Dynamics Of Carbonate And Nutrients And Ocean Acidification In The Changjiang Estuary And Adjacent East China Sea

The atmospheric CO2 concentration is increasing.The ocean is an important sink of the atmospheric CO2.However,another environmental problem ocuur as a result of the oceaic CO2 sink-ocean acidification.The East China Sea is the largest shelf sea in the North Pacific.It has large river inputs,which stimulates the water dynamics and primary production.This thesis is based on the carbonate and nutrient data collected in the area of the Changjiang estuary and East China Sea shelf in August 2015,February 2016,December 2015 and August 2016.In the inner Changjiang estuary,dissolved inorganic carbon(DIC),total alkalinity(TA)and nitrogen nutrients are mainly influenced by sedwage discharge,with had higher values bear the southern bank.In the outher estuary,DIC and nutrients was mainly dominated by conservative mixing in winter.However,the biological uptake of DIC and nutrients are conspicuous in the outer estuary in summer.The net community production(NCP)was estimated to be 77.3±24.8 mmol C m-2 d-1.The uptake ratio of C/N(6.6)was very close to the Redfield ratio.The high productivity increased pH and aragonite saturation state index in index by 0.23～0.37 and 1.0-2.2,respectively.On the East China Sea shelf,the water in winter was mainly dominated by the conservative mixing of Yellow Sea water,Chiangjiang diluted water and East Sea off shore water.However,in summer,there was another scenario.The water was stratified.In surface water,the photosynthesis resulted strong DIC and butrients removal.However,strong remineralization resulted in DIC and nutrients addition and hypoxia.In the surface water,the NCP was estimated to be 59.9±16.7 mmol C m-2 d-1 at the surface.The photosynthesis increased pH and Ωar by 0.2 and 1.3,respectively.In the bottom water,DIC increased 104.6～176.9 μmol kg-1 accomponied by hypoxia.The C/O ratio in the remineralization was 0.77±0.08,close the the redfield ratio.The decrease in pH and aragonite saturation state index was 0.3 and 1.6,respectively.By the end of this century,the pH in the bottom water will decrease by 0.3 and the water will be "corrosive" for aragonite.Actions should be taken to relief the status.