Carbon cycling processes and carbon fixed by organisms in China marginal seas

Abstract

In the paper,carbon cycling processes and carbon fixed by organisms in China marginal seas are reviewed.The carbon cycling processes include CO2 fluxes between atmosphere and seawater,carbon biological pump process,carbon sink/release in par-ticulates and carbon transfer in fishing/culture.China marginal sea is a sink area of CO2 in the air,but some coastal parts are source areas such as the Jiaozhou Bay and the Changjiang estuary.The mean annual sink strength of atmospheric CO2 in China marginal seas is about 30 million ton carbon per year.The source/sink strength is controlled by sea surface temperature(SST),phytoplankton production and seawater mixing process in different sea-regions and seasons.The amount of fixed carbon by phytoplankton is about 6.39×108 t/a in China marginal seas,in which 65.3% carbon is fixed in spring and summer.The carbon fixation ability of the South China Sea is about 4.16×108 t/a,which is double of that in Bohai Sea,the Yellow Sea and the East China Sea.Fishing and culture can increase carbon sink strength.In recent years,the yield of large-size economic seaweeds in China marginal seas is about 1.20–1.50 ×106 t/a,so their fixed carbon is about 4.0 ×105 t/a.If the seaweed yield amount increase by 5% every year in China marginal seas,carbon fixed amount of the large-sized economic seaweeds may reach to 9.3 ×105 t/a up to 2020.Therefore,algae breeding is an important technique for increasing marine carbon sink with multi-values.To reveal the fishing/culture eco-environment,establish the method for grading the carbon sink of fishing/culture and study the recycling period of fishing/culture carbon sink are very important in the future.