Lagrangian particle tracking for the assessment of the flushing efficiency of harbor structures: the case of the Port of the Bay of Algeciras, Strait of Gibraltar

The Bay of Algeciras, an inlet of about 9 x 11 km located at the eastern margin of the Strait of Gibraltar, opens to the south, where the Atlantic jet leaves the Strait and starts spreading into the Alboran Sea. In its western side, the Bay hosts one of the main ports in Europe, neuralgic base of the major traffic load from Europe to Africa and from Europa to the rest of the oversea countries. The massive transport of liquid and solid bulk or bunkering activity, daily carried out in the Bay, combined with the harsh weather conditions that often lash the zone, give the ideal scenario for an incipient ecological disaster. This high environmental risk motivates the interest for a deeper understanding of the small scale dynamics of the Bay and the role played by the port structures in case of oil spill or other surface contaminations. A series of Lagrangian particles tracking (LPT) experiments were carried out to investigate the flushing patterns of the Bay and 8 different docks inside the local port, under a representative variety of external conditions, such as tide phase and strength, and winds. A 2D LPT algorithm has been adapted to fully exploit the outputs of a very high resolution (∼30m) three-domain-nested hydrodynamic model, with the aim of resolving the complex circulation within the structures of the harbor. Winds are a clearly dominant factor, with westerlies featuring e-folding times one order of magnitude lower than easterlies. Fortnightly tidal modulation presents a counter-intuitive effect, with spring tides that, despite promoting higher ventilation in a first instance, end up providing higher accumulation of particles inside the docks and higher e-folding times than neap tides. Tide phase affects the current direction at the entrance of the docks during the first few hours of simulation and its effect is progressively masked throughout the experiment. In the 45% of the experiments, a significant quantity of particles flow out to the Alboran Sea (55% in the whole Bay experiment), confirming the importance of the Bay on the exportation of pollutant/properties to the nearby basin.Universidad de Málaga. Campus de Excelencia Internacional del Mar, CEIMAR. Campus de Excelencia Internacional Andalucía Tec

Mediterranean outflow and its link with upstream conditions in Alboran Sea

The Western Alboran Gyre (WAG) at the eastern entrance of the Strait of Gibraltar can influence the Mediterranean outflow (MOW) by favoring or hampering the flow of Levantine and Western Mediterranean (LIW and WMDW) waters, the main constituents of the MOW. Observations collected at Camarinal sill in the Strait and AVISO data are used to investigate this issue.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

The influence of tides on the exchange through the Strait of Gibraltar and on properties of the Mediterranean Sea

A. Ishlinsky Institute for Problems in Mechanics, Rusi

Interaction flow bathymetry at tidal scale in the main sill of the Strait of Gibraltar

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 Tec

Blackspot seabream early life stages dispersal by hydrodynamic modelling (Strait of Gibraltar - Alboran Sea)

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 (SoG) is an important fishing area where artisanal fleets from Spain and Morocco target this species using special longline gears known as “voracera”. Different studies on the health status of this species claim an overexploitation of the resource without any kind of objective management measures implemented yet by the associated countries. Improving the knowledge of the population dynamics, and particularly during the spawning window, is crucial for a better management of the fishing effort for this species. There is an agreement in literature in considering the SoG as an especially energetic and dispersive spawning zone for this species. Once spawned, eggs and larvae (ELS) are assumed to be scattered by the currents towards both sides of the SoG, mostly to the eastwards Alboran basin, where high concentrations of juveniles occur. A high resolution hydrodynamic model coupled to a Lagrangian particle tracking system is employed to assess the potential dispersal pathways of blackspot seabream ELS spawned in the SoG. Recursive releases of passive tracers in different virtual spawning spots and depths within the SoG region are tracked under different tidal conditions in order to obtain an overall characterization of the spatial dispersion patterns of the studied species. Semidiurnal tidal currents emerge as the primary factor in determining the horizontal dispersion and pathway of the spawning products, although the spring-neap tidal cycle and the spawning depth can be also important variables depending on the region considered as well as the arrival zone for the ELS dispersal paths over the Alboran SeaUniversidad de Málaga. Campus de Excelencia Internacional CEIMA

How biomass diel migration affects the reliability of currents measurements in the Strait of Gibraltar?

Since 2004, high resolution profiles of the 3D velocity of the water column have been collected at the westernmost sill of the Strait of Gibraltar (Espartel Sill), with the aim of monitoring the Mediterranean water outflow and evaluate its short and long term variability. A 75 kHz up-looking Acoustic Doppler Profiler (ADP) and, more recently, another 500 kHz model installed in down-looking mode, have been embedded in a subsurface buoy, deployed ∼20m above the seafloor at a depth of approximately 360m. The averaged profile of the observed along-strait current uses to show local minima ∼50m above seafloor, which has been interpreted as the diurnal-semidiurnal interaction of tidal currents (Sammartino et al., 2015). The prevailing semidiurnal tide drives periodic accelerations of the westward Mediterranean current flowing at the bottom, whereas diurnal constituents slow them down, giving rise to a local minimum in amplitude, and prompting severe drops in measurements accuracy. In year 2019, the main ADP was replaced by a 100 kHz model sporting an additional vertical beam that collects high resolution echograms of the water column. This new information reveals the key role of scatterers concentration, which undergoes diel migrations, and affects the reliability of the velocity observations which rely on the amplitude of scattered echo recorded by the instruments. Actually, echo amplitude reaches average correlations of 0.7 with measurement uncertainties. In light of these new insights, an accurate update of the Mediterranean outflow calculations is performed and new values of trend and long-term variability, are estimated.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Efectos de la dinámica mareal en los patrones de conectividad del voraz (Pagellus bogaraveo) en el Mar de Alborán

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

Hydrochanges Gibraltar Campaign - characterization of Mediterranean Outflow through the Strait of Gibraltar

The precise characterization of the Mediterranean outflow through the Strait of Gibraltar is a very well know issue although a question rather far to be resolved completely. Many scientific efforts have been invested to try to define the exact composition and evolution of the Mediterranean waters (MWs) raising at the entrance of the strait and crossing one of the most dynamically active site of the worldwide oceans. In the framework of the Hydrochanges European programme, the “Gibraltar International Campaign” was carried out onboard the R/V Tethys II by the French Mediterranean Institute of Oceanography (MIO) in June 2012, with the chance to perform a series of highresolution CTD meridional transects. The instrument used is a Moving Vessel Profiler (MVP), a towed free-falling CTD, which enables a very high spatial resolution semi-autonomous monitoring of the column water. This work presents the hydrological data set retrieved in the campaign and proposes their usage as tool for the characterization of the composition and the evolution of the Mediterranean outflow along the strait. Two main assumptions are discussed: the generally accepted hypothesis of only two main Mediterranean waters crossing the strait, the Levantine IntermediateWater (LIW) and theWestern Mediterranean DeepWater (WMDW), and the novel theory, principally supported by the MIO group since last years, of the presence of up to four Mediterranean waters raising at the strait entrance: two intermediate waters, the LIW and the Winter Intermediate Water (WIW) and a further dense water, the Tyrrhenian Deep Water (TDW) flanking the WMDW. In both cases the mixing within these MWs and between them and the Atlantic inflowing waters, namely the Surface Atlantic Water (SAW) and the North Atlantic Central Water (NACW), are analyzed and discussed. A classical mixing triangle approach is proposed for the first assumption, with the definition of a third vertex as a general Atlantic water, and a novel approach based on a simplified cluster analysis of the Temperature/Salinity/Density diagrams of the transects, is applied to the six water masses considered in the second assumption. The latter is also applied to the GIBEX2 (Gibraltar Experiment) dataset in order to confirm, by a completely subjective approach, the rather arbitrary definition of the MWs accepted so far. A clear differentiation of the MWs along the cross-strait direction is observed, with intermediate waters laying on the northern Spanish slope and the denser ones flowing along the southern slope. However, this structure is deeply modified by the very strong mixing occurring in the strait and it ends to nearly disappear at west of the Camarinal Sill. The temporal variability, strictly related to the tidal dynamics, is very high, inducing strong changes in this structure throughout the strait, up to substantially modify it. In order to investigate this temporal variability, the recent series of current and thermohaline characteristics of the MWs, sampled simultaneously at Espartel and in two (north and south) extremes of the Camarinal Sill by the Physical Oceanography Group of the University of Málaga, have also been examined with interesting results on the characterization of the outflow evolution along the strait.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Cytoreduction and HIPEC in the treatment of "unconventional" secondary peritoneal carcinomatosis

BACKGROUND: Peritoneal metastasis (PM) is considered a terminal and incurable disease. In the last 30 years, cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) radically changed the therapeutic approach for these patients and is regarded as the standard of care for pseudomyxoma peritonei from appendiceal cancer and peritoneal mesotheliomas. Improved survival has also been reported in treating PM from ovarian, gastric, and colorectal cancers. However, PM often seriously complicates the clinical course of patients with other primary digestive and non-digestive cancers. There is increasing literature evidence that helped to identify not only the primary tumors for which CRS and HIPEC showed a survival advantage but also the patients who may benefit form this treatment modality for the potential lethal complications. Our goal is to report our experience with cytoreduction and HIPEC in patients with PM from rare or unusual primary tumors, discussing possible "unconventional" indications, outcome, and the peculiar issues related to each tumor. METHODS: From a series of 253 consecutive patients with a diagnosis of peritoneal carcinomatosis and treated by CRS and HIPEC, we selected only those with secondary peritoneal carcinomatosis from rare or unusual primary tumors, excluding pseudomyxoma peritonei, peritoneal mesotheliomas, ovarian, gastric, and colorectal cancers. Complications and adverse effects were graded from 0 to 5 according to the WHO Common Toxicity Criteria for Adverse Events (CTCAE). Survival was expressed as mean and median. RESULTS: We admitted and treated by CRS and HIPEC 28 patients with secondary peritoneal carcinomatosis from rare or unusual primary tumors. Morbidity and mortality rates were in line with those reported for similar procedures. Median survival for the study group was 56 months, and 5-year overall survival reached 40.3 %, with a difference between patients with no (CC0) and minimal (CC1) residual disease (52.3 vs. 25.7), not reaching statistical significance. Ten patients are alive disease-free, and eight are alive with disease. CONCLUSIONS: Cytoreduction and HIPEC should not be excluded "a priori" for the treatment of peritoneal metastases from unconventional primary tumors. This combined therapeutic approach, performed in an experienced center, is safe and can provide a survival benefit over conventional palliative treatments

Water renewal mechanisms of the Bay of Algeciras in the Strait of Gibraltar

The Bay of Algeciras (BA) is a marine environment subject to high levels of anthropogenic pressure. Here we analyze observations collected at the Bay and the results of an ocean circulation model to investigate its circulation and variability. Special attention is paid to the identification of the mechanisms enhancing the exchange of water with the adjacent Strait of Gibraltar and therefore contributing to maintain satisfactory levels of water quality.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech