http://hdl.handle.net/10498/10857 2026-11-05T20:23:33Z 2026-11-05T20:23:33Z Osorio-Granada, Ana Maria http://hdl.handle.net/10498/37118 2025-09-09T00:06:54Z 2025-04-22T00:00:00Z

Estudio mediante tecnologías acústicas y geofísicas para la exploración del fondo marino. Aplicación para la detección de acumulaciones de gas somero en el Mar Caribe colombiano Osorio-Granada, Ana Maria La exploración de los océanos utilizando métodos geofísicos ha permitido avanzar en el entendimiento del sistema Tierra-Océano y su comportamiento a través del tiempo. Nuevas tecnologías en métodos acústicos, geodésicos, geofísicos, en teledetección y a su vez en la optimización de la gestión de información espacial y repositorios de datos; ha jugado un papel clave en las observaciones e interpretaciones de los ambientes oceánicos en las últimas décadas. La presente Tesis Doctoral revela el estudio morfo-estructural en dos contextos submarinos y geodinámicamente distintos en el margen continental del Mar Caribe Colombiano. Para estos estudios, se han implementado tecnologías acústicas y geofísicas, utilizado fundamentalmente datos adquiridos a través de las plataformas satelital y marina. Por un lado, en la cuenca Los Cayos, en el Caribe occidental, se han estudiado y discutido escenarios alternos acerca de la naturaleza de la corteza y el basamento de la cuenca y la zona insular; a través del modelamiento e interpretación de anomalías gravimétricas y magnéticas. Por otro lado, en las áreas marinas del Urabá, región offshore del Cinturón Plegado del Sinú se ha investigado la presencia de gas en los sedimentos marinos superficiales (situados a una profundidad de 1000 m); mediante el análisis de perfiles del subsuelo y batimetría de alta resolución. El objetivo principal del estudio de anomalías gravimétricas y magnéticas ha sido realizar el modelado 2D de propiedades como la susceptibilidad magnética y la densidad, discriminando entre bloques de corteza, geometría de los sedimentos y fuentes causantes de anomalías en la Cuenca Los Cayos. En el sector offshore del Cinturón Plegado del Sinú el estudio se centró en gran medida en las ocurrencias de gas en los sedimentos poco profundos. Dado que los sedimentos que contienen gas pueden causar anomalías tanto en el fondo como en el sub-fondo marino; el uso de herramientas de alta resolución ofreció la oportunidad de investigar las formas de ocurrencia y distribución en profundidad de gas en los sedimentos. La investigación presento avances en el conocimiento de la estructural cortical y dinámica geológica en el margen continental del Caribe colombiano mediante tecnologías acústicas y geofísicas avanzadas. En este estudio, las mediciones magnéticas y de gravedad muestran numerosas anomalías con firmas geofísicas distintivas, revelando la presencia de cuerpos geológicos densos y altamente magnéticos; asociados a eventos volcánicos en el fondo marino. Se concluye que la Cuenca Los Cayos posee una corteza de afinidad oceánica, vinculada a la Provincia Ígnea del Caribe, con un adelgazamiento cortical en la Depresión de San Andrés. Además, las anomalías de campos potenciales destacan una estructura heterogénea con profundidades de basamento entre 2 y 6 km, y la superficie de Moho a unos 18 km por debajo de la cuenca. En el Cinturón Plegado del Sinú, se concluye que existen evidencias acústicas que indican la ocurrencia de gas en los sedimentos superficiales. En el área se detectaron y mapearon acústicamente más de 30 anomalías dentro de una profundidad sub-superficial de ~65 m y dentro de un área de 1000 km2 en la plataforma y porción superior del talud continental, con profundidades de agua que varían entre 20 y 1300 m.

2025-04-22T00:00:00Z Sánchez Rodríguez, Jairo http://hdl.handle.net/10498/36266 2025-05-14T00:07:21Z 2025-01-23T00:00:00Z

Dinámica de gases invernadero en un sistema estuarino Sánchez Rodríguez, Jairo El objetivo de esta tesis doctoral es mejorar el conocimiento sobre la dinámica del dióxido de carbono (CO2), metano (CH4) y óxido nitroso (N2O) en el estuario del Guadalquivir. Se realizaron 11 muestreos entre 2017 y 2022 a bordo del B/O UCadiz, que incluyeron transectos longitudinales de hasta 20 estaciones a lo largo del gradiente de salinidad y ciclos mareales en diferentes zonas del estuario. Además, se llevaron a cabo fondeos de cámaras bentónicas autónomas de 8 horas de duración en un total de 13 estaciones. Esta estrategia de muestreo ha permitido obtener una visión integral de los procesos que afectan a la variabilidad espacial y temporal de los gases con efecto invernadero en el estuario y establecer patrones de intercambio con las mareas. Los valores de pCO2 (386.3 - 5865.6 µatm), CH4 (4.9 - 463.2 nmol L-1) y N2O (4.8 - 103.3 nmol L-1) aumentan hacia el interior del sistema y son generalmente mayores en verano. Se propone una metodología que permite descomponer la variabilidad experimental de estos gases en factores que recogen el efecto de la temperatura, salinidad, flujos agua-atmósfera, flujos bentónicos, reactividad en la columna de agua y las entradas laterales. La temperatura y la salinidad tienen poca influencia en la variabilidad total de pCO2, CH4 y N2O. La temperatura explica solo el 1 % de la variabilidad en pCO2 y N2O, mientras que la salinidad contribuye con un 4 % en pCO2 y un 5 % en N2O. En el caso del CH4, la variabilidad que explican estos factores es menor al 1 %. El estuario del Guadalquivir emite CO2, CH4 y N2O hacia la atmósfera, con flujos más intensos en la zona interna y en verano. La variabilidad de los flujos es baja en la zona marina, pero aumenta hacia el interior debido a la intensificación de los procesos de producción de estos gases y mayores tiempos de residencia del agua. Los flujos agua-atmósfera explican el 25 %, 17 % y 16 % de la variabilidad de CO2, CH4 y N2O, respectivamente. Los flujos de CO2 varían entre -20.9 y 220.7 mmol m-2 d-1, los de CH4 entre 4.2 y 686.5 µmol m-2 d-1, y los de N2O entre -4.1 y 145.8 µmol m-2 d-1. Los sedimentos del estuario del Guadalquivir actúan como fuente de DIC (33.8 - 764.2 mmol m-2 d-1), CH4 (3.9 µmol m-2 d-1 - 18.5 mmol m-2 d-1) y N2O (1.6 - 12.3 µmol m-2 d-1) hacia la columna de agua, mostrando alta variabilidad por la heterogeneidad intrínseca del sedimento. El 54 % de los flujos de DIC proviene de la oxidación de materia orgánica, mientras que el 46 % se debe a la disolución de carbonato. Los flujos bentónicos de CH en el estuario del Guadalquivir se intensifican hacia las áreas internas tanto en verano como en invierno, y parecen estar controlados por el contenido en materia orgánica y a la intensificación de la metanogénesis a bajas salinidades. La magnitud y signo de los flujos bentónicos de N2O, nitrato y amonio sugieren nitrificación en los sedimentos en la desembocadura mientras que, en la zona interna, los flujos hacia el sedimento de nitrato sugieren la importancia de la desnitrificación en el sedimento. Los flujos bentónicos explican el 3 % de la variabilidad de pCO2, 17 % de CH4 y 10 % de N2O. La oxidación de CH4 y la producción de N2O aumentan hacia la zona interna del estuario del Guadalquivir. Las tasas de oxidación de CH4 varían entre 0.2 y 489 nmol L-1 d-1, siendo más altas en verano, especialmente en la zona interna. Las tasas de producción de N2O varían de 0.22 a 2.81 nmol L-1 d-1, siendo mayores en verano. La nitrificación parece ser el principal proceso de producción de N2O en la columna de agua, con tasas relacionadas positivamente con la utilización aparente de oxígeno, NO3- y NO2-, y negativamente con NH4 . La reactividad en la columna de agua explica aproximadamente un 20 % de la variabilidad del CH4 y N2O, mostrando contribuciones negativas para CH4 y positivas y constantes para N2O a lo largo del estuario. Los aportes laterales se han estimado como la diferencia entre la variabilidad del gas de estudio y la contribución de otros factores, e intrínsecamente recoge las incertidumbres experimentales asociadas a la cuantificación de cada proceso. Aunque se reconoce la importancia de los aportes laterales en la variabilidad de CO2, CH4 y N2O, no se puede caracterizar de manera fiable su contribución con el análisis actual. Es crucial realizar una caracterización precisa de estos aportes para entender mejor su influencia en la distribución de los gases. El estuario del Guadalquivir, con una cuenca carbonatada, facilita el transporte de carbono inorgánico hacia el Golfo de Cádiz. La alcalinidad total (TA) y el carbono inorgánico disuelto (DIC) aumentan río arriba, mientras que el calcio (Ca²) es más alto en la zona marina. Los procesos clave en la dinámica del carbono inorgánico incluyen la sulfato-reducción en la zona baja, la desnitrificación en la parte interna y la disolución de carbonatos, especialmente en invierno. El estuario tiene buena capacidad de amortiguación del pH a salinidades superiores a 10, pero la parte interna es más sensible a la acidificación. El sistema exporta alcalinidad total (3.7 ± 2.4 · 107 mol d-1), carbono inorgánico disuelto (3.5 ± 2.4 · 107 mol d-1) y Ca² (8.4 ± 4.7 · 107 mol d-1) al Golfo de Cádiz, sin afectar significativamente a su capacidad de amortiguación. La materia orgánica disuelta (DOM) en el estuario del Guadalquivir está influenciada por procesos de mezcla y reactividad. La mayor parte de la fracción fluorescente (FDOM) es de origen alóctono, predominando los componentes húmicos (84 ± 14 %) sobre los proteicos (14 ± 6 %). Los componentes húmicos se correlacionan con la salinidad, mientras que los proteicos están más relacionados con la producción autóctona y nutrientes. El transporte anual de carbono orgánico disuelto (DOC) es de 0.33 ± 0.43 Tg C año-1, principalmente de fracción húmica (87.3 ± 3.3 %). El bajo transporte de DOC, con relación al tamaño del estuario, se debe a la regulación del caudal por presas, reflejando la influencia antropogénica en el ciclo del carbono en estos sistemas.

2025-01-23T00:00:00Z Casal Porras, Isabel http://hdl.handle.net/10498/36228 2025-05-01T00:05:00Z 2025-03-14T00:00:00Z

Carbon dynamics in coastal vegetated communities: evaluation of anthropogenic impacts, chemical characterization of dissolved organic matter, and its influence on blue carbon sequestration Casal Porras, Isabel Climate change (a variation in temperatures and weather patterns) is a natural phenomenon that has been accelerating since the 19th century. The rapid increase in global temperature is mainly due to the emission of large amounts of greenhouse gases, resulting from anthropogenic activities such as the burning of fossil fuels or from livestock activities. This concern was expressed globally with the Kyoto Protocol in 1997, the first international agreement aimed at committing industrialized countries to reduce greenhouse gas emissions. Since then, policies and adaptation and mitigation measures have been adopted by the different countries involved. In the Paris Agreement in 2015, a commitment was made not to exceed the pre-industrial temperature by 1.5°C, focusing strategies on reducing global greenhouse gas emissions by 85%. In addition, one of the most innovative mitigation measures of this agreement was the possibility of capturing and removing carbon through natural ecosystems. In this context, coastal vegetated communities have been noted for their fundamental role in sequestering and storing carbon in the sediment (blue carbon), incorporating carbon dioxide (CO2) and removing it from the atmosphere in the long term. In addition, these communities play a key role in ocean carbon cycling through dissolved organic matter (DOM) fluxes where part of this organic matter feeds heterotrophic organisms (labile DOM) and another fraction contributes to the carbon pool stored in the deep ocean for thousands of years (refractory DOM). Indeed, the role of coastal vegetated ecosystems as CO2 sinks has attracted the attention of a diverse group of stakeholders including the scientific community, private sector, governments and intergovernmental bodies committed to marine conservation and climate change mitigation and adaptation. However, these communities are currently among the most threatened ecosystems in the biosphere, largely due to various anthropogenic impacts resulting in deteriorating water quality, habitat destruction due to coastal development and also, more recently, the occurrence of extreme events such as storms (e.g., DANA) and heatwaves resulting from climate change. All this produces direct and indirect impacts that affect both biomass and DOM fluxes and carbon stocks in the sediment, leading to a decrease in the capacity to store carbon in the long term, as well as to a loss of sediment carbon being released back into the atmosphere in the form of CO2. In this scenario, and from an integrated perspective, this thesis has addressed the response of certain coastal vegetated ecosystems (seagrass meadows and macroalgae) to some of the main global threats that affect them. This perspective is based on the fact that the response of these ecosystems to different impacts is far from being simple and individual, and that the final behavior must integrate the responses of each of the components that make up the community (dominant primary producer, bacterial activity in water and sediment and macrofauna, mainly). This thesis is composed of four chapters in which the direct and indirect impact of anthropogenic activities on coastal vegetated communities (seagrass meadows and macroalgae) has been estimated. In addition, and as a pioneering milestone, the DOM of the different coastal vegetated communities in the Bay of Cádiz has been chemically characterized. In chapter 1, the direct impact of the construction of several coastal infrastructures on the organic carbon stocks of the meadows of Zostera noltei in Ria Formosa (Portugal) was studied. In this study was observed that impacted meadows contained 1.5 times less organic carbon stock than non-impacted meadows. Although the area affected was relatively small (0.05-0.07 ha), the coastal infrastructure caused a significant reduction of the carbon stock, between 1.1 and 2.2 Megagrams (Mg) organic carbon, and a total loss of the carbon sequestration capacity of the impacted meadows. These results contribute to understanding the spatial variability of blue carbon stocks in coastal systems heavily impacted by urban development. Chapters 2 and 3 estimate the integrated community response (through community metabolism and dissolved organic carbon (DOC) fluxes) of the coastal vegetated communities of the Bay of Cádiz at two times of the year (winter and summer) to the chronic impact of reduced shoot density (chapter 2) and to the indirect impact of climate change such as marine heatwaves (chapter 3). In Chapter 2, changes in Cymodocea nodosa communities was observed when the shoot density was reduced to 40 and 75% of the control. The net primary production of the community decreased up to 10-fold when the shoot density was reduced from an autotrophic to a heterotrophic community. In addition, DOC fluxes (up to 5.5 times) and sediment organic matter decreased significantly. This clearly indicates that the prolonged chronic stress to which these communities have been subjected is having a negative impact on their ability to capture and store blue carbon. In chapter 3, it was observed that the heat caused an increase in net primary production in C. nodosa communities (1.9 times more than the control) and a decrease in Caulerpa prolifera communities. DOC fluxes in C. prolifera communities shifted towards negative values, i.e. from being DOC producers to DOC consumers. Furthermore, an increase in the percentage of refractory DOC was observed when the communities were subjected to a simulated heatwave, which could indicate that the increase in temperature would also increase carbon stocks. In chapter 4, the dissolved organic matter of the seagrass communities C. nodosa and Z. noltei and the macroalgal community C. prolifera were chemically characterized using a methodology based on nuclear magnetic resonance and high-resolution mass spectrometry. The chemical profile of the DOM of the different coastal vegetated communities showed that the major compounds were the highly unsaturated and aromatic ones. In addition, the DOM was characterized after a bioavailability test, which revealed the highest percentage of lability in the C. prolifera community (86%), followed by C. nodosa (81%) and Z. noltei (76%). According to van Krevelen diagrams, a significant fraction of labile compounds belonged to lipid-, peptide-, amino sugar-, and carbohydrate-like classes, while the refractory compounds mainly belonged to lignin-, tannin-, and aromatic-like classes. In conclusion, this thesis highlights the negative effects of anthropogenic impacts on coastal vegetated communities, affecting the functions and services they provide, such as climate change mitigation. The results of this thesis show not only the significant loss of biomass and blue carbon stocks in the coastal communities studied as a consequence of direct impacts (coastal infrastructures), but also that the metabolism and DOC fluxes of the community are affected by indirect (heatwaves) and chronic impacts (reduction in shoot density), leading to a decrease in the functions and services provided by these ecosystems. In addition, this thesis has contributed, for the first time, to the study of the chemical characterization of DOM from coastal vegetated communities using high-resolution techniques, revealing the chemical profile of labile and refractory DOM. Our results provide further arguments for the growing need to protect and conserve these valuable ecosystems in order to maintain the ecosystem services they provide to our planet, such as the ability to mitigate climate change.

2025-03-14T00:00:00Z Salguero Pérez, María del Mar http://hdl.handle.net/10498/36009 2025-03-29T01:06:39Z 2024-09-27T00:00:00Z

Conservación de quirópteros en el Sur de Europa Salguero Pérez, María del Mar This doctoral thesis aims to advance the knowledge about bat populations in southern Europe, with special emphasis on two aspects: their winter activity in temperate climates of southern Europe and their relationship with environmental variables, and the impact of wind energy infrastructure development on this faunal group. The expansion of renewable energy, especially wind energy, is crucial in the strategy to mitigate climate change. However, there is growing concern about the impacts this energy source may have on biodiversity, with bats being particularly sensitive, and the need to develop tools to properly assess these impacts and mitigate their effects. In this line, the results and conclusions obtained in the works composing this thesis seek to provide new information to aid in the development of bat conservation measures and to understand the mechanisms explaining bat mortality in wind farms, which in turn allows the development of practical tools that managers or researchers can use for decision-making related to future installations or restructurings of existing ones. In the first chapter, we delve into the winter activity of these animals. It is well known that bats include a hibernation period in their annual biological cycle during the coldest months. However, in regions like southern Europe, where winter temperatures are milder, bats show different ecological requirements for winter activity, which has implications for their management and conservation. In our study, we recorded winter activity of at least four species (Eptesicus isabellinus, Nyctalus leisleri, Pipistrellus pipistrellus, and Pipistrellus pygmaeus), which was directly related to the daily maximum temperature. This study provides relevant information to understand how climatic conditions influence bat winter activity, anticipating possible ecological consequences under future climate change scenarios. In the second chapter, we investigated the temporal patterns of bat mortality in wind farms in the province of Cádiz, using a dataset spanning 11 years (2009 - 2019) across 904 wind turbines in the province of Cádiz. A total of 2,858 deaths corresponding to 10 different genera were reported, although over 90% of the affected animals were individuals from the genera Pipistrellus, Eptesicus, and Nyctalus. Bat mortality occurred throughout the year, including winter months in the case of the genus Pipistrellus, although most deaths occurred during summer and autumn, especially in August and September. Mortality correlated positively with daily maximum temperature, increasing from 20°C and more markedly when the temperature exceeded 30°C. These results highlight the importance of regional projections from global climate models, with increasing maximum temperatures and milder winters, predictably increasing bat mortality in wind farms in the coming decades. In the third chapter, using the same dataset, we conducted a spatial pattern analysis of bat mortality. To do this, we applied spatial modeling techniques to our data, considering the effect of different variables related to landscape, land use, topography, and technical characteristics of the wind turbines. The results show an evident spatial aggregation of mortality, as almost half of bat deaths were concentrated in only 10% of wind farms and 8% of turbines. The developed models suggest that proximity to bodies of water was the main factor to consider when assessing the danger of a wind turbine for bats. Additionally, a larger rotor diameter also implied a higher risk of mortality. Considering current trends in wind energy development, which involve replacing current turbines with larger capacity ones and, consequently, larger dimensions than current ones, and the increasingly lower presence of water bodies accessible to these animals due to drought, this study highlights the need to analyze the location of future wind turbines beforehand to minimize their impact on this faunal group. Finally, in the last chapter of this doctoral thesis, it has been demonstrated how the use of Stochastic Dynamic Models (StDM) offers a very effective tool for making predictions about the evolution of bat mortality under different scenarios. In this context, a dynamic systems model based on the same dataset considered in the previous chapters was developed. This model considered spatiotemporal gradients encompassing environmental, meteorological, and wind farm technical variables. Scenarios were projected 10 years into the future and encompassed, for three different groups of wind farms categorized based on historical mortality data, the current situation prolonged over time, the implementation of mitigation measures, the repowering of these wind farms, and the application of mitigation measures in repowered wind farms. Simulations obtained from these scenarios emphasize the effectiveness of implementing simple mitigation measures to significantly reduce bat mortality in all considered scenarios. The implementation of such measures is especially critical in low-risk repowered wind farms, where mortality increases almost 1000% compared to the same unrepowered wind farm. Our results support that, in the current context of climate change, bat winter activity will increase in our study area, as well as their susceptibility to the impact of wind farms. It is therefore essential to develop conservation strategies that anticipate these scenarios and implement measures to mitigate the impact on bats of wind energy development, which paradoxically is proposed as an essential measure to mitigate the effects of climate change itself.

2024-09-27T00:00:00Z