Spatio-temporal Evolution Characteristics of Red Tide in Coastal Guangdong over the Past 45 Years

The frequent occurrence of red tide disasters has caused severe ecological, resource and environmental challenges for coastal nations, resulting in substantial economic losses. With the advancement of marine "Blue Granary" initiatives, mitigating red tide hazards and safeguarding marine ecosystems have become increasingly urgent. This study compiles red tide records from 1980 to 2024 coastal Guangdong, analyzes their spatio-temporal distribution using Geographic Information Systems (GIS). Key findings followed certain patterns: Red tides in coastal Guangdong exhibit both perennial and seasonal characteristics, with peak occurrences in spring. The annual frequency shows a fluctuating upward trend, while the cumulative annual affected area varies significantly. Distinct phased variations are observed across decades: low frequency in the 1980s, increased occurrence from the 1990s, and peak levels during the first decade of the 21st century. High-frequency areas include the Pearl River Estuary, Mirs Bay, Daya Bay, the coastal Zhanjiang in western Guangdong and the coastal Chaoshan in eastern Guangdong.The top four red tide species by occurrence frequency are Noctiluca scintillans, Phaeocystis globosa, Akashiwo sanguinea and Skeletonema costatum. By analyzing data spanning a broader time frame and incorporating the latest information, this study reveals the distribution patterns of red tide in coastal Guangdong. It provides scientific support for the operational work of red tide forecasting and, consequently, offers reference for government departments in disaster prevention and mitigation.