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 (NH4+), biological oxygen demand (BOD), phosphate (PO43-), 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 MECCAmmonium by 60.30% in the dry season and 22.75% in the wet season; similar to MECCBOD, MECCPhosphate increased by 5.26%, 0.21% (dry season), and 11.04%, 0.72% (wet season), respectively. MECCCColiforms in the dry season increased by 14.83%; in the wet season, MECCColiforms 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.

Assessing marine environmental carrying capacity in semi-enclosed coastal areas - Models and related databases.

Faced with the degradation of the marine environment, the Joint Group of Experts on the Scientific Aspects of Marine Pollution (GESEMP) first presented the concept of marine environmental carrying capacity (MECC) in 1986, which confirmed that there is a need to pay attention to physical, chemical, biological, and biochemical processes, thereby indirectly suggesting the need for a modelling approach. Although studies on MECC have been published, further research is necessary and must be complemented by a new approach. In this study, an integrated system called SECAMECC (Marine Environmental Carrying Capacity Semi Enclosed for Coastal Areas) for semi-enclosed bays is proposed. SECAMECC comprises database of seven data groups and four models: 3D hydrodynamic, ecological, retention time estimation, and MECC calculation. The proposed system has been applied to a specific semi-enclosed bay as a case study to determine the MECC seasonally. The carrying capacities of ammonium (NH4+), phosphate, total suspended solids (TSS), and biological oxygen demand were assessed in accordance with the baseline and forecast scenarios. The received results show that under the baseline, MECC no longer accepted PO43-; meanwhile, NH4+, TSS, and BOD5 exhibited the following values in the dry and wet season, respectively: 1134 and 3514 (t/m); 110,578 and 144,458 (t/m); and 17,072 and 44,348 (t/m). Owing to the hydrodynamic factors, the carrying capacity in the dry season is always greater than that in the wet season. Furthermore, the relationship between MECC and environmental standards, current water quality, and hydrodynamic factors was clarified.