>Magister Scientiae - MSc / Two species of Chrysaora are described from the northern Benguela ecosystem: C. fulgida and C. africana. These species can be diagnosed by a combination of morphological features including lappet and tentacle number, shape oflappets, colouration patterns (alive), shape of the proximal portion of radial septa, gastrovascular pouch shape, point of attachment of gonads and the presence or absence of small raised nematocyst warts on the exumbrellar surface. Objective, quantitative statistical analyses coupled with molecular sequence data support the qualitative morphological dissimilarity observed, as these analyses unambiguously diagnose C. fulgida and C. africana as two distinct species. There is a strong superficial resemblance between the C. fulgida material described here and the preserved specimens of C. hysoscella examined at the Natural History Museum, London. Thorough investigation does however allow the separation of these two species. morphological features found to be dissimilar were the proximal portion of the manubrium, gastrovascular pouch shape and the presence or absence of sperm sacs. Objective, quantitative statistical analyses support these findings. Nuclear sequence variation suggests considerable divergence between the two species but additional molecular work is needed.

Philosophiae Doctor - PhD / Enhancing our understanding of wetland properties and the ecosystem services provided by wetlands within a dynamic landscape, is fundamental to ensuring appropriate management strategies for enhanced biodiversity and ecosystem benefits. With increased anthropogenic activities and the impacts of climatic variability, a better understanding of the factors influencing the water balance dynamics of wetlands can provide insight into how wetlands respond to change. The main aim of the research was to improve the understanding of the spatial and temporal availability of water and storage of a depression wetland in a semi-arid climate, and to relate these to ecosystem functions. As ecosystems are intricately connected to society, a secondary aim of the research was to gain insight to how wetland ecosystems, within a changing climate and landscape, provide benefits to society, and add value to human-wellbeing. Soetendalsvlei, a shallow freshwater depression, and one of the few coastal freshwater lakes of South Africa, was the focus of the research.

Integrating green or blue space into cities can provide environmental and public health benefits which maximize urban sustainability. One type of green/blue infrastructure that has been understudied is urban stormwater ponds, which are used to manage stormwater runoff. Their performance is typically only evaluated in terms of hydrological functions, with little focus on their capacity to provide ancillary benefits to communities. In this exploratory study, an online survey was distributed to six neighbourhoods in the City of Ottawa, ON to gain insight into the social value of urban stormwater ponds. The results revealed that despite some disadvantages, most respondents visited their neighbourhood stormwater ponds regularly and largely appreciated the cultural ecosystem services provided by these ponds, such as opportunities for experiencing nature, especially wildlife, and outdoor recreation. These findings can be used to improve the multifunctionality of stormwater ponds and optimize both environmental and social sustainability outcomes.

Due to growing human demands for freshwater within the last century, manmade flow alterations are now a common characteristic of rivers worldwide. Alterations to the volume and timing of flows in rivers are known to negatively impact aquatic biodiversity, biological productivity and ecosystem functions such as nutrient cycling. While previous research has focused on the effects of flow reductions and spates, there is a lack of knowledge on how high flows across longer timespans (i.e. ‘enhanced flows’) impact the structure of river communities and the integrity of ecosystem functions. The Utah Reclamation, Mitigation and Conservation Commission has expressed interest in reducing enhanced flows in a central Utah river so as to benefit aquatic habitat and native game fish. With their funding support, I collected aquatic invertebrate and ecosystem function data under natural and enhanced flow conditions throughout Sixth Water Creek and Diamond Fork River. These data were supplemented with historical invertebrate data collected by BIO-West, Incorporated. For each river segment, I tested whether flow volume and variation had relationships with the density and health of streambed invertebrate communities. I also sought to determine how these flow metrics affected leaf litter breakdown, primary production and stream metabolism (i.e. the production and respiration of organic matter). Here, I demonstrate that enhanced flows impact streambed invertebrate communities differently in each river segment, in addition to suppressing stream metabolism system-wide. While streambed communities were mostly unaffected by enhanced flows in Sixth Water Creek, density and community health exhibited negative relationships with flow metrics in Diamond Fork River. In the Lower Diamond Fork mainstem, proportions of pollution-tolerant taxa increased as peak flows increased, while streambed invertebrate density decreased as mean monthly flows increased. Moreover, enhanced flows appeared to severely impact the production of organic matter in Sixth Water Creek and Lower Diamond Fork River. This disproportionate suppression of production over respiration shifted the river towards greater reliance on out-of-stream energy sources. These results demonstrate the importance of considering spatial gradients when investigating community responses to flow alterations, and also reveal how river ecosystems are threatened with losses of in-stream energy supplies under enhanced flows.

A major challenge in freshwater ecosystem management is to predict future changes in streamflow regime. This thesis focused on identifying and modeling specific characteristics of streamflow that are important to stream ecosystems. The need to evaluate the potential impacts of climate change on stream ecosystems makes it important to study how streamflow regime may change. In this thesis we sought to advance understanding of the effect of climate change on streamflow regime by (1) examining the spatial variation in streamflow attributes across the continental US, (2) modeling how these streamflow attributes vary with current climate and watershed features, and (3) using this model with future climate projections of changes in precipitation and temperature to predict how streamflow attributes change with climate change. We used long-term daily flow measurements for 601 gauged streams whose watersheds were in relatively unimpaired condition to characterize streamflow regimes. Sixteen streamflow variables were identified which in our judgment sufficiently characterized aspects of the streamflow regime most relevant to stream ecosystem structure and function. These are computed for each stream. Principal component analysis with Varimax rotation reduced the dimensionality to five uncorrelated streamflow factors that quantify lowflow, magnitude, flashiness, timing and constancy. These independent factors were used to hereafter classify the streams based on distances in factor space into three broad classes which were further divided into eight classes. We used Random Forests to develop a model to predict these stream classes using watershed and climate attributes. The model had an accuracy of about 75%. Downscaled climate projections of precipitation and temperature were used to predict the changes in these stream classes by 2100 using the RF model. Thirty-three percent of selected sites were predicted to change into a different stream class by 2100. The least changes were predicted in snow-fed streams in the west while most of changes were predicted for rain-fed small perennial streams and intermittent streams in the central and eastern US. Class changes predicted, due to projected climate change provide a basis for (i) considering the extent of projected changes and (ii) formulating approaches to protect ecosystems that may be subject to change.

Coexisting ungulate-eating carnivores--lion, spotted hyena, cheetah, leopard, African wild dog, black-backed jackal, common jackal, and six species of vulture--are examined in East Africa's Serengeti ecosystem. Niche similarities year-round, by season, and by location are described using food, habitat, time of hunting, and other variables. Intraspecific niches of cheetah sex, age, and social groups show that male coalitions differ most from the others in hunting behavior and habitat use. Tests using the carnivore data failed to support hypotheses about niche breadth variation, niche overlap variation, range of food items, and niche inclusion. Densities of the five largest Carnivora in the 35,500 square kilometer ecosystem are 0.513/sq km; including the two jackals gives a density of 1.55/sq km. Their prey--30 ungulate species--are 84 .85/sq km. Prey and predator ratios suggest that the Serengeti Plains in 1977 had a three-fourthsdecrease in relative abundance of prey to predators from wet season to dry season . Year-round the Ngorongoro Crater had a prey:predator ratio s lightly larger than that of the dry season Serengeti Plains. Literature review suggests that cleptoparasitism and direct killing are very important forms of interference competition among and within carnivore species . Evidence for exploitation competition i s scant, but is inferred because local environments are unpredictable f or carnivores. Analysis of body sizes fails to support the hypothesized ratios of 2.0 for body weigh t and 1.28 for linear dimensions . Three methods of calculating multidimensional niche metrics (product, summation, and projection) are compared. Apparently the Serengeti's carnivores coexist because of their behavioral flexibility in an unpredictable environment . Niche descriptions were of little he l p in assessing the foci for potential and real competition among carnivores . Only the direct observations of interference competition in long-term field studies identified where competitive interactions are occurring with sufficient intensity to provide a numerical response in a population. Spotted hyenas some times competitively exclude African wild dogs locally . Management f or a high abundance and diversity of carnivores probably requires maintaining high densities of prey and varied habitats. Specific recommendations are made for cheetah and African wild dog conservation.

>Magister Scientiae - MSc / Groundwater dependent vegetation (GDV) communities are increasingly threatened by the transformation of the natural environment to different land use/land cover, over-exploitation of groundwater resources and the proliferation of invasive species within the Cape Floristic Region (CFR). These changes affect the groundwater regime, level, and quality, which supports GDV. Natural resource managers often lack an understanding at appropriate scales of the nature of dependency of GDV to make informed sustainable decisions. This work thus assesses the spatial distribution of GDV and their responses to groundwater variability within the Cape floristic region from June 2017 to July 2018. To achieve this aim, firstly a literature review on the background of GDV, threats and the impact of climate change was assessed.

Philosophiae Doctor - PhD / Maintenance of water resources protection practice for water availability, uninterrupted water utilization, and for ecosystem integrity is critical for sustainable achievement of resource security for all. Therefore, operationalization of water resource protection strategies such as resource directed measures, especially at catchment level where water resources utilization takes place is critical. The main aim of the current study was to develop a citizen science framework for operationalization of resource directed measures at catchment level. Such a framework used a nexus approach, and its development was guided by the principles of socio-ecological model from a systems thinking perspective. This demonstrated importance of resource directed measures which are accepted as relevant policy implementation strategies towards improved and integrated water resources management practice at catchment level, where local citizens become part of such practice. Local operationalization of resource directed measures provides a basis for practical policy implementation at catchment level, thereby informing decisions taken on water resources protection and sustainable water use for several purposes. It provides an understanding of how policies which are formulated for water resources protection purposes influence land use activities and other non-land use activities to ensure water availability for current and future generations. Furthermore, localized operationalization of resource directed measures facilitates ecological ecosystems protection such that goods and services derived from such ecosystems are sustained. The research problem of the current study was a lack of available and feasible plan for resource directed measures practice at catchment level which has a direct influence on the continued water quality deterioration and unsustainable utilization of water resources. This study argued that a citizen science framework needed to be developed and such a plan must be informed by science-policy interface that is practical, reflective and must consider the nexus approach using the concept of citizen science in order to improve the practice of resource directed measures at local level in an acceptable manner by practitioners.

Platforms are the critical players driving the digital economy. My thesis focuses on the platform economy, especially the competitive advantage of platforms. On the one hand, what factors affect the competitive advantage of platforms? How does the platform form the competitive advantage? These questions are related to platform strategy. On the other hand, does the competitive advantage of platforms harm social welfare? This question is related to regulatory issues. The first chapter of my dissertation studies how different aspects of user effects drive value in two-sided markets. We first develop a model of inter-temporal network effects and within-period network effects of users to estimate different aspects of user effects. We then propose a model to estimate the user lifetime value in two-sided markets and examine the effectiveness of the user growth strategy. Finally, we discuss platform heterogeneity and corresponding platform strategies. Using Groupon data, we empirically estimate different aspects of user effects and examine how they vary. We show that the strength of the inter-temporal same-side network effect affects user stickiness, further influencing the persistence of the within-period cross-side network effect. Strong within-period cross-side network effects alone cannot sustain value creation. Our findings remind managers not to overemphasize user growth when the inter-temporal network effects are weak and should instead focus on platform design that increases user stickiness. The second chapter of my dissertation examines the impact of a potential policy of opening a platform's big data to banks on FinTech lending. We show that the policy promotes competition in FinTech lending and the loan price decreases. However, its impact on financial inclusion is unclear. We discuss how the efficiency of the banking system and the value of big data affect the policy outcome. We also consider the equilibrium of a data market where the platform can sell big data to banks. We show that FinTech can best promote financial inclusion in this case, but the loan price is the same as when the platform monopolizes big data. Since financial inclusion is important for entrepreneurship and innovation, the regulator should carefully examine the context in their countries before making a policy choice. The third chapter of my dissertation studies the impact of cross-market acquisitions of giant platforms on start-ups' entry into emerging markets. Our model shows that the acquisition reduces the post-acquisition entry but may increase the pre-acquisition entry. The net effect of the acquisition on the entry is positive when the pre-acquisition gain is greater than the post-acquisition loss. We then discuss three cases in which a giant platform strategically increases its market position in the acquisition. The net effect of the acquisition on start-ups' entry varies in different cases. Our findings indicate that regulators should analyze the specific situation of each acquisition before making a decision to approve an acquisition.

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