Research On The Tianjin Coastal Plankton Ecosystem Biophysical Model

With the rapid development of the social economy, continuous exploitation of the coastal area has given a great pressure on the coastal ecosystem. Especially, in recent years, lots of big projects such as land reclamation and port construction have been implemented in many coastal area. These projects influenced the coastal ecosystem seriously. Ecological dynamic model is an efficient method to quantitatively study the evolution mechanism of the coastal ecosystem and to forecast the important variation characteristics of the system. Therefore, such modeling studies of the coastal ecosystem may be of value in further understanding the influence of coastal constructions on the coastal ecosystem. Further more, the prediction results from these models can be used to guide proper exploitation and utilization of the coastal resources, and to reduce the negative influence from coastal construction on the coastal ecosystem. Thus, it could serve as a powerful tool for the management and sustainable exploitation of the national ocean resources.This dissertation mainly concerns the influencing characteristics of coastal constructions on the coastal ecosystem, such as increased concentrations of the suspended matters, nutrient salts (nitrogen and phosphorus), and petroleum hydrocarbon. Based on a deep analysis of the ecosystem structure and its variation characteristics in Tianjin coastal waters, a bio-physical coupled model was proposed to evaluate the influence of coastal constructions on the coastal ecosystems.(1) Based on the monitoring results of nitrogen, phosphorus from 1996 to 2006 in Tianjin coastal waters, the concentration of DIN, DIP continuously increased from 1996 and reached its maximum value in 2004, then it began to decrease. Spatial variation analysis showed that the means of DIN and DIP concentrations have a similar space distribution pattern, decreasing from coastal waters to sea basin and from the north to the south. Different correlation coefficients were got for DIN and DIP concentrations at different seasons. The correlation coefficients followed the order:wet period> flow period> dry season. From 1990s to recent years, the community structure, dominant species composition, biomass of phytoplankton and zooplankton had changed a lot.(2) Based on the structure and variation characteristics of the coastal water ecosystem, a pelagic ecosystem dynamical model was proposed using phytoplankton (diatoms and dinoflagellate), zooplankton, nutrient (phosphate, ammonia, nitrate nitrogen) and detritus as system variables.According to the influencing characteristics of coastal constructions on the coastal ecosystem, the solution of such model was given. Compared with the observation data, the result of model test is satisfactory and can be used as a good indicator for the yearly change trend of the plankton ecosystem in the coastal area. Moreover, the influence of coastal projects on pelagic ecosystems was also studied based on this model.(3) By using of the one-way grid inlay technique,the hydrodynamic characteristics of Bohai Sea were calculated. To simulate the hydrodynamic characteristics of coastal waters in Tianjin, the temperature, salinity, velocity and water level was interpolated to obtain the open boundary conditions of Tianjin coastal waters. Compared with the measured data, the hydrodynamic model can be used to simulate the tidal current characteristics of Tianjin Bohai coastal region, and also provide an accurate physical field for the biogeochemical processes. According to the coastal ecosystem dynamic model, a coupled biophysical model of coastal ecosystem was established and used to simulate the seasonal variation and spatial distribution of the main biogenic elements in the Bohai Bay, and satisfactory results were obtained.