Climate-adaptive flocculant design: Mechanistic advances and operational challenges for harmful algal blooms control

Global climate change is exacerbating the occurrence of harmful algal blooms (HABs) through rising temperatures, extreme climate events, and eutrophication. Conversely, HABs amplify climate impacts by degrading marine carbon sinks and emitting greenhouse gas during decomposition, thereby forming a positive feedback loop that accelerates ecological destabilization. Flocculation technology, a widely used mitigation strategy, faces challenges under climate-stressed water chemistry, as conventional eco-friendly flocculants lack dynamic adaptability. The bidirectional amplification of global climate change and HABs necessitates advanced flocculants. This work aims to propose a roadmap for developing flocculants that disrupt the climate-HABs cycle while aligning with marine sustainability goals. Firstly, the mutual amplification mechanism between global climate change and HABs, driven by warming, acidification, and hydrological extremes is analyzed. Additionally, the effects of physiological traits of typical harmful microalgae on flocculation are elucidated. Conventional eco-friendly flocculants, various impact factors and indices for assessing the flocculation efficiency are briefly discussed. Finally, design principles, mechanic innovation, practicalities, limitations, and challenges for the development of climate-resilient flocculants are systematically discussed. This work establishes a framework to disrupt the climate deterioration-HABs outbreaks-carbon sink degradation feedback loop, thereby enabling a transformative shift in HABs governance from reactive mitigation strategies toward proactive, climate-adaptive prevention and control measures.