3,850 research outputs found

    An Evaluation of the risks to food safety and shellfish farming in Great Britain,posed by marine biotoxins from, current and future emerging, marine microalgal species

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    Harmful marine microalgae are a global concern, impacting human and ecosystem health as well as having socioeconomic impacts for coastal communities. The changing world climate has an impact on marine organisms including the harmful algal species. These changes will have impacts on species already present in a nations waters whilst also influencing the emergence of novel species. This is assessed here, in part, with regards to Great Britain (GB). This thesis explores the current extent of a harmful species, Alexandrium minutum, globally and in the South of GB. This shows that A. minutum occurs widely across the globe with different populations possessing varying toxin profiles. Populations from GB geographically neighbouring areas share similar toxin profiles. Within the South of GB, the current extent of A. minutum appears patchy, with evidence gathered by toxin profile analysis but successful germinations of vegetative cells from field samples proving unsuccessful. Experimental work determined a mechanism for the use of chemotaxonomy to differentiate the source of shellfish intoxications, allowing for separation of two key GB saxitoxin producers, A. minutum and Alexandrium catenella. This technique could enhance routine monitoring data with little additional cost. Assessment of harmful microalgal taxa considered as non-native species (NNS) to GB suggested that several species could pose a risk of future successful invasion of GB coastal waters, within the next 30 years. This was principally based on the environmental tolerances of NNS. If established the impacts which NNS could impose on GB include similar impacts to native harmful species as well as a higher risk of environmental damage. Experimental work with a high-risk potential invasive species, Ostreopsis cf. ovata, indicated that this impact could be acute, with rapid mortalities observed in exposed naĂŻve GB mussels. Taken together this body of work shows the validity of chemotaxonomic assessment of toxin profiles as an additional tool for the tracking of harmful microalgal species as well as proactively assessing the risk and impacts which climate change might have for the future impacts of harmful marine microalgal species around GB

    Novel Acoustic Methods for Directly Monitoring Seabed Sediment Transport, Geohazards & Scour

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    In the natural environment, sediment transport processes can pose significant hazards to marine infrastructure, such as offshore wind turbines or seabed cables that carry both power onshore as well as carrying over 99% of global data. These processes are often extremely challenging to measure directly because sensors can be easily damaged by the processes themselves. It would, therefore, be highly advantageous to remotely sense and quantify sediment transport via sensors that are located outside the region of sediment transport. One way to do this is via sensors higher in the water column that detect acoustic signals emitted by sediment transport processes closer to the bed. Previous work such as Wren et al. (2015), Marineau et al. (2016), and Le Guern et al. (2021) have started to develop passive acoustic methods to record signals from sediment transport, using tools such as hydrophones and acoustic Doppler current profilers (ADCPs). Normally, ADCPs actively emit their own acoustic pulses, and their reflections are used to monitor flow velocities and concentrations. However, with modification to extend their listening times, ADCP’s can also be used to passively record acoustic signals emitted by sediment transport processes. Thus far, the potential of these passive acoustic methods have not been fully developed, and the fundamental controls that determine the type of acoustic signals produced are not yet fully understood. This PhD sought to understand what controls the nature (frequencies, strength etc) of these signals and, thus, what they can tell us about sediment transport processes (Thorne, 1985,1986,1990,2014; Rigby et al. 2016). It aims to do this using a combination of laboratory experiments (Chapter 2) and detailed fieldwork (Chapters 3 and 4) using acoustic signals passively emitted by sediment flows. In addition, the thesis includes work testing the use of active acoustic methods to monitor sediment transport processes within the natural environment, specifically seabed sediment flows (called turbidity currents) (Chapter 5). Results from this thesis found a general relationship between the strength of self-generated noise and flow speed in some types of sediment flows (Chapters 2, 3 and 4). However, the strength of this relationship changes depending on the frequency and details of the environment investigated. Field data from the Río Paraná (Chapter 3) suggested no relationship between bedload flux and acoustic signal strength, nor between acoustic signal strength and friction velocity. This is unexpected because previous research by Sime et al. (2007), Hossein and Rennie (2009), Hatcher (2017), Hay et al. (2021) and Le Guern et al. (2021) proposed links between flow speed (and bed shear stress and bedload transport) and passively detected noise strength. Passive acoustic signals generated by turbidity currents were used to monitor these flows in a set of submarine canyons, which were Bute Inlet (Canada), Monterey Canyon (offshore California), and the Congo Canyon (offshore West Africa) (Chapter 4). Noticeable variations in the level of passively detected noise between these three field sites were observed. These variations are thought to be related to the main sediment grain size present within each canyon, with lower noise being detected with an increasing mud content of the seabed. In addition, differences in noise down submarine canyons suggest that flow processes and concentration could be controlling the level of sediment-generated noise, with implications of flow field dynamics. Chapter 5 uses one of the most detailed (near-daily) series of multibeam swath bathymetry surveys yet collected, which come from within Bute Inlet, Canada, in September 2022. This unusual set of field observations is used to understand the relationship between flow evolution and the initiation mechanism of turbidity currents. For example, the Bute Inlet study supports the findings from Hizzett et al. (2018) that there is no link between the initiation mechanism and runout distance of a turbidity current. Further research is needed to improve understanding of the controls on acoustic signals in the natural environment, and to also improve our ability to use acoustic signals to monitor sediment transport in a wider range of environments, such as around offshore wind farms

    Displacement and the Humanities: Manifestos from the Ancient to the Present

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    This is the final version. Available on open access from MDPI via the DOI in this recordThis is a reprint of articles from the Special Issue published online in the open access journal Humanities (ISSN 2076-0787) (available at: https://www.mdpi.com/journal/humanities/special_issues/Manifestos Ancient Present)This volume brings together the work of practitioners, communities, artists and other researchers from multiple disciplines. Seeking to provoke a discourse around displacement within and beyond the field of Humanities, it positions historical cases and debates, some reaching into the ancient past, within diverse geo-chronological contexts and current world urgencies. In adopting an innovative dialogic structure, between practitioners on the ground - from architects and urban planners to artists - and academics working across subject areas, the volume is a proposition to: remap priorities for current research agendas; open up disciplines, critically analysing their approaches; address the socio-political responsibilities that we have as scholars and practitioners; and provide an alternative site of discourse for contemporary concerns about displacement. Ultimately, this volume aims to provoke future work and collaborations - hence, manifestos - not only in the historical and literary fields, but wider research concerned with human mobility and the challenges confronting people who are out of place of rights, protection and belonging

    Determining the ages of sub-fossil cetacean remains, found in the Carse of Stirling, Scotland

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    During the 19th and early 20th centuries, sub-fossil cetacean remains were often discovered in the Firth of Forth, Central Scotland. These bones and skeletons of "Whales" were excavated from a recent, estuarine deposit (named "carse clay") and, within the biological and geological sciences, were not judged to be important. That palaeontological evidence is re-evaluated in this thesis. These cetacean remains have been preserved in an unusual marine environment and form an exceptional fossil assemblage, with almost no geological precedents. Why is it there? Whatever caused exceptional preservation in the Firth of Forth in the early Holocene (c. 9.5 – 2.5ka cal BP) can be best identified with chronological data. The ages of six sets of cetacean remains are determined in this thesis, by radiocarbon dating and stratigraphic inference. To reconstruct where a bone or skeleton had been found in the "carse" and then to identify any surviving elements in modern museum collections, archaic textual sources had to be thoroughly investigated. Radiocarbon dates from marine organisms require correction for "reservoir effects" and those applicable to mysticete cetaceans require careful consideration. The absolute dating evidence shows that no two "Whales" are the same age and that each died, and was then preserved, over the period 9.5 – 7.0ka cal BP. Therefore, a "disaster" (e.g. tsunami) or mass mortality is unlikely to have caused these remains to accumulate. A combination of physical processes and stable environmental conditions are more likely responsible, and might still permit exceptional preservation in the modern Firth of Forth. Actualistic experiment (observing if, and how, a cetacean carcass is preserved or dispersed on a modern tidal foreshore) would allow further insights into this cryptic palaeontological assemblage

    IoT Transmission Technologies for Distributed Measurement Systems in Critical Environments

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    Distributed measurement systems are spread in the most diverse application scenarios, and Internet of Things (IoT) transmission equipment is usually the enabling technologies for such measurement systems that need to feature wireless connectivity to ensure pervasiveness. Because wireless measurement systems have been deployed for the last years even in critical environments, assessing transmission technologies performances in such contexts is fundamental. Indeed, they are the most challenging ones for wireless data transmission due to their intrinsic attenuation capabilities. Several scenarios in which measurement systems can be deployed are analysed. Firstly, marine contexts are treated by considering above-the-sea wireless links. Such setting can be experienced in whichever application requiring remote monitoring of facilities and assets that are offshore installed. Some instances are offshore sea farming plants, or remote video monitoring systems installed on seamark buoys. Secondly, wireless communications taking place from the underground to the aboveground are covered. This scenario is typical of precision agriculture applications, where the accurate measurement of underground physical parameters is needed to be remotely sent to optimise crops reducing the wastefulness of fundamental resources (e.g., irrigation water). Thirdly, wireless communications occurring from the underwater to the abovewater are addressed. Such situation is inevitable for all those infrastructures monitoring conservation status of underwater species like algae, seaweeds and reef. Then, wireless links happening traversing metal surfaces and structures are tackled. Such context is commonly encountered in asset tracking and monitoring (e.g., containers), or in smart metering applications (e.g., utility meters). Lastly, sundry harsh environments that are typical of industrial monitoring (e.g., vibrating machineries, harsh temperature and humidity rooms, corrosive atmospheres) are tested to validate pervasive measurement infrastructures even in such contexts that are usually experienced in Industrial Internet of Things (IIoT) applications. The performances of wireless measurement systems in such scenarios are tested by sorting out ad-hoc measurement campaigns. Finally, IoT measurement infrastructures respectively deployed in above-the-sea and underground-to-aboveground settings are described to provide real applications in which such facilities can be effectively installed. Nonetheless, the aforementioned application scenarios are only some amid their sundry variety. Indeed, nowadays distributed pervasive measurement systems have to be thought in a broad way, resulting in countless instances: predictive maintenance, smart healthcare, smart cities, industrial monitoring, or smart agriculture, etc. This Thesis aims at showing distributed measurement systems in critical environments to set up pervasive monitoring infrastructures that are enabled by IoT transmission technologies. At first, they are presented, and then the harsh environments are introduced, along with the relative theoretical analysis modelling path loss in such conditions. It must be underlined that this Thesis aims neither at finding better path loss models with respect to the existing ones, nor at improving them. Indeed, path loss models are exploited as they are, in order to derive estimates of losses to understand the effectiveness of the deployed infrastructure. In fact, some transmission tests in those contexts are described, along with providing examples of these types of applications in the field, showing the measurement infrastructures and the relative critical environments serving as deployment sites. The scientific relevance of this Thesis is evident since, at the moment, the literature lacks a comparative study like this, showing both transmission performances in critical environments, and the deployment of real IoT distributed wireless measurement systems in such contexts

    Automated riverbed composition analysis using deep learning on underwater images

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    The sediment of alluvial riverbeds plays a significant role in river systems both in engineering and natural processes. However, the sediment composition can show high spatial and temporal heterogeneity, even on river-reach scale, making it difficult to representatively sample and assess. Conventional sampling methods are inadequate and time-consuming for effectively capturing the variability of bed surface texture in these situations. In this study, we overcome this issue by adopting an image-based deep-learning (DL) algorithm. The algorithm was trained to recognise the main sediment classes in videos that were taken along cross sections underwater in the Danube. A total of 27 riverbed samples were collected and analysed for validation. The introduced DL-based method is fast, i.e. the videos of 300–400 m long sections can be analysed within minutes with continuous spatial sampling distribution (i.e. the whole riverbed along the path is mapped with images in ca. 0.3–1 m2 overlapping windows). The quality of the trained algorithm was evaluated (i) mathematically by dividing the annotated images into test and validation sets and also via (ii) intercomparison with other direct (sieving of physical samples) and indirect sampling methods (wavelet-based image processing of the riverbed images), focusing on the percentages of the detected sediment fractions. For the final evaluation, the sieving analysis of the collected physical samples were considered the ground truth. After correcting for samples affected by bed armouring, comparison of the DL approach with 14 physical samples yielded a mean classification error of 4.5 %. In addition, based upon the visual evaluation of the footage, the spatial trend in the fraction changes was also well captured along the cross sections. Suggestions for performing proper field measurements are also given; furthermore, possibilities for combining the algorithm with other techniques are highlighted, briefly showcasing the multi-purpose nature of underwater videos for hydromorphological assessment.</p

    Advances and Applications of DSmT for Information Fusion. Collected Works, Volume 5

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    This ïŹfth volume on Advances and Applications of DSmT for Information Fusion collects theoretical and applied contributions of researchers working in different ïŹelds of applications and in mathematics, and is available in open-access. The collected contributions of this volume have either been published or presented after disseminating the fourth volume in 2015 in international conferences, seminars, workshops and journals, or they are new. The contributions of each part of this volume are chronologically ordered. First Part of this book presents some theoretical advances on DSmT, dealing mainly with modiïŹed Proportional ConïŹ‚ict Redistribution Rules (PCR) of combination with degree of intersection, coarsening techniques, interval calculus for PCR thanks to set inversion via interval analysis (SIVIA), rough set classiïŹers, canonical decomposition of dichotomous belief functions, fast PCR fusion, fast inter-criteria analysis with PCR, and improved PCR5 and PCR6 rules preserving the (quasi-)neutrality of (quasi-)vacuous belief assignment in the fusion of sources of evidence with their Matlab codes. Because more applications of DSmT have emerged in the past years since the apparition of the fourth book of DSmT in 2015, the second part of this volume is about selected applications of DSmT mainly in building change detection, object recognition, quality of data association in tracking, perception in robotics, risk assessment for torrent protection and multi-criteria decision-making, multi-modal image fusion, coarsening techniques, recommender system, levee characterization and assessment, human heading perception, trust assessment, robotics, biometrics, failure detection, GPS systems, inter-criteria analysis, group decision, human activity recognition, storm prediction, data association for autonomous vehicles, identiïŹcation of maritime vessels, fusion of support vector machines (SVM), Silx-Furtif RUST code library for information fusion including PCR rules, and network for ship classiïŹcation. Finally, the third part presents interesting contributions related to belief functions in general published or presented along the years since 2015. These contributions are related with decision-making under uncertainty, belief approximations, probability transformations, new distances between belief functions, non-classical multi-criteria decision-making problems with belief functions, generalization of Bayes theorem, image processing, data association, entropy and cross-entropy measures, fuzzy evidence numbers, negator of belief mass, human activity recognition, information fusion for breast cancer therapy, imbalanced data classiïŹcation, and hybrid techniques mixing deep learning with belief functions as well

    From ecosystems to people: examining the variability in the provision of ecosystem services by eelgrass meadows in Atlantic Canada

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    Seagrass meadows provide functions that support other species and ecosystem services that directly and indirectly benefit human wellbeing. However, growing in estuarine environments, seagrass meadows are exposed to interacting pressures from terrestrial and marine systems, resulting in their degradation worldwide. Efforts to conserve these social-ecological systems have met challenges, including insufficient maps to assess seagrass status and value, a limited understanding of seagrass meadow ecosystem traits underpinning the provision of ecosystem services, and a lack of public awareness necessary to support management decisions. This thesis presents multidisciplinary studies of eelgrass (Zostera marina) meadows in Placentia Bay, Newfoundland and Labrador, Canada, that contribute toward addressing these challenges. In the first study, I evaluated the reproducibility of using remotely piloted aircraft systems (RPAS) to collect seasonal maps of submerged eelgrass meadows in a temperate environment. I show that higher altitude surveys are beneficial when surveying in rapidly changing environments; however, RPAS surveys using three-colour band imagery alone may be insufficient to discriminate seasonal changes. In the second and third studies, I identified meadow structural and environmental traits underpinning eelgrass service as fish habitat and function as a coastal filter. In the second study, I show that shallower and more saline eelgrass meadows enhance diversity in fish life history traits. In the third study, I show that carbon and nitrogen content in the surface sediment was negatively related to sediment density, where isotopic ratios indicated that the carbon was predominantly derived from marine allochthonous (non-eelgrass) sources. Lastly, in the fourth study, using an online survey, I show strong awareness of eelgrass by Canadian coastal Atlantic community members, and support for conservation efforts. Participants identified fish habitat, coastal protection, and water quality maintenance as the three most important ecosystem services provided by eelgrass in Atlantic Canada. Together, the components of this thesis characterise three Newfoundland and Labrador eelgrass meadows, the services they provide, and synthesises the perception of eelgrass by Canadian coastal Atlantic community members. These findings are relevant to local management decision-making and eelgrass monitoring, while also contributing to the growing global characterization of the variability in eelgrass meadow function driving ecosystem services

    Les glissements sous-marins dans l'estuaire du Saint-Laurent, Québec, Canada

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    RÉSUMÉ : L'estuaire du Saint-Laurent, situĂ© dans la province du QuĂ©bec au sud-est du Canada, abrite prĂšs d'une centaine de glissements sous-marins. Leur prĂ©sence dans cette rĂ©gion avec un haut niveau d'alĂ©a sismique a conduit Ă  supposer qu'ils ont Ă©tĂ© dĂ©clenchĂ©s par la sismicitĂ© rĂ©gionale. Le prĂ©sent projet de doctorat a donc pour objectif de comprendre l'origine de ces glissements sous-marins. Le projet utilise une grande quantitĂ© de donnĂ©es gĂ©ophysiques, sĂ©dimentologiques, datations et gĂ©otechniques qui sont intĂ©grĂ©es dans des modĂšles numĂ©riques. Les glissements sous-marins de l'estuaire du Saint-Laurent ont des Ăąges synchrones sur prĂšs de 220 km et sont corrĂ©lĂ©s aux sĂ©ismes historiques majeurs. Ainsi, seule la sismicitĂ© peut les avoir dĂ©clenchĂ©s. L'Ă©tablissement de cette relation permet d'identifier deux Ă©vĂšnements sismiques antĂ©rieurs Ă  la colonisation europĂ©enne en ~645 CE et ~1145 CE. De plus, le sĂ©isme de 1663 CE ressort comme l'Ă©vĂšnement majeur des derniers 2000 ans car il a dĂ©clenchĂ© le plus de glissements sous-marins. Son Ă©picentre positionnĂ© dans la rĂ©gion de Charlevoix n'avait pas Ă©tĂ© rĂ©visĂ© depuis prĂšs d'un siĂšcle. A partir des glissements sous-marins dĂ©clenchĂ©s par la liquĂ©faction du sĂ©diment, l'Ă©picentre du sĂ©isme de 1663 CE a pu ĂȘtre repositionnĂ© Ă  plus de 120 km au nord-est de sa position initiale. Ainsi, il serait associĂ© Ă  une faille active au large de la ville de Tadoussac, proche de l'embouchure du fjord du Saguenay. Enfin, les plans de rupture des glissements sous-marins se dĂ©veloppent aux interfaces d'unitĂ©s sĂ©dimentaires qui correspondent Ă  des transitions d'environnement de dĂ©pĂŽt. L'intĂ©gration de ces niveaux de dĂ©collement dans des modĂšles numĂ©riques permettent de prĂ©dire les zones qui en cas de sĂ©isme majeur glisseront. En conclusion, la sismicitĂ© est le facteur de dĂ©clenchement de glissements sous-marins dans l'estuaire du Saint-Laurent et cela s'explique par la liquĂ©faction de niveaux grossiers (silt Ă  sable) gĂ©nĂ©rĂ©e par les secousses sismiques. De futurs glissements sous-marins sont susceptibles de se produire Ă  l'avenir soulignant la nĂ©cessitĂ© d'Ă©tudier cet alĂ©a naturel au QuĂ©bec. -- Mot(s) clĂ©(s) en français : AlĂ©as-gĂ©ologiques ; GĂ©otechnique ; LiquĂ©faction ; PalĂ©o-sismologie ; SĂ©dimentologie ; StabilitĂ© de pente. -- ABSTRACT : The St. Lawrence Estuary, located in the province of QuĂ©bec in southeastern Canada, is home to almost one hundred submarine landslides. Their presence in this region of high seismic hazard has led to the assumption that they were triggered by regional seismicity. The aim of this PhD project is to understand the origin of these submarine landslides. The project comprises a huge amount of geophysical, sedimentological, age and geotechnical datas which are integrated into numerical simulations. Submarine landslides in the St. Lawrence Estuary have synchronous ages over 220 km and are correlated with major historical earthquakes. Thus, only seismicity can have triggered them. Establishing this relationship allows us to identify two seismic events prior to European colonization around 645 CE and 1145 CE. Moreover, the 1663 CE earthquake appears to be the major event of the least 2000 years because it triggered the greatest number of submarine landslides. Its epicenter located in the Charlevoix region had not been revised for almost century. Using submarine landslides triggered by sediment liquefaction, the epicenter of the 1663 CE earthquake could be repositioned more than 120 km northeast of its originally presumed position. Thus, it could be associated with an active fault off the city of Tadoussac, near the mouth of the Saguenay Fjord. Finally, submarine landslide failure planes develop at interfaces of sedimentary units that correspond to depositional environment transitions. The integration of these levels of detachment in numerical models allows the prediction of areas that will slip in the future, in the case of a major earthquake. In summary, seismicity is the triggering factor for submarine landslides in the St. Lawrence Estuary and this is due to the liquefaction of coarse levels (silt to sand) generated by seismic shaking. Submarine landslides are likely to occur in the future, hence the need to study this natural hazard in QuĂ©bec. -- Mot(s) clĂ©(s) en anglais : Geological hazards; Geotechnics; Liquefaction; Paleoseismology; Sedimentology; Slope stability
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