Development of Nakdong River Estuary Ecosystem Model Using AQUATOX Model

Abstract

Objectives:In this study, a model representing the ecosystem of the Nakdong River Estuary was constructed using the AQUATOX model, and the ecosystem model was calibrated using the measured data, and the Nakdong River Estuary ecosystem was predicted by using the calibrated model.Methods:After constructing the Nakdong River Estuary Ecosystem Model using the AQUATOX model provided by the US EPA, the model was calibrated using the measurement data for the Nakdong River Estuary. The model calibration was performed on the measured chlorophyll-a, and the DO, total nitrogen, total phosphorus, crab, shrimp, and fish measurement data were compared with the values ​​derived from the calibrated model and verified. Using the final verified model, we predicted the ecosystem change that occurs when the pesticide component (0.4 ug/L) is temporarily and continuously introduced into the Nakdong estuary area from the upper stream of the Nakdong River.Results and Discussion:The calibration results of the ecosystem model for the measured chlorophyll-a were RB (0.029), F (1.35), RSME (0.489), and MAE (0.105). The phytoplankton in the estuary consisted of cryptomonas, greens, diatoms, blue-green algae, and the cryptomonas grew in the estuary as a habitat, but the rest of the phytoplankton were introduced into the estuary through the effluent of Nakdong river. In the case of zooplankton, copepods are the dominant species, but all of them are found to be released into the ocean when the effluent from Nakdong river is introduced. In the case of crustaceans, crab and shrimp were the dominant species, and the values ​​of these models were similar to the results of previous studies, and in the case of fish, the dominant species were found to be Toadfish and Croaker. Using the validated model, we predicted the transient or continuous inflow of herbicide components from the effluent of Hagut-duk, but phytoplankton and invertebrates decreased in both inflow situations. Exceptionally, copepods were not affected by the two inflow situations, and crabs continued to increase during temporary inflow conditions except for the initial stagnation period. All fish died in the continuous inflow situation, but in the temporary inflow situation, the Croaker increased and the Toadfish decreased.Conclusions:The implementation of the Nakdong River Estuary ecosystem as an AQUATOX model was the first attempt in Korea. Through this study, a plan to predict various environmental changes that may occur in the future was prepared. It was confirmed that the introduction of herbicides suggested as an example of environmental change can have a fatal effect on the estuary ecosystem even in small amounts, and the foundation for ecosystem changes and future countermeasures to various environmental changes in the future was established.