6949 research outputs found
Sort by
Nurse-led interventions in prevention, health promotion and rehabilitation: a systematic review. Updating the online information resource of the Centre for Quality in Care
No full textHintergrund: Um gesundheitsfördernde, präventive und rehabilitative Interventionen für ältere Menschen auszuwählen und durchzuführen, benötigen Pflegefachpersonen Wissen zu deren Wirksamkeit. Das Zentrum für Qualität in der Pflege (ZQP) stellt ein Onlineangebot zu gesundheitsfördernden, präventiven und rehabilitativen Interventionen für ältere Menschen im ambulanten und stationären Pflegesetting bereit, das zuletzt mit empirischer Evidenz aus randomisierten kontrollierten Studien (RCT) und Systematischen Übersichtsarbeiten (SR) bis zum Jahr 2018 aktualisiert wurde.
Fragestellung: Diese systematische Übersichtsarbeit aktualisiert die Evidenzbasis des Onlineangebots des ZQP. Reviewfrage 1: Welche pflegerischen Interventionen sind in der Rehabilitation, Gesundheitsförderung und Prävention für ältere Menschen für den Einsatz in der ambulanten, teilstationären und stationären Langzeitpflege in der internationalen Literatur beschrieben? Reviewfrage 2: Wie wirksam sind die jeweiligen Interventionen?
Methode: Suche in den Datenbanken PubMed, The Cochrane Library und CINAHL im November 2022 für den Zeitraum 01.01.2019 bis 03.11.2022. Einschluss von RCT und SR von RCT in deutscher oder englischer Sprache nach vorab definierten Kriterien. Drei Autorinnen sichteten unabhängig voneinander Titel, Abstracts und Volltexte. Eine unabhängige Person wurde bei Unsicherheit hinzugezogen. Zwei Autorinnen führten unabhängig voneinander die Datenextraktion und Bewertung der methodischen Güte für jede Studie durch. RCT wurden mit dem Risk-of-Bias (RoB) Version 2 Tool und SR mit dem AMSTAR Version 2 Instrument bewertet.
Ergebnisse: Nach Sichtung von 5.082 Titeln wurden 20 Studien eingeschlossen, die primäre Endpunkte in 20 Kategorien adressieren. Positive Wirksamkeit für den primären Endpunkt beschreiben neun Studien. Drei Studien berichten heterogene Ergebnisse, acht Studien stellen keine Wirksamkeit fest. Positive Wirksamkeit zeigt sich u.a. für den Einsatz robotischer Tiere zur Förderung der Schlafqualität, der Reduktion neuropsychiatrischer Symptome in Pflegeheimen und einer Video-gestützten Erinnerungstherapie zur Reduktion von Apathie und Verbesserung der kognitiven Funktion von Menschen mit leichter Demenz. Das Risiko für Bias in den Ergebnissen ist hoch.
Schlussfolgerung: Für einzelne pflegerische Interventionsbereiche steht eine breite Auswahl von Maßnahmen zur Verfügung, die aber nicht für alle Settings oder Endpunkte statistisch signifikante Effekte erzielen und oft mit einem hohen Risiko für Bias einhergehen. Dies erschwert die Nutzung der Ergebnisse in der Praxis, da Pflegefachpersonen Fach- und Methodenkompetenz um die statistische Signifikanz und klinische Relevanz von Studienergebnissen für die eigene Praxis bewerten zu können. Onlineangebote wie das des ZQP stellen eine Möglichkeit dar, an der Versorgung beteiligten Personen empirische Evidenz systematisiert anzubieten.17
Cerium oxide nanoparticles: antioxidative potential and effects on the metabolism of glial cells
No full textCerium oxide nanoparticles (CeONPs) are considered a solid candidate for the new generation of antioxidants due to their protective potential against oxidative stress demonstrated in vitro and in vivo and their self-regeneration potential. Cellular or systemic CeONPs protection against radical-induced toxicity is based on their redox cycling capacity coupled with oxygen buffering. However, their antioxidant capacity as well as the side-effects of their application strongly depend on their synthesis and the cells targeted. In this line, previous studies have demonstrated protective effects of CeONPs against neuro-pathologies with a strong background of oxidative stress, such as Alzheimer´s disease, Parkinson´s disease or ischemia. However, despite this growing scientific evidences, the non-acute effects of CeONPs in glial cells remain a vast unexplored area of research. Therefore, it is of utmost importance to explore the novel formulations and the particular cellular interactions of CeONPs.
In the presented thesis, the coating with dimercaptosuccinate (DMSA) of commercial CeONPs was tested to obtain a colloidally stable DMSA-CeONPs dispersion. These nanoparticles (NPs) were thoroughly analyzed for their physicochemical properties such as size, shape and zeta potential. In addition, DMSA-CeONPs were fluorescence functionalized with the Oregon Green dye (OG), allowing the microscopical observation of their time- and temperature-dependent cellular uptake by rat C6 glioma cells and astrocytes. Cell viability and the effects on glucose metabolism was also investigated in astrocytes after incubation with DMSA-CeONPs. Different experimental conditions revealed that astrocytes remained viable over time and accumulated cerium in a concentration-dependent manner. However, the glycolytic flux was stimulated and thus, the extracellular concentration of lactate was significantly increased in astrocytes treated with DMSA-CeONPs. Comparison to astrocytes exposed to ionic cerium showed that the stimulation of the glycolytic flux depends on the presence of cerium, independently of the form in which it was presented. However, the intracellular cerium accumulation was significantly enhanced after exposure to DMSA-CeONPs compared to cells treated with ionic cerium. Incubations with hypoxia inducible 1 α (Hif-1α) stabilizers revealed that such stimulation of the glycolytic flux showed similarities to the stimulation observed when astrocytes were incubated with DMSA-CeONPs and therefore, it is concluded that cerium may interfere with the intracellular oxygen availability.
Two different approaches were taken to assess the potential antioxidative capacity of DMSA-CeONPs against reactive oxygen species (ROS): 1) the removal of exogenous H2O2 and the scavenging of cellularly formed superoxide was tested extracellularly and 2) intracellularly, by pre-incubating glial cells with these DMSA-CeONPs and then incubating them in the presence of exogenous H2O2 or under the cellular formation of superoxide. The results demonstrate that DMSA-CeONPs have only a limited extracellular ROS scavenging capacity. Internalized DMSA-CeONPs did not act as antioxidants in glial cells, nor did they show catalyst activities under the conditions tested.
In conclusion, the coating and fluorescence functionalization of CeONPs presented in this thesis are suitable tools to study the uptake, intracellular fate and accumulation in glial cells. However, these NPs cannot be applied as antioxidants due to their limited ROS scavenging capacities. DMSA-CeONPs did not affect the viability of glial cells but altered glucose metabolism, most likely via Hif-1α stabilization. In this line, this thesis highlights the importance of the investigation of the cellular effects beyond cell viability and under non-pathological conditions of CeONPs treatments
Sustainable offshore wind farm decommissioning - Multi-criteria decision analysis for the assessment of sustainable decommissioning alternatives
No full textDie aktuellen ehrgeizigen Entwicklungspläne für Windenergie erfordern die Errichtung sehr vieler Windturbinen in der Nordsee. Da die operative Lebensdauer dieser Windturbinen endlich ist, wird der Rückbau eine der Kernfragen des nachhaltigen Energiemanagements. Zurzeit mangelt es jedoch sowohl an praktischen Rückbauerfahrungen als auch an einem fundierten Verständnis für Chancen und Limitationen der unterschiedlichen Rückbaualternativen. Mögliche Rückbaualternativen berücksichtigen zum Beispiel verschiedene Rückbautechnologien, logistische Konzepte oder teilweisen Rückbau. Ökonomische, Umweltbezogene oder soziale Auswirkungen dieser Rückbaualternativen sind bisher nicht vollständig untersucht. Aufgrund der sehr geringen Erfahrungen und Kenntnissen ist der Rückbau von Offshore-Windparks mit einer großen Unsicherheit verbunden. Diese Arbeit hat zum Ziel, Entscheidungsträger zu befähigen qualifizierte und nachvollziehbare Entscheidungen für einen nachhaltigen Rückbau von Offshore-Windparks zu treffen. Multikritierelle Entscheidungsanalysen wurden angewandt um ausgewählte Rückbaualternativen hinsichtlich ihrer Nachhaltigkeit, d.h. ihrer Treibhausgasemissionen, Ressourceneffizienz, Kosten, Gefährdungen und Auswirkungen auf die benthische Biodiversität, unter Berücksichtigung der einhergehenden Unsicherheiten zu bewerten und zu vergleichen.
Aufgrund der mangelnden Erfahrungen wurde als erstes eine Wissensbasis entwickelt, auf welcher alle nachfolgenden Untersuchungen basierten. Diese Wissensbasis umfasst eine Stakeholder-Analyse (Publikation I), die Ausarbeitung der Rückbaualternativen (Publikationen V and VIII), die Untersuchen der rechtlichen Anforderungen (Publikation II) und Entwicklung eines Referenz-Offshore-Windparks als Fallbeispiel (Publikation III). Anschließend wurde ein Konzept entworfen für die Integration von Stakeholder-, Nachhaltigkeits- und Prozessansatz (Publikation IV), welches als Basis für die multikriterielle Entscheidungsanalyse diente. Unterschiedliche Methoden der multikritierellen Entscheidungsanalysen wurden angewendet (Nutzwertanalyse in Publikation VIII und fuzzy SAW, fuzzy TOPSIS sowie fuzzy VIKOR in Publikation IX) und die Ergebnisse wurden zwecks des Vergleichs der Methoden und der Rückbaualternativen interpretiert. Um die Auswirkungen der Gewichtung der Entscheidungskriterien auf die Rangfolge der Rückbaualternativen zu untersuchen wurde eine Auswertung mit übergewichteten Kriterien durchgeführt (Publikation X).
Diese Studie zeigt, wie multikriterielle Entscheidungsanalysen eingesetzt werden können, um die Nachhaltigkeit von Rückbaualternativen von Offshore-Windparks zu untersuchen. Obwohl alle einsetzten Methoden geeignet waren, berücksichtigten nur die fuzzy Multikriterielle Entscheidungsanalsysemethoden die assoziierte Unsicherheit. Obwohl die Methoden unter bestimmten Bedingungen unterschiedliche auf kleine Abweichungen in den fuzzy rating reagierten, haben sie größtenteils ähnliche Rangfolgen der Rückbaualternativen hervorgebracht. Alternativen des teilweisen Rückbaus, bei denen Gründungsstrukturen oberhalb des Meeresbodens geschnitten werden, der Kolkschutz und/oder die Innerparkverkabelung zurückbleibt, erhielten zumeist hohe Range. Sie sind mit geringen Kosten und Treibhausgasemissionen verbunden und sind vorteilhaft für die benthische Biodiversität. Feeder-Konzepte wiederum gehen mit hohen Kosten, Treibhausgasemissionen und Gefährdungen einher, da sie zusätzliche Schiffe und Überfahrten sowie mehrere Hebevorgänge erfordern. Sie erhielten somit am häufigsten die niedrigsten Ränge.
Nachhaltigkeit, also die Verfolgung umweltbezogener, wirtschaftlicher und sozialer Ziele, wurde durch die fünf Entscheidungskriterien in der multikriteriellen Entscheidungsanalyse berücksichtigt. Diese Analyse zeigt, dass vier der Entscheidungskriterien, nämlich Kosten, Treibhausgasemissionen, Biodiversität und Gefährdungen, geeignete Kriterien sind, um die Rückbaualternativen für Offshore-Windparks zu bewerten. Das Entscheidungskriterium Ressourceneffizient jedoch ist nicht geeignet, um teilweise Rückbaualternativen einzuschätzen, da die Menge und die Art der im Meer verbleibenden Materialien nicht angemessen berücksichtigt werden.
Eine grundlegende Herausforderung dieser Analyse war die schwache Daten- und Wissensbasis. Aufgrund mangelnder Erfahrungen wurden Rückbauprozesse basierend auf der Einschätzung von Experten entwickelt. Daten für die Bewertung der Rückbaualternativen unterlagen häufig der Geheimhaltung, z.B. der Treibstoffverbrauch der Schiffe, oder sie existierten nicht, so wie z.B. Umweltmonitoring-Daten. Um den Rückbau von Offshore-Windparks besser untersuchen zu können, sollten künftig solche Daten und Informationen erhoben werden
Expanding speech interaction for domestic activities
No full textDue to technological advancements, communicating with computer systems using natural language has become a common phenomenon. Speech-based systems have become widely popular among people in everyday activities due to the intuitive nature of their interaction. Speech interaction inherently encompasses a social component as it reflects the fundamental human capacity for communication and enables interpersonal engagement through verbal exchange.This makes speech interaction with computers an essential topic of research in the field of human-computer interaction. Along with the development of speech-based systems, users' demands and expectations from such systems grow. Despite the popularity of speech interaction, designing a gratifying experience for users interacting with such systems remains challenging. This can be attributed partly to technical constraints, such as challenges with speech recognition, and partly to experiential limitations where these systems fail to meet users' needs and expectations as communication partners.
This dissertation explores human-agent speech interaction in domestic activities through a series of user studies and interviews.The primary focus lies in the practical application of speech technology for everyday activities, particularly within two application domains of homes and video games, to identify factors contributing to successful speech interaction. Drawing inspiration from communication and human-computer interaction models, a novel interaction model is introduced to provide a more nuanced understanding of the dynamics in human-agent speech interaction.
Different dimensions of speech systems are analyzed, including the utility and efficacy of speech systems, diverse representations of speech agents, and the style in which these systems interact with users. By examining users' needs and addressing current issues, designing new features to enhance existing systems, and proactively anticipating potential future challenges, this work takes a comprehensive approach, encompassing a retrospective, current, and future outlook. The aim is to provide a broad perspective on designing speech systems, offering relevant design factors and recommendations to achieve a higher user experience with such systems.
This thesis contributes to the fields of human-computer interaction, voice user interfaces, game user research, and user experience design within both academia and industry
Dirigenten der Erlebnisgesellschaft. Berufsfeld Eventmanagement: Rahmenbedingungen, Kompetenzen und Perspektiven
No full textDie vorliegende Berufsfeldstudie beruht auf 22 qualitativen Interviews mit Eventmanagern und Eventmanagerinnen. Im Mittelpunkt stehen die Aufgaben und die Kompetenzen, die Beschäftige in diesem Feld benötigen. Die mit Unterstützung der Hochschule Bremen durchgeführte Studie gibt einen Einblick in die Sichtweisen der Akteure und sollte auch dazu dienen das Studienangebot für eine Tätigkeit im Eventsektor zu qualifizieren
Allen Ginsberg und die Beat Generation – Lyrisches Opponieren, Protestieren und Widersprechen
No full textPublikation der U Bremen und U Wien internationalen Studierendenkonferenz »Debattieren, Opponieren, Protestieren – Interdisziplinäre Perspektiven auf sprachliche Praktiken des Widersprechens« 2023.10811
Spatio-temporal evaluation of green hydrogen production in Ecuador
No full textThis study evaluates the techno-economic conditions of green hydrogen production based on the combined operation of geographically-dispersed and complementary wind and solar power farms in Ecuador. Representative sites with high potential of wind and solar resources are used for the calculations. The hourly meteorological data of these sites is used to simulate the power output of solar photovoltaic (PV) and wind power farms. Then, based on the renewable power output and the associated generation cost, the production of
hydrogen is simulated using an electrolysis optimization model. Using a set of indicators, we evaluate the results of three combinations of different PV and wind farms to identify the relation between the renewable power and the hydrogen production and cost. Results show that all combinations produce green hydrogen at a levelized cost of hydrogen (LCOH) of less than US$4 per kg. It is found that the LCOH can be related to the hourly variation
and the cost of the renewable generation. This means that the higher the stability of the renewable power output, the lower the simulated LCOH. We will use the findings of this study to evaluate the performance with more combinations of PV and wind power farms in a future work.23
Late Quaternary relative sea-level changes and reef development in the Coral Triangle recorded by coral reef terraces
No full textCoral reef terraces (CRTs), usually observed along tropical coastal areas and are formed through repeated bioconstructional and erosional processes, are useful bio-geomorphological indicators of relative sea-level (RSL) changes in the past. Often considered as a process analog for predicted future changes for a warmer world is the Last Interglacial (LIG, also Marine Isotope Stage (MIS) 5e) and the analysis of sea-level indicators during this period can give us insights about potential drivers of local, regional, and global sea-level changes in the past. In this work, a standardized database of LIG sea-level indicators in Southeast Asia was produced. Overall, 43 unique RSL proxies (42 CRTs and one tidal notch), which were correlated to 134 dated samples, were compiled and data gaps in the region were recognized. Following this, a sequence of CRTs situated at the northern apex of the Coral Triangle was investigated in detail to understand RSL changes and reef development in the region during the late Quaternary. The Cape Bolinao CRTs in west Luzon, Philippines were examined using high-resolution morphological analysis and reef modelling coupled with new stratigraphic and geochronologic data. Distinct levels of CRTs (Terrace I to Terrace IX) were delineated with the lowest terrace (TI measured ~4 m above mean sea level (amsl)) dated mid-Holocene. Using best-fitting reef simulations that replicate the present-day morphology of the Cape Bolinao CRTs, the highest terrace (TIX at ~155 m amsl) was identified to form during MIS 5e. A morpho-chronological framework for the development of the Cape Bolinao CRTs is hereby proposed. In this framework, an extensive Late Pleistocene reef platform or table reef developed on top of a gently-dipping substrate and continuous uplift superimposed on a changing sea level led to the emergence of this table reef followed by the formation of fringing reefs (corresponding to lower reef terraces) along its slope. A parametric study was also conducted to examine the different parameters that control CRT architecture and morphogenesis in the region. Numerical reef simulations reveal that vertical land movement (uplift) is the principal driver of relative sea-level changes in western Luzon, being the main control of the architecture of the Cape Bolinao CRTs. The reef simulations suggest high uplift rates (1.17 mm/yr to 1.2 mm/yr) during the Late Pleistocene which is attributed to regional tectonics (i.e., subduction of the Scarborough Seamount Chain beneath Luzon Island). Other parameters that influence the CRT architecture in the study area include the slope of the basement, erosion rate, and reef growth rate. Accommodation space and antecedent topography also modulate the formation of CRTs especially in a rapidly uplifting region. Lastly, this study affirms that CRTs are a continuous record of sea-level oscillations superimposed on local forcings such as vertical land motion, bedrock topography, erosion rate, and reef growth rate
Strain selection and optimization of Ulva spp. for land-based recirculating cultivation systems
No full textUlva species are intertidal macroalgae spread worldwide, known for their biochemical
composition (e.g., ulvan) that grants them interesting properties to explore in sectors
such as food, feed, cosmetics, pharmaceutical, and bioplastics. They are known for their high growth rates, bioremediation capacity, and plasticity, which can be associated with the formation of harmful green tides. Nevertheless, Ulva is considered a good candidate to cultivate on a large scale. Recirculating aquaculture systems (RAS) are well established systems for the cultivation of fish, shrimp, and other aquatic species and can be operated as a partly flow-through or even complete closed system. Thus, allowing the cultivation of non-native species in land-based recirculating systems without introducingthese species in the wild. Land-based systems present high costs and Ulva cultivation still presents several bottlenecks that limit the possibility of a profitable scale-up process (e.g., variation in biochemical composition, different adjustments, and responses to the environment). The works presented in this dissertation aimed to select Ulva strains for later cultivation in a RAS with artificial seawater and optimize them for their later use as the main constituent of food packaging. Four strains of Ulva from two geographical origins (Ulva flexuosa, Ulva lacinulata, from the Mediterranean Sea, and U. lacinulata and Ulva linza from the NE-Atlantic Ocean) were tested and compared for their robustness and capacity to grow in high temperatures and low salinities.
To test the importance of strain selection for Ulva cultivation, eco-physiological
experiments were conducted. The relative growth rates (RGR) of different Ulva species
and strains under different salinity (Publication I) and temperature conditions were
tested (Chapter 6). Strains that presented RGRs below a 7 % day-1 RGR threshold, were considered not ideal. Ulva linza and both strains of U. lacinulata presented elevated growth rates in the temperature range tested. In the salinity experiment (Publication I) it was estimated that RGRs of the adult U. lacinulata strains would be above the 7 % day-1 threshold, even if salinity was reduced to 12 PSU. For this reason, U. lacinulata strains, particularly the NE-Atlantic strain, were considered potential candidates for vegetative cultivation in a RAS under lower salinity settings. To test the same salinity treatments as a potential method for strain optimization, the antioxidant activity (AA) from the NE-Atlantic U. lacinulata was measured for 10 days. AA showed a tendency to increase in the lowest and highest treatments (10 and 30 PSU), suggesting that biomass quality can be increased by further reducing the salinity for a short period before harvesting. Not all the species tested were good candidates for the system, thus corroborating the importance of strain selection before cultivation. Cultivating U.
lacinulata strains at lower salinities could amount to a reduction in the costs for the
system and an increase in biomass quality. High-quality biomass can increase the profitability of the system by enabling the biomass to be sold for a higher price. Antioxidant activity was considered a necessary property in the strains, as high levels of antioxidants can increase food’s shelf-life. The effect of irradiance on the AA of the two U. lacinulata strains was evaluated (Publication II). Both strains were grown under a saturating irradiance treatment for 5 days and their AA and photosynthetic efficiency were evaluated. Both strains showed the capacity to adapt to the saturating irradiance, but only the NE-Atlantic strain had a significant increase in AA under the saturating irradiance treatment. Thus, suggesting that a significant light increase can improve the quality of the biomass. The lack of differences found in the AA of the Mediterranean strain between the control group and the saturating treatment indicates that light dose (kept the same between the treatments) also plays a role in determining the AA of a strain. The different results from both strains corroborate once more the importance of strain selection and optimization.
The NE-Atlantic Ulva lacinulata, often and spontaneously degraded without signs of
fertility, and attempts at inducing reproduction were unsuccessful. As a first attempt to
overcome these limitations, a successful protoplast isolation method was developed
based on the methods reported in the literature. Two eco-physiological pre-treatments
(light and salinity) were tested to be used before the isolation of protoplasts to reduce
the costs of the isolation method. Only the 40 PSU pre-treatment reduced the cell wall
of Ulva-1 (Chapter 6). To understand the constant biomass loss, the degradation process of the NE-Atlantic U. lacinulata was followed (Publication III). The degradation
caused the removal of the cell wall and the release of protoplasts into the water that were able to regenerate and regrow. Protoplasts grew into three morphologies (cell masses, unattached discs, and unattached germlings), two of which very soon after regeneration and germination, released gametes into the water. A similar experiment was performed with wild material from Ulva compressa. This species became fertile and released swarmers, but a portion of the cells released were found to be protoplasts. These findings suggest that Ulva species have an unexplored asexual reproduction strategy. This is the first time that the natural formation of protoplast has been reported in Ulva species as a method of reproduction. This knowledge can help us understand Ulva species and how to deal with future degradation events that limit Ulva cultivation
Exploring fluid flow in the Gulf of Cadiz: from mud volcanoes to transform faults
No full textCold seeps have been identified globally spanning diverse geologic settings and represent important seafloor manifestations of material transfer between geosphere and hydrosphere. The material extrusions give rise to seafloor topographic features that are indicative of focused release of overpressure, fluids, and, in the case of mud volcanoes, sediments. As emitted fluids have experienced various diagenetic processes at depth, their expulsion may play a significant role in global biogeochemical cycles. To gain insights into fluid circulation within cold seep systems, it is imperative to acquire a comprehensive understanding of the fluids’ origin and the geochemical processes that exert an influence on their composition.
In this dissertation, the plate boundary region between Africa and Eurasia is studied to identify cold seeps of various origin. The sites investigated span from the Gulf of Cadiz in the west, geodynamically dominated by transform faulting, to the Hellenic subduction zone to the East, a mature subduction system with reverse faulting. Seeping features that can be directly observed at or near the seabed in these regions are manifold, and mud volcanoes (MVs) are the most prominent among them. The first and second manuscripts in this study investigate several MVs in the Gulf of Cadiz, aiming to enhance the understanding of MVs’ morphological characteristics, deep-seated fluid migrations, and salinity patterns. A presentation of new discoveries about mud volcanism through the Gulf of Cadiz accretionary prisms is reported in the first manuscript, covering their morphologies, physical properties and lithological changes in mud breccias, and fluid compositions. The six MVs investigated (already known MVs Yuma, Ginsburg and Meknes and newly discovered MVs R2, D2 and Funky Monkey) are located along different strike-slip fault segments. While two of them are textbook examples of inactive mud domes, the other four MVs attest recent activity in different evolution stages. At active seepage sites, we traced back the origin of venting fluids to clay mineral dehydration and identified pronounced crustal influence and less intense pore water freshening present in the deeper MVs located close to major strike-slip faults (Funky Monkey MV). The second manuscript presents in turn a deeper understanding of fluid circulation within “the MV system” to investigate the relationship between evolving surface characteristics and dynamic subsurface conditions. Two MVs situated in the Gulf of Cadiz (Yuma, Ginsburg) and one MV in the Mediterranean Ridge (Milano) have been studied, which show striking differences in fluid composition between their summit and moat/rim. Through the utilization of fluid geochemistry, pore water modeling, and high-resolution seismic data, this study has identified not only the widely-known central conduits within the MV system, expelling freshening fluids due to clay mineral dehydration, but also the rim-related fluid pathways actively emitting saline fluids resulting from the leaching of evaporites. The chemical and fluid fluxes of 5 MVs have been analyzed and related to the MVs life-cycle (depletion and quiescence periods). The results indicate the involvement of additional (shallow) fluid sources during a later evolutionary stage, particularly when the moat is being developed. Based on the calculated flow rates at the moat area, in the case of the Ginsburg MV, this newly described rim-related fluid circulation significantly contributes to fluid cycling in MVs, especially during long intervals of inactivity. Although this research is confined to the Gulf of Cadiz and the Mediterranean Ridge, the rim-related fluid circulation may have global implications. This enhances our understanding of the coverage and timespan of quiescent fluid seeping and its impact on the global fluid and methane budgets, which indicates the need for further efforts to improve the estimates including not only the summit areas of MVs but also the peripheric systems of these complexes.
To gain a more comprehensive insight into fluid seepage in the Gulf of Cadiz, the third manuscript shifts the focus from MVs to transform faults. Its objective is to define the contribution of oceanic transform faults as important settings for the circulation of deep-sourced fluid flow and their influence on global mass balances. The fault fluids are sampled from two different pull-apart basins on the dextral strike-slip faults, as known as the South West Iberian Margin (SWIM) faults defining the Africa-Eurasia plate boundary in the Gulf of Cadiz. Chemical and isotopic composition analysis has been conducted on fault fluids and compared with those from nearby tectonic-controlled cold seep sites including MVs and pockmarks. In contrast to the prevalent freshening signals (Cl depletion) observed in the MV fluids, the geochemical results show a missing signal from clay mineral dehydration in the fault fluids, suggesting an almost absent connection with terrigenous sediments. The geochemical composition of fault fluids is, instead, characterized by ⅰ) considerably high Na and Cl concentrations attributed to intensely interaction with Triassic evaporites at depth; and ⅱ) strong enrichment of less radiogenic Sr, compared to present-day seawater values. When related to pure Triassic evaporitic fluids, the relatively radiogenic 87Sr/86Sr ratios in the fault fluids hint a potential contribution from continental crustal fluids, with modeling indicating up to 22%. This provides insights into the impact of transform faults in focusing crustal signals from the depths, thereby advancing our understanding of the deep hydrologic cycle within transform-type plate boundaries.
This thesis offers insights into fluid flow dynamics at seep sites in the Gulf of Cadiz plus a comparison to analogue processes further east across the Mediterranean Ridge. Through the investigation of fluids in mud volcanoes and fault systems, this study reveals: i) their relationship and different mechanisms in upward-channeling deep fluids; ii) the signature of fluids and the potential origin from crustal basement; and iii) the significant role these fluid systems play in influencing fluid cycling and global element budgets