Hazard Zoning of Harmful Algal Bloom Disasters in Zhejiang Coastal Waters Using GIS: 1933-2021.

The coastal waters of Zhejiang Province in China experience a high incidence of harmful algal blooms (HABs). It is therefore important to carry out hazard zoning to prevent and mitigate these HAB disasters. According to the historical record data of HAB disasters from 1933 to 2021, the frequency, duration, area and algal toxicity of HAB occurrences can be used as evaluation indicators. A method for hazard zoning of HAB disasters and a method for verifying the rationality of the zoning results are proposed. The hazard zoning results of HAB disasters in the coastal waters of Zhejiang from 1933 to 2021 (H1933-2021) show that very-high hazard degree areas of coastal waters of Zhejiang Province were found in Shengshan waters, the eastern waters of Zhujiajian and Nanji Islands' waters. Due to the influence of marine environmental factors, the spatial distribution of hazard degree of HAB disasters is dynamic, so it is recommended that the hazard zoning of HAB disasters be carried out once every five years. The rationality of the zoning results from 2017 to 2021 is verified, showing that the hazard zoning method of HAB disasters proposed in this study has a good rationality and credibility. This study utilized a qualitative approach to visually identify the spatial distribution of hazard degree zoning of HAB disasters in the Zhejiang Province coastal waters over the last 88 years. This has provided useful information to help prevent and mitigate HAB disasters and guide mariculture and coastal tourism planning. [ABSTRACT FROM AUTHOR]