Nutrient-based method for assessing the hazard degree of red tide a case study in the Zhejiang coastal waters, East China Sea

The assessment of the hazard degree of red tide is a new research field. The current study analyzes the relationship between the specific growth rate and N/P atomic ratio of red tide to obtain the assessment results of red tide under various N/P atomic ratios. This study aims to develop a nutrient-based method that can assess the hazard degree of red tide disasters based on the algal growth and cell density threshold of red tide outbreaks. This study obtained the following four main findings: (1) a nutrient-based tolerance model of the algal growth that can provide a quantitative description of Shelford’s law of tolerance was established, (2) a method that can assess the hazard degree of red tide disasters based on the time the algal growth reached the cell density threshold of red tide outbreaks was proposed, (3) the hazard degree assessment of red tide disasters was classified into four grades, namely, very high, high, medium, and low, and (4) the spatial distribution map of the Alexandrium tamarense red tide outbreak probability in the Zhejiang coastal waters was generated using the proposed method and the geographic information system and remote sensing technology.