The Distribution And Seasonal Evolution Of Sea Surface PCO₂between Spring And Summer In Jiaozhou Bay

In recent years, the problems of carbon sources/sinks in continental margins seabecome a hot research of scholars from various countries. As the most obvious area ofinteraction of terrestrial and marine ecosystems, bays and estuaries are naturallybecome one of the focus of global carbon cycle researches. Especially the bays whereare more obvious influenced by human action, the characteristics of CO₂source/sink are universal in nature to the research of CO₂flux in shelf sea, and then thevariety are more extreme. In addition, data of higher-resolution in time and space areeasy access to facilitate the discussion of the mechanism, research of the CO₂source/sink on the bay is very active in recent years. This paper based on three cruises fieldsurvey of Jiaozhou Bay of March2011, May2010and August2008and take theunderway measured pCO₂data, combined with synchronous observations ofhydrological, chemical and biological elements, analyzed the surface seawater pCO₂distribution and seasonal evolution in Jiaozhou Bay and estimated the air-sea CO₂Flux, discussed the impact factors of the pCO₂distribution and seasonal evolution,such as temperature, degradation of organic matter and phytoplankton activities inJiaozhou Bay.The study results show that: In March, Jiaozhou Bay shown the strong sink ofair-CO₂.Temperature has little influence on the distribution of surface waters pCO₂ofJiaozhou Bay and the impact of organic matter degradation on pCO₂also can benegligible. Phytoplankton activity is a major impact factor of pCO₂distribution,which couse the sink of air-CO₂in Jiaozhou Bay.In spring（May）, the average of pCO₂is558μatm, show the source of air-CO₂inthe whole area. From the incubation experiments, we can see that the degradation oforganic matter plays a control role in the distribution of pCO₂, high aerobicrespiration rate to maintain a high pCO₂. The total primary productivity calculated through black-and-white bottle，primary productivity estimated by chlorophyll a andthe relationship of DO%with pCO₂show that the phytoplankton plays an essentialrole for the distribution of pCO₂. The degradation of organic matter, together with theactivity of phytoplankton affect the distribution of pCO₂in surface water of theJiaozhou bay in spring.In summer, average of pCO₂is487μatm, significantly lower than the spring,show the source of air-CO₂in the whole area, but little weaker than that in spring. Thedegradation of organic matter, together with the activity of phytoplankton affect thedistribution of pCO₂in surface water of the Jiaozhou bay. The contribution of organicmatter degradation is the primary cause of the result. The gross primary productivitycalculated by black-and-white bottle and dissolved oxygen saturation data show that,in summer phytoplankton activities play a control role for the weaker pCO₂sourcethan spring.In the seasonal evolution of pCO₂distribution, we use the calculation method ofTakahashi （1993） and Takahashi et al （2002） to calculate the impact of temperatureand biological activity （including the degradation of organic matter and phytoplanktonactivity） on seasonal evolution of pCO₂, the results show that temperature andbiological activity common control the seasonal evolution of surface seawater pCO₂of Jiaozhou Bay. From winter to spring, the contribution of temperature to pCO₂isgreater than biological activity; From spring to summer, biological activity effect isgreater than the temperature.The paper uses Wanninkhof （1992） and grid statistical method to estimate thethree months carbon fluxes of Jiaozhou Bay. The results show that CO₂source/sinkshow a significant seasonal variation in Jiaozhou Bay: in March, the Bay overallperformance as strong air-CO₂sink,and manifested as a source of air-CO₂in Spring.InSummer the Bay also shows as air-CO₂source, but the strength of the source isweaker than Spring, even shows as sink in Bay central because of strong biologicalactivity.