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1
Phephu, Nonkululo. "A taxonomic revision of Thuidiaceae (Bryophyta) in Africa and the East African islands." Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/41007.
Full textAbstract:
A taxonomic revision of the family Thuidiaceae Schimp. for Africa and the east African Islands is
presented. Three genera, namely, Pelekium Mitt., Thuidiopsis (Broth.) M. Fleisch. and Thuidium
Bruch & Schimp., and 16 species are accepted and revised for the region. The nomenclature, keys
to genera and species, descriptions, illustrations and distribution maps are included.
Thuidiaceae is one of over 40 families that belong to the Hypnales which is known to
contain the most diversity among pleurocarpous mosses. Members of the Thuidiaceae are
characterised by gametophytes with attractive, regularly 2- or 3-pinnate branching, presence of
paraphyllia on surfaces of stems and branches, dimorphic stem and branch leaves, longitudinally
plicate leaves with a single costa, papillose leaf cells, and a hypnoid peristome. Abietinella Müll. Hal., Haplocladium (Müll. Hal.) Müll. Hal., Hylocomiopsis Cardot and
Rauiella Reimers are excluded from African Thuidiaceae. Thuidium involvens var. thomeanum
Broth. is raised to species status under Pelekium, as Pelekium thomeanum (Broth.) Phephu.
Thuidium pseudoinvolvens (Müll. Hal.) A. Jaeger is also transferred to Pelekium and the new
combination Pelekium pseudoinvolvens (Müll. Hal.) Phephu is proposed.<br>Dissertation (MSc)--University of Pretoria, 2013.<br>gm2014<br>Plant Science<br>unrestricted
2
Mwachala, Geoffrey. "Systematics and ecology of Dracaena L. (Ruscaceae) in Central, East and Southern Africa." [S.l.] : [s.n.], 2005. http://kola.opus.hbz-nrw.de/volltexte/2005/21.
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Amir, Omar A. "Biology, ecology and anthropogenic threats of Indo-Pacific bottlenose dolphins in east Africa." Doctoral thesis, Stockholm : Department of zoology, Stockholm university, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-34472.
Full textAbstract:
Diss. (sammanfattning) Stockholm : Stockholms universitet, 2010.<br>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 4: In progress. Paper 5: Submitted.
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Burns, Michael Edmund Reid. "A synecological study of the East London coast dune forests." Thesis, Rhodes University, 1987. http://hdl.handle.net/10962/d1006134.
Full textAbstract:
Quantitative community descriptions, based on point quarter sample data, are made for a number of dune forest units along the East London coast. These are supported by multivariate classifications and ordinations which illustrate the inter community variation between the sampled seaward, landward and dune valley sites. Climax valley forest is floristically most characteristic and can be clearly distinguished from the seaward and landward thicket communities which tend to show a degree of similarity. Within-forest community differences are shown to be more significant than variation along the coast. This appears to indicate that climoedaphic gradients established laterally to the coast induce a greater floristic response than the rainfall gradient within the study area. The state of developnent within the dune soil profile and the rate and effect of salt spray deposition are considered to be important factors influencing dune forest succession and are discussed in some detail. An overview of certain other climatic variables as well as the geological features within the study area is also given. A phenology study of the dune forest, scrub-thicket and strand plant cornnunities shows some general patterns of flowering and fruiting phenorhythms. Although much variation was observed, there appears to be a bimodal hyperactive phenophase response which is thought to be related to rainfall or periods of favourable soil moisture conditions. A brief discussion of some of the positive and negative human influences on the coastline is given. This includes a description of the management activities carried out in the area as well as the demands placed on ·the coastal resource.
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Van, der Westhuizen Henri. "Valuing preferences for freshwater inflows into the Bira, Bushmans, Kasouga, Keiskamma, Kleinemond East, Nahoon and Tyolomnqa estuaries." Thesis, Nelson Mandela Metropolitan University, 2007. http://hdl.handle.net/10948/628.
Full textAbstract:
There are about 259 estuaries in South Africa that can be classified as “functioning” and their “health” status is directly related to the quantity and quality of freshwater that flows into them. Many of South Africa’s estuaries have become smaller due to a steady decrease in the amount of freshwater that flows into them. This reduction in freshwater inflows decreases their ecological functioning and undermines the recreational activities and subsistence services available from them. The National Water Act (ACT No. 36 of 1998) recognises the right of the environment to water, but a large amount of data is still needed to make management decisions on the allocation of freshwater. The objective of this research was to contribute to the management of the allocation of freshwater in the catchment areas of the Bira, Bushmans, Kasouga, Keiskamma, Kleinemond East, Nahoon and Tyolomnqa rivers by determining the recreational value of the freshwater flowing into their estuaries. This recreational value was established using the contingent valuation method. The contingent valuation method (CVM) is a technique to establish the value of a good (or service) that is not bought or sold in an actual market. This technique is frequently applied in the valuation of environmental goods, e.g. the freshwater that flows into an estuary. The CVM establishes the economic value by asking the users of an environmental good to state their willingness to pay (WTP) for a hypothetical project to prevent or bring about a change in the current condition of the environmental good. The users’ WTP is then aggregated to establish a total willingness to pay (TWTP) for the population of the users of the environmental good. The hypothetical project presented in this study is that of an increase of freshwater inflows, that would prevent (bring about) predetermined changes in environmental services provided by the selected seven estuaries.
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O'Reilly, Catherine Marie. "The effects of land use change on littoral zone dynamics of Lake Tanganyika, East Africa." Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/289754.
Full textAbstract:
Lake Tanganyika, East Africa, is one of the world's unique freshwater ecosystems. This lake is approximately 10 million years old and contains an extremely diverse fauna with high levels of endemicity. Most of the biodiversity in the lake is concentrated along the rocky shoreline, and this dissertation focused on the land-water interactions that may affect the littoral ecosystem as human population densities increase. First, the potential of carbon and nitrogen stable isotopes as indicators of human impact was examined. Sedimentary organic matter from four river deltas with contrasting patterns of land use was used to develop a predictive relationship between terrestrial patterns and geochemical signals. Stable isotope analyses of cores taken at two disturbed and two undisturbed watersheds were consistent with patterns seen in surface sediments. These results suggest that nitrogen isotopes are a better indicator of land use while carbon isotopes are useful in determining changes in vegetation patterns. To evaluate the effect of deforestation on ecosystem dynamics, epilithic metabolism was measured at several sites over a period of one year. Epilithic net productivity did not differ significantly between the disturbed and undisturbed watersheds, but epilithic respiration and algal biomass were significantly higher at the disturbed site. Further evidence of disturbance was given by greater amounts of inorganic material on the rocks and lower ambient oxygen concentrations at the impacted site. Finally, in order to identify species more susceptible to changes in benthic productivity, the food web structure of the pelagic and littoral food webs was elucidated using stable isotopic analyses. Diet specificity is not apparent in the littoral food web, suggesting that broad dietary preferences may help stabilize this persistent food web during environmental perturbations. The isotopic structure of the pelagic food web suggests that upwelling of deeper waters is an important nutrient source for the food web, which is consistent with current nutrient and hydrodynamic models.
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Jambo, Collins Mayeso. "Aspects of the ecology and reproductive biology of three cichlid fish species of Southern Lake Malombe (Malawi)." Thesis, Rhodes University, 1998. http://hdl.handle.net/10962/d1005067.
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The three major species Lethrinops ''pinkhead'', Otopharynx argyrosoma "red" and Copadichromis. cf virginalis which used to dominate the catches (by weight) of Lake Malombe in the past decade were investigated. In order to make rational recommendations regarding size and boundary of the existing sanctuary area (lightly fished), distribution and abundance, population structure and reproductive biology of the three species were related to habitat types of the southern part of the lake (south western side and south eastern side). Analysis of catch composition showed that species richness was higher in the south eastern side than in the south western side of the lake. Rare species such as Labeo mesops and Opsaridium microiepis were observed in the south eastern side and there was visual absence of such species in the south western side of the lake. The overall fish abundance was significantly greater in the south eastern side than in the south western side of the lake. In the south eastern side, the catch per unit effort (CPUE) was twice that of the south western side (P< 0.05). Seasonal fluctuations in CPUE were also prominent, with the highest peak occurring during September-October period. However, there was an indication of weak relationship among CPUE, phytoplankton biomass, temperature and water depth. The length-weight relationships revealed that growth of the three species closely followed the cubic law for isometric growth in both sides of the lake. Differences in regression coefficients between sides were not significant (ttest, P>0.05). The length-frequency distribution analysis revealed that the three species had the same growth rate regardless of habitat type. However, females grew faster than males. An investigation of reproductive biology showed that the three species have low fecundity and they are asynchronous spawners, with a breeding peak during August and September period. Furthermore, the length-fecundity relationships for L. ''pinkhead'', and 0. argyrosoma "red" indicated that fecundity was more closely related to length in the south eastern side than in the south western side. Based on the above characteristics of L. ''pinkhead'', 0. argyrosoma "red" and C. cf virginalis, and the substrate types, it was strongly suggested that the existing sanctuary (lightly fished) in the south eastern side of the lake could immediately be enlarged to conserve the fish stocks, favourable substratum and aquatic animals that may be of tourists concern.
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Vromans, Deborah Claire. "Macrophyte phenology in a temporarily open/closed Estuary compared with a permanently open Estuary." Thesis, Nelson Mandela Metropolitan University, 2010. http://hdl.handle.net/10948/1393.
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Temporarily open/closed estuaries (TOCEs) are unpredictable environments that change in response to mouth condition, which is influenced by freshwater flooding or sea storm surges. The aim of the study was to determine whether macrophyte phenology in a TOCE was event driven rather than cyclically predictable and if it differed from permanently open estuaries (POEs). Macrophyte growth and flowering phenology in response to environmental conditions was investigated in the East Kleinemonde Estuary (TOCE) and the Kowie Estuary (POE) along the eastern coastline of South Africa. The lack of freshwater flooding due to low rainfall coupled with several overwash events resulted in a prolonged period of mouth closure from September 2008 to the end of this study period in 2010. This in turn caused the inundation of the supratidal and intertidal habitats, high water level (> 1.57 m amsl) and high salinity (30 - 42 ppt) in the TOCE. Principle Components Analysis showed that high water level and reduced sediments were the most significant environmental factors affecting macrophyte phenology. Macrophyte phenology in the POE was primarily driven by temperature, sediment redox potential and salinity. The saline high water level and reduced sediment significantly reduced macrophyte cover in all habitats in the TOCE. Macrophytes in the POE maintained high cover abundance due to seasonal re-growth compared to the TOCE where cover declined over the sampling period due to the high water level. Subsequent to water level dropping by as little as 11 - 20 cm in the TOCE, the intertidal species Sarcocornia tegetaria and Salicornia meyeriana completed their life-cycles and produced viable seeds within four and three months of germinating respectively. In contrast, the Sarcocornia hybrid and S. meyeriana in the POE took longer to complete their life-cycles, namely seven and nine months respectively, while S. tegataria did not germinate in situ but reproduced vegetatively despite producing seed. In the TOCE, the submerged species Ruppia cirrhosa and Chara vulgaris completed their life-cycles within five and three months and produced a maximum of 26 242 and 196 998 seeds m-2 respectively. Due to high water level and prolonged inundation, the reproductive periods were shorter for the intertidal and reed and sedge species in the TOCE compared to the POE. Seed output during the two reproduction periods varied between the two estuaries. Sarcocornia decumbens and S. tegetaria produced a substantially higher number of seeds in the TOCE compared to the POE, namely 0 - 102 847 versus 20 661 - 48 576 seeds m-²; and 7 001 - 45 542 versus 1 587 – 16 958 seeds m-² respectively. Seed output in the TOCE was significantly higher in S. tegetaria during the second reproduction period despite the significantly lower plant cover, which may be a function of the stressful environment in the TOCE. Seed production of S. meyeriana was significantly higher in the POE compared to the TOCE, with 264 224 - 640 292 compared with 24 050 - 27 643 seeds m-², due to higher plant cover in the POE. The research suggests that macrophyte phenology in the TOCE was significantly influenced by mouth condition. Further, macrophytes were able to demonstrate considerable phenotypic plasticity in response to changing and unfavourable environmental conditions. These data can be used in mouth management plans and freshwater requirement studies in TOCEs to ensure that macrophytes can complete their life-cycles and produce viable seeds for the safeguarding of habitat persistence and ecological processes. In impacted estuaries where artificial mouth opening is practised and the macrophytes have been severely degraded or extirpated, management should ensure that the intertidal and supratidal habitats are not inundated during peak flowering and seed production periods i.e. late spring to early autumn (November to March).
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Allan, Elizabeth Louise. "Ecological role of free-living bacteria in the microbial food web of the temporarily open/closed East Kleinemonde Estuary, South Africa." Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1005351.
Full textAbstract:
The main aim of this study was to assess the “top-down” and “bottom-up” control of bacterial production in the small temporarily open/closed East Kleinemonde Estuary, situated on the south-eastern coastline of southern Africa. Spatial and temporal patterns in bacterial abundance, biomass and production and the importance of abiotic and biotic factors were investigated over the period May 2006 to April 2007. The trophic interactions between bacteria, phytoplankton, nanoflagellates (< 20 μm), microzooplankton (< 200 μm) and mesozooplankton (< 2 000 μm) were investigated during winter and summer. Bacterial abundance, biomass and production ranged between 1.00 × 10⁹ and 4.93 × 10⁹ cells 1⁻¹, 32.4 and 109 μg C 1⁻¹ and 0.01 and 1.99 μg C 1⁻¹ h⁻¹, respectively. With a few exceptions there were no spatial patterns in the values. Bacterial abundance, biomass and production, however, demonstrated a distinct temporal pattern with the lowest values consistently recorded during the winter months. Nanoflagellate and bacterial abundances were significantly correlated to one another (lower reaches: r = 0.818, p < 0.001; middle reaches: r = 0.628, p < 0.001; upper reaches: r = 0.484, p < 0.05) suggesting a strong predator-prey relationship. The frequency of visibly infected bacterial cells and the mean number of virus particles within each bacterial cell during this study demonstrated no temporal or spatial patterns and ranged from 0.5 to 6.1 % and 12.0 to 37.5 virus particles per bacterium, respectively. Viral infection and lysis was thus a constant source of bacterial mortality throughout the year. The estimated percentage of bacterial production removed by viral lysis ranged between 7.8 and 88.9% of the total which suggests that viral lysis represented a very important source of bacterial mortality during this study. The biological interactions between the selected components of the plankton community demonstrated that among the heterotrophic components of the plankton, the nanoflagellates were identified as the most important consumers of bacteria and small phytoplankton cells (< 20 μm). In the presence of microzooplankton the impact of the nanoflagellates on both the bacteria and phytoplankton was reduced, indicating that larger heterotrophs were preying upon the nanoflagellates. Mesozooplankton, however, appeared to exert the greatest impact on nanoflagellates. In the cascading experiments, the data suggest that mesozooplankton consume nanoflagellates, which resulted in a decrease in the predation impact of these organisms on the bacteria. This result is consistent with predator-prey cascades. The presence of the larger heterotrophs therefore, mediates the interactions between the primary bacterivores, the nanoflagellates, and the bacteria within the temporarily open/closed East Kleinemonde Estuary.
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Muli, Benjamin Kimwele. "The biology and ecology of Mussidia spp. (Lepidoptera : Pyralidae) and associated natural enemies in Kenya / Benjamin Kimwele Muli." Thesis, North-West University, 2009. http://hdl.handle.net/10394/4114.
Full textAbstract:
Mussidia nigrivenella Ragonot (Lepidoptera: Pyralidae), an important pest of maize, cotton and Phaseolus bean in West Africa, has never been described as a crop pest from East and southern Africa (ESA). It was hypothesized that in ESA it was either kept under control by natural enemies or that there exist several populations of M. nigrivenella with different host plant ranges. Another possibility is the mis-identification of the Mussidia species in ESA. Studies were conducted in Kenya between 2005 and 2007 to assess the species diversity and host plant range of Mussidia spp. and spatial distribution studies were done on selected host plants. Later, based on the results of host plant range, surveys were conducted between 2006 and 2007 in mid-altitude coastal Kenya to establish a catalogue of parasitoids associated with Mussidia spp. The suitability of stem borers found in Kenya for development of Trichogrammatoidea sp. nr lutea Girault (Hymenoptera: Trichogrammatoidea) and the factors affecting the bionomics of Mussidia sp. in the laboratory were examined. Eight plant species were found to host two Mussidia spp. and six putative morphospecies, which occur sympatrically in the coastal region. The two Mussidia spp. were Mussidia fiorii Ceconni and de Joannis and M. nr nigrivenella. Only one Mussidia sp., M.Jiorii, was found attacking one host plant species in the mid-altitude regions. In general, the host plant range was much narrower than in West Africa. Mussidia nr nigrivenella and Mussidia "madagascariensis" larval distribution was aggregated on Canavalia cathartica Thouars. (Fabaceae) and Strychnos madagascariensis Poir. (Loganiaceae), respectively, while the distribution of M. fiorii adults on Kigelia africana (Lam.) Benth. (Bignoniaceae) was regular. Eight parasitoid species were recovered from Mussidia spp. eggs and larvae and include the trichogrammatid egg parasitoid Trichogrammatoidea sp. nr lutea Girault, a braconid egg-larval parasitoid, Phanerotoma sp., the bethylid Goniozus sp. and the braconid Apanteles sp. Moreover, the ichneumonid larval parasitoid Syzeuctus sp. was obtained from M. fiorii, while the tachinid Leskia sp. was obtained from M, "madagascariensis". Trichogrammatoidea sp. nr lutea, the only parasitoid species which was successfully reared in the laboratory, successfully attacked and developed on eggs of six lepidopteran hosts indicating its potential to exploit other alternate lepidopteran pests of maize in West Africa. Like the parasitoid species, only one Mussidia sp., M.fiorii, was successfully reared in the laboratory and it developed on maize seed-, Canavalia enseiformes L. DC (Fabaceae) seed- and maize leaf-based diets while it could not develop on Mucuna pruriens L. DC (Fabaceae) seed- and C. cathartica seed-based diets. The lower developmental thresholds for M. fiorii eggs, larvae, pupae and egg to adult were found to be 12.8±0.25°C, 14.4±0.27°C, 11.0±0.03°C and 13.5i0.2rc, respectively, while the thermal constants were 82.0±1.61, 384.6±9.43, 144.9±6.84 and 588.2±10.81 degree days, respectively. Adults started emerging during the last hour of photophase and peak emergence was observed in the 2nd hour of scotophase. Mating activity largely took place between the 4th and 5th hour of scotophase. It can be concluded that there exist several Mussidia spp. in Africa that vary in their host plant range. Overall, mortality caused by parasitoids was negligible hence they were unlikely to explain the population dynamics of the Mussidia spp. in Kenya. The fact that Trichogrammatoidea sp. nr lutea successfully attacks and develops in six lepidopteran hosts, including two Mussidia spp. indicates its potential for use as a biological agent against M. nigrivenella in West Africa. Mussidia fiorii was able to develop on diets based on maize and C. enseiformes. The knowledge on dietary and thermal requirements would optimize mass production of the host and natural enemies. The present study revealed again a serious bottleneck for biocontrol worldwide, namely the
proper identification of the pest and natural enemy species as a result of an ever dwindling number of taxonomists. We therefore suggest that molecular (DNA) techniques should be used in addition to detailed morphological examination. In view of the fact that natural control will not be effective in case of accidental introduction of the West African M. nigrivenella into Kenya, we suggest stringent precautions during movement of grains especially maize between the West Africa region and Kenya.<br>Thesis (Ph.D. (Environmental Sciences and Management))--North-West University, Potchefstroom Campus, 2009.
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Fröhlich, Julius. "The impacts of global warming and diet change on the virtual water consumption: Estimating the present and future invisible virtual water resource use in East Africa." Thesis, Stockholms universitet, Stockholm Resilience Centre, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-179153.
Full textAbstract:
The production of food is the biggest water consumer and it is required to meet the growing demand of food from a growing population and changing diets. Water can be dislocated indirectly in its hidden virtual form in traded food products as the water that is needed to produce the product locally. East Africa is a generally water scarce region, often ignored in scientific literature and characterized by a currently fast-growing population and overall economy, resulting in ongoing dietary change of people with growing incomes. The aim of this thesis is to estimate the current amount of water demand as virtual water to produce food for the present and future global change scenarios facing higher temperatures and higher food demand with growing populations. By using the CLIMWAT-model and CROPWAT-database, the virtual water content of all national produced agricultural commodities is summarized as its water footprint and put into relation to the national water availability. The results of the ratio between water footprint and availability show that Somalia’s, Kenya’s and Djibouti‘s food production water demand has exceeded the water availability before 2014. Tanzania and Ethiopia are expected to join these countries between 2014 and 2030. The impact of virtual water trade and global warming balance each other out with 2.23 and 2.45% of change of the water footprint and availability ratio. Meat production consumes twice as much water than crop production with only 5% of the total food weight, making livestock the key driver of virtual water development.
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Mirera, David Oersted. "Capture-based mud crab (Scylla serrata) aquaculture and artisanal fishery in East Africa- Practical and ecological perspectives : Mud crab ecology and aquaculture." Doctoral thesis, Linnéuniversitetet, Institutionen för biologi och miljö (BOM), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-32399.
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Mud crab Scylla serrata is a crustacean that spends most of its life cycle in the mangrove environment throughout its range. Fishery and aquaculture of this crab are significant economic activities in coastal areas in the tropics and sub-tropics because of the meat quality and nutritional value. However there is a significant shortage of information on the ecology, fishery and aquaculture of these crabs in sub-Saharan Africa. This impacts the development of a sustainable aquaculture and fishery for the benefit of coastal communities. The present study analyses various aspects of mud crab ecology, fishery, aquaculture and social economics in East Africa using multidisciplinary approaches. The results are given in seven papers based on field and laboratory studies. The study established for the first time that high intertidal mangrove back-flats constitute a key habitat for the earliest instars of S. serrata (4 -30 mm CW). It also showed that diurnal tidal migration behaviour occurs in small juveniles that migrate to sub-tidal habitats during the day, possibly due to variable predation risks. Monthly sampling of juveniles in Kenya and Tanzania indicated continuous recruitment throughout the year. The large numbers of juvenile crabs along mangrove fringes indicate that these habitats could serve as sites suitable for collection of juvenile crabs for aquaculture. However, these areas must also be managed and protected to support the recruitment to the wild crab populations. An assessment of the crab fishery indicated that artisanal crab fishers possess significant traditional knowledge mainly inherited from their parents that enabled them to exploit the resource. Such knowledge could be useful for the development of the aquaculture and in management of the fishery. Mud crab fishing was found to be a male dominated activity, and fishers on foot practiced fishing in burrows at spring low tides. Interviews indicated that the average size of marketable crabs has declined over the years and a weak management system was observed with most fishers operating without a license. Due to the knowledge required regarding the local conditions, fishers are unable to shift to new areas. Furthermore fishers and could not fish at neap tides. Such limitations provide a “natural closure” of the fishery. Also foot fishers cover fairly limited distances in their daily operations, an aspect that can be utilized to effect site-specific management for the fishery if necessary. Laboratory and field experiments indicated that cannibalistic interactions are heavily influenced both by size differences of crabs and the availability of shelter but no significant effect was found for different stocking densities. Such information is of direct importance for crab farmers in East Africa, where seed from the wild are of multiple sizes and there is a need to grade juvenile crabs and provide shelter at stocking to ensure maximum survival. Experimental studies in earthen pond and mangrove pen cultures indicated high mortality rates. Comparing growth in earthen pond and mangrove pen systems indicated that growth rates were generally high in both systems, but significantly lower in pen systems without shelter, suggesting that shelter may have a stronger effect on growth than has been previously thought. Similar to artisanal mud crab fishery, an assessment of small-scale mud crab farming by organized community groups in Kenya indicated low level of women participation. A good knowledge of the market existed among the mud crab farming groups where hotels and exporters offered the highest prices. However there is a need for national policies to be directed to support small-scale aquaculture development by ensuring training and capacity building for women, operation and management of groups, data management and provision of user rights for communities working in the mangrove environment. Market analyses showed that the common market size of crabs in East Africa ranged between 500-1000 g and are thus larger than in Southeast Asia where the average size is reported at 300 g. Prices for mud crabs were over 50 % lower in Tanzania than in other East African countries and most of the profit was earned by middlemen and exporters. Cost revenue analysis showed that it would be more profitable to farm smaller commercial crabs, and develop a market for 300 g crabs to increase the profitability of crab farming in East Africa. Also, the same analyses found that farming large crabs in individual cages, which is the dominant culture form in East Africa today, had very low profitability due to high labor costs and low growth rates. Using a step-wise function of natural growth it was shown that growth rates of S. serrata cultured in cages was 40 % of the growth rates obtained in experimental pond and pen cultures, which were similar to natural growth. Therefore the good performance of grow-out cultures of juvenile mud crabs in earthen ponds and mangrove pens showed a potential to develop into a profitable and sustainable intervention. However, more work is needed to improve survival in culture systems and address the identified limitations of crab seeds and feed to enable development of sustainable mud crab aquaculture in East Africa.
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Vosloo, Mathys Christiaan. "Network analysis of trophic linkages in two sub-tropical estuaries along the South-East coast of South Africa." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1010966.
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Estuaries are some of the most productive yet threatened ecosystems in the world. Despite their importance they face significant threats through changes to river flow, eutrophication, rapid population growth long the caost and harvesting of natural resources. A number of international studies have been conducted investigating the structure and functioning of an array of ecosystems using ecological network analysis. Energy flow networks have been contsructed for coastal, lagoonal, intertidial and, most notably, permantently open estuaries. Despite the valualble insights contributed by these and other studies, a lack of information on the majority of estuarine ecosystems exists.
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Vorsatz, Lyle Dennis. "Observations on the biology and seasonal variation in feeding of the East Coast redeye round herring (Etrumeus wongratanai) (Clupeiformes), off Scottburgh, KwaZulu-Natal, South Africa." University of the Western Cape, 2016. http://hdl.handle.net/11394/5545.
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Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol)<br>The basic biology and ecology of Etrumeus wongratanai was investigated from samples of fish collected by jigging off Scottburgh, Kwazulu-Natal throughout 2014 and 2015. A total of 516 otoliths, 401 gonads, 140 stomachs and 163 samples of white muscle tissue was examined, and length and weight data of 3 637 fish caught between 2013 and 2016 was also analysed. Counts of annuli deposited on sagittal otoliths indicate that sampled E. wongratanai ranged from 0 to 3 y. (year/s) of age. Length-at-age for males (females) was estimated at 15.5 cm (16.2 cm) for 1 y. olds, 17.7 cm (17.4 cm) for 2 y. olds and 19.6 cm (18.8 cm) for 3 y. olds. The length at 50% maturity was estimated to be 15.6 cm for males, and 16.1 cm for females. Etrumeus wongratanai showed high gonadosomatic index values from June to December indicating that the breeding season lasts for 6 and 8 months for males and females, respectively, and that spawning takes place from the onset of winter to early summer. Condition factor was lowest in May through to August and increased from September. The low condition factor values from May through to
August could be due to the physiological strain before and during the spawning season. Fish larvae were the most important food item in samples collected in summer, whereas eucalanids were the most important prey item in autumn and winter. Overall, large copepods were the dominant prey items in terms of frequency and importance. Stable isotope data suggests that there are gradual changes in the trophic level and diet of E. wongratanai as it increases with size, and whilst δ¹⁵N values differed between seasons δ¹³C did not. The results obtained here are
compared with other species of Etrumeus, regionally and globally.<br>National Research Foundation (NRF) and ACEP Phulisa
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Tilney, Robin Lewis. "Aspects of the biology, ecology and population dynamics of Galeichthys feliceps (Valenciennes) and G. ater (Castelnau) (Pisces: Ariidae) off the south-east coast of South Africa." Thesis, Rhodes University, 1991. http://hdl.handle.net/10962/d1005064.
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This thesis represents a detailed investigation into aspects of the biology, ecology and population dynamics of two endemic ariid species, Galeichthys feliceps and G. ater, off the southeast coast of South Africa. The two species are exploited as a by-catch in the commercial ski-boat fishery off Port Alfred, a fishery dominated by highly fecund sparid and sciaenid species. They collectively constitute approximately 10% of the total annual catch in terms of landed mass G. feliceps outnumber G. ater in the catches by a ratio of 3:1. The investigation was designed to provide the biological data required for stock assessment and to determine optimum management strategies for the two populations. The implications of their K-selected life-history styles for exploitation received particular attention. While the two species were sympatric and had similar depth distributions they were found to be allopatric with respect to their foraging habitats. G. feliceps foraged over sandy and muddy substrata in marine and estuarine environments. G. ater fed only on reef-associated species and did not utilise estuaries. Their feeding-associated morphologies were identical and both species preyed primarily on crustaceans (brachyuran crabs and isopods), echiurids, molluscs and polychaetes. The diet of G. ater was broader in terms of the number of species consumed. The two species are mouth-brooders with low fecundity. G. feliceps and G. ater produced a mean of 49 and 32 eggs each, per annum. The buccal incubation period was determined to be in the region of 140 days for G. feliceps. Embryos hatched after approximately 75-80 days and the young began exogenous feeding thereafter. The young fed intra-buccally on detritus provided by the parent. Adult buccal mucus may also have been used as a food source. Young were released at a total length of ± 55mm. Adult males ceased feeding whilst mouth-brooding. Body musculature, abdominal fat and liver reserves provided energy for basal metabolism and males lost approximately 28% of their body mass during buccal incubation. Females expended less reproductive energy than males. Catches were dominated by mature fish (76% in G. feliceps and 97% in G. ater). Females were significantly more abundant in catches during the spawning and mouth-brooding period. The female to male sex ratios were 1.65:1 and 2.23:1 for G. feliceps and G. ater respectively. Age and growth studies revealed that the two species mature at advanced ages (10 and 9 years for G. feliceps and 9 and 7 years for G. ater males and females respectively). They are long-lived, reaching ages in excess of 18 years in G. feliceps and in excess of 15 years in G. ater. Females live longer than males and grow larger. Yield-per-recruit and spawner biomass-per-recruit analyses demonstrated that G. ater were exploited below FO.1 at a level where spawner biomass-per-recruit was reduced to between 45% and 65% of the unexploited level. The G. ater stock was not adversely affected by current levels of fishing effort. For G. feliceps, both sexes were exploited beyond F₀.₁ where spawner biomass-per-recruit was reduced to between 30% and 22% of the unexploited level. G. feliceps were shown to be sensitive to relatively low levels of exploitation, a phenomenon attributed to their highly Kselected life-history style. Should the species become targeted for in the future, effort restrictions in the form of a closed season during the spawning and mouth-brooding period would prove effective in reducing effort and conserving the population sex ratio.
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Larsson, Cecilia, and Moa Orvehed. "Carbon Offsetting, a new form of CO2lonialism? : Local implications of tree-planting projects in East Africa." Thesis, Södertörns högskola, Utveckling och internationellt samarbete, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-45657.
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Carbon offsetting has a growing presence on the global climate action agenda where it is promoted as a triple-win for the environment, business and development. However, the opinions on carbon offsetting are divided. Projects with agroforestry and participatory methods are highlighted as having more positive aspects, but critics emphasize that carbon offsetting can become an excuse for the Global North to continue business as usual while using the Global South as a carbon dump. Carbon offsetting can reproduce unequal power structures where countries, while formally decolonized, are still affected by coloniality. This study examines carbon offsetting through tree planting projects and the potential discrepancies between discourse and documented effects in East Africa with focus on Uganda. Four projects are compared with each other, focusing on documented social effects and impacts on land access. We analyze how power structures are expressed in carbon offsetting generally and in the projects. This is a literature study with a combined theoretical framework of political ecology and the decolonial approach. Findings imply that there, to varying degrees, are discrepancies between rhetoric and reality for the projects. Differences between the projects’ outcomes mainly boil down to their planting method, degree of participation and operating logic. All the projects are to varying degrees based on a coloniality, permeated by power structures and have some level of exclusion. However, findings also imply that best practices involve the local communities in a bottom up approach with an agroforestry method and carbon offsetting as a co-benefit.
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Beymer, Betsy Anne. "Women's views on the political ecology of fuelwood use in the West Usambara Mountains, Tanzania." Connect to this document online, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=miami1121958339.
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Thesis (M.A.)--Miami University, Dept. of Geography, 2005.<br>Title from first page of PDF document. Document formatted into pages; contains [1], vi, 99 p. : ill. Includes bibliographical references (p. 77-93).
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Ott, Theresia. "The response of biological communities to spatial and temporal changes in a regenerating coastal dune forest along the north-east coast of South Africa." Thesis, University of Pretoria, 2013. http://hdl.handle.net/2263/26029.
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Ecological restoration that aims to reinstate indigenous processes may be constrained by regional and local conditions, especially those that drive dispersal and colonisation. Local conditions can be managed, while regional conditions cannot. The management of costly rehabilitation programmes is considered best practice when scientifically informed. My thesis documents the responses of biological communities to a range of local conditions developing in coastal dune habitats in response to ecological restoration. Here, landscape-level (spatial structure of patches of tree canopies) local conditions were distinguished from site-level (topography, soil nutrient content, woody plant community richness, microclimatic variables) local conditions. The spatial structure of tree canopies varied over time and differed between the mining lease site and the relatively undisturbed benchmark site prior to (1937- 1970), and after (1990-2006) mining. For example, approximately 20% of the mining lease site and 40% of the benchmark site was covered by tree canopies prior to mining. However, after mining and rehabilitation, the structure of tree canopies began to converge towards that of the benchmark. The topographic profile of coastal dunes was less heterogeneous after mining and rehabilitation than before. Aspect, elevation and gradient of dune slopes were also different and had shifted in space. Variability in the structure of tree canopies could not explain variability in species richness, forest-associated species richness and proportion of benchmark species for the millipede, dung beetle and bird communities ashad been expected. However, species composition did change (though idiosyncratically) with age-related changes in soil nutrient availability and tree species diversity. Temperature, relative humidity and light intensity varied with dune topography, but soil nutrient content (C: N ratio and pH) was better accounted for by the age of the regenerating forest than by dune topography. Similarly, analysis of covariance suggested that tree canopy density, woody plant richness and millipede species richness only responded to the aspect, elevation and gradient of restored coastal dunes when age was taken into account as a covariate. However, the response of keeled millipedes to dune topography, regardless of regeneration age, suggested that the microclimatic variability brought about by topographic heterogeneity may provide these specialists with suitable microhabitats. Throughout my thesis, the age of regenerating patches of indigenous canopies was often more important as an explanatory variable than habitat conditions per se. Age itself is not a determinant of biological communities, but merely the axis along which habitat conditions change with succession, and later, patch dynamics. Therefore, as elsewhere, my thesis has highlighted age as a useful proxy for the response of biological communities to local conditions. It seems that managing local variables such as those considered in my assessment is not an avenue through which to enhance restoration. After kick-starting initial conditions, best practice rehabilitation management should therefore focus on minimizing external disturbances rather than interfering with natural processes.<br>Thesis (PhD)--University of Pretoria, 2013.<br>Zoology and Entomology<br>unrestricted
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Alin, Simone Rebecca. "Calibration and Interpretation of Holocene Paleoecological Records of Diversity from Lake Tanganyika, East Africa." Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/231412.
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Lake Tanganyika is a complex, tropical ecosystem in East Africa, harboring an estimated 2,100 species. Extensive watershed deforestation threatens the biodiversity and ecological integrity of the lake. In this dissertation, ecological and paleoecological methods were employed to study the distribution of invertebrate biodiversity through space and time, with particular emphasis on linkages between biodiversity and land –use patterns. Ecological surveys of fish, mollusc, and ostracod crustacean diversity at sites in northern Lake Tanganyika representing different levels of watershed disturbance revealed a negative correlation between biodiversity and intensity of watershed disturbance. To elucidate the long -term relationship between disturbance and biodiversity, paleoecological records of invertebrates offshore from watersheds experiencing different degrees of anthropogenic disturbance were examined. Life, death, and fossil assemblages of ostracod valves were compared to assess the reliability and natural variability inherent to the paleoecological record. These comparisons indicated that paleoecological (i.e. death and fossil) assemblages reliably preserve information on species richness, abundance, and occurrence frequency at comparable -to- annual resolution. Unlike life assemblages, species composition of paleoecological assemblages reflects input of species from multiple habitat types. Ostracod paleoecological assemblages are characterized by spatiotemporal averaging that renders them representative of larger areas and longer time spans than life assemblages. Thus, paleoecological assemblages provide an efficient means of characterizing longer -term, site -average conditions. Natural variability in ostracod fossil assemblages from a sediment core representing the Late Glacial to the present indicates that abundance of individual ostracod species is highly variable. Ostracod assemblages were preserved in only the most recent 2,500 years of sediment. Species composition of ostracod assemblages reflects lake water depth. Core geochemical data indicate that the coring site may have been below the oxycline for ~2,000 years, inhibiting ostracod survival and preservation. Paleoecological, sedimentological, and stable isotope data revealed differences in biodiversity and watershed disturbance through time offshore from a pair of sites. The protected site is offshore from Gombe Stream National Park (Tanzania), the other offshore from a deforested watershed outside the park. Offshore from the deforested watershed, sedimentation rates increased, and turnover in ostracod species composition occurred during the past 50 years. Comparable changes were not observed offshore from the park.
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Kamau, Peter Ngugi. "ANTHROPOGENIC FIRES, FOREST RESOURCES, AND LOCAL LIVELIHOODS AT CHYULU HILLS, KENYA." Miami University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=miami1374078802.
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Rignall, Karen Eugenie. "LAND, RIGHTS, AND THE PRACTICE OF MAKING A LIVING IN PRE-SAHARAN MOROCCO." UKnowledge, 2012. http://uknowledge.uky.edu/anthro_etds/3.
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This dissertation explores the relationship between land tenure and livelihoods in pre-Saharan Morocco as an ethical struggle over subsistence rights and the definition of community. Research in an oasis valley of southern Morocco indicated how changing land use practices framed contestations over community, political authority, and social hierarchies. The dissertation specifically examines the extension of settlement and cultivation from the oasis into the arid steppe. The research methodology contextualizes household decision-making around land use and livelihood strategies within the framework of land tenure regimes and other regional, national, and global processes. Households with the resources and prestige to navigate customary tenure regimes in their favor used these institutions to facilitate land acquisition and investments in commercial agricultural production. Rather than push for capitalist land markets, they invoked a discourse of communalism in support of customary regimes. In contrast, marginalized families without access to land mobilized to divide collective lands and secure individual freehold tenure. This complicates a prominent critique in agrarian studies that privatization signals the immersion of peripheral lands into neoliberal tenure regimes. The research shows that in southern Morocco, resistance to communal tenure regimes favoring elites was rooted in a discourse of subsistence rights and ethical claims to membership in a just community rather than a simple acquiescence to the power of neoliberal property relations. The dissertation therefore explores the shifting fault lines of social differentiation and the political and cultural embeddedness of land in processes of "repeasantization," the resurgence of rural peasantries in the context of the growing industrialization of global food production. The research draws on cultural anthropology, geography, and political economy to explore an understudied issue in the anthropology of the Middle East and North Africa: the economic and environmental dimensions of agrarian livelihoods and rural social dynamics from a critical theoretical perspective.
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Mutiti, Christine Mango. "Landscape Structure of Acacia-Commiphora Bushland in Southeastern Kenya." Miami University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=miami1280206409.
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Sieff, Daniela F. "The effects of resource availability on the subsistence strategies of Datoga pastoralists of north west Tanzania." Thesis, University of Oxford, 1995. http://ora.ox.ac.uk/objects/uuid:a499a1dd-3c21-4be9-8572-261a9625b85d.
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Many early anthropological studies treated pastoralist populations as egalitarian, however there is considerable variation in the resources available to individual households. This thesis considers how resources influence the subsistence system of the pastoral Datoga of Lake Eyasi. The two categories of resources considered are wealth and labour. The labour available to Datoga households does not influence the herding strategies of those households. In turn, the herding strategies do not affect the dynamics of cattle herds. This is because households that are short of labour can arrange for their animals to be herded by members of different households, and there are no discernible costs associated with this. Wealth, defined by livestock holdings, can be measured either as total household wealth, or as wealth per capita. These are conceptually distinct. Among the Datoga, households that are wealthy in terms of total livestock holdings, are also wealthy in terms of wealth per capita, but not proportionally more so. Once households have about five livestock units per capita, any increase in household wealth is used to attract new people to the household, rather than to increase the wealth of existing household members. For many aspects of the production system overall household wealth and wealth per capita have a similar effect, but this is not always the case. In some instances overall household wealth can explain variation between households, whereas wealth per capita cannot. This occurs when the absolute number of animals belonging to a household is important. In terms of provisioning the household and household economics, per capita wealth explains more of the variation between households. Overall the Datoga are struggling to survive. They have been alienated from more fertile areas, and consequently they are poor, and herd productivity is low. This is due to the low reproduction rate of cattle, and the high commercial offtake rate of both cattle and small stock. The high commercial offtake rate is driven by subsistence needs and most income is used to buy grain and veterinary products. However, there is considerable variation between households, and compared to poor households, wealthy households have a comparatively low offtake rate of livestock, in terms of both mortality and sales. Consequently, they are managing to retain their livestock holdings, or in a few cases to increase the size of their herds. However, wealthy households are in the minority, and the majority of households are caught in a declining cycle of poverty, and will eventually be forced to drop out of the pastoral system.
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Callaby, Rebecca. "Coinfections in East African Shorthorn Zebu." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/14167.
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The Infectious Diseases of East African Livestock (IDEAL) project followed 548 East African Shorthorn Zebu (EASZ) calves in Western Kenya for the first year of life and monitored the sequelae of infections by multiple parasites. More than 50 different parasites were identified during this time. The IDEAL project also gathered environmental information about the farm and collected phenotypic data on the calf and its dam. Calves were also genotyped for 55,777 single nucleotide polymorphisms (SNPs). Recent research has looked at coinfection in rodents and humans but not in indigenous cattle. Here I investigate the evidence for coinfection in EASZ and study the associations occurring between coinfecting parasites. In addition, I examine the genetic and phenotypic factors which predispose an individual to infection with multiple parasites. Using information gathered by the IDEAL project, my thesis consists of the following chapters. An investigation of the nature of concurrent associations and of lagged effects between different parasites. Using the parasites Theileria spp., Coccidia spp., Strongyloides spp., strongyles and Calicophoron spp. I show that the patterns of association between different parasites are complex: there is evidence for both positive and negative associations. For example, infection with Strongyloides spp. increased the risk of strongyle infection. Conversely, in other cases, being infected with one parasite decreased the calf’s risk of infection with another parasite: for example, infection with Strongyloides spp. decreased the risk of infection with Calicophoron spp. A study of the relationship between different respiratory viruses and their effect upon the host. I confirm that positive associations exist between Infectious Bovine Rhinotracheitis (IBR), Bovine Viral Diarrhoea Virus (BVDV) and Bovine Parainfluenza Virus Type 3 (PIV3) in a previously unstudied setting; being seropositive for any one of these three viruses means that an individual is more likely to be seropositive for the other two viruses than expected by chance. Being seropositive for IBR, BVDV or PIV3 did not affect the average daily weight gain of the calf, nor did PIV3 and BVDV serostatus have an effect on the calf ever experiencing a clinical episode. However, IBR seropositive calves were less likely to experience a clinical episode of some form, suggestive of some protective aspect of IBR. An examination of the sources of variation in faecal strongyle egg counts (EPG), and their association with body weight, host genetics and a suite of haematological measures. Using estimates of relatedness derived from the SNP data, I established that strongyle EPG has a genetic basis in EASZ, with a heritability of 23.9% (S.E. = 11.8%) and showed a consistently strong negative association between strongyle infection and the haematological parameters white blood cell count, red blood cell count, total serum protein and absolute eosinophil count. Furthermore, calf body weight at 1 week old was a significant predictor of strongyle EPG at 16-51 weeks, with smaller calves being predisposed to a higher strongyle EPG later in life. A genome-wide association study (GWAS) to investigate if there is a genetic predisposition to East Coast Fever (ECF) death and a genetic basis to the packed cell volume at the time of seroconversion to Theileria parva (PCVTP). I found no robust evidence for a relationship between genotyped single nucleotide polymorphisms (SNPs) and ECF death or PCVTP. The effect of sample size upon GWAS and significance thresholds was investigated further through simulations. I conclude that the small number of cases influences the probability of association between a SNP and the phenotypic trait. Smaller case numbers produce more artifactual associations with SNPs, an effect not fully compensated for by the standard Bonferroni correction, suggesting that an empirical significance threshold should be used to directly account for sample size. The results of this thesis provide an understanding of the associations occurring between different parasites, and of their causes and consequences. I discuss the results in the context of their implications for disease control strategies, suggesting the benefits of an integrated approach to control worm and T. parva alongside the possible genetic selection for parasite resistance and supplementary feeding of lightweight individuals to improve the health of EASZ.
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Berkström, Charlotte. "Ecological connectivity in East African seascapes." Doctoral thesis, Stockholms universitet, Systemekologiska institutionen, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-75194.
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Coral reefs, seagrass beds and mangroves constitute a complex mosaic of habitats referred to as the tropical seascape. Great gaps exist in the knowledge of how these systems are interconnected. This thesis sets out to examine ecological connectivity, i.e. the connectedness of ecological processes across multiple scales, in Zanzibar and Mafia Island, Tanzania. Paper I examined the current knowledge of interlinkages and their effect on seascape functioning, revealing that there are surprisingly few studies on the influences of cross-habitat interactions and food-web ecology. Furthermore, 50% of all fish species use more than one habitat and 18% of all coral reef fish species use mangrove or seagrass beds as juvenile habitat in Zanzibar. Paper II examined the seascape of Menai Bay, Zanzibar using a landscape ecology approach and studied the relationship between fish and landscape variables. The amount of seagrass within 750m of a coral reef site was correlated with increased invertebrate feeder/piscivore fish abundance, especially Lethrinidae and Lutjanidae, which are known to perform ontogenetic and feeding migrations. Within patch seagrass cover was correlated with nursery species abundance. Paper III focused on a seagrass-dominated seascape in Chwaka Bay, Zanzibar and showed that small-scale habitat complexity (shoot height and density) as well as large-scale variables such as distance to coral reefs affected abundance and distribution of a common seagrass parrotfish Leptoscarus vaigiensis. Paper IV studied the connectivity and functional role of two snappers (Lutjanus fulviflamma and L. ehrenbergii) using stable isotopes (δ15N and δ13C) and found that connectivity between habitats was maintained by ontogenetic and foraging migrations by these species. The thesis concludes that ecological connectivity and multi-habitat usage by fish is a general and important characteristic in the Western Indian Ocean and should be considered in management planning.<br><p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 4: Submitted.</p>
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Nuwamanya-Matsiko, John Willis 1950. "The East African Institute of Resource Planning and Management: A proposal." Thesis, The University of Arizona, 1992. http://hdl.handle.net/10150/278139.
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East Africa, a region in Africa south of the Sahara, is faced with many environmental and urban problems due to development and population growth impacting on the land, vegetation and wildlife. This region, at present, does not have its own trained manpower able to plan and manage the natural resources but also to minimize man's impact on these resources in order to achieve sustainable development in the region. The thesis of this study is that a regional institute of resource planning and management be established in one of the three countries in the region to meet this pressing need.
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Sheehan, Meghan Marie. "Determining Drivers for Wildebeest (Connochaetes taurinus) Distribution in the Masai Mara National Reserve and Surrounding Group Ranches." Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1452550498.
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Robinson, Victoria Jane. "The ecology of East African soda lakes : implications for lesser flamingo (Phoeniconaias minor) feeding behaviours." Thesis, University of Leicester, 2015. http://hdl.handle.net/2381/32533.
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This thesis investigates the feeding ecology of the lesser flamingo (Phoeniconaias minor). Studies took place at six endorheic alkaline-saline lakes within the East African Rift Valley, which varied in terms of taxonomic composition and biomass, both spatially and temporally. The lakes could be categorised as Arthrospira fusiformis dominated (lakes Bogoria and Sonachi), diatom dominated (Lakes Natron and Elementaita) or ‘other’ cyanobacteria dominated (lakes Oloidien and Nakuru). From 2009 to 2013, the lake levels were consistently rising with the average biomass reducing concurrently; maximum surface A. fusiformis recorded was > 800 mg L-1 in 2009 at Lake Bogoria, falling to < 50 mg L-1 in 2013. A reduction in average biomass was recorded at all lakes throughout the study period, with the exception of Lake Natron, where higher diatom abundance was recorded in 2011 than in 2009. This study identified 10 distinct feeding behaviours utilised by lesser flamingos at different times of day. Different behaviours were also employed to access different food resources from a variety of niches throughout the aquatic habitat: from the lake’s edge, the open water and the lake-sediment interface. Deep water feeding was occurring in higher frequency than recorded previously, at Lake Bogoria where flamingos were exploiting a highly concentrated food resource of sedimented A. fusiformis, discovered during this study. This confirms that deep water feeding behaviours are more common than only being utilised to access diatoms as an emergency food source, as has been suggested. The time spent feeding was negatively correlated with food abundance across the six lakes with lower biomass requiring longer feeding duration, however, at Lake Bogoria a positive correlation was identified, suggesting re-stocking of energy reserves. A positive correlation was identified between the distribution of food resources within Lake Bogoria and lesser flamingo distribution across the lake. Finally, a significant difference was found between flock density when feeding on different food sources (more densely flocked when feeding on A. fusiformis than on diatoms) or through different feeding behaviours.
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Skov, Martin Wiggers. "Reproduction and feeding ecology of East African mangrove crabs, and their influence on forest energy flow." Thesis, University of Liverpool, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250459.
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LaMalfa, Eric M. "Fire - Herbivory Interactions in an East African Savanna: Effects on Acacia Drepanolobium Trees." DigitalCommons@USU, 2019. https://digitalcommons.usu.edu/etd/7498.
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Globally, changes in plant community structure have occurred in ecosystems where humans have altered natural disturbance regimes. Many plants have adaptive life histories and morphological traits that have coevolved with fire and herbivory, which allows them to thrive despite repeated tissue losses. Therefore, altering the type, frequency, or severity of disturbance affects individual plant growth and competition among species. When these changes benefit or disadvantage different plant functional groups (i.e., grasses, shrubs, trees) it alters ecosystem structure and function. Understanding and predicting these vegetation changes, is critical for conservation and management of biodiversity, wildlife habitat, livestock forage, and water.
Savannas are characterized by the codominance of grasses and trees, but the proportion of tree cover responds dynamically to changes in precipitation, fire, and herbivory. These factors often cause a ‘demographic bottleneck,’ which delays transitions from sapling size (1 m). In this dissertation, I investigated several fire × herbivory interactions to gain a mechanistic understanding of sapling recruitment processes that ultimately affect savanna structure.
I made use of a long-term experiment that used semi-permeable fencing to manipulate presence and absence of different types of herbivores, to explore how fire and different combinations of domestic cattle, meso-wildlife, and megaherbivores (elephant and giraffe) affect sapling recruitment. First, I found clear evidence that a wide range of tree height classes resprout after being top-killed by fire, but they were all subsequently kept short by meso-wildlife browsing. Elephants played a key role in suppressing the largest resprouts after fire possibly because fire had reduced the presence of ant mutualists that defend the trees. Second, I found that in the absence of fire, cattle and wildlife indirectly affected saplings by altering competition with neighboring vegetation. Saplings competed with grass and trees during above-average rainfall years. Bare ground—a condition often caused by overgrazing—was positively associated with sapling growth. The highest sapling growth, however, occurred where large neighbor trees were absent, a condition maintained primarily by elephants browsing and damaging large neighbor trees. Finally, I found that saplings conditioned by pre-fire wildlife “browsing legacies” had high tolerance to combined fire and wildlife browsing. These results help explain how saplings tolerate repeated tissue loss to disturbance. Understanding how interactions between fire and herbivory affect sapling recruitment will help managers effectively use natural disturbance processes to manage savanna structure and function.
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"Inter-epidemic yellow fever ecology in Kenya, East Africa." Tulane University, 2006.
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Nearly 60 years have passed since the discovery of Yellow Fever (YF) in East Africa but the disease has remained enigmatic because of unpredictable focal periodicity, lengthy inter-epidemic periods, and a precarious potential for large epidemics. Endemic and/or enzootic transmission has been poorly documented and, as such, typically remains of little value in predicting future outbreaks. The following studies were aimed at clarifying the ecology and epidemiology of YF in East Africa and detailing a number of important interactions associated with the potential emergence and transmission of YF. Three aims were included in this investigation: (1) a study of the distribution of YF among wild monkeys in Kenya, (2) spatiotemporal descriptions of YF vectors along forest interfaces, and (3) an examination of the efficiency of domestic vectors to transmit a local YF virus genotype. Overall, the study indicates that enzootic YF activity has been limited focally and in duration within Kenya, YF vector-human interactions are relatively limited in domestic areas as compared to the forests studied, and the most important vector of epidemic YF is poorly competent. These results have important implications in regard to the emergence and epidemiological outcomes of YF. The approach taken during these studies was to highlight the dynamics of important eco-epidemiological interactions and to provide practical comparative measures. Ultimately, revealing the underlying drivers and dynamics of YF emergence, as evidenced by causal changes, will require quantifiable measure of these rare events or strongly suggestive evidence from inter-epidemic and epidemic comparisons<br>acase@tulane.edu
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Craparo, Alessandro. "Influence of climate change and variability on Coffea arabica in the East African highlands." Thesis, 2017. http://hdl.handle.net/10539/23558.
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A thesis submitted in fulfilment of the requirements for the degree of
Doctor of Philosophy (Agroclimatology) at the University of Witwatersrand, 2017.<br>Plant development is inherently linked to meteorological variability. The phenology, distribution and production of crops and wild relatives has already altered in response to climate change. Recent years have produced the warmest mean annual global temperatures since 1880, with 2016 setting the highest record thus far. Such profound changes have sparked investigations into the impact of temperature and rainfall on crop development, particularly those with profound economic importance such as coffee (C. arabica). The crop is a fundamental source of income for smallholder farming communities and governments throughout the tropical highlands. However, the impact of climate change on C. arabica has yet to be quantified using empirical data in East Africa, leaving uncertainty in the cultivable future of the crop. Therefore, the objective of this thesis is to investigate the influence of climate change and variability on C. arabica yields and phenology in East Africa.
Using a spatio-temporal approach, trends and relationships between coffee performance and meteorological variables were analysed at different scales and time periods ranging from the macroclimatic national scale (49 year), to the meso- and microclimatic farm level (3 year) scale, and finally to the microclimatic canopy and leaf level (hourly) scales. Data from all three climatic continua reveal for the first time that temperatures, and particularly rapidly advancing night time temperatures, are having a substantial negative impact on C. arabica yields. Forecasting models based on these biophysical relationships indicate that by the year 2050, smallholder farmers would on average harvest approximately 50% of the yield they are achieving today. Warming night time temperatures are also responsible for advancing ripening and harvest phenology. As a result, bean filling and development time is reduced, thereby potentially resulting in lower quality coffee. Trends in precipitation do not appear to have any substantial impact on C. arabica yields or harvest phenology, however, it is proposed that rainfall would act synergistically with temperatures to influence plant development and other phenological phases such as flowering. Finally, thermography is introduced as a novel complementary technique to rapidly analyse the suitability of different agroecological systems on coffee physiology at the leaf level. High temporal resolution (hourly) data, illustrate the success of the method in variable meteorological and environmental conditions. The findings contribute to advancing the protocol for use at the canopy and plantation level on coffee, so that appropriate microenvironment designs and adaptation mechanisms be put in place to accommodate climatic change.
Avoiding increments in night time temperatures is key to maintaining or improving yields and fruiting development. Farming at higher altitudes and novel agroforestry systems may assist in achieving lower night time temperatures. Importantly, data reveal that careful analysis of various cropping systems, particularly at lower altitudes, is critical for providing suitable microenvironments for the crop.<br>XL2017
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Mwachala, Geoffrey [Verfasser]. "Systematics and ecology of Dracaena L. (Ruscaceae) in Central, East and Southern Africa / by Geoffrey Mwachala." 2005. http://d-nb.info/976039796/34.
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Allan, Elizabeth Louise. "Ecological role of free-living bacteria in the microbial food web of the temporarily open/closed East Kleinemonde Estuary, South Africa /." 2007. http://eprints.ru.ac.za/1120/.
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Masikini, Rosemary Joshua. "Spatial variability of macroinvertebrate assemblages and the influence of hydrological and environmental variables along the Sigi River, Tanzania-East Africa." Master's thesis, 2012. http://hdl.handle.net/10400.1/5984.
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The study of investigating the spatial and temporal variability of macroinvertebrate and their
relation to hydrology, hydraulic and environmental factors was done along the Sigi River
during two sampling periods in the dry (March) and wet (May) periods of 2012.
The river was demarcated based on slope ranges and five river zones were identified as
mountains streams (MS), upper foothills (UF), lower foothills (LF), rejuvenated foothills
(REJ) and mature lower river (MR). Samples of macroinvertebrate were collected from the
five river zones and measurements of hydrological (discharge), hydraulics (Depth, velocity
and Froude number) and Environmental (pH, Temperature, substrate, conductivity)
parameters were done in each zone.
In characterizing the macroinvertebrate assemblages along the Sigi River diversity indices
(number of taxa, total abundances, Margalef richness index and ShannonWiener
index) were
calculated and the most representative species for the spatial and temporal variation were
identified. Melanoides and Afronurous showed differences in abundance in two samplings
periods while Cleopatra, Potamonautes, Ephemerythus, Neoperla, Caenis, Ceratogomphus
and Cheumatopsyche showed significant difference among the river zones. Spearman rank
correlation and Distance Linear Model (DistLM) used to revealed physical factors governing
the macroinvertebrate assemblages distribution.
The study demonstrated that the variation of physical factors like discharge, temperature,
conductivity and pH have an important role in the spatial distribution of macroinvertebrate
assemblages along the river and the life cycle of macroinvertebrate (Afronurus) is important
in determining the temporal variability.<br>O estudo de investigar a variabilidade espacial e temporal de macroinvertebrados e sua
relação com a hidrologia, fatores hidráulicos e ambientais foi feito ao longo do Rio Sigi
durante dois períodos de amostragem na estação seca (Março) e chuvosa (Maio) de 2012.
O rio foi demarcada com base nas taxas de inclinação e cinco zonas do rio foram
identificadas como: riachos em montanhas, alto sopé, baixo sopé, rejuvenescente sopé e rio
inferior. Amostras de macroinvertebrados foram coletadas a partir das cinco zonas fluviais e
medições dos parâmetros hidrológicos (descarga), hidráulicos (profundidade, velocidade e
número de Froude) e ambientais (pH, temperatura, substrato, condutividade), foram feitas em
cada zona.
Ao caracterizar as assembléias de macroinvertebrados ao longo do Rio Sigi, índices de
diversidade (número de táxons, abundâncias totais, índice de riqueza de Margalef e ShannonWiener)
foram calculados e as espécies mais representativas foram identificadas para a
variação espacial e temporal. Melanoides, Amphypsyche, Elminae e Afronurous mostraram
diferenças na abundância em dois períodos amostrados, enquanto Cleopatra, Potamonautes,
Ephemerythus, Neoperla, Caenis, Ceratogomphus e Cheumatopsyche apresentaram diferença
significativa entre as zonas fluviais. Correlação de Sperman e Modelo de Distância Linear
foram usados a fim de revelar os fatores físicos que regem a distribuição da comunidade de
macroinvertebrados bentônicos.
O estudo demonstrou que a variação dos factores físicos, como a descarga, temperatura,
condutividade e pH apresentam um papel importante na distribuição espacial na comunidade
de macroinvertebrados ao longo do rio e do ciclo de vida dos macroinvertebrados (Afronurus)
sendo importante para a determinação da variabilidade temporal.