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Studies assessing potential measures to counteract the marine deoxygenation attributed to anthropogenic activities have been conducted in a few coastal environments and at regional scale, but not yet on a global scale. One way toward global scale artificial oxygenation would be to use oxygen produced as a by-product from hydrogen-production through electrolysis. The low-carbon footprint renewable production of hydrogen from offshore wind energy offers such a possibility. Here, we assessed the potential of this artificial oxygenation method on a global scale using a coupled physical-biogeochemical numerical model. The anthropogenic oxygen source scenario assumes worldwide adoption of hydrogen, considering demographic changes and the feasibility of offshore wind turbine deployment. Following this scenario, artificial oxygenation had a negligible effect on the overall oxygen inventory (an increase of 0,07 %) but showed a reduction in the overall volume of Oxygen Minimum Zones (OMZ) between 1,1–2,4 %. Despite the decrease in the mean OMZ volume globally, OMZs display distinct and contrasting regional patterns notably due to the oxygen impacts on the nitrogen cycle. Artificial oxygenation can inhibit denitrification resulting in a net gain of nitrate that promotes locally and remotely increased biological productivity and consequent respiration. Increased respiration could ultimately lead to an oxygen loss at and beyond injection sites as in the Tropical Pacific and Indian Ocean and particularly expand the Bay of Bengal OMZ. In contrast, the tropical OMZ shrinkage in the Atlantic Ocean is attributed to oxygen enrichment induced by advective transport into the OMZ, while the absence of denitrification in this area precludes any biochemical feedback effect on oxygen levels. These results suggest that the impacts of artificial oxygenation on oxygen concentrations and ecosystems are highly non-linear. It can produce unexpected regional responses that can occur beyond the injection sites which make them difficult to forecast.

Eastern boundary upwelling systems feature strong zonal gradients of physical and biological properties between cool, productive coastal oceans and warm, oligotrophic subtropical gyres. Zonal currents and jets (striations) are therefore likely to contribute to the transport of water properties between coastal and open oceanic regions. For the first time, multi-sensor satellite data are used to characterize the time-mean signatures of striations in sea surface temperature (SST), salinity (SSS), and chlorophyll-a (Chl-a) in subtropical eastern North/South Pacific (ENP/ESP) upwelling systems. In the ENP, tracers exhibit striated patterns extending up to ~2500 km offshore. Striated signals in SST and SSS are highly correlated with quasi-zonal jets, suggesting that these jets contribute to SST/SSS mesoscale patterns via zonal advection. Striated Chl-a anomalies are collocated with sea surface height (SSH) bands, a possible result of mesoscale eddy trains trapping nutrients and forming striated signals. In the ESP, the signature of striations is only found in SST and coincides with the SSH bands, consistently with quasi-zonal jets located outside major zonal tracer gradients. An interplay between large-scale SST/SSS advection by the quasi-zonal jets, mesoscale SST/SSS advection by the large-scale meridional flow, and eddy advection may explain the persistent ENP hydrographic signature of striations. These results underline the importance of quasi-zonal jets for surface tracer structuring at the mesoscale.

The aim of this work is to evaluate the efficiency, benefits and costs of different strategies for managing an epidemic described by a classic SEIRS model. Non-Pharmaceutical Interventions are taken by health authorities in order to remove a certain proportion of people from the chain of contamination, such as quarantine, partial lockdown as well as teleworking. We further assume that the intensity of protective measures is infected dependent. Depending on the choice of the infected dependent control function, we show that it is possible to create new endemic equilibria or change the stability of the diseasefree equilibrium. We present the mathematical analysis, existence and stability properties of equilibria. We present several management strategies grouped into four main classes. Appart from constant level strategies, we particularly study the effects of management strategies that allow the number of cases to be stabilized at a target low endemic level or else to generate an "Allee" effect that allows to extinguish the epidemic below some threshold. We compare the different strategies and discuss the opportunity to apply the method in the case of the SARS-CoV-2 epidemic.

Since the onset of AWA, a number of studies have focused on the management and ecology in West Africa. Here we provide a short insight of the main highlights on a selection of contrasted modelling case studies. Understanding the functioning of the ecosystem is essential to promote ecosystem approach to fisheries management and the marine environment (EAMME) and path providing advices to decision makers and managers. In the EAMME, the civil society addressed various questions to AWA on which specific models have been developed to provide at least first insight to the answers, e.g., on the effect of artificial reef implementation in marine protected area; the possible equilibriums between national fisheries sharing a same trans-boundary fish stock; the feedback between local exploitation, fish market and fisheries mobility, the responses of a fishery to economic, biologic and management parameters, the spatial variability of primary productivity as well oceanographic circulation at regional level or the fish egg advection over the continental shelf. More complex modelling exercise have also been conducted taking advantage of previous research led on sardinella aurita. In this way a coupled model taking into account environmental variability, fish growth and spatial behaviour was developed. We present as example new hypothesis on adult mediated connectivity between EEZ, inter-annual variability and interest to work on climate change with such model. We propose a prospective of what further research could be conducted to continue to bring up relevant information for a sub-regional EAMME in North West Africa fostering exchanges between modellers and marine scientists and all stakeholders.

The El Niño Southern Oscillation (ENSO) produces global marine environment conditions that can cause changes in abundance and distribution of distant fish populations worldwide. Understanding mechanisms acting locally on fish population dynamics is crucial to develop forecast skill useful for fisheries management. The present work addresses the role played by ENSO on the round sardinella population biomass and distribution in the central-southern portion of the Canary Current Upwelling System (CCUS). A combined physical-biogeochemical framework is used to understand the climate influence on the hydrodynamical conditions in the study area. Then, an evolutionary individual-based model is used to simulate the round sardinella spatio-temporal biomass variability. According to model experiments, anomalous oceanographic conditions forced by El Niño along the African coast cause anomalies in the latitudinal migration pattern of the species. A robust anomalous increase and decrease of the simulated round sardinella biomass is identified in winter off the Cape Blanc and the Saharan coast region, respectively, in response to El Niño variations. The resultant anomalous pattern is an alteration of the normal migration between the Saharan and the Mauritanian waters. It is primarily explained by the modulating role that El Niño exerts on the currents off Cape Blanc, modifying therefore the normal migration of round sardinella in the search of acceptable temperature conditions. This climate signature can be potentially predicted up to six months in advance based on El Niño conditions in the Pacific. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.