Mediterranean Institute of Oceanography

In oligotrophic regions like the Mediterranean Sea, vertical nutrient distribution plays a key role in controlling primary production via upward fluxes. In spring 2023, the BioSWOT-Med campaign explored how fine-scale ocean dynamics modulate nutrient availability in the North Balearic Front. Combining SWOT satellite observations with targeted Lagrangian sampling, the study focused on a 50 km domain encompassing contrasting water masses at and across the front, and a fine-scale anticyclonic eddy embedded within southern waters. High-resolution nutrient profiles revealed a clear two-level structure: at the regional scale, northern waters showed shallower nutriclines and steeper vertical nutrient gradients; at finer scale, the anticyclonic eddy exhibited even deeper clines and weaker gradients compared to its surroundings. A local relation between SWOT sea surface height and the nutricline highlighted the coupling between physical fine-scale structures and nutrient dynamics, with further implications for un- derstanding nutrient supply and biogeochemical functioning in oligotrophic marine sys- tems.

Near-inertial waves (NIWs) are an important source of turbulence for the ocean interior. Mesoscale anticyclonic eddies are known to facilitate their propagation at depth while trapping them. However, in-situ observations have so far focused on large (>50 km radius), energetic eddies, whereas most of the ocean is populated by smaller, moderately energetic fine-scale structures. Are these smaller structures efficient to trap NIWs and enhance turbulence? Here, we present in-situ observations from the BioSWOT-Med 2023 cruise addressing this issue by surveying a fine-scale frontal area of the North Balearic front, assisted by the first high-resolution Sea Surface Height images of the new SWOT satellite mission during its Calibration/validation phase. We explore how fine scales modulate the evolution of turbulence below the mixed layer after experiencing two consecutive strong wind events. We show that turbulence remains low in the front and its cyclonic side, while being greatly enhanced in the anticyclonic side. The latter side is dominated by a fine-scale anticyclone (12.8 km of radius, Rossby number of 0.5) that trapped NIWs down to 300 m depth, increasing turbulent dissipation level to several 10-8 W/kg. Estimations of the NIW-induced vertical kinetic energy flux are about 1 to 10 times stronger than previous estimations outside and inside mesoscale anticyclones (5-10 mW/m2 vs 0.5-10 mW/m2). These results suggest that moderately energetic fine-scale structures are as important to structure flows and turbulence as large and intense structures found in western boundary currents and upwelling systems, addressing new challenges for their parameterization in Earth system models.

Understanding the pathways of floating material at the surface ocean is important to improve our knowledge on surface circulation and for its ecological and environmental impacts. Virtual particle simulations are a common method to simulate the dispersion of floating material. To advect the particles, ocean models’ velocities are usually used, but only recent ones include tidal forcing. Our research question is: What is the effect of tidal forcing on virtual particle dispersion and accumulation at the ocean surface? As inputs we use velocity outputs from eNATL60, a twin simulation with and without tidal forcing. We focus on the Açores Islands region and we find: 1) Surface particles have a larger displacement, but a lower distance travelled with than without tidal forcing 2) Surface accumulation seasonal differences depend on the spatial scale of the ocean structures 3) A greater variability in surface accumulation is present with tidal forcing.

Predicting species survival in the face of climate change requires understanding the drivers that influence their distribution. Emperor penguins (Aptenodytes forsteri) incubate and rear chicks on landfast sea ice, whose extent, dynamics, and quality are expected to vary substantially due to climate change. Until recently, this species' continent-wide observations were scarce, and knowledge on their distribution and habitat limited. Advances in satellite imagery now allow their observation and characterization of habitats across Antarctica at high resolution. Using circumpolar high-resolution satellite images, unique fast ice metrics, and geographic and biological factors, we identified diverse penguin habitats across the continent, with no significant difference between areas with penguins or not. There is a clear geographic partitioning of colonies with respect to their defining habitat characteristics, indicating possible behavioral plasticity among different metapopulations. This coincides with geographic structures found in previous genetic studies. Given projections of quasi-extinction for this species in 2100, this study provides essential information for conservation measures.

Gorgonian population after the 2022 mass mortality event (MME) in the Calanques National Park. The year 2022 was marked by a historic gorgonian MME. This study describes the consequences for the red gorgonian (Paramuricea clavata) and red coral (Corallium rubrum) populations in the Calanques National Park (Marseille, France).

Abstract The aim of this article is to study the early effects of a recent marine reserve on the fish population, the Palavas Coastal Marine Reserve (PCMR), created in 2016 on fishermen initiative. This recent reserve, covering 100 ha and located 2.6 km from the coast at N 43°30.6845, E 3°58.4635, constitutes almost entirely a protected zone, with a ban on any fishing activity. The abundance of the fish populations and the size and biomass of the target species have been studied for the period of the first 4 years of protection. An inventory of fish populations was carried out using the scuba diving transect method in the rocky substrate of three zones: a large enhanced protection zone (EPZ) where only navigation was allowed,, a small restricted zone (RZ), where scuba diving was admitted, and an off-reserve zone (ORZ). Monitoring of this recent reserve shows significant increases in overall abundance and changes in population assemblages within the third year of protection. The biomass of target species tripled in the EPZ showing a refuge effect despite the fact that the fishing ban was not always respected during this implementation period. However, the behaviour patterns of the fish, which are more or less fearful of divers depending on the study area, do not offer an adequate basis for determining differences in populations between the EPZ and the RZ.

Stera-3β,5α,6β-triols make useful tracers of the autoxidation of Δ5-sterols. These compounds are generally analyzed using gas chromatography–mass spectrometry (GC-MS) after silylation. Unfortunately, the 5α hydroxyl groups of these compounds, which are not derivatized by conventional silylation reagents, substantially alter the chromatographic properties of these derivatives, thus ruling out firm quantification of trace amounts. In this work, we developed a derivatization method (trifluoroacetylation) that enables derivatization of the three hydroxyl groups of 3β,5α,6β-steratriols. The derivatives thus formed present several advantages over silyl ethers: (i) better stability, (ii) shorter retention times, (iii) better chromatographic properties and (iv) mass spectra featuring specific ions or transitions that enable very low limits of detection in selected ion monitoring (SIM) and multiple reaction monitoring (MRM) modes. This method, validated with cholesta-3β,5α,6β-triol, was applied to several environmental samples (desert dusts, marine sediments and particulate matter) and was able to quantify trace amounts of 3β,5α,6β-steratriols corresponding to several sterols: not only classical monounsaturated sterols (e.g., cholesterol, campesterol and sitosterol) but also, and for the first time, di-unsaturated sterols (e.g., stigmasterol, dehydrocholesterol and brassicasterol).

In this work, a search for nuclearites of strange quark matter by using nine years of ANTARES data taken in the period 2009–2017 is presented. The passage through matter of these particles is simulated taking into account a detailed description of the detector response to nuclearites and of the data acquisition conditions. A down-going flux of cosmic nuclearites with Galactic velocities (β = 10-3) was considered for this study. The mass threshold for detecting these particles at the detector level is 4 × 1013 GeV/c 2. Upper limits on the nuclearite flux for masses up to 1017 GeV/c 2 at the level of ∼ 5 × 10-17 cm-2 s-1 sr-1 are obtained. These are the first upper limits on nuclearites established with a neutrino telescope and the most stringent ever set for Galactic velocities.