The Study On The Response Of Phytoplankton Growth To The Physical Processes In Changjiang Estuary And Min-Zhe Coastal Waters

Phytoplankton, as the main primary produce of marine ecosystem, sustains the nutrient transfer and energy flow in the sea areas, the number of whose biomass determines the performance of aquaculture and the status of aquatic ecological environment in the areas. In recent years, it is the rapid development of economy in our country, especially in the coastal areas, that brings serious burdens to the aquatic environment, which has attracts the attention of scientists. The Changjiang Estuary and Min-Zhe coastal waters is one important pieces of China Sea where the water is seriously eutrophication, the algae blooms frequently and the aquatic ecological environment is threatened. The phytoplankton dynamic study in the Changjiang Estuary and Min-Zhe coastal waters has important significance to the study on the nutrient transfer and energy flow, and further on the external environmental and physical mechanism of the algae blooms and the restoration of the aquatic ecological environment.The Hydrodynamics condition in the Changjiang Estuary and Min-Zhe coastal waters is complex and varies seasonally. The key physical processes such as Changjiang diluted water and the seasonal shelf circulation and wind jointly influence the distribution of temperature and nutrient as well as the characteristics of current, which further influences the marine primary productivity. For all this, based on the already built high-resolution, three-dimensional, physics-biogeochemistry coupling numerical model that considers multiple key physical processes such as the runoff, tide, shelf circulation and seasonal wind, this article simulated the growth process of two kinds of phytoplankton including diatoms and dinoflagellates, and furthermore, the article analyzed the influences of those key physical processes on the spatial and temporal distribution of the phytoplankton biomass. In general, the model simulation results of phytoplankton have good characteristics of horizontal and vertical distribution, which has some credibility.The growth of phytoplankton is mainly controlled by the temperature, light intensity and nutrient concentration. In this paper, through analyzing the characteristics of temperature, light condition and nutrient distribution in the Changjiang Estuary and Min-Zhe coastal waters during the time from April to September, the spatial and temporal distribution of two kinds of phytoplankton including diatoms and dinoflagellates is given. From the temporal point of view, the diatoms bloom twice in spring and summer while the dinoflagellates bloom only once in spring; From the spatial point of view, the phytoplankton biomass mainly concentrates around the east area of 30 to 50 isobaths. Because of the light limitation caused by high turbidity in the Changjiang Estuary and Hangzhou Bay and the nutrient limitation caused by oligotrophication in the east of Taiwan Island and Kuroshio waters, where there is no significant phytoplankton growth. In addition, affected by the seasonal variation of temperature and nutrient concentration, the phytoplankton has different characteristics of spatial and temporal distribution in different seasons.Furthermore, by setting numerical trials changing the quantity of runoff, the quantity of shelf circulation and the monsoon conditions to analyze the variation of temperature and nutrient concentration caused by the various key physical processes changes, the biomass variation of two kinds of phytoplankton including diatoms and dinoflagellates is given. The results show that all those key physical processes changes have certain influences on the phytoplankton biomass. Changing the quantity of shelf circulation has the most influence, then the monsoon conditions, the quantity of runoff influences least.