Seasonal Occurrence of Microcystin-LR with Respect to Physico-Chemical Aspects of Beira Lake Water

Abstract

Cyanobacteria are well known for their ability to produce a group of cyanotoxins referred as microcystins (MCs). MCs show both acute and chronic hepatotoxic effects on animals and humans. Microcystin-LR (MCLR) is the dominant type of MCs prevailing in Sri Lankan water bodies. The present study records the seasonal variation of MCLR, in the Beira lake waters from January 2013 to January 2014 with respect to some physico-chemical parameters of the lake. Quantification of MCLR was done using photodiode array - High Pressure Liquid Chromatography method (PDA-HPLC). The physico-chemical parameters of the water body were measured using standard methods. Microcystis aeruginosa, Microcystis wesenbergii and Microcystis incerta, were the toxic cyanobacterial species present in the Beiralake while Microcystis aeruginosa (49.63%) was the dominant species. MCLR concentration of the lake varied between 11.45±0.73 to 17.57±0.13 µg/ml throughout the dry season of the sampling period while varied between 13.21 ±0.73 to 25.23±0.42 µg/ml during the rainy season. The Pearsons correlation coefficient analysis done for total toxin concentration and the water quality parameters suggested that the water temperature (r=0.914, pvalue=0.000), and the total phosphate concentration (r=0.988, p-value=0.000) have a strong positive correlation with the total MCLR concentration, while pH (r=0.766, p-value=0.002) has a moderate correlation for the production of total MCLR.