The Distribution Of Nutrients And Phytoplankton Biomass In North China Sea

Bohai Sea and Yellow Sea are important parts of China's continental shelf sea,as important CO2 "sinking" area,which have higher primary productivity.The growth and reproduction of phytoplankton rely on nutrients,whose levels and structure have significant effects on community structure and abundance of phytoplankton in the ocean.Studying on spatial and temporal distribution,sources and influenced factors of nutrients and phytoplankton biomass in the area can provide data for the China Sea phytoplankton carbon cycling studies,setting polices of reducing CO2 emissions and marine fisheries resources.This subject,Bohai Sea and Yellow Sea as research objects,relies on National Natural Science foundation of China voyage on survey areas of nutrients and chlorophyll a for sampling.Through combined hydrological parameters(temperature,salinity and water masses),it analyses spatial-temporal distribution features of nutrients and chlorophyll a,and discusses relationship of nutrients and chlorophyll a.Hope that this study can provide a basis for marine environmental research in the area.This thesis,based on analyses of surveying data in Bohai Sea and Yellow Sea in three voyages of April-May 2014,November 2014 and August-September 2015,having the following main conclusions:(1)DIP and DIN concentrations of surface and DCM layer of Bohai Sea and Yellow Sea have the same trends:inshore areas are higher than offshore areas.The maximum value occurred in adjacent areas of Yellow River and Changjiang River,which have significant terrestrial input influence.But high values of DIP and DIN of bottom layer appear in the central areas of North and South Yellow Sea.The distribution of DSi is different from DIP and DIN in the surface and DCM layer.High values of DSi appear in the Central area of South Yellow Sea in spring,but in the Central area of Bohai Sea in summer and autumn.The DSi distribution of bottom layer lines with DIP and DIN trends,whose higher values were found in the central area of North and South Yellow Sea.(2)From nutrients threshold that,Bohai Sea and Yellow Sea are mainly limited to the absolute limitation of DIP,although the absolute limitation of DIN and DSi is regional.It can be seen from nutrients structure,that Bohai Sea and Yellow Sea almost have not DIN relative limitation,and the relative limitation of DSi is regional.The relative limitation of Bohai Sea and Yellow Sea was controlled by DIP.(3)Chlorophyll a shows significant seasonal variations in Bohai Sea and Yellow Sea:inshore areas are higher than offshore areas.The maximum value of Chlorophyll a occurs in Yellow River and Luanhe River estuary and eastern part of North Yellow Sea in Spring;although it occurs in the region of near the Changjiang River of southern Yellow Sea in summer;and in adjacent areas of Shandong peninsula and West Korea Bay in autumn.(4)Worthy of note is,temperature and salinity characteristics of vertical distribution at section B and C show low temperature and high salinity cold water mass in central area Yellow Sea.It began to develop in spring,mostly obvious in summer and drop offin autumn.Cold water mass of Yellow Sea has good storage function with DIP,DIN and DSi.DIP,DIN and DSi concentrations of bottom layer were higher.Due to obvious stratification,nutrients of bottom layer cannot be up to surface layer,which resulting in phytoplankton biomass have not higher value with cold water mass of Yellow Sea.This phenomenon is most pronounced in summer.(5)On the relationship between environmental factors and chlorophyll a,Bohai zone is affect by riverine inputs such as Yellow River,influx of waters from Yellow Sea through the Bohai Strait and bacterial activity.Yellow Sea coastal zone consistent with position of western Yellow Sea coastal currents,whose water have low nutrients.Its chlorophyll a with DIP,DSi and NO3-have negative related relationship in spring and autumn.In summer,chlorophyll a with temperature,salinity,and nutrients are not related,its may related to trend of North by monsoon effect in surface layer.Yellow Sea cold water mass controling zone have more significant with storaging DIP,DSi,NO3-.Nutrients are exhausted by phytoplankton in surface and middle layer and have not supplement from bottom layer.Although water of bottom layer has higher nutrient concentrations,limited by light,phytoplankton have unable to grow at the bottom.(6)Because of the depth shallow,B67 station,continuous observation station,whose temperature and salinity haven't obvious stratification phenomenon.Besides surface layer,temperature have regularly fluctuating.Salinity doesn't change significantly over time.The concentration of DIP is absolute limitation.Due to water mixing uniform,with depth vary,the changes of concentration of DIN and DSi is smaller.Time with high values of concentration of DIN and DSi coincide with low values of temperature.It presumably associated with input of Yellow River.Nutrient structure,vertical changes is surface layer>bottom layer>middle layer.Numerically,DIP have relative limitation at all layers.