Explore the vast range of titles available.

Lake Victoria, bordered by Kenya, Tanzania, and Uganda, provides one of the largest freshwater fisheries in the world and supports millions in small-scale fishing communities. Historical environmental change, including population growth, nutrient loading, introduced invasive species, and rising temperatures, has resulted in eutrophication and persistent cyanobacterial harmful algae blooms (cyanoHABs) over recent decades, particularly in the shallower gulfs, bays, and inlets. CyanoHABs impact fisheries and food web dynamics and compromise food and water security for nearshore fisher populations. In this study, we examine the social-ecological impact of freshwater blooms on fisher health in one of these eutrophic regions, Winam Gulf in Lake Victoria. CyanoHABs persist for months and produce microcystins and hepatotoxins at levels unsafe for human health. We assessed potential risk and contribution of microcystin exposure through fish consumption, in addition to exposure through water source, and conducted 400 fisher and 400 household surveys. Average microcystin concentrations exceeded the World Health Organization (WHO) guideline for drinking water consistently during the long dry season, and cyanobacterial cell counts surpassed WHO standards for recreational risk in 84% of samples. Hazard quotients for fish consumed by young children were 5 to 10 times higher than permissible levels. In addition, fishers chronicled profound ecosystem changes with direct impact on livelihood, fisheries, and water quality with 77.4% reporting a decline in profit or catch, 83.1% reporting adverse impacts of cyanoHABs on fish in the lake, and 98.2% reporting indicators of declining water quality in the lake overall. Through the application of a social-ecological lens to a public health model, we identified spheres of influence that modify how fishers experience HABs related stressors and risks to provide a starting point at which to identify sustainable strategies to improve food and water security and livelihood for the millions in nearshore communities.

The human health risks posed by exposure to cyanobacterial toxins such as microcystin (MC) through water and fish consumption remain poorly described. During the last two decades, coastal regions of Lake Victoria such as Nyanza Gulf (Kisumu Bay) have shown severe signs of eutrophication with blooms formed by Microcystis producing MC. In this study, the spatial variability in MC concentration in Kisumu Bay was investigated which was mostly caused by Microcystis buoyancy and wind drifting. Small fish (<6 cm) mainly composed of Rastrineobola argentea were examined for MC content by means of biological methods such as ELISA and protein phosphatase inhibition assay (PPIA) and partly by chemical-analytical methods such as LC-MS/MS. Overall, the MC content in small fish was related to the MC content observed in the seston. When comparing the MC content in the seston in relation to dry weight with the MC content in small fish the latter was found three orders of magnitude decreased. On average, the ELISA-determined MC contents exceeded the PPIA-determined MC contents by a factor of 8.2 ± 0.5 (SE) while the MC contents as determined by LC-MS/MS were close to the detection limit. Using PPIA, the MC content varied from 25–109 (mean 62 ± 7) ng/g fish dry weight in Kisumu Bay vs. 14 ± 0.8 ng MC/g in the more open water of L. Victoria at Rusinga channel. Drying the fish under the sun showed little effect on MC content, although increased humidity might indirectly favor photocatalyzed MC degradation.

Lake Victoria provides important ecosystem services including transport, water for domestic and industrial uses and fisheries to about 33 million inhabitants in three East African countries. The lake plays an important role in modulating regional climate. Its thermodynamics and hydrodynamics are also influenced by prevailing climatic and weather conditions on diel, seasonal and annual scales. However, information on water temperature and circulation in the lake is limited in space and time. We use a Regional Oceanographic Model System (ROMS) to simulate these processes from 1st January 2000 to 31st December 2014. The model is based on real bathymetry, river runoff and atmospheric forcing data using the bulk flux algorithm. Simulations show that the water column exhibits annual cycles of thermo-stratification (September-May) and mixing (June-August). Surface water currents take different patterns ranging from a lake-wide northward flow to gyres that vary in size and number. An under flow exists that leads to the formation of upwelling and downwelling regions. Current velocities are highest at the center of the lake and on the western inshore waters indicating enhanced water circulation in those areas. However, there is little exchange of water between the major gulfs (especially Nyanza) and the open lake, a factor that could be responsible for the different water quality reported in those regions. Findings of the present study enhance understanding of the physical processes (temperature and currents) that have an effect on diel, seasonal, and annual variations in stratification, vertical mixing, inshore-offshore exchanges and fluxes of nutrients that ultimately influence the biotic distribution and trophic structure. For instance information on areas/timing of upwelling and vertical mixing obtained from this study will help predict locations/seasons of high primary production and ultimately fisheries productivity in Lake Victoria.

Microplastics (MPs) are emerging pollutants of concern in aquatic ecosystems. Fish ingest MPs accidentally during normal feeding because they resemble prey or by ingesting prey that previously consumed them. Despite severe plastic pollution in Africa, some countries, including Kenya have implemented laws to curb this pollution menace. MPs have scantly been studied in African freshwaters. This study provides empirical data and describes the levels of MPs in four commercially important fish species in Lake Victoria. A total of 95 fish samples were collected from four sampling sites (inshore–offshore waters) between March and May 2022. Microscopy and Attenuated Total Reflectance Fourier Transformed Infrared (ATR-FTIR) spectroscopy methods were used to identify MPs. In this study, 62 out of 95 (65.26%) of the gastrointestinal tracts of the sampled fish contained MPs. The four species showed different proportions of detected MPs among the sampled individuals: 75.00% (Clarias gariepinus), 75.00% (Synodontis victoriae), 71.43% (Lates niloticus), and 59.26% (Oreochromis niloticus). Polystyrene (PS) and poly (perfluorobutadiene) were the main plastic polymers in the fish samples. The condition factors estimated for O. niloticus, S. victoriae, and L. niloticus were > 1 and < 1 for C. gariepinus, respectively. Positive correlations were observed between microplastic numbers and fish length and microplastic numbers and fish weight. However, the low R2 values obtained implied no strong relationship exists between these parameters. These findings provide evidence of microplastic contamination in fish in Kisumu Bay.

Dumpsites are a common way for waste disposal around the world. Since their impact is not controlled, they represent a threat to the public health and to the environment, being a source of pollutants and greenhouse gases. The dumpsite of Ngong (Kajiado County, Kenya) has been addressed since years as a serious issue affecting the surrounding community. A project for its closure and the establishment of a new facility for waste treatment was elaborated in 2017, and recently the conversion of the dumpsite in a park has been proposed by the local authorities. Nonetheless, the framework appears still complex from the environmental, economic and social points of view: any intervention is expected to raise challenges for the municipal solid waste management (MSWM) system in place, which involves many stakeholders, including informal workers of the dumpsite. After presenting a general overview on the MSWM system in place at the time, this paper presents the results of the social assessment (SA) carried out in 2018, where some of the criticalities encountered by the local authorities at a later time were already predicted. In the opinion of the authors, the importance of qualitative and sociological research within a technological project is highlighted by the results of the SA, and the shared methodology can be helpful for practitioners on the field, whose support will enhance the capacity of stakeholders to deal successfully with challenges related to waste management.

Available guidance to mitigate health risks from exposure to freshwater harmful algal blooms (HABs) is largely derived from temperate ecosystems. Yet in tropical ecosystems, HABs can occur year-round, and resource-dependent populations face multiple routes of exposure to toxic components. Along Winam Gulf, Lake Victoria, Kenya, fisher communities rely on lake water contaminated with microcystins (MCs) from HABs. In these peri-urban communities near Kisumu, we tested hypotheses that MCs exceed exposure guidelines across seasons, and persistent HABs present a chronic risk to fisher communities through ingestion with minimal water treatment and frequent, direct contact. We tested source waters at eleven communities across dry and rainy seasons from September 2015 through May 2016. We measured MCs, other metabolites, physicochemical parameters, chlorophyll-a, phytoplankton abundance and diversity, and fecal indicators. We then selected four communities for interviews about water sources, usage, and treatment. Greater than 30% of source water samples exceeded WHO drinking water guidelines for MCs (1 µg/L), and over 60% of source water samples exceeded USEPA guidelines for children and immunocompromised individuals. 50% of households reported a sole source of raw lake water for drinking and household use, with alternate sources including rain and boreholes. Household chlorination was the most widespread treatment utilized. At this tropical, eutrophic lake, HABs pose a year-round health risk for fisher communities in resource -limited settings. Community-based solutions and site-specific guidance for Kisumu Bay and similarly impacted regions is needed to address a chronic health exposure likely to increase in severity and duration with global climate change.

Components of the lower food web (mussels, Caridina and Omena) were collected from stations from Winam Gulf, Lake Victoria, Kenya in 2022 and 2023 to analyze for stable isotopes and total mercury (THg). Temporal comparisons were made with data generated for the same species in 1998. Values of δ15N in mussels and Caridina were similar (6.89‰ vs. 6.78 ± 0.13‰), while Omena occupied an elevated trophic position (9.97 ± 0.24‰) with minor shifts in δ15N over time. All species had elevated δ13C values in 2022–2023 versus 1998 supportive of enhanced eutrophication in the Gulf. THg concentrations exhibited modest spatial differences between sites (< 2.6 fold), but not between Caridina and Omena. Larger temporal differences were apparent relative to spatial patterns with THg concentrations decreasing in study species by 2.8 to 4.1-fold between years. An exposure assessment indicated that Omena, commonly found in local markets, can be consumed up to 0.74 kg/month without generating excess THg exposures.

East Africa’s Lake Victoria provides resources and services to millions of people on the lake’s shores and abroad. In particular, the lake’s fisheries are an important source of protein, employment, and international economic connections for the whole region. Nonetheless, stock dynamics are poorly understood and currently unpredictable. Furthermore, fishery dynamics are intricately connected to other supporting services of the lake as well as to lakeshore societies and economies. Much research has been carried out piecemeal on different aspects of Lake Victoria’s system; e.g., societies, biodiversity, fisheries, and eutrophication. However, to disentangle drivers and dynamics of change in this complex system, we need to put these pieces together and analyze the system as a whole. We did so by first building a qualitative model of the lake’s social-ecological system. We then investigated the model system through a qualitative loop analysis, and finally examined effects of changes on the system state and structure. The model and its contextual analysis allowed us to investigate system-wide chain reactions resulting from disturbances. Importantly, we built a tool that can be used to analyze the cascading effects of management options and establish the requirements for their success. We found that high connectedness of the system at the exploitation level, through fisheries having multiple target stocks, can increase the stocks’ vulnerability to exploitation but reduce society’s vulnerability to variability in individual stocks. We describe how there are multiple pathways to any change in the system, which makes it difficult to identify the root cause of changes but also broadens the management toolkit. Also, we illustrate how nutrient enrichment is not a self-regulating process, and that explicit management is necessary to halt or reverse eutrophication. This model is simple and usable to assess system-wide effects of management policies, and can serve as a paving stone for future quantitative analyses of system dynamics at local scales.

Globally, lake surface water temperatures have warmed rapidly relative to air temperatures, but changes in deepwater temperatures and vertical thermal structure are still largely unknown. We have compiled the most comprehensive data set to date of long-term (1970-2009) summertime vertical temperature profiles in lakes across the world to examine trends and drivers of whole-lake vertical thermal structure. We found significant increases in surface water temperatures across lakes at an average rate of+0.37 degrees C decade(-1), comparable to changes reported previously for other lakes, and similarly consistent trends of increasing water column stability (+0.08 kg m(-3) decade(-1)). In contrast, however, deepwater temperature trends showed little change on average (+0.06 degrees C decade(-1)), but had high variability across lakes, with trends in individual lakes ranging from -0.68 degrees C decade(-1) to+0.65 degrees C decade(-1). The variability in deepwater temperature trends was not explained by trends in either surface water temperatures or thermal stability within lakes, and only 8.4% was explained by lake thermal region or local lake characteristics in a random forest analysis. These findings suggest that external drivers beyond our tested lake characteristics are important in explaining long-term trends in thermal structure, such as local to regional climate patterns or additional external anthropogenic influences.