Harmful algal blooms are devastating marine life on an unprecedented scale in the Great Southern Reef of South Australia (1) and are expected to increase with climate change (2-4). A prolonged marine heatwave and calm seas allowed toxic dinoflagellate algae (primarily Karenia mikimotoi) to thrive in stratified coastal waters (2). As harmful algal blooms affect society and environments across jurisdictional boundaries, Australia should coordinate a national management approach (4, 5).
