资源环境科技发展态势分析平台

A floating algae bloom in the East China Sea was observed in Moderate Resolution Imaging Spectroradiometer (MODIS) imagery in May 2017. Using satellite imagery from MODIS, Visible Infrared Imaging Radiometer Suite, Geostationary Ocean Color Imager, and Ocean Land Imager, and combined with numerical particle tracing experiments and laboratory experiments, we examined the history of this bloom as well as similar blooms in previous years and attempted to trace the bloom source and identify the algae type. Results suggest that one bloom origin is offshore Zhejiang coast where algae slicks have appeared in satellite imagery almost every February-March since 2012. Following the Kuroshio Current and Taiwan Warm Current, these "initial" algae slicks are first transported to the northeast to reach South Korea (Jeju Island) and Japan coastal waters (up to 135 degrees E) by early April 2017, and then transported to the northwest to enter the Yellow Sea by the end of April. The transport pathway covers an area known to be rich in Sargassum horneri, and spectral analysis suggests that most of the algae slicks may contain large amount of S. horneri. The bloom covers a water area of similar to 160,000 km(2) with pure algae coverage of similar to 530 km(2), which exceeds the size of most Ulva blooms that occur every May-July in the Yellow Sea. While blooms of smaller size also occurred in previous years and especially in 2015, the 2017 bloom is hypothesized to be a result of record-high water temperature, increased light availability, and continuous expansion of Porphyra aquaculture along the East China Sea coast.

Plain Language Summary A massive floating algae bloom in the East China Sea was first captured in Moderate Resolution Imaging Spectroradiometer satellite imagery in mid-May 2017. Both its size and location are unprecedented. Several means have been used to identify the algae type and bloom origin, including the use of multisource satellite imagery, numerical particle tracing experiments, and laboratory experiments. While multiple origins are possible, the bloom could be tracked to Zhejiang coastal waters where the "initial" algae slicks back in February were transported to the northeast following the Kuroshio Current and Taiwan Warm Current to reach South Korea (Jeju Island) and Japan coastal waters by early April 2017, and then transported to the northwest to enter the Yellow Sea by end of April. Spectral analysis and historical field surveys suggested that the bloom may be dominated by Sargassum horneri, while expanded seaweed aquaculture and record-high water temperature and increased surface light may have contributed to the unprecedented bloom, which covered a water area of similar to 160,000 km(2) with pure algae coverage of similar to 530 km(2), both exceeding the maximum size of most Ulva blooms in the Yellow Sea.