Spatial-Temporal Distribution of Golden Tide Based on High-Resolution Satellite Remote Sensing in the South Yellow Sea

A new marine ecological disaster called the golden tide occurred in the Southern Yellow Sea at the end of 2016. This disaster damaged the Porphyra yezoensis aquaculture in the Jiangsu Shoal, causing a direct economic loss of nearly 500 million CNY. The floating brown macroalgae in the golden tide was identified as Sargassum horneri, which have been frequently growing in coastal waters in recent years. Effectively detecting this golden tide using traditional satellites is difficult because of the small patches or slicks of bloom. This study used multi-source and high-resolution satellite data to identify the floating Sargassum with a maximum multispectral resolution of 4 m (GF-2). Satellite and in-situ spectral data were used to analyze the spectral characteristics of the Sargassum and compare them with those of Ulva. Both sets of spectral characteristics exhibited the "red-edge" effect, and the difference was obvious between the green and red bands. Combined with the normalized difference vegetation index algorithm, monitoring and backtracking were performed for the golden tide disaster. Results show that the golden tide originated from the Rongcheng-Haiyang sea area of the Shandong peninsula and drifted to the south and westward. In early December 2016, Sargassum affected the sea area of Yancheng in Jiangsu Province. In late December 2016, it arrived at the Jiangsu Shoal and finally entered the Yangtze River estuary around mid-January 2017. The drifting path was mainly controlled by wind vector products. A comprehensive analysis of environmental factors showed that the sea surface temperature and chlorophyll-a in the South Yellow Sea were higher than normal during the golden tide disaster, which may be attributed to the rapid growth of the Sargassum biomass. Therefore, this study hypothesizes that an internal cause exists between the golden tide and the abovementioned factors