Dissertations / Theses on the topic 'Stable isotopic tracing'

The use of multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) for trace element stable isotope ratio analysis has been well established within geochemistry since its conception. The utilization of this high precision technique has since progressed to some environmental applications; however, the use of this tool in biological and biomedical work is limited to few studies. The aim of this thesis is to establish viable techniques to enable high precision isotope analyses of Cu and Zn in biological media, and demonstrate these methods via several collaborative pilot studies across biomedicine and ecotoxicology. For this, a new method for the separation of copper from biological materials to enable accurate and precise Cu isotope analyses (±0.10 ‰) has been developed. This has been applied to a study that, with the use of a 65Cu enriched stable isotope tracer, shows that abnormalities of the human copper metabolism exist in those with Parkinson’s disease. The first Zn isotope analyses of various engineered ZnO nanomaterials (NMs) has been performed, which in conjunction with an extensive literature survey and modelling studies, has shown that highly selective and sensitive detection of ZnO NMs can only be achieved with the use of purpose made isotopically labelled ZnO NMs. This is in part due to the high natural background levels of this element and relatively low Zn concentrations involved in ecotoxicologically relevant exposures. This concept has been successfully implemented to investigate ZnO NM uptake by an estuarine invertebrate, and has shown that Zn from ZnO nanoparticles is bioavailable to these organisms. These pilot studies have shown that there is vast scope for high precision isotope analyses of trace metals in life sciences, and support the transition of such investigations to full-scale studies.

Measuring the metabolite profile of plants can be a strong phenotyping tool, but the changes of metabolite pool sizes are often difficult to interpret, not least because metabolite pool sizes may stay constant while carbon flows are altered and vice versa. Hence, measuring the carbon allocation of metabolites enables a better understanding of the metabolic phenotype. The main challenge of such measurements is the in vivo integration of a stable or radioactive label into a plant without perturbation of the system. To follow the carbon flow of a precursor metabolite, a method is developed in this work that is based on metabolite profiling of primary metabolites measured with a mass spectrometer preceded by a gas chromatograph (Wagner et al. 2003; Erban et al. 2007; Dethloff et al. submitted). This method generates stable isotope profiling data, besides conventional metabolite profiling data. In order to allow the feeding of a 13C sucrose solution into the plant, a petiole and a hypocotyl feeding assay are developed. To enable the processing of large numbers of single leaf samples, their preparation and extraction are simplified and optimised. The metabolite profiles of primary metabolites are measured, and a simple relative calculation is done to gain information on carbon allocation from 13C sucrose. This method is tested examining single leaves of one rosette in different developmental stages, both metabolically and regarding carbon allocation from 13C sucrose. It is revealed that some metabolite pool sizes and 13C pools are tightly associated to relative leaf growth, i.e. to the developmental stage of the leaf. Fumaric acid turns out to be the most interesting candidate for further studies because pool size and 13C pool diverge considerably. In addition, the analyses are also performed on plants grown in the cold, and the initial results show a different metabolite pool size pattern across single leaves of one Arabidopsis rosette, compared to the plants grown under normal temperatures. Lastly, in situ expression of REIL genes in the cold is examined using promotor-GUS plants. Initial results suggest that single leaf metabolite profiles of reil2 differ from those of the WT.<br>Messungen des pflanzlichen Metaboloms können ein hilfreiches Werkzeug sein, um Pflanzen zu phänotypisieren. Jedoch sind die Änderungen der Poolgrößen teilweise schwer zu interpretieren, weil sich nicht nur die Poolgrößen sondern auch die Kohlenstoffflüsse unabhängig voneinander ändern können. Werden nun zusätzlich Informationen über die Flüsse ermittelt, kann der pflanzliche Phänotyp deutlich genauer beschrieben werden. Die größte Herausforderung für diese Messungen ist die In-vivo-Integration einer stabilen oder radioaktiven Markierung in einer Pflanze, ohne das System dabei zu stören. In dieser Arbeit wird ein Verfahren entwickelt, um die Verteilung von Kohlenstoffen aus einer gefütterten Vorstufe zu messen. Die Messung basiert dabei auf einem Primärmetabolitenprofil, das mit Hilfe eines Massenspektrometers mit vorgeschaltetem Gaschromatographen erstellt wird (Wagner et al. 2003; Erban et al. 2007; Dethloff et al. eingereicht). Mit dieser Methode ist es einfach möglich, stabile Isotopenprofildaten neben herkömmlichen Metabolitprofildaten zu erzeugen. Die Vorstufe, in diesem Fall 13C Saccharose, wird dazu mit Hilfe eines neuen Petiolen- und Hypokotyl-Fütterungs-Assay in die Pflanze gefüttert. Um die große Menge an Einzelblattproben aufzuarbeiten, die dabei anfallen, wird eine vereinfachte und optimierte Extraktion angewendet. Mit Hilfe einer einfachen Berechnung kann aus den Messdaten eine relative Verteilung des Kohlenstoffs aus 13C Saccharose bestimmt werden. Die Funktionalität dieses Verfahrens wird an Einzelblättern von Arabidopsis-Rosetten gezeigt, wobei sowohl Primärmetabolitenprofile als auch stabile Isotopenprofile erzeugt und untersucht werden. Es kann hierbei gezeigt werden, dass konventionelle Poolgrößen und 13C Poolgrößen einiger Metaboliten eng mit dem relativen Wachstum einzelner Blattpositionen bzw. mit dem jeweiligen Entwicklungsstadium der Blätter zusammenhängen. Anders als bei den meisten anderen Metaboliten zeigen die konventionellen Poolgrößen und 13C Poolgrößen von Fumarsäure ein unterschiedliches Verhalten in den einzelnen Blättern, was Fumarsäure zum interessantesten Kandidaten für weitere Studien macht. Die beschriebenen Untersuchungen werden weiterhin an in Kälte gewachsenen Pflanzen durchgeführt, wobei erste Ergebnisse ein verändertes Metabolitenprofil in den einzelnen Blättern zeigen. Des Weiteren wird die In-situ-Expression von REIL-Genen mit Hilfe von Promotor-GUS-Reportern untersucht. Erste Ergebnisse von Einzelblatt-Metabolitenprofilen der reil2 zeigen einen deutlichen Unterschied zum WT.

Depuis de nombreuses années, une approche a été mise en œuvre reposant sur l'identification de l'origine géographique d'un produit agro-alimentaire via la connaissance de ses isotopes du Sr, notamment via l'analyse du rapport 87Sr/86Sr. L'objectif de cette thèse est d'appliquer cette stratégie de reconnaissance aux huiles d'olive, en s'appuyant sur la production des huiles AOP de Nîmes dans le Sud de la France (Gard). La viscosité, la charge organique élevée, la teneur faible en Sr de cette matrice, rendent néanmoins inadaptés les protocoles de purification du Sr existants. La première approche de l'étude correspond donc à la définition et à la validation d'une méthode de traitement des huiles d'olive en vue de la purification du Sr afin de procéder à l'analyse de sa composition isotopique (CI). La seconde partie de l'étude est consacrée à la définition des processus d'assimilation et de transfert du Sr dans l'olivier. Cette approche, menée grâce à une étude détaillée d'un des moulins AOP de Nîmes, a permis de démontrer que le transfert du Sr des sols vers l'olivier et au sein des oliviers se fait sans fractionnement isotopique.La dernière partie de l'étude s'appuie sur la mesure et la caractérisation des rapports isotopiques 87Sr/86Sr des dix huiles d'olive AOP de Nîmes, et une comparaison de cette signature avec celle des formations géologiques sur lesquelles reposent les parcelles de culture. L'identité de la CI huile-territoire de culture a permis de conclure, dans le contexte de production de l'huile d'olive AOP de Nîmes, que les isotopes du Sr constituent un très bon outil de traçage de l'origine géographique des produits oléicoles<br>For many years, an approach based on the identification of the geographical origin for food product has been implemented through the knowledge of its Sr isotopes, particularly through the analysis of 87Sr / 86Sr ratio. The objective of this thesis is to develop a similar strategy for the olive oils, from the example of PDO Nimes (Gard), in southern France. A specific methodology is necessary since the existing purification protocols of Sr revealed themselves inadequate because of viscosity, high organic load, low Sr content of this matrix In order to proceed to the analysis of the isotopic composition (IC), the first part of the study highlights the definition and validation of a specific method for the treatment of olive oils and strontium purification. The second part of the study is dedicated to expose the processes of assimilation and transfer of strontium into the olive tree. This approach, conducted through a detailed study of one of Nîmes PDO mills, demonstrated that the transfer of strontium from soils to olive tree, and within the olive tree, occurs without isotope fractionation.The last part of the manuscript studies the isotopic ratios 87Sr / 86Sr of the ten PDO olive oils of Nimes and consists in a comparison of this signature with the geological formations underlying the cultivation soils. This approach allows discussing quality of Sr isotopic tool in the geographical recognition of the olive products. The observed similarity between th IC from oils and soil allow us to conclude that, in this context of production, the Sr isotopes are a efficient tool to trace and certify the geographical origin of the oil

The tropical warm pool waters surrounding Indonesia are one of the equatorial heat and moisture sources that are considered as a driving force of the global climate system. The climate in Indonesia is dominated by the equatorial monsoon system, and has been linked to El Niño-Southern Oscillation (ENSO) events, which often result in severe droughts or floods over Indonesia with profound societal and economic impacts on the populations living in the world's fourth most populated country. The latest IPCC report states that ENSO will remain the dominant mode in the tropical Pacific with global effects in the 21st century and ENSO-related precipitation extremes will intensify. However, no common agreement exists among climate simulation models for projected change in ENSO and the Australian-Indonesian Monsoon. Exploring high-resolution palaeoclimate archives, like tree rings or varved lake sediments, provide insights into the natural climate variability of the past, and thus helps improving and validating simulations of future climate changes. Centennial tree-ring stable isotope records | Within this doctoral thesis the main goal was to explore the potential of tropical tree rings to record climate signals and to use them as palaeoclimate proxies. In detail, stable carbon (δ13C) and oxygen (δ18O) isotopes were extracted from teak trees in order to establish the first well-replicated centennial (AD 1900-2007) stable isotope records for Java, Indonesia. Furthermore, different climatic variables were tested whether they show significant correlation with tree-ring proxies (ring-width, δ13C, δ18O). Moreover, highly resolved intra-annual oxygen isotope data were established to assess the transfer of the seasonal precipitation signal into the tree rings. Finally, the established oxygen isotope record was used to reveal possible correlations with ENSO events. Methodological achievements | A second goal of this thesis was to assess the applicability of novel techniques which facilitate and optimize high-resolution and high-throughput stable isotope analysis of tree rings. Two different UV-laser-based microscopic dissection systems were evaluated as a novel sampling tool for high-resolution stable isotope analysis. Furthermore, an improved procedure of tree-ring dissection from thin cellulose laths for stable isotope analysis was designed. The most important findings of this thesis are: I) The herein presented novel sampling techniques improve stable isotope analyses for tree-ring studies in terms of precision, efficiency and quality. The UV-laser-based microdissection serve as a valuable tool for sampling plant tissue at ultrahigh-resolution and for unprecedented precision. II) A guideline for a modified method of cellulose extraction from wholewood cross-sections and subsequent tree-ring dissection was established. The novel technique optimizes the stable isotope analysis process in two ways: faster and high-throughput cellulose extraction and precise tree-ring separation at annual to high-resolution scale. III) The centennial tree-ring stable isotope records reveal significant correlation with regional precipitation. High-resolution stable oxygen values, furthermore, allow distinguishing between dry and rainy season rainfall. IV) The δ18O record reveals significant correlation with different ENSO flavors and demonstrates the importance of considering ENSO flavors when interpreting palaeoclimatic data in the tropics. The findings of my dissertation show that seasonally resolved δ18O records from Indonesian teak trees are a valuable proxy for multi-centennial reconstructions of regional precipitation variability (monsoon signals) and large-scale ocean-atmosphere phenomena (ENSO) for the Indo-Pacific region. Furthermore, the novel methodological achievements offer many unexplored avenues for multidisciplinary research in high-resolution palaeoclimatology.<br>Die tropischen Gewässer um Indonesien sind eine der äquatorialen Wärme- und Feuchtigkeitsquellen, die als treibende Kraft des globalen Klimasystems betrachtet werden können. Das Klima in Indonesien ist geprägt durch das Australisch-Indonesische Monsunsystem. Weiterhin besteht eine Verknüpfung mit El Niño-Southern Oszillation (ENSO) Ereignissen, die oft zu schweren Dürren oder Überschwemmungen in der Region mit tiefgreifenden gesellschaftlichen und wirtschaftlichen Folgen führen. Der neueste IPCC-Bericht legt dar, dass ENSO auch in den nächsten 100 Jahren das vorherrschende Klimaphänomen im tropischen Pazifik bleiben wird. Ferner wird davon ausgegangen, dass sich die ENSO-bezogenen Niederschlagsextrema intensivieren werden. Wenig Übereinstimmung herrscht jedoch bislang zwischen den Klimasimulationsmodellen in Bezug auf die voraussichtlichen Veränderungen von ENSO und dem Australisch-Indonesischen Monsunsystem. Hochaufgelöste Paläoklima-Archive, wie z.B. Jahrringe oder warvierte Seesedimente, geben Auskunft über die natürliche Klimavariabilität der Vergangenheit und können somit dazu beitragen, die Computersimulationen der künftigen Klimaentwicklung zu verbessern und zu validieren. Hundertjährige stabile Jahrring-Isotopenchronologien | Das Hauptziel dieser Doktorarbeit war es, dass Potenzial von tropischen Jahrringen zur Aufzeichnung von Klimasignalen herauszustellen und deren Evaluierung als Paläoklimaproxys. Im Detail wurden stabile Kohlenstoff- (δ13C) und Sauerstoff- (δ18O) Isotopenverhältnisse in Teakbäumen analysiert, und die ersten gut replizierten hundertjährigen (AD 1900-2007) stabilen Isotopenchronologien aus Java (Indonesien) erstellt. Dabei wurden verschiedene klimatische Einflussgrößen getestet, ob diese signifikante Korrelationen mit den Jahrringparametern aufzeigen. Weiterhin wurden hochaufgelöste intra-annuelle Sauerstoffisotopenzeitreihen erstellt, um den Transfer des saisonalen Niederschlagssignals in den jeweiligen Jahrring zu bemessen. Die ermittelte Sauerstoff-Isotopenchronologie wurde anschließend auf mögliche ENSO Signale hin untersucht. Methodische Errungenschaften | Ein zweites Ziel dieser Arbeit war es neue Verfahren zur Analyse stabiler Isotope in Baumjahrringen zu entwickeln und zu optimieren. Zwei verschiedene UV-Lasermikrodissektions-Systeme wurden getestet als neues präzises Präparationswerkzeug für stabile Isotopenstudien. Darüber hinaus wurde eine verbesserte Methode für die Probenaufbereitung stabiler Isotopenmessungen anhand von Zellulose-Dünnschnitten entwickelt. Die wichtigsten Ergebnisse dieser Doktorarbeit sind: I) Die hier vorgestellten neuartigen Techniken zu Probenvorbereitung verbessern die Analyse stabiler Isotope für Jahrringstudien in Hinsicht auf Präzision, Effizienz und Qualität. Es wurde gezeigt, dass die UV-Lasermikrodissektion eine wertvolle Technik ist, um die Beprobung von Pflanzengewebe in höchster Auflösung und beispielloser Präzision durchzuführen. II) Es ist gelungen, einen Leitfaden für ein modifiziertes Verfahren der Zelluloseextraktion an Gesamtholz-Dünnschnitten und der anschließenden Jahrringaufbereitung zu erstellen. Diese neuartige Methode optimiert die Analyse stabiler Isotopenzeitreihen in zweierlei Hinsicht: schnellere und effiziente Zelluloseextraktion und präzise Trennung der Jahrringsequenzen in inter-annueller bis intra-annuelle Auflösung. III) Die hundertjährigen stabilen Jahrring-Isotopenchronologien weisen signifikante Korrelationen mit dem regionalen Niederschlag auf. In den hochaufgelösten stabilen Sauerstoffisotopenwerten spiegelt sich deutlich das Niederschlagssignal der Trocken- und der Regenzeit wieder. IV) Die stabile Sauerstoffisotopenzeitreihe zeigt signifikante Korrelationen mit verschiedenen ENSO Phasen. Dies betont, dass die verschiedenen ENSO Phasen bei der Interpretation von tropischen Paläodaten zu berücksichtigen sind. Die Ergebnisse der Dissertation zeigen, dass saisonal aufgelöste stabile Sauerstoffisotopenchronologien von indonesischen Teakbäumen ein geeigneter Proxy für mehrhundertjährige Rekonstruktionen der regionalen Niederschlagsvariabilität (Monsun-Signale) und großräumiger Ozean-Atmosphären-Systeme (ENSO) für den Indopazifik ist. Darüber hinaus bieten die neuartigen methodischen Errungenschaften viele neue Ansätze für multidisziplinäre hochaufgelöste Studien in der paläoklimatologischen Forschung.

Recent studies have demonstrated that use of stable carbon isotopes and fatty acid biomarkers in combination can be a powerful approach to elucidate trophic relationships in aquatic ecosystems. Stable hydrogen and oxygen isotope ratios of lipids and essential fatty acids in fishes may reflect environmental hydrogen and oxygen isotope signatures, enabling identification of the importance of floodplain lake and riverine energy sources for large river fishes. However, relationships between water and fish lipid or fatty acid hydrogen and oxygen isotopes have not been examined. Therefore, I evaluated whether fatty acid profiles of bluegill differed among rivers and lakes that differed in water hydrogen and oxygen isotope signatures and characterized relationships between water and fish lipid and fatty acid hydrogen and oxygen isotope values. Fatty acid profiles of bluegill were different among sites (lake and riverine sites); bluegills could be identified to their environment of capture with 83% accuracy based on their fatty acid profiles. Hydrogen and oxygen isotope values of bluegill lipids were correlated with water hydrogen and oxygen isotope signatures. Hydrogen isotope values of individual fatty acids were strongly correlated with water hydrogen isotope signatures. Results suggest that fatty acid profiles in conjunction with lipid or fatty acid hydrogen and oxygen isotope values may provide new insights into energy sources and environments (e.g., floodplain lakes vs. rivers) that ultimately support fish production.

This study was undertaken to assess the use of carbon and nitrogen stable isotope analyses as methods to identify source host fish populations of sea lice, Lepeophtheirus salmonis. The delta carbon signatures of parasitic copepodid sea lice used to infect cultured Atlantic salmon in the laboratory were found to be statistically indistinguishable from the delta carbon signatures of blood (ANOVA, p = 1.000) and mucus (ANOVA, p = 0.430) sampled from the wild pink salmon population from which the sea lice originated. As a result, delta carbon signatures show potential as tools to track the movement of sea lice between fish populations. In contrast, delta nitrogen analysis did not show such promise as the natal host fish, wild pink salmon, and novel host fish, cultured Atlantic salmon, between which sea lice were transferred during the study, did not display distinct isotope signatures and thus could not be differentiated. This study found that when applying stable isotope analysis as a method to studying the dispersal of sea lice (1) the blood and mucus of potential source host fish populations should be sampled when assessing their possible relationship to sampled sea lice, (2) sea lice in no later than the parasitic copepodid stage should be analysed, (3) sea lice should be given time to clear their guts of any host materials before analysis takes place, (4) sea lice sampled from the gills should not be not grouped with sea lice sampled from the body surface or fins, and (5) replication unit for sampled parasitic copepodids should be set at the individual and not host fish level. The application of stable carbon isotopes to tracking the movement of sea lice between host fish is a promising method for directly identifying sources of sea lice epizootics and of quantifying the exchange of sea lice between host fish populations.<br>Land and Food Systems, Faculty of<br>Graduate

Nous avons étudié les mécanismes de croissance du dépôt atomique couche par couche (ALD) de films minces de ZnO, TiO2, Al2O3 et HfO2, en particulier en utilisant le traçage isotopique stable en conjonction avec les techniques d'analyse par faisceau d'ions isotopiquement sensibles, à savoir, la Spectrométrie de rétrodiffusion de Rutherford (RBS), l’analyse de détection de recul élastique (ERDA) et l’analyse de réaction nucléaire (NRA). En utilisant des précurseurs ALD marqués au deutérium, isotope rare, nous distinguons l'origine des éléments bruts et des impuretés dans chacun des films - de l'un ou l'autre des précurseurs, ou des gaz résiduels dans la chambre de réaction. Les contributions relatives sont suivies en fonction de la température de dépôt, du bas vers le haut de la fenêtre de température ALD. Nous avons constaté que la structure de surface du film pouvait être lisse ou rugueuse selon les matériaux déposés. En faisant croître différents couples de films A-sur-B ou B-sur-A, dans des précurseurs différemment marqués, nous avons mis en évidence le rôle de la molécule d'eau dans le mécanisme de croissance multicouche, et avons pu observer la diffusion atomique de H et D dans le système multicouche. Dans un système multicouche, nous avons développé un prototype de structure sandwich qui facilite le transport des ions protons lorsque le film multicouche est polarisé électriquement dans un électrolyte acide également enrichi en deutérium ou utilisant des acides marqués au deutérium, dans des conditions pertinentes pour le fonctionnement des batteries proton-ion (PIB)<br>We have studied the Atomic Layer Deposition (ALD) growth mechanisms of ZnO, TiO2, Al2O3 and HfO2 thin films, in particular using stable isotopic tracing in conjunction with the isotopically sensitive ion beam analysis techniques Rutherford Backscattering Spectrometry (RBS), Elastic Recoil Detection Analysis (ERDA) and Nuclear Reaction Analysis (NRA). By using ALD precursors labelled in rare isotope deuterium we distinguish the origin of the bulk and impurity elements in each of the films - from one or other of the precursors, or from residual gases in the reaction chamber. The relative contributions are followed as a function of deposition temperature, from below to above the ALD temperature window. We show by NRA determination of carbon in the films that there is a narrower temperature range, within the ALD window, for which residual contaminants are minimized. We found that the film surface structure could be smooth or rough depending on the grown materials. By growing different couples of films A-on-B or B-on-A, in differently labelled precursors, we highlight the role of the water molecule in the multilayer growth mechanism, and could observe the H and D atomic diffusion in the multilayer system. In the TiO2/ZnO multilayer system, we developed a prototype sandwich structure that facilitates proton ion transport when the multilayer film is electrically polarized in an acid electrolyte also enriched in deuterium or using deuterium labelled acids, under conditions relevant to the operation of proton ion batteries (PIB). The depth distributions of H and D established in this system by ERDA showed fast galvanostatic proton insertion and extraction. We have studied the Atomic Layer Deposition (ALD) growth mechanisms of ZnO, TiO2, Al2O3 and HfO2 thin films, in particular using stable isotopic tracing in conjunction with the isotopically sensitive ion beam analysis techniques Rutherford Backscattering Spectrometry (RBS), Elastic Recoil Detection Analysis (ERDA) and Nuclear Reaction Analysis (NRA). By using ALD precursors labelled in rare isotope deuterium we distinguish the origin of the bulk and impurity elements in each of the films - from one or other of the precursors, or from residual gases in the reaction chamber. The relative contributions are followed as a function of deposition temperature, from below to above the ALD temperature window. We show by NRA determination of carbon in the films that there is a narrower temperature range, within the ALD window, for which residual contaminants are minimized. We found that the film surface structure could be smooth or rough depending on the grown materials. By growing different couples of films A-on-B or B-on-A, in differently labelled precursors, we highlight the role of the water molecule in the multilayer growth mechanism, and could observe the H and D atomic diffusion in the multilayer system. In the TiO2/ZnO multilayer system, we developed a prototype sandwich structure that facilitates proton ion transport when the multilayer film is electrically polarized in an acid electrolyte also enriched in deuterium or using deuterium labelled acids, under conditions relevant to the operation of proton ion batteries (PIB). The depth distributions of H and D established in this system by ERDA showed fast galvanostatic proton insertion and extraction

The focus of this work was on the use of otolith microchemistry and fish eye lens chemical profiles to measure fish movement and provided indirect support for the use of otolith microchemistry to examine exposure to crude oil. Chapter 1 provides an introduction to the applications of otolith microchemistry and eye lens isotopic profiles. In the second chapter, which examined associations between metal exposure and lesion formation in fishes collected after the Deepwater Horizon (DWH) oil spill, I did not observe any change in oil-associated metal concentrations in otoliths coinciding with the timing of the DWH oil spill. This suggests that either the technique used is not sensitive enough to detect any transient changes that may have occurred because of exposure to the oil spill or that the fish examined were not exposed to the oil spill. However, I did find that lesioned fish may have been exposed to a persistent source of trace-metals in the GoM prior to, during, and after the oil spill, and metal-induced immunomodulation may have occurred in these fish. These interactions between the physiological and environmental modulation of otolith element incorporation were explored further in Chapter 3 in which multiple tests demonstrated that physiology explained more of the variation in otolith chemical tags than ambient water chemistry. These findings suggest that the use of otolith microchemistry alone to track fish movement and potential exposure to harmful metals may be complicated by physiological control of otolith microchemistry. Thus, in Chapter 4, I pursued a novel method to evaluate the movement of fish across isoscapes of varying δ15N. I validated the use of fish eye lenses as potential lifetime recorders of isotopic histories and in Chapter 5 compared the use of fish eye lens δ15N profiles to otolith microchemistry profiles to examine fish movement. Both techniques suggested similar patterns of movement in Red Snapper from the northern GoM to the West Florida Shelf. This is the first study to use these complimentary techniques to track fish movement.

Oxic soils are generally classed as a sink for atmospheric methane (CH4), as methanotrophy far outweighs internal production. However, CH4 production can be stimulated in such soils by exposure to wet conditions, or even cause them to act as a net CH4 source. The work detailed in this thesis was carried out with the aims of investigating the nature and distributions of the microbial communities controlling CH4 cycling in waterlogged aerobic soils, and assessing their potential to respond to marginal increases in soil moisture and aeration conditions caused by climate-change induced precipitation. The concentration of archaeol in its free and conjugated forms was investigated within three oxic soils using gas chromatography/mass spectrometry (GC/MS) in combination with selected ion monitoring (SIM). Archaeol was proposed to be a biomarker for methanogenic biomass in such soils on the basis that trends in abundance differed from Thaumarchaeota-derived crenarchaeol. Phospholipid and glycosidic archaeol seemed to derive from extant and fossilised methanogen biomass, respectively. Observed trends in concentrations were attributed to carbon contents and soil moisture, due to their association with the development of anoxic microniches and substrate availability. The presence and distribution of glycerol dialkyl glycerol tetraethers (GDGTs), detennined by high performance liquid chromatography/atmospheric pressure chemical ionization-mass spectrometry (HPLC/ APCI-MS), were investigated within two highmoisture, oxic soils. As with archaeol, trends in distribution were driven by organic matter content and soil moisture. Bacteria-derived GDGTs dominated at both sites. Isoprenoid GDGTs I and II-IV derived from a mutual archaeal source, potentially methanogens; however, distributions did not reflect archaeol concentrations.

Lakes play an important role in the global carbon (C) cycle as they process carbon from terrestrial (allochthonous) and within lake (autochthonous) sources and may store C over long periods of time. Some arctic lakes contain high concentrations of dissolved organic carbon (DOC) that does not absorb light and thus remains colourless. The origin of this DOC remains unknown, but the sediment of these lakes have been suggested to accumulate primarily autochthonous (algal) C. I developed an experimental chamber for hydrogen (H) isotope pre-treatments and applied a novel H isotope tracing approach to determine the origin of the DOC and sediment C of a lake on SW Greenland known to contain colourless DOC. I hypothesized that autochthonous C was the prime source of DOC and sediment C, in line with previous theories. Analyses of algae and soil samples from the catchment revealed that local allochthonous and autochthonous C sources had a δ2H composition of -139 ‰ and -209 ‰, respectively. In contrast to my hypothesis, the analysed DOC had a mean δ2H isotopic composition of -147 ‰ indicating a dominance (ca 80-90 %) of allochthonous C. Similarly, the sediment had a mean δ2H isotopic composition of -155 ‰, suggesting that about 84 % of the C accumulating in the sediment was derived from terrestrial sources. The terrestrial origin was supported by field observations of high DOC seepage water (up to 70 mg L-1) with uncharacteristically low light absorption values entering the lake during high precipitation events. My results indicate that terrestrial processes are fundamental C sources for arctic lakes, even in regions with very low precipitation.

The mineralisation which occurs within the Central Wales Orefield (CWO) is of historical importance, as the area was once one of the major producers of silver in the United Kingdom. In comparison to the other ore districts situated in the British Isles however, surprisingly little research has been undertaken in the CWO in recent years. This thesis redresses this issue by examining, in conjunction with Pb isotope analysis, the geochemical variation in three sulphide minerals (galena, sphalerite and chalcopyrite), collected from six mineralised lodes located in the Afon Clarach catchment; a small river system situated in the northern region of the CWO, north of Aberystwyth. Although the Pb-Ag mines in the CWO have been abandoned for over 100 years, many of these sites continue to have a legacy of pollution, which under the Water Framework Directive (2000/60/EC) now require remediation. By characterising the trace metal and Pb isotope fingerprints of the six mineralised lodes situated in the Afon Clarach catchment, this thesis successfully identifies those mine sites which continue to contaminate the river sediments of the Afon Clarach with trace metals and therefore require remediation. Variations in the Pb isotope ratios and the concentrations of Sb, Tl and Hg identified in the Pb-ore and Tl, In, Fe, Mn and Cu in the Zn-ore collected from the six lodes have successfully differentiated the two periods of mineralisation previously identified in the CWO by Mason (1994) and dated by Fletcher et al. (1993). The Camdwr, Cwmerfyn, Cwmsymlog and Daren Lodes are dominated by the older phase of mineralisation (Group 1) whereas the Hafan Lode is dominated by the younger phase (Group 2). In contrast, the Goginan Lode contains ore minerals which were precipitated during both stages of mineralisation. In addition to differentiating the two periods of mineralisation, subtle variations in the concentrations of Ag, Cd, Co, Cu, Fe, Ni, Pb and Sb in the Pb-ore; Cd, Cu, Ga, Fe, Hg, Ni, Pb, Sb, Tl, In and Zn in the Zn-ore and Cu, Fe, Ga, Hg, In, Pb, Sn and Zn in the Cu-ore differentiate those lodes assigned to the older Group 1. It is possible to use the chemical and isotope signatures of the lodes, to trace the metal contamination, particularly that of Pb, Zn, Cu and Sb, into the river sediments and identify those sites which are continuing to contaminate the Afon Clarach. The priority mine sites identified in the study include Bwlch Mine, Cwmsymlog Mine, Daren Mine and Cwmerfyn Mine, all of which are located along the Nant Silo, one of the four main tributaries of the Afon Clarach. The inclusion of Bwlch and Cwmerfyn Mines in this list is of some concern as these sites have already undergone some remediation work during the early 1990‟s. In addition, mines including Llety-Hen, Willowbank and Pen-y-Cefn are also introducing some metal contamination into the Afon Stewi. The remaining two tributaries of the Afon Clarach (the Bowstreet Brook and the Afon Peithyll) are less affected by metal contamination. The spoil tips located at Mynydd Gorddu Mine, situated on the Bowstreet Brook, however do pose a threat to the local environment with high mean concentrations of Pb (4.21 %), Zn (4.02 %) and Sb (221 g/g) found in the tailings and high concentrations of soluble Zn (7.3 mg/L) found in the water draining the spoil tips.

Attempts to use stable isotope carbon (delta13C) and nitrogen (delta15N) ratios to construct trophic positions and track mercury biomagnification in zooplankton and 13 fish species from a coastal food web of the Gulf of Oman illustrated some potential differences in this environment compared to the aquatic ecosystem of the northern hemisphere. Due to the large difference in delta13C values (3.4&permil;) between zooplankton planktivorous fish species (S. crumenophthalmus, S. longiceps and R. kanagurta), zooplankton would seem to not be the primary diet of these fish species as commonly described in literature. Total mercury (T-Hg) concentrations of zooplankton were very low (range 0.010 to 0.037 mug&middot;g-1, N = 27) with a mean methyl mercury (MeHg) of 0.001 mug&middot;g-1 (range 1-19%, N = 5). The lowest T-Hg (0.003 mug&middot;g-1) was found in planktivore (S. longiceps) and the highest was 0.760 mug&middot;g -1 in predator shark (R. acutus) with average MeHg for all fish of 72% (range: 33-100%, N = 150). Using 15 N as indicator of trophic position, neither total mercury (T-Hg) nor methyl mercury (MeHg) were found to biomagnify. Regression slopes were 0.08 and 0.05 for T-Hg and MeHg respectively as a function of delta15 N. This indicates that biomagnification was lower in this tropical ocean compared to that found in freshwater and marine ecosystems of the arctic and temperate zones. Methyl mercury levels in the fish species commonly consumed are low and intake calculations showed that individuals can safely consume fish.

Water is a valuable and crucial resource, the protection of which poses environmental, social and economic challenges. Fundamental to the sustainable use of water is effective management. In the Canterbury region of New Zealand, nitrate contamination has become a resource management issue due to changes in land use and intensification, which have placed pressure on the region’s groundwater and surface water systems. The purpose of this study was to assess and track nitrate concentrations on the Central Canterbury Plains with specific emphasis on a local point source of nitrate, the Ashburton Meat Processors plant. To make this assessment review of historical data was followed by the collection of 131 groundwater and 25 surface water samples to analyse the geochemical properties of the water and the stable isotopic composition of nitrate in the water. It was hypothesised that nitrate concentrations at a regional scale have increased since regular records began and that the stable isotopic composition of different nitrate sources are not discernable. Nitrate concentrations across the Canterbury region were found to have increased, prompting concerns about water quality. Concentrations are elevated above natural background levels across much of the Canterbury Plains and extreme concentrations are associated with local point sources of nitrate. Nitrate concentrations down gradient of the Ashburton Meat Processing plant are shown to have declined approximately 5% per year for the past ten years, which is in contrast to the rest of the region, where average concentrations have nearly doubled in 20 years. The reduction of contamination from the point source is most likely the result of the implementation of better wastewater management practices in the early 21st century. The δ18O and δ15N values of nitrate were found to be relatively homogenous over the Canterbury Plains. Therefore, it is suggested by this study that the dual-isotope approach alone, is not a viable tool for nitrate source identification in the region. The uniform nitrate stable isotopic composition in Canterbury could be attributed to a single, principle source of nitrate, such as clover, that overprints other isotopic compositions of nitrate source, or may also be the result of soil processes and the farming techniques used in the region. This research presents important findings for the future of identifying and managing nitrate sources in the Canterbury region. Better management practices are required for the diffuse source(s) of nitrate contributing to the widespread contamination. Critical thinking and the willingness of stakeholders to engage in the identifying, documenting and solving problems is necessary to ensure the effective management and sustainability of this precious resource.

Top predators can have large effects on community and population dynamics but we still know relatively little about their roles in ecosystems and which biotic and abiotic factors potentially affect their behavioral patterns. Understanding the roles played by top predators is a pressing issue because many top predator populations around the world are declining rapidly yet we do not fully understand what the consequences of their potential extirpation could be for ecosystem structure and function. In addition, individual behavioral specialization is commonplace across many taxa, but studies of its prevalence, causes, and consequences in top predator populations are lacking. In this dissertation I investigated the movement, feeding patterns, and drivers and implications of individual specialization in an American alligator (Alligator mississippiensis) population inhabiting a dynamic subtropical estuary. I found that alligator movement and feeding behaviors in this population were largely regulated by a combination of biotic and abiotic factors that varied seasonally. I also found that the population consisted of individuals that displayed an extremely wide range of movement and feeding behaviors, indicating that individual specialization is potentially an important determinant of the varied roles of alligators in ecosystems. Ultimately, I found that assuming top predator populations consist of individuals that all behave in similar ways in terms of their feeding, movements, and potential roles in ecosystems is likely incorrect. As climate change and ecosystem restoration and conservation activities continue to affect top predator populations worldwide, individuals will likely respond in different and possibly unexpected ways.

L'exploration de la niche écologique d'une espèce implique une analyse à plusieurs échelles, car différentes contraintes environnementales peuvent avoir des conséquences écologiques importantes. Cependant, l'absence d'informations précises sur l'écologie des petites espèces de procellariiformes a considérablement limité leur étude, impactant notre capacité à définir une planification de conservation appropriée. Les avancées technologiques dans la miniaturisation des enregistreurs de données permettent depuis peu de collecter des données écologiques sur ces espèces. Dans cette étude, une approche multidisciplinaire a été utilisée pour étudier la niche écologique des pétrels plongeurs communs et de Géorgie du Sud. Les principaux objectifs étaient de : 1) décrire leur écologie alimentaire pendant les périodes de reproduction et de non-reproduction, et étudier leurs variations interannuelles ; 2) déterminer les différences écologiques entre les populations de l'Océan Austral ; et 3) étudier les variations de leur écologie tout au long du cycle annuel dans un contexte de ségrégation écologique entre ces deux espèces sœurs. Les résultats ont démontré que les pétrels plongeurs présentent des capacités de vol remarquables malgré leur charge alaire élevée, se nourrissant sur de vastes zones pendant la reproduction et migrant à plusieurs milliers de kilomètres de leur colonie pendant la période post-reproduction. Ces analyses ont révélé d'importantes différences écologiques au sein des espèces, notamment en termes de phénologie et de zone de migration. La collecte de données sur plusieurs années a considérablement renforcé ces résultats et fournit des informations précieuses pour comprendre les limites des niches écologiques des pétrels plongeurs. Enfin, la variation de ségrégation en fonction du stade de reproduction a démontré l'importance d'une approche multi-outils pour mieux décrire et comprendre la coexistence d'espèces écologiquement similaires<br>Exploring a species’ ecological niche entails investigating at multiple scales, as different environmental threats and niche constraints between intra-species levels may lead to important ecological and conservation consequences. However, the absence of precise information about small procellariiform species ecology has greatly limited ecological niche modelling studies, directly impacting our ability to delineate proper conservation planning. Technological advancements in the miniaturisation of data loggers have made it possible to collect ecological data of such species. In the present study, a multi-tooled approach was used to investigate the ecological niche of the common and the South-Georgian diving petrels. The primary objectives were to: 1) describe their foraging ecology during the breeding and non-breeding periods, and investigate their inter-annual variations; 2) determine the ecological differences between populations throughout the Southern Ocean; and 3) study the variations in their foraging ecology throughout the entire annual-cycle in the context of niche segregation between two sibling species. The results demonstrated that diving petrels exhibit remarkable flying abilities despite their high wing loading, foraging over large areas during the breeding season, and migrating several thousands of kilometres from their colony during the post-breeding period. These analyses revealed important ecological differences throughout the species distribution, particularly in terms of phenology and migration area. Collecting data over several years substantially strengthens results and provides valuable information to understand the variations and the limits of diving petrel ecological niches. Finally, a stage-dependent and context-dependent niche segregation analysis demonstrated the importance of a multi-tooled approach to better describe and understand the co-existence of ecologically similar species

Most albatrosses are critically endangered, endangered or vulnerable due to the deleterious impact of fisheries, pollution, introduced species, habitat alteration, and climate change. Foraging behaviour influences many aspects of seabird biology, and a detailed understanding of foraging ecology is required to better predict the impacts of significant changes to the marine environment. Campbell Albatross (Thalassarche impavida) is a threatened endemic, confined to a small number of locations on Campbell Island, New Zealand and was recently split from the closely related Black-browed Albatross (T. melanophrys). We currently lack much basic information on the foraging behaviour of this species, hindering our ability to understand how change may have occurred in the past and make predictions about it’s long-term future. First, I used GPS loggers and stable isotope analysis of blood to investigate how distribution and foraging effort (distance travelled and duration) varied with sex and breeding stage. I found that Campbell Albatrosses are sexually dimorphic and showed sex-specific foraging behaviour and habitat use – although this varied by stage of reproduction. Because males and females may be vulnerable to different threats, such as interactions with fisheries, I compared the spatial overlap and high resolution spatio-temporal overlaps between fisheries vessels and albatrosses within New Zealand’s Exclusive Economic Zone (EEZ). Albatrosses utilised 32% of the EEZ, however they overlapped with fisheries vessels in only 0.20% of the area. Previous research has demonstrated that the influence of fisheries vessels goes beyond the immediate location of the boat itself. Campbell Albatross have low levels of spatio-temporal overlap with fisheries – with males overlapping more than females. More generally, my results indicate that adding data on fine scale interactions will improve fisheries risk assessments, and provide information needed for the conservation and management of the Campbell Albatross. A key development in recent ecological research has been a greater appreciation that inter-individual variation in foraging behaviour can have profound population-level consequences. Accordingly I tested for individual differences in foraging behaviour in Campbell Albatrosses. The majority of individuals demonstrated both annual and inter-annual individual consistency in foraging locations, and the degree of specialisation was influenced by both sex and year. Consistent terminal latitude and longitude of foraging trips indicated high foraging area fidelity with a degree of flexibility in the fine-scale location. During brooding, females used the Campbell Plateau and showed more consistent behaviours than males, which tended to forage in the Southern Ocean. This adds to a growing body of evidence of individual foraging specialisation among seabirds in general and albatrosses in particular and reveals marked inter-individual differences in vulnerability to threats. In light of the evidence of individual foraging specialisations in the Campbell albatross, I also preformed a literature review of individual foraging specialisations across all seabirds. I found studies examining foraging specialisation for 35 species, with 28 (80%) providing evidence of consistent inter-individual differences (i.e. specialisation). Current studies suggest that specialisation is influenced by environmental variability and resource predictability, however, with limited data in tropical regions, more studies are needed to test these links. In summary, my thesis has provided new information on Campbell Albatross foraging ecology. Sex specific variations in behaviour and habitat use may influence conservation and management strategies. I have been able to contextualise the consistent individual differences in foraging distribution described for this species in light of global patterns of individual foraging specialisation in seabirds and highlight future areas of research.

La recharge au niveau des piémonts constitue une source importante de recharge naturelle des eaux souterraines dans les zones arides et semi-aride. Le bassin du Tensift, au centre du Maroc, héberge la plaine du Haouz et l'aquifère alluvial du Haouz dont l'extension spatiale dépasse 6000 km². L'eau souterraine est la source d'eau principale pour les activités agricoles, industrielles et pour l'alimentation en eau potable Cette ressource st considérablement affectée par la surexploitation et le changement climatique. La détermination des sources et des processus de recharge, en particulier au niveau des piémonts, est primordiale pour la gestion efficace des ressources en eau. Malgré son importance, la dynamique de la recharge au niveau des piémonts du Haut-Atlas, comme dans les zones semi-arides autour du globe, reste peu étudiée. L'objectif de la présente étude est d'investiguer, de près, les sources de recharge dans le piémont du Haut-Atlas, en se focalisant sur l'infiltration au niveau des oueds. L'étude est basée sur la combinaison de plusieurs types de de données : prélèvements des seguias, piézométriques, isotopiques, hydrochimiques, teneur en eau des sédiments et température des sédiments récoltés sur le terrain. Les données ont été analysées qualitativement et quantitativement par modélisation. Les données piézométriques et isotopiques (18O et ²H) ont été utilisés pour comparer la recharge naturelle et la recharge induite par irrigation dans le piémont du Haut-Atlas. L'évolution piézométrique a montré que la recharge induite par l'irrigation traditionnelle dépasse celle induite par l'infiltration au niveau des oueds. Cela est en accordance avec la distribution spatiale des signatures isotopiques qui montrent l'influence du captage des eaux par Séguias, en période d'écoulement normal sur la recharge des eaux souterraines. L'évolution hydrochimique des eaux souterraines dans la zone d'étude est influencée par les interactions eau/roche, la dissolution des minéraux carbonatés et des évaporites, l'hydrolyse des silicates et les échanges ioniques entre l'eau et les sédiments. L'influence de l'irrigation par les eaux de surface sur la recharge des eaux souterraines et les pratiques agricoles dans la zone d'étudie ont préservé la bonne qualité de ces eaux et leur adéquation à l'utilisation domestique. La teneur en eau et la température des sédiments mesurés sur un site expérimental dans le lit de l'oued Rheraya, pendant une année entière, ont été utilisés pour caractériser la dynamique de l'infiltration et de la recharge des eaux pendant les périodes d'écoulements. ces données sont aussi exploitées pour le calage d'un modèle du transport d'énergie dans le milieu poreux pour calculer les taux d'infiltration. Pendant toute l'année, la recharge totale calculée est de 425 mm/m². La recharge est principalement induite par les crues et elle est contrôlée par la saisonnalité, l'état antérieur de saturation des sédiments, la durée des évènements, puis la hauteur du niveau de l'eau. Les résultats de cette étude peuvent être incorporés dans les schémas futurs de la gestion et de la préservation des ressources en eau dans le bassin de Tensift<br>Mountaifront recherge is the recharge of grounwater occuring in the piedmonts of high-elevation mountain often receiving more precipitation due to orographic effects. This type of recharge is the major source of groundwater replenishment in many semi(arid) basins. The Tensift basin in central Morocco hosts the large alluvial plain of Haouz with its vast pheatic aquifer of more than 6000 km². groundwater in the Haouz plain is the main source of water for the socio-economic activities in the area. This groundwater originates from the adjacent high-Atlas ranges. Despite the importance of mountain-front recharge for the socio-economic deveopment in the area, it was never investigated with care but only incorporate in a very limited regional-scale studies providing highly speculative conclusions. The aims of the present study is the close investigation of recharge sources in the mountain-front area of the High-Atlas of Marrakech at the local scale, with an emphasis on infiltration within wadi channels. Hydrophysical data (piezometry, sediment water content and heat), hydrochemical (major ions) and environmental tracers (stable isotopes of water) from field campaigns and experiments were used in this study. The data acquired was analyzed by analytical methods and modeling (heat transport modeling). Coupled groundwater fluctuation measurements and environmental tracers (18O, ²H, and major ions) were used to identify and compare the natural mountain-front recharge to the anthropogenic irrigation recharge. Within the High-Atlas mountain front of the Ourika Basin, Central Morocco, the groundwater fluctuation mapping from the dry to wet season showed that recharge beneath the irrigation area may be higher than recharge along the streanbed. A conceptual model of seasonal groundwater recharge sources in the study area was established. Theses findings highlight that irrigation practices can result in the dominant mountain front racharge process for groundwater. The hydrochemical evolution of groundwater in the mountain-front area is controlled mainly by water-rock interactions through mineral dissolution, silicate weathering and ion exchange. The strong relationship between groundwater and mountain water, enhanced by traditional irrigation, and the ecological agriculture practiced in the area preserved the excellent quality of groundwater. Streambed water content and temperature were continuously logged over a year for the Rheraya intermittent wadi. Over the entire year, the calculated total potential recharge based on heat transfer modeling was 425 mm/m2. During winter and spring when the alluvium has a higher water moisture, this recharge is predominantly generated by floods. Normal streamflow generally generates low infiltration but contributes to wetting the sediment. During the summer, brief flashfloods over dry sediment result in shallower and slow wetting from infiltration, despite of their higher peak streamflow. Results from this study can be incorporated in future management schemes for the water resources preservation in the Tensift basin

Trabalho Final de Mestrado Integrado, Ciências Farmacêuticas, Universidade de Lisboa, Faculdade de Farmácia, 2017<br>Mercury (Hg) is an ubiquitous contaminant with a severe impact in public health. In general, humans are mainly exposed to this metal due to fish and seafood consumption where high concentrations of this element can be found due to the bioaccumulation and biomagnification processes occurring in the water environments. A previous study driven by ANSES showed high mercury concentrations on fish from the Aquitanian lakes and this work integrates a new research program that aims at determining the origin of Hg pollution to the biota living in these lakes. The species analysed by CVG-MC-ICP-MS include clams, crayfish, bream, pike, perch and pike-perch collected from September to November 2015 in Hourtin-Carcans, Lacanau, Casaux-Sanguinet, and Parentis-Biscarrose lakes. Hg is involved in several transformations due to environmental and biological processes that influence its stable isotope composition. Therefore, Hg isotopic mass dependent (MDF) and mass independent fractionation (MIF) are powerful tools to identify the major sources and processes involved in Hg bioaccumulation in foodwebs. In the samples analysed, δ202Hg showed a wide range (-0.93‰ to 0.60‰). In general, δ202Hg is increased from clam to crayfish to bream to pike to perch to pike-perch. MIF had a wider range (0.11‰ to 3.84‰) and clam showed the smallest value. Pike, perch and pike-perch displayed the highest ∆199Hg value. In these samples, the mercury bioaccumulated results principally of MeHg demethylation (∆199Hg/∆201Hg = 1.3). Additionally, the stable isotopic composition of Hg was related to the trophic levels of the species calculated by using δ13C, δ15N. The results obtained are a good contribution for the understanding of the mercury biogeochemical cycle in the Aquitanian lakes although there is a need for analysis of samples such as sediments and prey fish to conclude about the trophic transferences of mercury existing in the Aquitanian lakes.<br>O mercúrio é um poluente ubíquo na Natureza, existindo na atmosfera, no solo e nos meios aquáticos, incluindo os meios lacustres, onde é acumulado e alvo de diversas reações, entre elas a alquilação, maioritariamente realizada por bactérias anaeróbias, cujo produto é o metilmercúrio. O metilmercúrio é acumulado no plâncton e devido à sua elevada afinidade pelos grupos sulfidrilo das proteínas citosólicas, é bioacumulado ao longo da cadeia alimentar, atingindo elevadas concentrações em peixes predadores. O consumo de peixe é a maior fonte de exposição de metilmercúrio para os humanos. De acordo com o conhecimento atual, o mercúrio é acumulado principalmente nos rins e no fígado, uma vez que estes são órgãos depuradores. Por outro lado, o metilmercúrio é principalmente acumulado no músculo e no cérebro. A maior parte do metilmercúrio ingerido a partir do peixe é absorvido no trato gastrointestinal e após a formação de um complexo com a L-cisteína, consegue mimetizar a metionina e atravessar a barreira hematoencefálica. Assim, este composto atinge concentrações no cérebro, 3 a 6 vezes superiores às do sangue, levando a neurotoxicidade. Num estudo feito pela ANSES - Agência de segurança alimentar de França em 2011, foi verificada a existência de elevadas concentrações de mercúrio em determinadas espécies de peixes dos lagos Aquitâneos,levando à proibição da pesca nos lagos Hourtin-Carcans e Lacanau. O projeto Contamination des Lacs AQuitains et impacts Humains (CLAQH) surge no seguimento destes acontecimentos e com o intuito de ser compreendida a extensão da poluição por mercúrio nos lagos Aquitâneos, a sua origem e distribuição nos diferentes ecossistemas, o impacto que pode ter na população humana e a perceção de risco para os consumidores. As tarefas estão divididas entre diferentes grupos, sendo que o objetivo deste trabalho específico foi rastrear a transferência do mercúrio ao longo da cadeia trófica por análise isotópica. Para isso, foram pescados dos lagos Hourtin-Carcans, Lacanau, Casaux-Sanguinet e Parentis-Biscarrose, as espécies Abramis brama, Esox Lucius, Perca fluviatilis, Sander lucioperca, Procambarus clarkii e Corbicula flumínea entre Setembro e Novembro de 2015. O elemento mercúrio tem diversos isótopos estáveis, entre eles, 196Hg, 198Hg, 199Hg, 200Hg, 201Hg, 202Hg e 204Hg, cuja abundância natural é de 0,15%, 9,97%, 16,87%, 23,10%, 13,18%, 29,86% e 6,87%, respetivamente. O fracionamento isotópico tem a ver com a ocorrência de variações na composição isotópica natural do elemento. A análise isotópica do mercúrio permite rastrear as fontes de mercúrio por forma a reduzir a exposição das populações a este composto neurotóxico. Quando submetidos a reações de transformação ou troca, todos os isótopos de mercúrio são sujeitos a fracionamento dependente da massa (MDF). Por outro lado, o fracionamento independente da massa (MIF) é principalmente verificado nos 2 isótopos ímpares de mercúrio (199Hg e 201Hg) e pensa-se que este último fenómeno ocorra devido a diferenças na paridade do isótopo ao invés da sua massa. Os diferentes isótopos de um elemento têm ligeiras diferenças na sua massa, o que faz com que os isótopos participem em processos físicos e reações bioquímicas com eficiências diferentes. Este fenómeno é denominado de fracionamento dependente da massa e é a forma mais comum de fracionamento, sendo uma ferramenta útil na obtenção de informação acerca de processos físicos e reações químicas aos quais os elementos foram expostos. Este parâmetro é comummente representado por δXXXHg. Observa-se o fracionamento independente da massa quando é observado um desvio na composição isotópica esperada pelo fracionamento dependente da massa. Normalmente, este parâmetro é representado por ΔXXXHg. Pensa-se que o fracionamento independente da massa ocorra devido a ligeiras diferenças na interação entre o núcleo destes isótopos e a sua nuvem eletrónica, o que vai afetar algumas características de certos isótopos, nomeadamente o bonding. Estes processos ocorrem essencialmente nos isótopos de massa ímpar. Diferentes estudos, compilados por Blum et al., 2014, indicam que variações negativas no fracionamento dependente da massa são observadas em amostras atmosféricas e sedimentos enquanto que variações positivas são observadas em amostras colhidas de humanos e material geológico. Peixes de água doce apresentam uma grande variação desde valores negativos a positivos de MDF. Valores positivos de fracionamento independente da massa são observados em peixes e invertebrados enquanto que valores negativos são observados e amostras atmosféricas e vegetação. Em suma, processos que contribuam para a absorção e manutenção do mercúrio na cadeia alimentar originam valores positivos de Δ199Hg. Por outro lado, processos responsáveis pela libertação do mercúrio para a atmosfera estão associados a valores negativos de Δ199Hg. Os isótopos de mercúrio de massa atómica par são úteis para a rastreabilidade do metilmercúrio durante transferências tróficas e bioacumulação, uma vez que estes fracionam principalmente através de reações fotoquímicas. É sugerido que na mesma cadeia alimentar é observado um enriquecimento isotópico, sendo verificado um valor positivo de δ202Hg. Em geral, na mesma cadeia alimentar, os predadores possuem valores de δ202Hg superiores às presas. A assinatura MIF permite identificar fontes específicas de mercúrio como antropogénicas derivadas da indústria ou atividade mineira. Permite ainda o seguimento da fonte de exposição para os organismos uma vez que à luz do conhecimento atual, o fracionamento independente da massa não foi observado em processos biológicos. A assinatura isotópica do mercúrio permite também o melhor conhecimento do ciclo biogeoquímico deste elemento, uma vez que diversos processos de transformação causam um aumento na assinatura isotópica do mercúrio. Em meios aquáticos o mercúrio pode ser transformado por processos biológicos e não biológicos tal como oxidação/redução e metilação/desmetilação, entre outros. Em geral, processos de oxidação e de metilação provocam um incremento em Δ199Hg enquanto que processos de redução e desmetilação provocam uma diminuição no valor deste parâmetro. Neste trabalho, a composição isotópica do mercúrio foi determinada em diferentes níveis tróficos do ecossistema existente em alguns lagos Aquitâneos, para os quais também foram determinados a concentração total de mercúrio, a composição isotópica do carbono e azoto (δ13C e δ15N) e o cálculo das posições tróficas a partir da composição isotópica do azoto. Os valores de δ202Hg variaram de -0,93‰ a 0,60‰. Os 2 maiores lagos (Hourtin-Carcans e Casaux-Sanguinet) apresentaram valores positivos enquanto que nos 2 lagos de menores dimensões (Lacanau e Parentis-Biscarrosse) os valores foram negativos. No geral, os valores de δ202Hg variam muito pouco mas verifica-se uma ligeira tendência crescente de amêijoa-asiática (Corbicula flumínea) para lagostim-vermelho (Procambarus clarkii) para brema (Abramis brama) para lúcio (Esox Lucius) para perca (Perca fluviatilis) para lucioperca (Sander lucioperca). O rácio ∆199Hg/∆201Hg obtido foi aproximadamente 1.3, o que indica que o mercúrio bioacumulado nestas amostras resulta de reações de desmetilação. Os valores do MIF apresentaram uma variação superior (0,11‰ a 3,84‰). A Corbicula fluminea apresenta valores inferiores aos encontrados em Procambarus clarkii e Abramis brama. Esox Lucius, Perca fluviatilis e Sander lucioperca apresentaram os valores superiores de ∆199Hg. Para caraterizar melhor a transferência de mercúrio ao longo das cadeias alimentares existentes nestes lagos, é necessária a realização de estudos posteriores com uma amostragem mais completa.

碩士<br>中央警察大學<br>鑑識科學研究所<br>100<br>The purpose of this research is trying to use isotope ratio mass technique (IRMS) to trace the source of abused drugs and gunpowders. Abused drugs include anaesthetic, stimulant, hallucinogen and sedative material. This research focused on ketamine, which is one of the date rape pills. The amount of ketamine that ferreted out by police is increasing yearly. It indicated that ketamine was abused seriously, so it is important to trace the source of ketamine. It is illegal for a person to own or to sell a gun in Taiwan, but many gangsters possess guns secretly. Therefore, there are many shooting fight cases occurred and caused series injuries. These showed that it is important to trace the source of gunpower. GC-isotope Ratio Mass Spectrometry can be used in analysis the ratio of stable isotope element in compounds. The carbon in specific- compound from the same source will have the similar isotope ratio. In this study, we combined the gas chromatography with isotope ratio mass spectrometry to analyze the carbon isotope ratio of ketamine that were from the court. The result showed that δ13C values of 19 ketamine samples can be classified into four groups. It indicated that the ketamine samples might be sold out from four different sources. Gunpowder was composed of complicated and some thermal unstable components. Among them, δ13C values of the two thermal stable compounds: Ethyl Phthalate and DBP (Dibutyl Phthalate) were analyzed by GC-IRMS. The data shown that δ13C value of single compound from different sample is not distinguishable, however, we can differentiate them by Cluster Analysis of δ13C value of these two components. Few samples that can’t be distinguished by this method can be accomplished by analysis of the GC chromatogram that was obtained in the GC/IRMS running.

Tese no âmbito do Doutoramento em Biologia Experimental e Biomedicina, ramo de Biotecnologia e Saúde, orientada pelo Doutor John G. Jones e coorientada pela Doutora Eugenia Carvalho e pelo Professor Doutor João Ramalho Santos, apresentada ao Instituto de Investigação Interdisciplinar da Universidade de Coimbra.<br>Humans evolved in environments where calorie supply and availability were scarce and unpredictable, thereby developing mechanisms that allowed them to store nutrients during times of plenty for utilization in times of need. In a remarkably short time, humanity has managed to profoundly change the environment from which it originally evolved. Nowadays, food is easily available in most societies and is frequently consumed in excess. At the same time, caloric requirements have diminished as lifestyle has become more sedentary. As a consequence, obesity and associated diseases became endemic in the last fifty years and have currently taken a tremendous toll on many aspects of society. Insulin resistance is considered a sine qua non for the development and progression of most common metabolic diseases. Although insulin resistance induces a multi-organ pathological response, disruption of insulin regulation has different manifestations on the various insulin- sensitive tissues of an organism. The liver plays a central role in systemic glucose and lipid homeostasis and a well-coordinated hepatic metabolism is essential for the overall metabolic health. Hepatic insulin resistance is an important element in the pathogenesis and precipitation of metabolically altered states and many therapeutic approaches target the liver specifically. Insulin governs metabolic fluxes in the liver by stimulating anabolic pathways during states of nutrients abundance, mostly by prompting glycogen and lipid synthesis. Thus, impaired glycogen deposition and aberrant lipid production are major hallmarks of the insulin-resistant liver. This thesis is constructed around three sets of animal model studies that applied stable isotope tracers coupled with Nuclear Magnetic Resonance (NMR) analysis of their enrichment of hepatic glycogen and/or lipids. The objectives were to enhance our understanding on the impact of diet, drugs and genetic manipulation - mediated in part by their effects on hepatic insulin actions - on hepatic glycogen and lipid metabolism. In Study 1, we combined the use of deuterated water (2H2O) with 13C uniformly labeled fructose and glucose to study the effect of high-fructose corn syrup, a very much investigated nutrient in the context of metabolic diseases, on hepatic glycogenesis in mice fed a high-sugar diet for a prolonged period of time. We observed that the fructose and the glucose components of the sugar administered to the animals under study contributed equally to hepatic glycogenesis. Moreover, overall glycogen synthesis and glycogen deposition via direct pathway were not compromised after chronic high- sugar feeding in mice. In Study 2, H2O was employed for the first time to examine the effects of second-generation antipsychotics, widely used medications associated with detrimental metabolic side effects, on hepatic metabolic fluxes in mice. Despite some early systemic metabolic alterations, we found intact hepatic glycogen and lipid fluxes in animals treated with second-generation antipsychotics over a period of seven months. In Study 3, H2O was utilized to characterize the hepatic metabolism of PTP-1B knockout mice, an animal model of insulin hypersensitivity. We observed reduced glycogen concentration and lipid synthetic fluxes in PTP-1B knockout mice, an outcome that contradicted our expectations from a mouse model of hypersensitivity to insulin.<br>Os seres humanos evoluíram em ambientes onde o provimento e a disponibilidade calórica eram escassos e imprevisíveis, por isso desenvolveram mecanismos que lhes permitiram armazenar nutrientes durante tempos de abundância para serem utilizados em tempos de necessidade. Num espaço de tempo notavelmente curto, a humanidade conseguiu mudar profundamente o ambiente do qual originalmente evoluiu. Nos nossos dias, os alimentos estão facilmente disponíveis na maioria das sociedades e frequentemente são consumidos em excesso. Ao mesmo tempo, as exigências calóricas diminuíram à medida que o estilo de vida se tornou mais sedentário. Como consequência, a obesidade e as doenças associadas tornaram-se endémicas nos últimos cinquenta anos e atualmente têm tido um tremendo impacto em muitos aspetos da sociedade. A resistência à insulina é considerada sine qua non para o desenvolvimento e progressão das doenças metabólicas mais comuns. Embora a resistência à insulina induza uma resposta patológica multi-orgão, a rutura da regulação da insulina resulta em manifestações diferentes nos vários tecidos dependentes da insulina de um organismo. O fígado desempenha um papel central na homeostase da glicose sistémica e lipídica, e um metabolismo hepático bem coordenado é essencial para a saúde metabólica geral. A resistência hepática à insulina é um elemento importante na patogénese e no rápido aparecimento de estados metabolicamente alterados e muitas abordagens terapêuticas visam especificamente o fígado. A insulina rege os fluxos metabólicos no fígado, estimulando as vias anabólicas durante estados de abundância de nutrientes, principalmente por promover a síntese de glicogénio e de lípidos. Assim, alterações no armazenamento de glicogénio e uma síntese lipídica aberrante são os principais sinais de um fígado resistente à insulina. Esta tese é construída em torno de três conjuntos de estudos em modelos animais nos quais foram utilizados marcadores com isótopos estáveis, combinados com a análise do seu enriquecimento no glicogénio hepático e/ou lípidos por Ressonância Magnética Nuclear (RMN). Os objetivos foram o aprofundamento da nossa compreensão sobre o impacto da dieta, drogas e manipulação genética - mediado em parte pelos seus efeitos sobre a ação da insulina no fígado - no metabolismo hepático do glicogénio e lipídico. No Estudo 1, combinámos a utilização da água deuterada (2H2O) com frutose e glicose uniformemente marcadas com 13C para estudar o efeito do xarope de milho com elevado teor de frutose, um nutriente muito investigado no contexto de doenças metabólicas, na glicogénese hepática em murganhos alimentados com uma dieta rica em açúcar durante um período prolongado de tempo. Observámos que a frutose e a glicose, componentes do açúcar administrado aos animais estudados, contribuíram de igual forma para a glicogénese hepática. Além disso, a síntese e o armazenamento do glicogénio pela via direta não ficaram comprometidos nos murganhos após uma alimentação crónica com elevado teor de açúcares. No Estudo 2, empregámos a 2H2O para examinar os efeitos de medicamentos antipsicóticos de segunda geração nos fluxos metabólicos hepáticos em murganhos. Apesar de algumas alterações metabólicas sistémicas precoces, verificámos que os fluxos de glicogénio e de lípidos hepáticos se encontravam intactos naqueles animais tratados com antipsicóticos de segunda geração durante um período de sete meses. No Estudo 3, foi utilizada a 2H2O para caracterizar o metabolismo hepático em murganhos knockout para PTP-1B, um modelo animal de hipersensibilidade à insulina. Observámos uma redução da concentração de glicogénio e dos fluxos de síntese lipídica nos murganhos knockout para PTP-1B, um resultado que contradisse as nossas expetativas para um modelo de murganho de hipersensibilidade à insulina.

Nitrate (NO3) contamination in agricultural watersheds is a widespread problem that threatens local drinking supplies and downstream ecology. Dual isotopes of NO3- (d15N and d18O) have been successfully used to identify sources of NO3 contamination and nitrogen (N)-cycle processes in agricultural settings. From 1998 to 2000, tile drainage and stream waters at the Strawberry Creek Catchment were sampled for NO3- concentration and isotopes. The results suggest that tile NO3 were mainly derived from soil organic matter and manure fertilizers, and that they were not extensively altered by denitrification. NO3- concentrations and isotopes in the stream oscillated between the influence of tile inputs, during periods of higher basin discharge, and groundwater inputs, during low basin discharge. The affect of denitrification was evident in stream NO3- samples. Sources and processes of dissolved NO3- and N2O were explored using concentrations and stable isotopes during the 2007 Springmelt and 2008 mid-winter thaw events. Tiles are a source of NO3- to the stream during both events and concentrations at the outflow are above the 10 mg N/L drinking water limit during the 2008 mid-winter thaw. The stream was a source of N2O to the atmosphere during both events. d15N and d18O of N2O reveal that N2O is produced from denitrification during both events. d18O:d15N slopes measured in N2O were due to the influence of substrate consumption (tiles) and gas exchange (stream). The stable isotopes of dissolved NO3- and N2O were also characterized during non-melt conditions (October 2006 to June 2007 and Fall 2007) at the Strawberry Creek catchment. Again, the purpose was to determine the sources and processes responsible for the measured concentrations and isotopic signatures. The isotope data suggests that N2O was produced by denitrification. Furthermore, NO3- consumption and gas exchange altered the original N2O signature. Isotopic distinction between soil gas N2O and dissolved N2O is suggestive of different production mechanisms between the unsaturated and saturated zones. Since the range of dissolved N2O isotopes from the Strawberry Creek catchment are relatively constraned, definition of the local isotopic signature of secondary, agricultural N2O sources was possible.

Understanding and quantifying terrestrial salt cycling is central to scientific fields such as sedimentary geology, mineral exploration, water resources, palaeontology, atmospheric chemistry and limnology. Dissolved chlorine and bromine concentrations have been utilised for decades as individual tracers or as a ratio to trace geochemical processes in saline environments. The stable isotope variations of these two elements have also been found to be useful for understanding and quantifying geochemical processes. However, both hydrogeochemical techniques could benefit from being applied in new environments and the collection of further data on a local and continental scale, as well as developing quantitative methods to provide further value to their use. This thesis presents findings based on theoretical analysis, large-scale monitoring and a targeted field investigation to improve the understanding of how chlorine and bromine can be utilised as tracers of terrestrial salt cycling. Firstly, bench-top salt dissolution experiments were used to verify a previously established quantitative mixing model that utilises chloride/bromide ratios to correct chloride- or bromide-based tracer methods for other chloride sources. The results show that the model can predict the percentage of alternate salt sources accurately after analytical and endmember uncertainties are considered. The results are used to extend the understanding of the uncertainties and sensitivities of the mixing models, providing scientists with a guide to which environments and scenarios the mixing model would be most appropriate. The mixing model correction provides a useful and cheap method for scientists to improve their use of chloride- or bromide-based tracer techniques in catchment studies. Secondly, a continental-scale dataset of wet deposition compositions spanning six and half years was analysed to identify spatial and temporal trends in chloride/bromide ratios. A recently developed imputation algorithm was applied to estimate the high proportion of censored bromide values, as well as the other eight analytes, based on the multivariate relationships of nine analytes. Chloride/bromide ratios of wet deposition decrease with distance inland following a logarithmic regression. The observations provide further confidence in the findings presented in previous studies that have shown that chloride/bromide ratios systematically decrease with increasing distance from the coast. Lastly, chlorine and bromine tracer techniques were applied in a case study of the Lake George Basin, NSW, to trace modern salt cycling proximal to a saline lake, and to investigate how hydrogeochemical signatures can elucidate palaeohydrologic processes. The Lake George Basin was chosen as the field site because of its long, near-continuous sequence of Cenozoic lake sediments, and its complex salt cycling regime. The chlorine- and bromine-based tracer methods, in combination with other geochemical information, have provided a better understanding of the modern salt cycling regime within the catchment, and have also provided useful constraints on the timing of the recession of the mega-lake that existed in the basin during the last glacial maximum. This study also illustrated the utility of chlorine- and bromine-based tracer methods to delineate salt cycling processes in saline lake environments.

No<br>The environmental contexts of the karstic hominin sites in South Africa have been established largely by means of faunal associations; taken together these data suggest a trend from relatively closed and more mesic to open, drier environments from about 3 to 1.5 Ma. Vrba argued for a major shift within this trend ca. 2.4¿2.6 Ma, an influential proposal that posited links between bovid (and hominin) radiation in Africa and the intensification of Northern Hemisphere Glaciation. Yet faunal approaches often rely on habitat and feeding preferences of modern taxa that may differ from those of their extinct predecessors. Here we explore ways of extending 13C/12C data from fossil mammals beyond denoting ¿presence¿ or ¿absence¿ of C4 grasses using the evolution of open environments in South Africa as a case study. To do so we calculated the relative proportions of C3-, mixed-, and C4-feeding herbivores for all the hominin sites for which we have sufficient data based on 13C/12C analyses of fossil tooth enamel. The results confirm a general trend towards more open environments since 3 Ma, but they also emphasize a marked change to open grassy habitats in the latest Pliocene/early Pleistocene. Mean 13C/12C for large felids also mirrored this trend.

In April 2010, approximately 4.9 million barrels of oil were accidentally released into the Gulf of Mexico during the Deepwater Horizon Macondo Mc252 Oil Spill. Some of the surface oil was carried by prevailing winds and currents and reached the coast of Louisiana impacting marsh and marine ecosystems. One and a half years after this incident, a set of oiled marsh samples (2 grab samples) coupled with nearby subtidal and intertidal cores (12 cores) were collected from Barataria Bay, Louisiana to determine the probable source of petroleum residues present and to characterize the chemical composition of the oil. Plus, pre-spill core which was collected from Barataria Bay in 2007 was analyzed to identify the background hydrocarbon composition of the area. Polycyclic aromatic hydrocarbons (PAH), total petroleum hydrocarbons (TPH), biomarker, and stable carbon isotope compositions of selected samples were detected using a GC-MS and an elemental analyzer Conflo system coupled to a DeltaPlusXP isotope ratio mass spectrometer. The comprehensive chemical data allowed us to classify the pre and post-spill samples into 4 Groups. According to this classification, Group 1 and Group 2 samples had the highest concentrations of petroleum-derived hydrocarbons. Group 3 and background samples, on the other hand, was dominated by biogenic signatures. Although a direct connection between the detected and spilled Macondo oils results are complicated due to confounding factors (e.g., already present hydrocarbons and weathering processes), our biomarker data indicates that both oils have similar signatures. This close genetic relationship was also identified by stable carbon isotope analysis. The impact of the Macondo Mc252 Oil Spill in Barataria Bay appears to be limited to areas closer to the source. The oil has undergone moderate weathering and has penetrated into, the at least, the top 9 cm sediments. Additionally, to examine the decadal-scale history of sedimentation in these marshes, a sediment core was analyzed for the radioisotope 137Cs. The observed sedimentation rate of 0.39 cm/yr shows that oil pollutant input into Barataria Bay has been ongoing for at least 50-60 years.

Dissertação de Mestrado em Ecologia apresentada à Faculdade de Ciências e Tecnologia<br>Em geral, estudos no âmbito da ecologia de procura de alimento e da dieta de predadores focam-se essencialmente no estudo da quantidade de alimento, em vez da sua qualidade. Relativamente aos ácidos gordos presentes na dieta, estudos prévios sugerem que a sua qualidade é tão, ou mais, importante que a quantidade ingerida. Ácidos gordos são considerados nutrientes essenciais tendo em conta a sua importância para o normal funcionamento e desenvolvimento saudável dos indivíduos, ainda que estes compostos não sejam vulgarmente biosintetizados pelos predadores. Desta forma, consumidores dependem da disponibilidade de ácidos gordos no ambiente para obter alimento de qualidade. Contudo, esta disponibilidade ambiental e o seu potencial efeito limitador nos predadores são ainda pouco conhecidos, especialmente considerando ambientes de baixa produtividade, como é o caso das regiões tropicais. Neste trabalho apresentamos um estudo preliminar de manipulação da qualidade alimentar de crias, através da suplementação de ómega-3, num contexto de condições selvagens de uma espécie tropical de ave marinha (i.e. cagarra-de-Cabo-Verde, Calonectris edwardsii), com o objetivo de melhor compreender a influência dos ácidos gordos no desenvolvimento das crias e na ecologia de forrageamento dos pais. Em geral, os resultados apresentados não demonstraram uma influência aparente da suplementação de ómega-3 no desenvolvimento das crias, nomeadamente no crescimento, na condição aquando da saída do ninho ou no seu estado fisiológico. Contudo, os pais pareceram responder, a um certo nível, à condição das crias, tendo em conta as variações no esforço de forrageamento, refletido também nas análises de dieta dos pais (i.e. isótopos estáveis e ácidos gordos). Assim, concluímos que os pais tendem a adotar diferentes estratégias de forrageamento tendo em conta a condição da cria. Por último, os nossos resultados reforçam o facto deste predador tropical apresentar uma alta plasticidade e grande adaptabilidade durante o forrageamento em cenários exigentes. Contudo, é ainda necessária investigação futura que integre dados ambientais, de maneira a possibilitar a caracterização da paisagem marinha disponível para os predadores durante o forrageamento.<br>Ecology studies on foraging ecology and predators’ diet have generally focused on food quantity over quality. In terms of fatty acid composition, previous studies have suggested food quality to be as important, if not more, than food quantity. Fatty acids are considered essential nutrients given the importance for normal functioning and healthy development of individuals, even though fatty acids are not usually biosynthesised endogenously by predators. Therefore, consumers depend on the availability of fatty acids on the environment to obtain quality food. However, this environmental availability and its potential limit effect on predators are still uncertain, especially when considering environments with lower profitability, as is the case of tropical regions. Here, we suggest a preliminary field study on food quality manipulation of free-living chicks, through omega-3 supplementation, considering natural conditions of a tropical seabird species (i.e. Cape Verde shearwater, Calonectris edwardsii), in order to better understand the influence of essential fatty acids on chick development and, subsequently, on parents’ foraging ecology. Overall, our results showed no apparent influence of the omega-3 supplementation on chick development, regarding growth, fledging condition or physiological status of chicks. However, parents seem to respond at some level to chicks’ condition, considering the variations on the foraging effort performed by parents, reflected as well on diet assessments of these adults (i.e. stable isotopes and fatty acids profiles). Thus, we conclude parents tend to adopt different foraging strategies regarding chick condition. At last, our results reinforce the fact of this tropical top predator presents a high plasticity and great adaptability while foraging under challenging scenarios, as previously described for the Cape Verde shearwater. Nevertheless, further research is still required, especially regarding environmental conditions in order to characterize the foraging marine landscape available to predators.