Simulation Analysis Of Seasonal And Inteannual Variation Of Phytoplankton Community Structure In The Yellow And East China Sea

As the marginal sea in the Northeast Pacific Ocean,the Yellow Sea and East China Sea is a representative marine ecosystem.In recent years,Influenced by human activities,the nitrogen and phosphorus in the river are excess,which leads to the increasing degree of pollution in the coastal area of sea of China.The marine ecological disasters occurred frequently and the ecological structure becomes unbalanced in the Yellow Sea and East China Sea.The phytoplankton is the primary producer of the marine ecosystem,its population fluctuation and structure could influence the function and structure of marine ecosystem directly,so it is important to study the structure of phytoplankton community.The marine ecosystem model can understand the characteristics of system function,and fill in the blank of the measured data.It is based on physical,chemical and biological processes in basic rules,with the help of computer quantitative simulation of the interaction mechanism of the process.In this paper,NEMURO(North Pacific Ecosystem Model for Understanding Regional Oceanography)is used to study the distribution of phytoplankton community and the mechanism.The spatial distribution of seasonal variation and the interannual variation of the phytoplankton biomass is analysed,the influence mechanism of the seasonal variation and interannual variation is discussed intensively.The seasonal distribution of chlorophyll a has obvious variation,In spring and summer chlorophyll a is higher than that in autumn and winter,In March chlorophyll a start to appear high value in the middle area of the Yellow Sea,In May chlorophyll a start to appear high value in Changjiang Estuary,at this time chlorophyll a reached 4 u molN/L in the middle area of the Yellow Sea and in Changjiang Estuary.PS and PL have the same seasonal variation as chlorophyll a.Through analysing the relationship between chlorophyll a and nutrient seasonal spatial distribution,we found that chlorophyll a and N/P ratio shows strong positive correlation in twelve month in Changjiang Estuary,due to Yangtze River diluted fresh water.Performance in the middle of South Yellow Sea showed positive correlation in cold half year and negative correlation in warm half year,due to the impact of rising and consumption of the thermocline in the middle of South Yellow Sea.Analysing the interannual variation of chlorophyll a,In Changjiang Estuary,chlorophyll a shows a increasing trend,and in the middle of South Yellow Sea and in the East China Sea shelf area,chlorophyll a shows slightly decreasing trend,In the west coast of Yellow Sea,the changes of chlorophyll a is not obvious.In Changjiang Estuary,the chlorophyll a is mainly influenced by the Yangtze River runoff and the shift of the Yangtze River runoff,Yangtze River runoff brings rich nutrient,which makes rapid growth of chlorophyll a,the interannual variation of chlorophyll a has a cycle of 3 years.In the west coast of Yellow Sea,the chlorophyll a is affected by light and nutrient,and is mainly affected by light,the interannual variation of chlorophyll a exists a cycle of 2.5 years.In the middle of South Yellow Sea,chlorophyll a is influenced by light(mixed layer)and nutrient,and is mainly affected by nutrient,the interannual variation of chlorophyll a exists a cycle of 2.5 and 4 years.In the East China Sea shelf area,the chlorophyll a is affected by temperature and nutrient,and is mainly affected by nutrient,the interannual variation of chlorophyll a exists a cycle of 3 years.The range of seasonal variation is much greater than that of the interannual variation.The range of the seasonal variation in inshore waters is higher than that in offshore waters.The main reason is that the water depth is shallow in inshore waters,and the seasonal variation of temperature,light and land runoff is obvious.The range of interannual variation in Changjiang Estuary,southwest of the Yellow Sea and the coastal areas of Zhejiang and Fujian is higher than that in other areas,the main reason is due to the flux and flow direction of the Yangtze River Runoff.