French Research Institute for Exploitation of the Sea
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AMOBIO : Analyse multicritère des effets exercés par les obstacles en cours d’eau sur les communautés biologiques (diatomées, macroinvertébrés, poissons)
No full textLe programme de recherche AMOBIO (« Analyse multicritère des effets exercés par les obstacles en cours d’eau sur les communautés biologiques » , 2021 2024 ) est né d’un partenariat entre l’OFB (Office français de la biodiversité) et l’INRAE (Institut national de recherche pour l’agriculture, l’alimentation et l’environnement). Il a été financé par l’OFB et supporté en moyens conjointement par l’OFB et l’INRAE . Sa conceptualisation théorique a été réalisée par Olivier Dézerald (chercheur, INRAE) et Karl Kreutzenberger (chargé de mission, OFB) ; son exécution pour le présent rapport a été effectuée par Bastien Bourillon (postdoctorant, INRAE). Le pilotage du programme a amené la création d’un consortium de recherche d’une vingtaine de scientifiques afin de partager des expertises complémentaires sur les nombreuses thématiques scientifiques qu’il aborde. Ce consortium regroupe notamment des personnels de l’OFB, de l’INRAE, du MNHN (Museum n ational d’ histoire naturelle), du CNRS (Centre national de la recherche scientifique) adossés aux Universités de Rennes 2, de Paris 1 et de Lorraine. Le présent document est le rapport final du programme pour la période 2021 2024 . Un catalogue de métriques produit au cours du programme y est associ
Evaluating the role of physical mechanisms as possible triggers for turbidity currents in a deep ocean seamount
No full textTurbidity currents on continental margins are often attributed to cyclic climate variability and sea-level change, while the causes of deep ocean turbidites are as yet to be tested. The Atlantic Iberian margin provides a unique setting to contrast deep ocean and continental environments, including depression features that further protect from resuspension and erosion by along-slope bottom currents. We present records of low-frequency, non-periodic, climate-independent turbidites from three deep cores covering up to 426,000 years in the Tore seamounts area. By evaluating a range of physical oceanographic mechanisms, the breaking of internal waves and mesoscale Mediterranean-eddies against unstable slopes in the seamounts area arises as the most likely triggers that precondition the recurrence pattern of the observed deep ocean turbidites
Optimisation d’une bathymétrie dérivée satellite pour le lagon de Reao, Tuamotu
No full textBathymetric surveys are rare for isolated lagoons, but recent approaches offer promising prospects for reducing the costs associated with acquisitions, by coupling bathymetric in situ data with a satellite image (the satellite-derived-bathymetry SDB method). For coral ecosystems in particular, the use of an “Iterative Multi Band Ratio” algorithm has provided satisfactory results (Amrari et al., 2021). The reliability of the method, which has so far been developed on a shallow coastal barrier reef (< 4 m), nevertheless raises questions for deeper lagoons. In this study, we propose to test an SDB approach inspired by Amrari et al (2021) on an atoll lagoon in the Tuamotu archipelago, Reao. The most satisfactory results were obtained by segmenting the lagoon into several parts and optimising an SDB on each of the parts rather than on the whole lagoon. The bathymetric product obtained is considered satisfactory for feeding hydrodynamic models and ecological studies on the scale of the lagoon, with 77.6% of estimates within the error interval < 10%, and a mean square error of 1.35 m.Les levés bathymétriques sont rares pour les lagons isolés, mais des approches récentes offrent des perspectives prometteuses pour réduire les coûts associés aux acquisitions, en couplant les levés bathymétriques à une image satellite (méthode dite SDB « satellite-derived-bathymetry »). En particulier pour les écosystèmes coralliens, l’utilisation d’un algorithme « Iterative Multi Band Ratio » a fournit des résultats particulièrement satisfaisants (Amrari et al., 2021). La fiabilité de la méthode, jusqu’à présent mise au point sur un récif barrière côtier peu profond (< 4 m), pose néanmoins question pour les lagons plus profonds. Dans cette étude, nous proposons de tester une approche SDB inspirée de Amrari et al. (2021) sur un lagon d’atoll de l’archipel des Tuamotu, Reao. Les résultats les plus satisfaisants ont été obtenus en segmentant le lagon en plusieurs parties et en optimisant une SDB sur chacune des parties plutôt que sur l’ensemble du lagon. Le produit bathymétrique obtenu est jugé satisfaisant pour alimenter des modèles hydrodynamiques et des études écologiques à l’échelle du lagon, avec 77.6% des estimations comprises dans l’intervalle d’erreur < 10%, et une erreur quadratique moyenne de 1.35 m
Metrological concepts applied to Total Alkalinity measurements in seawater: reference materials, inter-laboratory comparison and uncertainty budget
No full textTotal alkalinity (TA) measurements in seawater are crucial for characterizing and monitoring the oceanic carbonate system. While international best practices and guidelines exist, the field still lacks widely available traceable reference materials and a well-established uncertainty budget of the measurement method. In this study, we applied key metrological principles – development of reference materials, inter-laboratory comparison and uncertainty quantification – to TA measurements. We developed two reference materials, including an artificial material with a rigorously characterized reference value and an associated uncertainty budget, being potentially traceable to the International System of units (SI). These materials were tested in an inter-laboratory comparison involving five laboratories and demonstrated the applicability and interest of the reference materials developed for quality control. Additionally, we established an uncertainty budget for the TA measurement method using two metrological approaches. The resulting expanded uncertainty was 5 µmol kg⁻¹ (k = 2) in TA, approaching the 4 µmol kg⁻¹ target set by the Global Ocean Acidification Observing Network for climate monitoring. These findings mark a significant step toward improving the quality and comparability of TA measurements, thereby strengthening long-term ocean carbonate system monitoring
From few to many maps: A fast map-level emulator for extreme augmentation of cosmic microwave background systematics datasets
No full textContext. Generating massive sets of end-to-end simulations of time-ordered data for Monte Carlo analyses in cosmic microwave background (CMB) experiments typically incurs exceedingly high computational costs. Aims. To address this challenge, we introduce a novel, fast, and efficient generative model built upon scattering covariances, the most recent iteration of the scattering transform statistics. This model is designed to augment by several orders of magnitude the number of map simulations in datasets of computationally expensive CMB instrumental systematics simulations, including their non-Gaussian and inhomogeneous features. Unlike conventional neural network-based algorithms, this generative model requires only a minimal number of training samples, making it highly compatible with the computational constraints of typical CMB simulation campaigns. While our primary focus is on spherical data, the framework is inherently versatile and readily applicable to 1D and 2D planar data, leveraging the localized nature of scattering statistics. Methods. We validated the method using realistic simulations of CMB systematics, which are particularly challenging to emulate, and performed extensive statistical tests to confirm its ability to produce new statistically independent approximate realizations. Results. Remarkably, even when trained on as few as ten simulations, the emulator closely reproduces key summary statistics including the angular power spectrum, scattering coefficients, and Minkowski functionals - and provides pixel covariance estimates with substantially reduced sample noise compared to those obtained without augmentation. Conclusions. The proposed approach has the potential to shift the paradigm in simulation campaign design. Instead of producing large numbers of low- or medium-accuracy simulations, future pipelines can focus on generating a few high-accuracy simulations that are then efficiently augmented using such a generative model. This promises significant benefits not only for current and forthcoming cosmological surveys such as Planck, LiteBIRD, Simons Observatory, CMB-S4, Euclid, and Rubin-LSST, but also for diverse fields including oceanography and climate science. We make both the general framework for scattering transform statistics, HealpixML, and the emulator, CMBSCAT, available to the community
In-Service Experience of the Behaviour of Deep Ocean Handling Ropes from the Pourquoi Pas ? and Marion Dufresne2 Oceanographic Vessels
No full textThis paper presents results from tests performed periodically to follow the tensile properties of HMPE deep water handling ropes used on two oceanographic vessels, the PourquoiPas? and the Marion Dufresne2. The SMASH Materials laboratory at IFREMER, in collaboration with DFO and Genavir, was involved in initial rope selection for these two ships and for other French oceanographic vessels (Atalante, Anita Conti), and then characterized samples removed throughout their service lifetimes during a 15-year study
Optimal control of a microbial growth model by means of substrate concentration and resource allocation
No full textResource allocation models have been proven to be a highly Effective tool to study the growth of microorganisms. Here, we use one such growth model describing the metabolism of a given bacterium in an artificial (e.g. biotechnological) environment. Tis model involves two controls, one quantifying the protein precursors allocation (i.e. the cellular internal control) and the other representing the nutrient concentration in the culture. We seek to determine the controls that maximize the resulting growth rate of cells living in this controlled environment. We first carry out a theoretical analysis of this optimal control problem (OCP) by means of the Pontryagin’s Maximum Principle (PMP). We show the bang-bang structure of the optimal resource allocation control. We fnd the environmental control to follow a bang-singular-bang structure, and give an expression for its singular arc depending on the state and costate given by the PMP. We solve the OCP in fixed final time using a direct optimization method, implemented on the BOCOP software. Tis resolution reveals an intrinsic period of the optimal control, corresponding to the solution of the periodic OCP in free final time. Moreover, we fnd a singular arc of the environment coinciding with the analytical expression given before. Our study highlights the optimality of periodic, non-constant environments in maximizing bacterial growth
Out of sight, but not out of mind: Key issues regarding seafloor macrolitter monitoring
No full textFollowing a number of meetings devoted to knowledge sharing, identification of key issues, and discussing the best ways to move forward, a wide international expert community is now able to provide recommendations regarding the monitoring of seafloor macrolitter through observation and imaging. As the seafloor constitutes a major sink for marine litter including plastics, it is important to acquire robust and extensive data on litter distribution, abundance, types and size ranges across marine habitats. This should be done through widely agreed, harmonised, and non-destructive methods encompassing advanced technologies. Training and capacity building are essential elements in this endeavour. Both new and legacy imagery are needed to establish baseline assessments and trends. Informing policy-making is indispensable for effective action through upstream and targeted measures, with seafloor macrolitter (and megalitter) being a vital part of the evidence base for global mitigation measures
Leachates from weathered polypropylene items, but not from polylactic acid, induce ecotoxicological effects on a marine diatom
No full textPlastic items released in the marine environment are subject to weathering processes which alter their surface physiochemical properties, and which can induce the leaching of associated chemicals from the polymer matrix to the aquatic media. Even though plastic leachates (i.e., an aqueous solution of released compounds) can induce negative effects on aquatic biota, the effects of plastic leachates from weathered plastics are still poorly known. The goal of our work was to assess the ecotoxicological effects of plastic leachates from pristine and weathered items on a marine diatom. To do so, we exposed the marine diatom Phaeodactylum tricornutum to the leachates from pristine and UV-weathered self-reinforced (SR-) polylactic acid (PLA) and polypropylene (PP) items. As a positive control, we assessed the response of the diatom growth to two associated compounds (dodecan-1-ol and 2,4-di-tert-butylphenol), components of the tested items. Weathered plastic items were obtained after being exposed to 57-day artificial ultraviolet radiation, simulating 18-months of solar exposure in central Europe. Our results indicate that neither leachates from pristine nor weathered SR-PLA items had adverse effects on P. tricornutum growth. This outcome was corroborated by the measured concentrations of associated compounds (i.e. dodecan-1-ol) in leachates, which were at least three orders of magnitude lower than the 72-h EC50 of diatom growth (dodecan-1-ol: 1.56 mg / L, 2,4,-DTBP: 1.52 mg / L). Leachates from weathered SR-PP items at full-strength concentration induced 51% greater growth inhibition than control treatments, and 43% greater inhibition than leachates from pristine SR-PP items at the same concentration. Our results suggest that leachates from the tested weathered SR-PP items inhibited the population growth of P. tricornutum, although at plastic concentrations above environmentally relevant levels