Woody plant invasion of grasslands is prevalent worldwide, but the biogeochemical consequences of this vegetation shift remain largely unquantified. In the Rio Grande Plains, TX, grasslands and savannas dominated by C4 grasses have undergone succession over the past century to subtropical thorn woodlands dominated by C3 trees/shrubs. To elucidate mechanisms of soil organic carbon (SOC) and soil total N (STN) storage and dynamics in this ecosystem, I measured the mass and isotopic composition (δ13C, δ15N) of C and N in whole-soil and soil size/density fractions in chronosequences consisting of remnant grasslands (Time 0) and woody plant stands ranging in age from 10-130 years. Rates of SOC and STN storage averaged 10-30 g C m-2yr-1 and 1-3 g N m-2yr-1, respectively. These accumulation rates increased soil C and N pools 80-200% following woody encroachment. Soil microbial biomass (SMB-C) also increased after woody invasion. Decreasing Cmic/C org and higher qCO2 in woodlands relative to grasslands suggests that woody litter is of poorer quality than grassland litter. Greater SOC and STN following woody invasion may also be due to increased protection of organic matter by stable soil structure. Soil aggregation increased following woody encroachment; however, most of the C and N accumulated in free particulate organic matter (POM) fractions not protected within aggregates. Mean residence times (MRTs) of soil fractions were calculated based on changes in their δ13C with time after woody encroachment. Free POM had the shortest average MRTs (30 years) and silt+clay the longest (360 years). Fine POM had MRTs of about 60 years, reflecting protection by location within aggregates. δ15N values of soil fractions were positively correlated with their MRTs, suggesting that higher δ15N values reflect an increased degree of humification. Increases in SOC and STN are probably being sustained by greater inputs, slower turnover of POM (some biochemical recalcitrance), and protection of organic matter in aggregates and association with silt and clay. Grassland-to-woodland conversion during the past century has been geographically extensive in grassland ecosystems worldwide, suggesting that changes in soil C and N dynamics and storage documented here could have significance for global C and N cycles.

The common snook, Centropomus undecimalis, is an estuarine dependent sport fish that relies upon subtidal wetlands as nursery habitat. Despite the economic and recreational significance of this species, there are portions of its life history and biology that are poorly understood, particularly its early life history. Understanding juvenile snook use of wetland habitats is crucial given the rapid loss and degradation of these areas to anthropogenic impacts. Young-of-the-year snook were collected in pond and creek habitats of a single wetland system to assess early life ecology and habitat use. Proxies of habitat quality were used to determine which habitats within a small spatial scale were optimal for young-of-the-year snook recruitment. Results indicated that even on a very small spatial scale, differences in habitat use were apparent, whereby smaller snook initially recruited to pond habitats and dedicated all energy into growth. Upon reaching a size of at least 40 mm SL snook began an ontogenetic habitat shift and moved to the tidal creek habitat. There, snook began to store energy, thus becoming more robust. Stable carbon and nitrogen isotopic analyses confirmed the ontogenetic habitat shift and revealed that snook have high site fidelity within the pond and creek habitats. Stable isotopic analysis also indicated that YOY snook appear to feed at the third trophic level consuming neonatal poecilliids and shrimp, and ultimately rely on benthic microalgae and particulate organic matter as basal resources. Results of this study advance the knowledge of juvenile snook ecology and will likely have implications for resource managers who are responsible for preserving and restoring wetland habitats upon which juvenile snook rely.

Changes in freshwater inputs due to water diversions and increased urbanization may alter the function and properties of estuarine ecosystems in South Texas. Freshwater and nitrogen inputs from the Mission and Aransas rivers to the federally designated Mission-Aransas National Estuarine Research Reserve (Mission-Aransas NERR) have received considerable attention in the past few years. However, freshwater inputs from two rivers (the San Antonio and Guadalupe rivers) that combine and drain into a neighboring bay (San Antonio Bay) may also provide a substantial nitrogen source to Aransas Bay, which is within the boundaries of the Mission-Aransas NERR. In order to study the influence of the San Antonio and Guadalupe rivers, an oyster species, Crassostrea virginica, was chosen to provide time-integrated information about freshwater contribution as a nitrogen source within the bays. Chapter One addresses variations in isotope values ([delta]¹⁵N and [delta]¹³C) in oyster adductor muscle tissue from 2009-2011 along a sampling transect from the head of San Antonio Bay through Aransas Bay. Stable carbon isotope values increased linearly from approximately -25 % to -17 %, while stable nitrogen isotope values decreased from approximately +16 % to +10 % along this transect. The patterns in stable carbon and nitrogen isotope values are consistent with substantial mixing of river-supplied water and nitrogen from San Antonio Bay into Aransas Bay. Variations in nitrogen isotopic signature between periods of sustained drought and flood conditions were relatively small, suggesting that riverine nitrogen contributions were similar regardless of the amount of freshwater inflow observed during the time frame of this study. Chapter Two addresses the isotopic equilibration time for adult oyster adductor muscle tissue using a year-long transplant experiment (November 2010-November 2011). Full representation of ambient water isotopic composition in oyster adductor muscle tissues was determined to occur roughly a year after transplant. Oyster adductor muscle could therefore be useful for long-term monitoring of nitrogen contribution from freshwater sources, and would be valuable to include in concert with water sampling and analysis of other tissues that have shorter integration rates for a comprehensive view of an estuarine system. / text

In order to test the hypothesis that fractures in outcrops are equivalent to subsurface fracture systems I compare fracture cement morphology, texture, mineralogy and geochemistry from a suite of outcrop samples from Union Springs, NY, with fractures in four cores from a currently producing reservoir in southwest Pennsylvania. Transmitted light-microscope petrography and cold cathodoluminescence of calcite of outcrop and core samples reveals a variety of cement morphologies including crack-seal and blocky fracture cement textures that are interpreted as a record multiple repeated stages of fracture opening and sealing, as well as fibrous calcite fill and other mineral phases. The stable isotopic composition of calcite fracture cements from different fracture types in cores and outcrop range from -21.5 to +4.4‰ δ13C PDB and -8.0 to -12.0 ‰ δ18O PDB and indicate calcite precipitation temperatures between 46 and 89°C. Fluid inclusion microthermometry from secondary fluid inclusions indicates trapping temperatures between 110 and 120°C. Microprobe analysis of fracture calcite cement indicates a range in Fe, Mn, and Mg composition, with subsurface and outcrop cement of similar composition. Assuming burial history predicts thermal history, isotopic compositions together with fluid inclusions suggest calcite precipitated in vertical fractures during prograde burial, during the Acadian to early Alleghanian orogenies. These findings indicate that fractures in outcrops of the Marcellus Formation can be used as a proxy for those in the subsurface. / text

Η παρούσα εργασία έχει σαν σκοπό την μελέτη των σπηλαιοθεμάτων από το σπήλαιο του Αγίου Γεωργίου στην περιοχή του Κιλκίς. Με αυτή την μελέτη διαπιστώθηκαν οι μεταβολές των περιβαλλοντικών συνθηκών με το πέρασμα των ετών, οι οποίες αποτυπώνονται στα στρώματα δημιουργίας των σπηλαιοθεμάτων. Η αποπεράτωση της εργασίας έγινε σε στάδια. Αρχικά υπήρξε υπαίθρια εργασία που χωρίστηκε σε δύο φάσεις. Στην πρώτη φάση έγινε συλλογή υδάτων της ευρύτερης περιοχής για περαιτέρω αξιολόγηση τους, και κατά την δεύτερη πραγματοποιήθηκε δειγματοληψία των ανθρακικών(σταλακτιτών) μέσα από το σπήλαιο. Στο επόμενο στάδιο πραγματοποιήθηκαν εργαστηριακές έρευνες. Έτσι από τα δείγματα που συλλέχθηκαν από την περιοχή του αμέσου ενδιαφέροντος φτιάχτηκαν λεπτές τομές, που μελετήθηκαν μικροσκοπικά. Για να γίνει ακριβής προσδιορισμός των ορυκτών πραγματοποιήθηκε ορυκτολογική ανάλυση με την μέθοδο της περιθλασιμετρίας, και ακολούθησαν μια σειρά από ορυκτοχημικές αναλύσεις. Παράλληλα με αυτές τις εργασίες πραγματοποιήθηκαν αναλύσεις υδάτων τόσο την χημική όσο και για την ισοτοπική σύσταση τους. Επιπλέον με δειγματοληψία στα ανθρακικά(σταλακτιτών) με κατάλληλη μέθοδο, προσδιορίστηκε και η ισοτοπική σύσταση των ανθρακικών(σταλακτιτών) με σκοπό την αποτύπωση των μεταβολών του κλίματος. / -

Die stabilen Isotopenverhältnisse von Sauerstoff und Kohlenstoff (¹⁸O/¹⁶O und ¹³C/¹²C) in atmosphärischem Kohlendioxid sind besonders geeignet, um den CO₂ Kreislauf zu untersuchen. Vor einigen Jahren wurde die Hypothese aufgestellt, dass die 3- Sauerstoffisotopen-Verhältnisse (¹⁷O/¹⁶O und ¹⁸O/¹⁶O) von troposphärischem Kohlendioxid ein neuer Isotopenindikator für die terrestrische Bruttoprimärproduktion ist. In dieser Arbeit wird untersucht, ob und inwieweit dieser neuartige Isotopenindikator konventionelle stabile Isotopenuntersuchungen von troposphärischem Kohlendioxid ergänzen kann. <br/> Die vorliegende Arbeit gliedert sich in vier Teile: (i) Die Entwicklung einer analytischen Methode, mit der die Sauerstoffisotopie (¹⁷O/¹⁶O, ¹⁸O/¹⁶O) von Kohlendioxid mit höchster Präzision gemessen werden kann. (ii) Eine experimentelle Untersuchung zum 3- Sauerstoffisotopen-Austausch zwischen CO₂ und Wasser. Dieser Austauschprozess ist von grundlegender Bedeutung für die Isotopen-Signatur von troposphärischem CO₂. (iii) Eine Studie zur 3-Sauerstoffisotopen-Zusammensetzung von Kohlendioxid aus Verbrennung mit einem besonderen Fokus auf anthropogene CO₂ Emissionen. (iv) Abschließend werden troposphärische CO₂ Daten vorgestellt und mit einem globalen Massenbilanzmodell verglichen. <br/> In Kapitel 2 wird die neuartige Methode zur 3-Sauerstoffisotopen-Analyse von CO₂ beschrieben. Diese Methode ermöglicht es, kleinste Variationen in troposphärischem Kohlendioxid und den unterschiedlichen CO₂ Quellen zur Troposphäre zu untersuchen. Die Methode beruht auf Isotopenäquilibrierung zwischen CO₂ und CeO₂ bei erhöhter Temperatur (T = 685 °C) und anschließender Laser-Fluorinierung des äquilibrierten Cerdioxids. Der freigesetzte Sauerstoff wird anschließend massenspektrometrisch auf seine 3-Sauerstoffisotopen-Zusammensetzung untersucht. Die Sauerstoffisotopie (¹⁷O/¹⁶O, ¹⁸O/¹⁶O) der Kohlendioxid Probe kann aus der Isotopie des CeO2 berechnet werden. Die Messgenauigkeit konnte im Vergleich zu früheren Methoden um etwa eine Größenordnung verbessert werden. <br/> Die Sauerstoffisotopie (¹⁷O/¹⁶O, ¹⁸O/¹⁶O) von troposphärischem Kohlendioxid wird hauptsächlich durch den Isotopenaustausch zwischen CO₂ und Wasser in Pflanzenblättern, Böden und in der obersten Meeresschicht bestimmt. Daher widmet sich Kapitel 3 der experimentellen Bestimmung der Gleichgewichtsfraktionierung (¹⁷O/¹⁶O, ¹⁸O/¹⁶O) zwischen CO₂ und Wasser bei drei unterschiedlichen Temperaturen (2 °C, 23 °C und 37 °C). Die experimentellen Ergebnisse stimmen mit theoretischen Berechnungen überein. Die Kenntnis dieses Gleichgewichtsfraktionierungsprozesses ist eine Grundvoraussetzung, um die 3-Sauerstoffisotopen-Zusammensetzung der natürlichen CO₂ Quellen aus der Biound Hydrosphäre abzuschätzen. <br/> In Kapitel 4 werden die experimentellen Ergebnisse zur 3-Sauerstoffisotopen- Zusammensetzung von Kohlendioxid aus Verbrennung dargestellt (Propan-Butan- Verbrennung, Holzverbrennung, Autoabgase und CO₂ aus Atemluft). Die Ergebnisse zeigen, dass bei Hochtemperatur-Verbrennungsprozessen die Sauerstoffisotopie von Luft- O2 (¹⁷O/¹⁶O, ¹⁸O/¹⁶O) größtenteils auf das Kohlendioxid übertragen wird. Bei niedrigen Verbrennungstemperaturen, wie der Holzverbrennung, wird die Sauerstoffisotopen- Zusammensetzung des freigesetzten Kohlendioxids auch durch CO₂-Wasser Äquilibrierung und andere Sauerstoffquellen, wie z.B. im Holz gebundener Sauerstoff, beeinflusst. Die Sauerstoffisotopen-Zusammensetzung von Kohlendioxid aus Atemluft wird hingegen nur durch den Isotopenaustausch mit Körperwasser bestimmt. Die experimentellen Daten zeigen, dass man anthropogenes Kohlendioxid anhand seiner Sauerstoffisotopie (¹⁷O/¹⁶O, ¹⁸O/¹⁶O) eindeutig von Kohlendioxid aus natürlichen Quellen unterscheiden kann. <br/> In Kapitel 5 werden die ersten hoch-präzisen 3-Sauerstoffisotopen-Analysen von troposphärischem Kohlendioxid vorgestellt. Der Datensatz von CO₂ Proben aus Göttingen zeigt eine deutliche zeitliche Variation in der 3-Sauerstoffisotopen-Zusammensetzung. Diese zeitliche Schwankung stimmt nur teilweise mit der saisonalen Variation des ¹⁸O/¹⁶O Verhältnisses von troposphärischem CO₂ überein. Messungen von CO₂ Proben vom Brocken (1140 m, Harz, Deutschland) stimmen mit den gemessen Daten in Göttingen überein. Die Massenbilanz Vorhersage für die 3-Sauerstoffisotopen-Zusammensetzung von troposphärischem CO₂ stimmt nur teilweise mit den gemessenen Daten überein. Die Modellierung legt nahe, dass die zeitlichen Variationen in der 3-Sauerstoffisotopen- Zusammensetzung nicht durch saisonale Schwankungen der biologischen Aktivität erklärt werden können, stattdessen könnte der Zustrom von stratosphärischem CO₂ die zeitlichen Schwankungen verursachen. <br/> Diese Untersuchung bereitet die Grundlage für 3-Sauerstoffisotopen Analysen von troposphärischem Kohlendioxid und deren aussagekräftige Interpretation. Allerdings können nicht alle Merkmale der gemessenen Isotopendaten erklärt werden, es werden künftig weitere Untersuchungen notwendig sein.

Background: The high prevalence of iron deficiency and anaemia among South African children highlights the need for iron fortification, especially with a highly bioavailable iron compound. Fortification of staple foods is an adequate strategy to provide additional iron to populations at risk. In South Africa it is mandatory to fortify maize meal and wheat flour with iron, as well as other micronutrients. Elemental iron, specifically electrolytic iron, is currently the preferred choice but other compounds that might be more effective in alleviating iron deficiency are under consideration. Objectives: The objective of this study was to provide information about the bioavailability of ferrous fumarate and NaFeEDTA from maize meal porridge in young children, which would assist in selecting a bioavailable alternative to electrolytic iron in the South African National Food Fortification Programme, Methods: A randomized parallel study design was used, with each of the 2 groups further randomised to receive either one of two test regimens in a crossover design in which each child acted as his/her own control. Iron bioavailability was measured with a stable-isotope technique based on erythrocyte incorporation 15 days after intake. Results: The mean absorption of iron from NaFeEDTA and ferrous fumarate from the maize porridge meal was 11.5% and 9.29% respectively. NaFeEDTA and ferrous fumarate are both sufficiently bioavailable from a maize based meal rich in phytates. Conclusion: Both NaFeEDTA and ferrous fumarate would provide a physiologically important amount of iron should they replace electrolytic iron as fortificant in maize flour fortification. The final choice between ferrous fumarate and NaFeEDTA as when it comes to finding the alternative iron fortificant will depend on factors such as technical compatibility, bioavailability, relative cost and organoleptic characteristics. / Thesis (Ph.D. (Nutrition))--North-West University, Potchefstroom Campus, 2007

Aphrodisiac and anti-aphrodisiac pheromone production and composition in the green-veined white butterfly Pieris napi L. were investigated. Aphrodisiac pheromone biosynthesis had different time constraints in butterflies from the diapausing and directly developing generations. Effects of stable isotope incorporation in adult butterfly pheromone, in the nectar and flower volatiles of  host plants from labeled substrates were measured by solid phase microextraction and gas chromatography–mass spectrometry. A method to fertilize plants with stable isotopes was developed and found to be an effective method to investigate the transfer of pheromone building blocks from flowering plants to butterflies. The anti-aphrodisiac methyl salicylate was not biosynthesized from phenylalanine in flowers of Alliaria petiolata. Both aphrodisiac and anti-aphrodisiac pheromones in P.napi are produced not only from resources acquired in the larval stage, but also from nutritional resources consumed intheadult stage. Males of P. napi produce the anti-aphrodisiac pheromone from both the essential amino acid L-phenylalanine and from common flower fragrance constituents. / <p>QC 20140311</p>

Pacific salmon (Oncorhynchus spp.) production strongly influences the ecosystems, cultures and economies of the Northeast Pacific. Historical variability in population sizes is complex, reflecting natural and human drivers. The nature and extent of such ‘exogenous’ controls on salmon and their nursery ecosystems are poorly understood, a significant impediment to sustainable fisheries management. Novel applications of paleolimnology demonstrate that past sockeye salmon abundances and nursery system ecology can be reconstructed from lake sediments. This thesis focuses on employing these techniques to establish the forcing mechanisms underlying salmon population and ecosystem dynamics, and determine the effects and interactions of fisheries management. I provided the first reconstruction for a southern North American stock, which demonstrated the influences of both conspicuous (e.g. commercial fishery, main-stem damming) and uncertain human impacts (e.g. local damming) on endangered salmon declines. By reconstructing ecological variability at multiple trophic levels, I established that rehabilitative management (e.g. fish stocking) may have permanently altered nursery lake rearing capacity, a change potentially reinforced by recent atmospheric changes. This work highlights significant impediments to ongoing recovery efforts. I extended my analysis of salmon management by exploring the interactive impacts of exotic salmon stocking on a remote northern lake. I demonstrated the utility of long-term data in pre-emptively understanding the complex impacts of stocking by documenting the long-term trajectories in limnological conditions. Integrating modeling, limnological and paleolimnological analyses, I determined that climate change and salmon introductions compound to alter chemical, physical and biological lake variables, ultimately altering ecosystem structure and functioning. Finally I reconstructed salmon abundances over the past six millennia, the longest record and the first Canadian example to date, demonstrating salmon production is cyclical and far more variable than observed in the monitoring record. My analyses established that North Pacific salmon production is forced by ocean-atmospheric teleconnections ultimately linked to climatic variability in the tropical Pacific. Further analyses provided the first evidence for a possible solar forcing of Holocene salmon production on both orbital and higher frequency time scales. Cumulatively this research improves our understanding of the processes underlying variability in Pacific salmon and their natal ecosystems, important to ecologically-informed future management. / Thesis (Ph.D, Biology) -- Queen's University, 2008-09-27 02:41:54.576

Migration acts as a selective force on the ecology and evolutionary trajectory of species, as well as presenting fundamental challenges for conservation. My thesis examines the impact of migration by exploring patterns of differentiation among and within migratory and non-migratory populations of the Loggerhead Shrike (Lanius ludovicianus). First, I use morphological, genotypic, stable isotope and leg band recovery data to quantify migratory connectivity in the species. Comparison across markers reveals a generally concordant pattern of moderate connectivity to the Gulf Coast, but overall mixing among populations on the wintering grounds. Combining data from multiple markers in a Bayesian framework improves the resolution of assignment of wintering birds to a breeding ground origin. Information on the species’ migratory patterns provides an explicit framework for interpreting patterns of genetic and ecological variation. I test two hypotheses regarding the interaction of gene flow and migratory habit: (1) migration facilitates gene flow; and (2) gene flow will occur most often along the axis of migration. Genetic population structure in migratory populations is weaker than in non-migratory populations, with gene flow facilitated by dispersal movements of females and first year breeders. As predicted, gene flow occurs most often along the north-south axis of migration, likely due either to opportunistic settling of dispersers or potentially, pairing on the wintering grounds. I investigate variation in the extent and scheduling of moult in relation to underlying genetic differences among populations, age, sex, body size, food availability and migratory habit. I find a pattern of interrupted moult across migratory populations, which may represent a trade-off between time allocated to breeding versus molt and migration. Loggerhead Shrikes in eastern and more southerly migratory populations undergo a greater extent of their moult on the breeding grounds and non-migratory individuals undergo a more extensive pre-formative moult than migratory individuals. I interpret this as suggesting a trade-off between resources allocated to molt versus those required for reproduction. / Thesis (Ph.D, Biology) -- Queen's University, 2011-01-25 15:54:36.593