Search

The short term (hourly scale) variability of heterotrophic prokaryote (HP) vertical distribution and respiratory activity, was investigated in the north-western (NW) Mediterranean Sea. HP vertical distribution was determined on board by flow cytometry analysis of seawater samples collected by series of CTD casts. Cell counts and viability were determined for all samples. HP respiratory rates were determined later in the laboratory from filtered seawater samples (23 dm3) from 300–1 150-m depth. The average cell viability was 94.8%±2.2% (n=240). There was no accumulation of dead cells, due to quick decay of damaged cells. In the epipelagic layer, three HP groups were distinguished, two (HNA1, HNA2) whose cells exhibited a high nucleic acid content and one (LNA) with low nucleic acid content cells. HNA2 was most populated at 50 m but not detected at 90 m and below, presumably aerobic anoxygenic photoheterotrophic bacteria (AAPs). The variability in HP abundance was mainly confined in the upper 80 m. A few secondary peaks of HP abundance were observed (80–150 m) in connection with abundance troughs in the surface layer. HP cells were continuously present in a wide layer around 500 m (mean 191×103 cells/cm3). Below this layer, HP abundance randomly exhibited peaks, coupled to respiratory rate peaks. The HP abundance and variability in the water column was suppressed during a strong wind event. The observed sporadic variability was tentatively interpreted through a pulsed carbon-export mechanism induced by the microorganism production of dissolved polysaccharides, followed by flocculation and rapid sinking. This mechanism would thus contribute to (i) preventing organic matter accumulation in the epipelagic layer, (ii) seeding the water column with live HP cells, and (iii) supplying the aphotic water column with fresh and labile organic matter. This important vertical flux mechanism needs further observations and modelling.

International audience; Echosounders are widely used to quantify fish behavior, fish stocks, and zooplankton biomass. Acoustic Doppler Current Profilers have also been used to accurately measure currents in all of the world’s major water bodies over the last 30 years. The present work evaluates the performance of a combined echosounder/ADCP system, the Nortek Signature100, for simultaneous biomass assessment and current profile data analysis. Due to its combined current profiling and scientific echosounding capabilities, the system is seeing increased usage in biomass flux applications, particularly in Antarctic krill research. However, capabilities of the system are still being studied and the present work aims to expand characterization of its performance. To that effect, a four month deployment was carried out by the French National Center for Scientific Research (CNRS) in the Mediterranean Sea with an up-looking Signature100 mounted atop the ALBATROSS mooring line. The line was at a total water depth of 2420 m and its top was approximately 370 m below the surface. Data show significant variations in scattering conditions between daytime and nighttime due to diel vertical migration (DVM), often unrelated to horizontal velocity fluctuations, highlighting not only the multiple frequency band capabilities of the system (up to 7 bands), but also the strength of the combined echosounder and current profiling functions. Echoview, a commercial software package for hydroacoustic data processing, was used to further explore the spatial and temporal patterns of the organisms observed in the echosounder data. A semi-automated technique was implemented to efficiently and objectively clean (e.g. remove interference generated by passing ship traffic), classify (e.g. based on relative frequency response or morphology), and characterize the narrow bandwidth and pulse compressed echosounder data by generating outputs that can contribute to the management and monitoring of aquatic resources.

Ocean Sciences Meeting (OSM), 16-21 February 2020, San Diego, CA, USA.- 1 page, 3 figures, The deep sea remains one of the less known environment on Earth and is characterized by high pressure, low availability of organic matter and absence of light. While there are still numerous discoveries concerning the diversity and adaptations of deep-sea organisms to their environement, this ecosystem is under an increasing anthropogenic pressure such as climate-related stressors (warming, acidification and deoxygenation), deep-sea fishing, human pollution (microplastics, POP), oil and gas extraction and could face new threats from emerging industries (e.g. mineral mining). How these changes will affect biodiversity and ecosystem functioning is one question of major importance for the future. In the darkness of the oceans, several organisms have the capability to emit light: called bioluminescence. Recent studies quantified that as much as 75% of pelagic and about 40% of benthic organisms are known to be bioluminescent. In this framework, we present a new deep-sea crawler, BathyBot, to be dedicated to the long-term exploration of deep-sea ecosystems allowing biological and-geochemical surveys. BathyBot will be deployed in 2020 in the Mediterranean Sea, at the MEUST-NUMerEnv/KM3NeT site, to strength the ecological-based monitoring capability of the European Multidisciplinary Seafloor and water column Observatory (EMSO ERIC) network. BathyBot will be able to explore an area of about 15 000 m2 at a depth of 2500m and will be devoted to 1) observe and monitor the dynamics of deep-sea pelagic and benthic organisms, 2) better define the occurrence and functions of bioluminescence in situ (increasing the dataset of bioluminescence records), 3) explore relationships between deep-sea organisms, biogeochemical (carbon content, oxygen concentrations) and environmental variables (temperature, salinity, current) in the context of global changes and their effects on the deep ocean, and 4) investigate benthic biogeochemical processes through the use of oxygen microprofiling in sediment porewaters, This work is funded by UE FEDER NUMerEnv project (number: 1166-39417, 2017), CNRS-INSU Moyens Mi-Lourd 2019 and VICAT-Tangram-MIO project

American Geophysical Union (AGU) Fall Meeting, 9-13 December 2019, San Francisco, EMSO is a European Research Infrastructure Consortium (ERIC) with 8 member countries. It is coordinated by a central management office and promotes monitoring services offered by 11 fixed-point deep-sea and water column observatories around Europe, from the Atlantic, through the Mediterranean, and to the anoxic Black Sea. EMSO aims are to advance marine science and technologies in the frame of sustainable development policies concerning ocean health, biodiversity, climate, and environmental changes. EMSO provides Science Services, in the form of data and/or access to the regional distributed observatory locations for experiments or testing of new equipment. EMSO ERIC is in its second year of operation, and its challenge is to turn the diversity of technical approaches and science priorities of each regional distributed observatory locations into a strength for building robust network-scale best practices, labels, and science services. This presentation reports on collaborative work initiated in recent months by EMSO, primarily within the Science Service Group, focusing on 3 practical goals: 1) offer online access, Quality Control (QC) and adequate data management tools for deep-water salinity and temperature data from five EMSO sites; 2) develop and promote a standard sampling and analytical procedure for microplastic pollution assessments to be performed at each EMSO site during maintenance cruises; and 3) explore the needs of the growing group of users of marine acoustics data (e.g. geohazards, marine mammals, sound pollution, marine transport) and design online access, QC and suitable scan-visualisation tools for acoustic data records. Our goal is, through and beyond EMSO Science Services, to help build smart ocean observation systems that meet the growing knowledge needs on natural and anthropogenic processes in the ocea

We report on data from an oceanographic cruise, covering western, central and eastern parts of the Mediterranean Sea, on the French research vessel Tethys 2 in May 2015. This cruise was fully dedicated to the maintenance and the metrological verification of a biogeochemical observing system based on a fleet of BGC-Argo floats. During the cruise, a comprehensive data set of parameters sensed by the autonomous network was collected. The measurements include ocean currents, seawater salinity and temperature, and concentrations of inorganic nutrients, dissolved oxygen and chlorophyll pigments. The analytical protocols and data processing methods are detailed, together with a first assessment of the calibration state for all the sensors deployed during the cruise.

The objective here is to review the practical accuracy and the precision of the existing oxygen sensors used in oceanography. The idea is to review all oxygen sensors mounted on fixed and lagrangian platforms (mooring, CTD profiler, glider, ARGO floats) used on coastal observatories. This report synthetizes the past experiences and recommendations for a better use of oxygen sensors in order to improve the quality of the oxygen data for scientific exploitations. European commission grant 262584 (JERICO) Published Report produced during the JERICO European project (2011-2015) grant 262584 Current 14.A Dissolved oxygen Manual (incl. handbook, guide, cookbook etc)