Dynamic causes contribute to the increasing trend of red tides in the east China sea during 2020–2022.

Red tide is a marine phenomenon caused by the excessive growth of microscopic algae in the ocean. This study aims to analyze the development trends 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 significant temperature fluctuations within the week before the red tide occurs, with an average increase of 1.42 °C. In contrast, 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%, indicating 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 rapidly. Therefore, this study has important reference value for further research on the causes of red tides and their response to ocean dynamic changes. • Study analyzes 20-year trend of red tides and their dynamic causes. • Before a red tide, average temperature rises by 1.42 °C; salinity changes little. • Increased ocean front strength by 3.7% boosts East China Sea red tide risk. [ABSTRACT FROM AUTHOR]