Where does floating Sargassum in the East China Sea come from?

Lin Qi; Peng Cheng; Menghua Wang; Chuanmin Hu; Yuyuan Xie; Keyu Mao

doi:10.1016/j.hal.2023.102523

Where does floating Sargassum in the East China Sea come from?

Harmful Algae. 2023 Nov:129:102523. doi: 10.1016/j.hal.2023.102523. Epub 2023 Oct 10.

Authors

Lin Qi¹, Peng Cheng², Menghua Wang³, Chuanmin Hu⁴, Yuyuan Xie⁴, Keyu Mao⁴

Affiliations

¹ NOAA Center for Satellite Applications and Research, College Park, MD 20740, USA; Global Science & Technology Inc., Greenbelt, MD 20770, USA. Electronic address: lin.qi@noaa.gov.
² State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen 361102, China.
³ NOAA Center for Satellite Applications and Research, College Park, MD 20740, USA.
⁴ College of Marine Science, University of South Florida, St. Petersburg, FL 33701, USA.

PMID: 37951622
DOI: 10.1016/j.hal.2023.102523

Abstract

Floating macroalgae of Sargassum horneri (S. horneri) in the East China Sea (ECS) has increased in recent years, with ocean warming being one of the driving factors. Yet their possible origins, based on a literature review, are unclear. Here, using multi-sensor high-resolution remote sensing data and numerical experiments for the period of 2015-2023, we show two possible origins of the ECS floating S. horneri, one being local near the Zhejiang coast with initiation in January-February and the other being remote (> 800 km from the first) in the Bohai Sea with initiation in June-November. While their drifting pathways are revealed in the sequential remote sensing imagery, numerical experiments suggest that S. horneri from the remote origin (Bohai Sea) can hardly meander through the strong Yangtze River frontal zone, which may serve as a "wall" to prevent trespassing of surface floating seaweed to the south of the frontal zone, where S. horneri has a local origin. PLAIN LANGUAGE SUMMARY: Sargassum horneri (S. horneri) is a brown macroalgae (seaweed) abundant in surface waters of the East China Sea (ECS), which can serve as a moving habitat, but can also cause major beaching events and environmental problems. Knowledge of its origins is important to help implement mitigation strategies and understand possible ecological impacts along its drifting pathways. Using high-resolution remote sensing images and numerical experiments, we track floating S. horneri in space and time between 2015 and 2023. Two possible origins are identified, one being far away from the ECS and the other being local, both of which are known to have benthic S. horneri. The study also reveals how S. horneri are transported from their source regions resulting in large-scale distributions previously observed in medium-resolution satellite imagery.

Keywords: Aquaculture; Bohai Sea; East China Sea; Global warming; MODIS; MSI; ROMS; Remote sensing; Sargassum horneri; Sentinel-2; VIIRS; Yellow Sea.

Publication types

Review
Research Support, Non-U.S. Gov't

MeSH terms

China
Ecosystem
Sargassum*
Seaweed*