Haizhou Bay is an open bay located in northern Jiangsu Province, China. This study analyzes the changes in the coastline, coastal development, and water quality of Haizhou Bay between 2006 and 2016. The box model method and numerical simulation are adopted to calculate the environmental capacities of Haizhou Bay in 2006 and 2016, analyze changes to environmental capacity features, and assess the influencing factors over this period. The scenario analysis method is used to discuss the influencing mechanism and degree of influence of factors (e.g., the water quality difference inside and outside the bay, and sea reclamation) on the environmental capacity and calculate the contribution of each influencing factor. The changes in terrain triggered by sea reclamation and water quality from 2006 to 2016 reduced the total environmental capacity of Haizhou Bay, with an influencing ratio of 0.198:0.802. In other words, poorer water quality inside the bay reduces the environmental capacity by a degree of 4.05 times that of sea reclamation. This study can offer guidance on related future research aiming to protect the marine environment of Haizhou Bay and control the total amount of pollutants discharged into the sea.

To calculate the environmental capacity of the estuaries of Haizhou Bay in northern Jiangsu, China in 2006 and 2016, this study employed the share ratio approach and established a tidal hydrodynamic model and a water quality diffusion model by the Delft 3D software to perform the numerical simulation. The article compared the environmental capacity in 2006 and 2016, and analyzed the changes between these years. The scenario analysis method was used to explore the influence of factors on the environmental capacity and quantify the contribution of each influencing factor. The results show that the theoretical environmental capacity was reduced by 32.718 tons/day (28.56%) from 114.571 tons/day in 2006 to 81.853 tons/day in 2016. The remaining environmental capacity was reduced by 6.955 tons/day (56.92%) from 12.219 tons/day in 2006 to 5.264 tons/day in 2016. The changes in topography and the amount of runoff into the ocean through the estuaries of Haizhou Bay between 2006 and 2016 reduced the total environmental capacity of the estuaries by an influence ratio of 0.363:0.637. The study will provide the management of the marine environment of Haizhou Bay with information to control the aggregate pollutants flowing into the ocean and support the social and economic sustainable development of Haizhou Bay.