The Common tern (Sterna hirundo) is considered a sentinel wildlife species for monitoring mercury (Hg) and other contaminants within the St. Lawrence River Cornwall/Massena Areas of Concern (AOC). Here, I investigate the relationship between Hg bioaccumulation and diet using stable isotopes of carbon (δ13C) and nitrogen (δ15N) in adult and chick Common terns from three colonies along a 160 km transect of the upper St. Lawrence River. The foraging range of the colony furthest downstream (EMC) includes both the Massena and Cornwall AOC’s while the two upstream colonies (213 and Ice) are more removed from known point sources of Hg. I also sampled winter- and summer-grown breast feathers to compare diet and Hg exposure on the terns’ breeding ground vs. the terns’ wintering grounds. Hg exposure in summer-grown feathers was significantly higher than Hg exposure in winter grown feathers. Stable carbon (δ13C) and nitrogen (δ15N) isotopes revealed a switch from a marine-based diet during the winter months to a freshwater-based diet on the breeding grounds. Among colonies in summer-grown and chick feathers, the only significant difference in total mercury (THg) exposure was found in chick feathers where Hg was significantly lower at 213 than Ice – both of which are upstream from the AOC’s. However, THg was negatively correlated with δ13C in both winter and summer feathers, and the most parsimonious multi-regression model for winter and summer feathers indicated that δ13C explains 24 and 25% of the variation in Hg exposure, respectively. This suggests terns foraging offshore bioaccumulate more Hg than individuals foraging inshore or in freshwater (winter feathers), and that during the breeding period, terns foraging in pelagic habitats bioaccumulate more Hg than terns foraging in littoral habitats (summer feathers). For the upper St. Lawrence River, these results provide strong evidence that foraging habitat is more important than colony location in determining Hg exposure in a top trophic consumer. / Thesis (Master, Biology) -- Queen's University, 2013-06-01 19:35:59.665

No description available.

The O and H isotopic composition of minerals can provide valuable information on the source of the fluids and temperature of mineral precipitation. To obtain accurate isotopic measurements using SIMS, it is important to select chemically similar standards and samples to correct for both matrix effects and instrumental mass fractionation (IMF), collectively termed instrumental mass bias (IMB). For certain mineral groups (e.g. tourmalines), there are large variations in major element composition between species. This study uses three of these tourmaline species (schorl, dravite, and elbaite) to construct calibration curves to correct for IMB during SIMS analysis of O and H isotopes. I have applied my technique to analyses of tourmalines from the Wollaston Group, Athabasca region, Saskatchewan to test my method, and I have calculated the O and H isotopic composition of the fluids that formed these tourmalines. / October 2016

No description available.

Master of Science / Department of Geology / Saugata Datta / To understand ambient nitrate dynamics in an unmanaged grassland environment, the stable isotope chemistry of various substrates at the Konza Prairie Biological Station were studied. Sediments consisted of alluvium, loess and bedrock materials are mostly limestone and shale. To gain a better understanding of the biogeochemistry of N cycling in this unmanaged grassland, 34 water samples have been collected along a full stretch of the major onsite creeks (Kings and Shane Creeks). These samples have been analyzed for δD, δ18O, and δ15N to determine the manner by which water allows nitrates to be leached into sediment, and to determine if additional nitrate is contributed from weathering of the bedrock. The anion chemistry of the waters show the presence of bicarbonates, sulfates, chlorides, nitrates, and fluorides. Although an obvious correlation among the anions is not present, data shows high alkalinity content due to the presence of shallow bedrock that is continuously being weathered. Using a hydraulic geoprobe, sediment cores were collected up to 8 ft deep using 2 ft core liners adjacent to the creeks to study δ15N and δ13C spatial variation of the sediments. This research also indicated the presence of C3 and C4 derived soil organic carbon with the latter being dominant. There is also an approximate 1:9 correlation between the total nitrogen and carbon content of these core sediments including NO3 and NH4 that are mostly concentrated in the upper 2 – 4 ft of the sediment profile. The results of this study provide a broader context for ambient nitrate cycling in unmanaged grassland and a baseline comparison for nitrate levels in surrounding agricultural lands.

Entre 2003 et 2010, dans la région centrale nommée X de la catacombe des Saints Pierre-et-Marcellin à Rome, a été découvert et en partie fouillé un ensemble de sépultures plurielles inédites (Ier-IIIe s. ap. J.-C.) contenant plusieurs centaines d’individus, lesquels ont été inhumés selon des pratiques funéraires singulières à la suite d’un épisode de surmortalité de nature probablement épidémique. Pour appréhender l’histoire de vie (alimentation et mobilité) de ces défunts et rediscuter sur la base d’éléments nouveaux certaines hypothèses préalablement établies, nous avons mené dans le cadre de ce travail une approche archéo-biogéochimique multi-proxy (14C, δ13C, δ15N, δ18O et 87Sr/86Sr) et multi-tissulaire (émail, os, cheveu) sur un échantillon de 130 individus issus de six différentes chambres. Nous avons dans un premier temps vérifié l’intégrité biochimique et isotopique des fractions minérales (phases carbonatées) et organiques (phases collagénique et kératinique) des échantillons à partir d’indicateurs classiques mesurés en routine (%Col, %C, %N, C/N, PCO2 et PCO2/Masse) et par spectroscopie IRTF (IRSF, CO3/PO4 et AmideI/PO4) et par une approche innovante consistant en des datations 14C sur couples collagène-apatite pour valider le signal isotopique des fractions minérales. Nos résultats mettent en évidence des différences extrêmes de préservation de toutes les phases. La trajectoire diagénétique des échantillons n’est toutefois pas aléatoire mais dépendante des conditions environnementales et taphonomiques différant entre les petites et les grandes chambres. En outre, nous avons pu démontrer qu’en dépit de fortes recristallisations et d’échanges isotopiques avec l’environnement sépulcral, les phases carbonatées possèdent un signal isotopique biogénique non altéré. Nous avons dans un second temps reconstruit les régimes alimentaires des individus en nous appuyant sur des référentiels de comparaisons robustes ainsi que divers modèles interprétatifs (mono-proxys versus multi-proxys ;qualitatifs versus quantitatifs), lesquels ont été dans certains cas adaptés au besoin de notre étude. D’une façon générale, nos résultats montrent que l’essentiel des individus a eu accès à un régime alimentaire type fondé sur la triade Céréales C3/Viande C3/Poisson marin. Ce régime alimentaire type n’est toutefois pas exclusif, certains individus (n = 13) ayant consommé de façon occasionnelle d’autres catégories de ressources tels que du poisson dulcicole ou des céréales C4. Nos résultats révèlent que les changements d’alimentation au cours de la vie sont relativement limités. Par ailleurs, cette population se singularise sur un plan strictement alimentaire au regard des autres populations contemporaines romaines pour lesquelles des valeurs isotopiques sont publiées. Nous avons dans un troisième temps étudié les schémas de mobilité des individus en nous fondant sur une approche rigoureuse de nos données et sur des référentiels de comparaison les plus exhaustifs possible ainsi qu’en tenant compte de biais ordinairement éludés (faits culturels, influence du climat et erreurs associées aux équations de conversion). Nos résultats mettent en lumière qu’a minima 23 % (n = 30) des individus étudiés sont migrants. Ces derniers ne se distinguent toutefois pas de par leur alimentation des résidents romains. Nous avons pu montrer en outre que ces migrants ont eu des trajectoires de vie complexes et hétérogènes et que trois schémas de mobilité distincts les caractérisent. Notre population ne se différencie pas en termes de taux de migrants des autres populations romaines pour lesquelles des données isotopiques sont disponibles. Elle se distingue en revanche par son cosmopolitisme avec des origines pour les migrants des plus diverses :Europe, Afrique, Arabie et Asie mineure. Enfin, nous avons pu démontrer en nous appuyant sur nos interprétations alimentaires et sur diverses données historiques que cette population n’est pas homogène sur un plan socio-économique. De même, au regard de notre étude de la mobilité et des données archéologiques, nous avons pu avancer l’hypothèse que certains aspects des pratiques funéraires mises en évidence sur le site pouvaient déjà être utilisés à Rome avant l’arrivée des migrants. En outre, nous avons pu rediscuter de l’antériorité supposée des sépultures en nous fondant sur les nouvelles datations 14C et la mise en évidence d’une consommation non négligeable de poisson. Sur la base de tous ces éléments, nous avons pu proposer l’existence d’un lien mystique (i.e. religieux) reliant ces individus. / info:eu-repo/semantics/nonPublished

No description available.

Nutrient inputs from productive marine environments have been shown to directly and indirectly subsidise primary producers and consumers in terrestrial ecosystems (e.g. Polis and Hurd 1995; 1996; Anderson and Polis 1998; 1999). But does this theory hold true on islands surrounded by oligotrophic waters, which account for a significant proportion of the marine environment? The aim of the present study was to examine the applicability of the spatial subsidisation hypotheses proposed by Polis and his co-authors to an oligotrophic system in south-western region of Western Australia. These aims were achieved by comparing soil and plant nutrients, and the nitrogen stable isotope signatures of soil, plants, detritus and invertebrates in areas with (islands) and without (mainland sites) inputs from seabirds. In addition, the responses of plant nutrients and vegetation assemblages to guano additions were examined in a controlled field experiment.

We investigate the silicon (Si) cycle in the Southern Ocean through two isotopic approaches: (1) 30Si-incubation experiments and (2) natural silicon isotopic composition (ä30Si). 30Si-spiked incubation allows to discriminate the short-term (~ 1 day) net Si-uptake flux in bSiO2 production and dissolution. ä30Si of both biogenic silica and dissolved silicon integrates at seasonal/annual scale bSiO2 production or dissolution and mixing. (1) A new mass spectrometer method (HR-SF-ICPMS) has been developed for 30Si-isotopic abundance measurements. This methodology is faster and easier than the previous available methodologies and has the same precision. A complete set of incubation was coupled with parallel 32Si-incubations and the two methodologies give not significantly different bSiO2 production rates. In the Southern Ocean, especially in the southern Antarctic Circumpolar Current, the large silicic acid concentration degrades the sensitivity of the method with Si dissolution fluxes staying generally below the detection limit. In contrast, the 28Si-isotopic dilution was sensitive enough to assess low biogenic silica dissolution rates in silicic acid poor waters of the northern ACC. We show that large accumulation of detrital dissolving biogenic silica after productive period implies really efficient silicon loop with integrated (euphotic layer) dissolution:production ratio equal or larger than 1. (2) We largely expand the silicic acid isotopic data in the open ocean. Relatively simple mass and isotopic balances have been performed in the Antarctic Zone and have allowed to apply for the first time ä30Si in a quantitative way to estimate regional net silica production and quantify source waters fueling bSiO2 productivity. We observe that at the end of the productive period as suggested with 30Si-incubation, large accumulation of detrital biogenic silica in the surface waters increase the D:P ratio and subsequently dampens the bSiO2 production mediated isotopic fractionation with residual biogenic silica carrying heavier ä30Si than expected. Seasonal isotopic evolution is simulated and seems in agreement with our observations. These simulations strongly suggest working with non-zero order equations to fully assess the seasonal expression of the different processes involved: mixing, uptake, dissolution. Si-isotopes are also tracking the origin and fates of the different ACC pools across the Southern Ocean meridional circulation. Moreover during the circumpolar eastward pathway, the bSiO2 dissolution in deep water decreases the corresponding ä30Si values and this imprint is further transmitted via the upper limb of the meridional circulation in the intermediate water masses.

Tracking migratory movements of birds between breeding and wintering areas is important for both theoretical and conservation purposes. In particular, information about linkages between stages of the annual cycle (i.e., migratory connectivity) is essential for identifying factors and processes limiting population sizes of birds. Further, this information is necessary for testing assumptions and hypotheses about the evolution of avian migratory patterns. Here, I used stable hydrogen isotope (δD) analyses of tissues representing different periods and geographic regions of the annual cycle of white-throated sparrows, Zonotrichia albicollis, to provide new information on spatial and temporal linkages between stages of the annual cycle of this species. To achieve this objective, I sampled white-throated sparrows during spring and fall migration of 2002 and 2003 at a key staging ground for North American migratory birds located at Delta Marsh, Manitoba. Based on evaluations of the correspondence between δD values of feathers, claws, and cellular portions of blood of migrants, I determined that δD values of claws and blood cells were not suitable for estimating wintering origins of individuals captured en route to breeding areas. However, δD values of head feathers grown on wintering areas and tail feathers grown on breeding areas corresponded to values expected for feathers grown in broad areas within the wintering and breeding range of the species, respectively. The δD values of feathers showed no relationship between estimated breeding or natal and wintering latitudes of white-throated sparrows. However, band-encounter analyses indicated a clear eastwest segregation of populations across Canada, a finding that suggests that this species has a parallel migration system. Temporally, all components of the breeding populations migrated together during spring migration. However, as expected, white-throated sparrows exhibited sex-biased differential timing of spring arrival and latitude of wintering origin. Consistent with several other differential migrants, female white-throated sparrows arrived later and originated from more southern latitudes. There was also a negative relationship between wintering latitude and arrival dates of individuals during the second spring of the study. The existence of this relationship is a key assumption of differential migration hypotheses that had not been previously validated. Furthermore, since timing of arrival at breeding areas is critical to establishing high-quality territories and pair bonds, relationships between wintering latitude and arrival date of individuals could have important carry-over effects to reproduction. Based on standard body condition indices, white-throated sparrows migrating longer distances to reach breeding areas were not in poorer body condition than those migrating shorter distances. Thus, the cost of migrating longer distances does not appear to affect pre-breeding body condition, a parameter known to be linked with reproductive success.