Effects Of Nutrients On Phytoplankton Growth And Its Dynamics Study In Mesocosm Experiments In Changjiang River Estuary And Its Adjacent Area

With the development of economy and the increasing influence by human activities, marine pollution tends more serious than ever before. In the East China Sea (ESC), with eutrophication extent aggravates and eutrophication area expands,harmful algae blooms (HABs) occurr frequently in this region, especially in Changjiang River estuary and its adjacent area. These all do harm to the economic development and marine breed aquatics, even the health of human beings. To understand the effects of compositions and structures of nutrients on the phytoplankton growth and feed back mechanism from phytoplankton to nutrients, the two mesocosm experiments are conducted during and after the HAB occurrence in the ESC. In this paper, the influence of nutrients on phytoplankton growth is discussed and the constants of uptake/release rates of PO4-P and NO3-N by phytoplankton are calculated according to a uptake/release dynamics model. Main research work and conclusions are listed as follows:1 Effects of nutrients in different concentrations on Phytoplankton growth in the course of HABThe increase of phosphate (PO4-P) concentration in sea water has great promotions on phytoplankton growth. In particular, the influence on the growth of phytoplankton is more obvious by increasing the concentration of NO3-N in the sea water with richer PO4-P. NO3-N is the mainly nitrogen source by phytoplankton in the experiments. The growth of phytoplankton is not consistent with the absorption of PO4-P by phytoplankton .The phytoplankton would continue to grow even if the PO4-P in the water has been used up. It shows that phytoplankton can store PO4-P in the cells during the experiments.The variation of nutrients concentration and structure has a closely relationship with the growth of phytoplankton in the mesocosm experiments.The phytoplankton grow best when N/P ratio in the water is about 12~18. The N/P ratio in the...