Analysis of the status and development trends of red tides in China’s offshore waters from 2015 to 2024

Based on national monitoring data from 2015 to 2024, this study examines red tides in China’s offshore waters and compares them with trends from 1995 to 2014. Key findings show 513 recorded red tide events affecting 58919 km2, with peak occurrence in spring and summer—though large-scale events also appeared in autumn and winter. Major red tide-prone areas were the Yangtze Estuary to northern Fujian, Pearl River Estuary, and western Bohai Sea. Among 80 identified red tide species, dinoflagellates and diatoms dominated. Compared to the previous 20 years, overall red tide characteristics remained similar, yet three trends emerged: (1) The peak season and average event duration extended; (2) Dinoflagellate red tides increased from 50% to 66.28%; (3) Toxic red tides have spread geographically, including events caused by non-native species. To address these challenges, we recommend optimizing integrated monitoring and early-warning systems, advancing unmanned monitoring equipment, improving rapid detection technologies, and enhancing emergency response capabilities to strengthen preparedness for red tide disasters.