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Abstract
A study which probed the occurrence and quantitative variations hepatotoxic microcystin in a Sub Saharan drinking freshwater reservoir was carried out between November 2014 and March 2015. Results reveal the presence of MCYST-YR, MCYST-LR, MCYST-RR, MCYST-LA and MCYST-LF variants either in cells collected directly from bloom or toxic isolates cultured under laboratory conditions. Two minor microcystin congeners (MCYST-(H4)YR) and (D-Asp3, Dha7) MCYST-RR) were identified, but not quantified. Variants dominance were in the order MCYST-LR>MCYST-RR>MCYST-YR>MCYST-LA>MCYST-LF across sampling sites. Maximum and minimum concentrations of quantified MCYSTs congeners were (489.25, 50.95 µg toxin/g DW), (98.92, 9.11 µg toxin/g DW), (140.25, 12.07 µg toxin/g DW), (56.99, 6.20 µg toxin/g DW) and (50.46, 3.65 µg toxin/g DW) for MCYST-LR, MCYST-YR, MCYST-RR, MCYST-LA and MCYST-LF, respectively. Analysis of variance (ANOVA) revealed there was a high significant difference between mean microcystin concentrations across sampling sites (p<0.05).