Evaluation of the Role of Self-cleaning Capacity on Marine Environmental Carrying Capacity: A Case of Ganh Rai Bay, Vietnam

Economic activities are constantly increasing in the southern key economic region (SKER), especially in Ho Chi Minh City (HCMC), which leads to the influx of large amounts of wastewater from this region into Ganh Rai Bay (GRB). The problem of assessing the marine environmental carrying capacity (MECC) of coastal areas is urgent, and the role of self-cleaning must be elucidated. Four typical pollution parameters were selected: ammonium (NH 4 + ), biological oxygen demand (BOD), phosphate (PO 4 3− ), and coliforms. The study aims to propose a framework to assess the impact of the role of self-cleaning on MECC and to apply the proposed framework to GRB as a case study. A series of models were used to simulate hydrodynamics, and an advection–diffusion model with an ecological parameter set was used for water quality modelling. The land–ocean interactions in the coastal zone model were used to calculate the GRB and East Sea retention time. Finally, a multiple linear regression model was used to clarify the relationship between the MECC and self-cleaning factors. Calculation results show that the self-cleaning factor increased the MECC Ammonium by 60.30% in the dry season and 22.75% in the wet season; similar to MECC BOD , MECC Phosphate increased by 5.26%, 0.21% (dry season), and 11.04%, 0.72% (wet season), respectively. MECCC Coliforms in the dry season increased by 14.83%; in the wet season, MECC Coliforms doubled. The results provide medium-and long-term solutions to improve the water quality of the GRB, especially the selection of activities that conserve the ecological system and improve the self-cleaning capacity of the bay.