Faculty of Agriculture, Engineering and Natural Sciences

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14C dating of organic residue and carbonate from stromatolites in Etosha Pan, Namibia: 14C reservoir effect, correction of published ages, and evidence of >8-m-deep lake during the late pleistocene
(2013) Hipondoka, Martin; Brook, George A.; Railsback, Bruce L.; Marais, Eugene
Lacustrine stromatolites are layered accretionary structures formed in shallow water by cyanobacteria. They are a precise indicator of high lake limits and their morphology and structure provide an insight into paleoenvironments of the time. Previous research on lacustrine stromatolites from Etosha Pan in Namibia based on radiocarbon ages of carbonates were close to the limit of the method and did not account for any possible 14C reservoir effect. The ages were used to suggest that the basin was not extensively flooded during the last 40,000 yr. To assess the reservoir effect, the age characteristics of a stromatolite from Poacher’s Point were investigated by 14C dating both carbonate and organic residue from samples at different depths in the deposit. The ~15-cm-diameter stromatolite was separated into 12 zones from the center to the edge and block samples were cut from each zone; the carbonate and residual organic residue were dated separately. The carbonate ages ranged from 34,700 to 24,700 14C yr BP and the organic ages from 15,700 to 2500 14C yr BP. Ages generally increased with increasing distance from the surface of the deposit. We believe that the organic ages are an accurate estimate of the stromatolite’s age, while the much older carbonate ages reflect incorporation of old carbon from limestone bedrock and ancient calcrete introduced by stream and spring flow. Excluding the 2 oldest organic ages (15,700 and 13,600 14C yr BP), which may reflect contamination by older organic material washed into the lake during flooding, a linear regression relationship between carbonate and organic ages indicates that the reservoir effect on carbonate ranges up to ~24,000 14C yr BP but decreases slightly as the true age of the deposit increases. This regression relationship was used to correct 2 finite carbonate ages for stromatolites from Pelican Island obtained in the early 1980s, which together with our new organic age for a stromatolite from Andoni Bay, document a >8-m-deep lake in Etosha Pan during the Late Pleistocene, at and prior to ~34,000–26,000 cal yr BP. The organic carbon ages from the Poacher’s Point stromatolite suggest prolonged lacustrine conditions during the early to middle Holocene (8000–6600 cal yr BP) but not to the extent seen during the Late Pleistocene
A geochemical baseline study of giant kelp (macrocystis pyrifera) at the kelp blue farm to assess carbon sequestration potential
(University of Namibia, 2024) Mutjida, Protasius Shikusho
The raised levels of carbon dioxide (CO2) in the earth’s atmosphere have contributed to global climate change, which has adversely affected a wide range of individuals, communities, and organizations. One of the ways to mitigate climate change is to grow a huge amount of kelp forests that can absorb carbon dioxide from the atmosphere and sequester it in the deep ocean. To grow these forests, the right biogeochemical conditions (temperature, nutrients, oxygen, salinity, pH, trace metals and ions) within the ocean is vital to assess the sequestration potential and the impacts on the ocean health. This study aimed at monitoring the biogeochemical changes at the proposed Kelp Blue farm and surrounding areas further away from the farm. This study also aims to create a baseline of the chemical composition of the farm and Lüderitz areas, which has not been done before. Using the results obtained from the study, the potential of the cultivated giant kelp to sequester CO2 will be evaluated. This study measured the geochemical parameters using both in-situ probes and laboratory analyses at 10 different locations in Lüderitz (both offshore and coastal): offshore (within the Kelp Blue Pilot project farm, upstream of the farm in the Dumfudgeon rocks, downstream of the farm at Boot Bay and further south of Lüderitz at the Halifax island) and the coastal areas which are adjacent to the offshore study areas including at coastal site of Guano Bay which is about 17 km and the coastal area of Grossebucht which is about 20 km south the town of Lüderitz as another control site. This study also collected sediment samples at these offshore sites including further north of Walvis Bay at the different latitudinal transects. The sediments were analysed for trace metals by using a portable XRF and for carbon content by LOI (Loss on Ignition) method. Another geochemical analysis done was the titrimetric method to CO2 determination of seawater by using NaOH as a titrant the end points were determined. The concentrations of nutrients (phosphates and nitrites) in seawater samples were determined by adding them to a 10 mL cuvette, which had been zeroed first. A specific nutrient reagent was then introduced, and using ii prescribed sample preparation techniques, a spectrophotometer was employed to measure the concentrations of the nutrients in µg/L and mg/L. The geochemical parameters changed in relation to the seasonality and geographical positioning. In a season when the upwelling system was strong, the concentration of nutrients, acidity and the value of the pH, salinity, other geochemical parameters increased more, compared to other seasons and the further southern sampling sites resembled to that of the Southern Benguela Upwelling System (SBUS). Higher concentrations of phosphates (614 µg/L) were found in areas close to the islands. This is due to the presence of guanos. These remarkable long duration geochemical measuring results shows that the cultivated kelp can co-exist with other natural existing kelp beds in this ecosystem, and they can thrive more predominantly in season of great influx of nutrients during the season of strong winds. With a dynamic Benguela upwelling eastern boundary, these kelp forests have an enormous potential to grow more and will function as carbon absorber and eventually sequester more carbon when cultivated at larger scale. To quantify the carbon sequestration potential of these giant kelps, there are other areas to be investigated such as developing a sediment carbon baseline using isotopic analyses, lipid biomarkers, identifying sediment hotspots where the kelp will be deposited, developing a carbon dioxide removal model and geochemical dispersion models. All these other areas will be developed from the baseline being developed by this study. This study recommends that a continuous and rigorous monitoring of the water and sediment geochemical changes be done as the kelp forest grows and as the scale of operation expands
A statistical analysis of endogeneity and instrumental variables of education on income in Namibia
(University of Namibia, 2024) Nanyemba, Maria K.
Education is a well-known driver of income and a causal factor for economic prosperity and social development in modern society. It provides one with capital such as qualification, knowledge and skillsets relevant to secure stable gainful employment, as well as increase one’s income, improve health conditions and general welfare. However, the measurement of the influence of education most often suffers from endogeneity suspicion due to the possible presence of a correlation between the education variable and the error term. This presents a critical issue when performing a cause-and-effect relationship analysis as neglecting endogeneity can lead to unreliable estimation results even when dealing with large samples because estimators of the model parameters will be inconsistent. To date, most studies that focuses on analysing the effect of education in Namibia have done so with other factors such as fertility and not income, while most of these studies used regression approaches such as the linear regression and logistic regression methods to perform their respective analyses. However, no study has simultaneously tried to account for the endogeneity of both education and income in Namibia. Thus, using the 2015/2016 Namibia Household Income and Expenditure Survey as well as accounting for the possible presence of endogeneity and for non-linear effects of continuous observed confounders, this study aimed at estimating the impact of education on income in Namibia, in addition to exploring different modelling strategies to capture the relationship between income and education, and other socio-economic and socio demographic factors. A total of 495,311 households containing 2,250,122 individuals aged 18 to 60 years who have been to school and have earned salary and/or wage as their source of income ii in the last 12 months of the survey period were considered in this study. Three different modelling strategies were carried out, namely: (i) Basic Ordinary Least Squares (OLS) regression without considering the clustering, stratification and weighting factors, (ii) Basic OLS regression considering the clustering, stratification and weighting factors, and (iii) Instrumental Variables & Two Stage Least Squares (IV-2SLS) regression, while the best fit modelling strategy to use for exploring the relationship between income and education, and other socio-economic and socio-demographic factors was determined using the Durbin and Wu-Hausman test of endogeneity. Results from this study showed that majority (82.1%) of the households in Namibia derived their source of income from salary and/or wage in 2015/2016. The IV-2SLS was identified as the best modelling strategy to use since the Durbin and Wu-Hausman test of endogeneity confirmed the presence of endogeneity (i.e, education must be endogenous), thus, making the OLS strategies unreliable to use. Furthermore, factors such as education, age, sex, marital status, type of work, employment period, total hours worked and transport mode to work had positive and significant influences on income, while factors such as region, dwelling unit type, main material for the wall, household size, and no contribution to investment had a negative and significant influences. However, the type of employer had a mixed effect on income. In addition, the IVs estimators revealed that the average rate of return of schooling was 13% which was higher compared to the OLS estimates of 5%. It is therefore recommended that the Namibian government and policy makers consider boosting more funding into education, especially in communities within the rural and underdeveloped regions still having traditional dwelling households whose structures are made of corrugated iron/zinc sticks, wooden poles, clay and/or cow dung. In addition, as part of their poverty alleviation strategies, the government should iii ensure the distribution of equitable resources, particularly the educational resources, to enhance the development of rural and underdeveloped regions so that they too can benefit from high-quality education opportunities in the country
Abundance and diversity of microalgae in freshwater eutrophic systems of Namibia and optimization of lipid and biomass production in Nannochloropsis Limnetica
(University of Namibia, 2017) Garus-Oas, Carol H.
Namibia is one of the driest countries in Sub-Saharan Africa, and man-made dams play an important role on salvaging water. These dams are however periodically frequented by microalgae blooms that pose devastating effects on the water quality, making water treatment processes troublesome and cost prohibitive. However, these unicellular organisms can be exploited in various ways especially when cultivated in controlled and closed systems under optimal conditions of light, temperature, pH and nutrient concentrations. Biomass can be optimized to produce proteins that can be a source of fertilizers, while lipids can be extracted to refine into various hydrocarbons such as biodiesel and bioethanol. It is therefore essential to study the dynamics of these microalgae and provide necessary guidelines on how to utilize them. The first objective of the current study was to assess the seasonal relative genera abundance, diversity, richness and eveness of microalgae in three fresh water eutrophic systems in central Namibia. The hypothesis was to seek whether there is no significant difference in the seasonal relative genera abundance of microalgae per dam in three freshwater eutrophic systems of Namibia namely, Goreangab dam, Von Bach dam and Swakoppoort dam. Microalgae were enumerated with the use of a haemocytometer and identified to genus level during the dry and the wet seasons. Environmental parameters such as turbidity, pH, temperature, dissolved oxygen, macronutrients (i.e. phosphates, nitrates and ammonia) and dam water volumes, were also measured during this time to assess how they are correlated to the relative genera abundance per dam. All statistical analyses were performed using the SPSS software package (IBM statistics Version 23) and differences in data were considered significant at p < 0.05. The Shannon-Weiner diversity index was applied to calculate the microalgae diversity per dam. Evenness Index (J’) and Margalef’s Index (d) was used to calculate the species evenness and species richness, respectively per dam. Results revealed that seasonal relative genera abundance was not normally distributed (p = 0.000) per dam. Von Bach dam seasonal relative genera abundance was statistically not significant (p = 1.000). Goreangab dam seasonal relative genera abundance was statistically not significant (p = 0.652) and Swakoppoort dam relative genera abundance was statistically not significant (p = 0.444). Data presentation of relative genera abundance showed Chlorophyceae as the most dominant class followed by Cyanophycea for Swakoppoort and Von Bach dams for both seasons. Chlorophyceae was the most abundant microalgae class in Goreangab dam during the dry season, while Florideophyceae and Cyanophycea were the second most abundant classes during the wet season. Microcystis was the most abundant genus for Swakoppoort and Goreangab dams during dry and wet seasons. However, in Von Bach dam Aulacoseira was the most abundant microalgae. The Shannon-Weiner diversity index showed that Von Bach dam had the highest diversity of 3.21 followed by Goreangab dam (2.32) and the lowest diversity was found in Swakoppoort dam (2.13). Species evenness varied between 0.46 - 0.65 for Swakoppoort and Goreangab dams, but was higher for Von Bach dam (0.72 - 0.97). Species richness calculated with the Margaleff’s index was around 1 for all the dams and throughout all the seasons, except for Swakoppoort dam during the dry season where it was 1.5. According to the statistical analysis performed, all of the environmental parameters measured for all the dams during the dry and wet seasons were not normally distributed (p = 0.000). Correlation tests showed that all the environmental parameters captured during the time for all the dams were not statistically significant (p > 0.05). According to the literature review, the higher relative abundance of the class Chlorophycea observed during the time of sampling for the current study was due to their higher growth rates. The higher relative abundance of the genera Microcystis was due to their physiological advantage (i.e. nitrogen fixing, surface to volume ratios, intracellular gas vesicles for buoyancy and slimy undulation to enable photomovement) over other microalgae identified during the time of sampling. Microcystis was prominent mostly in Goreangab dam which was characterized by optimum combination of environmental factors such temperature, pH levels and high macronutrients when compared to the other dams. The current study recommends assessment of microalgae diversity and abundance over a one year period with sampling at least every second week. It will be essential to also study other macro-and micronutrients, trace elements, chlorophyll a along with their cumulative effects on microalgae composition. Furthermore, the study advises assessment of topography and mechanical extractions for water transfer on microalgae composition. Moreover, a variety of mesh sizes will constitute a more diversified pool of microalgae to study. The second objective of the study was to optimize the neutral intracellular lipid and biomass production in Nannochloropsis limnetica under variant nitrate concentrations in highly controlled conditions in lab-scaled bioreactors over duration of 14 days. The hypothesis was to seek whether there was no significant difference in growth rate, biomass and neutral intracellular lipid productivity of Nannochloropsis limnetica in “normal nitrate” (3.53 M), “nitrate replete” (7.06 M), “moderate nitrate deplete” (1.765 M), and “high nitrate deplete” (0.8825 M) cultivated under the same conditions of light, pH, temperature and CO2 concentration. The parameters measured throughout this process include optical density to measure growth rates, gravimetrical measurements of bio dry mass/biomass (BDM), ion chromatography measurements for ions, pH as well as sterility tests. All statistical analyses were performed using the SPSS software package (IBM statistics Version 23) and differences in data were considered significant at p < 0.05. During the main-cultivation of Nannochloropsis limnetica, growth was observed in a characteristic pattern consisting of lag, exponential, stationary and declining phases. The growth rates across all of the Flasks during the main-cultivation were not normally distributed (p = 0.012). The statistical tests showed that they were statistically significant (p = 0.001). Bio dry mass increased linearly over time for all of the Flasks from 0 day-1 to the highest on 14 day-1 at the end of the experiment. Bio dry mass was normally distributed (p = 0.055). The statistical test showed that it was statistically not significant (p = 0.939). Bio dry mass and growth rates were moderate and positively correlated and statistically not significant (rs (8) = 0.529, p = 0.077). Relative fluorescence data recorded for all the Flasks was the highest only on the first couple of days during the lag phase and decelerated towards the end of the cultivation period. Therefore, there was no lipid accumulation. The relative fluorescence data captured for neutral intracellular lipid analysis showed that during the cultivation process all of the data were not normally distributed (p = 0.000). Statistical analysis showed it to be statistically significant (p = 0.112). Correlation tests performed between BDM and lipids was strong and negatively correlated and statistically significant (rs (8) = -0.765, p = 0.004). The relationship between lipids and growth rates was moderate, negatively correlated and statistically not significant (rs (8) = -0.501, p = 0.087). The highest growth rates were under “moderate nitrate deplete” at 6 days-1, 11.32 hours at 16.11 OD. The highest BDM value (7780 mg/L) was also captured for “moderate nitrate deplete” at 14 days-1, 19.47 hours at 60.27 mg/L nitrate. The highest relative fluorescence (neutral intracellular lipid content) was captured under “nitrate replete” at 2.387 % at 1 day-1, 6.28 hours and 2550.439 mg/L nitrate. The main-cultivation addressed the hypotheses set out. The study was successful in that it exponentially optimized the biomass production of Nannochloropsis limnetica in each of the four Flasks during the main-cultivation. These results suggest elaborate research on the biomass composition for various outputs such as proteins, lipids, carbohydrates, pigments et cetera. It was discovered during the current study that the various nitrate concentrations did not optimize lipid productivity. Therefore, it is proposed that other macronutrients such as phosphate concentrations along with variables such as light intensity and CO2 be manipulated for lipid optimization. Furthermore, in future studies, the Nile red method should be used in conjunction with other conventional gravimetric methods for lipid quantification and validation for the N.limnetica.
Abundance, species composition and diversity of small mammals and the prevalence and intensity of infestation of associated fleas (Siphonaptera) across an altitudinal gradient along the Ugab river, Namibia
(University of Namibia, 2021) Frans, Alma Inga
The objectives of the study were to determine and compare the abundance, species composition and diversity of small mammals and the associated fleas and to determine and compare the prevalence and intensity of infestation of fleas across an altitudinal gradient along the Ugab River, Namibia. Three sampling sites at different altitudes were selected, Outjo (high altitude site) at about 1300 m above sea level (a.s.l.), Vingerklip (middle altitude site) at about 1000 m a.s.l. and Brandberg (low altitude site) at 400 m a.s. l. Small mammals were trapped in January (hot wet season) and May (cold dry season) in 2018. A total of 159 small mammals belonging to seven rodents and two insectivore species were trapped during the entire study. Small mammals trapped included: Namaqua rock mouse (Micaelamys namaquensis), Natal multimammate rat (Mastomys natalensis), Red rock rat (Aethomys chrysophilus), lesser Red musk shrew (Crocidura hirta), pouched mouse (Saccostomus campestris), bushveld gerbil (Gerbiliscus leucogaster), black-tailed tree rat (Thallomys nigricauda), Acacia rat (Thallomys paedulcus) and bushveld elephant shrew (Elephantulus intufi). The abundance, species composition and diversity of small mammal hosts were not significantly different among the sampling sites during the two seasons (hot wet and cold dry seasons). A total of 139 fleas were collected from small mammals during the study. Three flea species were recorded from small mammal hosts during the study, namely: Xenopsylla cheopis, Xenopsylla brasiliensis and Listropsylla dorripae. The overall intensity of flea infestation (median) per host was not significantly different among the three sampling sites during the hot wet and the cold dry season. Overall infestation prevalence of fleas for the three sites during the hot wet season revealed no significant difference. However, the infestation prevalence of fleas of small mammals was significant among the three sites during the cold dry season. Altitude affects vegetation structure and cover, which in turn affect the small mammal and flea communities. Altitude also affects several climatic factors (temperature, rainfall, humidity), which affect small mammal and flea communities.
Abundance, structure and uses of Baobab (Adansonia Digitata L.) populations in omusati region, Namibia
(2015) Munyebvu, Faith
This study sought to determine the biology and the uses of baobab (Adansonia digitata L.) populations in Outapi and Onesi constituencies in Omusati Region, Namibia. As one of the important Non-Timber Forest Products (NTFPs)-providing species of ecological and socio-economic significance, there is need to have a better understanding of the biology and local uses of the species before its full potential and sustainable harvesting is realized. A comparison of densities, distribution patterns, structure, phenology, stem conditions and uses of baobabs between the two constituencies was done. Field data collection was conducted in April 2014. Road transects were used to sample baobabs in the two sites by purposively choosing the next road to gain access to the next focal tree. Circular plots with a radius of 30m from the edge of the canopy of each focal tree were demarcated. In each plot, diameter at breast height (dbh) of adult and sub-adult trees, height of adults, sub-adults and saplings and their stem conditions, number of fruits on each fruiting baobab tree, the Global Positioning System (GPS) waypoints and coordinates and the land-use types where baobabs occurred were recorded. The results revealed that there was no significant difference in the baobab densities (χ2=2, df=1, p>0.05) and median fruit abundance (U=5550.5, p>0.05) between Outapi and Onesi constituencies. The Chi-square tests detected significant differences in the dbh-size classes (χ2=33.038, df=8, p<0.001) and height classes (χ2=16.295, df=4, p<0.05) between the two study sites. The bell-shaped distribution curve in dbh size-classes in the two sites showed poor recruitment. Onesi constituency had 77% damaged stems compared to 50% in Outapi constituency (χ2=22.705, df=2, p<0.001). Onesi villagers make use of the baobab tree more extensively than Outapi residents (χ2=31.022, df=9, p<0.001). Some of the common uses of baobabs in both study sites include human and livestock consumption and treating various ailments. Poor seedling survival resulting primarily from herbivory, human activities and climate variability hampers baobab recruitment. Considering the poor recruitment due to the above factors, the potential for commercialization of baobabs in the region may not be viable. Therefore, active planting in undisturbed areas, protection of seedlings from livestock coupled with community awareness are vital to ensure recruitment so that effective commercialization and subsistence use is realized and sustainable.
Access coverage for remote connectivity framework (ACRCF): Facilitating scholarship awarding in Namibia
(2015) Ndiwakalunga, Immanuel O.
The corporate world was faced with the challenge of community development. As a result, Namibian companies have been offering scholarships to assist students as best as they can. It was however an insurmountable task to assist the populace without clarity of information or background knowledge. Consequently, the selection of students for scholarships was arguably questionable. Some students awarded scholarships were from rural areas and others from urban areas. However, notice had to be taken of those students in remote area schools where connectivity was lacking. In this age of growing technology, solutions to the dilemma of leaving out worthy students for scholarships should be available with the use of Long Term Evolution (LTE) technologies. The LTE powered technologies would provide seamless interlinking of remote students to the scholarship providers. LTE technologies based on the Access Coverage Remote Connectivity Framework (ACRCF) proposed in this study would deal with the high quality content requirements. The technology would provide a feasible service for the provision of improved interview sessions between students and sponsor selection panels. The interview panels would not have to request students to travel long distances to the interview venues, hence saving travel costs and time by ensuring students are interviewed economically. Interviews would be able to take place over Voice over Internet Protocol (VoiP) and other interfaces under the ACRCF infrastructure. The sponsors would be able to access student information readily at their fingertips through the providence of high quality presented student data on a website maintained under the ACRCF infrastructure. Terminals would be placed at the various remote schools to ensure that student data was updated and ready for use as required. These nodes at the various remote schools would hence be updated with all the student records at the specific remote schools to ensure that there was up-to-date data on the systems at the click of a button. A qualitative research approach was undertaken for the purposes of the study to explore the derivations from case studies. Interviews were held with various sponsors and students to confirm the current state of affairs. They were also held to establish the need for the ACRCF infrastructure to link sponsors to the remote students to improve the scholarship selection process. A quantitative research approach was used in the form of questionnaires handed out to various sponsoring institutions for sampling purposes. The data was analysed with use of the SPSS statistical software program. The findings indicated that selections for scholarships had a need to be improved in the area of equitability. Equitable selection would provide equal opportunities for all students whether in resource rich town centres, rural or remote areas.
African swine fever outbreak at a farm in central Namibia
(2019) Samkange, Alaster; Mushonga, Borden; Mudimba, Douglas; Chiwome, Bernard; Jago, Mark; Kandiwa, Erick; Bishi, Alec S.; Molini, Umberto
An outbreak of African swine fever (ASF) occurred at a farm in central Namibia in March 2018. Fourteen pigs died out of a herd of 59 animals over a period of 16 days between the first and sixteenth of March 2018. The clinical signs observed included sternal recumbency, fever, weakness, pain and reluctance to move, hyperemia of the skin and anorexia, followed by death. Necropsy findings included large amounts of unclotted blood in the pleural and peritoneal cavities, diffuse carcass congestion, splenomegaly, consolidation of both lungs, hemorrhagic and frothy airways and trachea, hepatomegaly and congestion, congestion of the gastric mucosa, enlarged and congested kidneys, ecchymotic epicardial, and endocardial hemorrhages, and very enlarged and congested urinary bladder. All the remaining pigs were euthanized, burned, and buried under state veterinary supervision. The authors concluded that the outbreak resulted from indirect transmission of the ASF virus due to lapses in biosecurity measures.
Age dating of groundwater in perched aquifers Okongo area, Ohangwena region
(University of Namibia, 2019) Masule, Nicco Libuku
Knowledge of groundwater age / residence time in Okongo perched aquifer is important in understanding key issues in the evolution of groundwater, recharge rates, recharge mechanisms, resource renewability, flow rate and distribution of recharge areas. The build-up in the atmosphere of trace gases such as sulfur hexafluoride (SF6) and tritium (3H) from over a centenary ago offers a convenient way of dating groundwater up to the age of 60 years. These gases are well mixed in the atmosphere; therefore, their input functions help to provide information about groundwater age, distribution and recharge patterns. In this study, sulfur hexafluoride and tritium were used as an age dating tracer for shallow groundwater. The focus of the study was to understand how age dating of groundwater in a perched aquifer system can help to determine recharge dynamics, e.g. recharge rates, processes, and vulnerability of these aquifers to pollution. The study consequently contributes to the knowledge on shallow groundwater in respect to the effectiveness of age dating methods to determine age / residence time of groundwater in perched aquifers. The study’s objective was to determine the residence time, investigate the distribution of recharge and examine the origins of recharge to the perched aquifer using sulfur hexafluoride, tritium and hydrochemistry, stable isotopes (2H and 18O) methods. A total number of 26 groundwater samples were collected during two separate sampling seasons / campaigns namely in October 2016 (for tritium and stable isotopes testing) and April 2017 (sulfur hexafluoride, hydro-chemistry and stable isotope). Samples were then grouped into sub-sets of six samples (18O and 2H) and five sample sets (SF6, 3H) by method of analysis and by the six (6) sampling sites namely Omboloka 1 and 2, Ohameva, Okamanya, Oshanashiwa and Epumbalondjaba. The results on concentration of SF6 in the groundwater samples indicate that recharge to the perched aquifer happened in 2000 for Omboloka 2, with a groundwater age of 17 years; Ohameva in 2010 with an age of 7 years; Okamanya in 2012 with an age of 5 years; and Omboloka 1 and Oshanashiwa in 2016 with an age of 1 year. Epumbalondjaba borehole was not sampled during the sampling campaign due to the site being flooded. Applying a conservative mixing ratio model, the samples were observed to have a higher proportion of young water compared to old water. This proves that the groundwater in the perched aquifer is young with a short residence time. Furthermore, the tritium method used to calculate theoretic/hypothetic activities suggests that groundwaterat Ohameva, Okamanya, Omboloka 1 and Oshanashiwa, is sub-modern. While results for Epumbalondjaba and Omboloka 2 portray a mix of both sub-modern and modern water. The ionic composition of groundwater in the perched aquifer presents three groups of water types characterised by mixed zone water, Na+-K+-HCO3 and Ca2+-Mg2+-HCO3. The perched aquifer system is dominated by the Ca2+-Mg2+-HCO3 water type which is a result of the dissolution of calcrete and the formation of carbonate-rich rocks derived from recent recharge with short residence times. Stable isotopes show that groundwater in perched aquifer systems is enriched in heavy isotopes and has been subjected to evaporation, which is caused by the prevailing climatic and hydrological conditions in the area. This shows that groundwater recharge to the perched aquifer originate from the local catchment systems. Therefore, it is recommended that thetrace gases (sulfur hexafluoride and tritium) methods should be applied to a wide range of groundwater in the perched aquifers of the Okongo area in order to understand recharge areas better. It is necessary to further investigate the groundwater chemistry and isotopic composition of perched groundwater aquifer in more detail. It is further recommended that a long-term monitoring programme consisting of sampling stations for water levels, water quality and stable isotopes is established.
Age determination and growth rate of the northern Benguela saddine (Sardinops sagax)
(2015) Malakia, Maria
The main objective of this study was to determine sardine age by counting rings on otoliths and to analyse the length, age and growth through regression and Von Bertalanffy Growth models. Otoliths amounting to 826 pairs were collected from the annual sardine research survey of the Ministry of Fisheries and Marine Resources in October 2013. A total of 713 sardine otoliths were mounted on black Perspex plates and aged by means of counting rings using a Zeiss microscope at a magnification of 22x. A micrometer (4 epu = 1 mm) was used to measure the radius and distance of rings from the nucleus on each otolith. In total, six age groups were represented in the sample, including, zero, one year, two years, three years, four years and five year age groups. The one year old age class was the dominant age group. Mean lengths at age were determined for each age group and were as follows: Zero age group had a mean length of 13.8 cm, one year olds were 16.8 cm, two year olds were 19.6 cm, three year olds were 21.4 cm, four year olds 22.4 cm and mean length for the five year age group was 23.4 cm. All these lengths were significantly different from each other, except the four and five year age groups. Fish length and otolith radius relationship was strong (r = 0.75, p < 0.05). The estimated parameters for the Von Bertalanffy Growth model were: = 26.6 cm, K = 0.28, and t0 = 2.69. Growth rate of females (K = 0.2256) was lower than males (K = 0.3188).
Aloe Zebrina Baker
(2010) Ndeunyema, Nghitoolwa E.
Analysis of antibacterial activity of Terminalia Sericea and Combretum Imberbe two combretaceae species from Namibia
(University of Namibia, 2019) Mapiye, Samson
The study was conducted to investigate the antibacterial activities of stem and leaves from Terminalia sericea and the live and dead bark from Combretum imberbe. The aqueous and organic crude extracts of the two plants were tested on Gram-negative bacteria Escherichia coli, Shigella sonnei, Serratia marcescens, Helicobacter pylori and Gram-positive bacteria Enterococcus faecalis, Staphylococcus aureus and Clostridium perfringens using the disk diffusion method. All the crude extracts exhibited activity against the tested bacteria species except for extracts from C. imberbe (dead bark). Organic extracts had high activity with minimum inhibitory concentration (MIC) values of 0.1mg/ml for all plant parts against S. aureus , S. marcescens, and H. pylori whilst the aqueous extracts from T. sericea (stem and leaves) and C. imberbe (live bark) had MIC values of 1mg/ml all against S. marcescens and H. pylori. Fractions from the two plants were obtained by vacuum liquid chromatography (VLC) using different solvents with increasing polarity. The organic extract fractions from both plants were observed to have good activity against two of the seven bacterial species that were tested. The dead bark plant extracts from C. imberbe had MIC value of 10mg/ml with 100% Ethyl acetate extracts against the bacteria H. pylori. T. sericea leaf extracts had MIC value of 0.01mg/ml against H. pylori in 100% MeOH fractions whilst the stem extracts had activity at 0.01mg/ml against E. faecalis in 100% Acetone fractions. The results indicate that the two plants have good antibacterial activity hence further research is needed to isolate and identify active compounds which can be developed into effective drugs.
An analysis of antibacterialactivity of Terminalia Sericea and Combretum Imerbe two comretaceae species from Namibia
(University of Namibia, 2019) Samson, Mapiye
The study was conducted to investigate the antibacterial activities of stem and leaves from Terminalia sericea and the live and dead bark from Combretum imberbe. The aqueous and organic crude extracts of the two plants were tested on Gram-negative bacteria Escherichia coli, Shigella sonnei, Serratia marcescens, Helicobacter pylori and Gram-positive bacteria Enterococcus faecalis, Staphylococcus aureus and Clostridium perfringens using the disk diffusion method. All the crude extracts exhibited activity against the tested bacteria species except for extracts from C. imberbe (dead bark). Organic extracts had high activity with minimum inhibitory concentration (MIC) values of 0.1mg/ml for all plant parts against S. aureus , S. marcescens, and H. pylori whilst the aqueous extracts from T. sericea (stem and leaves) and C. imberbe (live bark) had MIC values of 1mg/ml all against S. marcescens and H. pylori. Fractions from the two plants were obtained by vacuum liquid chromatography (VLC) using different solvents with increasing polarity. The organic extract fractions from both plants were observed to have good activity against two of the seven bacterial species that were tested. The dead bark plant extracts from C. imberbe had MIC value of 10mg/ml with 100% Ethyl acetate extracts against the bacteria H. pylori. T. sericea leaf extracts had MIC value of 0.01mg/ml against H. pylori in 100% MeOH fractions whilst the stem extracts had activity at 0.01mg/ml against E. faecalis in 100% Acetone fractions. The results indicate that the two plants have good antibacterial activity hence further research is needed to isolate and identify active compounds which can be developed into effective drugs.
Analysis of causes and risk factors associated with maternal deaths in Namibia
(2015) Mulama, Lihongeni N.
Maternal mortality is a major health concern in Namibia as it is the case in most countries. The rate at which women are dying due to pregnancy related causes is high and the cause as well as risk factors are not well explored. The main objective of this research was to identify the causes and risk factors associated with maternal mortality in Namibia and thus the study described the socio-demographic characteristics and three delays that lead to maternal deaths in Namibia. The paper also aims to propose strategies for midwifery practice, in order to prevent maternal deaths in future. Data on health facility based review of maternal records from 13 regions in the country during the period of 2008-2012 was used. This was then complemented by the 2011 Namibia Population and Housing census data. For the health facility data, a case control study design was applied, with a total number of 154 maternal deaths included in the study as cases and 770 women of reproductive ages who fell pregnant during the study period and survived as controls. A logistic regression model was used to assess the risk factors associated with maternal deaths. For the Census data, measures of maternal mortality, such as maternal mortality ratio, maternal mortality rate, lifetime risk of maternal death, and proportion of maternal deaths among women of reproductive age were estimated. Based on the health facility data, of the 154 maternal deaths reviewed, 58.4% were from direct maternal deaths and 41.6% were from indirect maternal deaths. Haemorrhage (37.8%), eclampsia (24.4%) and puerperal sepsis (23.3%) were the leading causes for direct maternal deaths. About 65% of the haemorrhage cases; 64% of the eclampsia cases and 53% of the puerperal sepsis occurred to women who lived in rural areas. The predominant recognizable indirect causes were HIV (45.3%); pneumonia (23.4%) and tuberculosis (17.2%). Maternal deaths are less likely to occur to women living together with their partner than those who are not living together (OR = 0.53). Most women experienced first (51.3%) and third delays (51.9%). Only few women experienced a second delay (12.9%). However it is important to note that some women experienced more than one delay and in some cases all delays were experienced. Using the 2011 Census data, maternal mortality ratio was 547 deaths per 100 000 live births. The highest ratio of 1954 deaths per 100,000 live births is recorded for women in the age group of 45-49 years. Maternal Mortality Ratio is also observed to be high among the teenage mothers between the age group of 15-19 years with an estimate of 421 deaths per 100,000 live births as compared to 318 deaths per 100,000 live births estimated for women aged 20-24 This analysis reinforced previous findings pointing to the fact that haemorrhage and eclampsia are the leading causes of maternal mortality in Namibia and other developing countries. This indicates the need for better obstetric care, particularly for women over thirty years of age.
Analysis of food safety and food handling knowledge among street food vendors in selected local food markets in Windhoek
(University of Namibia, 2022) Ngalangi, Paulus
Contaminated food leads to foodborne disease outbreaks (FDO) that cause millions of deaths among people every year. In Namibia, many low and middle-income consumers use street-vended foods (SVF) with compromised quality of raw materials, degraded handling and storage conditions that do not meet food safety standards. Therefore, this study was conducted by means of a descriptive, cross-sectional study of six Windhoek locations of Okuryangava, Katutura, Klein Windhoek, Kleine Kuppe, Prosperita, and Otjomuise. Food samples were purchased for laboratory analysis to determine pH, moisture and total plate count (TPC). Systems-Theoretic Accident Models and Processes (STAMP) was adopted, informed by data gathered based on event chain models drawn from street food handlers (SFH). Food-handlers were knowledgeable about the need for hygienic practices such as hand washing (94.6%), and cleaning of utensils (83.5%). Knowledge on food pathogens revealed that 72.1% did not know food pathogens such as Salmonella, Listeria, Campylobacter, and E. coli, meanwhile, only 28.4% did not know that parasites, fungi, and viruses act as agents to cause food poisoning. There is a none-consistent pattern of SFH knowledge with regard to hygienic practices during food handling and processing. pH values were lower (3.21±0.29) for liquid beverage than all solid foods that ranged from 6.81±0.10 to 7.54±0.16. The moisture percentage was higher (90.97±0.85) for liquid beverage than all solid foods that ranged from 37.66±1.20 to 63.28±0.89. High TPC of 5.28±0.49 Log CFU/g was detected in matangara, followed by sausage (5.06±0.99), kapana (3.07±0.47), and oshifima (2.66±1.99). STAMP with ready to use scenarios was introduced to deal with accidents that lead to FDO. Moreover, an assessment of the potency and appropriateness of food preservation methods and preservatives are ii recommended. A robust food safety regulatory regime, including a strong component of food safety training for contamination prevention should be pursued and is recommended for SVF handlers
Analysis of malaria transmission dynamics in human and mosquito populations
(University of Namibia, 2024) Shaanika, Hilma Yvonne
This mini-thesis presents a deterministic mathematical model for the spread of malaria in human and mosquito populations. The human population is divided into four com partments while mosquito population is divided into three compartments. Suscepti ble humans can be infected when they are bitten by an infected mosquito, they then progress through the exposed, infected, recovered before going back to the susceptible class. Susceptible mosquitoes can be exposed to the disease and once they are exposed, they can be infected, and remain infected until they die. Basic reproduction number, R0 was established and used to determine whether the disease dies out or persists in the population. It was shown that the disease-free equilibrium point is locally asymptoti cally stable when R0 < 1 and unstable when R0 > 1. Quantitative analysis of the model was carried out to confirm the findings from qualitative analysis. Result obtained indi cate that the findings of quantitative analysis correspond to the findings of qualitative analysis. It was proven qualitatively that R0 < 1, which corresponds to the results of the sensitivity analysis, that was carried out quantitatively. It was recommended that future work can be done to investigate the stability of the endemic equilibrium point
Analysis of marine biotoxins: Paralytic and lipophilic shellfish toxins in Mussels (Mytilus Galloprovincialis) along the Namibia coastline
(2015) Dijerenge, Kahe J.
The study was carried out along the Namibian coastline, this includes Henties Bay, Swakopmund, Bird Island, Walvis Bay and Lüderitz to assess presence of shellfish marine biotoxins in mussels, Mytilus galloprovincialis which are filter feeders and feed on some of the algal species that produces phycotoxins, that can negatively affect the mariculture industry and human health. Samples were analysed for Paralytic and lipophilic shellfish toxins; including environmental parameters and phytoplankton species composition. Samples were collected using randomized sampling techniques for the period of May 2012 to April 2013. Mussel toxin content was measured by liquid chromatography-mass spectrometry (LC-MS/MS) for lipophilic toxins and paralytic shellfish poisoning Mouse bioassay (PSP MBA). The diarrhetic shellfish poisoning (DSP) toxin profile was found to be primarily composed of Okadaic acid (OA) and dinophysistoxins-1 (DTX-1), with the highest concentration recorded at Walvis Bay area, each toxin accounted for at least 50% of the total toxin content, this is probably due to the Dinophysis species reported in this area during the sampling period. In addition, Yessotoxin (YTX) and its analogues 1a-Homoyessotoxin (homo-YTX) and 45- hydroxy-yessotoxin (45-OH-YTX) were all detected at concentrations below the regulatory limit of 1 mg YTX equivalents/kg with homo-YTX dominating at Swakopmund and Bird Island stations with the highest toxin content of 0.14 mg YTX equ./kg recorded at both stations. Furthermore, PSP toxin contents in mussels were only detected at Walvis Bay and Lüderitz, with highest toxin concentrations of 80 and 903 μg STX equivalents/100g respectively. This coincided with the time at which Alexandrium species cell concentration at Lüderitz were at maximum, and could be a source of the paralytic shellfish toxins (PST). Although the toxin content in mussels were generally low, it still highlights the importance of a continued monitoring of both shellfish toxicity and their causative phytoplankton species, in order to produce safe shellfish for both local and international consumers.
Analysis of predator-prey models with infection in both species and human intervention
(University of Namibia, 2024) Khoa, Lutopu
The intricate interplay between infectious diseases and predator-prey dynamics holds pivotal significance. Within this context, our focus centres on the impact of human intervention through treatment and vaccination. This study delves into a predator-prey system, categorizing the populations as susceptible, infected with the disease, vaccinated when inoculated against infection, and under treatment post-infection. We formulate four comprehensive mathematical models that illustrate varying levels of human intervention: no intervention, intervention in the prey only, inter vention in the predator only, as well as intervention in both species simultaneously. Mathematical proofs of model positivity are provided. Following the derivation of equilibrium points, we analyse their stability by examining the signs of the eigenvalues from the Jacobian matrix and using the Routh-Hurwitz criteria. To verify our qualitative analysis findings, we conduct simulations using varied parameters in Matlab. We then draw conclusions regarding the impact that human intervention can have on a predator-prey system with infection. Simulation results indicated that without human intervention, predators faced extinction, whereas with treatment and vaccination in either the prey alone or in both predator and prey, the intervention demonstrated a positive effect, preventing the extinction of any species. Therefore, this study concludes that human intervention plays a crucial role in preventing species extinction
Analysis of seasonal variation in dietary composition and behaviour of wild chacma baboons (Papio ursinus) in two habitats of different human influence around windhoek, central Namibia
(University of Namibia, 2024) Mukuve, Bernhard Z.M.
Diet composition of an organism gives a holistic picture of what an organism forages on in its environment to maximize energy intake for all its essential activities that contribute to survival and successful reproduction. Chacma baboons have the ability to modify their broad omnivorous diet and behavior under changing environmental and climatic conditions. However, the ever-increasing environmental and anthropogenic pressures on baboon populations are likely to affect both the diet composition and foraging behavior of these animals. Moreover, Namibia being one of the driest countries in the Sub Saharan Africa, and coupled with accelerated anthropogenic changes, baboon populations, especially those thriving in and around the city of Windhoek are facing constant threats of habitat destruction and fragmentation due to the rapid expansion of the city and are under pressure to adapt to these changes in order to survive. With limited research carried out on primates in the central highlands of Namibia, this study was carried out in an effort to bridge the knowledge gap and obtain insight into the influence humans have on the ecology of these primates around the city of Windhoek. The study investigated the activity budget and diet of the baboons using data collected from two contrasting habitats (Dobra and farm Krumhuk) that are influenced by human activities. A total of 166 baboons were observed during 2 seasons (wet & dry) at two sites using a focal animal method. Forty-nine (49) scat samples were collected between the seasons, separated in the laboratory, weighed, and placed into four categories (fruits and seeds, roots, stems, and leaves, invertebrates, and others). Results showed that baboons consumed plant materials more than any other food type and that they maintained their diet profile across the seasons. Furthermore, their behavior was found to be reactional to seasonal changes. The study further confirmed the ii broad diet and selectivity that exists in the so-called “generalist diet” of these well documented old-world monkeys while also providing an alternative method to enhance scat analysis techniques in the laboratory. The study noted that the human-disposed food waste, stable and constant water supply, preserved wild flora and minimal disturbance regimes around human settlements, all contribute to increased contact with humans
Analysis of short tandem repeat loci for forensic use in Namibia
(University of Namibia, 2020) Lukas, Ann-Angelique
In the genetics section of the forensics laboratory, in Windhoek, Namibia, forensic DNA (deoxyribonucleic acid) typing has become an integral part of establishing familial relations as well as providing weight to evidence during criminal investigations. Currently, there is limited existing knowledge regarding the ethnic and racial genetic diversity of the Namibian population. In the present study, biological samples from 150 individuals from three racial groupings selected for the paper were used to generate a reference DNA database. The data was analysed at 21 short tandem repeat (STR) loci to observe the genetic variation between individuals of different racial groupings. In order to obtain the STR profiles, the Globalfiler Express kit from Life Technologies was used. The extracted samples were amplified and detected by the Genetic Analyser 3500 as STR profiles, with its recommended allelic ladder. Allele frequencies from the STR profiles were used to evaluate the forensic efficiency parameters such as the power of discrimination (PD), power of exclusion (PE) and the expected heterozygosity (He). Locus point SE33 exhibited the highest polymorphism and was the most informative during the study, whereas TPOX and D13S317 were the least informative. The findings in this study would be useful in assisting the Namibian legal system as well as other relevant bodies in human identification. The findings provided a method for characterizing the genetic structure of the Namibian population and suggested valuable information required to generate a standard online reference DNA database, thus motivate population studies on the Y-chromosome and mitochondrial DNA which could be useful in human identification of complex cases.

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