Genetic biosensors to measure the activity of toxigenic cyanobacteria: towards a new standardized method to forecast harmful algal blooms

Efficient and proactive management of public health risk associated with cyanobacterial harmful blooms requires appropriate tools that can generate rapid and informative data on the proliferation of toxigenic cyanobacteria in freshwater environments. The present pilot study aimed at assessing the suitability of a new biosensor to follow the population dynamics of toxigenic genera Microcystis, Planktothrix, Aphanizomenon and Dolichospermum to rapidly assess the toxic risk associated with their occurrence. The genetic biosensor is adapted into a simple ELISA-type colorimetric format that has been designed to recognize and quantify ribosomal RNA to rapidly detect a population entering a growing phase. Five different reference lakes in Canada, Switzerland and Luxembourg were selected to conduct temporal series in addition to depth profiles and spatial investigations. Biosensor measurements were compared with (in situ) algal pigment screening, taxonomic analyses as well as microcystin quantification using both standard LC-MS workflows and rapid in situ strip tests. Preliminary results demonstrated a high sensitivity of the biosensor to detect the onset of blooms. The proof-of-concept will provide insights for the use of the biosensor to track toxigenic cyanobacteria and establish risk categories. A conceptual model is presented to implement this new tool into future monitoring programs and early warning systems as a complement to conventional microscopy and toxin analyses.