Lakes Of Africa Research Articles

Evaluation of impact of land use and landscape metrics on surface water quality in the northeastern part along Lake Tanganyika, Africa.

As the second deepest lake in Africa, Lake Tanganyika plays an important role in supplying fish protein for the catchment's residents and is irreplaceable in global biodiversity. However, the lake's water environment is threatened by socioeconomic development and rapid population growth along the lake. This study analyzed the spatial scale effects and seasonal dependence of land use types and landscape metrics on water quality in 16 sub-basins along northeastern Lake Tanganyika at different levels of urbanization. The results revealed that land use types had a higher influence on water quality in urban areas than that in rural areas; the explanatory variance in the urban area was 0.78-0.96, while it was 0.21-0.70 in the rural area. The explanatory ability of land use types on water quality was better at the buffer scale than at the sub-watershed scale, and the 500m buffer scale had the highest explanatory ability in the urban area and rural area both in the rainy season and dry season, and artificial surface and arable land were the main contributing factors. And this phenomenon was more obvious in dry season than in rainy season. We identified that CONTAG was the key landscape metric in urban area and was positively correlated with nutrient variables, indicating that water quality degraded in less fragmented landscapes. The sub-watershed scale had the highest explained ability, while in rural area, the 1500m buffer scale had the highest explained ability and IJI had the highest explanatory variance, which had a negative effect on water quality. Research on the relationship between land use and water quality would help assess the water quality in the unmonitored watershed as monitoring is expensive and time-consuming in low-income area. This knowledge would provide guideline to watershed managers and policymakers to prioritize the future land use development within Lake Tanganyika basin.

Towards improved short-term forecasting for Lake Victoria Basin: Part I – A radar-based convective mode analysis

Abstract East African countries benefit economically from the largest freshwater lake in Africa: Lake Victoria (LV). Around 30 million people live along its coastline and 5.4 million people subsist on its fishing industry. However, more than 1,000 fishermen die annually by high-wave conditions often produced by severe convective wind phenomena, which marks this lake one of the deadliest places in the world for hazardous weather impacts. The World Meteorological Organization launched the 3-year “HIGH impact Weather lAke sYstem” (HIGHWAY) project, with the main objective to reduce loss of lives and economic goods in the lake basin and improve the resilience of the local communities. The project conducted a field campaign in 2019 aiming to provide forecasters with high-resolution observations and to study the storm life cycle over the lake basin. The research discussed here used the S-band polarimetric Tanzania radar from the field campaign to investigate the diurnal cycle of the convective mode over the lake. We classified the lake storms occurring during the two wet seasons into six different convective modes and present their diurnal evolution, organization, and main radar-based attributes, thereby extending the knowledge of convection on the lake. The result is the creation of a “convection catalog for Lake Victoria,” using the operational forecast lake sectors, and defining the exact times for the different timeslots resulting from the HIGHWAY project for the marine forecast. This will inform methods to improve the marine operational forecasts for Lake Victoria, and to provide the basis for new Standard Operation Procedures (SOP) for severe weather surveillance and warning.

Cycles of fusion and fission enabled rapid parallel adaptive radiations in African cichlids.

Although some lineages of animals and plants have made impressive adaptive radiations when provided with ecological opportunity, the propensities to radiate vary profoundly among lineages for unknown reasons. In Africa's Lake Victoria region, one cichlid lineage radiated in every lake, with the largest radiation taking place in a lake less than 16,000 years old. We show that all of its ecological guilds evolved in situ. Cycles of lineage fusion through admixture and lineage fission through speciation characterize the history of the radiation. It was jump-started when several swamp-dwelling refugial populations, each of which were of older hybrid descent, met in the newly forming lake, where they fused into a single population, resuspending old admixture variation. Each population contributed a different set of ancient alleles from which a new adaptive radiation assembled in record time, involving additional fusion-fission cycles. We argue that repeated fusion-fission cycles in the history of a lineage make adaptive radiation fast and predictable.

Spatial trends and ecotoxic risk assessment of selected pharmaceuticals in sediments from Lake Victoria, Uganda, East Africa

Pharmaceutical residues in the aquatic environment are an emerging issue of global concern because of their effects on ecosystems including; antibacterial resistance development and endocrine disruption. Lake Victoria is the largest freshwater lake in Africa, and the second largest lake in the world. It is also the main source of the White Nile River, arguably the longest river in the world, flowing through South Sudan, Sudan, Ethiopia and Egypt, discharging into the Mediterranean Sea. However, its ecology is threatened by rapid industrialisation, urbanization, and increased agricultural activities, which have led to increased pollution via polluted runoffs. In this study, the occurrence of twenty-five pharmaceutical compounds (14 antibiotics, four anti-epileptic and antidepressant drugs, three analgesic and anti-inflammatory drugs, three beta-blockers, and one lipid regulator) was studied in 55 sediment samples obtained from the Ugandan sector of Lake Victoria, and their ecotoxic risk assessed. All the target compounds were quantifiable with levofloxacin (2–120 ng g−1 dm; dry mass), ciprofloxacin (3–130 ng g−1 dm) enoxacin (9–75 ng g−1 dm), ibuprofen (6–50 ng g−1 dm), metoprolol (1–92 ng g−1 dm) and propranolol (1–52 ng g−1 dm) being predominant. Murchison Bay, being the chief recipient of sewage effluents, municipal and industrial waste from Kampala city and its suburbs, had the highest levels. Ecotoxic risk assessment revealed that ciprofloxacin, levofloxacin, sulfamethoxazole, sulfamethazine, oxytetracycline, tetracycline, erythromycin, norfloxacin, ibuprofen, diclofenac, carbamazepine, atenolol, and metoprolol posed high toxic risks to sediment-dwelling organisms (risk quotients, RQ >1). This is the first study reporting concentrations and ecotoxic risks of pharmaceuticals in sediments of Lake Victoria, Uganda, and the whole of East Africa. Detection, identification and quantification of pharmaceuticals in Lake Victoria sediments is essential for gaining knowledge on their occurrence and fate which can ultimately be used to assist in constructing relevant policy and management recommendations.

Community-Managed Fish Sanctuaries for Freshwater Fishery Biodiversity Conservation and Productivity in Malawi

Key fish breeding and other biodiverse areas in Malawian lakes are under threat from illegal fishing, the siltation of key breeding areas (due to deforestation-induced soil erosion), and the clearing of shoreline aquatic vegetation. Freshwater protected areas, also called sanctuaries, have the potential to support the restoration of degraded aquatic environments and protect fisheries’ biodiversity. In Malawi, community-managed fish sanctuaries have been established by beach village committees (BVCs) throughout Lake Malawi, Lake Malombe, Lake Chilwa and Lake Chiuta. The sanctuaries were established to conserve exploited stocks, preserve biodiversity, and enhance fisheries’ yield. The BVCs are aligned with local decentralized village development committees linked to District Councils. Together, they constitute a defragmented decentralized ecosystem-based management of fishery resources. A monitoring study was conducted in sanctuaries in the four lakes during the wet and dry season over three years (2016–2019). The monitoring was carried out to evaluate the sanctuaries’ biological performance. The results showed that community-managed sanctuaries contributed to a 24% increase in the total number of observed species. The Shannon Diversity Index increased from an average 1.21 to 1.52. Small and mid-size (<50 ha) sanctuaries showed a higher performance improvement than large (>50 ha) sanctuaries. This is likely due to multiple factors, including a higher level of fish movement and the greater ability of communities to surveil and enforce smaller sanctuaries. The participation of communities in monitoring enhanced the demonstration effects of sanctuaries. This, in turn, encouraged communities to expand the number and size of the sanctuaries. The biological performance results indicate that community-managed freshwater sanctuaries can be used to protect and restore fish biodiversity in freshwater lakes in Africa. Linking the BVCs to defragmented decentralized structures ensures that the interconnectedness between ecosystem uses, including forestry, agriculture, and tourism, which impinge on fish productivity, are addressed holistically.

Genomic Microevolution of Vibrio cholerae O1, Lake Tanganyika Basin, Africa.

Africa's Lake Tanganyika basin is a cholera hotspot. During 2001-2020, Vibrio cholerae O1 isolates obtained from the Democratic Republic of the Congo side of the lake belonged to 2 of the 5 clades of the AFR10 sublineage. One clade became predominant after acquiring a parC mutation that decreased susceptibility to ciprofloxacin.

Water hyacinth (Eichhornia crassipes) infestation cycle and interactions with nutrients and aquatic biota in Winam Gulf (Kenya), Lake Victoria

AbstractLake Victoria, like many other lakes in Africa, is affected by water hyacinth that reside in several bays for the majority of the year. The weed affects several economic activities of the local communities and denies revenue to the government from blue economic activities related to the lake. The present study examined the interaction of water hyacinth with biotic and abiotic factors and the efficiency of introduced weevils to better control this invasive weed. Water quality samples were collected and compared from the time of water hyacinth re‐emergence and sinking within the Winam Gulf of Lake Victoria. The present study was divided into three phases with an interval of 2 months. Water hyacinth was collected, and the damages resulting from the weevils to the hyacinth, as well as the number of weevils, was recorded and analysed. Fish samples were collected with experimental gill nets. The collected water samples was analysed for the aquatic plant nutrient ammonium, soluble reactive phosphorus, nitrates and nitrites. Data were analysed using R package. The results of the present study indicated that the weevils inhibited nutrient uptake by hyacinth by 17% within the first 4 weeks. The hyacinth subsequently increased the nutrient levels in the gulf by threefold after their decay and sinking. Weevils also increased the sinking rate of water hyacinth through the destruction of their petioles and leaves. One hundred and ninety‐four more fish were observed in the experimental nets during the weed infestation, compared to periods when the weed was absent within the gulf. The major conclusions were that water hyacinth impacts both biotic and abiotic factors, and that the weevils alone are unable to eradicate the weed.

Comparative analysis of two drought indices in the calculation of drought recovery time and implications on drought assessment: East Africa's Lake Victoria Basin

Comparative analysis of two drought indices in the calculation of drought recovery time and implications on drought assessment: East Africa's Lake Victoria Basin

Reflections on almost a century of hydrological studies on Africa's largest lake

Abstract. Lake Victoria is the largest lake in Africa and its outflows strongly influence flows in the White Nile, including the availability of water for hydropower generation, irrigation and water supply. Understanding the water balance is a major challenge since the lake is large enough to influence the local climate and its catchment spans several countries. Hydrometeorological monitoring networks are also sparse in some parts of the basin. In this paper, we consider the history of water balance estimates for the lake and how the science has developed as new information and techniques have become available, including in areas such as seasonal flow forecasting and estimating the potential impacts of dam operations and climate change. These findings are placed into a wider context including the challenges arising from a changing climate and evolving ideas from international research programmes, which lead to some suggestions for future research priorities for Lake Victoria and other sub-Saharan/Rift Valley lakes.

Seasonal flow forecasting in Africa; exploratory studies for large lakes

Abstract. For many applications, it would be extremely useful to have insights into river flows at timescales of a few weeks to months ahead. However, seasonal predictions of this type are necessarily probabilistic which raises challenges both in generating forecasts and their interpretation. Despite this, an increasing number of studies have shown promising results and this is an active area for research. In this paper, we discuss insights gained from previous studies using a novel combined water balance and data-driven approach for two of Africa's largest lakes, Lake Victoria and Lake Malawi. Factors which increased predictability included the unusually long hydrological response times and statistically significant links to ocean-atmosphere processes such as the Indian Ocean Dipole. Other lessons learned included the benefits of data assimilation and the need for care in the choice of performance metrics.

Volcanic Lakes in Africa: The VOLADA_Africa 2.0 Database, and Implications for Volcanic Hazard

Volcanic lakes pose specific hazards inherent to the presence of water: phreatic and phreatomagmatic eruptions, lahars, limnic gas bursts and dispersion of brines in the hydrological network. Here we introduce the updated, interactive and open-access database for African volcanic lakes, country by country. The previous database VOLADA (VOlcanic LAke DAta Base, Rouwet et al., Journal of Volcanology and Geothermal Research, 2014, 272, 78–97) reported 96 volcanic lakes for Africa. This number is now revised and established at 220, converting VOLADA_Africa 2.0 in the most comprehensive resource for African volcanic lakes: 81 in Uganda, 37 in Kenya, 33 in Cameroon, 28 in Madagascar, 19 in Ethiopia, 6 in Tanzania, 2 in Rwanda, 2 in Sudan, 2 in D.R. Congo, 1 in Libya, and 9 on the minor islands around Africa. We present the current state-of-the-art of arguably all the African volcanic lakes that the global experts and regional research teams are aware of, and provide hints for future research directions, with a special focus on the volcanic hazard assessment. All lakes in the updated database are classified for their genetic origin and their physical and chemical characteristics, and level of study. The predominant rift-related volcanism in Africa favors basaltic eruptive products, leading to volcanoes with highly permeable edifices, and hence less-developed hydrothermal systems. Basal aquifers accumulate under large volcanoes and in rift depressions providing a potential scenario for phreatomagmatic volcanism. This hypothesis, based on a morphometric analysis and volcanological research from literature, conveys the predominance of maar lakes in large monogenetic fields in Africa (e.g. Uganda, Cameroon, Ethiopia), and the absence of peak-activity crater lakes, generally found at polygenetic arc-volcanoes. Considering the large number of maar lakes in Africa (172), within similar geotectonic settings and meteoric conditions as in Cameroon, it is somewhat surprising that “only” from Lake Monoun and Lake Nyos fatal CO2 bursts have been recorded. Explaining why other maars did not experience limnic gas bursts is a question that can only be answered by enhancing insights into physical limnology and fluid geochemistry of the so far poorly studied lakes. From a hazard perspective, there is an urgent need to tackle this task as a community.

A remote sensing-based area dataset for approximately 40 years that reveals the hydrological asynchrony of Lake Chad based on Google Earth Engine

As the second largest lake in Africa, the extent of Lake Chad has over 50% seasonal variations with large parts of water under aquatic vegetation. Although a great area shrinkage since the 1960s divided the lake into two parts, namely, the northern and southern basins, it still feeds millions of people from four countries around it. Given sparse in situ measurements, remote sensing with seamless spatial coverage has served for acquiring the long-term area series of Lake Chad. This study retrieves the open (unvegetated) surface water area series of Lake Chad and the total inundation area, including open water and water under macrophytes, combining multiple remote sensing data from around 1980 to 2020 with satellite-based water level and in situ observations at the Bol gauge as validation and auxiliary. Results show that the total inundation area continuously recovered at a rate of 145 km2/year from 1982 to 2020 with large annual fluctuations. Approximately two- to three-month time lags between the open surface water and the total inundation area reveal the hydrological asynchrony of Lake Chad, which can be attributed by the large area of rooted macrophytes. The overspill of the southern surface water flowing over the Great Barrier into the northern lake also has a one-month lag with the open surface water of the southern lake. The Google Earth Engine-based online application can be easily shared for use and data downloaded by the general public, and the open code can be adjusted for any other lakes worldwide.

The impact on food security of a shrinking Lake Chad

The fourth largest lake in Africa, Lake Chad has shrunk by nearly ninety percent since the 1960s, which has impacted food security and livelihoods for fifty million people residing in the Lake Chad Basin. This short communication discusses how decreased rainfall, exacerbated by climate change, and human activity have contributed to the lake's shrinking and recommends individual, national, and multilateral coordinated interventions to ensure food security needs are met for the millions of people who rely on the lake for sustenance.

Application of microsatellite genotyping by amplicon sequencing for delimitation of African tilapiine species relevant for aquaculture

The introduction of new genetic lineages into a population promotes interbreeding or hybridization and can be associated with the loss of genetic adaptation. This may contribute to financial losses for fish farmers following investments into fish strains that do not perform to their expectations. Oreochromis niloticus is one of the tilapiine species that has been widely distributed in areas far from its native range mainly for aquaculture purposes. This is principally due to its fast growth rates, adaptability to new habitats in addition to attractive market prices. Oreochromis niloticus has also been previously associated with the loss of native tilapiine species such as O. variabilis and O. esculentus in Lake Victoria and other lakes in Africa. To understand the impacts of O. niloticus translocation on native fish stocks, its species borders need to be delimited. Here we use microsatellite genotyping by amplicon sequencing (SSR-GBAS) for species delimitation of O. niloticus and seven related species from different regions in East and West Africa obtained from natural and farm environments. In total, 47 markers previously developed for O. niloticus were tested for cross-species amplification resulting in thirty-eight working markers. Most species were represented by different genetic units with little admixture between them even if ocuring in the same waterbodies. Exceptions involved the farmed populations from O. niloticus and O. mossambicus, which may be indicative of hybrid introgression. Our approach did also detect lower genetic diversity on the critically endangered species O. variabilis and O. esculentus. The possibility of introgressive hybridisation between O. niloticus and some of its congenerics may affect the sustainability of its exploitation. Moreover, long-term projects to monitor the response of genetic diversity and species boundaries to anthropogenic activities are required. In this context, SSR-GBAS can be a powerful tool given its high sample throughput and higher reproducibility compared to other methods.

Assessment of the Impact of the Nile Flood on Food Chain in Lake Nasser—Egypt, with Special Reference to Turbidity

This study aimed to assess the impact of the Nile flood with special reference to turbidity on the food chain in Lake Nasser water as one of the largest man-made lakes in Africa before the flood (BF) and after the flood (AF) seasons. To achieve that aim, subsurface water samples were collected from 11 sampling stations along the lake before and after the flood for analyzing the water turbidity, total suspended solids, and total phosphorus, as well as chlorophyll-a and zooplankton to represent the food chain in the lake. Results showed an increase in water turbidity after the flood than that before the flood. Total suspended solids concentration displayed a similar trend as water turbidity. Chlorophyll-a concentration increased in AF all over the lake except at the entrance of the lake, as compared to the BF season. Zooplankton count was represented by copepods, cladocerans, and rotifers with the dominance of copepods in AF and rotifers in BF. The density of zooplankton was higher in the AF than the BF season. The negative impact of flood turbidity had appeared on crustacean organisms.

Water Volume Variations Estimation and Analysis Using Multisource Satellite Data: A Case Study of Lake Victoria

The spatiotemporal changes of lake water resources objectively reflect not only the process of the water resources balance, but also the ecological environment changes in the lake area. In recent decades, climate changes and human activities have caused great impacts on the spatial distribution of the earth’s water resources and the spatiotemporal process of the surface water cycle, which has caused a series of ecological crises and environmental problems, such as the drying-up of inland lakes, the disappearance of the oasis, water shortage or flooding and water pollution. Therefore, monitoring and fully understanding the dynamic changes of lakes is of great scientific significance for grasping regional water balance, water resources management, and sustainable development of the ecological environment. In this study, we focus on using multi-source satellite data on the estimation of water volume and multi-timescale variations analysis for large scale lakes. This study combines the problems in the practical application of “African Water Action”, taking the largest lake in Africa, Lake Victoria, as the study area, and utilizes long-term serial multi-source satellite data of the past 15 years (2003–2017), including Moderate-resolution Imaging Spectroradiometer (MODIS), Jason-1/-2/-3 and Gravity Recovery and Climate Experiment (GRACE) to perform the comprehensive analysis on the water volume change estimation. Firstly, the satellite altimetry data of Jason-1/-2/-3 and MODIS imagery was used to calculate series of water level, and to extract series of water surface area, respectively. On this basis, a more accurate regression model between the area and water level variation (ΔH) was constructed. Then, the model between water volume variation (ΔV) and ΔH, derived from area-ΔH model, was applied to calculate the relative water volume of Lake Victoria. Meanwhile, terrestrial water storage (TWS) changes between 2003 and 2016, derived from GRACE data, were also used for a comparative verification of the ΔV results. The results show the long-term series change trends of ΔV and the TWS are the same. Finally, the multi-timescale analysis of water volume changes was carried out on different time scales, such as the inter-annual, inter-monthly, and variation period.

The Interplay of Regionalism and Statism in Conflict Transformation of the Great Lakes of Africa: A Critical Look at Kenya

The Interplay of Regionalism and Statism in Conflict Transformation of the Great Lakes of Africa: A Critical Look at Kenya

COVID-19 threatens health systems in sub-Saharan Africa: the eye of the crocodile.

The threat of Coronavirus Disease 2019 (COVID-19) to health systems in sub-Saharan Africa (SSA) can be compared metaphorically to a lake in Africa infested with a bask of crocodiles and the saying: "the eye of the crocodile." In the lake, only the eyes of the crocodile appear on the surface while the rest of the body is submerged in water. In this Viewpoint, the eyes and the body of the crocodile represent the public health preparedness and health systems, respectively, in SSA.

Sustainable livelihood alternatives among Nile perch (Lates niloticus) fishers in Lake Victoria Tanzania: analytical hierarchy process (AHP) approach

Sustainable livelihood has been a focal point in many development initiatives by private and public sectors in most African countries. However artisanal fishers in the main lakes of Africa are faced with several alternative decisions to improve their livelihood sustainably. Several studies which have been conducted in Africa offered various options using different models such as sustainable livelihood approach/framework (SLA). This study provides different decision-making alternatives using multi-criteria decision model known as analytical hierarchy process (AHP) to assess the most economical and sustainable livelihood options for Nile perch fishers in Lake Victoria Tanzania. Using structured questionnaires and key informant interviews, different strategic criteria such as environment, economic, social and technology were analyzed and the study found that, important factor in the strategic criteria is environment. Moreover, different livelihood alternatives which include livelihood diversification, fisheries co-management and promotion of aquaculture were analyzed. The study found that livelihood diversification which implies diversifying income-generating activities was identified as the best alternative model for sustainable livelihood development. The study recommends proper income diversification interventions and environment management for the sustainability of Nile perch fishers’ livelihood and fishery resources in Lake Victoria.

Abiotic and biotic responses to the 2016/2017 restoration project at the St Lucia Estuary mouth, South Africa

The St Lucia Estuary is the largest estuarine lake in Africa and has been heavily impacted by anthropogenic activities, which include a history of human-induced sediment loading and separation in the 1950s of the originally common St Lucia Estuary-uMfolozi River mouth. Over the years a number of projects have been implemented aimed at countering the adverse effects that resulted from isolation of the St Lucia mouth. The most recent (2016/2017) project is the Global Environment Facility (GEF) funded initiative to restore the common St Lucia-uMfolozi River mouth. During, but especially after completion of the rehabilitation project, distinct changes in the sediment grain size composition of the estuarine substratum were observed, resulting primarily from deposition of uMfolozi River sediment in the area. Before commencement of the project (i.e. prior to June 2016) coarse and medium sediment (<1 mm >500 µm and <500 µm >250 µm, respectively) dominated. After project completion (July 2017 onwards) the substrate became muddy as a shift from coarse and medium grains to silt (<63 µm) occurred. Preliminary analyses show a corresponding shift in zooplankton and macrofauna composition. Impacts on other animals, including hippopotami and crocodiles, as well as on various flora have also been observed.