Remote sensing monitoring and trend analysis of Chl-a changes in cultured fish ponds in the Greater Bay Area from 2013 to 2022

The Guangdong-Hong Kong-Macao Greater Bay Area (GBA) is one of the most economically developed and active regions in China. Fish pond farming is the most important aquaculture model in the GBA. In recent years, climate change and the continuous interference of human activities have led to Chl-a content There are significant differences in time and space, and timely monitoring is crucial to protecting the ecosystems of inland water bodies and adjacent sea areas. Most previous studies have focused on inland lakes or adjacent sea areas, and there have been few studies on fish ponds in the GBA. Based on the BST model, this study selected Landsat image data from 2013 to 2022 to invert the Chl-a concentration of cultured fish ponds in the GBA, and analyzed the temporal and spatial differences in Chl-a contained in cultured fish ponds in the GBA. The results show that: (1) The BST model performs well in retrieving Chl-a concentration in cultured fish ponds in the GBA.(2) In the past ten years, Chl-a has declined year by year from 2013 to 2018, fluctuated slightly from 2018 to 2020, and continued to rise from 2020 to 2022. (3) Aquaculture fish ponds are mainly distributed in the central and southern areas of the GBA. Aquaculture fish ponds near the Pearl River Basin are denser and have higher concentrations. (4) Chl-a has shown an overall upward trend in the past ten years. Among them, the aquaculture fish ponds in Dongguan and Zhongshan have the largest upward trend. Dongguan has the highest increase rate and Guangzhou has the lowest increase rate. (5) Chl-a in cultured fish ponds in the GBA has obvious seasonal variation characteristics, with the highest value in summer and the lowest value in winter. Chl-a concentration in the four seasons is highly correlated with water temperature. Changes in water temperature may be the main factor causing this phenomenon. (6) The concentration of Chl-a in the water bodies of fish farming ponds in the GBA is significantly higher than that of the Pearl River water body and sea water, and the Pearl River water body near the shore is higher than that in the center of the river. This may be due to human overuse of feed and disinfectants Caused. Increasing human activities have caused a significant increase in the degree of eutrophication of water bodies in farmed fish ponds. Control of nutrients such as N and P produced by human activities should be strengthened. The results of this study are important references for water body protection in the GBA and the sustainable development of the aquaculture industry value.