Dissertations / Theses on the topic 'Proxies development'

The analysis of the sea-ice diatom biomarker IP25 (a mono-unsaturated Highly Branched Isoprenoid (HBI) alkene) in Arctic marine sediments has previously been shown to provide a useful qualitative proxy measure for the past spring sea-ice occurrence. In the Southern Ocean the occurrence and variable abundance of a structurally similar di-unsaturated HBI (HBI diene II) has previously been proposed as a proxy measure of paleo sea-ice extent. However, the use of such biomarker proxies remains under development. In the current study, a number of additional palaeoceanographic developments of HBIs as sea-ice biomarkers in both polar regions has been undertaken. For the Arctic, an investigation into the combined analysis of IP25 and certain phytoplankton biomarkers has been conducted with the aim of providing more detailed and semi-quantitative descriptions of sea-ice conditions in the Barents Sea. In contrast, analysis of HBIs and other lipids within water column, surface sediment and sea-ice samples has been undertaken to provide further insights into the use of HBIs as proxies for Antarctic sea-ice. Analysis of surface sediments from across the Barents Sea has shown that the relative abundances of IP25 and a tri-unsaturated HBI lipid (HBI triene IIIa) are characteristic of the overlying surface oceanographic conditions, most notably, the location of the seasonal sea-ice edge. A semi-quantitative approach, in the form of the PIP25 index, showed a good positive linear relationship between PIP25 indices and spring sea-ice concentration, with a particularly strong relationship found when using HBI triene IIIa (PIIIaIP25) as the open-water counterpart to IP25. The quality of the linear fits were not especially dependent on the balance factor c, used in the PIP25 calculation, which may have important positive consequences for down-core sea-ice reconstruction, and when making comparisons between outcomes from different Arctic regions or climatic epochs. Further, a lower limit threshold for PIIIaIP25 (0.8) might represent a useful qualitative proxy for the past occurrence of summer sea-ice. The re-evaluation of biomarker data from three dated marine sequences in the Barents Sea suggests that the combined analysis of IP25 and HBI triene IIIa can provide information on temporal variations in the position of the maximum (winter) Arctic sea-ice extent, together with more quantitative sea-ice reconstructions. In the Southern Ocean, the distributions of di- and tri-unsaturated HBIs (HBI diene II and HBI trienes IIIa and IIIb) in surface waters were shown to be extremely sensitive to the local sea-ice conditions, consistent with significant environmental control over their biosynthesis by sea-ice diatoms and open water phytoplankton, respectively. Within the water column, the apparent alteration to HBI and other lipid abundances was evident between the photic and benthic parts of the water column, which, along with additional local factors (e.g. polynya formation), may have important implications for paleo sea-ice reconstructions. The sedimentary occurrence and distribution of HBI diene II (termed here as IPSO25) were consistent with the recent identification of the diatom Berkeleya adeliensis Medlin as a source of IPSO25. The tendency for B. adeliensis to flourish in platelet ice, the formation of which is strongly associated with super-cooled freshwater inflow, means that sedimentary IPSO25 may provide a potentially sensitive proxy indicator of landfast sea-ice influenced by meltwater discharge from nearby glaciers and ice shelves. Re-examination of some previous IPSO25 down-core records supports this suggestion, although further down-core analysis is required to confirm this hypothesis. The similar sedimentary distribution relationship between phytoplankton-derived HBI trienes and IPSO25, further indicates that the former may reflect production of these biomarkers by certain diatoms that flourish within the region of the retreating ice edge; however, the source identification of the HBI trienes is still needed to place this interpretation on a firmer footing.

This thesis develops and applies new techniques for reconstructing past environments from the speleothem archive. Chapter 3 introduces Ca isotopes as a novel palaeo-aridity proxy. Recent dripwater, farmed calcite and bedrock data show that, in the modern environment, 36% of initial dripwater Ca is removed by prior calcite precipitation at the HS4 dripsite (Heshang Cave, Central China). A speleothem record spanning the 8.2kyr event suggests this value increased to 60% during the event, in response to a decrease in effective rainfall of approximately a third. Modern Ca isotope systematics, and the cycling of other Group II metals, are studied further in Chapter 4. Data from Heshang Cave monitoring samples explore the temporal and spatial controls on these proxy systems. Results highlight the importance of secondary calcite as a potential source of dripwater metals, as well as the significant contribution of particulate calcite to bulk dripwater chemistry. At the HS4 dripsite, over a third of bulk dripwater Ca is present as particulate calcite. This influences bulk dripwater Ca concentrations and isotopes, as well as potentially impacting speleothem growth and chemistry. Chapters 5 introduces CaveCalc, a new numerical model for dripwater and speleothem chemistry and isotopes based on PHREEQC. Key strengths of CaveCalc include its ability to model multiple proxy systems in a single framework, the ability to quantify the extent of open-system dissolution, and the extensible nature of its design. Chapter 6 applies CaveCalc to disentangling the controls on dripwater and speleothem δ¹³C values. Model results are compared with speleothem data. At Heshang Cave, anomalously high δ¹³C is quantitatively explained as the result of CO₂ degassing and prior calcite precipitation, an interpretation made possible by the availability of coupled δ¹³C, a¹⁴C and Ca isotope data. This approach provides a powerful tool to help researchers better interpret dripwater and speleothem δ¹³C data.

Although Holocene climate changes are significantly smaller in amplitude than the Pleistocene Glacial-Interglacial cycles (Dansgaard et al., 1993), they have affected human civilisations over at least the last 4000 years (Buntgen et al., 2011; Lamb, 1995; Mayewski & White, 2002). The study of Holocene climate variations is increasingly important to disentangle climate change caused by anthropogenic influences from natural climate change. Furthermore, Holocene climate change provides the geological context in which to place contemporary climatic observations. Studying sedimentary records stemming from marine biotopes located close to land, such as fjords, affords the opportunity to study marine and terrestrial paleo-climatic variability, and therein linking the two together. Additionally, fjordic environments typically have a higher sediment accumulation rate than deeper ocean sites, facilitating resolution of rapid climate change events. The fjords of Northwest Iceland are ideal for studying Holocene climate change as they receive warm water from the Irminger current, an end member of the Atlantic current, but are also influenced by the east Greenland current, which brings cold polar waters to the region (Jennings et al., 2011). Furthermore, the coring site is located beneath one of the dipoles of the North Atlantic Oscillation (Hurrell, 1995). Therefore, oceanic and atmospheric Holocene variability should be recorded in the sediments studied. Alkenones, terrestrial leaf wax n-alkanes, branched and archaeal glycerol tetraethers and C/N ratios from a sediment core from the mouth of the Ísafjarðardjúp fjord (MD99-2266; location: 66° 13' 77'' N, 23° 15' 93'' W; 106 m water depth) were analysed. These terrestrial and marine biomarkers were used to produce biomarker based palaeoclimatic records with the highest resolution to date (one sample every ~ 32 years), covering the Holocene from ~ 10,700 calibrated years before present (cal. a BP) to ~ 300 cal. a BP. The terrestrial and marine organic carbon contributions to the sediment and the palaeoproductivity of the fjord vary throughout the Holocene forced by changing climate. While the amount of terrestrial organic carbon is primarily controlled by the development of vegetation as glaciers retreat, the primary productivity is controlled by varying influxes of nutrient rich water masses. By combining the reconstructed sea surface temperature, air temperature and precipitation records, climatic changes that affect the terrestrial and marine realm are uncovered. Two periods in the Holocene where major climatic shifts in the North Atlantic region occur, one at ~ 7700 cal. a BP, and one at ~ 2900 cal. a BP, are observed. Meltwater events and decreasing summer insolation drive climatic change throughout the early Holocene. The middle Holocene climate, from 7700 to 2900 cal. a BP is driven by decreasing summer insolation, and meridional overturning circulation. The climate variability is decoupled from insolation change in the late Holocene, and the sea surface temperature and air temperature, and precipitation changes are driven by NAO-type fluctuations and variations in the heat transport via the meridional overturning circulation. The TEX86 palaeo-SST thermometer does not work in Ísafjarðardjúp fjord. The TEX86-SSTs are adversely affected by GDGTs associated with archaea mediating anaerobic oxidation of methane, as indicated by the methane index. Methane indices as low as 0.1 indicate anaerobic oxidation of methane at the site studied. The palaeo-sea-ice proxy IP25 was not detected in the sediments of MD99-2266 even though the northwest Icelandic coast has been affected by drift ice, particularly in the late Holocene. Therefore, the use of carbon isotopic signatures from sedimentary fatty acids, derived from ice and pelagic algae was investigated as a sea-ice proxy. Ice algae, ice core, water column particulate organic matter and sediment samples were collected on the ICE CHASER 2010 research cruise. The carbon isotopic signature of the ice algal C16 fatty acid is significantly heavier than that of the pelagic derived organic matter. Furthermore, the carbon isotopic signature of the fatty acid in the samples from the sediment core located at the ice edge is isotopically heavier, compared to the fatty acid isotopic signature from the sediment core from a pelagic site. It appears that the isotopic signature of algal fatty acids can be used to elucidate sea-ice cover, however, more research is needed.

Delta regions are typically characterized by their high population density, low elevation, and risk of flooding. Long term planning and preparation is needed to mitigate the adverse effects of floods. Disaster management planning and flood protection measures require information about urbanization patterns, but this information is lacking in many parts of the world. Global satellite data could potentially aid or replace local urbanization data in such data scarce areas. This master thesis assesses the suitability of two global satellite datasets to serve as proxies for urbanization in flood prone areas: the Global Human Settlement (data for 1975, 1990, 2000 and 2014) and stable Nighttime Lights data series (annual data, 1992-2013). The assessment is performed through comparison of spatial-temporal urbanization trends of the global datasets with a previous study performed in the Netherlands using detailed local data. These spatial-temporal trends involve the share or urban area that is situated in flood prone zones and the average inundation depth. Through analysis based on Geographic Information Systems it was found that the Global Human Settlement data series indicates a stable increase in the percentage of urban area in flood prone zones from 31.60% in 1975 to 36.54% in 2014. Potentially, this increase results from the flood protection measures installed between 1954 and 1997. The Nighttime Lights data series shows values of around 36% throughout its time period, with no clear increase or decrease. These values are on average 15-17% higher over the whole time series than the values found with the use of the local data. The Global Human Settlements dataset shows values for the average inundation depth from 1.47m in 1975 to 1.72m in 2014, similar to the local data. The increase could be explained by the fact that only areas with higher inundation depths are available for urbanization. The Nighttime Lights does not show a clear trend with values ranging from 1.52m to 1.70m and large annual variation. Overall, the suitability of the Global Human Settlement dataset is higher than the stable Nighttime Lights dataset for this study area as it shows values more similar to the local data and does not require prerequisite threshold analysis, which is the case for the Nighttime Lights data.

This paper hopes to serve as a primer, firstly for this Author, regarding the concept of Institutional Economics; a foundation and an enabling environment, which allows economics to function and to be free. Firstly, we focus on the topic of institutions within the scope of economic development, and ask the simple question, “Why some countries are poor, and why some countries are rich?” In terms of set up, this paper is guided by Dani Rodrik & Arvind Subramanian’s 2003 article, “The Primacy of Institutions (and what this does and does not mean).” I looked at how institutions, market openness and geography effect economic development. Both an OLS and pooled OLS model are employed, with the results showing that, institutions account for the largest variation in income. The data is sourced from the Heritage Foundation, 2019 Index of Economic Freedom. Secondly, a discussion of Brunei Darussalam, my home country is presented, trying to link ideas of institutional economics, economic freedom, entrepreneurship and economic development.

L’objectif principal de cette thèse était de comprendre comment la variabilité temporelle et spatiale de l’oxygénation de l’eau de fond est enregistrée dans le test des foraminifères benthiques, à travers le rapport Mn/Ca et les paramètres des pores. Pour atteindre cet objectif, Ammonia tepida, un groupe d’espèces pseudocryptiques, du Grevelingenmeer (Pays-Bas) a été principalement étudié. A ce site, le gradient bathymétrique est accompagné par une augmentation de la durée et de l’intensité de l’hypoxie/anoxie saisonnière qui influence indirectement le rapport Mn/Ca et directement la porosité d’A. tepida. Notre étude de la Zone à Oxygène Minimum de la Mer d’Arabie suggère la présence d’un important biais diagénétique dans le signal Mn/Ca lors de la transition d’un foraminifère vivant vers un test fossile. En conclusion de cette thèse, la composition Mn/Ca d’un test des foraminifères benthiques dans notre zone d’étude semble être influencée par trois facteurs temporelles 1) l’oxygénation du milieu benthique et la position de la zone redox enrichie en Mn2+ dans l’eau interstitielle, 2) l’activité des bactéries câblées et 3) la période de calcification, ainsi que par trois facteurs spatiaux qui déterminent la position du foraminifère par rapport à la zone de Mn2+ lors de la calcification 4) le microhabitat, 5) la migration verticale des foraminifères et 6) la bioturbation de la macrofaune. Dans le Grevelingenmeer, la porosité d’A. tepida montre une relation avec l’oxygénation. Le couplage entre porosité et oxygénation semble être direct, une plus grande porosité permettant des échanges de gaz plus intensifs. Au contraire, la relation entre le rapport Mn/Ca et l’oxygénation serait plus indirecte, puisque celle-ci est également influencée par l’activité microbienne. L’utilisation simultanée de ces deux proxies totalement indépendants nous semble prometteuse, spécialement parce que ces proxies réagissent à différentes échelles de temps
The main objective of this thesis was to investigate how the temporal and spatial variability of bottom water oxygenation is recorded in the benthic foraminiferal test, by the Mn/Ca ratio, and by the pore parameters. To achieve this objective, Ammonia tepida, a group of pseudocryptic species, of the Lake Grevelingen (Netherlands) was mainly studied. At this site, the depth gradient is accompanied by an increase in duration and intensity of seasonal hypoxia/anoxia which indirectly influences the Mn/Ca ratio and directly the porosity of A. tepida. Our study of the Oxygen Minimum Zone in the Arabian Sea suggests the presence of a significant diagenetic effect during the transition of a Mn/Ca signal from a living foraminifer to a fossil signal. In conclusion of this PhD research, the Mn/Ca signal of a benthic foraminiferal test seems to be influenced by three temporal factors: 1) the oxygenation of the benthic ecosystem and the position of the Mn2+ zone in the interstitial water, 2) the cable bacteria activity, and 3) the period of calcification, as well as by three spatial factors which determine the position of the foraminifer with respect to the Mn2+ zone during calcification 4) the microhabitat, 5) the vertical migration of the foraminifer and 6) the bioturbation of macrofauna. In the Lake Grevelingen, the porosity of A. tepida shows a relationship with oxygenation of the benthic ecosystem. The coupling between porosity and oxygenation could be rather direct, a greater porosity allowing more intensive gas exchanges. In contrast, the relationship between the Mn/Ca ratio and the oxygenation would be more indirect, being influenced in particular by the microbial activity. The simultaneous use of these two totally independent proxies seems promising, especially because these proxies react at different time scales

The aim of this thesis is to develop and apply novel climate proxies to understand the palaeoceanographic evolution of the N.E. Atlantic during the late-Glacial and Holocene. The proxies investigated are based on organic molecular compounds called lipid biomarkers and bulk organic matter properties. The primary focus is on long-chain alkenones, molecules which have been extensively used in mid and low latitude open oceans to reconstruct sea surface temperatures (SSTs) during the Quaternary. Thus, the relative abundance of some alkenones is related to the growth temperature of the algae at the time of the biosynthesis of these molecules (expressed in the U(^K)(_37) and U(^K)(_37)’ indices). In high latitudes and coastal environments, the temperature dependence of alkenones is controversial, and the potential environmental information from alkenones is not yet well understood. In such locations there is increasing abundance of the C(_37:4) alkenone (quantified as %C(_37:4)). The presence of this component has been related to changes in the relative budget of freshwater in the surface ocean. A central aim of this thesis is to carry out an empirical investigation to find out the key environmental factors that control %C(_37:4) to assess its potential as a palaeoceanographic proxy. Research was conducted in the Nordic Seas and N.W. Scotland using samples from the water column, surficial sediment and sediment cores. The research undertaken can be broken down in three main sections: Alkenone distributions in the Nordic Seas. The aim was to clarify and extend the application of alkenones as palaeoceanographic proxies in subpolar to polar environments. Samples of filtered sea surface POM were analysed and extremely high %C(_37:4) values (up to 77%) were measured in polar waters (up to 80% sea-ice cover). Values of %C(_37:4) across the Nordic Seas showed a strong association with water mass type. A combined data-set revealed a stronger correlation of %C(_37:4) to sea surface salinity' (SSS, R(^2) = 0.72) than to SST (R(^2) = 0.5). However, scatter was observed in the relationship of %C(_37:4) to SSS, preventing confirmation of %C(_37:4) as a palaeo-SSS proxy. Values of %C(_37:4) in sea surface POM were high compared to surficial sediments. We discount preferential degradation of the %C(_37:4) alkenone and invoke dilution of the %C(_37:4) signal in sea surface sediments by advected allochthonous matter to explain this. The POM filter data suggest that, overall, U(^K)(_37) is a more appropriate SST index for the Nordic Seas than U(^K)(_37) '. Examination of the scatter in the U(^K)(_37) ' versus SST relationship, shows that regions in the south of the Nordic Seas (including the Icelandic shelf) may yield reliable, alkenone based, palaeoceanographic reconstructions. Comparison of %C(_37:4) distributions with dinocyst proxies in a late Holocene core from the Barents Sea suggests %C(_37:4) may be a general marker for the influence of arctic/polar water in palaeoceanographic reconstructions. The palaeoceanography of the Icelandic shelf iox. the post-Glacial period (0-15 kyr BP) was reconstructed from alkenone indices measured in three cores collected N and W of Iceland. One of the cores, JR51-GC35, contained a continuous record of Holocene sedimentation spanning 0 - 10.1 kyr BP. Superimposed on a general Holocene cooling trend in core JR5I-GC35 were millennial scale oscillations of ~2 C. The timing of the oscillations was in close agreement with the variability in IRD records from the East Greenland shelf and the timing of glacier advances in northern Iceland. A comparison of the U(^K)(_37) -SST records from JR51-GC35 and a published core from the eastern Nordic Seas (MD952011) showed significant differences (superimposed on the general trend) in the timing of millennial scale climate events. This illustrates that Holocene climate evolution in the Nordic Seas was more complex than previously suggested, with significant climatic differences between the eastern and western Nordic Seas caused by the differential variability of the Irminger and Norwegian Currents with time. The potential application for reconstructing past sea-level changes in NW. Scotland of lipid biomarkers (alkenones, n-alkanes and chlorophyll derivatives), and bulk organic parameters (%TOC, C(_nrg)/N) was assessed by a survey of modern basins (at different stages of isolation from the sea) and fossil basins (with known sea-level histories). A logit regression analysis of all the sediment samples was employed to find which of the biomarkers or bulk organic measurements could reliably characterize the sediment samples in terms of a marine/brackish or isolated/lacustrine origin. The results suggested an excellent efficiency for the alkenone index %C(_37:4) at predicting the depositional origin of the sediments. This study suggests alkenones could be used as an indicator of sea-level change in fossil isolation basins.

Sediment records of two Italian subalpine lakes (Lake Garda and Lake Ledro) were analyzed in order to reconstruct their ecological evolution over the past several hundred years. A multi-proxy and multi-site approach was applied in order to disentangle the effects of local anthropogenic forcings, such as nutrients, and climate impacts on the two lakes and their catchments. Biological indicators (sub-fossil pigments, diatoms and Cladocera) were used to reconstruct changes in the aquatic food web and to define the lake reference conditions, while geochemical methods, i.e. wavelength-dispersive Xray fluorescence spectroscopy (WD-XRF), were used to provide quantitative information on the different physical or chemical processes affecting both lake and catchment systems. Sub-fossil pigments and diatoms, together with their respective inferred TP values, suggested very stable oligotrophic conditions in both lakes until the 1960s. The period following was affected by nutrient enrichment, which led to a drastic shift in the phytoplanktonic community. The response of sub-fossil pigments and diatoms to major climatic anomalies such as the Medieval Climatic Anomaly (MCA) and the Little Ice Age (LIA) were not pronounced, and the taxonomic composition remained relatively stable. On the contrary, these proxies showed an indirect response to climate variability since the beginning of the nutrient enrichment phase in the 1960s. In Lake Garda, the winter temperature regulates the water column mixing, which in its turn controls the degree of nutrient fertilization of the entire water column, and the related phytoplankton growth. In Lake Ledro a rapid reorganization of planktonic diatoms was observed only during the temperature recovery after the LIA, while recent temperature effects are masked by the prevailing nutrient effects. In Lake Garda, Cladocera remains responded in quantitative and qualitative terms to climatic changes, whereas in Lake Ledro they appeared to be mainly affected by variations in hydrological regimes, i.e. flood events. Cladocera remains corroborated the nutrient enrichment after the 1960s in both lakes as inferred by diatoms and pigments. In Lake Garda, the geochemical data showed a pronounced shift in elemental composition since the mid-1900s, when major elements and lithogenic tracers started to decrease, while some elements related to redox conditions and other (contaminant) trace elements increased. The general trends since the mid-1900s agree with the biological records. However, some differences recorded in the two different basins of Lake Garda reflected the effects of local conditions, both related to hydrology and sedimentation patterns. Lake Ledro showed higher short-term variability for most elements, even though some features were comparable to Lake Garda. The geochemical record of Lake Ledro revealed a major influence of human-induced lake-level fluctuations and catchment properties. This paleolimnological study allows us to place temporally restricted limnological surveys into a longer-term secular perspective, which is highly valuable for the definition of lake reference conditions. Because the restoration targets are usually based on the lake reference conditions, this study highlighted also the necessity to pay particular attention to the lake-specific sensitivity patterns. The multi-proxy and multi-site approach showed that the lake conditions of large and deep lakes in northern Italy, such as Lake Garda, are mainly driven by nutrient enrichment and/or climate change. In contrast, smaller lakes with larger catchment areas, such as Lake Ledro, are seemingly more impacted by conditions and processes occurring in the drainage basin.

Les biocarbonates produits par les organismes marins tels que les foraminifères ou les coraux sont des archives importantes pour étudier les environnements et climats du passé. Depuis les travaux de H. Urey en 1947, il est établi que la composition isotopique en oxygène-18 (δ18O) des carbonates reflète à la fois la température de formation et le rapport isotopique (18O/16O) de l'eau de mer. Cette relation, supposément fondée sur l'équilibre thermodynamique entre l'eau et le carbonate, peut cependant être perturbée soit par des paramètres environnementaux, soit par des mécanismes biologiques . Chez certains organismes, comme les coraux, ces « effets vitaux » se manifestent par des déséquilibres isotopiques flagrants, qui compliquent l'interprétation d'une partie non négligeable du registre sédimentaire fossile. En réponse à ces problèmes, cette thèse adopte une approche novatrice en tirant partie de nouveaux traceurs isotopiques, les anomalies d'oxygèen-17 (Δ17O) et les « clumped isotopes » (Δ47, Δ48), en complément des mesures traditionnelles de δ13C et δ18O. En travaillant à partir d'échantillons modernes dont les conditions de croissance sont bien documentées, les contraintes supplémentaires fournies par ces traceurs permettent de mieux caractériser les facteurs qui influençent la composition isotopique des biocarbonates.Ce travail a commencé par une première étape exploratoire, visant d'une part (1) à identifier les organismes / cas d'étude à cibler en priorité, en associant des mesures isotopiques à faible résolution spatiale avec des observations in situ fournissant des informations minéralogiques, élémentaires et isotopiques à bien plus haute résolution, et d'autre part (2) à établir des protocoles expérimentaux optimisés pour les techniques instrumentales de pointe utilisées pour les mesures de Δ47/Δ48 (par spectrométrie de masse à très haute sensibilité) et de Δ17O (par VCOF-CRDS, une technologie spectroscopique innovante). Le premier volet de ce travail a donné lieu à la première l'étude publiée sur les clumped isotopes dans les squelettes de bryozoaires. Les résultats mettent en évidence une forte influence de la minéralogie sur le signal Δ47, qui semble résulter d'un simple effet thermodynamique. Par contre, il apparaît que les organismes de certains sites présentent des déséquilibres isotopiques spécifiques, potentiellement associés à la salinité locale. Ces résultats suscitent de nouvelles interrogations sur l'influence de certains paramètres environnementaux sur l'activité de certaines enzymes, en particulier l'anhydrase carbonique qui joue un rôle majeur dans le maintien de l'équilibre isotopique entre l'eau et le carbone inorganique dissous (CID). Le second volet porte sur la caractérisation, chez les coraux d'eau froide, des écarts à l'équilibre dans cinq dimensions isotopique (δ13C, δ18O, Δ17O, Δ47, Δ48), observées ici conjointement pour la première fois. Les observations sur Δ47 et Δ48 sont en accord avec une publication indépendante récente, et cohérentes avec un modèle théorique du CID, suggérant que la signature isotopique des coraux profonds est principalement contrôlée par des effets cinétiques liés à l'absorption du CO₂ métabolique. Cependant, les prédictions de ce même modèle sont en désaccord avec nos mesures de Δ17O (qui ont été depuis confirmées par des observations indépendantes), soulignant la nécessité de réviser certains paramètres du modèle. La richesse des questions nouvelles suscitées par ce travail de thèse illustre l'intérêt de combiner les observations dans un espace multi-isotopique à 5 dimensions avec des modèles théoriques quantitatifs, tout en confrontant ces modèles aux spécificités biologiques de chaque organisme marin, permettant tout à la fois de mieux comprendre les mécanismes de biominéralisation et de quantifier l'influence des effets vitaux dans les biocarbonates sur les paléo-reconstructions
Biocarbonates produced by marine organisms such as foraminifera or corals serve as important archives for studying past environments and climates. Since the work of H. Urey in 1947, it has been established that the oxygen-18 isotopic composition (δ18O) of carbonates reflects both the formation temperature and the isotopic ratio (18O/16O) of seawater. However, this relationship, supposedly based on the thermodynamic equilibrium between carbonate and water, can be disturbed by either environmental parameters or biological mechanisms. In certain organisms, such as corals, these "vital effects" manifest as significant isotopic disequilibrium, complicating the interpretation of a substantial portion of the fossil sedimentary record.In response to these challenges, this thesis adopts an innovative approach by leveraging new isotopic tracers, namely oxygen-17 anomalies (Δ17O) and "clumped isotopes" (Δ47, Δ48), in addition to traditional δ13C and δ18O measurements. By working with modern samples for which growth conditions are well documented, the additional constraints provided by these tracers allow for a better characterization of the factors influencing the isotopic composition of biocarbonates.This work began with an exploratory phase, aimed at (1) identifying the organisms/case studies by combining low spatial resolution isotopic measurements with in situ observations that provide mineralogical, elemental, and isotopic information at much higher resolution, and (2) establishing optimized experimental protocols for cutting-edge instrumental techniques used for Δ47/Δ48 measurements (via ultra-high sensitivity mass spectrometry) and Δ17O (via VCOF-CRDS, an innovative spectroscopic technology).The first part of this work resulted in the first published study on clumped isotopes in bryozoan skeletons. The results highlight a strong influence of mineralogy on the Δ47 signal, which seems to result from a simple thermodynamic effect. However, it appears that organisms from certain sites exhibit specific isotopic disequilibrium, potentially linked to local salinity. These findings raise new questions about the influence of certain environmental parameters on the activity of specific enzymes, particularly carbonic anhydrase, which plays a key role in maintaining isotopic equilibrium between water and dissolved inorganic carbon (DIC).The second part focuses on characterizing isotopic disequilibria in five isotopic dimensions (δ13C, δ18O, Δ17O, Δ47, Δ48) in cold-water corals, observed together here for the first time. The observations on Δ47 and Δ48 are consistent with a recent independent publication and align with a theoretical DIC model, suggesting that the isotopic signature of deep-sea corals is primarily controlled by kinetic effects related to the absorption of metabolic CO₂. However, the predictions of this same model are at odds with our Δ17O measurements (which have since been confirmed by independent observations), underscoring the need to revise certain model parameters.The richness of new questions raised by this thesis highlights the value of combining observations in a five-dimensional multi-isotopic space with quantitative theoretical models, while confronting these models with the biological specifics of each marine organism. This approach enables a deeper understanding of biomineralization mechanisms and allows for a more precise quantification of the influence of vital effects in biocarbonates on paleo-reconstructions

It is increasingly acknowledged that the proper objective of government efforts towards economic development should be aimed at improvements beyond simple measures of growth, poverty and inequality towards richer measures of human well-being. Herein, the economic and non-economic quality of life, as well as the quantity of life, becomes important indicators. Economists and other social planners therefore need to develop more meaningful indicators of the quality of life. Objective and subjective indicators of the quality of life can be distinguished. For various reasons, this thesis will focus on the search for more meaningful objective indicators of the quality of life. One of the most wellknown objective indicators of quality of life is the Human Development Index (HDI). There is, however, a growing dissatisfaction with the HDI. In this thesis, two recent methodological advances in the measurement of quality of life are applied and combined and, in particular, in the measurement of the non-economic quality of life, to the sub-national quality of life in South Africa. As such, this thesis’ contribution is twofold. First, it investigates the extent to which the quality of life differs within a developing country, as opposed to most studies that focus on either inter-country differences in quality of life, or studies that focus only on spatial inequalities within countries using a restricted set of measures such as per capita income or poverty rates and headcounts. Secondly, this thesis applies a recent methodology proposed by McGillivray (2005) to isolate the non-economic (non-monetary) quality of life in various composite indices and to focus on the non-economic quality of life across 351 South African magisterial districts Indices for the non-economic quality of life are compiled for geographical quality, for demographic quality, and based on the human development index. Furthermore, given that composite indices used in the construction of measures of quality of life consist of weightings of multiple proxies, this thesis implements the method of Lubotsky and Wittenberg (2006) which proposed a new estimator for the case where multiple proxies are to be used for a single, unobserved variable such as quality of life. This thesis establishes that when the non-economic quality of life of the demographic index is considered, the top ten regions in 1001 were as follows: Pretoria, Johannesburg, Soweto, Port Elizabeth, Durban, Inanda, Pietermaritzburg, Wynberg, Mitchellsplain and Vanderbijlpark. It is important to note that, when interpreting these results, one should take caution since variables such as the number of people, number of households etc. is included in this index and as a region grows in population size the more negative consequences such as a higher crime rate can be associated with the particular region. The top ten regions in which to reside in 1004 as determined by the geography quality of life index were: Calvinia, Gordonia, Namaqualand, Kenhardt, Carnarvon, Ubombo, Williston, Hlabisa, Ceres and Ingwavuma. This geography index measures a region's natural beauty which, according to Wey (2000), contributes positively to one's perceived quality of life. Considering changes in non-economic quality of life indices between 1996 and 2004, the conclusion can he drawn that the South African government has been successful to a certain degree in addressing non-economic quality of life. Social policies such as health care, education, housing, water and sanitation appear to have had a positive effect on people's perceived non-economic quality of life in areas that were relatively deprived in 1996.
Thesis (Ph.D. (Economics))--North-West University, Potchefstroom Campus, 2007

Understanding complex Earth systems is challenging for scientists and students alike, because of the characteristics (e.g. bifurcations, self-organization, chaotic response) that are associated with these systems. This research integrates two research strands which contribute to the scientific and pedagogical understanding of complex Earth systems. In the first strand, a method that characterizes volatile organic compounds (VOCs) as ecological proxies of soil microbial ecosystems was validated. Unlike other measures of microbial community structure (e.g. Biolog and FAME), VOCs are advantageous because they are non-destructive and can provide temporal and spatial data. Additionally they are rich sources of information that describe the microbial metabolism, community structure, and organic carbon substrates utilized by soil microorganisms. Statistical results indicate that the detected and identified VOCs were significant (p < 0.05) indicators of microbial community composition shift in soil microcosm studies. Geographical information systems (GIS) illustrates that VOCs varied with space and time in south Texas soils. The second strand focuses on a geoscience education study exploring student conceptual model development of complex Earth systems. The efficacy of multiple representations and inquiry was tested as the pedagogical strategy in upper and lower level undergraduate courses to support students’ conceptual model development of complex Earth systems. Comparisons in student performance were based on prior knowledge (low and high) and on exposure to the implemented pedagogy (control and experimental groups). Results indicate that an inquiry-based learning model coupled with the use of multiple representations had significant positive performance impacts on students’ conceptual model development and content knowledge. This dissertation model integrates science and education research and is particularly useful for graduate students who intend to pursue a career in academia and envision teaching as part of their professional duties. It allows for synergy between teaching and research to be achieved where the classroom becomes a laboratory for research. Ultimately, the research conducted in the classroom informs pedagogy and enhances scholarship. Graduates learn to bridge the gap between education and science departments where they become leaders in science who conduct cutting-edge scientific research and also value making a broader impact on society through enhancing public education.

Sediment records of two Italian subalpine lakes (Lake Garda and Lake Ledro) were analyzed in order to reconstruct their ecological evolution over the past several hundred years. A multi-proxy and multi-site approach was applied in order to disentangle the effects of local anthropogenic forcings, such as nutrients, and climate impacts on the two lakes and their catchments. Biological indicators (sub-fossil pigments, diatoms and Cladocera) were used to reconstruct changes in the aquatic food web and to define the lake reference conditions, while geochemical methods, i.e. wavelength-dispersive X-ray fluorescence spectroscopy (WD-XRF), were used to provide quantitative information on the different physical or chemical processes affecting both lake and catchment systems. Sub-fossil pigments and diatoms, together with their respective inferred TP values, suggested very stable oligotrophic conditions in both lakes until the 1960s. The period following was affected by nutrient enrichment, which led to a drastic shift in the phytoplanktonic community. The response of sub-fossil pigments and diatoms to major climatic anomalies such as the Medieval Climatic Anomaly (MCA) and the Little Ice Age (LIA) were not pronounced, and the taxonomic composition remained relatively stable. On the contrary, these proxies showed an indirect response to climate variability since the beginning of the nutrient enrichment phase in the 1960s. In Lake Garda, the winter temperature regulates the water column mixing, which in its turn controls the degree of nutrient fertilization of the entire water column, and the related phytoplankton growth. In Lake Ledro a rapid reorganization of planktonic diatoms was observed only during the temperature recovery after the LIA, while recent temperature effects are masked by the prevailing nutrient effects. In Lake Garda, Cladocera remains responded in quantitative and qualitative terms to climatic changes, whereas in Lake Ledro they appeared to be mainly affected by variations in hydrological regimes, i.e. flood events. Cladocera remains corroborated the nutrient enrichment after the 1960s in both lakes as inferred by diatoms and pigments. In Lake Garda, the geochemical data showed a pronounced shift in elemental composition since the mid-1900s, when major elements and lithogenic tracers started to decrease, while some elements related to redox conditions and other (contaminant) trace elements increased. The general trends since the mid-1900s agree with the biological records. However, some differences recorded in the two different basins of Lake Garda reflected the effects of local conditions, both related to hydrology and sedimentation patterns. Lake Ledro showed higher short-term variability for most elements, even though some features were comparable to Lake Garda. The geochemical record of Lake Ledro revealed a major influence of human-induced lake-level fluctuations and catchment properties. This paleolimnological study allows us to place temporally restricted limnological surveys into a longer-term secular perspective, which is highly valuable for the definition of lake reference conditions. Because the restoration targets are usually based on the lake reference conditions, this study highlighted also the necessity to pay particular attention to the lake-specific sensitivity patterns. The multi-proxy and multi-site approach showed that the lake conditions of large and deep lakes in northern Italy, such as Lake Garda, are mainly driven by nutrient enrichment and/or climate change. In contrast, smaller lakes with larger catchment areas, such as Lake Ledro, are seemingly more impacted by conditions and processes occurring in the drainage basin.

Growth polarity in leaves – a final discussion Insights into the growth processes of leaf lamina have come from studies on several species including Arabidopsis, Antirrhinum, tobacco and maize. A feature common to the growth of leaf in these distantly related species is the existence of a pronounced growth gradient in the proximo-distal axis -growth at the tip (distal part) is arrested at an early stage while the basal region (proximal part) continues to grow for the longest duration. This is because the cell division is arrested first at the tip at an early stage of development and the arrest progressively spreads towards the base. Along with the strong proximo-distal growth gradient, a milder growth gradient also exists in the medio-lateral axis, such that the cell division arrest travels slightly faster on the leaf margins imparting an overall convex shape to the arrest front. The temporal and spatial progression of the arrest front has not only been implicated in shaping up of a leaf but is also of paramount importance in the maintenance of a flat surface during leaf growth. Although the patterning mechanisms described above seem to operate during leaf growth in many6 species, the molecular mechanisms governing these processes is still in its infancy. Moreover, patterning of leaf growth has been studied only in a handful of model species and, therefore, the information from the vast body of natural variation remains neglected. Proximo-distal growth patterning by CINCINNATA Mutant leaves with altered rates or shapes of the arrest front progression deviate significantly from the normal shape and overall flat structure. Mutation in the CIN gene in Antirrhinum and its orthologues in Arabidopsis cause buckling of the leaf due to excess cell proliferation, which in turn is caused by a delayed progression of the arrest front. CIN-like genes code for TCP transcription factors and are expressed in a broad zone of a growing leaf somewhat distal to the proliferation zone. Even though several direct and indirect targets of CIN-like genes have been identified in various plant species, their role in regulating leaf maturity and surface curvature has remained unclear. The comparison of global transcription profile of wild type and cincinnata mutant of Antirrhinum showed that the expression of genes involved in either signaling or biosynthesis of the major growth hormones were altered in the mutant. By combining DNA-protein interaction, expression analysis, chromatin immuno-precipitation and RNA in situ hybridization, we show that CIN maintains surface flatness by regulating the signaling or level of major plant hormones in developing leaves. CIN promotes cytokinin signaling by directly binding to and thereby promoting the expression of a cytokinin receptor, AmHK4, in a spatio¬temporal manner. Furthermore, it also seems to affect GA level indirectly in young leaves by regulating the spatio-temporal as well as levels of GA-biosynthetic and GA-degrading enzymes. Thus, CIN seems to accelerate maturity in leaf cells along the tip-to-base direction through its effect on the cytokinin and GA signaling pathways. In addition, CIN suppresses auxin signaling more at the margin than in the centre by establishing a margin-to-medial expression gradient of a homologue of the auxin suppressor IAA3, thereby suppressing excess cell proliferation on the margin. Our results uncover an underlying mechanism in a developing leaf that controls curvature of the leaf surface by promotion of timely exit from cell proliferation in the proximo-distal as well as the medio-lateral axes via multiple hormone pathways. Divergent growth polarities in the proximo-distal axis of leaves The morphogenetic gradient in the proximo-distal axis of a leaf is brought about by the dynamic expression of several heterochronic regulators which can include TCP and GRF classes of transcription factors. Interestingly, many of these transcription factors are also regulated post-transcriptionally by micro RNAs. In case of the studied model species, these factors seem to be associated with basipetal growth. The early arrest in cell proliferation at the tip and continued cell division at the base has served as a paradigm in studying leaf growth and has been used to conceptualize the growth of leaves with different shapes. However, the possibility of the existence of different patterning mechanisms during leaf growth in the highly diverse plant kingdom remains unexplored. Our survey of leaf growth patterns in 75 dicot species reveals the existence of four distinct proximo-distal polarities in growth patterns. Using the law of simple allometry, we also show that the differentially growing regions of leaves bear a constant relationship between them during growth. A combination of cell-size studies, histochemical staining and expression analysis reveals a strong correlation among growth pattern, cell size and the cell proliferation status. The cell size studies also indicate that there is a wide variation in the final cell sizes of leaves and the relative contribution of cell division and cell expansion to the final leaf size can be highly variable. Furthermore, we find that the varying growth patterns are linked to changes in the expression pattern of miR396, which controls the expression pattern of cell division regulatory transcription factors, the GRFs. Mis-expressing miR396 at the base of the young Arabidopsis leaf caused an early exit from cell division while reducing the expression of the miR396 at the tip allowed cell division to continue for a longer duration near the tip. Our results demonstrate that leaves with similar shapes can be differently patterned and that this divergent patterning is linked to the expression differences in the regulatory micro RNA, miR396 In conclusion, this study shows that regulators like CIN maintain surface flatness of the Antirrhinum leaf during growth by promoting timely exit from cell division along the proximo-distal and the medio-lateral axes; and it does so by regulating multiple hormone pathways. Although the basic mechanism of patterned cell division and differentiation seems to be conserved among species, the polarities of growth can vary. The variability in the growth polarities could be brought about by changes in the trans-regulation or cis-regulatory changes in the patterning genes.

Growth polarity in leaves – a final discussion Insights into the growth processes of leaf lamina have come from studies on several species including Arabidopsis, Antirrhinum, tobacco and maize. A feature common to the growth of leaf in these distantly related species is the existence of a pronounced growth gradient in the proximo-distal axis -growth at the tip (distal part) is arrested at an early stage while the basal region (proximal part) continues to grow for the longest duration. This is because the cell division is arrested first at the tip at an early stage of development and the arrest progressively spreads towards the base. Along with the strong proximo-distal growth gradient, a milder growth gradient also exists in the medio-lateral axis, such that the cell division arrest travels slightly faster on the leaf margins imparting an overall convex shape to the arrest front. The temporal and spatial progression of the arrest front has not only been implicated in shaping up of a leaf but is also of paramount importance in the maintenance of a flat surface during leaf growth. Although the patterning mechanisms described above seem to operate during leaf growth in many6 species, the molecular mechanisms governing these processes is still in its infancy. Moreover, patterning of leaf growth has been studied only in a handful of model species and, therefore, the information from the vast body of natural variation remains neglected. Proximo-distal growth patterning by CINCINNATA Mutant leaves with altered rates or shapes of the arrest front progression deviate significantly from the normal shape and overall flat structure. Mutation in the CIN gene in Antirrhinum and its orthologues in Arabidopsis cause buckling of the leaf due to excess cell proliferation, which in turn is caused by a delayed progression of the arrest front. CIN-like genes code for TCP transcription factors and are expressed in a broad zone of a growing leaf somewhat distal to the proliferation zone. Even though several direct and indirect targets of CIN-like genes have been identified in various plant species, their role in regulating leaf maturity and surface curvature has remained unclear. The comparison of global transcription profile of wild type and cincinnata mutant of Antirrhinum showed that the expression of genes involved in either signaling or biosynthesis of the major growth hormones were altered in the mutant. By combining DNA-protein interaction, expression analysis, chromatin immuno-precipitation and RNA in situ hybridization, we show that CIN maintains surface flatness by regulating the signaling or level of major plant hormones in developing leaves. CIN promotes cytokinin signaling by directly binding to and thereby promoting the expression of a cytokinin receptor, AmHK4, in a spatio¬temporal manner. Furthermore, it also seems to affect GA level indirectly in young leaves by regulating the spatio-temporal as well as levels of GA-biosynthetic and GA-degrading enzymes. Thus, CIN seems to accelerate maturity in leaf cells along the tip-to-base direction through its effect on the cytokinin and GA signaling pathways. In addition, CIN suppresses auxin signaling more at the margin than in the centre by establishing a margin-to-medial expression gradient of a homologue of the auxin suppressor IAA3, thereby suppressing excess cell proliferation on the margin. Our results uncover an underlying mechanism in a developing leaf that controls curvature of the leaf surface by promotion of timely exit from cell proliferation in the proximo-distal as well as the medio-lateral axes via multiple hormone pathways. Divergent growth polarities in the proximo-distal axis of leaves The morphogenetic gradient in the proximo-distal axis of a leaf is brought about by the dynamic expression of several heterochronic regulators which can include TCP and GRF classes of transcription factors. Interestingly, many of these transcription factors are also regulated post-transcriptionally by micro RNAs. In case of the studied model species, these factors seem to be associated with basipetal growth. The early arrest in cell proliferation at the tip and continued cell division at the base has served as a paradigm in studying leaf growth and has been used to conceptualize the growth of leaves with different shapes. However, the possibility of the existence of different patterning mechanisms during leaf growth in the highly diverse plant kingdom remains unexplored. Our survey of leaf growth patterns in 75 dicot species reveals the existence of four distinct proximo-distal polarities in growth patterns. Using the law of simple allometry, we also show that the differentially growing regions of leaves bear a constant relationship between them during growth. A combination of cell-size studies, histochemical staining and expression analysis reveals a strong correlation among growth pattern, cell size and the cell proliferation status. The cell size studies also indicate that there is a wide variation in the final cell sizes of leaves and the relative contribution of cell division and cell expansion to the final leaf size can be highly variable. Furthermore, we find that the varying growth patterns are linked to changes in the expression pattern of miR396, which controls the expression pattern of cell division regulatory transcription factors, the GRFs. Mis-expressing miR396 at the base of the young Arabidopsis leaf caused an early exit from cell division while reducing the expression of the miR396 at the tip allowed cell division to continue for a longer duration near the tip. Our results demonstrate that leaves with similar shapes can be differently patterned and that this divergent patterning is linked to the expression differences in the regulatory micro RNA, miR396 In conclusion, this study shows that regulators like CIN maintain surface flatness of the Antirrhinum leaf during growth by promoting timely exit from cell division along the proximo-distal and the medio-lateral axes; and it does so by regulating multiple hormone pathways. Although the basic mechanism of patterned cell division and differentiation seems to be conserved among species, the polarities of growth can vary. The variability in the growth polarities could be brought about by changes in the trans-regulation or cis-regulatory changes in the patterning genes.