Dynamic causes contribute to the increasing trend of red tides in the East China Sea during 2020 to 2022

Red tide is a marine phenomenon caused by the excessive growth of microscopic algae in the ocean. This study aims to analyze the development trend of red tides in the past 20 years and the dynamic external causes that induce red tides based on existing satellite remote sensing and numerical simulation data. And the changes in dominant species of red tides in different seasons are analyzed. The results show that within the week before the red tide occurs, the temperature fluctuates significantly, with an average temperature increase of 1.42°C, while the change in salinity is relatively small. Meanwhile, ocean fronts are areas in the ocean where different water masses meet and form boundaries. The average strength of ocean fronts increased by 3.7%. The increase in ocean front strength indicates enhanced ocean mixing over a short period of time. Under the combined influence of these factors, the probability of a red tide outbreak in the East China Sea increases within a short period of time. This article has important reference value for further research on the causes of red tides and their response to ocean dynamic changes.