Spatiotemporal dynamics of nearshore red tides and their carbon sink potential in the East China Sea, 2012–2021

Abstract

ABSTRACT The East China Sea frequently experiences red tide outbreaks, significantly impacting marine carbon sink dynamics and ecosystem health. This study examines the temporal and spatial variations of red tide events in the East China Sea 2012 -2021, utilizing MODIS remote sensing imagery with a focus on summer outbreaks. Using the Two-Step algorithm, we assess surface particle organic carbon (POC) levels in red tide-affected areas, providing crucial insights into the carbon sink potential and distribution patterns of phytoplankton. Key findings include: (1) The largest red tide outbreak area occurred in 2015, with substantial fluctuations observed along the Zhejiang coast compared to the more stable Yangtze River estuary, especially in 2018 and 2020. (2) Surface POC concentrations reached their peak at 404.37 g m−3 in the Yangtze River estuary in 2021 and 359.83 g m−3 along the Zhejiang coast in 2017, with the lowest values recorded in 2013 and 2015. (3) Spatially, The distribution of severe algal bloom and higher concentrations of POC are observed along the coastal areas of the Yangtze River estuary and Zhejiang-Fujian, but with different causes. These findings highlight the importance of red tide events in regional carbon dynamics and their role in achieving sustainable development goals.