Acoustic distribution of discriminated micronektonic organisms from a bi-frequency processing : the case study of eastern Kerguelen oceanic waters
Despite its ecological importance, micronekton remains one of the least investigated components of the open-ocean ecosystems. Our main goal was to characterize micronektonic organisms using bi-frequency acoustic data (38 and 120 kHz) by calibrating an algorithm tool that discriminates groups of scat...
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ftird:oai:ird.fr:fdi:010071047 2023-05-15T15:22:59+02:00 Acoustic distribution of discriminated micronektonic organisms from a bi-frequency processing : the case study of eastern Kerguelen oceanic waters Behagle, Nolwenn Cotte, C. Lebourges Dhaussy, Anne Roudaut, Gildas Duhamel, G. Brehmer, Patrice Josse, Erwan Cherel, Y. KERGUELEN OCEAN ARCTIQUE 2017 http://www.documentation.ird.fr/hor/fdi:010071047 EN eng http://www.documentation.ird.fr/hor/fdi:010071047 oai:ird.fr:fdi:010071047 Behagle Nolwenn, Cotte C., Lebourges Dhaussy Anne, Roudaut Gildas, Duhamel G., Brehmer Patrice, Josse Erwan, Cherel Y. Acoustic distribution of discriminated micronektonic organisms from a bi-frequency processing : the case study of eastern Kerguelen oceanic waters. Progress in Oceanography, 2017, 156, p. 276-289. Euphausiid Kerguelen Myctophid Southern Ocean Acoustics text 2017 ftird 2020-08-21T06:50:28Z Despite its ecological importance, micronekton remains one of the least investigated components of the open-ocean ecosystems. Our main goal was to characterize micronektonic organisms using bi-frequency acoustic data (38 and 120 kHz) by calibrating an algorithm tool that discriminates groups of scatterers in the top 300 m of the productive oceanic zone east of Kerguelen Islands (Indian sector of the Southern Ocean). The bi-frequency algorithm was calibrated from acoustic properties of mono-specific biological samples collected with trawls, thus allowing to discriminate three acoustic groups of micronekton: (i) "gas-bearing" (Delta Sv.120-38 < -1 dB), (ii) "fluid-like" (Delta S-v,S-120-38 > 2 dB), and (iii) "undetermined" scatterers (-1 < Delta S-v,S-120-38 < 2 dB). The three groups likely correspond biologically to gas-filled swimbladder fish (myctophids), crustaceans (euphausiids and hyperiid amphipods), and other marine organisms potentially present in these waters and containing either lipid-filled or no inclusion (e.g. other myctophids), respectively. The Nautical Area Scattering Coefficient (NASC) was used (echo-integration cells of 10 m long and 1 m deep) between 30 and 300 m depth as a proxy of relative biomass of acoustic targets. The distribution of NASC values showed a complex pattern according to: (i) the three acoustically defined groups, (ii) the type of structures (patch vs. layers) and (iii) the timing of the day (day/night cycle). NASC values were higher at night than during the day. A large proportion of scatterers occurred in layers while patches, that mainly encompass gas-bearing organisms, are especially observed during daytime. This method provided an essential descriptive baseline of the spatial distribution of micronekton and a relevant approach to (i) link micronektonic group to physical parameters to define their habitats, (ii) investigate trophic interactions by combining active acoustic and top predator satellite tracking, and (iii) study the functioning of the pelagic ecosystems at various spatio-temporal scales. Text Arctique* Kerguelen Islands Southern Ocean IRD (Institute de recherche pour le développement): Horizon Southern Ocean Kerguelen Kerguelen Islands Indian |
institution |
Open Polar |
collection |
IRD (Institute de recherche pour le développement): Horizon |
op_collection_id |
ftird |
language |
English |
topic |
Euphausiid Kerguelen Myctophid Southern Ocean Acoustics |
spellingShingle |
Euphausiid Kerguelen Myctophid Southern Ocean Acoustics Behagle, Nolwenn Cotte, C. Lebourges Dhaussy, Anne Roudaut, Gildas Duhamel, G. Brehmer, Patrice Josse, Erwan Cherel, Y. Acoustic distribution of discriminated micronektonic organisms from a bi-frequency processing : the case study of eastern Kerguelen oceanic waters |
topic_facet |
Euphausiid Kerguelen Myctophid Southern Ocean Acoustics |
description |
Despite its ecological importance, micronekton remains one of the least investigated components of the open-ocean ecosystems. Our main goal was to characterize micronektonic organisms using bi-frequency acoustic data (38 and 120 kHz) by calibrating an algorithm tool that discriminates groups of scatterers in the top 300 m of the productive oceanic zone east of Kerguelen Islands (Indian sector of the Southern Ocean). The bi-frequency algorithm was calibrated from acoustic properties of mono-specific biological samples collected with trawls, thus allowing to discriminate three acoustic groups of micronekton: (i) "gas-bearing" (Delta Sv.120-38 < -1 dB), (ii) "fluid-like" (Delta S-v,S-120-38 > 2 dB), and (iii) "undetermined" scatterers (-1 < Delta S-v,S-120-38 < 2 dB). The three groups likely correspond biologically to gas-filled swimbladder fish (myctophids), crustaceans (euphausiids and hyperiid amphipods), and other marine organisms potentially present in these waters and containing either lipid-filled or no inclusion (e.g. other myctophids), respectively. The Nautical Area Scattering Coefficient (NASC) was used (echo-integration cells of 10 m long and 1 m deep) between 30 and 300 m depth as a proxy of relative biomass of acoustic targets. The distribution of NASC values showed a complex pattern according to: (i) the three acoustically defined groups, (ii) the type of structures (patch vs. layers) and (iii) the timing of the day (day/night cycle). NASC values were higher at night than during the day. A large proportion of scatterers occurred in layers while patches, that mainly encompass gas-bearing organisms, are especially observed during daytime. This method provided an essential descriptive baseline of the spatial distribution of micronekton and a relevant approach to (i) link micronektonic group to physical parameters to define their habitats, (ii) investigate trophic interactions by combining active acoustic and top predator satellite tracking, and (iii) study the functioning of the pelagic ecosystems at various spatio-temporal scales. |
format |
Text |
author |
Behagle, Nolwenn Cotte, C. Lebourges Dhaussy, Anne Roudaut, Gildas Duhamel, G. Brehmer, Patrice Josse, Erwan Cherel, Y. |
author_facet |
Behagle, Nolwenn Cotte, C. Lebourges Dhaussy, Anne Roudaut, Gildas Duhamel, G. Brehmer, Patrice Josse, Erwan Cherel, Y. |
author_sort |
Behagle, Nolwenn |
title |
Acoustic distribution of discriminated micronektonic organisms from a bi-frequency processing : the case study of eastern Kerguelen oceanic waters |
title_short |
Acoustic distribution of discriminated micronektonic organisms from a bi-frequency processing : the case study of eastern Kerguelen oceanic waters |
title_full |
Acoustic distribution of discriminated micronektonic organisms from a bi-frequency processing : the case study of eastern Kerguelen oceanic waters |
title_fullStr |
Acoustic distribution of discriminated micronektonic organisms from a bi-frequency processing : the case study of eastern Kerguelen oceanic waters |
title_full_unstemmed |
Acoustic distribution of discriminated micronektonic organisms from a bi-frequency processing : the case study of eastern Kerguelen oceanic waters |
title_sort |
acoustic distribution of discriminated micronektonic organisms from a bi-frequency processing : the case study of eastern kerguelen oceanic waters |
publishDate |
2017 |
url |
http://www.documentation.ird.fr/hor/fdi:010071047 |
op_coverage |
KERGUELEN OCEAN ARCTIQUE |
geographic |
Southern Ocean Kerguelen Kerguelen Islands Indian |
geographic_facet |
Southern Ocean Kerguelen Kerguelen Islands Indian |
genre |
Arctique* Kerguelen Islands Southern Ocean |
genre_facet |
Arctique* Kerguelen Islands Southern Ocean |
op_relation |
http://www.documentation.ird.fr/hor/fdi:010071047 oai:ird.fr:fdi:010071047 Behagle Nolwenn, Cotte C., Lebourges Dhaussy Anne, Roudaut Gildas, Duhamel G., Brehmer Patrice, Josse Erwan, Cherel Y. Acoustic distribution of discriminated micronektonic organisms from a bi-frequency processing : the case study of eastern Kerguelen oceanic waters. Progress in Oceanography, 2017, 156, p. 276-289. |
_version_ |
1766353673873522688 |