Most urban areas of developing countries were hitherto experiencing unprecedented growth in their population, the phenomenon commonly referred to as urbanization, which in this study can be said to be the proportion of urban population relative to the total population of a region. This phenomenon has opportunities vis-à-vis challenges, whose impact on natural resources in general and water resources in particular, cannot be over- emphasized. It is within the context of these urban challenges that this study attempts to look into and possibly assess the situation in the urban and peri- urban areas of Kumasi Metropolitan Area (KMA) in Ghana, whose urbanization processes is prejudiced by this study to be increasing rapidly. The study specifically attempted to assess thechanges in the urbanization patterns and the possible future urbanization trend of the area within a specific time frame. The study also attempts to look at the causes of this urbanization, and its impact on water resources in the Area, both qualitatively and quantitatively, envisaged to be the results of socio-economic activities taking place in the Area. Finally, the study attempts to look into the measures put in place to curb these challenges. Amid paucity of data, however, the study reveals that the most single contributor of urbanization processes in the area has been migration from the countryside, and in particular from the northern part of the country. The study also reveals the fact that even though the general quality standard of some water resources is better, the largely uncontrolled socio-economic activities, coupled with the deplorable sanitary conditions in the KMA, has potential to degrade the water resources in the KMA. In addition, the study reveals that little attention is given, in terms of policy formulation to curb this urbanization processes and to protect water resources in the area.

An understanding of the impacts on freshwater systems from water management and development practices and the recognition that freshwater ecosystems are dependent on various aspects of the natural hydrological variability has given rise to a relatively new field of science commonly referred to as environmental flows. The assessment and application of environmental flows has advanced considerably in the last ten years. To coincide with the emergence and expansion of the environmental flows concept around the world, this survey study was undertaken aiming to identify people’s perceptions and interpretations of the environmental flows concept and its role in water management. It also aims to add to existing knowledge of the extent to which the concept is being applied, how it is being translated into policy and practice and the major challenges and opportunities that exist for continued understanding and implementation. The survey was distributed to a range of people representing different water-related sectors and regions around the world. A total of 272 responses representing 64 countries in the six major regions of the world was received. The responses were compiled and analysis of aspects of the respondents backgrounds as well as the questions were conducted using the computer statistical program SPSS. Representation of specific groups, particularly water user groups, and specific regions in the survey however was low, demonstrating possible limitations of the survey distribution method as well as the lack of concept awareness and application in many parts of the world. The ways in which people define and interpret the concept varied widely. The degree to which the concept was applied shows the growing recognition around the world of the need to consider the environmental water requirements when making decisions on water allocations. Despite the growing recognition many areas do not yet apply the concept. The survey allowed the opportunity for respondents to highlight what they perceived asthe major obstacles and difficulties for the concept within their respective areas. Lack of understanding among stakeholders of the socio-economic costs and benefits associated with concept implementation and a lack of political will were the two most common obstacles for the continued adoption and application of environmental flows around the world. Overall, the survey delivered promising signs for the continued evolution of environmental flows within water management. There was widespread opinion that the concept of environmental flows was an essential element in the efforts to achieve sustainable management of water resources.

The condition of the herring (Clupea harengus) in the Baltic Sea has decreased during the past 30-40 years. This decrease could be explained by different factors; (1) change in diet due to changes in zooplankton community, (2) changes in water temperature and salinity, (3) increasing nutrient inputs and (4) competition for food with other species such as sprat (Sprattus sprattus). In this study the change in condition was analysed using the Fulton’s condition index, and by looking at age and sex of the fish as well as the season and locationthe fish was caught, the differences between these factors were presented. Data from the national Swedish contaminant monitoring programme where used from four locations in the Baltic Sea and two locations at the Swedish West coast. The data was analysed using multiple regressions in R Commander. The result show that the condition, and the temporal trends in condition value, varies at different locations, with higher condition values and increasing temporal trends at the Swedish West coast, compared to the Baltic Sea with lower condition values and where three of four locations show decreasing temporal trends. The condition varied between spring and autumn caught herring as well, while age and sex showed less significant differences.

Regions containing gradients of vertical flow are often associated with sharp changes in hydrographic and biochemical water properties in coastal marine ecosystems. Often these are sites of dense plankton aggregations of critical ecological importance. In this study, a recirculating flume apparatus with a laminar, planar free jet (the Bickley jet) was used to create finescale gradients of fluid velocity (shear) in both upwelling and downwelling configurations for zooplankton behavioral assays. Particle image velocimetry (PIV) was used to fully resolve the velocity fields allowing us to fine-tune experimental parameters to match fluid mechanical conditions commonly measured in the field. Zooplankton behavioral assays with two tropical calanoid copepods, Acartia negligens and Clausocalanus furcatus, an estuarine mysid, Neomysis americana, and the larvae of an estuarine mud crab, Panopeus herbstii, were conducted in control (stagnant), upwelling, and downwelling flow configurations. Statistical analyses (ANOVA) of individual zooplankton trajectories revealed the potential for individual behavioral responses to persistent finescale vertical shear layers to produce population scale aggregations, which is proposed here as a mechanism of patchiness in coastal marine ecosystems. Results from behavioral analyses reveal species-specific threshold shear strain rates that trigger individual behavioral responses. Furthermore, results show statistically significant changes in behavior (relative swimming speed, turn frequency, heading) for all species tested in response to a coherent shear structure in the form of finescale upwelling and downwelling jets. The results show that changes in individual behavior can increase Proportional Residence Time (PRT = percent time spent in the jet structure). On a population scale, the increase in PRT can lead to dense aggregations around persistent flow features, which is consistent with numerous field studies. These dense, patchy aggregations of zooplankton have profound trickle-up ecological consequences in coastal marine ecosystems.

Some of the major problems we face today are human induced changes to the nitrogen (N), phosphorus (P) and carbon (C) cycles. Predicted increases in rainfall and temperature due to climate change, may also increase dissolved organic matter (DOM) inflows to freshwater ecosystems in the boreal zone. N, P, C and light, are essential resources that most often limit phytoplankton (PPr) and bacterial production (BP) in the pelagic zone of lakes. PPr and BP not only constitute the total basal C resource for the pelagic aquatic food web, but also influence ecosystem function and biogeochemical cycles. In this thesis I studied how N, P, C and light affect the relative and absolute rates of PPr and BP, along a wide latitudinal and trophic gradient using published data, and in two in situ mesocosm experiments in a clear water oligotrophic lake. In the experiments I manipulated bottom-up drivers of production and top-down predation to examine how these factors interact to affect pelagic food web structure and function. The most important predictors of PPr globally (Paper I) were latitude, TN, and lake shape. Latitude alone explained the most variation in areal (50%) and volumetric (40%) PPr. In terms of nutrients PPr was primarily N-limited and BP was P-limited. Therefore bacteria and phytoplankton were not directly competing for nutrients. BP:PPr was mostly driven by PPr, therefore light, N, temperature and other factors affecting PPr controlled this ratio. PPr was positively correlated with temperature, but not BP, consequently, higher temperatures may reduce BP:PPr and hence the amount of energy mobilised through the microbial food web on a global scale. In papers II and III interaction effects were found between C-additions and top-down predation by young-of-the-year (YOY) perch. Selective predation by fish on copepods influenced the fate of labile C-addition, as rotifer biomass increased with C-addition, but only when fish were absent. Interaction effects between these top-down and bottom-up drivers were evident in middle of the food web, which is seldom examined in this type of study. Although the energy pathway from bacteria to higher consumers is generally longer than from phytoplankton to higher trophic levels, increased BP still stimulated the biomass of rotifers, calanoid copepods and YOY fish. However, this appeared to be mediated by intermediate bacterial grazers such as flagellates and ciliates. Light was an important driver of crustacean zooplankton biomass (paper IV), but the light:nutrient hypothesis was inadequate to predict the mechanisms behind the decrease in zooplankton biomass at low light. Instead, it appeared that reduced edibility of the phytoplankton community under low light conditions and reduced BP most strongly affected zooplankton biomass. Thus, the LNH may not apply in oligotrophic lakes where PPr is primarily N-limited, Daphnia is rare or absent and mixotrophic phytoplankton are abundant. N, P, C and light manipulations have very different effects on different parts of the pelagic food web. They influence the relative rates of PPr and BP, affect phytoplankton community composition, alter the biomass of higher trophic levels and change pathways of energy transfer through the pelagic food web. This thesis adds valuable information as to how major changes in these resources will affect food web structure and function under different environmental conditions and future climate scenarios. / Lake ecosystem response to environmental change

The minimum ecologically viable population size (MEVP) of a species describes the minimum size at which the species itself or another species in the same ecosystem goes extinct as a result of the loss of inter-specific interactions. The MEVP shows a good potential for use as a tool for exploring the mechanisms behind species extinctions, but presently only a small amount of research has been done that takes advantage of this. In this study the MEVP is used to investigate what properties of species can be used as good indicators of ecological importance. 100 large computer generated food webs were created with an assembly model and the reduction in density that was necessary to induce an extinction event in the web was subsequently determined for each species within the webs. This change in density was then correlated with 28 different properties, measured for each species. The results show that properties that measure how well connected a species is, as well as measures of the species role as a prey item in the web are the ones with the greatest potential to find species with high MEVP. Further, the results put emphasis on the importance of regarding the web as a whole when working with species extinctions, while also highlighting the usefulness of the MEVP concept.

Ecosystem modelling allows for an understanding of the structure and functioning of ecosystems. During this study, the oligotrophic KwaZulu-Natal (KZN) Bight, a data-limited system on the east coast of South Africa, was modelled. A framework for modelling data-poor systems, incorporating the construction of multiple models, sensitivity analyses and comparative analyses was applied to the Bight using literature data. Models converged on general trends of ecosystem functioning showing 99% of flows originated from detritus, primarily imported from rivers. The largest source of riverine detritus is the Thukela River which flows into the central Bight. This area supports a shallow-water prawn trawl fishery which targets penaeid prawns. Fisheries time series‘ were incorporated into the model framework to study the effects of prawn trawling and the decrease in prawn recruitment, caused by estuarine nursery loss, on the central Bight ecosystem. Dynamic simulations suggest the biomass of biotic groups were more affected by prawn recruitment level than trawling effort level. To understand the importance of nutrients in more detail, nutrient content, biomass and stoichiometric ratios were documented for various pelagic and demersal functional groups, and compared between areas in this oligotrophic system. Results showed the central Bight had the highest carbon, nitrogen and phosphorus biomasses, due to riverine nutrient sources, and the southern Bight had the lowest. In addition, the demersal community had higher biomasses than the pelagic community for all nutrients. Nutrient dynamics and limitations within the Bight were explored through the construction and analysis of trophic flow networks of carbon, nitrogen and phosphorus for the southern, central and northern Bight. Network analyses suggest nutrient cycling was lowest in the central Bight, and highest in the southern Bight. Cycling of nitrogen was highest in all areas due to the dominance of benthos, in terms of biomass, which was nitrogen-limited. Higher trophic levels were found to be phosphorus-limited. However many pelagic groups were co-limited by nitrogen and phosphorus, probably due to the oligotrophic nature of the bight. This suite of ecosystem models provides the first holistic view of the KZN Bight and an understanding of ecosystem functioning in the southern, central and northern Bight. / Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2012.

The KwaZulu‒Natal Bight is formed from a narrow indentation in the SE coast of South Africa with the waters within considered to be oligotrophic. These waters therefore depend on both allochthonous sources of nutrients such as intermittent upwelling of deeper water and nutrients supplied by riverine inputs, as well as the autochthonous nutrients supplied by phytoplankton production, microbial fixation and recycling of nutrients by the microbial loop. Two African Coelacanth Ecosystem Programme cruises were undertaken during 2010, during the wet summer, and dry winter months. During each cruise, the waters of the KZN‒B were sampled rapidly to provide spatial scales (synoptic) of bacterial abundance and biomass, as well as at four predetermined locations to determine temporal scales (focus) of bacterial abundance, biomass and productivity. During the synoptic section, samples were taken in surface waters, close to F‒max (the depth at which phytoplankton were at their most dense as determined by in situ fluorometry), below the F‒max (where depths exceeded 50 m), and near the bottom. These samples were fixed with formaldehyde, stained with DAPI and cells were visualised by epifluorescent microscopy. During the focus section, samples were taken in surface waters, close to F‒max and below F‒max and incubated with 3H‒Thymidine to determine bacterial productivity. Bacterioplankton dynamics (numbers, biomass and productivity) for both cruises, synoptic section, were higher within the photic zone and near riverine influenced waters, with summer showing higher dynamics than winter. Irrespective of season, bacterioplankton dynamics decreased with increasing distance from the coast as well as with increasing depth, potentially via bottom‒up control mechanisms. Results obtained from the focus section of both cruises showed a significant difference between seasons for the Thukela Mouth and Richards Bay North, while no difference at the Durban Eddy. These results from the focus section suggest that bacterioplankton temporal dynamics were more top‒down controlled, rather than environmentally influenced, resulting in fluctuating dynamics over time. Overall, it is proposed that the degree of inorganic nutrient supply to the phytoplankton, resulted in the formation of DOM for use by the heterotrophic bacteria, resulting in a bottom‒up control mechanism, where Chl‒a concentrations within the euphotic zone induces either top‒down or bottom‒up control mechanisms on the heterotrophic bacteria directly affecting their numbers, biomass and productivity. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2013.

Coral reefs are highly complex and also highly threatened ecosystems. Population growth and the unsustainable use of coral reefs have resulted in 55% of the world’s reefs being considered degraded. Fishing, the primary ‘local’ threat on most reefs, has altered the composition of most reef communities. As a result, very few pristine coral reefs remain. Typically, coral reef research is done via underwater visual censuses, providing abundance estimates but no indication of trophic interactions, therefore we know relatively little about the structure of intact reef food webs. Understanding how human activities affect trophic structure and feeding interactions among resident reef species may be important for coral reef conservation. Here, I apply stable isotope analysis to coral reef piscivorous fishes from Kiritimati (Republic of Kiribati), the world’s largest atoll. I examine dietary niche metrics of five focal species (Cephalopholis argus, Cephalopholis urodeta, Aphareus furca, Lutjanus bohar, and Lutjanus fulvus) and of the piscivore functional group as a whole, across an anthropogenic disturbance gradient that results from the atoll’s heavily skewed geographic population distribution. Using bootstrapped stable carbon (δ13C) and nitrogen (δ15N) isotope values, controlled for body size effects and analysed with Bayesian methods using the SIAR (Stable Isotope Analysis in R) program, I provide evidence of isotopic niche differentiation in C. argus and L. fulvus relative to other sampled species in terms of niche width metrics and mean δ13C and δ15N values. I also analyse the effect of fishing pressure at an individual level (controlling for body size effects on stable isotope signatures for each species), population level (accounting for observed differences in body size distributions across the fishing pressure gradient for each species), and the ‘community’ level (accounting for body size and relative abundance differences of the five piscivores across the fishing pressure gradient). These metrics reveal species-specific changes in niche metrics of three of the focal species at the individual level: C. urodeta, showed regionally distinct niche width metrics but no apparent correlation with fishing pressure, while A. furca and L. bohar, both had broader niche width metrics in heavily fished areas. No significant effect of fishing pressure was found at population or community levels. This study provides the first evidence using stable isotopes that fishing can alter the diets of coral reef fishes. The mechanism by which it can do so, while not entirely clear, would most likely be by expanding a given species’ dietary diversity by either forcing it to switch to non-preferred prey items or changing the diet and/or body size of its prey items, both of which would reflect significant ecological changes within a community. This thesis provides evidence of the utility of stable isotope analyses in answering important ecological questions in coral reef food webs, and reveals that fishing can affect reef communities at the most fundamental level of trophic interactions. / Graduate / 0329 / burrilladrian@gmail.com

Female reproductive decisions have been suggested to be highly influenced by mate quality. I have studied whether offspring quality may be adjusted by females to match the attractiveness of males and how strong control females have over their reproductive investment focusing on egg size. This was done in the Banggai cardinalfish (Pterapogon kauderni), a sex-role reversed obligate paternal mouthbrooder where males invest heavily into reproduction. As this species is suitable for both laboratory experiments and field studies it is an ideal candidate for the study of reproductive investment. Mating was size-assortative and both males and females benefited from pairing with large partners. However, male size determined the reproductive output of a pair. Females courted large males more intensively and produced larger, but not fewer eggs when mated to large males as compared to small males. Further, this matching of egg size to mate attractiveness may be fast. Female courtship behaviours contained honest information regarding both clutch weight and egg maturity, traits that may be highly important for male mate choice. Surprisingly, males played an important part in territory defence suggesting relatively equal sex-roles in this species. Also, this species showed stable group structures which may be important for the evolution of female plasticity in reproductive investment due to high variance in quality of available mates. This thesis suggest that females have a remarkable control over their reproductive investments and that male quality may be highly influential on reproductive decisions regarding offspring quality. Furthermore, it suggest that sexual selection may have strong effects on the evolution of egg size and parental care on a whole.