Evidence of improvements in the water quality of coastal areas around China

Abstract

Coastal areas are huge carbon stores and hotspots for marine carbon fixation. Changes in the water quality of coastal areas are closely linked to their carbon fixation function. In this study, monitoring data were analyzed to identify how the water quality in China's coastal areas changed from 2001 to 2020. The results showed that the water quality in the coastal areas had improved gradually since 2001. The proportion of water quality in Class II and above gradually increased from 41.4% in 2001 to 77.4% in 2020, meanwhile, the proportion of water quality less than Class II, decreased from 58.6% to 22.6%, respectively. Of the four sea areas, the water quality was best in the Yellow Sea, and was poor in the East China Sea. The water quality varied between the different coastal provinces and cities and was good in coastal areas of Hainan, Guangxi, Shandong, and other provinces and cities, but was poor in Shanghai, Zhejiang, and Tianjin. Terrestrial anthropogenic pollutants were the main influence on the water quality in the coastal areas. As a hotspot for fixing blue carbon, the continuous improvement of the water quality of coastal areas laid a foundation for the health of the blue carbon ecosystems.

Keywords: Coastal areas; Marine ecosystems; Reclamation; Terrestrial anthropogenic pollutants; Water quality.