Developments and prospects of modified clay for mitigating harmful algal blooms

With the intensification of global climate change and human activities, the frequent occurrence of harmful algal blooms (HABs) poses threats to aquaculture, coastal tourism, and other industries. The demand for HAB mitigation has shifted from algal removal to multifunctional approaches including algal removal, toxin reduction, and eco-environmental regulation. As an efficient and environmentally friendly method for HAB mitigation, the modified clay (MC) technology has made significant progress in theory, technological innovation, and standardized application in recent years. This paper systematically reviews the new developments in MC technology. In terms of surface modification, advanced methods such as functional group grafting modification and microbial composite modification have been developed to address organic matter-rich waters and multiple mitigation demands. The former significantly enhances flocculation efficiency against high-density, pico-sized HAB species and resistance to organic matter interference through organic quaternization and organic-inorganic composite strategies; the latter achieves multiple effects of "algicidal-toxin reduction" and "algal removal-water purification" by combining specific functional microorganisms. Regarding application standardization, a numerical model of the dosage-effectiveness relationship for MC has been established, providing a quantitative basis for the standardized field application of MC technology and forming standards that support large-scale applications. In addition, this paper introduces the eco-environmental regulation effects of this technology in intensive pond aquaculture (IPA), and its effects on the quality and yield of cultured organisms. Successful field practices in countries such as Turkey and Malaysia are also presented, offering references for integrated HAB prevention and control globally.