@article{fdi:010089609,
  title = {{D}ecomposing acoustic signal reveals the pelagic response to a frontal system},
  author = {{I}zard, {L}. and {F}onvieille, {N}. and {M}erland, {C}. and {K}oubbi, {P}. and {N}erini, {D}. and {H}abasque, {J}{\'e}r{\'e}mie and {L}ebourges {D}haussy, {A}nne and {L}o {M}onaco, {C}. and {R}oudaut, {G}ildas and d'{O}vidio, {F}. and {C}harrassin, {J}. {B}. and {C}ott{\'e}, {C}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he pelagic zone is home to a large diversity of organisms such as macrozooplankton and micronekton ({MM}), connecting the surface productive waters to the mesopelagic layers (200-1000 m) through diel vertical migrations ({DVM}). {A}ctive acoustics complement net sampling observations by detecting sound-scattering layers ({SL}) of organisms, allowing to monitor the {MM} dynamics with a high spatio-temporal resolution. {M}ultifrequency analyses are a pertinent approach to better integrate the rich diversity of organisms composing {SL}s and their respective dynamics. {H}owever, analysing simultaneously emitted acoustic signals with distinct depth ranges and separating spatial from temporal variability is challenging and needs adapted tools to be fully exploited. {T}his study examines the pelagic realm in a transition zone between the {S}outhern {O}cean and the subtropical {I}ndian {O}cean, crossing the {S}aint-{P}aul and {A}msterdam islands' natural reserve. {W}e extended a {M}ultivariate {F}unctional {P}rincipal {C}omponent {A}nalysis (mf{PCA}) to analyse the joint vertical variation of five frequencies from two oceanographic cruises (2016 and 2022), allowing the decomposition of the acoustic dataset into orthogonal vertical modes ({VM}) of variability. {W}e found the first {VM} to be linked to the temporal variability due to {DVM}, while the following majorly depict patterns in spatial distribution. {O}verall, from the subantarctic to the subtropical zones, we observed (i) enrichment of densities in the surface layer (0-100 m), (ii) a decrease in densities in the intermediate layer during the daytime (100-300 m) and (iii) the apparition of an intensive deep scattering layer on the 38 k{H}z. {W}e explored {VM}s' connection with in -situ environmental conditions by clustering our observations into three distinct environmental-acoustic regions. {T}hese regions were compared with vertically integrated nautical area scattering coefficient distribution, a proxy for marine organisms' biomass. {A}dditionally, we analysed species assemblage changes from complementary cruises to further elucidate the observed acoustic distribution. {W}e show that the mf{PCA} method is promising to better integrate the pelagic horizontal, vertical and temporal dimensions which is a step towards further investigating the control of the environment on the distribution and structuring of pelagic communities.},
  keywords = {{M}ulti-frequency hydroacoustics ; {M}ultivariate functional data analysis ; {S}aint-{P}aul and {A}msterdam french islands ; {S}outhern {I}ndian {O}cean ; {OCEAN} {INDIEN}},
  booktitle = {},
  journal = {{J}ournal of {M}arine {S}ystems},
  volume = {243},
  numero = {},
  pages = {103951 [19 p.]},
  ISSN = {0924-7963},
  year = {2024},
  DOI = {10.1016/j.jmarsys.2023.103951},
  URL = {https://www.documentation.ird.fr/hor/fdi:010089609},
}