Incidence of microcystins (Hepatotoxins) in floating scums in the swartspruit river, South Africa

Abstract

A study which probed the bioaccumulation, detection and quantitative variations of microcystins in floating scums of Microcystis flos-aquae employing optimized solid phase extraction liquid chromatography electrospray ionization mass spectrometry was undertaken. A quantitative profile and dominance of MCYST-LR over MCYST-YR and MCYST-RR congeners across sampled sites, as well as the occurrence of MCYST-(H4)YR and (D-Asp3, Dha7) MCYST-RR during the summer months was observed. Analysis of maximum and minimum concentrations of quantified MCYSTs showed 270, 14.10 (µg toxin/g DW), 141.5, 1.43 (µg toxin/g DW) and 72.28, 0.15 (µg toxin/g DW) for MCYST-LR, MCYST-RR and MCYST-YR respectively. One way ANOVA showed there was significant difference between mean MCYSTs concentrations across the sampling sites (P < 0.05) and a marginal significant difference in mean MCYSTs concentrations among variants (P = 0.04). The results suggest that the most prevalent bloom forming species is Microcystis flos-aquae, often producing hepatotoxic microcystins, which can negatively impact aquatic animals and human health. The identification of sites with higher MCYST-YR, MCYST-LR, MCYST-RR concentrations and distributions in the pond and MCYST-LR dominance will be of particular importance to the metropolitan authorities, researchers and general public of the water safety quality of this freshwater reservoir.