoon. {S}urprisingly, {N}-2 fixation rates were higher below the oxygen minimum zone than within it. {T}hus, our study provides additional evidence that {N}-2 fixation is feasible (low but persistent) in dark marine places with abundant oxygen in conjunction with surface ocean.},
  keywords = {{N}-2 fixation ; nutrients ; monsoon ; cyanobacteria ; oxygen minimum zone ; {I}ndian {O}cean ; {GOLFE} {DU} {BENGALE} ; {OCEAN} {INDIEN}},
  booktitle = {},
  journal = {{J}ournal of {G}eophysical {R}esearch : {B}iogeosciences},
  volume = {128},
  numero = {9},
  pages = {e2023{JG}007687 [16 p.]},
  ISSN = {2169-8953},
  year = {2023},
  DOI = {10.1029/2023jg007687},
  URL = {https://www.documentation.ird.fr/hor/fdi:010090306},
}