Freshwater cyanobacteria in waters intended for human consumption in Serbia: two decades of changes in diversity

Herein we provide an assessment of cyanobacterial diversity and habitat preferences of potentially toxic and alien taxa, which could be an important tool for human health risk assessment regarding recreational and water-supply waterbodies. The diversity changes of cyanobacteria in waters intended for human consumption in Serbia were analyzed two decades after the first floristic study was published. The examination included phytoplankton and phytobenthic sample analysis from 35 localities in the period between 2012 and 2017, together with published literature records. The results indicate that the number of identified taxa doubled since the first Serbian Flora of Cyanobacteria was released two decades ago. The changes most likely occurred due to environmental factors, including hydrological transformations of habitats, cultural eutrophication and global warming. Many frequently recorded taxa are potentially toxic and bloom-forming. The spread of alien species with potentially invasive characteristics has also been noted. Canonical correspondence analysis (CCA) indicates that shallow waterbodies are the most vulnerable regarding the occurrence and expansion of bloom-forming, potentially toxic and invasive taxa. This shows the urgent need for a more detailed investigation. Additionally, although most of the research was focused on planktonic forms, benthic cyanobacteria represent an important component for public health risk assessment and therefore should be more frequently investigated.