@article{fdi:010083230,
  title = {{H}igh-sustained concentrations of organisms at very low oxygen concentration indicated by acoustic profiles in the oxygen deficit region off {P}eru},
  author = {{P}aulmier, {A}ur{\'e}lien and {E}ldin, {G}{\'e}rard and {O}choa, {J}. and {D}ewitte, {B}oris and {S}udre, {J}. and {G}arcon, {V}. and {G}relet, {J}. and {M}osquera-{V}asquez, {K}. and {V}ergara, {O}. and {M}aske, {H}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he oxygen deficient mesopelagic layer ({ODL}) off {P}eru has concentrations below 5 mu mol {O}-2 kg(-1) and is delimited by a shallow upper oxycline with strong vertical gradient and a more gradual lower oxycline (l{O}x). {S}ome regions show a narrow band of slightly increased oxygen concentrations within the {ODL}, an intermediate oxygen layer (i{O}(2)). {CTD}, oxygen and lowered {A}coustic {D}oppler {C}urrent {P}rofiler ({LADCP}, 300 k{H}z) profiles were taken on the shelf edge and outside down to mostly 2000 m. {W}e evaluate here the acoustic volume backscatter strength of the {LADCP} signal representing organisms of about 5 mm size. {D}ominant features of the backscatter profiles were a minimum backscatter strength within the {ODL}, and just below the l{O}x a marked backscatter increase reaching a maximum at less than 3.0 mu mol {O}-2 kg(-1). {B}elow this maximum, the acoustic backscatter strength gradually decreased down to 1000 m below the l{O}x. {T}he backscatter strength also increased at the i{O}(2) in parallel to the oxygen concentration perturbations marking the i{O}(2). {T}hese stable backscatter features were independent of the time of day and the organisms represented by the backscatter had to be adapted to live in this microaerobic environment. {D}uring daylight, these stable structures were overlapped by migrating backscatter peaks. {O}utstanding features of the stable backscatter were that at very low oxygen concentrations, the volume backscatter was linearly related to the oxygen concentration, reaching half peak maximum at less than 2.0 mu mol {O}-2 kg(-1) below the l{O}x, and the depth-integrated backscatter of the peak below the l{O}x was higher than the integral above the {O}x. {B}oth features suggest that sufficient organic material produced at the surface reaches to below the {ODL} to sustain the major fraction of the volume backscatter-producing organisms in the water column. {T}hese organisms are adapted to the microaerobic environment so they can position themselves close to the lower oxycline to take advantage of the organic particles sinking out of the {ODL}.</p>},
  keywords = {microaerobic zooplankton ; lowered {ADCP} ; oxygen minimum zone ({OMZ}) ; biomass below {OMZ} ; {E}astern {T}ropical {S}outh {P}acific ; {PEROU} ; {ZONE} {TROPICALE} ; {PACIFIQUE} {SUD}},
  booktitle = {},
  journal = {{F}rontiers in {M}arine {S}cience},
  volume = {8},
  numero = {},
  pages = {723056 [12 p.]},
  year = {2021},
  DOI = {10.3389/fmars.2021.723056},
  URL = {https://www.documentation.ird.fr/hor/fdi:010083230},
}