Strait Of Gibraltar Research Articles

Direct in situ evidence of tidal roles in the formation of contourite depositional systems

Tidal currents are ubiquitous in the oceans, but the role of these currents in contributing to form contourite depositional systems is poorly understood. Here we evaluated the significance of these currents in the formation and shaping of the contourite depositional systems. We examined in situ current data, spanning three months to one year, from four contourite sites at the exit of the Strait of Gibraltar, the northern North Atlantic Ocean, the Pacific margin of the Antarctic Peninsula, and the Lake Champlain. These current data indicate that tidal currents contribute to varying degrees to the formation of contourite erosional and depositional features, depending on the relative strengths of local tidal currents and background water mass circulation. Tidal currents enhance sediment resuspension in moats and channels, and encourage deposition on drifts, thereby promoting the development of contourite depositional systems. Baroclinic (internal) tidal currents are likely the dominant agent. Our findings indicate that tidal influences, especially those of internal tides, need to be considered in studies of the generation and evolution of contourite depositional systems.

A Brief Look at the Geopolitical Situation of Islamic Countries: Emphasis on the Role of Natural Resources

The Islamic world is formed from a very large territory that constitutes the most important strategic and lucrative regions and points of the world, starting from the Mediterranean Sea and encompassing most of the geography of African countries, to western, southwestern, central Asia, south and southeast Asia. The political unity of the Islamic world has been weakened after the eleventh century CE and political power has been dismantled by Muslims and with the disintegration of the Osmani Turkic Empire, the political and geopolitical power of the Islamic world has been degraded. Although the most important and valuable natural resources including oil and gas are located in the territory of Islamic countries, the most important strategic areas such as the Persian Gulf, the Suez Canal, the Straits of Dardaniel, Basforce and Bab al-Mandab, the Oman Sea, the Red Sea, the Strait of Gibraltar are located in the territory of Islamic countries, if the Islamic world has political unity, it will use its natural and situational resources properly. The greatest power will become globally, but the geopolitical situation of Islamic countries is still fragile, there is economic multiplicity between Islamic countries and Western countries are directly and indirectly sovereign over the greater number of these countries and benefit from their resources, The aim of this study was to briefly investigate the geopolitical situation of Islamic countries with emphasis on its natural resources. The research method of this subject is library and internet which is the result of research information and awareness about the geopolitical situation of Islamic countries with emphasis on the role of natural resources.

Spatial Distribution and Temporal Variation of Megafauna in Circalittoral and Bathyal Soft Bottoms of the Westernmost Biodiversity Hotspot of the Mediterranean Sea: The Alboran Ridge

The Alboran Sea is the westernmost sub-basin of the Mediterranean Sea, and it is connected to the Atlantic Ocean through the Strait of Gibraltar. The Alboran Ridge is located in the middle of the Alboran Sea and represents a hotspot of biodiversity in the Mediterranean Sea. Besides their critical importance, there are few studies on the communities and changes in biodiversity, and they mostly concentrate on infralittoral and circalittoral bottoms. In this work, the composition, structure and bathymetric and temporal changes of megafauna of the Alboran Ridge were examined. Samples were collected from MEDITS surveys carried out between 2012 and 2022 at depths ranging from 100 to 800 m. Analyses were performed separately for each of the taxonomic groups: osteichthyes, chondrichthyes, crustaceans, molluscs, echinoderms and “other groups”. There was no common spatial organization for each of the faunistic groups studied, although most of them displayed differences between the shelf and the slope. The continental shelf was characterized by the highest values of community metrics such as abundance, biomass, species richness and mean weight of species for all groups except for chondrichthyes and crustaceans. Decreasing trends of some community metrics were detected in some of the faunistic groups throughout the study period.

Metagenomic Analysis of Microbial Diversity in the Moroccan Coastal Water of the Gibraltar Strait

Coastal waters are known for higher productivity and organic matter levels, which support a high diversity and abundance of microorganisms compared to some aquatic environments. The characterization of marine microbiomes can provide valuable information for evaluating the sustainability of coastal waters that are increasingly subjected to environmental and human impacts. Our study is the first metagenomic study realized on Moroccan Mediterranean coastal seawater. We analyzed and described the Gibraltar Detroit marine microbiome taxonomic and functional profiling using MG-RAST software. Shotgun sequencing revealed a predominance of bacterial taxa, particularly the Proteobacteria (57.29%) and Bacteroidetes (27.06%) phyla, alongside notable populations of eukaryotes, viruses, and archaea. Alphaproteobacteria and Gammaproteobacteria emerged as the dominant bacterial classes, while Flavobacteria represented a significant portion of Bacteroidetes. Functional profiling of the microbial community highlighted a wide array of metabolic pathways, emphasizing genes related to carbohydrate metabolism, amino acid synthesis, and protein processing. The marine microbiome exhibited essential biogeochemical activities, particularly in nitrogen, sulfur, and carbon cycles, with notable pathways including denitrification, thiosulfate oxidation, and carbon fixation. This functional diversity underlines the microbiome’s role in sustaining ecosystem health through nutrient cycling and organic matter degradation. Our findings offer a crucial baseline for understanding microbial community structure and resilience in Mediterranean coastal ecosystems, with implications for assessing future environmental and anthropogenic impacts on these microbial dynamics.

Environmental changes and historical occupation at Oued Laksar (Ksar Seghir), Morocco

Laksar is a small river near the village of Ksar Seghir, located between Tangier and Ceuta (Morocco), strategic points to control the Strait of Gibraltar over centuries. The river outlets at the western part of a sandy beach that can block the fluvial discharge in years of low precipitation/river flow.The area is densely occupied since the 5th century BC, during the roman period and Early Middle Age in the archaeological site of Dhar d’Aseqfane, located around 1 km from the mouth of the river. The coastal town of Ksar Seghir was founded on the eastern margin and was used as a shipyard for Moroccan dynasties after the 12th century. During the 15th and 16th centuries, Portugal occupied Ksar Seghir to control the Strait and to increase its power in North Africa. After the Portuguese left the site remained abandoned. The present-day Moroccan village developed in the 20th century, first expanding on the western river slope and gradually encompassing the archaeological site.This work aims to i) characterize the environmental evolution of the Laksar River; ii) identify potential records of extreme events such as floods or tsunamis; and iii) explore the relationship between the landscape dynamics and human occupation.To achieve these goals, a ∼5.4 m long sediment core - KS1 - was studied applying high-resolution multiproxy analyses (X-Ray, magnetic susceptibility, sedimentology, organic chemistry and micropalaeontology) together with 14C dating to establish a chronological model.The sedimentary sequence corresponds to intercalations of fine sand and mud. Results point to deposition in subtidal conditions between the core base (ca. 2500 cal BP) and the 15th century AD (388 cm below surface). The dominance of marine foraminifera assemblages with high number of juveniles and high diversity index suggests an environment under open marine conditions during this period. Conversely, the low δ13C values, coupled with the presence of charophytes and Cretaceous, Paleogene and Neogene reworked calcareous nannofossils reflect the contribution of fluvial processes. The sedimentary record underscores fluctuations in fluvial discharge, beach morphology and marine influence. The accumulation of magnetic (heavy) minerals at the core base is the likely result of at least one high-energy event.Following the onset of Portuguese occupation of Ksar Seghir (15th century), the sedimentation rate increases, silting-up the channel margins. Deposition occurs under low subtidal to intertidal conditions. Foraminifera assemblages point to a low salinity environment; coarse materials are mostly constituted by minerogenic particles transported by the fluvial network. Changes in the sedimentary succession (heavy-minerals accumulation, higher marine influence and rip-up clasts) were detected between 219 cm and 140 cm depth below surface that, according to the age-model, overlap temporally with the Lisbon 1755 AD tsunami event (Great Lisbon earthquake).

Shifts in Maritime Trade Routes as a Result of Red Sea Shipping Crisis Detected in TROPOMI NO2 Data

AbstractObservations from space‐borne spectrometers have been lately used to quantify shipping emissions of nitrogen oxides (ΝΟΧ). Here we present a method that enhances the shipping signal of NO2 TROPOspheric MOnitoring Instrument (TROPOMI) satellite sensor observations in order to assess the impact of the Red Sea ship attacks on NO2 levels in three important shipping routes along the Red Sea, the Cape of Good Hope, and the Gibraltar Strait. Major shipping carriers, sailing usually via the Red Sea, have responded to the attacks by transiting their fleet around the African continent. The shipping signal from TROPOMI declines by ∼55% in the Red Sea and ∼15% in the Gibraltar Strait while an increase of ∼40% is found off the South African coast between January–June 2024 and the same period in 2023. These changes correlate well with vessel statistics, demonstrating the ability to track abrupt changes in NO2 shipping levels with satellite measurements.

Evolution of linear internal waves over large bottom topography in three-layer stratified fluids

Evolutions of internal waves of different modes, particularly mode 1 and mode 2, passing over variable bathymetry are investigated based on a new numerical scheme. The problem is idealized as interfacial waves propagating on two interfaces of a three-layer density stratified fluid system with large-amplitude bottom topography. The Dirichlet-to-Neumann operators are introduced to reduce the spatial dimension by one and to adapt the three-layer system and significant topographic effects. However, for simplicity, nonlinear interactions between interfaces are neglected. Numerical techniques such as the Galerkin approximation, proven effective in previous works, are applied to save computational costs. Shoaling of linear waves on an uneven bottom is first studied to validate the proposed formulation and the corresponding numerical scheme. Then, for two-dimensional numerical experiments, mode transition phenomena excited by locally confined bottom obstacles and quickly varying topographies, including the Bragg resonance, mode-2 excitation, wave homogenization, etc., are investigated. In three-dimensional simulations, internal wave refraction by a Luneberg lens is considered, and good agreement is found in comparison with the ray theory. Finally, in the limiting case, when the top layer can be negligible (for example, a gas layer of extremely small density), the problem is reduced to a two-and-a-half-layer fluid system, where an interface and a surface are unknown free boundaries. In this situation, the surface signature of an internal wave is simulated and verified by introducing the realistic bathymetry of the Strait of Gibraltar and qualitatively compared with the satellite image.

Marine Microplastic Classification by Hyperspectral Imaging: Case Studies from the Mediterranean Sea, the Strait of Gibraltar, the Western Atlantic Ocean and the Bay of Biscay

Marine Microplastic Classification by Hyperspectral Imaging: Case Studies from the Mediterranean Sea, the Strait of Gibraltar, the Western Atlantic Ocean and the Bay of Biscay

Understanding the invasion of the macroalga Rugulopteryx okamurae (Ochrophyta) in the northern Alboran Sea through the use of biogeographic models

Rugulopteryx okamurae is a brown alga native to the northwestern Pacific and invasive elsewhere. It was first sighted in the southern Strait of Gibraltar in 2015, expanded to the northern Strait of Gibraltar in 2016, and had covered most of the northern Alboran Sea by 2021. Understanding the factors that may explain its different phases of colonisation is crucial for developing mitigation and control measures. We modelled the yearly distribution of R. okamurae in the northern Alboran Sea from 2016 to 2021 using the favourability function, which produces commensurable biogeographic models despite variations in species prevalence across years. This function also allows the use of fuzzy logic operations to combine previous environmental models based on different explanatory factors, namely biotope, biocoenosis, coastal influence, accessibility through dispersion, and oceanographic characteristics. Significant environmental models were assembled, and their fuzzy intersection and union applied. This resulted in two final biogeographic models for each year, which were used to predict the distribution of the species in following years. The biogeographic models exhibited a high predictive capacity, as most years accurately predicted colonisation in the following year or even multiple years ahead. Accessibility through dispersion and oceanographic characteristics were critical during the initial years of establishment, while complete establishment depended on all five factors together. Expansion to the whole northern Alboran coast was explained by favourable conditions for any of the explanatory factors, while all factors except coastal influence explained the saturation of the invasion. We conclude that the biogeographic models prove valuable in understanding the factors that contributed to the spread of R. okamurae in the northern Alboran Sea. This approach could help prevent further colonisation and mitigate the ecosystem and commercial consequences of R. okamurae's invasion.

Population Genomics of the Blue Shark, Prionace glauca, Reveals Different Populations in the Mediterranean Sea and the Northeast Atlantic.

Populations of marine top predators have been sharply declining during the past decades, and one-third of chondrichthyans are currently threatened with extinction. Sustainable management measures and conservation plans of large pelagic sharks require knowledge on population genetic differentiation and demographic connectivity. Here, we present the case of the Mediterranean blue shark (Prionace glauca, L. 1758), commonly found as bycatch in longline fisheries and classified by the IUCN as critically endangered. The management of this species suffers from a scarcity of data about population structure and connectivity within the Mediterranean Sea and between this basin and the adjacent Northeast Atlantic. Here, we assessed the genetic diversity and spatial structure of blue shark from different areas of the Mediterranean Sea and the Northeast Atlantic through genome scan analyses. Pairwise genetic differentiation estimates (F ST) on 203 specimens genotyped at 14,713 ddRAD-derived SNPs revealed subtle, yet significant, genetic differences within the Mediterranean sampling locations, and between the Mediterranean Sea and the Northeast Atlantic Ocean. Genetic differentiation suggests some degree of demographic independence between the Western and Eastern Mediterranean blue shark populations. Furthermore, results show limited genetic connectivity between the Mediterranean and the Atlantic basins, supporting the hypothesis of two distinct populations of blue shark separated by the Strait of Gibraltar. Although reproductive interactions may be limited, the faint genetic signal of differentiation suggests a recent common history between these units. Therefore, Mediterranean blue sharks may function akin to a metapopulation relying upon local demographic processes and connectivity dynamics, whereby the limited contemporary gene flow replenishment from the Atlantic may interplay with currently poorly regulated commercial catches and large-scale ecosystem changes. Altogether, these results emphasise the need for revising management delineations applied to these critically endangered sharks.

Illuminating the richness of the ascidian fossil record: a new exceptionally diverse assemblage of ascidian spicules from the Middle Miocene of Bosnia and Herzegovina

AbstractAscidians, or sea squirts, are sac‐like sessile tunicates commonly found in modern seas. Although the oldest ascidians, or at least ascidian‐like tunicates, are mid‐Cambrian in age, the quality of the ascidian fossil record is extraordinarily poor. It mostly consists of isolated finds or low‐diversity assemblages, often represented by mineral spicules. Our study reports the world's most diverse assemblage of ascidian spicules, originating from the Middle Miocene Bogutovo Selo near Ugljevik, Bosnia and Herzegovina. This material includes 31 spicule types, with four assignable to species (Lissoclinum cf. perforatum, Polysyncraton cf. bilobatum, Didemnum cf. vexillum and D. cf. leopardi) and 10 to genera, all belonging to aplousobranchiate ascidians. Comparing our findings with those of two other studies that use modern biological nomenclature, our assemblage shows a closer resemblance to the distant Eocene Australian assemblage than to the Miocene ascidians from Eastern Paratethys. This suggests the persistence of a once‐homogeneous and widely distributed Eocene fauna into the Miocene, while the Eastern Paratethyan basin developed an endemic fauna after the isolation of Eastern Paratethys from the open sea. Some taxa of our assemblage currently inhabit the Mediterranean Sea. The discovery of one species in distant South African waters suggests that tectonic and environmental changes during the Late Miocene, including the closure of the Gibraltar Strait and prior disconnection from the Indian Ocean, may have limited its survival to remote refugia. The study underscores the importance of including spicules in reconstructing ascidian faunas in the geological past, an area that has been surprisingly understudied.

Modelling Mediterranean ocean biogeochemistry of the Last Glacial Maximum

Abstract. We present results of simulations performed with a physical–biogeochemical ocean model of the Mediterranean Sea for the Last Glacial Maximum (LGM) and analyse the differences in physical and biochemical states between the historical period and the LGM. Long-term simulations with an Earth system model based on ice sheet reconstructions provide the necessary atmospheric forcing data, oceanic boundary conditions at the entrance to the Mediterranean Sea, and river discharge to the entire basin. Our regional model accounts for changes in bathymetry due to ice sheet volume changes, reduction in atmospheric CO2 concentration, and an adjusted aeolian dust and iron deposition. The physical ocean state of the Mediterranean during the LGM shows a reduced baroclinic water exchange at the Strait of Gibraltar, a more sluggish zonal overturning circulation, and the relocation of intermediate and deep-water-formation areas – all in line with estimates from palaeo-sediment records or previous modelling efforts. Most striking features of the biogeochemical realm are a reduction in the net primary production, an accumulation of nutrients below the euphotic zone, and an increase in the organic matter deposition at the seafloor. This seeming contradiction of increased organic matter deposition and decreased net primary production challenges our view of possible changes in surface biological processes during the LGM. We attribute the origin of a reduced net primary production to the interplay of increased stability of the upper water column, changed zonal water transport at intermediate depths, and lower water temperatures, which slow down all biological processes during the LGM. Cold water temperatures also affect the remineralisation rates of organic material, which explains the simulated increase in the organic matter deposition, which is in good agreement with sediment proxy records. In addition, we discuss changes in an artificial tracer which captures the surface ocean temperature signal during organic matter production. A shifted seasonality of the biological production in the LGM leads to a difference in the recording of the climate signal by this artificial tracer of up to 1 K. This could be of relevance for the interpretation of proxy records like, e.g., alkenones. Our study not only provides the first consistent insights into the biogeochemistry of the glacial Mediterranean Sea but will also serve as the starting point for transient simulations of the last deglaciation.

The Desiccation and Catastrophic Refilling of the Mediterranean: 50 Years of Facts, Hypotheses, and Myths Around the Messinian Salinity Crisis.

According to some authors, the Messinian salinity crisis was ended by a giant waterfall or megaflood 5.33 million years ago, when the Atlantic Ocean reconnected in a catastrophic way with the desiccated Mediterranean, creating the Strait of Gibraltar. An erosional surface deeply cutting upper Miocene or older rocks and sealed by lower Pliocene sediments is the geological feature that inspired this fascinating hypothesis. The hypothesis, which recalls several ancient myths, is well established in the scientific community and often considered to be a fact. However, several studies are suggesting that the Atlantic-Mediterranean connection through the Strait of Gibraltar was probably active before and during the entire Messinian salinity crisis. This allows us to consider the possibility that long-lived, more gradual physical processes were responsible for the evolution of the strait, opening the idea of a nondesiccated Mediterranean Sea.

Health-Related Quality of Life Among Irregular Sub-Saharan Migrants in Northern Morocco.

Due to its geographical proximity to Europe, Morocco experiences a significant influx of migrants from neighboring Sub-Saharan African countries. Attempts to cross the Strait of Gibraltar make Northern Morocco a stopover for Sub-Saharan migrants. However, faced with increasingly restrictive measures from European Union countries, many of these migrants are compelled to turn this transit into a prolonged stay in Morocco, often in irregular status and facing challenging socio-economic conditions that threaten their health and their quality of life-related to health. This study aims to assess the level of health-related quality of life and its determinants among irregular Sub-Saharan migrants in Northern Morocco using the 36-Item Short Form Survey (SF-36) measurement scale. A total of 526 irregular Sub-Saharan migrants residing in the cities of Tangier and Tetouan were recruited using snowball sampling. A socio-demographic information sheet and the SF-36 scale were used to collect data. Subsequently, the data were entered and statistically analyzed using Statistical Product and Service Solutions (SPSS, version 21.0; IBM SPSS Statistics for Windows, Armonk, NY). Numerical variables were summarized as mean ± standard deviation and categorical variables as frequency and percentage. Non-parametric tests, including the Mann-Whitney U test and Kendall's Tau-B, were used to measure the association of physical and mental component scores with sociodemographic variables, for a significance level set at p < 0.05. Multivariate logistic regression was conducted to identify factors determining health-related quality of life, using odds ratios (OR) and a 95% confidence interval (CI) for p < 0.05. Participants were aged between 18 and 50 years, with a mean age of 29.7 ± 7.6 years; 80% were single, and the majority were male (63.7%). In terms of education, 57.2% have a secondary level. The physical (PCS = 46.5 ± 9.03) and mental (MCS = 35.5 ± 9.9) summary scores were low. PCS and MCS were lower among subjects aged ≥ 36 years compared to those aged 18-25 years (p = 0.000). Women had lower PCS than men (p = 0.002). The migrants having more than three years in Morocco had lower MCS compared to those recently settled (p = 0.002). PCS and MCS were lower among participants who were assaulted compared to those who were not (p = 0.000). Multivariate logistic regression results showed that age, type of habitat, and assault significantly affected both PCS and MCS scores. Gender is a significant determinant for PCS and duration of stay in Morocco for MCS. The quality of life of Sub-Saharan irregular migrants appears to be low, particularly concerning the mental health component, highlighting the need for priority interventions in this area to improve their health status.

High contribution of an invasive macroalgae species to beach wrack CO2 emissions

Accumulations of macroalgal wrack are important for adequate functioning of the beach ecosystem. However, the sudden beaching of seaweed masses smothers the coastline and forms decomposing piles on the shore, harming tourism-based economies, but also affecting the beach ecosystem metabolism. The decomposition of sudden pulses of wrack can modify the biogeochemistry of beach sands and increase greenhouse gas (GHG) emissions. The presence of invasive species in the wrack deposits can superimpose harmful effects on the beach functioning. We quantified the wrack biomass of Rugulopteryx okamurae, an invasive species of extreme impact, on five sandy beaches from the Atlantic coast of the Strait of Gibraltar (Spain), and we tested the effects on in situ respiratory CO2 fluxes using an infrared gas analyser. All the beaches showed massive accumulations of Rugulopteryx wrack deposits. However, the biomass changed significantly between beaches, ranging (mean ± SE) from 968.3 ± 287.7 kg m−1 to 9210 ± 1279.4 kg m−1 of wet weight. Wrack supported high respiration rates, with CO2 fluxes averaging (±SE) 19.15 ± 5.5 μmol CO2 m−2 s−1 across beaches, reaching astounding maximum peaks of 291 μmol CO2 m−2 s−1. The within-beach variability was related to the distance of the wrack deposits from the shoreline, as the average metabolic rates tended to increase significantly from the swash to the drift line. Thicker wrack and a more degraded algae stage showed significantly higher CO2 fluxes. We estimated that the annual CO2 flux of R. okamurae in our study area ranged between 0.39 (±0.01) and 23.30 (±11.33) kg C m−2 y−1. We suggest that massive amounts of beach wrack can become a globally significant contributor to GHG emissions that can offset any potential carbon-sink capacity of macroalgal forests. However, the piles of wrack located several meters above the drift line showed non-measurable CO2 efflux. Transferring beach wrack from swash to drier upper-beach areas, a common practice in many coastal regions suffering from massive wrack accumulations, might help reduce GHG emissions while removing the wrack stockpiles from the intertidal. However, this practice is not necessarily suitable for all beaches and can create ecological and conservation problems in the dune system. There is an urgent need to implement practical and sustainable management practices for massive wrack deposits capable of presenting various solutions to achieve a balance between conservation and recreation actions, answering the consequences of a problem that links both, environmental and economic issues.

Dispersal and connectivity modelling simulations for invertebrate larvae passing through the Strait of Gibraltar

Abstract The link between the northeastern Atlantic and Mediterranean Sea created by the Strait of Gibraltar and the adjacent Iberian and Moroccan coasts marks remarkable transition areas between distinct environments that harbour a diverse mixture of species. The area is interesting regarding marine connectivity and the transport of pelagic invertebrate larvae, crucial knowledge to manage over-exploited populations, and minimize the impacts of climate change and anthropogenic activities. Biophysical models were developed, combining oceanic and particle-tracking Lagrangian simulations with in situ zooplankton distribution data. The conditions driving the larval exchange between the sub-basins and the connectivity throughout the region were explored, using crustacean decapod larvae as biological references. The potential exchange between both sub-basins was confirmed, although specific larval traits revealed contrasting scenarios. The simulations showed that slope-dwelling and mesopelagic larvae have advantage when crossing from the Alboran into the Atlantic, in comparison with shelf-dwelling and epipelagic larvae. Transport pathways and retention areas were identified, and passive drifts were shown to increase the dispersal range of the simulations. The spatial origin of the larval release, larval duration, vertical distribution, and the interaction of larvae with the oceanic features are presented as the main factors impacting the effective larval input into the Atlantic or Mediterranean basins.

The Strait and the Sea Unsettling Scores

In this inquiry I build on my previous work on contemporary aesthetics to engage the media practices and bio-acoustic mappings of cetacean scientists, as well as fishers’ video diaries and sound cartographies of interactions with cetaceans. To these, I also juxtapose a contemporary composer, sound engineer, and media artist’s sonographic records of encounters with these decidedly intriguing marine mammals alas too often reduced to the moniker “charismatic”. Concretely, I zoom in on three media practices: the sound compositions of Ariel Guzik, founder of the Nature Expression and Resonance Lab, who designs and engineers instruments to communicate with grey whales, sperm whales, and bottle nose dolphins in the Sea of Cortez; the hydrophone recordings, spectrograms, drone footage, and photo-identifications by a team of cetacean ethologists and communication scientists who run a research vessel and a marine ecology lab in the Tyrrhenian Sea; and the multimedia online platforms of fishers who produce video diaries of potentially fatal interactions with orcas in the Strait of Gibraltar. These carefully selected and juxtaposed audiovisual practices are the graphic, acoustic, and musical fragments that compose the de-territorialized cartography I am calling The Strait and The Sea.

Assessing grazing of Rugulopteryx okamurae (Ochrophyta) by the sea urchin Paracentrotus lividus (Echinodermata): a prospect for the biocontrol of the alien species?

ABSTRACT Rugulopteryx okamurae is an invasive non-indigenous species (NIS) of marine alga present in the benthic communities of the Strait of Gibraltar, where it has colonized most of the coast triggering ecological, economic and social consequences. The purple sea urchin Paracentrotus lividus is a generalist herbivore with potential to provide resistance to this NIS. Two experiments were carried out to determine if (i) P. lividus consumes R. okamurae under laboratory conditions, (ii) to assess its grazing preferences when this NIS is offered together with the native Ulva sp. and (iii) to find biochemical tissue markers related to R. okamurae ingestion. In the first experiment, sea urchins fed with R. okamurae, Ulva sp. or both diets were evaluated in groups for two months. Ingestion, food preference, growth and survival were assessed. In the second one, the same specimens from the R. okamurae and mixed diets were used to analyse their individual preferences, ingestion rates, growth and fatty acid profiles during another two months. Ingestion rates showed that sea urchins accepted the NIS R. okamurae as food under laboratory conditions, increasing its intake after a long exposure period. The electivity values for R. okamurae also increased when P. lividus was exposed to this alga for a long time. Regarding the fatty acids profile of tissues, the results showed that intestinal arachidonic acid (ARA, 20:4n-6) clearly differentiates sea urchins fed with R. okamurae from those fed with the mixed diet. ARA also appeared to be related to the feeding preferences, highlighting this fatty acid as a reliable marker of R. okamurae ingestion. Further research is needed in order to determine P. lividus feeding behaviour and its role as a biocontrol species in the areas invaded by R. okamurae.

Climate change in the Canary/Iberia upwelling region: the role of ocean stratification and wind

The Canary/Iberia region (CIR), part of the Canary Current Upwelling System, is well-known for its coastal productivity and crucial role in enriching the oligotrophic open ocean through the offshore transport of the upwelled coastal waters. Given its significant ecological and socio-economic importance, it is essential to assess the impact of climate change on this area. Therefore, the goal of this study is to analyze the climate change signal over the CIR using a high-resolution regional climate system model driven by the Earth system model MPI-ESM-LR under RCP8.5 scenario. This modelling system presents a regional atmosphere model coupled to a global ocean model with enough horizontal resolution at CIR to examine the role of the upwelling favourable winds and the ocean stratification as key factors in the future changes. CIR exhibits significant latitudinal and seasonal variability in response to climate change under RCP8.5 scenario, where ocean stratification and wind patterns will play both complementary and competitive roles. Ocean stratification will increase from the Strait of Gibraltar to Cape Juby by the end of the century, weakening the coastal upwelling all year long. This increase in stratification is associated with a freshening of the surface layers of the North Atlantic. However, modifications in the wind pattern will play a primary role in upwelling source water depth changes in the southernmost region of the CIR in winter and in the north of the Iberian Peninsula in summer. Wind pattern changes are related to the intensification of the Azores High in winter and to a deepening of the Iberian thermal low in summer months.

Killer whales habitat suitability in the Iberian Peninsula and the Gulf of Biscay: Implications for conservation

This study addresses existing gaps in our understanding of the ecology of killer whales by investigating their habitat use dynamics in the Atlantic coastal waters of North Africa, the Iberian Peninsula, and the Gulf of Biscay. Despite previous research on their distribution during the Atlantic Bluefin tuna migration in the Strait of Gibraltar and adjacent waters, substantial knowledge gaps persist, particularly regarding their movement patterns beyond these regions and seasonal variations in habitat use. Utilizing killer whale occurrence records from 2020 to 2023 and considering environmental factors influencing prey presence, we employed seasonal spatial distribution models. MaxEnt models exhibited robust predictive performance, emphasizing distance to shore, depth, and sea surface temperature as key factors influencing killer whale habitat suitability. Spatial distribution patterns reveal a peak in coastal waters of the southern Iberian Peninsula and North Africa during winter and spring, with a significant shift northward and expansion during summer and autumn towards the Gulf of Biscay. This expansion suggests a broader distribution of killer whales in the Northeast Atlantic during warmer months, encompassing a diverse range of habitats. The research underscores a substantial interaction (47%) between killer whales and recreational vessels, posing concerns for both the killer whales and maritime safety. This study provides valuable insights on killer whale habitat use in the Atlantic waters from North Africa to the Gulf of Biscay, thereby supporting conservation and management efforts in the region.