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The blackspot seabream is a highly appreciated species that has an important target of the Spanish and Moroccan fisheries in the transcontinental waters of the Strait of Gibraltar area (Gil, 2006). It is also one of the most exploited resources of the region, which has led to a notable drop of catches over the years, arriving to a vulnerable status nowadays. Consequently, a reduction of fishing mortality towards sustainability levels was recommended (GFCM, 2021). Improving our knowledge on the interaction of this species with its physical environment is a key issue in the efforts towards rebuilding the fishery target population until its maximum sustainable yield (Cowen et al., 2006). To gain insight into this interaction, a high-resolution circulation model coupled to a lagrangian tracking module has been employed, using eggs and larvae (early-life-stages, ELS) as purely passive particles advected by simulated currents. Several spawning scenarios consisting of different temporal (tidal phase and strength) and spatial (depths and sites) initial conditions have been analyzed to identify the most likely pathways of ELS dispersion. Eastward transport by the Atlantic Jet exiting the Strait of Gibraltar is the most influencing process in that dispersion. Regarding temporal fluctuations, fortnightly tidal modulation appears to be the prevailing factor determining the horizontal paths of ELS, being the spring tide responsible of the greatest scattering of eggs and larvae. Interestingly, the spatial distribution numerically simulated is consistent with results of larvae distribution obtained from samples collected during recent scientific surveys. The results presented in this study can be certainly different attending to the species strategy. The role of other important larval traits not included in this study requires also further research that may help decision-makers to establish biological rest periods that lead to maximize connectivity and sustainability.

The Guadalquivir (SW Spain) is a complex estuarine system where many factors converge: navigation of cargo ships, water intake and outtake for agricultural and aquaculture uses, its location bordering the Doñana National Park, etc. Recently, shore and marshes restoration are being considered [1,2]. For years the recovery of tidal marshes in the lower part of the estuary has been suggested as a solution to the degradation of the shores and to counteract possible negative consequences associated to bathymetric changes in the estuary [3]. However, recent studies have been carried out only with exploratory 1D models [3]. These studies, which are enough to provide a primary evaluation of trends, demand more detailed investigations with more complex computational models such as the one GOFIMA has developed in the Guadalquivir estuary using Delft3D. In this work, different domains that simulate a tidal flat have been created. These experiments test different surfaces, depths and locations for two different connections of the tidal flat with the navigation channel. The results are compared with a no-tidal flats configuration where only the main forcing (astronomical tide) is considered and where constant boundary conditions (ecological discharge ∿110 km from the mouth and salinity at the mouth) are fixed. This work aims to understand the effect of the recovery of marshes in the lower part of the estuary, assessing the modifications they originate on the tidal harmonics of surface oscillations and currents as well as salinity distribution along the estuary. It raises that the amount of water exchanged with the restored tidal flat and its location are the critical variables for the induced changes in tidal and saline dynamics. Future studies will include other physical variables such as temperature and possibly address more realistic cases of tidal marsh restoration. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.

Photogrammetry is one of the oldest but constantly evolving branch of computer vision. The main concept behind it is based on obtaining three-dimensional coordinates of a real word object from a series of pictures of it, collected from diferent locations. The outcome is a three-dimensional model of the object, on which any kind of virtual manipulation and quantitative measuring can be carried out. Several examples of both aerial (based on aerial photographs) and close-range (based on standard close-distance pictures) photogrammetry applications to diferent felds of marine science, are described, promoting the use of this technique as an undeniable aid for oceanographers, marine geologists and biologists.

The Guadalquivir River is dominated by the tidal fows coming from the Gulf of Cadiz, being the semidiurnal oscillation the most relevant in the area. Tidal constituents in the estuary are especially sensitive to variations in frequency due to tidal friction and resonance balance, and fuctuate with other harmonic components. In this study both sensitive analyses have been covered, providing an assessment of the frictional interactions between tidal constituents.

The significant role of reservoirs in the carbon cycling and the recent growth of dam building have increased the interest to evaluate carbon fluxes in these systems. In this work, we study the spatial and temporal variability in CO₂ (diffusive) and CH₄ (diffusive and ebullitive) fluxes from the water surface in a Mediterranean reservoir (El Gergal, Spain). During a whole year, CO₂ and CH₄ fluxes were measured monthly from the reservoir lacustrine and riverine zone. Additionally, we measured CO₂ flux from dry sediments of the reservoir drawdown area. CO₂ and CH₄ diffusive fluxes from the water surface were higher during mixing period, and the CO₂ flux was related to pH and Chl-a, suggesting primary production as a relevant driver. Conversely, CH₄ ebullitive flux was higher during thermal stratification. Dry exposed sediments constituted a net CO₂ source to the atmosphere showing higher CO₂ emissions in areas influenced by river or intermittent stream discharges. During the mixing period, the reservoir water surface was a net source of CO₂ to atmosphere whereas it was a CO₂ sink during the stratification period. However during the stratification period the reservoir drawdown zone increased due to lower water input and larger water demand, and consequently larger areas of previously submerged sediments became dry and exposed to the atmosphere. Therefore, ecosystem net CO₂ uptake during the thermally stratified period could be significantly diminished in Mediterranean reservoirs in future conditions, due to the predicted increase in the frequency and intensity of droughts expected for this region. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.

El voraz (Pagellus bogaraveo) es una especie de pez teleósteo demersal altamente apreciada tanto por su valor económico como gastronómico, que tiene un importante caladero en el Estrecho de Gibraltar. Dentro del ámbito científico, existe un consenso que considera que, para optimizar las pesquerías, simultáneamente a dejar de sobre explotar el recurso, es necesario hacer estudios de dinámica poblacional y conectividad. Con el objetivo de conocer mejor la dinámica poblacional de la especie y sus mecanismos de dispersión en el Mar de Alborán, se ha estudiado su conectividad hidrodinámica a partir de un modelo numérico [MITgcm], utilizando los estadios de vida temprana (huevos y larvas) como partículas virtuales lagrangianas advectadas por la dinámica mareal. Se han realizado análisis de sensibilidad en función de la variabilidad espacial y temporal. Para determinar la sensibilidad espacial, se definieron tres zonas de suelta en el Estrecho de Gibraltar, zona preferencial de desove del voraz y cinco profundidades de liberación desde la superficie hasta los 81 metros. Para determinar la sensibilidad temporal, se definieron ocho combinaciones de marea en función de la fase mareal y de la modulación quincenal (marea viva-marea muerta). Para cada uno de estos escenarios mareales iniciales se hicieron simulaciones de 60 días, que es la duración pelágica del voraz, en distintas fechas para estudiar la variabilidad subinercial asociada al forzamiento meteorológico, todo ello en el periodo comprendido entre diciembre de 2004 y abril de 2005 En conjunto se realizaron 480 simulaciones, de cuyo análisis se ha deducido que la modulación quincenal es el factor predominante para la dispersión horizontal, siendo el escenario de marea muerta el que produce una dispersión más baja y velocidad más uniforme de los huevos y larvas. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.

Data collected in the north and south channels of the main sill of the Strait of Gibraltar (Camarinal sill) are used to investigate processes connected to the internal hydraulics of the exchange through the Strait at tidal frequencies. Observations strongly suggest the setting up of hydraulic jumps at both the western and eastern flank of the sill, the latter associated with the reversal of the Mediterranean undercurrent during spring tides. The northern site is more sensitive to processes triggered by the formation and release of the jump formed east of the sill during intense enough ebb tide cycles, which is thus better traced at this location; the southern site detects more neatly the fluctuations and footprints associated with the hydraulic jump regularly formed to the west of the sill during flood tides. A detailed inspection of the high resolution bathymetry of the area reveals the existence of two enclosed depressions at either side of the sill, almost certainly carved by the bottom flow over the millennia, whose shape and morphology are suggestive of this spatial differentiation. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

European Geosciences Union (EGU) General Assembly 2018, 8-13 April 2018, Vienna, Austria.-- 1 page, The pathways and transformations of dense water overflows, which depend on small-scale interactions between flow dynamics and erosional-depositional processes, are a central piece in the ocean’s large-scale circulation. A novel, high-resolution current and hydrographic data set highlights the intricate pathway travelled by the saline Mediterranean Overflow as it enters the Atlantic. Interaction with the topography constraints its spreading. Over the initial 200 km west of the Gibraltar gateway, distinct channels separate the initial gravity current into several plunging branches depth-sorted by density. Shallow branches follow the upper slope and eventually detach as buoyant plumes. Deeper branches occupy mid slope channels and coalesce upon reaching a diapiric ridge. A still deeper branch, guided by a lower channel wall marked by transverse furrows, experiences small-scale overflows which travel downslope to settle at mid-depths. The Mediterranean salt flux into the Atlantic has implications for the buoyancy balance in the North Atlantic. Observations on how this flux enters at different depth levels are key to accurately measuring and understanding the role of Mediterranean Outflow in future climate scenarios

The blackspot seabream (Pagellus bogaraveo) is a commercially appreciated demersal fish, widespread in the North-eastern Atlantic and middle-western Mediterranean. The Strait of Gibraltar is an important fishing area where artisanal fleets from Spain and Morocco target this species using special longline gears known as “voracera”. Different assessments of the state of health of this species point to the same result: a clear overexploitation of the resource with no specific/joint management implemented yet. There is some agreement in literature in considering the Strait of Gibraltar as a specially energetic and dispersive spawning zone for this species. After the spawning, eggs and larvae (early life stages [ELS]) would be scattered to both sides of the Strait of Gibraltar, mostly to the breeding area close to Estepona, where high concentrations of juveniles occur. A high resolution hydrodynamic model coupled to a 3D Lagrangian particle tracking system is employed to assess the potential dispersal pathways of blackspot seabream ELS spawned in the Strait of Gibraltar. Recursive releases of passive tracers in virtual spawning spots in this zone are tracked under different conditions of tidal current, including fortnightly modulation, in order to obtain the spatial dispersion patterns of the studied species. Semidiurnal variability appears as a fundamental factor for horizontal dispersion and vertical displacement of the spawning products, determining the trajectories of the ripening ELS of the species. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.

Since 2004 a monitoring station located at the western exit of the Strait of Gibraltar (Espartel Sill), maintained with the joint efforts of the Physical Oceanography Group of the University of Málaga, the Spanish Institute of Oceanography laboratory of Cádiz and the Marine Science Institute of Andalusia, has been providing the longest series of water column current profiles ever collected in such a strategic site. The line is equipped with an up-looking long range current profiler capable to sample the water column up to few tents of meters from the surface. However, for both physical limitations of the line structure and electronic constraints of the instrument, the profiles miss the first 30 meters above the seafloor, a significant concern for a precise calculation of the Mediterranean outflow and the bottom layer dynamics. Since September 2016 a new high frequency down-looking current profiler has been included in the line, with the aim of covering the missing portion of the water column and precisely assessing the closure profile of the flow above the seafloor. The preliminary results are very encouraging and show a remarkable agreement between the profiles measured by both instruments: the boundary layer profile not only matches the closure curve suggested by the overhead profile, but even confirms the near-bottom diurnal modulation of the current suggested by previous observations, a feature that is expected to modify earlier estimations of the outflow. The resulting boundary layer is only few meters thick, revealing the high energy of the Mediterranean outflow in the strait, with flow speeds exceeding 1 m s-1 at only 3 m above the seafloor. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech