The Yellow Sea (YS) and East China Sea (ECS) have the world’s largest supply of floating macroalgae. The golden tides (Sargassum horneri) appear mainly in the YS and ECS, but become entangled as they drift. The floating harmful macroalgae blooms (HMBs) obstructs navigation and is a huge socioeconomic problem in the vicinity of coastal areas. However, the annual pattern of Sargassum bloom is not well known due to changing air-sea interaction conditions. To determine the spatio-temporal distribution and variation of the golden tide in the YS and ECS, the multi-satellite sensor data (e.g. Sentinel-2 and GOCI) was used to detect the floating macroalgae patch using the Alternative Floating Algae Index and mapped over the study area using a 15-year data. The floating patches detected by both satellite data were overlapped to make the annual pattern maps. The Sargassum blooms were generally found on spring in the YS and ECS. The Sargassum blooms was proceeded in the waters near the Yangtze River and Zhejiang Province, China and then floating into the east and north-east ward influenced by the Tsushima warm current or Kuroshio. The Sargassum blooms were build-up in the middle of the ECS and pile-up in the coast of Korea from March to May. Recently, the Sargassum blooms were temporally expanded from to May from 2019 to 2022 and spatially raised in the YS and ECS. The initiated drifting blooms were detected in the Bohai Bay and Shandong Peninsula from September to October and then expanded in a southward direction from the central YS to Jeju Island, Korea during November to March. The blooms lasted 5-6 months in the YS and ECS. The second onset blooms were found near the mouth of the Yangtze River and Zhejiang Province from January to February and expanded in an east- or north-ward direction from March to May (or June). From the annual pattern maps of the golden tide blooms, we suggested two origins with tracing the temporal and spatial distribution and development. The first blooms were onset on fall around the Bohai Bay and/or Shandong Peninsula and southward controlled by the local wind and sea surface temperature condition on winter. The second blooms were initiated on winter near the Zhejiang Province, China and east- and northward affected by the local current and wind condition.

Primary Presenter: Young Baek Son, Korea Institute of Ocean Science and Technology(KIOST) (sonyb@kiost.ac.kr)

Authors:

Jong-Kuk Choi, Korea Institute of Ocean Science and Technolgoy(KIOST)  (jkchoi@kiost.ac.kr)