Aquatic plant-associated toxic cyanobacteria—a new threat to freshwater ecosystems

Toxic cyanobacteria associated with aquatic plants are increasingly reported in freshwater systems worldwide, yet most intensive investigations have followed fatal animal poisonings. We compiled findings from 107 freshwater systems across 12 countries on five continents and demonstrated that toxic or potentially toxic plant-associated cyanobacteria occur globally across diverse habitats and trophic states. Numerous macrophytes host these organisms. Key toxin-producing genera include Aetokthonos, Microcoleus, Phormidium, Geitlerinema, Heterosyctonema, and Microseira, producing neurotoxins such as anatoxins and saxitoxins. However, the influence of host plants on cyanobacterial community composition and toxin production remains poorly understood. We call for systematic surveys of plant-associated cyanobacteria, improved risk assessment approaches, and studies clarifying drivers of occurrence, toxin production, and trophic transfer in freshwater food webs.