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    First investigation of micro-plastics pollution in the River Nile in Khartoum, Sudan: using Nile Tilapia (Oreochromis niloticus) as a bio-indicator
    (University of the Witwatersrand, Johannesburg, 2025-10) Alamin, Hadeel Fudlalla Alsadig; Richards, Heidi; Saad, Dalia
    Microplastics (MPs) have become the bane of the environment for decades, and their impact on freshwater systems is still understudied. In addition to the inevitable and potentially irreversible imbalances in ecosystems caused by particulate matter pollution, environmental standards and coordinated actions are limited by the lack of knowledge about their abundance, distribution, and fate in the ecosystem. This project aimed to generate new data on the occurrence and characteristics of MPs in the River Nile in Khartoum, Sudan, using Nile Tilapia (Oreochromis niloticus) as a bioindicator. The study also aimed to assess the contribution of anthropogenic activities to MP pollution in the River Nile. To achieve this, thirty Nile Tilapia fish samples (freshly caught) were bought from Al-Mawrada fish market. Samples were frozen and transferred to the MPs laboratory at the University of the Witwatersrand, Johannesburg, South Africa. The digestive tracts were removed and individually digested with 10% potassium hydroxide (KOH) to degrade biogenic and natural organic matter that could interfere with MP identification. MP particles were separated according to their density using Sodium iodide (NaI) as a density separator. Nikon light microscope (stereomicroscope) was used to detect and identify MPs based on size, shape, and colour. The surface morphology of MP particles was examined by scanning electron microscope (SEM), and Raman spectroscopy was used to identify the polymer types. The weight of the fish ranged from 0.11 to 1.39 kg with an average of 0.48 ± 0.38 kg. Two-thirds of the fish samples (twenty fish) were identified as males, leaving ten female samples. The values of condition factor (K), except for one sample, were greater than 1, implying that the fish were in good health. A total of 567 particles were recovered from the digestive tracts of the Nile Tilapia, ranging from 5 to 45 MPs/individual fish with an average intensity of 18.90 ± 9.17 MPs/individual. The average abundance of MPs in the fish samples was 72.07 ± 62.06 particles/kg. The examination of the physical characteristics of MPs revealed a predominance of fibers (85.19%), small-sized particles of less than 0.5 mm (30.51%), and coloured MPs (83.60%). However, MPs of other shapes and sizes were also present in considerable percentages, for instance, 25.93% of MPs were detected in the size range of 0.5 - 1 mm, and 27.69% were in the range of 1 - 2 mm. In terms of shape, fragments accounted for 9.52% of the total MPs, while other shapes were present in very small quantities. The chemical characterization of MPs in this study showed two types of polymers, polyethylene (PE) and polypropylene (PP). The high prevalence of fibers and fragments indicates that MP contamination in the River Nile is from secondary sources. These shapes are formed by the fragmentation of macro-plastics. Their potential sources include domestic and industrial effluent, recreational activities, and surface run off from urban centres. This study is the first investigation to assess MPs in the River Nile in Sudan. It provides the first data on their presence and bioavailability, thus providing a benchmark for guiding future monitoring studies and identifying research gaps.
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    The Right to Self Determination for the Khoi-San People in the Western Cape Region of South Africa
    (University of the Witwatersrand, Johannesburg, 2025) Gabaphethe, Thuto
    This research report analyses the extent to which the Khoi-San people in the Western Cape region of South Africa are entitled to self-determination under international law and South African law, and if so, which form(s) of self-determination can they exercise and under what circumstances. A human-rights centred analysis to the right is undertaken to add on to the discourse about a rearranged approach to the concept of ‘self’ in self-determination especially in the post-colonial context. Having considered the substance of the right under international law and South African law, the research report places the Khoi-San people as a people whose subjugation remains embedded in South Africa’s history of colonisation. Within this context, the research report proposes that self-determination should be understood as more people- centred than it might have been in the colonial period. The report thereafter concludes that within this post-colonial framework, the Khoi-San people in the Western Cape region of South Africa are entitled to self-determination. Whether this entitlement is for internal or external self-determination is a question of balancing several interests which the report considers
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    The influence of El Niño Southern Oscillation (ENSO) on rainfall over the mega-dam region of South Africa
    (University of the Witwatersrand, Johannesburg, 2025-08) Abubakar, Mohamed; Steinkopf, Jessica; Engelbrecht, Francois
    This dissertation investigates the impact of the El Niño Southern Oscillation (ENSO) on rainfall variability over the eastern escarpment of South Africa, a key water source for surrounding regions. Using observational rainfall data from the Climate Research Unit (CRU) and ERA5 reanalysis, this study analyses annual and seasonal patterns in response to different ENSO phases, namely El Niño, La Niña, and neutral conditions, from 1981 to 2023. The results show that there is significant regional variability, particularly in the eastern escarpment which tends to record higher annual rainfall compared to other parts of the country. Seasonal analysis of CRU data identifies the December-February (DJF) and September-November (SON) seasons as the wettest periods, whereas the June-August (JJA) season experiences the least rainfall. The results show a strong correlation between ENSO and rainfall variability, particularly during DJF, when El Niño events suppress rainfall, and La Niña phases enhance rainfall. Notably, the severe El Niño events of 1982/83 and 2015/16 led to severe drought conditions. ERA5 data is found to closely align with CRU observations, successfully capturing seasonal rainfall patterns and interannual rainfall variability, though ERA5 data does slightly overestimate rainfall. Composite maps highlight spatial differences in rainfall anomalies associated with ENSO events, clearly identifying the eastern escarpment as one of the regions most impacted by ENSO. Rainfall anomalies are particularly pronounced over the eastern escarpment study site, when compared to the country as a whole, especially during DJF, with El Niño phases significantly rainfall, and La Niña phases enhancing it. This study underscores the importance of understanding how ENSO shapes rainfall variability, with implications for water resource management, agricultural planning, and drought mitigation in South Africa. Improved forecasting of ENSO events could help reduce economic losses and societal impacts linked to extreme weather climates.
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    Vulnerability of affordable housing to global warming in South Africa: case study of a Masonry House in Johannesburg
    (MDPI, 2023-06) Bradley, Ryan
    Global warming is expected to lead to longer and more intense heatwaves, which will have negative environmental and socioeconomic impacts around the world. South Africa is projected to experience significant warming, with surface temperatures possibly increasing by up to 3 ◦C by mid-century. This warming trend has implications for architecture, as the demand for cooling in buildings could rise dramatically. However, socioeconomic conditions in developing countries may limit the use of air conditioning to mitigate indoor overheating. In South Africa, research has shown that government provided low-cost housing structures are thermally inefficient, with temperatures occasionally exceeding outdoor levels. Residents often rely on natural ventilation and personal actions to cope with heat. However, the effects of climate change may render these strategies insufficient if energy poverty and housing improvement are not addressed. This study aims to examine the impact of global warming on a high mass, naturally ventilated, affordable housing structure in Johannesburg, South Africa. Measured operative temperature data from a long-term experimental study, alongside adaptive temperature limits to evaluate overheating, highlight the vulnerability of indoor spaces without adequate insulation and/or thermal mass. The results underscore concerns about the performance of low-cost and affordable housing in warmer future climates in the South African interior
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    Understanding the female athlete: molecular mechanisms underpinning menstrual phase differences in exercise metabolism
    (Springer, 2023) Oosthuyse, Tanja; Strauss, Juliette A.; Hackney, Anthony C.
    Research should equitably reflect responses in men and women. Including women in research, however, necessitates an understanding of the ovarian hormones and menstrual phase variations in both cellular and systems physiology. This review outlines recent advances in the multiplicity of ovarian hormone molecular signaling that elucidates the mechanisms for menstrual phase variability in exercise metabolism. The prominent endogenous estrogen, 17-β-estradiol (E2), molecular structure is bioactive in stabilizing plasma membranes and quenching free radicals and both E2 and progesterone (P4) promote the expression of antioxidant enzymes attenuating exercise-induced muscle damage in the late follicular (LF) and mid-luteal (ML) phases. E2 and P4 bind nuclear hormone receptors and membrane-bound receptors to regulate gene expression directly or indirectly, which importantly includes cross-regulated expression of their own receptors. Activation of membrane-bound receptors also regulates kinases causing rapid cellular responses. Careful analysis of these signaling pathways explains menstrual phase-specific differences. Namely, E2-promoted plasma glucose uptake during exercise, via GLUT4 expression and kinases, is nullified by E2-dominant suppression of gluconeogenic gene expression in LF and ML phases, ameliorated by carbohydrate ingestion. E2 signaling maximizes fat oxidation capacity in LF and ML phases, pending low-moderate exercise intensities, restricted nutrient availability, and high E2:P4 ratios. P4 increases protein catabolism during the luteal phase by indeterminate mechanisms. Satellite cell function supported by E2-targeted gene expression is countered by P4, explaining greater muscle strengthening from follicular phase-based training. In totality, this integrative review provides causative effects, supported by meta-analyses for quantitative actuality, highlighting research opportunities and evidence-based relevance for female athletes.