Tropical cyclones claim a huge number of lives and cause substantial damage to property and crops in many regions each year. Southern Africa is no exception. This makes the process of forecasting tropical cyclones of great importance to the region’s economy and to public safety. Skillful seasonal forecasts of tropical cyclone activity could be used to warn the communities affected by tropical cyclones of the likely occurrence of such systems ahead of the cyclone season. This could result in reduced damage and fatalities associated with such systems. Both statistical and dynamical techniques have been employed in an attempt to predict tropical cyclone activity on a seasonal time scale over a number of ocean basins. The skills of such techniques vary from one technique to another and from one basin to another. This study investigates the predictability of tropical cyclone activity on a seasonal time scale over the southwestern Indian Ocean (SWIO) by nesting a regional climate model (RCM), the RegCM3 within a coarse-resolution atmospheric general circulation model (AGCM), the ECHAM4.5. The national meteorological centres of most southern African countries do not have the required dedicated computational resources to run the high-resolution GCMs that are suitable to predict these systems operationally. However, these systems can be very devastating on the southern African region and need to be predicted on various time scales, including the seasonal time scale. Therefore, it is instructive that research be done to better our understanding of these systems and their predictability using physical models. This study examines the simulations of the genesis locations and the number of tropical cyclones produced in RCM integrations nested within an AGCM forced by observed sea-surface temperatures (SSTs). The season of interest is the mid-summer period of December to February. Four members of the AGCM generated at the International Research Institute for Climate and Society (IRI) are used to force the RCM. Four-month integrations over a 10-year period (1991/92-2000/01) are performed. An objective procedure for detecting model-generated tropical cyclones is applied to this ensemble. Some characteristics of the simulated cyclones are compared with the observations. In addition, some statistical techniques are employed to evaluate the capability of the RCM to reproduce some aspects of the observed tropical cyclones during the aforementioned period. The results show that there is a good agreement between two of the simulated and observed environmental variables that influence tropical cyclone formation, viz. vertical wind shear and relative vorticity. In particular, the simulated and observed vertical wind shear show a similar pattern in most parts of the model domain. With regards to the relative vorticity, the highest agreement is found in the Mozambique Channel and in the region east of Madagascar. In addition, there is an appreciable agreement between the simulated and observed tropical cyclone characteristics such as tropical cyclone genesis locations and frequency. The model also simulated the interannual variability in the tropical cyclone frequency skillfully. AFRIKAANS : Tropiese siklone is verantwoordelik vir ‘n goot aantal sterftes en veroorsaak beduidende skade aan eindom asook oeste oor etlike areas elke jaar. Suidelike Afrika is nie ‘n uitsondering nie. Hierdie verliese maak die voorspelling van tropiese siklone van groot belang vir die gebied se ekonomie asook vir publieke veiligheid. Vaardige seisoenale voorspelling van tropiese sikloon aktiwiteit kan gebruik word om gemeenskappe wat onderhewig is aan die invloed van tropiese siklone te waarsku oor die kans vir sulke sisteme om voor te kom voordat die tropiese sikloon seisoen ‘n aanvang neem. Vroegtydige waarskuwings kan tot gevolg hê dat daar minder verwant skade en laer sterftes is. Beide statistiese en dinamiese tegnieke is al in die verlede gebruik om tropiese sikloon aktiwiteit oor verskeie oseaankomme op ‘n seisoenale tydskaal te probeer voorspel. Die vaardigheid van hierdie tegnieke hang af van die tipe tegniek wat gebruik word asook watter oseaankom beskou word. Hierdie studie ondersoek die voorspelbaarheid van tropies sikloon aktiwiteit op ‘n seisoenale tydskaal oor die suid-westelike Indiese Oseaan deur gebruik te maak van ‘n streeksmodel, die RegCM3, genes in ‘n growwe-resolusie algemene sirkulasie model van die atmosfeer, die ECHAM4.5. Die nasionale weerdienste van die meerderheid Suider-Afrikaanse lande beskik nie oor die nodige rekenaars om geskikte hoë-resolusie algemene sirkulasie modelle te loop om sodanige sisteme mee operasioneel te voorspel nie. Desnieteenstaande kan hierdie tropiese sisteme verwoestend wees en daarom behoort hulle voorspel te word op verskeie tydskale, insluitende seisoenale tydskale. Dit sal dus insiggewend wees om navorsing te doen om sodoende ons begrip oor hierdie sisteme en hul voorspelbaarheid te verbeter deur gebruik te maak van fisiese modelle. Hierdie studie gaan ondersoek instel oor die simulasie van tropiese siklone oor hul ontwikkelingsgebiede en die aantal tropiese siklone wat ‘n streeksmodel, genes in ‘n algemen sirkulasie model van die atmosfeer wat geforseer word deur waargeneemde see-oppervlak temperature, kan produseer. Die seisoen van belang is die mid-somer periode van Desember tot Februarie. Vier ensemble lede afkomstig vanaf die algemene sirkulasie model wat geloop is by die International Research Institute for Climate and Society word gebruik om die streeksmodel mee te forseer. Model integrasies word oor ‘n 4-maand periode gedoen en vir ‘n 10-jaar tydperk (1991/92-2000/01). ‘n Objektiewe vorteks opsporingsprosedure word dan toegepas op die 4-lid ensemble om model-geskepte tropiese siklone te identifiseer. Sommige van die karakteristieke van die gesimuleerde siklone word dan vergelyk met die waargeneemde tropiese stelsels. Hiermee saam word statisiese tegnieke ingespan vir die genoemde tydperk om die vermoë van die streeksmodel te ondersoek om sekere aspekte van waargeneemde storms te herproduseer. Die resultate wys dat daar ‘n goeie ooreenkoms is tussen twee van die gesimuleerde en waargeneemde omgewingsveranderlikes wat tropiese sikloon ontwikkeling beinvloed, nl, vertikale windskuiwing en relatiewe vortisiteit. In besonder het die gesimuleerde en waargeneemde vertikale windskuiwing ooreenstemmende patrone gelewer oor die grootste gedeelte van die streeks model-area. Wat relatiewe vortisiteit betref, is die beste ooreenkoms oor die Mosambiek kanaal en in die gebied oos van Madagaskar gevind. Verder is daar ‘n sterk ooreenkoms tussen die gesimuleerde en waargeneemde tropiese sikloon karakteristieke soos by die tropiese siklone se ontwikkelingsgebiede asook hul frekwensie. Die model he took daarin geslaag om die inter-jaarlikse veranderlikheid van tropiese sikloon frekwensie suksesvol te simuleer. / Dissertation (MSc)--University of Pretoria, 2010. / Geography, Geoinformatics and Meteorology / MSc / Unrestricted

Cette étude a pour but d'identifier les principales maladies coralliennes, de quantifier leurs prévalences sur les récifs de la Réunion, d'Afrique du Sud et de Mayotte et de déterminer leurs variations spatiales et saisonnières. Les résultats ont révélé la présence de six grands types de maladies coralliennes. Les prévalences totales moyennes des maladies ont été plus élevées à la Réunion (7.5 ± 2.2%) qu'en Afrique du Sud (3.9 ± 0.8%) et qu'à Mayotte (2.7 ± 0.3%). Les genres coralliens Acropora et Porites ont été les plus vulnérables aux maladies dans les trois régions étudiées. Des variations spatiales et saisonnières ont été détectées pour la maladie de la bande noire (BBD) et les syndromes blancs (WS) à la fois à la Réunion et en Afrique du Sud avec des prévalences plus élevées sur les récifs peu profonds et pendant la saison chaude. Ce travail a également pour but de caractériser deux maladies non décrites à ce jour : le syndrome des patches blancs (PWPS) et le syndrome du patch noir (PBPS) chez Porites. PWPS, observé à fois à la Réunion, en Afrique du Sud et à Mayotte est caractérisé par d'importantes fragmentations tissulaires généralement associées à des corps ovoïdes basophiles ressemblant à des agrégats bactériens. L'analyse bactérienne a révélé une grande variabilité entre les tissus infectés et sains. L'identification des pathogènes responsables de PWPS a également été réalisée en laboratoire. Sur les 14 souches bactériennes sélectionnées et testées, seule la P180R, génétiquement proche de Vibrio tubiashii a généré des signes de PWPS. Pour finir, PBPS, une forme atypique de BBD a été observée sur les récifs de la Réunion. Les suivis réalisés ont montré des variations spatiales et saisonnières avec des prévalences plus élevées sur le platier et pendant l'été. L'histologie a mis en évidence la présence de cyanobactéries et de corps basophiles dans les tissus infectés du corail. L'analyse génétique a révélé la présence d'une plus grande diversité de taxons dans les tissus infectés par PBPS que dans les tissus sains représentés par le genre Vibrio. / During the past two decades, the emergence and spread of infectious diseases have caused substantial declines in the biodiversity and abundance of reef-building corals. Despite their increased global prevalence and virulence, little is known about coral diseases on Indian Ocean coral reefs. This study aims to fill this gap in knowledge by identifying the main coral diseases and quantify their prevalence at three localities Reunion, South Africa and Mayotte, determining their spatial distribution and seasonal variation. Principal findings of this study demonstrated the presence of six main coral diseases including black band disease (BBD), white syndromes (WS), pink line syndrome (PLS), growth anomalies (GA), skeleton eroding band (SEB) and Porites white patch syndrome (PWPS). The overall disease prevalence was higher in Reunion (7.5 ± 2.2%; mean ± SE) compared to South Africa (3.9 ± 0.8%; mean ± SE) and Mayotte (2.7 ± 0.3%; mean ± SE). Acropora and Porites were the genera most vulnerable to disease. Spatial variability was detected in both Reunion and South Africa with BBD and WS more prevalent on shallow than deep reefs. There was also evidence of seasonality in two diseases: BBD and WS, their prevalence being higher in summer than winter. Corals exhibiting signs of PWPS revealed extensive tissue fragmentation, generally associated with ovoid basophilic bodies resembling bacterial aggregates within the mesoglea of the body wall. Other organisms, including Cyanobacteria, Nematoda, Ciliata and endophytic algae, were also observed on diseased tissues and were generally associated with the dead epidermis and cell debris. Results of 16S rRNA sequence analysis revealed a high variability between bacterial communities associated with PWPS-infected and healthy tissues in Porites lutea. Several bacterial ribotypes affiliated to potential putative pathogens notably Shimia marina and Vibrio hepatarius were consistently found among the 16S rRNA sequences derived from the PWPS lesions, and absent and/or poorly represented in HT. Primary pathogens involved in the PWPS were also investigated in this study using traditional culturing techniques and laboratory infection trials. Of the 14 isolates selected for the inoculation trials, only the bacterial strain P180R mostly phylogenetically closely related8 to Vibrio tubiashii with its closest known sister taxon, V. hepatarius, was shown to cause signs resembling those of PWPS and satisfied the four Henle-Koch’s postulates. P180R displayed focalised and progressive tissue paling 12 h after inoculation and visible lesions of PWPS were observed 12 h thereafter. Signs of PWPS appeared on 90% of the exposed coral fragments (27 of 30) under controlled environmental conditions. Moreover, the virulence of this marine pathogen was tested and seemed to be strongly dependent on seawater temperature, resulting in significantly higher tissue loss at 30°C than 28°C and 26°C. Finally, a multidisciplinary approach involving field surveys, gross lesion monitoring, histopathology and 454-pyrosequencing was investigated to characterize an atypical form of BBD named PBPS. Histology revealed cyanobacterial penetration of the compromised tissue as well as the presence of basophilic bodies resembling bacterial aggregates in the living tissue, adjacent to the bacterial mat. Bacterial 16S rRNA sequences yielded a broader diversity of bacterial taxa in PBPS-infected tissues than in healthy tissue, represented by the genus Vibrio (24.9%), followed by sulfate-reducers or sulfide-oxidizers such as Desulfovibrio (20%), Clostridium (12.9%) and Arcobacter (9.9%). PBPS appears to be a multi-stage disease triggered by cyanobacterial invasion and resulting in secondary infections by environmental bacteria that grow in mucus-like decomposing tissue.

The Indian Ocean has experienced a process of profound change in its political and strategic map since World War II. This began with the British withdrawal from East of Suez, and was followed by the entry of the superpowers into the Indian Ocean, the growth of superpower naval rivalry, and the proliferation of security problems of the states in the region. The essence of these developments is the transformation of the Indian Ocean from the stability of one-power domination to the instability of superpower rivalry. The thesis examines the process of this transformation and the Sri Lankan response from a historical perspective. The transformation of the power structure in the Indian Ocean was essentially an outcome of the changes in power configurations in world politics. The growth of superpower rivalry in the Indian Ocean must be understood in relation to the evolution of political, economic, and strategic interests of the superpowers, advances in weapons systems and naval technology, and political developments in the region. The superpower naval rivalry has three interrelated elements, viz, naval deployments, weapons deals, and jockeying for bases/logistic support in the region. It evolves in three phases: from 1968 to the 1973 oil crisis; from the oil crisis to 1978; and since 1978. There are definite linkages between superpower naval rivalry and the conflict patterns in the region. The states in the region count on the superpowers for their security because of the inherent weaknessess of the ruling elites in the region, the limits of their security options, and economic dependence. The invariable outcome is a chain reaction resulting in military pacts, puppet governments, political supression, and proxy war, which forms the texture of the international politics of the Indian Ocean region. Sri Lankan responses to superpower naval rivalry can be explained in relation to the geo-political framework of her strategic thinking, and her internal political and economic processes. In the period 1948-56, Sri Lanka identified herself with the British defence structure in the Indian Ocean. With the changes introduced by the M.E.P. regime, non-alignment became the foreign policy approach of Sri Lanka after 1956. In accordance with the growth of superpower naval presence, Sri Lanka became more sensitive to Indian Ocean strategic issues in the 1960s. After 1970, Sri Lankan policy towards the Indian Ocean took a more coherent form and was designed to balance two considerations - first, at the sub-regional level, how to deal with India; and at the Indian Ocean level, how to check superpower naval rivalry and the increasing militarization of the Indian Ocean. This was reflected in Sri Lanka's proposal for an Indian Ocean Peace Zone (IOPZ). After 1977, under the changed internal and international situation, Sri Lanka soft-pedalled her earlier more articulated position regarding superpower naval riavlry in the Indian Ocean. / Arts, Faculty of / History, Department of / Graduate

The December 2004 Indian Ocean Tsunami wrecked thousands of lives, homes, and livelihoods - losses that could have been avoided with timely and better information. A resource such as information is needed at a fundamental level much like water, food, medicine, or shelter. This dissertation examines the development of the Thai information society, in terms of the share of information workforce and the level of diffusion of information and communication technologies (ICT), as well as, the role of the Thai information society in response to the tsunami disaster. The study combined the historical and political economy analyses in explaining factors influencing the growth of information workforce and the development of ICT in Thailand. Interviews conducted in 2007-08 revealed the Thai information society responded to the 2004 Tsunami - the first global internet-mediated natural disaster - in two areas: on-site assistance in collecting and recording identification information of tsunami disaster victims and on-line dissemination of disaster relief information. The effectiveness of ICT institutions in providing the tsunami disaster relief efforts and increasing the development of the information society were assessed using statistical procedures analyzing the perceptions of the Internet-based survey respondents. The disaster effects on survey respondents were also assessed. The study's findings include: (1) the Thai information sector development pattern confirmed a key difference between development patterns of information sectors in developed and developing countries, (2) the increasing number of Thai information workers was due more to the expansion of government than the expansion in the manufacturing and service sectors during the 1997-98 Asian financial crisis, (3) Thailand's expansion of ICT infrastructure was influenced not only on the basis of economic profitability but also by political desirability, and (4) volunteers were crucial in humanitarian aid and disaster relief.

MENVSC (Climatology) / Department of Geography and Geo-Information Sciences / Subtropical anticyclones locate and modulate weather and climate over subtropical belts for both the Northern and Southern Hemispheres. This study investigates the spatio-temporal variability of the Mascarene High over the South Indian Ocean on (anomalous) weather and climate over southern Africa at intraseasonal, seasonal, interannual, multidecadal and event time-scales. The Mascarene High is located 25-35°S, 40-110°E, playing a vital role in day-to-day weather and climate patterns conditions over southern Africa. Spatio-temporal characteristics of the Mascarene High investigated in this study span the period 1985-2014 and 2071-2100, using NCEP-NCAR reanalysis datasets for present-day climate observations and the Conformal-Cubic Atmospheric Model (CCAM) for future projections. The Mascarene High is analysed using mean sea level pressure (MSLP) extracted from ECMWF ERA-interim monthly reanalysis data. The Mascarene High is also subjected to Principal Components Analysis, depicting eastern displacements of the weather system to be dominant for weather and climate fluctuations over southern Africa. The Mascarene High migrates south (north) during austral summer (winter) and is centred over the eastern Indian Ocean in summer in connection with the Indian Ocean Subtropical Dipole. Event scale analysis is also employed for investigating Mascarene High blocking and induced anomalous weather. Mascarene High blocking leads to anomalous rainfall events over southern Africa associated with tropical cyclones, cut-off lows and cloud bands. There is also a vital geographical variability of the Mascarene High development, distribution and movement in the South Indian Ocean at the different time-scales. Projections of the Mascarene High indicate a shift in mean location as a result of future expansion and intensification. This projected expansion and intensification is expected to shift tropical cyclone trajectories equatorward, with the baroclinic structure of cold fronts expected to shift poleward affecting changes in the weather and climate of southern Africa. This finding is important as it projects changes in weather and climate conditions over southern Africa in a changing climate due to increased greenhouse gas emissions.

The concern of the diploma thesis is the geostrategic role of the base on the island Diego Garcia. It deals chronologically with the evolvement of this role since the base was established until the present time. Apart from the analysis of the extent, motivation and reasons of the evolvement, the explanation of all these is provided as well. The research is based on the theories formulated by admiral Alfred T. Mahan who was primarily concerned with the agenda of a naval superpower. The issue of bases is directly linked to that subject. The analysis pays attention to physical development of the facilities on the island which to a certain extent reflects the strategic role of the base. It also further examines the regional and global context which is deemed to be crucial for the better understanding of the function the base had for the United States. Practical usage of the base is analysed for a better explanation of the role the base played as some of the contemporary documents are still classified and unavailable. According to the research, the role the base played changed several times but it is very difficult to point out the main factor that caused the change. Most probably, it was caused by a combination of several factors.

The master thesis called US-India Strategic Partnership as a Balance for China's Increasing Power examines development of relationship between USA and India in the years 2000-2011. American foreign policy toward India has been transformed in this period; it has evolved from open hostility during Cold War and mistrust in the nineties to the position when it is helping India to gain status of global importance. Improvement of US-India ties are explained by the need of the United States to contain increasing Chinese power. Main arguments of the analysis are based on the realistic balance of power theory, which is further enhanced by the by Joseph Nye's three dimensional concept of power. The thesis therefore distinguishes three different sources of threat to American dominant position caused by China. These sources are following: expanding China's sphere of influence into Indian Ocean and South China Sea; US-China bilateral trade deficit and high amount of American bonds owned by China, challenge to the legitimacy of American power by soft power of China. American efforts to establish cooperation with India in order to balance Chinese influence can be founded in all of these issues. The thesis concludes that motivation of the United States to enter into a strategic partnership with India can be...

Ces travaux de recherche se sont focalisés sur la zone Océan Indien austral et ont permis d'améliorer les connaissances scientifiques sur la provenance des masses d'air polluées, sur leur distribution spatiale, sur la contribution relative des zones sources à la charge en polluant mesurée, et sur les propriétés optiques des aérosols détectés. La prépondérance de l'influence du transport des masses d'air polluées en provenance d'Afrique Australe et d'Amérique Latine à la concentration en polluant dans le sud-ouest de l'océan Indien a ainsi été démontrée en utilisant des mesures par spectrométrie infrarouge à transformée de Fourier et des modèles de dispersion de panache couplés à des bases de données d'émission. Une voie de transport privilégiée reliant l'Asie du sud-est au sud-ouest de l'océan Indien dans la haute troposphère en Juillet-Août, ainsi que l'apport en CO résultant, ont été identifiés pour la première fois. La variation saisonnière de la concentration en ozone troposphérique dans le sud de l'océan Indien a également été mise en évidence, ainsi que son lien avec les émissions de précurseurs d'ozone provenant des feux de biomasse se produisant en Afrique Australe et en Amérique Latine. L'analyse des données photométriques AERONET a permis d'établir une climatologie des caractéristiques optiques des aérosols à la verticale de la Réunion, qui apparaît comme étant un site relativement propre dont la troposphère est principalement affectée par les aérosols marins tout au long de l'année, et également par les aérosols de feu pendant la saison des feux australe. De plus, des campagnes de mesure avec lidar et photomètre embarqués à bord d'un navire sillonnant l'océan Indien austral a donné accès à l'évaluation de l'extension verticale et des propriétés optiques d'un panache d'aérosols de feux provenant principalement d'Amérique Latine et d'Afrique Australe, mais aussi d'Asie du sud-est. / This thesis focused on the southern Indian Ocean area and contributed to improve our scientific knowledge on the origin of polluted air masses, on their spatial distribution, on the relative contribution of the identified source regions to the measured pollutant loading, and on the optical properties of the encountered aerosols. The potential primary sources for CO throughout the south-western Indian Ocean troposphere are southern Africa and South America. A secondary potential contribution from Southeast Asia and Indonesia-Malaysia was identified in the upper troposphere, especially in July and August. The seasonal variation of tropospheric ozone concentration in the southern Indian Ocean is highlighted, and its link to wintertime long range transport of tropospheric ozone precursors emitted in biomass burning plumes from southern America and Africa is evidenced. The analysis of sun photometer measurements gave access to a climatology of the optical properties of aerosols in Reunion Island, showing this site can be considered as a clean site, mostly influenced by marine aerosols throughout the year, and also by biomass burning aerosols during the southern hemisphere biomass burning season. A unique data set of shipborne measurements has been collected with a dual Rayleigh-Mie lidar and a handheld sun photometer aboard a research vessel crossing the southern Indian Ocean, and the time evolution of the encountered marine and biomass burning aerosols extinction properties and vertical extension are documented.

L'objectif principal de cette thèse était de reconstituer l'évolution de la circulation intermédiaire depuis la dernière période glaciaire à partir de carottes de sédiments marins prélevées dans le golfe du Bengale GB, la Mer d’Arabie MA et l’océan Indien équatorial oriental OIEO. La stratégie scientifique mise en œuvre inclut l’étude des assemblages et de la géochimie des foraminifères benthiques, afin de reconstruire les changements de source et de ventilation des masses d’eau. Les résultats obtenus dans le GB ont permis de restituer les changements hydrologiques à profondeur intermédiaire à haute résolution temporelle au cours des derniers 40 ka. Les enregistrements témoignent de changements dans la source des masses d’eau, entre l’Océan austral avec les eaux antarctiques intermédiaires AAIW et les eaux Nord Atlantique NADW, à l’échelle glaciaire-interglaciaire mais aussi lors des événements millénaires. Ce travail a aussi permis de fournir les premiers enregistrements à haute résolution temporelle des rapports élémentaires des foraminifères benthiques (Mg/Ca, Sr/Ca, U/Ca et Li/Ca) dans le GB et en MA. Ces résultats permettent notamment de mieux contraindre la pénétration des AAIW vers le nord depuis la dernière période glaciaire. La reconstruction de la concentration en ion carbonate permet également de discuter des relations entre les variations de la circulation intermédiaire et les changements profonds du cycle du Carbone à l’échelle globale, notamment via les échanges se produisant dans l’Océan Austral. Nous avons également fourni dans ce travail les premiers enregistrements de Cd/Ca et de Ba/Ca continus et à haute résolution dans le nord de l’océan Indien, pour reconstituer les modifications passées de la teneur en éléments nutritifs. Les enregistrements géochimiques dans l’OIEO témoignent de profonds changements des propriétés des masses d'eau intermédiaires, associées aux changements de circulation. / The main objective of this study was to reconstruct the evolution of the intermediate water circulation since the last glacial period by the investigation of marine cores collected from the Bay of Bengal (BoB), Arabian Sea (AS) and Eastern Equatorial Indian Ocean (EEIO). The scientific strategy involves benthic foraminiferal assemblages and geochemical proxies to better constrain past changes in the source and ventilation of water masses. Records from the BoB allowed reconstructing hydrological changes at intermediate depth over the last 40 cal kyr. The records highlight changes in the source of water masses, with a balance between the contribution of southern Antarctic Intermediate Water (AAIW) versus North Atlantic Deep Water (NADW) at glacial-interglacial timescale as well as during millennial events. This work also provided the first high-resolution benthic foraminifera elemental ratio records (Mg/Ca, Sr/Ca, U/Ca and Li/Ca) from the BoB and the AS. These records especially help to better constrain the northward penetration of AAIW over the last glacial period. The reconstruction of the carbonate ion concentration allowed to discuss the relationships between the intermediate water circulation and deep changes in the global Carbon cycle, with a special interest for the Southern Ocean. This work also provides the first continuous and high-resolution benthic Cd/Ca and Ba/Ca records in the northern Indian Ocean, could reconstruct past changes in the nutrient content. Geochemical records from the EEIO exhibit strong changes in the chemical properties of the intermediate water masses, related to global circulation changes in the area.

Die Atyidae sind eine artenreiche Familie weit verbreiteter Süßwassergarnelen, zu der sowohl landumschlossene als auch amphidrome Arten gehören. Ein großer Teil der Atyidae ist im Indopazifik verbreitet, einer Region, die für ihre geologisch komplexe Geschichte bekannt ist. Die Evolution der Atyidae in Kombination mit der Taxonomie, die bis ins frühe 19. Jahrhundert zurückreicht, führt zu einem hohen Maß an taxonomischer Unsicherheit. Das zeigt sich darin, dass über 70 % der Artenvielfalt in einer Gattung – aus insgesamt 54 der gesamten Familie – enthalten sind. Diese Gattung, Caridina, ist nicht monophyletisch. Eine vollständige Überarbeitung fehlt jedoch noch aus mehreren Gründen; darunter unvollständige Kenntnisse über entsprechende Verwandtschaftsverhältnisse, das Abwägen zwischen der Arbeit mit Museumsexemplaren und dem Sammeln im weiten Verbreitungsgebiet der Familie sowie die Plastizität ihrer Morphologie. Ich führe eine Meta-Analyse der Biogeographie der Landmassen innerhalb der Grenzen des Indischen Ozeans durch. Die bei mehreren Taxa festgestellten Tendenzen belegen, dass die physische Verbindung zwischen den Landmassen für die Ausbreitung weniger wichtig war als der durch ökologische Bedingungen ausgeübte Druck. Dann vergleichen wir Extraktionsmethoden, abwägend zwischen DNA-Ausbeute und -Integrität sowie Probenkonservierung. Wir zeigen, dass die Maximierung der DNA-Ausbeute durch Ganzkörperlyse jedoch möglich ist, ohne die Merkmale im Exoskelett zu beschädigen. Abschließend verwenden wir einen Exon-Capture-Ansatz, um eine zeitkalibrierte Phylogenie der artenreichsten Gruppe innerhalb der Atyidae, d. h. Caridina und ihrer Verwandten, zu erstellen. Wir erläutern Details über die Evolution lebensgeschichtlicher Merkmale sowie der Biogeographie und zeigen, dass die Geschichte der Familie eng mit dem Indopazifik verbunden ist und schaffen einen robusten phylogenomischen Rahmen, der zukünftige Bemühungen zur Überarbeitung der Familie erleichtern wird. / The Atyidae is a speciose family of widely distributed freshwater shrimps that includes landlocked and amphidromous species. A large portion of the atyid diversity is distributed in the Indo-Pacific, a region known for its geologically complex history. Its evolution combined with a vast distribution range and a taxonomy that dates back to the early nineteenth century amounts to a high degree of taxonomic uncertainty, which is illustrated by the fact that over 70% of its diversity is contained within one genus out of the 54 in the family. This genus, Caridina, is not monophyletic, but a full revision is still lacking for several reasons, including incomplete knowledge about its relationships, the compromise between working with museum specimens and collecting new specimens along its wide distribution, and the plasticity of its morphology. My coauthors and I conduct a meta-analysis of the historical biogeography of the landmasses within the boundaries of the Indian Ocean. Trends shown by multiple taxa demonstrate that physical connectivity between said landmasses is less important to dispersal than the pressure exerted by ecological conditions. Then, we compare extraction methods in terms of the trade-off between DNA yield and integrity and specimen preservation. We show that, whereas traditional extraction methods are still useful to obtain viable DNA from museum samples a few decades old, maximising the DNA yield through whole-body lysis is possible without damaging characters in the exoskeleton. Finally, we proceed to use an exon-capture approach to produce a time-calibrated phylogeny of the most diverse group in Atyidae, i.e., Caridina and their kin. We reveal details about the evolution of life history traits as well as biogeography, showing that the history of the family is intimately linked to the Indo-Pacific and constructing a robust phylogenetic framework that will facilitate future endeavours to revise the family.