Influence of temperature and rainfall on cyanobacteria abundance and microcystins persistence in the selected public water supply system

Cyanobacterial blooms pose increasing threats to water safety due to their ability to produce toxic secondary metabolites such as microcystins. This study aimed to assess the abundance of cyanobacteria and the occurrence of microcystins contamination in Malaysia_s water supply system, particularly under local climatic conditions. The Sungai Labu Off-River Storage (ORS) was selected as the study site to investigate the presence of microcystin-producing cyanobacteria and their correlation with environmental factors. Cyanobacterial abundance was determined using photosynthetic pigment measurements (chlorophyll-a and phycocyanin) via portable sensors, and molecular identification was conducted using quantitative polymerase chain reaction (qPCR) targeting the mcyE gene. Microcystins concentrations were quantified using Enzyme-Linked Immunosorbent Assay (ELISA). The relationship between variables was analysed using Pearson correlation, and an artificial neural network (ANN) model was developed to predict microcystins levels based on biological and climatic data. Findings revealed that the highest cyanobacterial abundance and microcystins levels were recorded at 83,521.33 cells/mL and 2.629 _g/L, respectively at the reservoir (Point 2), where Microcystis spp. dominated. Microcystins were consistently detected across all water supply points, including post-treatment stages, though remaining below 1.0 _g/L. Phycocyanin showed a significant correlation with both mcyE gene copies (r = 0.553, p