Dense mesopelagic sound scattering layer and vertical segregation of pelagic organisms at the Arctic-Atlantic gateway during the midnight sun

Changes in vertical and spatial distributions of zooplankton and small pelagic fish impact the biological carbon pump and the distribution of larger piscivorous fish and marine mammal species. However, their distribution and abundance remain poorly documented at high latitudes because of the difficulties inherent to sampling relatively fast-moving organisms in ice-covered waters. This study documents the under-ice distribution of epipelagic and mesopelagic organisms at the Arctic-Atlantic gateway in spring, during the midnight sun period, using ice-tethered and ship-based echosounders. An epipelagic surface scattering layer composed of copepods consistently occupied the top 60 m and was associated with cold polar surface water (mean temperature of -1.5°C). A mesopelagic deep scattering layer (DSL), partly composed of fish, persisted between 280 m and 600 m and was associated with modified Atlantic water. Backscattering strength within the DSL was higher than previously reported in the Arctic and north Atlantic, and increased by two orders of magnitude over the continental slope where one of the Atlantic water pathways enters the Arctic Ocean. Mesopelagic organisms did not perform diel vertical migrations. The consistent segregation between copepods at the surface and their predators at mesopelagic depths suggests limited predator-prey interactions during the midnight sun period, even under the ice cover. Predation on copepods by mesopelagic organisms, including fish, could thus be limited to very pulsed events during the seasonal vertical migration of copepods to and from overwintering depths. This suggests that the arctic mesopelagic food web may be decoupled from secondary production in the epipelagic layer throughout most of the year

Sea-ice decline could keep zooplankton deeper for longer

As Arctic sea ice deteriorates, more light enters the ocean, causing largely unknown effects on the ecosystem. Using an autonomous biophysical observatory, we recorded zooplankton vertical distribution under Arctic sea ice from dusk to dawn of the polar night. Here we show that zooplankton ascend into the under-ice habitat during autumn twilight, following an isolume of 2.4 × 10−4 W m−2. We applied this trigger isolume to CMIP6 model outputs accounting for incoming radiation after sunset and before sunrise of the polar night. The models project that, in about three decades, the total time spent by zooplankton in the under-ice habitat could be reduced by up to one month, depending on geographic region. This will impact zooplankton winter survival, the Arctic foodweb, and carbon and nutrient fluxes. These findings highlight the importance of biological processes during the twilight periods for predicting change in high-latitude ecosystems

Pelagic organisms avoid white, blue, and red artificial light from scientific instruments

In situ observations of pelagic fish and zooplankton with optical instruments usually rely on external light sources. However, artificial light may attract or repulse marine organisms, which results in biased measurements. It is often assumed that most pelagic organisms do not perceive the red part of the visible spectrum and that red light can be used for underwater optical measurements of biological processes. Using hull-mounted echosounders above an acoustic probe or a baited video camera, each equipped with light sources of different colours (white, blue and red), we demonstrate that pelagic organisms in Arctic and temperate regions strongly avoid artificial light, including visible red light (575–700 nm), from instruments lowered in the water column. The density of organisms decreased by up to 99% when exposed to artificial light and the distance of avoidance varied from 23 to 94 m from the light source, depending on colours, irradiance levels and, possibly, species communities. We conclude that observations from optical and acoustic instruments, including baited cameras, using light sources with broad spectral composition in the 400–700 nm wavelengths do not capture the real state of the ecosystem and that they cannot be used alone for reliable abundance estimates or behavioural studies

Microparticles from patients with metabolic syndrome induce vascular hypo-reactivity via Fas/Fas-ligand pathway in mice

Peer reviewedPublisher PD

Composition, distribution, and life history strategies of mesopelagic fauna in a changing Arctic Ocean

Micronekton and zooplankton inhabit the mesopelagic zone (200-1,000 m depth) which represents a unique environment in the global ocean where low-light levels structure predator-prey interactions. Because of the central position of mesopelagic organisms in food webs and the strong vertical gradient in light intensity, these animals conduct light-mediated diel vertical migrations (DVM) to maximize feeding while limiting mortality through visual predation. DVM contribute to the biological carbon pump by actively transporting carbon from the upper ocean to greater depths. The extreme light climate prevailing at high latitudes is hypothesized to prevent DVM during the midnight sun and polar night periods and hence prevent the establishment of viable mesopelagic populations in the Arctic Ocean. Yet, recent observations of mesopelagic layers in the European Arctic and the Central Arctic Ocean challenge this paradigm. There remain uncertainties regarding the spatial extent, species composition, life history strategies, and environmental drivers of the occurrence of mesopelagic organisms in the Arctic Ocean. Here, I used acoustic data collected at different spatial and temporal scales from multiple regions of the Arctic Ocean to investigate the distribution, structure, and dynamics of Arctic mesopelagic organisms. I demonstrate that mesopelagic organisms are commonly found in the Arctic Ocean and identified two distinct species assemblages that may be representative of larger biogeographic provinces. The seasonal vertical distribution of mesopelagic organisms generally followed a light comfort zone – a narrow range of light intensities. The seasonal cycle was characterized by two phases of active feeding on Calanus copepods in spring and autumn interspersed by oversummering and overwintering periods of vertical segregation with Calanus during the polar night and midnight sun. While the light comfort zone hypothesis provides a comprehensive framework for understanding the structure and dynamics of the mesopelagic zone, not all size classes and taxa adhere to this hypothesis. In the Arctic, mesopelagic organisms exhibit complex and flexible behaviours to accommodate a broad range of changing environmental conditions. I conclude that the mesopelagic ecological niche is widespread in the Arctic Ocean. Future studies of the biological carbon pump and of trophic interactions in the Arctic should consider and include the mesopelagic niche

Associations between herbivorous zooplankton, phytoplankton and hydrography in Porsangerfjord, northern Norway

During three cruises in April, May and November 2014 in Porsangerfjord, northern Norway, the role of hydrography and phytoplankton composition in shaping zooplankton vertical distribution was studied. Simultaneous collection of biological (phytoplankton and zooplankton distribution/abundance) and environmental data (temperature, salinity, density, Chlorophyll a) was sampled using a high-resolution autonomous VPR. Phytoplankton species composition was also determined using cell counts. Two stations representing two different hydrographic conditions were sampled, one in the inner part and the other in the outer part of the fjord. The phytoplankton bloom started in May. The outer part was dominated by Phaeocystis pouchetii and the inner part by diatoms (Chaetoceros spp.). The inner part of the fjord was dominated by small copepods species like Pseudocalanus spp., Microsetella norvegica, and Oithona spp. whereas the outer part was dominated by large copepods like Calanus finmarchicus. Zooplankton distribution changed over season, in early bloom they were spread over the water column, during the bloom they were linked to phytoplankton vertical distribution and in the winter situation they were at depths. Hydrography was not the only factor responsible for herbivorous zooplankton distribution. Herbivorous zooplankton was affected by phytoplankton species composition. C. finmarchicus and Pseudocalanus spp. avoided the dense layer of P. pouchetii while M. norvegica was observed grazing on P. pouchetii. Zooplankton vertical distribution was therefore linked to both abiotic (hydrography) and biotic (phytoplankton composition and distribution) factors which varied in importance throughout the season

Etude de pratique des méthodes diagnostiques d'embolie pulmonaire aux urgences (EMDEPU 2)

ANGERS-BU Médecine-Pharmacie (490072105) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Polyphenols impact on vascular dysfunction associated with obstructive sleep apnea: a randomized controlled trial

International audienc

Polyphenols impact on vascular dysfunction associated with obstructive sleep apnea: a randomized controlled trial

International audienc

Etude sur les contaminants émergents dans les eaux françaises - Rapport de l'étude prospective sur les contaminants émergents dans les eaux littorales de la métropole et des DOM

This study contributes to inventory programme on emerging pollutants in French waters and to the general reflection which will enable to update the list of relevant substnaces to be included in the new monitoring programmes to come. This work concerns the coastal part of the inventory programme on marine waters and sediments of France and five overseas french departments (OFD). In this goal, passive sampling techniques and direct extraction techniques have been tested through the implementation of in situ systems integrators POCIS (Polar Organic Chemical Integrative Sampler) and the extraction by SBSE bars (Stir bar sorptive extraction) directly in the waters sampled. Finally, analyzes of sediment completed the acquisition of data. Arount 40 stations were sampled for shore waters and sediments were collected from 7 stations in France and 5 stations in the OFD (one station/OFD). In analytical terms, 1054 analyzes were carried out on POCIS membranes and only 64 data exceeded the limit of detection (LD), 12726 analyzes came from SBSE extractions and 304 were above the LD and 1536 analyzes in sediment showed that 237 data were above the limit of quantification (LQ). Finally, 169 different substances were investigated and 68 of them were detected at least once in water or sediment. The lack of replicates for POCIS analyzes and those in the sediment limited the statistical treatment of data. The results were used to determine the level of contamination, the detection frequency (FD), the distribution of substances between France and OFD, the comparison with environmental thresholds (the PNEC) and the origin/use of the substances. In littoral waters, 32 substances were identified and 19 were quantified. In the sediment, 47 substances were quantified. Nine substances were detected in both water and sediment. In France, the 15 substances that were quantified at higher frequencies (> 50 %, one out of 2 sites) were quantified in sediments. These are the congeners of PAHs (11 substances), organic forms of tin (2 substances), diethyl lead and 209 PBDE congener. In the OFD, the 22 substances that were quantified at higher frequencies (> 50 %, one out of 2 sites) were measured in sediments. These are congeners of PAHs (13 substances) , alkylphenols ( 3 molecules: the mono and diethoxyate nonylphenol and the 4-ter butylphenol ), the organic forms of tin (2 substances), products of metabolism insecticide DDT ( 2 products), diethyl lead and the 209 PBDE congener. The study of the highest concentrations distribution of substances between France and OFD shows that the 5 (among 19 molecules) highest concentrations in water and the 6 (among 47 molecules) highest concentrations in sediments are found in OFD. Reference to PNEC indicates that four pesticides in water and 11 different substances in sediments exceed the environmental thresholds. Substances with highest detection frequency are found in the sediment. The distribution of data by use or nature of the substance shows that plasticizers and pesticides predominate in raw water, both in France and overseas departments while PAHs in sediments dominate in France and in OFD.Cette étude contribue au programme d’inventaire des substances chimiques émergentes dans les eaux françaises et à la réflexion qui doit permettre d’actualiser la liste des substances pertinentes à surveiller de manière régulière dans le cadre des nouveaux programmes de surveillance. Ce travail concerne la partie littorale de l’inventaire, sur les eaux brutes et les sédiments de la métropole et des 5 DOM. Dans ce cadre, des techniques d’échantillonnage passif (EP) et d’extraction directe ont été testées grâce à la mise en place in situ de systèmes intégrateurs POCIS (Polar Organic Chemical Integrative Sampler) et à l’extraction par des barres SBSE (Stir Bar Sorptive Extraction) directement dans les eaux échantillonnées. Enfin des analyses de sédiments ont complété l’acquisition des données. L’eau d’une quarantaine de stations a été échantillonnée et des sédiments ont été prélevés sur 7 stations en métropole et dans 5 stations dans les DOM (une station par DOM). En termes analytiques, 1054 analyses ont été réalisées sur les membranes POCIS et 64 dépassaient la limite de détection (LD), 12726 analyses ont concerné les extractions par SBSE pour 304 résultats situés au dessus de la LD et 1536 analyses effectuées dans le sédiment ont donné 237 valeurs supérieures à la limite de quantification (LQ). Au bilan 169 substances différentes ont été recherchées et 68 d’entre elles ont été détectées au moins une fois dans l’eau brute ou le sédiment. L’absence de réplicats pour les analyses POCIS et celles dans le sédiment a limité le traitement statistique des données. Les résultats ont permis de déterminer le niveau de contamination, la fréquence de détection (FD), la distribution métropole/DOM des substances, la comparaison avec les seuils environnementaux (PNEC) et l’origine des substances. Dans l’eau 32 substances ont été identifiées et 19 ont été quantifiées. Dans le sédiment 47 substances sont quantifiées .Neuf substances sont détectées à la fois dans l’eau et le sédiment. En métropole, les 15 substances quantifiées aux plus hautes fréquences (> 50%, soit un site sur 2) sont quantifiées dans les sédiments. Ce sont les congénères de la famille des HAP (11 substances), des formes organiques de l’étain (2 substances), le plomb diéthyle et le congénère 209 des PBDE. Dans les DOM, les 22 substances quantifiées aux plus hautes fréquences (> 50%, soit un site sur 2) sont mesurées dans les sédiments. Ce sont des congénères de la famille des HAP dans (13 substances), des alkylphénols (3 substances : nonylphénols mono et diéthoxylés et 4-ter butylphénol), des formes organiques de l’étain (2 substances), des produits de métabolisation de l’insecticide DDT (2 produits), du plomb diéthyle et du congénère 209 des PBDE. L’étude de la répartition des plus fortes concentrations entre la métropole et les DOM montre que les 5 (sur 19) concentrations les plus élevées mesurées dans l’eau et les 6 (sur 47) plus fortes concentrations mesurées dans les sédiments sont trouvées dans les DOM. Les substances mesurées aux fortes fréquences sont observées dans le sédiment. La référence à la PNEC indique le dépassement de la norme pour 4 pesticides dans l’eau brute et 11 substances diverses dans les sédiments. L’exploitation des données par usage ou nature des substances montre que les plastifiants et les pesticides sont majoritaires dans les eaux brutes, à la fois en métropole et dans les DOM alors que ce sont les HAP qui dominent dans les sédiments, en métropole et dans les DOM