Harmful Algal Blooms in a Changing Climate: Triggers, Detection, and Management

Abstract

Harmful algal blooms (HABs) have emerged as one of the most challenging ecological and environmental problems affecting freshwater, coastal, and marine ecosystems worldwide. These events occur when certain species of algae or cyanobacteria experience rapid population growth and produce harmful effects through toxin production, oxygen depletion, habitat alteration, or disruption of aquatic food webs. In recent decades, the frequency, geographical distribution, and intensity of HAB events have increased in many regions due to the combined influence of climate change, nutrient enrichment, hydrological alterations, and increasing anthropogenic pressure. Rising water temperatures, altered precipitation patterns, ocean warming, and extreme climatic events are creating conditions that favor bloom formation and persistence. Climate change does not act as a single trigger but interacts with nutrient availability, water circulation, and biological processes to influence HAB development. Warmer conditions may enhance the growth of toxin-producing cyanobacteria and harmful marine phytoplankton, while increased nutrient loading from agricultural runoff and wastewater discharge provides the resources required for excessive biomass accumulation. Recent advances in detection technologies, including molecular tools, satellite remote sensing, automated sensors, and artificial intelligence-based prediction models, have improved the ability to monitor and forecast HAB events. However, challenges remain in developing reliable early warning systems, especially in regions with limited monitoring capacity. This review discusses the major environmental drivers of HABs under changing climatic conditions, summarizes current detection approaches, and evaluates management strategies for reducing their ecological and socioeconomic impacts. Particular attention is given to recent scientific advances and integrated approaches combining environmental monitoring, nutrient management, and predictive modelling. Understanding the complex relationship between climate change and HAB dynamics is essential for protecting aquatic ecosystems, fisheries, public health, and water resources in the future.