PhD student in Acoustics applied to the study of marine organisms M/F
- Locmaria-Plouzané, Finistère
- CDD
- Temps-plein
SCIENTIFIC BACKGROUND
Micronekton organisms play an essential role in the mesopelagic zones of the world ocean. Prey to marine top predators (tuna), they are major players in the nutrient cycle and carbon sequestration[1]. Every day, they make diel vertical migrations over hundreds of meters. This highly dynamic movement during twilight phases is observed in all oceans, but patterns vary considerably in space and time. These vertical movements and the associated metabolic activity (surface feeding at night and deep metabolism during the day) have important consequences for the biological carbon pump[2][3].
Active acoustics (single- or multi-frequency hull sounders) can be used to study migratory dynamics by characterizing the distribution of scattering layers at very high resolution, but a number of obstacles remain (distinction of species and even taxa). Traditional invasive methods based on trawling are selective and underestimate biomass[4]. In ultrasonic detection of organisms in the water column, the frequency component of the signal is decisive in determining the type and size of targets detected[5]. In recent years, technological advances have made it possible to deploy autonomous broadband acoustic profilers (Wide Band Autonomous Transceiver, WBAT and WBTTUBE connected to the boat) as close as possible to the scattering layers, thereby increasing the spatial resolution of the measurement and enabling the acquisition of the frequency signatures of individual targets, thus complementing the information from hull sounders[6].
The data for this project were acquired as part of the APERO campaign and ANR, using 2 complementary devices of this type, one placed in deep scattering layers and the other in the layers as they migrate. Both migrating and non-migrating organisms will be studied through acoustic analysis of frequency responses and trawl sampling. But the innovative nature of the project lies in the exploration and analysis of acoustic data.
OBJECTIVES
(1) Quantify the vertical dynamics of micronekton diel migrations
Combined with data from the hull sounder, which provides a global image of migrations in the water column, broadband data from profilers on individual targets will enable us to better characterize migrations, the chronology of twilight transition phases for the migrating fraction, the speeds of organisms by tracking targets, the depths reached, and the density in fine-scale layers. The results obtained will feed into and calibrate a migration model developed as part of a thesis already funded (H. Thibault, MIO).
(2) Sonifying broadband acoustic recordings
The complexity and quantity of data make the analysis of broadband acoustic recordings tedious and delicate. Sonification of these data would make it possible to take advantage of the auditory system's excellent temporal and frequency acuity [9], and its ability to detect and separate multiple sources, even in complex and/or highly noisy environments[10]. The thesis will test and evaluate the relevance of this new sound analysis method, as well as its ability to inspire new ways of using conventional analysis tools (statistics, signal processing, artificial intelligence...).
(3) Classifying and sonifying individual targets recorded by broadband acoustic profilers
Thanks to their low sampling volume, broadband devices positioned as close as possible to the layers provide new spatial resolution in the deeper layers, enabling the detection of individuals on which continuous frequency information is much richer than with multi-frequency data. Although deployed for some years now, the analysis of data from these profilers is far from routine, and methodological exploration to arrive at a classification of organisms is in full development in the international community[6][11]. The thesis will contribute to this research by exploiting individual signatures to characterize the biodiversity present in the layers through the recognition of taxa (swim bladder fish, gelatinous fish, crustaceans, mollusks) and to study their respective dynamics.
METHODOLOGIES
During the APERO campaign in 2023 (N/O Thalassa), 30 acquisitions were made with the WBAT and WBTTUBE profilers at fixed 40-hour stations in deep water during the day and night, and during migration in the morning and evening. Analysis of these data will focus on (i) organism densities and (ii) the frequency signature of individual targets[12][13]. Data pre-processing will be guaranteed using tools developed in 2024. This thesis will go further and interpret biodiversity and migratory behavior in relation to trawling. This is where the musical and artistic aspects of the thesis come into their own. Broadband data will be explored in the audible domain via sonification, using the latest 3D sound technologies (Ambisonic, WFS, binaural) to accurately place a maximum of data all around the listener. Different ways of "sonifying" the data will be tested in collaboration with professional composers. These sonifications will be presented to the scientific community at conferences, but also to the artistic community and the general public at various events, concerts and art installations. In addition to the educational and mediation dimensions, these sonification presentations will provide concrete feedback on both aesthetic and scientific criteria (intelligibility, listening comfort, ability of sonification to draw attention to important signal characteristics...)[14]. The sound analysis tool developed during the thesis could then be made available to the community in the form of open-source software, for use by scientists and composers alike. This sonification also opens the door to the use of audio signal analysis tools unknown to the scientific community of acoustical halieutes.Scientific, material and financial conditions of the research project
- This thesis project is part of ANR APERO, which brings together UMRs LEMAR, MIO, LOV, LOCEAN, LOG, LOPS, Univ. Nantes, Stations de Roscoff et de Banyuls, and includes collaborations in Europe, the United States and Australia. Most of the data from the APERO campaign will be processed and available at the start of the thesis, and the M/F student will benefit from the preliminary work mentioned above.Objective of promoting the research work of the M/F doctoral student
A-level publications, oral presentations and sonification results at conferences, arts & sciences events and events for the general public (Arts'Pulseurs festival at Océanopolis and RESSAC at UBO, Le Mans sonore).References[1] Saba 2021 Limnol. Oceanogr. ; [2] Cotté 2022 J. Mar. Syst. ; [3] Ariza 2015 Prog. Oceanogr.
[4] Barbin 2024 Deep Sea Research I ; [5] Lavery 2007 J. Acoust. Soc. Am. ; [6] Cotter 2021 J. Acoust. Soc. Am. ; [7] Hegg 2018 Heliyon ; [8] Hendrickx 2022 Sonification d'Échogrammes : un projet Sciences & Arts. Congrès Français d'Acoustique ; [9] Moore 1995 “Hearing” Academic Press San Diego CA ; [10] McDermott 2009 Curr. Biol. ; [11] Dunn 2023 ICES J. of Mar. Sci.
[12] Bassett 2020 J. Acoust. Soc. Am. ; [13] Agersted 2021 ICES J Mar. Sci. ; [14] Hendrickx 2023 Sonification of underwater acoustic data: an art-science initiative. Forum Acusticum.RequirementsResearch Field Environmental science Education Level PhD or equivalentResearch Field Environmental science Education Level PhD or equivalentResearch Field Environmental science Education Level PhD or equivalentLanguages FRENCH Level BasicResearch Field Environmental science Years of Research Experience NoneResearch Field Environmental science » Earth science Years of Research Experience NoneResearch Field Environmental science » Global change Years of Research Experience NoneAdditional InformationAdditional commentsThe M/F candidate must hold an engineering degree and/or a Master 2 in signal processing, underwater acoustics. Ability to work with Python, Matlab, R is required.
M/F candidates should also have a particular interest in music. Skills in solfège, musical analysis, or even musical composition (MAO and/or acoustic music), and knowledge of mixing tools and audio software such as ProTools, Reaper, Logic or Max/MSP will be greatly appreciated.
An open mind towards interdisciplinarity and exploring new avenues is essential, as is a taste for mediation and interaction with diverse audiences.
We are looking for someone with good oral and written communication skills (French and English required) to present at conferences and write articles for scientific journals, the ability to work as part of a team, to be autonomous while remaining accountable, and in particular to share information with all supervisors.
Documents to be provided: Applications should include a detailed CV; at least two references (people likely to be contacted); a one-page cover letter; a one-page summary of the Master's thesis; grades from Master 1 or 2 or engineering school). Website for additional job detailsWork Location(s)Number of offers available 1 Company/Institute Institut Méditerranéen d'Océanologie Country France City LOCMARIA PLOUZANE GeofieldWhere to apply WebsiteContact CityLOCMARIA PLOUZANESTATUS: EXPIRED
EURAXESS