Extraction and interannual variation analysis of algal bloom-prone zones in the adjacent waters of the Yangtze River Estuary in summer based on GOCI data

• Published in: Journal of marine systems Vol. 245; p. 103989
• Main Authors: Zhao, Kexin, Zhao, Qian, Li, Hu, Xi, Yanbin
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2024
• Subjects: Chl-a; Correlation; GOCI; Harmful algal blooms; Prone zones; Yangtze River Estuary; Yangtze River Estuary; Harmful algal blooms; Correlation; Chl-a; Prone zones; GOCI
• ISSN: 0924-7963; 1879-1573
• DOI: 10.1016/j.jmarsys.2024.103989

Harmful algal blooms (HABs) frequently threaten the health of marine environments and ecosystems in the adjacent waters of the Yangtze River Estuary (YRE) in summer. To better understand the spatiotemporal distribution, variation characteristics, and major influencing factors of algal bloom-prone zones in the adjacent waters of the YRE in summer, the present study used Geostationary Ocean Color Imager (GOCI) chlorophyll-a (Chl-a) data from 2011 to 2020. The Chl-a concentration threshold for summer algal blooms in the adjacent waters of the YRE was determined to be 16 mg/m3, based on which the monthly and interannual distribution characteristics of algal blooms were further clarified, and the influence of runoff and sea surface temperature (SST) on algal blooms was analyzed. The results showed that the area of the algal bloom-prone zones was the largest in July, at 1337 km2, which was approximately 2.8-fold greater than that in June (474 km2) and 1.3-fold greater than that in August (1028 km2); the algal bloom-prone zones were mainly distributed in the eastern sea area of the YRE, and the spatial distribution of the algal blooms showed significant interannual variation. In 2020, the distribution range of the algal bloom-prone zones was the largest, and the maximum probability was >20%. Runoff had a significant positive effect on the algal bloom index (BI) (r = 0.89, p < 0.05), the correlation between BI and SST was weak (r = 0.50, p = 0.14), and the algal bloom probability had a significant negative correlation with SST (r = −0.71, p < 0.05), implying that above a certain range of temperatures, algal growth rates may decrease with increasing temperature. The research results can provide a scientific basis for the early prevention, control, and emergency response of disasters, which is conducive to the sustainable and healthy development of marine resources and has significant scientific and management significance. •Chlorophyll-a concentration threshold method can be used to identify algal blooms.•The area of algal bloom-prone zones in the YRE is the largest in July in summer.•Spatial distribution of algal blooms shows significant interannual variability.•Yangtze River runoff has a significant positive effect on the bloom intensity.•Temperature has a significant negative effect on the algal bloom probability.