In a marine ecosystem,phytoplankton not only serves as the base of the food web,but also plays an important role in the biogeochemical cycle.However,some of the species could form exceptional blooms and cause significant damages to local economies,marine ecosystems,global biogeochemical cycle and human health.These events are known as harmful algal blooms (HABs),and are also commonly called Red Tides because some blooms can discolor the water in red or brown.HABs have increased in frequency,geographic extent,and intensity with eutrophication and global climate change,and its research is increasingly catching attention.In this review,we summarize the major progress in HAB research in the last decade,covering topic areas of species identification,influencing factors,and the molecular mechanisms of bloom formation.The current challenges and future prospects of HAB study are also discussed.Over the past 10 years,advances have been made in HAB research,which can be summarized as follows.(1) Many new HAB species have been identified and the taxonomy has been significantly reconstructed and improved.(2) New methods and technologies for HAB monitoring and research are increasingly available.(3) There have been increasing efforts and improved understanding of biosynthesis pathways of algal toxins.(4) On top of the sustained ecological and oceanographic research of HABs,research of modern omics and molecular mechanisms has advanced significantly.However,the key environmental triggers and biological (particularly biochemical and molecular) mechanisms remain elusive,with no available triggering factor for predicting HAB outbreaks.The shortcoming is because HAB formation is a complex ecological process,which is likely species-specific and ecosystem-specific on the one hand,and because HAB research still falls short of integrated,comprehensive,and systematic manner on the other hand.We propose that in the future,more efforts should be invested in integrative,comprehensive,and systematic approach on key representative HAB species,similar to the research on model organisms in life science.This requires a combination of laboratory experiments on cultured species,mesocosm experiments on multi-species communities,and natural plankton assemblages,and in the meantime technological integration of modern omics,traditional physioecology,and real-time in situ monitoring.