Tesis Doctorals - Facultat - Ciències de la Terra

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Respuesta bio-geomorfodinámica a las avenidas: avances en la evaluación de la peligrosidad por inundación (río Francolí, Cuenca del Mediterráneo occidental)
(Universitat de Barcelona, 2024-12-17) Valera Prieto, Llanos; Ruiz‐Villanueva, Virginia; Universitat de Barcelona. Facultat de Ciències de la Terra
[spa] La región mediterránea es reconocida a nivel mundial como una zona crítica para los desastres naturales, impulsada por factores geográficos, climáticos, demográficos y socioeconómicos. Los eventos meteorológicos extremos, como lluvias torrenciales, a menudo provocan inundaciones repentinas (flash floods) caracterizadas por su alta intensidad, rapidez e imprevisibilidad, lo que supone riesgos considerables para poblaciones humanas y las infraestructuras. Por otro lado, la rápida urbanización, particularmente en las áreas costeras mediterráneas y las zonas propensas a inundaciones, ha exacerbado la vulnerabilidad a los peligros naturales. Además, los efectos del cambio climático, que resultan en eventos extremos más frecuentes, han amplificado el impacto de las inundaciones repentinas, presentando importantes desafíos para la gestión del riesgo de desastres en la región. La respuesta de los sistemas fluviales mediterráneos a las inundaciones repentinas es un proceso altamente complejo y dinámico, gobernado por interacciones no lineales entre factores biológicos, geomorfológicos e hidrológicos. La magnitud de los cambios morfológicos en los cauces de los ríos está determinada por una combinación de factores, como la intensidad, la duración y la variabilidad espacial de la inundación, y las condiciones previas del lecho del río y la llanura de inundación. La vegetación ribereña desempeña un doble papel, estabilizando los sedimentos en algunas áreas mientras promueve la erosión o altera los patrones de sedimentación en otras. Durante los eventos extremos, grandes cantidades de vegetación erosionada y arrancada pueden incorporarse al flujo, y el transporte y la acumulación de este material pueden obstruir infraestructuras como puentes, intensificando aún más los daños por inundación. Además, las observaciones directas y los datos cuantitativos sobre este fenómeno siguen siendo limitados en las regiones mediterráneas, lo que subraya la necesidad de más investigaciones, especialmente en el contexto de cambio climático y el aumento de las presiones antropogénicas sobre las cuencas fluviales. En la noche del 22 octubre del 2019 una situación de inestabilidad atmosférica regida por una DANA (Depresión Aislada de Niveles Altos), provocó precipitaciones intensas en la provincia de Tarragona, Catalunya, que superaron los 100 mm en 24 horas. Las lluvias de carácter torrencial se concentraron en las montañas de Prades, lo que resultó en una crecida repentina del río Francolí. En el transcurso de una hora, el caudal del río aumentó más de 800 veces su caudal inicial, lo que ilustra la extrema intensidad y el rápido desarrollo del evento de inundación. Las consecuencias fueron muy graves, incluyendo varias muertes, daños generalizados en infraestructuras y cultivos, interrupciones en los servicios básicos y pérdidas económicas que ascendieron a millones de euros. Desde una perspectiva bio-geomorfológica, la inundación indujo cambios significativos. Se movilizaron grandes cantidades de sedimentos y madera de gran tamaño, lo que desencadenó una extensa morfogénesis fluvial y provocó alteraciones drásticas en la morfología del cauce del río. El transporte y la deposición de grandes cantidades de madera jugaron un papel crucial al obstruir puentes, lo que, a su vez, amplificó el potencial destructivo de la inundación alterando la dinámica del flujo. Este evento proporcionó una oportunidad única para investigar la respuesta del río y mejorar la evaluación de la peligrosidad por inundación en ríos mediterráneos. Por lo tanto, el objetivo principal de esta tesis fue analizar la respuesta bio- geomorfológica y sus complejas interacciones a lo largo de un tramo de 31 kilómetros de la cuenca alta del río Francolí. La investigación empleó un enfoque multidisciplinario innovador, integrando diversas metodologías que representan un avance en el estudio de los procesos bio- geomorfológicos durante eventos extremos en ríos mediterráneos. El estudio examinó las variables geomorfológicas mediante cartografía detallada y análisis geoespaciales, permitiendo comprender la trayectoria del río y los efectos de la avenida. La vegetación ribereña se analizó combinando teledetección, cartografía, trabajo de campo y dendrocronología, proporcionando información sobre la sucesión bio-geomorfológica y la intensidad de eventos pasados. El transporte de material leñoso se investigó a través de cartografía y estadísticas geoespaciales, ofreciendo una visión detallada de su dinámica. Además, por primera vez en río mediterráneos, se implementó una modelización hidrodinámica que incluyó transporte de sedimentos y madera. Los resultados revelaron que los impactos bio-geomorfológicos más significativos, incluyendo el ensanchamiento generalizado del cauce, la destrucción total del bosque de ribera y la movilización y transporte de grandes troncos, que se acumularon principalmente en los puentes, estaban controlados por la energía del cauce, el grado de confinamiento y las características del bosque. Sin embargo, estas perturbaciones bio-geomorfológicas no pueden explicarse completamente, solo por las condiciones naturales, lo que resalta la influencia de factores antropogénicos, como la presencia de puentes e infraestructuras. Aun así, la energía de la inundación, en términos de potencia unitaria del cauce, surgió como un predictor clave del cambio geomorfológico, con su gradiente longitudinal sirviendo como un indicador efectivo de las áreas propensas a la pérdida de vegetación durante inundaciones repentinas. El volumen excepcional de grandes troncos movilizados durante el evento alteró significativamente el comportamiento hidráulico, particularmente en los puentes, donde se acumuló la madera, elevando los niveles de inundación e intensificando el impacto general. Esto demostró claramente que la modificación de los ríos y la construcción de infraestructuras pueden exacerbar los daños por inundación cuando no se considera el transporte de madera en el diseño y la gestión de los ríos. El enfoque metodológico integrado en el estudio de la vegetación, reveló patrones espaciales complejos en la distribución y abundancia de la vegetación y su respuesta a eventos extremos, destacando la importancia de la variabilidad espacial y temporal. La comparación de eventos de inundación significativos (1994 y 2019) subraya la complejidad de estos ecosistemas ribereños y ofrece nuevas perspectivas para cuantificar procesos de sucesión bio-geomorfológica en ríos mediterráneos. Un paso crucial para la evaluación de la peligrosidad de inundación es la identificación de infraestructuras críticas propensas acumular madera. El modelo predictivo aplicado a los 23 puentes a lo largo del río Francolí, identificó de manera efectiva la mayoría de los puentes afectados por la obstrucción de madera durante la inundación y ayudó a revelar las principales características morfológicas y estructurales que influyeron en este proceso. Este modelo ofrece una herramienta valiosa para la gestión del riesgo de inundación en los sistemas fluviales mediterráneos. Finalmente, la reconstrucción de la inundación y el diseño de escenarios permitieron simular y reproducir algunos fenómenos complejos que antes sólo se suponían, arrojando luz sobre las dinámicas complejas del flujo, el sedimento y el transporte de madera durante las inundaciones repentinas. La comparación de escenarios simulados permitió un análisis detallado de cómo los patrones de flujo y la morfodinámica difieren entre las inundaciones que involucran agua clara y aquellas que implican transporte de sedimentos y material leñoso. El modelo numérico replicó con éxito el bloqueo y el desbloqueo de puentes a lo largo del tramo de río estudiado, mostrando cómo este proceso agravó los efectos de la inundación. En resumen, esta tesis representa una contribución científica y práctica significativa, ofreciendo un valioso registro histórico para futuros estudios sobre ríos mediterráneos. La integración de variables hidrológicas, hidráulicas, geomorfológicas y de vegetación de ribera, junto con el análisis del transporte de grandes troncos, ha proporcionado nuevas perspectivas sobre la respuesta bio- geomorfológica del río Francolí a eventos extremos de inundación. Estos hallazgos ofrecen importantes implicaciones para la evaluación y gestión del peligro de inundación en los sistemas fluviales mediterráneos, particularmente en el contexto del cambio climático y el aumento de las presiones antropogénicas.
Biogeochemical controls on organic contaminants in the Atlantic and Southern Oceans
(Universitat de Barcelona, 2025-06-10) Trilla i Prieto, Núria; Dachs Martinet, Jordi; Jiménez Luque, Begoña; Universitat de Barcelona. Facultat de Ciències de la Terra
[eng] During the last two centuries, the increase of human population and economic development has led to a rising demand for goods and resources. Such development has also led to the synthesis of millions of new organic chemicals, with hundreds of thousands of these currently used in agriculture and industrial applications, as well as in consumer products. A fraction of this myriad of synthetic chemicals, together with hydrocarbons derived from the use of fossil fuels, reach the environment. This mixture of organic compounds with diverse properties and uses, invisible to the human eye, constitutes a form of pollution to the Earth system of unusual complexity. Addressing chemical pollution is a major challenge due to the large number of chemicals involved, which in addition have different and diverse physico-chemical properties and present different mechanisms of toxicity to organisms, ecosystems and humans. For decades, researchers, environmental agencies and regulatory bodies have sought to prioritize those organic contaminants that need to be regulated because of their potential for long-range transport, ubiquitous occurrence, persistence, bioaccumulation potential, toxicity, and ecological impact. However, the massive production and release of these substances into the environment surpass research and regulatory capacities, endangering the sustainability of the Earth’s system. This mismatch has led to the definition of “novel entities” as one of the planetary boundaries in the current context of global change, essential for the planet’s resilience. A recent study confirms that this threshold, along with five others, has already been exceeded, increasing the risk of irreversible changes to the Earth system. Mostly during the last century, some synthetic chemicals were regulated and banned, even though they are still found in the environment. However, just in the recent decades, an increasing number of chemicals, potentially thousands of contaminants of emerging concern (CECs), have dispersed globally, accumulating in various environmental compartments, with transport, biogeochemical cycles and sinks strongly dependent on their physicochemical properties and chemical structure. They are found in soils, fresh and sea water, ice, air, and biota, from microorganisms to large predators. Many CECs originate from common consumer products such as clothing, cosmetics, furniture, and paints. Among CECs, organophosphate esters (OPEs) and perfluoroalkyl acids (PFAAs) have raised increasing concern due to their ubiquity, persistence, toxicity and bioaccumulation in food webs. Nevertheless, knowledge not only on their occurrence, but their transport, cycling and sinks in the oceans is limited. The study of persistent organic pollutants (POPs) and CECs in the ocean is important, especially in remote regions, as these are sentinels of global pollution, which can only occur for chemicals persistent enough to undergo long-range transport. For instance, candidates for regulation as POPs under the Stockholm Convention should meet the criteria on persistence, toxicity, long-range transport, and biomagnification. This thesis contributes to the study of oceanic and Antarctic pollution with the overall objective of assessing the occurrence, biogeochemistry and sinks of three families of organic pollutants in the ocean: PFAAs, OPEs and semivolatile aromatic compounds (SALCs) within the dissolved black carbon (DBC). Despite their differences in sources and physicochemical properties, these three families share the ability for long-range transport, persistence , and toxic effects on ecosystems and human health.
Global change effects on the habitat availability and distribution of marine species
(Universitat de Barcelona, 2025-04-09) Ouled-Chheikh Bonan, Jazel; Cardona Pascual, Luis; Coll Montón, Marta; Universitat de Barcelona. Facultat de Ciències de la Terra
[eng] Marine ecosystems are increasingly shaped by the combined effects of climate change and human activities, driving shifts in species distributions, ecosystem structure, and habitat suitability. Understanding how these pressures interact at regional scales is essential, as region-specific environmental conditions and ecological strategies can modulate species’ responses to global change. This Ph.D. thesis ex- plores how different dimensions of global change influence the habitat availability and distribution of marine vertebrates, focusing on pelagic fish, pinnipeds, and marine turtles, through three case studies set in the Mediterranean Sea, the Antarctic Peninsula, and the Canary Current Upwelling System. Using diverse modeling approaches, it examines how traits such as foraging behavior and physiological limitations shape species’ capacity to cope with environmental variability and long-term changes driven by global change. In one case study, the spatial overlap between suitable habitats and fishing effort is also assessed, providing insights into areas where human pressures and climate-related impacts may accumulate. Overall, the findings demonstrate the importance of integrating ecological, oceanographic, and human factors into marine management and contribute to a broader understanding of global change impacts on marine vertebrates.
Rhodolith beds in the Menorca Channel. Taxonomic diversity, structural complexity, and monitoring strategies for conservation
(Universitat de Barcelona, 2025-06-27) Cabrito Rubau, Andrea; Maynou i Hernàndez, Francesc; Juan Mohan, Silvia de; Universitat de Barcelona. Facultat de Ciències de la Terra
[eng] Rhodolith beds, formed by free-living calcareous red algae, represent ecologically valuable and structurally complex habitats that contribute significantly to benthic biodiversity and ecosystem functioning. Their intricate three-dimensional architecture provides refugia for other organisms, positioning them among the most important biogenic habitats in the marine realm. However, in the Mediterranean Sea, these habitats remain insufficiently characterized, both in terms of their structural complexity and species composition, which hampers the development of effective conservation and management strategies. This thesis investigates the ecological, taxonomic, and functional dimensions of rhodolith beds in the Menorca Channel (western Mediterranean), integrating morphological, molecular, and ecological approaches across four complementary studies. First, I assessed rhodolith morphological diversity using three-dimensional analyses and comparing core zones of the bed (high rhodolith density) to adjacent areas with lower density. The results revealed that rhodoliths in core areas exhibited more complex morphologies, larger size, and higher interstitial space—key indicators of habitat complexity that are often underestimated by traditional two- dimensional methods. Second, I addressed the knowledge gap in species composition by combining classical taxonomy with molecular techniques, revealing a cryptic diversity of at least 15 rhodolith- forming species. These findings contrast with current Habitats Directive, which focus on just two species predominant in the Atlantic, and underscore the need to revise conservation policies to reflect the true diversity of rhodoliths in the Mediterranean. Third, I clarified the taxonomic status of the poorly known species Sporolithon mediterraneum, for which I designated a neotype based on a specimen from mesophotic depths of the Tyrrhenian Sea. Morphological and molecular analyses confirmed the distinctiveness of this species from other Sporolithon taxa and established a robust framework for future identifications. Finally, I explored the application of three non-intrusive monitoring tools— environmental DNA, underwater video, and passive bioacoustics—to characterize fish assemblages associated with rhodolith beds. Their combined use revealed high species richness, including endangered and cryptic species, while also capturing variability related to habitat heterogeneity and trawling exposure. Altogether, this thesis highlights the underestimated structural and taxonomic complexity of rhodolith beds in the western Mediterranean and emphasizes the value of integrating multidisciplinary tools to understand and monitor these vulnerable habitats. The results contribute to the refinement of habitat assessments, species inventories, and conservation frameworks, with direct implications for regional marine biodiversity management and the development of non-destructive monitoring strategies.
Metodologies de reconstrucció i modelització 3D d’estructures geològiques: anticlinal de Sant Corneli - Bóixols (Pirineus centrals)
(Universitat de Barcelona, 2011-01-18) Mencos Bellpuig, Joana; Muñoz, J. A.; Universitat de Barcelona. Facultat de Ciències de la Terra
[cat] L’anticlinal de Sant Corneli – Bóixols és una estructura de primer ordre dels Pirineus Centrals que permet estudiar una etapa clau en l’evolució de l’orogen pirinenc: l’inici de l’estructuració alpina sobre conques extensives prèvies relacionades amb l’obertura del Golf de Biscaia. Aquest context geodinàmic ha condicionat la geometria i evolució de l’anticlinal, generant una estructura complexa amb una forta component tridimensional. El Grup de Geodinàmica i Anàlisi de Conques (GGAC) i l’Institut de Recerca GEOMODELS han desenvolupat una metodologia integral per a la reconstrucció 3D de cossos geològics que incorpora la modelització estructural i de reservoris així com els processos que s’hi desenvolupen. En aquest context, aquesta Tesi persegueix dues fites principals: (1) analitzar detalladament l’anticlinal i el paper de les estructures preexistents en la seva evolució, i (2) aplicar i combinar tècniques de reconstrucció tridimensional a partir de dades de superfície i subsòl, integrant-les amb modelització numèrica per comprendre quins factors han intervingut en la seva formació. Una exposició excel·lent en superfície, amb afloraments de gran qualitat permeten caracteritzar en detall la seva geometria superficial i optimitzar metodologies de reconstrucció 3D basades en dades de camp. Paral·lelament, la informació de subsòl disponible ha permès restringir la seva geometria en profunditat i investigar la relació entre estructures superficials i profundes mitjançant modelització numèrica. Aquesta modelització també s’ha utilitzat per contrastar hipòtesis evolutives i analitzar la influència de diversos paràmetres en la gènesi de l’estructura. La metodologia emprada en aquesta Tesi cobreix un segment de les tècniques 3D, especialment pel que fa a la interpolació de dades disperses. Un dels punts forts del mètode és l’ús d’un model geomètric que permet interpolar dades amb restriccions geològiques, minimitzant la incertesa i evitant les simplificacions pròpies de projeccions bidimensionals. L’anticlinal de Sant Corneli – Bóixols s’ha desenvolupat en els marges d’una conca extensiva invertida i transportada sobre un encavalcament de gran extensió i desplaçament. La seva geometria combina trets d’inversió tectònica amb característiques pròpies de la tectònica de cobertora, tant en fases preorogèniques com sinorogèniques. Aquesta complexitat el converteix en un anàleg excel·lent per a estudiar orògens menys coneguts o menys accessibles. A escala local, la reconstrucció estructural i la millora del coneixement sobre la seva evolució tectònica han aportat una comprensió més precisa de l’estructura i el seu impacte en la distribució dels cinturons de fàcies durant les diferents etapes del seu desenvolupament. Aquest treball estableix, a més, les bases per a futurs estudis orientats a la modelització de fàcies o de processos sedimentaris, obrint noves línies d’investigació en la geologia estructural i l’anàlisi de conques.
Geophysical-Petrological Modeling of the Crust and Upper Mantle within the Central Mediterranean and Topographic Implications
(Universitat de Barcelona, 2024-11-15) Zhang, Wentao; Jiménez Munt, Ivone; Torné i Escasany, Montserrat; Universitat de Barcelona. Facultat de Ciències de la Terra
[eng] The Central Mediterranean region is a highly active seismic zone with unique tectonic characteristics, forming part of the Alpine-Mediterranean belt that extends from southern Iberia to the western Aegean Sea. Applying an integrated geophysical-petrological modeling, this thesis investigates the thermochemical structure of the lithosphere and sublithospheric mantle beneath the Adria microplate and its margins and explores the geometry and depth continuity of the Adria slabs. Two transects have been modeled down to 400 km, spanning from the Tyrrhenian Basin to the Carpathians-Balkanides region, in a roughly SW-NE direction. In addition, I developed new numerical modeling codes of mantle flow to evaluate the topographic response of opposed subductions along the transects. In the northern transect, results show a more complex structure and slightly higher average crustal density of Adria compared to Tisza microplate. Below the Tyrrhenian Sea and Western Apennines, Moho lays at <25 km depth while along the Eastern Apennines it is as deep as 55 km. The modeled lithosphere-asthenosphere boundary (LAB) below the Tyrrhenian Sea and Pannonian Basin is flat lying at ∼75 and 90 km, respectively. Below the External Apennines and Dinarides the LAB deepens to 150 km, slightly shallowing toward the Adriatic foreland basin at 125 km depth. My results are consistent with the presence of two mantle wedges, resulting from the rollback of the Ligurian-Tethys and Vardar-NeoTethys oceanic slabs followed by continental mantle delamination of the eastern and western distal margins of Adria. These two opposed slabs beneath the Apennines and Dinarides are modeled as two thermal sublithospheric anomalies of −200 °C. In the southern transect, the modeling shows the presence of two asthenospheric mantle wedges aligning with the Apenninic and Dinaric continental mantle slab rollback, along with cold (−200 °C) sublithospheric anomalies beneath Adria's NE and SW margins. In the northern Adria region, the lithosphere undergoes synchronous thinning in the Tyrrhenian domain and thickening toward the forefront of the northern Apennines. This is associated with the northeastward rollback of the SW Adriatic slab, leading to subsequent delamination of the continental mantle. In the southern Adria region, the complex deep structure results from the variably oriented lithospheric slabs, and nearly 90-degree shift of the tectonic grain between the southern Apennines and the Calabrian Arc. At the SW Adria margin, beneath the northern Apennines, the thermal sublithospheric anomaly is attached to the shallower lithosphere, while a slab gap is modeled in the southern Apennines. One possibility is that the gap is due to a recent horizontal slab tear. Along the NE margin of Adria, the thermal anomaly penetrates to depths of about 200 km in the northern Dinarides and 280 km in the southern Dinarides, shallower than the SW Adria anomaly, which extends to at least 400 km depth. Most elevation along the profiles is attributed to thermal isostasy. Elevation in the External Apennines, Dinarides, and Sava Suture Zone can be explained by regional isostasy with an elastic thickness of 20-30 km. The numerical modeling of dynamic topography permitted the identification of the dynamic deflection caused by deep mantle flow and buoyancy forces related to density contrasts. This modeling indicates that the denser attached slabs trigger downwelling mantle flow and negative dynamic topography. A longer slab beneath the northern Apennines leads to higher mantle flow and larger amplitudes of dynamic topography, -400 m. Residual topography in the northern Apennines can be explained by the cold thermal anomaly associated with the northern Apenninic slab. The rest of mantle anomalies produce a negligible dynamic topography, either because of being detached in the case of the southern Apennines, or because of their reduced size below the Dinarides.
Holocene vegetational changes in Northeastern Greenland and its link to North Atlantic Oscillation/Arctic Oscillation
(Universitat de Barcelona, 2024-07-05) Osorio Serrano, Rodrigo; Sáez, Alberto; Giralt Romeu, Santiago; Universitat de Barcelona. Facultat de Ciències de la Terra
[eng] Rapid climate change and its pronounced effect over the Arctic has become a hot topic for both the scientific community and the public, raising concerns about the future of its ecosystems. In this context, Greenland, with its minimal human influence serves as a natural archive of past climate. This island's climate is strongly influenced by large- scale atmospheric and oceanic interactions, particularly the North Atlantic Oscillation/Arctic Oscillation (NAO/AO) and the Atlantic Meridional Overturning Current (AMOC). These patterns influence temperature and precipitation, with NAO+ phases bringing colder and drier conditions and NAO- phases bringing warmer and moister conditions. AMOC, a key component of global heat distribution, also plays a role by influencing sea-ice cover along Greenland's eastern coast. This study was conducted on the Zackenberg valley and its surroundings, in NE Greenland (74°N, 20°W). The main aim of this study is to quantitatively reconstruct the climate evolution of NE Greenland based on modern pollen-climate relationships. Our specific goals are to: (1) establish a reference collection of modern pollen from the Zackenberg area, (2) identify the key environmental and ecological factors influencing pollen assemblages in the sediment record, (3) reconstruct past vegetation changes throughout the Holocene epoch in Zackenberg, and (4) establish linkages between these reconstructed vegetation changes and past climate variations, including those associated with the NAO/AO. To achieve these objectives, a quantitative approach based on modern pollen-climate relationships was executed.
The biogeochemical imprint of the Azores Archipelago lacustrine sedimentary infill. A linkage between the climatic effects of the north Atlantic atmospheric circulation and the tectono-volcanic landscape of the triple junction during the late Holocene
(Universitat de Barcelona, 2024-07-30) Benavente Marín, Mario; Giralt Romeu, Santiago; Hernández Hernández, Armand; Universitat de Barcelona. Facultat de Ciències de la Terra
[eng] The Azores Archipelago, strategically located in the central North Atlantic, serves as a key location for analyzing regional atmospheric dynamics. Thus, climate reconstructions derived from from sediments of the Azorean lakes are useful for improving our understanding of North Atlantic atmospheric patterns beyond instrumental records. However, the use of such sediments for climate and environmental reconstructions includes complexities, as they are also located in one of the most complex geodynamic regions on the planet. Additionally, early colonization of the archipelago has increased anthropogenic pressure on its ecosystems since settlement. The multi-proxy approach of sedimentary sequences, combined with innovative limnogeomorphic spatial analysis techniques, have facilitated the study of landscape evolution within lake basins of the archipelago and their relationship with the geological substrate. Variable morpho-stratigraphic patterns reflect the morphosedimentary evolution of the depositional environments over the last millennia, within the deep Lake Funda, located on Flores Island, the shallow Lake Caldeirão, on Corvo Island, and the small Lake Caveiro, on Pico Island. The biogeochemical imprint of the sediments from these lakes was variable due to different morphologies of the lake-catchment systems. Furthermore, accelerated sedimentary responses of the systems revealed the increasing anthropogenic transformation of the landscape. The tectono-volcanic configuration of the lake basins modulates the sedimentary responses to hydroclimate and deforestation in the archipelago, emphasizing some effects over others. Verticalized topo-bathymetric morphologies in Funda and the first stages of Caveiro lake-catchment systems evolved with enhanced sediment cascading and reduced evapotranspiration after deforestation that provoked lake deepening. In contrast, the horizontal reliefs of the flat topo-bathymetric morphologies of Caldeirão and the last stages of Caveiro lake-catchment systems promoted paralimnetic sediment storage, and deforestation resulted in marked soil degradation. Furthermore, oriented reliefs in Funda and Caveiro systems induced preferential morpho-sedimentary evolution, whereas chaotic reliefs within Caldeirão system favoured spatial stationarity. The biogeochemical imprint of Caldeirão system sedimentation demonstrated to be the most appropriate for paleoclimatic reconstructions. This is confirmed through correlation between proxy- based and instrumental data. A comparative analysis with the North Atlantic climatic evolution allows for the spatio-temporal evolution of North Atlantic atmospheric dynamics characterized by specific NAO and EA configurations.
Metagenomic Exploration of the Effects of Depth and Temperature on the Microbiome Structure and Function of the Gorgonian Eunicella Singularis and the Cold Water Scleractinia Desmophyllum pertusum
(Universitat de Barcelona, 2024-10-11) Mutlaq S. Binsarha, Mohammad; Logares, Ramiro; Calafat Frau, Antoni; Universitat de Barcelona. Facultat de Ciències de la Terra
[eng] Corals are crucial to marine ecosystems, offering varied habitats for microbial communities that, in return, provide essential compounds for coral health and resilience. Numerous factors, such as coral age, species, health, and environmental conditions like depth and temperature, influence the structure and function of the coral microbiome. Disruptions in the coral-microbe relationship can lead to infections, bleaching, and increased coral mortality. Understanding these influences on the microbiome is vital for deciphering coral-microbe interactions. This thesis explores the coral microbiome concerning depth and temperature variations using highthroughput meta-omics approaches. Our analysis of the influence of depth on the Mediterranean coral Eunicella singularis revealed significant taxonomic and functional differences between shallow and mesophotic zones. Shallow water colonies prominently featured Symbiodinium, essential for photosynthesis, while its absence in mesophotic zones indicated a shift in microbial community composition. In mesophotic water colonies, the microbiome exhibited higher abundances of genes related to carbohydrate, energy, amino acid, cofactor, and vitamin metabolism, suggesting adaptation to diverse nutrient sources and enhanced nutrient availability. Metagenome-assembled genomes (MAGs) analysis identified key taxa, such as DT-91 (Order Pseudomonadales) and Endozoicomonas, involved in nutrient recycling and vitamin production, underscoring their role in maintaining microbiome fitness and coral resilience. Further research is needed to determine the active expression of these genes and their impact on coral health. Additionally, our study on the cold-water coral D. pertusum under prolonged thermal stress revealed significant changes in the microbiome's taxonomic and functional structure. Elevated temperatures correlated with an increase in microbial taxa such as Rhodobacterales and genes associated with carbon metabolism and secretion systems, potentially destabilizing the microbiome and promoting the growth of opportunistic pathogens. Furthermore, we observed a rise in genes related to diazotrophic activity, including denitrification and nitrification, which could disrupt nitrogen cycle balance and heighten disease susceptibility. These findings highlight the importance of environmental factors in shaping coral microbiomes and emphasize the need for further research on gene expression profiles to better understand microbial activity and regulation under stress conditions. Such understanding is crucial for developing strategies to enhance coral resilience in changing environments.
Unravelling causes and consequences of marine biodiversity changes in East Atlantic and Mediterranean ecosystems
(Universitat de Barcelona, 2024-10-25) Veloy Dominguez, Carlos; Coll Montón, Marta; Hidalgo Roldán, José Manuel; Universitat de Barcelona. Facultat de Ciències de la Terra
[eng] Marine communities have been affected by multiple stressors increasing over the last decades, such as overfishing and climate change, resulting in negative effects throughout ecosystems. However, these impacts do not have homogeneous effects globally. Instead, systems across regions experience different impacts and rates of change shaped both by regional and global drivers. Furthermore, organisms within the same community can suffer from different impacts or respond to the same impact in distinct ways due to different ecological traits or life history strategies. These responses can include reductions or increments in the abundance of the populations of affected species, with the term "winners" often used to refer to organisms that may benefit from global change. Another common response, especially to warming, is shifts in distribution ranges. These shifts can be latitudinal, migrating northwards, or vertical, moving towards deeper waters. Previous studies have addressed these processes mainly focusing on abundance and biomass displacements, but a holistic approach that considers several aspects of the ecosystem, such as production, biodiversity and trophic characteristics across different taxonomic groups is still missing. The main goal of this P.hD.was establishing a comparison of areas within the Atlantic and Mediterranean by using an integrative analysis of indicators, calculated from data collected from scientific bottom trawl surveys, and species groups in order to achieve a better understanding of ongoing spatiotemporal changes. Several types of indicators were considered to analyse different aspects of ecosystem functioning and dynamics. To reflect the variety of responses and calculate these indicators, three taxonomic groups were considered (fishes, cephalopods, and crustaceans), in which several traits were analysed. Spatial variability was accounted both at the regional scale by comparing different subregions of the Western Mediterranean and at the oceanic scale with a study comparing the Barents Sea, North Sea, Western Mediterranean, and South African coast. To do that, complementary methods were applied for addressing several specific questions regarding the distribution and ecosystem dynamic. Analyses of subregional differences and temporal trends in the Western Mediterranean were performed using ANOVA and linear regressions, respectively. Then, the relationship between ecological indicators and environmental variables and fishing were studied using Generalised Additive Models (GAMs) to assess the status of alleged taxa winners in the Western Mediterranean and test for bathymetric changes in the indicators in the East Atlantic areas and the Mediterranean Sea. Several regional patterns were detected in the Western Mediterranean, often following the latitudinal gradient of temperature within the area. However, in many cases, interrupted or even discontinuous gradients were reported, due to localised variability in the environment and/or human impacts, especially on the North Catalan coast. In terms of taxa, fishes showed negative trends in most indicators, while cephalopods and crustaceans experienced more favourable results. Despite this, a detailed examination of cephalopods signalled the possibility of negative effects of increasing temperatures beyond certain thresholds. In the East Atlantic and Mediterranean Sea comparison, temporal changes in depth range were reported in several indicators in accordance with the Depth Refuge hypothesis, although they did not follow large-scale gradients but were influenced by the conditions and characteristics of individual regions. Overall, this Ph.D. reveals the existence of numerous spatial patterns and temporal trends regarding marine biodiversity and emphasises the unequal responses to both environmental drivers and anthropogenic pressures among the considered ecological groups. These differences were further signalled by the variation and interrelationship of several indicators, often related to recorded shifts in the community, such as the functional changes in the North Sea and Barents Sea, the eastward migrations occurring in South Africa, or the complex sub-regional combination of fishing and environmental impacts observed over the Western Mediterranean. Overall, these results highlight that environmental change impacts may have notable consequences for ecosystem composition at several scales. The use of ecological indicators and taxonomic groups was proven to be a useful tool to further my understanding on the ongoing marine changes as well as their extent and implications.
Thermal compensation in marine copepods: long-term ecophysiological implications in Paracartia grani
(Universitat de Barcelona, 2024-05-17) Juan Carbonell, Carlos de; Saiz Sendrós, Enric; Calbet Fabregat, Albert; Universitat de Barcelona. Facultat de Ciències de la Terra
[eng] Ectothermic animals are highly sensitive to changes in the environmental temperature. As ocean temperatures rise, a major concern is the potential impact of warming on copepods, which are crucial contributors to marine food webs. However, our understanding of how copepods respond to chronic temperature changes and the underlying physiological mechanisms is limited due to a scarcity of long- term studies. This thesis presents a series of experiments investigating the direct effects of temperature on copepod phenotypic traits across multiple generations. We specifically focused on the calanoid copepod Paracartia grani, exposed at long-term to warmer conditions (+3°C and +6°C). We explored the implications of chronic thermal stress for production, energetics, life-history as well as the copepod’s resilience to extreme events and low food availability. The results showed that higher rearing temperatures accelerated copepod hatching and development rates, resulting in a reduction of the adult body size and elemental content (carbon, nitrogen and phosphorous). Initially, temperature increased the copepod main physiological rates (ingestion, respiration and reproduction), but these effects were compensated within a few generations under warmer conditions, with no relevant costs on multiple life-history traits, including the efficiency of food utilized for reproduction, energetics, nauplii hatching success or the sex ratio. Adult body stoichiometric ratios (C:N, C:P, and N:P) were either altered across generations. P. grani exhibited a broad thermal tolerance range (11-32ºC), and long-term warming (+6ºC) even expanded their tolerance to acute high temperatures (>30ºC). However, prolonged exposure to these temperatures reduced its survival after a week, diminishing the advantage gained from warm rearing. At these extreme temperatures, reproduction was reduced but sustained, thereby expanding the fitness of copepods reared under warming conditions. The thermal resilience of this species to extreme temperatures was highlighted when subjected to sub- lethal thermal stress (28ºC), which did not affect the metabolic balance of copepods regardless of the rearing temperatures (19, 22 and 25ºC). As a main trade-off, following chronic warming the food uptake under low food conditions of the prey Rhodomonas salina was highly reduced, potentially indicating a decline in feeding efficiency and subsequent reduction in reproductive activity. Overall, the research carried out in this thesis suggests that P. grani has a large capability to adapt to temperature increases, maintaining key activities, like grazing and production. Nevertheless, an increase in thermal anomalies, low food availability, or the combination of both factors may limit their capacity to persist in their local environment. Given that the thermal effects on development were not compensated at long-term, size reductions in copepods might be a major consequence of ocean warming, with important ramifications for marine food webs and biogeochemical cycles.
Delivering insights into diversity and ecology of marine chytrids
(Universitat de Barcelona, 2024-04-04) Fernández Valero, Alan Denís; Garcés, Esther, 1970-; Reñé Vicente, Albert; Universitat de Barcelona. Facultat de Ciències de la Terra
[eng] Current knowledge of marine fungi is limited, marked by gaps in the understanding of their diversity, spatio-temporal patterns, and ecological roles within marine ecosystems. The underexplored nature of specific fungal groups, like chytrids occurring during phytoplankton blooms, and the lack of research in most marine regions, such as the Mediterranean Sea, emphasise the need for this thesis. Consequently, the main objective of this doctoral thesis is to investigate the composition of the fungal community in the Mediterranean coastal ecosystem, with a focus on the basal fungal group Chytridiomycota (chytrids). The study sets for specific objectives: i) to evaluate the spatial distribution of Chytridiomycota diversity in various coastal areas during dinoflagellate proliferations; ii) to evaluate the temporal dynamics of the fungal community in epiphytic communities during benthic dinoflagellate proliferations and to investigate their interaction with hosts; and iii) to identify and describe new parasitic Chytridiomycota species associated with their host proliferations. The chytrid community in coastal environments is particularly dynamic and diverse, with a marked specificity towards their preferred hosts. These communities are more diverse and abundant in sediments and on macroalgae surfaces than in the water column. The relative abundance of chytrids increases in the water column during dinoflagellate proliferations, suggesting their opportunistic parasitic behaviour. In the laboratory, strains of four chytrid species, including the most abundant species detected by metabarcoding sequencing, have been cultured and identified by co-culture techniques with dinoflagellates. Three strains correspond to as yet undescribed species and the cultures have allowed the morphological and molecular characterisation of two of them, Dinomyces gilberthii and Paradinomyces evelyniae, which have been newly described in this thesis. In terms of geographic distribution of species, Dinomyces gilberthii is widely distributed in coastal Mediterranean habitats particularly during summer dinoflagellate blooms. Conversely, species like Paradinomyces evelyniae exhibit a more limited distribution in these habitats. Investigations into the temporal dynamics of the fungal community on poorly explored niches such as biofilms in macroalgae, revealed an alternation in the abundance of fungal groups, significantly influenced by the epiphytic dinoflagellates dynamics. Dominant chytrid species in these communities, such as Dinomyces arenysensis, exhibit adaptability in their survival strategies, including trophic versatility. The findings demonstrate that chytrids play a significant role in the structuring of planktonic and benthic microbial communities in the coastal ecosystems.
The potential of carboxylesterase activity in the biomonitoring of marine pollution
(Universitat de Barcelona, 2024-02-06) Nos Francisco, David; Solé i Rovira, Montserrat; Navarro Bernabé, Joan; Universitat de Barcelona. Facultat de Ciències de la Terra
[eng] Understanding and monitoring the impacts of pollution on marine ecosystems leads the list of challenges of the United Nations Ocean Decade as crucial steps towards achieving a healthy ocean. The marine environment faces a constant influx of chemical pollutants from land, marine and atmospheric sources, resulting in complex pollutant mixtures that can cause a cascade of responses on marine biota, from biochemical to physiological. Biochemical responses, in particular, can serve as early biomarkers of exposure, susceptibility, or effect. Among them, carboxylesterases (CEs) are enzymes that hydrolyze a variety of substrates, and offer a cost-effective tool for monitoring marine pollution, especially in scenarios involving chemical mixtures. However, the current efforts are limited to few sentinel species mostly found in coastal environments. This Ph.D. thesis aims to broaden the knowledge on the use of CEs as biomarkers as well as to identify alternative sentinel species across different trophic levels and ecological niches in the under-monitored pelagic realm. Biomarker activities, in vitro inhibition tests, biological parameters (e.g., body size, body mass, sex or reproductive season) and environmental factors (e.g., sea temperature, salinity or dissolved oxygen) were considered in combination to unravel the response of CEs to pollutants of environmental concern and their natural variability. Among sentinels, we propose copepods (Paracartia grani and Centropages typicus), small pelagic fish (Sardina pilchardus and Engraulis encrasicolus), large predatory fish (Euthynnus alletteratus, Sarda sarda, Auxis rochei and Thunnus alalunga) and an opportunistic seabird (Larus michahellis). CEs activities and their sensitivity to chemicals of concern and specific inhibitors were assessed, highlighting the inhibitory potential of tetrabromobisphenol A at high levels of the pelagic trophic net. Moreover, the influence of biological and environmental parameters on CEs activities were evaluated in small pelagic fish, large predatory fish and gulls, being age, sex and the reproductive status the main factors modulating CEs activities. Overall, the findings of this Ph.D. thesis contribute to demonstrate how biological and environmental factors affect some biomarkers and particularly CE activity, making them relevant variables to take into account when interpreting biomarker responses. Additionally, we characterized and evidenced the species-specific differences on basal CE activities. Together, our contribution is a step forward towards the establishment of CEs as biomarkers of pollution not only in the marine pelagic environments but also in urban areas with anchovy and yellow-legged gulls as respective sentinels.
The importance of seasonality at different levels of ecological organization in the marine ecosystem of the Northwestern Mediterranean Sea
(Universitat de Barcelona, 2023-05-17) Lloret Lloret, Elena; Coll Montón, Marta; Navarro Bernabé, Joan; Universitat de Barcelona. Facultat de Ciències de la Terra
[eng] From an oceanographic perspective, seasonality has been widely studied, and abundant research exists about low trophic level organisms such as phytoplankton and zooplankton. Nevertheless, at a regional scale, this information is not always homogenous and certain areas lack longer time series to track seasonal cycles. This knowledge gap is emphasized as one moves to higher trophic level organisms, whose studies tend to focus on single seasons or inter-annual variation rather than on seasonal changes and intra-annual dynamics. This Ph.D. thesis aims to broaden the knowledge about the marine ecosystem of the Northwestern Mediterranean Sea incorporating the importance of seasonality in key ecological processes, such as body condition, fitness, spatial distribution, and trophic ecology of marine species, and, finally, the structure and functioning of marine food webs. Seasonality is approached at different levels of the marine community, including the demersal component focusing on commercially important species of fish (Merluccius merluccius, Lophius budegassa, Lophius piscatorius, Mullus barbatus), crustaceans (Liocarcinus depurator, Squilla mantis) and cephalopods (Illex coindetii, Eledone cirrhosa), the pelagic component targeting the most abundant and commercially important small pelagic fish species (Sardina pilchardus and Engraulis encrasicolus), and at the ecosystem level using system indicators. To attain these objectives, various methodological approaches have been combined, such as species distribution models, stable isotopes analysis, bayesian isotope mixing isotope models, analysis of biometrical/biophysical parameters (Kn, GSI, fat content), generalized additive models and ecosystem modelling. Results show seasonal variations in species distribution with species-specific patterns in the case of demersal species. Bathymetry, temperature and fishing effort are important drivers explaining biomass spatial distribution of these species. European hake is further studied in one of the chapters, and the predicted posterior mean weight distribution also presents spatial differences between winter and summer. Ontogenetic and seasonal variations are also detected in the diet of this species. Spatial and seasonal variations in fitness are found at the local scale for European sardines and anchovies. These changes are mostly explained by environmental variables while spatial and seasonal factors are also important. Moreover, trophic variables also contributed to the species dynamics, suggesting that variations in prey abundance, composition and quality can impact their fitness. At the ecosystem level, we investigate changes in indicators of ecosystem structure and functioning when using seasonal input data vs annual averages in marine ecosystem models for the characterization of our study area. We find several indicators showing significant variations in ecosystem structure and energy transfer. Overall, the findings of this Ph.D. show seasonal variation at different levels of biological organization and in various ecological processes, which highlights the relevance of seasonality in the marine realm, specifically in the Northwestern Mediterranean Sea. Therefore, we can conclude that considering seasonality in ecological studies can provide complementary insights into our understanding of species biological and ecological dynamics, which cascades up to the knowledge about ecosystem structure and functioning.
Transformations and pathways of Southern Ocean waters into the South Atlantic Ocean
(Universitat de Barcelona, 2023-03-20) Olivé Abelló, Anna; Pelegrí Llopart, Josep L. (Josep Lluís); Machín Jiménez, Francisco; Universitat de Barcelona. Facultat de Ciències de la Terra
[eng] The returning limb of Atlantic Meridional Overturning Circulation (AMOC) is partly supplied by the cold-fresh waters that enter through the Drake Passage. Up to the isoneutral 28.0 kg m−3, the mean water inflow through the Drake Passage to the Scotia Sea is 140.8 ± 7.4 Sv and the outflow through the Northern Passages is 115.9 ± 8.3 Sv. Below this isoneutral reference and down to 2000 m, an additional 23.4 Sv enters through the Drake Passage. The mean barotropic contribution always represents over half the total transports, with substantial seasonal and moderate interannual variability in the water transports. The water mean-residence time is about 6 - 8 months. Combining the Argo floats data with other observational measurements, we apply a climatological high-resolution inverse model over the Scotia Sea boundaries up to the 28.0 kg m-3 isoneutral. The ACC enters 136.7 ± 1.0 Sv through the Drake Passage and exits 137.9 ± 1.0 Sv through the northern boundary, with the difference responding to the South Scotia Ridge and Philip Passages contributions. Along its northward path, the ACC waters lose heat but gain equatorward freshwater transport. Within the Scotia Sea, the surface-modal and modal-intermediate waters experience production in all biogeochemical variables. Finally, regarding anthropogenic DIC, the Scotia Sea stores 0.123 Pg C yr-1. Then, the ROD method compares actual drifters' displacements with numerical trajectory predictions; the observed-predicted differences in final positions respond to diffusive motions not captured by the numerical models. The ROD method is applied in the western South Atlantic Ocean leading to maximum diffusivities of 4630 - 4980 m2 s-1 in the upper 200 m of the water column, presenting an inverse relationship with depth. The diffusivities near the surface are fairly constant in latitude but the diffusion coefficients at 1000 m decrease considerably south of the Southern Boundary. With the horizontal diffusion coefficients obtained previously, we use the Lagrangian technique to determine the fraction of the upper-ocean transport that remains in the ACC flow as it crosses the South Atlantic Ocean and the fraction that contributes to the South Atlantic subtropical gyre. The mean results reveal that 94.8 Sv remains in the ACC, whereas a total of 15.1 Sv contributes directly to the AMOC. This AMOC transport takes a median of 14.3 years to arrive to the Brazilian Current from the Drake Passage. Furthermore, 78.1% of the particles that recirculate in the subtropical gyre perform one recirculation. The results confirm that the water masses entering the subtropical gyre through its eastern edge warm up substantially and lose density, partly transformed to surface waters. Furthermore, the contributions at the eastern edge of the South Atlantic subtropical gyre from the warm-water and the cold-water routes are compared. We perform numerical simulations of Lagrangian trajectories to identify the multiple direct and indirect pathways of intermediate waters. The total cold-route contribution represents between 17.9 and 18.9%, substantially higher than the 7.1 to 12.3% warm- route contribution. Several individual pathways form both routes, but the direct path is the preferential pathway followed by 83.6 to 87.2% of the water parcels. The direct cold route is the one that undergoes a greater transformation of its water masses, and it is confirmed that also feeds the Agulhas Current, contributing similarly to that coming from the Indonesian Throughflow.
No-take fishery reserves for restoring overexploited deep-sea habitats: the case of the Norway lobster Nephrops norvegicus in the northwestern Mediterranean Sea
(Universitat de Barcelona, 2023-10-30) Vigo Fernandez, Maria; Company Claret, Joan Baptista; Navarro Bernabé, Joan Josep; Universitat de Barcelona. Facultat de Ciències de la Terra
[eng] In September 2017, a no-take fishery reserve was established in the deep waters of the northwestern Mediterranean Sea, specifically focused on recovering the Norway lobster (Nephrops norvegicus) population. The main objective of this Ph.D. thesis is to evaluate the effectiveness of this no-take reserve as a tool for restoring overexploited demersal populations. In the first study, the biological parameters of the Norway lobster population in the northwestern Mediterranean Sea were updated, providing information about the status of the fishery and the population, which showed signs of overexploitation. To evaluate the effects of the no-take reserve, potential predators of the Norway lobster in the northwest Mediterranean were first identified using genetic markers and stable isotopes. It was confirmed that the size of the marine reserve was adequate by conducting tagging and recapture experiments to describe its spatial ecology and reveal its territorial and solitary behavior. The effectiveness of the reserve was evaluated using a Before-After-Control-Impact (BACI) approach, conducting experimental fishing surveys both inside the reserve and in a control zone where fishing was allowed. Through a non-invasive methodology using Remotely Operated Vehicles (ROVs), the species community and habitat were also monitored. All results indicated signs of Norway lobster recovery within the reserve in terms of abundance, biomass, size structure, and other associated species. Finally, several configurations of no-take fishery reserve networks were simulated using the spatial planning tool "Marxan". These scenarios included a dynamic management approach to adapt the reserves according to seasonal fluctuations in species and associated costs. The simulation results showed that dynamic scenarios achieved all conservation objectives with a lower opportunity cost than the static network. Overall, this thesis highlights the potential of spatial management measures to contribute to the recovery and sustainability of fisheries and the conservation of marine ecosystems. Although the Norway lobster population has been used as a case study, the approach can be applied to many other species and help address the global concern over the decline of fish populations.
Experimental and numerical study of chemo-hydro-mechanical effects of CO2 injection on permeable limestone
(Universitat de Barcelona, 2023-07-07) Vafaie, Atefeh; Cama i Robert, Jordi; Soler, Josep M.; Universitat de Barcelona. Facultat de Ciències de la Terra
[eng] Carbon capture and storage (CCS) in saline aquifers is a proven technology aimed at reducing atmospheric CO2 emissions and mitigating the climate change crisis. CO2 injection acidifies the formation water inducing mineral dissolution and alterations in the pore structure and hydromechanical properties of the rock, particularly in carbonate reservoirs with large contents of fast-reacting minerals. Improving the current understanding of the form, extent, and governing mechanisms of such interactions is central to optimizing and securing the implementation of CCS and serves as the primary goal of this study. To achieve this goal, this study combines (i) percolation experiments with CO2-saturated water and HCl solutions on cm-scale cores of highly permeable Pont du Gard Limestone and (ii) 3D Darcy-scale reactive transport simulations of the performed experiments. Effluent chemistry analyses, X-ray Micro Computed Tomography (XMCT) imaging, and measurements of the hydromechanical properties of intact and altered specimens are employed to quantify acid-induced changes in the two acid-rock systems. Further, a digital rock approach is developed to construct heterogeneous permeability maps of the intact specimens from CT images that feed as inputs into 3D Darcy-scale reactive transport models. Experimental results show that the acid type and pore space heterogeneity have primary control on dissolution patterns formed in limestone specimens and the resulting alterations in their hydromechanical properties. Under the flow conditions of these experiments, the complete dissociation of HCl as a strong acid leads to rapid limestone dissolution and the formation of compact dissolution patterns that only affect the hydromechanical properties at the core inlet. In contrast, partial dissociation of H2CO3 as a weak acid extends the dissolution reaction along the core and induces wormhole formation that markedly enhances the rock permeability. Altered cores render significant attenuation in both mechanical rock properties and ultrasonic velocities. Chemically-driven alterations in rock stiffness are reproduced using a Differential Effective Medium (DEM) homogenization approach. Numerical simulations using the 3D Darcy-scale reactive transport model satisfactorily reproduce the experimentally measured changes in effluent chemistry, porosity, permeability, and the observed dissolution features in CT images of reacted limestone samples. Simulation results indicate that the pore space heterogeneity controls calcite dissolution from the very beginning of acidic fluid injections while the acid type becomes progressively important as the reaction front further penetrates into the rock. The compact dissolution pattern formed in the HCl-limestone system can be numerically captured using the classical Kozeny-Carman porosity-permeability relationship with a power-law exponent of 3 applied to the grid blocks of the numerical domain. In the case of CO2 injection, however, formation of wormhole by continuous acid renewal exerts strong feedback between the fluid flow and the dissolution reaction. This dissolution pattern can only be reproduced using an exponent as large as 15 that increases to ≈ 27 for the bulk behavior of the core containing a wormhole. This demonstrates that acid-induced permeability evolution in carbonate rocks is highly scale-dependent. The percolation experiments performed using CO2-saturated water represent a severe scenario of CO2-brine-rock interactions in carbonate reservoirs that needs to be considered in predictions and monitoring of CO2 storage. This study highlights (1) the importance of small-scale heterogeneities in controlling flow properties and localization of flow and chemical reactions in limestones and (2) the need for developing rigorous upscaling approaches to account for them in field-scale simulations.
Volcanic risk assessment at Irazú volcano, Costa Rica
(Universitat de Barcelona, 2023-11-23) Campos Durán, Daniela; Martí i Molist, Joan, 1957-; Alvarado Induni, Guillermo E.; Universitat de Barcelona. Facultat de Ciències de la Terra
[eng] Irazu is the highest volcano in Costa Rica (3427 m.a.s.l.); it constitutes an andesitic shield, with two main craters at the top and several pyroclastic cones cuspidal, and adventitial on the South Flank. The first historical eruption was registered in 1723, and other eruptive episodes took place in 1917-1921, 1924, 1928-1930, 1933, 1939- 1940 and 1963-1965. These eruptive events were characterized by phreatomagmatic, strombolian and phreatic phases that generated pyroclastic fall deposits, pyroclastic density current (PDC) deposits and lahars. The 1963-1965 eruptions had considerable effects on the population, crops, and pastures, as well as on civil works (collapse of roofs and bridges). The most considerable economic losses occurred in the Greater Metropolitan Area (GAM), mainly due to ash and lahars. We have reconstructed the tephro-chronostratigraphy of the last 2.6 ka of the Irazu volcano, these data allowed us to estimate that this volcano has had an eruptive frequency that ranges between 23 and 100 years, with a major event every 85 years (VEI between 1 and 3). Furthermore, this eruptive reconstruction was the basis for carrying out a long-term hazard assessment, which has been conducted by us in two steps a) a spatial analysis (susceptibility) and b) a temporal analysis. Regarding susceptibility, we determined that the highest values correspond to the Main Crater area, from where all historical eruptions have been vented. On the southern flank we identified an area with medium susceptibility values due to the presence of fissures and scoria cones that were active during the Holocene, therefore, we cannot rule out a possible future eruptive foci on this flank. In the case of the temporal analysis, we could expect for a five-year window a magmatic unrest that results in a magmatic eruption in the Main Crater with VEI ≥1 (that is, VEI between 1 and 3), with pyroclastic falls, short PDCs, ballistics and lahars (mainly on the south and southwest flanks), similar to the eruptions of 1723-1724, 1939-1940, or 1963-1965. A geothermal unrest (the least likely) culminating in a phreatic explosion is also conceivable. In the case of a three-years forecasting window, we obtained a significant probability of an eruption of VEI=3 with ashfall, lahars, PDCd and ballistics, all of an extension similar to the eruptive episode of 1963- 1965. The other probable scenarios (VEI between 1 and 3) could range between ashfall and lahars of medium to large extent, in lower ballistic grades and low magnitude earthquakes (between 3.1-5.0 Mw). It is important to highlight that, for all possible scenarios, the ashfall would mainly affect the southwest flank, while in the case of lahars it would affect the south and southwest flank, and for the PDCd and ballistics, they would be restricted to the Main crater area. The inputs generated with the spatial and temporal analysis were the basis for determining that the 1963-1965 eruptive scenario (VEI=3) is the one that represents the greatest hazard, so we reconstructed and simulated all the hazards that were registered in that episode, which allowed us to define three hazard areas: high, medium, and low. This information was the basis for carrying out an analysis of population, land use and critical infrastructure exposure. Among the most relevant results we have that currently more than 2.5 million people live in the GAM, mainly at urban areas in the cities of San Jose and Alajuela, where the development of the industrial sector is concentrated. On the other hand, in the surroundings of Irazu , rural communities base their economy on agricultural activities. Likewise, there are more than 150 informal settlements exposed to the lahar hazard. Regarding educational and health centers, the majority are located in sectors of the GAM exposed mainly to the impact of ashfall. Finally, we provide an essential contribution to territorial planning, which must consider hazards of volcanic origin within the planning processes for updating and improving emergency plans to face future volcanic crises.
Mid-Late Pleistocene glacial dynamics in the Valira valleys (Principality of Andorra). Asymmetries within the Pyrenees and correlation across the westernmost European mountain ranges
(Universitat de Barcelona, 2023-04-24) Turu, Valentí; Oliva Franganillo, Marc; Universitat de Barcelona. Facultat de Ciències de la Terra; Geochemistry
[eng] Many sediment-covered mountain areas affected by the growth of Pleistocene glaciers are over-consolidated. Palaeoglacial conditions are deduced from glacial consolidation and site investigations. Geomorphological evidence on the glacial extent and history is in this Thesis used as a framework for hydro-mechanical flow simulations in the valley glacier of Andorra and the lower Isère glaciated valley. From the effects observed within the fossil record of ancient glaciated valleys, a reliable reconstruction of palaeo-glacier’s thickness is possible when former ice-tonges overlayed porous aquifers, because subglacial erosion was mitigated by the subglacial water pressure limiting subglacial till formation. Records of minimum preconsolidation values indicate a buoyant surging glacier. For palaeoglacier reconstruction, the glacial valley geomorphology is clue providing the palaeogeographical calibration for further hydrogeomechanical calculations, especially at successive glacial stages during the deglaciation. A modern analogue, the Hansbreen sub-polar glacier, helps to set up a conceptual model allowing a better understanding of the glaciology of the two studied former valley glaciers, comparable to a polythermal glacier type. Tills and glaciolacustrine deposits from Andorra’s main valley and its principal tributary of La Massana allow for reliable local deglaciation patterns between GS-9 (40 ka b2k) and the Holocene Optimum (9.3–5.5 b2k). However, from the palaeoenvironmental data of the Pyrenees, deglaciation started sooner, and aridity affected the size of the glaciers from GS-10, resetting the valley glacier conditions ahead of GI-7. This affected the mainly prominent glacier-ice transfluence pass in the Pyrenees and the extension of the ice tongues on both sides of the mountain belt between GI-9 and GI-7, also during GS-5.2 and GI-5.1. During and posteriorly Heinrich event H4, aridity did not favour the development of valley glaciers in Andorra until stadial GS-7; however, glaciers in the Pyrenees progressed during the following Heinrich event (H3). Using geochemical data (Al, Ti, Ca, K, P), a basic limnological study permits a palaeoenvironmental interpretation in Andorra by adding data from stable carbon isotope (δ13C) from bulk carbon samples and AMS dates. Results show four unreported inland δ13C cycles linked to low water levels in the ice-dammed lake of Andorra (La Massana palaeolake). At the beginning of each cycle, enhanced δ13C bulk carbon values are found (> -23‰), a proxy of abrupt shifting from Type-C3 to Type-C4 vegetation. The beginning of the LGM and Heinrich events H3 and H2 were marked by enhanced δ13C values interpreted as a product of strong climate change that boosted aridity. The retrieval period towards δ13C depleted values (< -23‰) spans 4,500±500 years. In Andorra, the beginnings of H3 and H2 events were relatively dry, and the second half of the climate was moist. The first evidence of sediments coming from the motion of a temperate-base glacier in the Pyrenees was from stadial GI-3. Moist conditions suddenly stopped at the beginning of Heinrich event 2 and returned at the end of H2. This moisture behaviour during H2 on the southern slopes of the Pyrenees is the opposite of the wet-to-dry conditions described in NW Iberia. Conversely, the H1 event had a wet-to-dry structure coast to coast of Iberia, including in the SE Pyrenees (Andorra). A transition from single-phase-like glacier advances (NW Iberia) to multiphase glacier advances (SE Pyrenees) was due to a change from coldbased glaciers to temperate-based glaciers. However, glacier sensibility to global changes increases through time toward NW Iberia. The Last Maximum Ice Extent and the Global LGM did not concur in places experiencing multiphase glacier advances. Indeed both extreme behaviours do not correspond to the same type of glaciers. Polar-type glaciers in NW Iberia are in this Thesis invoked, while tempered or polythermal were frequent in NE Iberia. Abrupt glacier advances and quick glacier recession in Andorra are interpreted as surges from a mass-imbalanced glacier. Two kinds of surge events are distinguished from available data in the Pyrenees, those surges produced by overfed ice tongues fed by short-lived cold spells (in GS-2b and H1) and those surges produced by buoyant melting ice tongues within the glaciated valley (between stadials GS-5/GI-4, stadials GI-3/GS-3 and stadials GS-2.1b/GS-2.1a) by a warm moist climate. The winter solar rate increase (GI-3 and GS-5.1) and the evidence of polythermal-type glaciers matched. Conversely, summer insolation increases and wet-ice type oversaturated glaciers and surges at GS-2a concurred. In Andorra the snow-overfed glacier surges correlate with the decreasing winter insolation during GS-2b. In Iberia, the LGM would be placed between 23-17.5 ka and glaciers spread, linked to both wet westerlies from the North Atlantic and moisture supply of Mediterranean influence, reaching almost the eastern side of the Central Pyrenees, leading us to suppose an NW-NE seesaw climatic relationship across Iberia almost since GS-5.1. The oscillations of the oceanic thermal front promoted wet/dry westerly winds crossing over the Pyrenees, pushing back the Mediterranean influence towards the East. By classifying glacial phases of the northern Iberian Peninsula fringe, four common glacial phases arise for the last glacial cycle: A An early LGC starting at MIS 5d having a recessional period during MIS 5c. Cold-type glaciers are expected to have existed in some of the extreme NW of the Iberian mountains until Termination 1. B The Last Maximum Ice Extent occurred mainly during MIS 5a – MIS 4. An asymmetrical glacier recession during MIS 3 was related to an increase in eastward aridity. C Significant glacier fluctuations during the MIS 3 – MIS 2 hinge, the appraisal of temperated-polythermal type of glaciers accompanied by a generalised moisture increase entailing valley glaciers to surge. D Side-to-side mountain range-scale deglaciation dissymmetry in MIS 2. The widespread expansion of tempered-polythermal type glaciers during the LGM period and Termination 1 had a proportional expansion to the available moisture. The final deglaciation is characterised by relictual cirque glaciers disappearing during GS-1. In Andorra, a general rise in local river base levels occurred until the Holocene Optimum. Unravelling the afore-cited glacial phases and unexpected research allows for a tesselated mapping of the SW continental Europe concerning part, or all of the LGC glacial phases outlined above: 1 – Areas where glaciers were prevalent during MIS 2, like the Iberian Central System, the NW and S French Massif Central, the NW Jura and the maritime Alps. 2 – Areas having a far-flung end moraine produced in a previous glacial phase (MIS 6 or posterior) showing stability until the MIS 2, as for ice caps/fields from the southern half of the Galicia mountains. 3 – Areas of pseudo-pleniglacial or apparent-pleniglacial condition, despite previous glacier recessions phases (albeit challenging to identify), as in most of the northern slope of the Pyrenees. 4 – Areas of multiphase glacier advances, like most of the southern slope of the Pyrenees, most of the Cantabrian Mountains, the half north of the Galicia mountains, the High Atlas, Sierra Nevada and the SW French Massif Central, the western Alps and the Vosges. 5 – Areas where glaciers were present from the LGM until Termination-I, like the northern Iberian range and Sanabria in Iberia. Nevertheless, other mountain ranges have a Type 5 glaciation’s scenario, like the southern Black Forest in Germany.
Shear Waves Characterization of the Sub-surface: Imaging Active Fault and Critical Zone along the Eastern Betic Shear Zone, SE Iberian Peninsula
(Universitat de Barcelona, 2023-02-16) Handoyo; Carbonell, Ramon; Alcalde Martín, Juan; Universitat de Barcelona. Facultat de Ciències de la Terra
[eng] The Earth System is formed by four components that sustain life: the atmosphere, the biosphere, the hydrosphere and the geosphere. The complex region in which these elements interact is known as the ‘Critical Zone’. The critical zone (CZ) is crucial for our society, as it is host of a diverse range of hydrological, geochemical, and biological processes that operate on numerous scales and shape landscapes, support ecosystems, and control resource availability. The CZ and by extension the shallow subsurface is also the host to human activity and infrastructure, and it is therefore vulnerable to natural hazards, such as extreme weather events, volcanic activity or earthquakes. Thus, it is key to investigate and monitor the shallow subsurface, to understand its geometry, extent and physical properties in order to produce comprehensive hazard assessments that could take place in connection to this important layer. The southeastern part of the Iberian Peninsula is characterized by moderate but intense earthquake activity that has caused significant damage since historical times. The seismicity in that area is distributed within a relatively broad deformation band parallel to the coast that includes a well-developed strike-slip fracture system. This deformation band is known as the Eastern Betic Shear Zone (EBSZ) and, runs along the southern border of the Guadalentín Depression, it is a densely populated area with extensive agricultural activity. Therefore, the activity of the faults in the EBSZ represents a seismic hazard with a very significant social and economic impact potential. This memoir focuses in the characterization of the shallow sub-surface structure including the CZ and, characteristics of the Carrascoy and Alhama de Murcia fault systems, SE Iberian Peninsula. To achieve this characterization, different shear wave seismic velocity-depth models based on Multichannel Analysis of Surface Waves (MASW) were constructed. These models were complemented with investigations involving P-wave tomography and/or Electrical Resistivity Tomography (ERT) methods, as well as surface geological observations (e.g. mapping and paleoseismological trench studies) to constrain physical properties models of the subsurface. S-wave velocities were estimated from the surface waves recorded within the controlled-source shot records of conventional normal incidence seismic reflection data. P-wave velocity models were determined from first arrival travel-time tomography. The resulting velocity-depth models revealed: i) the location, geometry and extent of shallow fault zones, and their associated damaged unconsolidated zones, new blind faults were also identified; ii) the thickness of the critical zone and its relation with fault zones in the target areas; and, iii) provide valuable information about the fault network for seismic hazard assessments. The seismic signature of the fault zones, including these of the multiple blind faults and fractured zones identified in the different profiles, was well demonstrated using 2D velocity depth models (S- and P- waves). Seismic signatures of fault zones and blind faults are indicated in the models by low-velocity anomalies. Vs velocities in the range of 500-1000 m/s and Vp within the range of 1300-1700 m/s. These low values indicate a reduced bulk- and shear-modulus along and around the fault plane. The velocity model images across the Carrascoy and La Torrecilla reveal higher number of faults than what is imaged in the La Salud South and La Salud North profiles. This might be indicative of differences in the maturity degree of the fracture zones involved. Being the former more mature than the latter. The models obtained have resolved the geometry and characteristics of the CZ in the neighborhood of faults/fracture zones. It is characterized consistently by relatively low seismic velocities Vs < 600 m/s and Vp < 1300 m/s, which is consistent with the expected low resistivity layer of Quaternary alluvial unconsolidated sediments in the La Torrecilla, La Salud North, and La Salud South profiles, as well as the Unidad Roja (Red Unit) and the Pleistocene-Quaternary alluvial in the Carrascoy profile. The thickness of the CZ in La Salud North profile lies within the range from 35-45 m and in La Salud South profile within 40-47.5 m. Furthermore, the thickest CZ layer constrained in the La Torrecilla profile features a thickness of ca. 40-50 m. The thinnest CZ is located in the Carrascoy profile with a thickness of ca. 30-40 m. In addition, the results also reveal a relation between fracture/fault zones and the thickness of the CZ. The presence of faults can contribute to the observed topography of the CZ in two ways: changes in bedrock elevation as a consequence of fault geometry changes and/or an increase in the number of regolith layer fragments, with the CZ layer near the fault zone becoming relatively thicker than in places far away from the fault zone. The shear wave characterization of the sub-surface presented in this memoir provides a methodological and workflow protocol to study the shallow subsurface in areas with active deformation, providing geometry and depth constraints to the structures interpreted in the geological models based on paleoseismological trenches, and, therefore, these can be used for improving the seismic hazard assessment and provide a detailed characterization of the CZ of this and other tectonically active regions in the world.

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