||Coastal lagoon is tend to encounter some impact of disturbance especially in rainfall events. During the heavy rain, the nutrients may transport from landside to lagoon by inflow. The abundance of nutrients may caused ecosystem loss of balance.|
Dapeng Bay is located in southwestern Taiwan, which is an enclosed shallow coastal lagoon. Recently Dapeng Bay is developing into an international tourist and recreation area by Tourism Bureau, MOTC. In order to study the water quality and ecosystem impact after the develoment projects, we established a high resolution 3-D FEM numerical water dynamical model by using unstructured grids, and the model is not only coupled with biology states variables but also using on case studies. Wet and dry seasons are clear seasonal phenomena in southern Taiwan. Heavy rainfall has significant influence on the salinity of surface water, local effects near the two discharges would bring high concentration of nutrients to the territorial water.Therefore, this study is based on the long term observation data. Assuming silicon and phosphorus nutrients are adequate supply, we added both tidal circulation and meteorological factors to simulated the nitrogen base biology simulation.
The results show that Dapeng Bay is a nutrients excess area. After we calculated the model results of fluxes of phytoplankton carbon and compared the results to eutrophication standard defined by Nixon, we discovered that the water body of Dapeng Bay has already become eutrophic in the early spring, and it even have phenomena of hypertrophication after the heavy rainfall events.
The biological model simulation results are summarized and analyzed that although tidal inlets dredging project and strong wind stress help to improve the water circulation of Dapeng Bay, but the nutrients fluxes of model results show that a large influx of nutrients would still accumulate in Dapeng Bay during the rainfall events.