No description available.

Clouds have pivotal influence on the Earth's hydrological cycle and climate system because they are intricately involved in the dynamical, chemical, and radiative processes within the upper troposphere and lower stratosphere. Cirrus clouds occur at high altitude around the tropopause level and, despite their thin appearance and low optical thickness, they contribute to the radiative balance of the atmosphere. The processes in this region of the atmosphere have become increasingly important for a clear understanding of feedback mechanisms in the climate system. The Canadian designed and built Optical Spectrograph and Infrared Imaging System (OSIRIS) satellite instrument measures the spectrum of sunlight scattered from the Earth's atmosphere at wavelengths from the ultraviolet (280 nm) to the near infrared (810 nm). The limb scattering measurement technique allows OSIRIS to collect information on the vertical profile of atmospheric chemical and particle composition at a resolution of approximately 2km with nearly global daily coverage. In this work, a technique characterizing the distribution of cirrus cloud top occurrences from OSIRIS limb scattering radiance profiles is presented. The technique involves computing residual profiles by comparing normalized measured radiance and modelled molecular density profiles where mismatches between the two traces indicate the presence of clouds. Probability density functions of scattering residuals show the distribution is not a continuum measurement; there is a clear distinction between the cloudy and cloud-free conditions. Observations show high cloud top occurrences in the upper troposphere and lower stratosphere region above Indonesia and Central America. Results obtained using the high altitude cloud detection technique and OSIRIS measurements are compared to those by Sassen et al. (2008) who used CALIPSO nadir measurements and to those by Wang et al. (1996) who used SAGE II solar occultation measurements of cirrus clouds. The cloud detection technique is applied to three case studies. Cloud top detections are used to support results presented in Dessler (2009) who theorized the local relative humidity controls either dehydration or hydration of the lower stratosphere through the efficiency of evaporation of ice lofted by deep convection. The second study makes use of the cloud detection technique to eliminate cloud-containing scans as to identify an Asian Tropopause Aerosol Layer in support of Vernier et al. (2011). Finally, the technique is used to track the dispersion and evolution of the volcanic plume following the Sarychev eruption in June 2009 since monitoring volcanic plumes is an effective way to help mitigate aviation hazards.

The influence of regional processes, such as dispersal, on ecological communities has been the focal point of considerable ecological research. Evidence has shown that dispersal can impact community composition through interactions with predation, the introduction of keystone species, and maintenance of species lost due to competitive exclusion. Ecological communities can be characterized by several metrics including species richness, diversity, evenness, abundance and species co-occurrence patterns. Negative species co-occurrence patterns have historically been attributed to competitive interactions between species causing pairs of species to never co-occur. However, little attention has been paid to the contribution of dispersal on species co-occurrence patterns. I have experimentally investigated the influence of dispersal on species co-occurrence patterns in addition to local species richness, total species abundance, evenness, and Simpson’s diversity. Local species richness significantly increased with dispersal, with variation in total local richness being mainly attributed to differences in the rotifer community. Local diversity, total abundance, and evenness were not significantly influenced by changes in the level of dispersal. Species co-occurrence patterns were greatly affected by changes in dispersal, with negative species co-occurrence patterns peaking at intermediate levels of dispersal. The potential for dispersal to increase the number of rare species within a community suggested that the presence of rare species could be behind the changes in the co-occurrence patterns between dispersal treatments. The effect size of the co-occurrence tests increased with the removal of rare species in the intermediate dispersal treatment and decreased in the remaining dispersal treatments. Likely, through mass effects, the presence of rare species, and the establishment of keystone predators changes in the level of dispersal strongly influenced species co-occurrence patterns. I conclude that external processes, like dispersal, can influence species co-occurrence patterns and that caution should be taken when interpreting the mechanisms driving species co-occurrence patterns across landscapes. / Thesis (Master, Biology) -- Queen's University, 2011-09-28 15:00:40.972

Photoidentification surveys of bottlenose dolphins (Tursiops truncatus) were conducted from December of 2002 through December of 2003 in Chocolate Bay, Texas, and the adjacent Gulf of Mexico area. The research represented the continuation of an ongoing study of the dolphins of this area. Behavioral sampling was carried out on a small resident community of dolphins that seasonally reside in Chocolate Bay, as well as on dolphins found along the gulf coastline. Resident dolphins had a daily behavioral pattern, with peaks of foraging activity in the morning, traveling at midday, and socializing in late afternoon. Gulf dolphins had small mean group sizes of 3.4 and were primarily observed foraging and traveling, with little socializing. When resident and gulf dolphins interacted, the mean group size increased to 12 and the proportion of social behavior increased. Association indices demonstrated no long-lasting associations among adult male dolphins, while strong associations existed between several females. Females revealed two patterns of association; they were either members of a female band with other mother-calf pairs, or were solitary with no strong affiliations with any dolphins other than their calf. Males seemed to disperse upon maturation, which maintained the community size of approximately 35 animals. Behavioral evidence indicates the resident community is matrilinealy related and composed largely of adult females and their offspring. A few adult males remain resident, while most young males disperse from the community and may rove among the gulf population. Although mating probably occurs between resident and gulf dolphins, sources of both maternity and paternity for residents need to be determined, and further behavioral work needs to be carried out to support this hypothesis.

Photoidentification surveys of bottlenose dolphins (Tursiops truncatus) were conducted from December of 2002 through December of 2003 in Chocolate Bay, Texas, and the adjacent Gulf of Mexico area. The research represented the continuation of an ongoing study of the dolphins of this area. Behavioral sampling was carried out on a small resident community of dolphins that seasonally reside in Chocolate Bay, as well as on dolphins found along the gulf coastline. Resident dolphins had a daily behavioral pattern, with peaks of foraging activity in the morning, traveling at midday, and socializing in late afternoon. Gulf dolphins had small mean group sizes of 3.4 and were primarily observed foraging and traveling, with little socializing. When resident and gulf dolphins interacted, the mean group size increased to 12 and the proportion of social behavior increased. Association indices demonstrated no long-lasting associations among adult male dolphins, while strong associations existed between several females. Females revealed two patterns of association; they were either members of a female band with other mother-calf pairs, or were solitary with no strong affiliations with any dolphins other than their calf. Males seemed to disperse upon maturation, which maintained the community size of approximately 35 animals. Behavioral evidence indicates the resident community is matrilinealy related and composed largely of adult females and their offspring. A few adult males remain resident, while most young males disperse from the community and may rove among the gulf population. Although mating probably occurs between resident and gulf dolphins, sources of both maternity and paternity for residents need to be determined, and further behavioral work needs to be carried out to support this hypothesis.

With catches of over 360,000 individuals, Antarctic blue whales Balaenoptera musculus intermedia were harvested to near extinction by commercial whaling in the past century. Antarctic blue whales are an important ecological component of marine ecosystems as they ensure the circulation of nutrients in the pelagic environment making such nutrients accessible for primary production. However, their recoveries; distributions; migrations; large-scale response to environmental variabilities are poorly known. This thesis explored the distribution, seasonal occurrence, behaviour and response of Antarctic blue whales to environmental conditions in the high and low latitudes. I used Antarctic circumpolar acoustic data collected from sonobuoys deployed in the austral summers of 1997 through 2009 during the International Whaling Commission’s Southern Ocean Whale and Ecosystem Research (IWC SOWER) line-transect surveys. I also used recent acoustic data from three autonomous acoustic recorders (AARs) deployed between 2014 and 2015; two of these AARs were deployed on oceanographic moorings in the low latitudes and one AAR was deployed on a dedicated mooring in the high latitudes. Characteristic Z-call and feeding associated D-call of Antarctic blue whales; and sometimes low frequency downsweeping ~28-15 Hz eastern Antarctic fin whale B. physalus calls, were detected using an automated detection template and visual verification methods. I used random forest model to determine pattern of environmental preferences, spatial occurrence and behaviour of Antarctic blue whales. Distance to southern boundary of the Antarctic Circumpolar Current, latitude, longitude and distance from the nearest Antarctic shores were the main geographic predictors of blue whale call occurrence and behaviour during IWC SOWER cruises. Satellite derived sea surface height (SSH), wind stress, wind direction, water depth, sea surface temperature (SST), chlorophyll-a and wind speed were important environmental predictors of blue whale occurrence and behaviour during IWC SOWER cruises. Antarctic blue whale call occurrence and call rates varied significantly in response to inter-annual variabilities of those environmental predictors during those cruises. Migratory Antarctic blue and fin whales were acoustically detected in South African waters between May and August with fin whales present till November. Diel call rate patterns of both whale species varied between seasons. Wind speed, SSH, SST, chlorophyll-a, time of the day and Ekman upwelling index were important predictors of Antarctic blue and fin whale call occurrence and behaviour off the South African west coast. Off the Maud Rise, Antarctica, call occurrences and rates of Antarctic blue whales peaked in March and were detected throughout the whole year suggesting asynchronous migrations to the low latitudes and part of the population remaining in the Maud Rise during winter. Fin whale calls were only detected in January and March. Wind speed, distance to the sea ice extent, sea surface height, sea surface temperature and time of the day were important predictors of Antarctic blue and fin whale call occurrence and behaviour. Information emerging from this thesis will improve the management and conservation of these highly depleted species. This thesis provides the first acoustic recordings of Antarctic blue and fin whales in the southern Benguela ecosystem; and provides preliminary information on which to concentrate further research effort to investigate abundance, distribution and seasonality of these large baleen whale populations in both high and low latitudes. / Thesis (PhD)--University of Pretoria, 2018. / National Research Foundation / Zoology and Entomology / PhD / Unrestricted

No description available.

MESMEG / Department of Mining and Environmental Geology / Muyexe magnesite deposit is situated in the Giyani Greenstone Belt in South Africa. Despite mining activities currently taking place at Muyexe magnesite deposit, little information is available about the geology and geochemistry of the deposit. This has resulted in a gap of information about the nature and character of magnesite, namely; its geology, mineralogy, geochemistry and mode of occurrence. Consequently, there is a need for further investigation of the magnesite deposit. The main objective of the study was to establish the geology and geochemistry of the Muyexe magnesite deposit and to ascertain its mode of occurrence. Further work involved undertaking detailed geological mapping, magnesite and rock sampling for petrographic and geochemical studies using petrographic microscopy and X-ray fluorescence spectrometry and identification of minerals in rocks and magnesite through X-ray diffractometry. A total of 20 magnesite and 4 host rock samples were collected from the Muyexe magnesite deposit. Furthermore, 62 rock samples were collected during geological field mapping of which 16 representative samples were selected for further analysis. X-ray fluorescence spectrometry was conducted on all selected samples of magnesite and rocks. XRD analysis was conducted on 12 rocks and 2 magnesite samples. Mineralogy of the rocks was also confirmed using petrographic microscopy. Detailed geological map of the Muyexe area revealed that the area is dominated by metamorphic ultramafic and mafic rocks. Basalt and peridotite are intrusions within the rock. The serpentinites and peridotites were found to be the source rock for magnesite mineralization, while the peridotite is the source rock for serpentinites rocks. XRD analysis revealed that magnesite in the Muyexe magnesite deposit is associated with silica and dolomite, while XRF data revealed that the following major oxides are present in magnesite as impurities; silicon dioxide (SiO2), calcium oxide (CaO), and iron oxide (Fe2O3). These oxides reduce the quality of magnesite, thus, their removal is necessary during processing. Magnesite of this deposit was found to be of good quality, with an average value of 54.02 wt. %. Magnesite at Muyexe was formed due to precipitation of Mg2+ along the fractures of serpentinites and peridotites due to CO2rich hydrothermal fluids. Magnesite occurs as a cryptocrystalline of the Kraubathtype. / NRF

La question de la contamination du milieu marin par les produits pharmaceutiques et de soin personnel (PPCP) se pose depuis une vingtaine d’années seulement. La principale source de contamination de ces substances se révèle être les stations d’épuration (STP) rejetant directement ou non leurs effluents traités en mer, les traitements employés dans ces stations n’étant pas toujours efficaces pour éliminer ces substances. Le premier objectif de la thèse a été d’évaluer l’état des lieux de la contamination du milieu marin par les PPCP, par une étude approfondie de la littérature, et ce dans les différents compartiments du milieu marin, l’eau de mer, les sédiments et les organismes. La contamination du milieu marin est évaluée principalement par des mesures ponctuelles in situ des concentrations des molécules. Cependant, pour obtenir une vision globale de la répartition de ces contaminants, la multiplication des campagnes d’échantillonnage rend cette méthodologie coûteuse en temps et en matériel. Des approches basées sur la modélisation des concentrations environnementales dans le milieu, par la détermination de concentrations environnementales prévisibles (PEC), peuvent être utilisées en complément ou à la place des mesures in situ. Les PEC constituent la première étape de l’évaluation du risque environnemental (ERE) et permettent d’évaluer l’exposition des organismes non cibles à ces substances. Cependant, pour être précise, cette estimation des concentrations doit être affinée en tenant compte des caractéristiques propres au site étudié. Le deuxième objectif de la thèse a été de proposer une méthodologie de calcul des PEC affinée de molécules pharmaceutiques et de leurs métabolites en zone côtière à l’aide d’un modèle hydrodynamique adapté. Deux molécules modèles ont été choisies, la carbamazépine et la venlafaxine. Afin d’évaluer le risque posé par les molécules pharmaceutiques, il est nécessaire de connaître les effets de ces substances sur les organismes. Actuellement, peu de données sont disponibles sur les organismes marins, contrairement aux organismes d’eau douce. De plus, l’ERE est bien souvent basée sur les résultats de tests standardisés, étudiant les effets à l’échelle de l’individu à des concentrations plus élevées que dans l’environnement. D’autres tests, effectués à des niveaux d’organisation biologique plus bas, sont plus sensibles à des faibles concentrations d’exposition, et sont donc plus pertinents en milieu marin. Le dernier objectif de la thèse a été d’étudier les effets du diclofénac sur la production des prostaglandines, cibles du mécanisme d’action connu de cette molécule, chez des moules méditerranéennes exposées. / The last twenty years, the issue of PPCP contamination of the marine environment caused a growing concern among scientific community. PPCP enter the environment mainly through wastewater treatment plants (WTP), not able to remove completely these substances. The first objective of the thesis was to assess the current state of knowledge on the PPCP occurrence in the different compartments of the marine environment (seawater, sediments and organisms) through a literature review. The contamination of the marine environment is generally assessed by “one-time” measures in situ. However, such monitoring campaigns are time-consuming and costly. Some approaches based on the determination of the predicted environmental concentrations (PEC) could be applied alternatively or complementarily to in situ measures. The PEC calculation is the first step of environmental risk assessment (ERA), to assess the exposure of non target organisms to these substances. However, this estimation needs to be refined to be accurate, by integrating site-specific information. The second aim of the thesis was to propose refined PEC calculation methodologies of pharmaceuticals and their metabolites in a coastal zone using an adapted hydrodynamic model. Two model compounds were chosen, carbamazepine and venlafaxine. In order to assess the environmental risk of pharmaceuticals, it is needful to assess their effects on organisms. Nowadays, few ecotoxicological data are available on marine organisms, contrary to freshwater organisms. Regulatory concept of ERA is often based on a set of short term standard tests carried out at high concentrations. Other tests, implemented at lower organizational levels, are more sensitive to low exposure levels and are more relevant for the marine risk assessment. The last objective was to study the effects of diclofenac on PG production, based on its mode of action, on marine mussels exposed.

The author presents an analysis of how speakers establish references in conversation. Further, this paper focuses on what words of a reference are conventionalized as speakers coordinate multiple times. The author explores how the co-occurrence of the reference terms with the referent can be a good predictor of what words are conventionalized over time. In order to study this, the author created an online version of the reference game from Clark and Wilkes-Gibbs (1986) experiment, where a matcher and director must describe a set of ambiguous shapes to each other many times. By creating an online version of this reference game the author was able to gather significantly more data and analyze the data with computational tools. Results prove that co-occurrence is a useful predictor of terms which are conventionalized, providing a first step for accounting for statistical inference in the process of conventionalization.