Characterization of Potential Threats from Cyanobacterial Toxins in Lake Victoria Embayments and during Water Treatment
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Date
2022
Journal Title
Journal ISSN
Volume Title
Publisher
Toxins
Abstract
Africa’s water needs are often supported by eutrophic water bodies dominated by cyanobacteria
posing health threats to riparian populations from cyanotoxins, and Lake Victoria is no exception.
In two embayments of the lake (Murchison Bay and Napoleon Gulf), cyanobacterial surveys were
conducted to characterize the dynamics of cyanotoxins in lake water and water treatment plants.
Forty-six cyanobacterial taxa were recorded, and out of these, fourteen were considered potentially
toxigenic (i.e., from the genera Dolichospermum, Microcystis, Oscillatoria, Pseudanabaena and
Raphidiopsis). A higher concentration (ranging from 5 to 10 g MC-LR equiv. L1) of microcystins
(MC) was detected in Murchison Bay compared to Napoleon Gulf, with a declining gradient from
the inshore (max. 15 g MC-LR equiv. L1) to the open lake. In Murchison Bay, an increase in
Microcystis sp. biovolume and MC was observed over the last two decades. Despite high cell densities
of toxigenic Microcystis and high MC concentrations, the water treatment plant in Murchison Bay
efficiently removed the cyanobacterial biomass, intracellular and dissolved MC to below the lifetime
guideline value for exposure via drinking water (<1.0 g MC-LR equiv. L1). Thus, the potential
health threats stem from the consumption of untreated water and recreational activities along the
shores of the lake embayments. MC concentrations were predicted from Microcystis cell numbers
regulated by environmental factors, such as solar radiation, wind speed in the N–S direction and
turbidity. Thus, an early warning through microscopical counting of Microcystis cell numbers is
proposed to better manage health risks from toxigenic cyanobacteria in Lake Victoria.
Description
Keywords
Drinking water, Rapid sand filtration, Recreational areas, Exposure routes, Microcystis, Dolichospermum, Microcystins
Citation
Olokotum, M.; Humbert, J.-F.; Quiblier, C.; Okello,W.; Semyalo, R.; Troussellier, M.; Marie, B.; Baumann, K.; Kurmayer, R.; Bernard, C. Characterization of Potential Threats from Cyanobacterial Toxins in Lake Victoria Embayments and duringWater Treatment. Toxins 2022, 14, 664. https://doi.org/10.3390/ toxins14100664