三沙湾盐田港海水养殖海域海-气界面CO_2交换通量的时空变化

Seasonal variation of sea-air CO_2 flux in mariculture area in Yantian Harbor,Sansha Bay

根据2012年11月和2013年2、5、8月对福建三沙湾盐田港养殖海域进行4个季节调查获得的pH、总碱度(TA)、表层水温、盐度、溶氧和溶解无机碳(DIC)以及叶绿素a等基础数据,估算该区域表层海水溶解无机碳体系各分量的浓度、pCO_2和海-气界面CO_2交换通量,并对影响因素进行分析。结果表明,盐田港表层海水4个季节的DIC、HCO_3^-、CO_3^(2-)和CO_2浓度分别为955~1 957.08、905.08~1 848.13、10.14~124.78和11.48~39.78μmol/L,不同季节之间差异极显著(P<0.01)。盐田港表层海水中的pCO_2在一年中的变化范围为391.27~1 200.49μatm,海-气界面CO_2交换通量全年的范围为0.25~6.93μmol/(m^2·d),表现为大气CO_2的弱源。盐田港海-气界面CO_2交换通量不同季节的差异极显著(P<0.01),在不同站位之间的差异显著(P<0.05)。秋、春季的碳通量最高,夏季碳通量最低,冬季显著低于秋季,但与春季差异不显著。分析表明,水文要素和生物要素等是影响盐田港表层海水中p CO_2和海-气界面CO_2交换通量的重要生态因子,其中,大型海藻的栽培活动有利于该养殖海域对大气CO_2的吸收。

Based on the investigation data of p H,total alkalinity（ TA）,sea surface temperature（ SST）,salinity（ S）,dissolved oxygen（ DO）,dissolved inorganic carbon（ DIC）,Chl. a,etc. during four cruises from November 2012 to August 2013,the spatial and seasonal variations of dissolved inorganic carbon system parameters and aqueous pCO_2 were investigated in a large-scale mariculture area in Yantian Harbor,Sansha Bay. And the sea-air CO2 flux was also evaluated. The results showed that the annual concentration of DIC,HCO_3^-,CO_3^（2-）and CO_2 was in the range of 955- 1957. 08,905. 08- 1848. 13,10. 14- 124. 78 and 11. 48-39. 78 μmol / L,respectively. There were significant differences between seasons in concentrations of DIC,HCO_3^-,CO_3^（2-）and CO_2（ P〈0. 01）. The annual value of aqueous p CO_2 was in the range of 391. 27- 1 200.49μatm,and sea- air CO_2 flux was in the range of 0. 252- 6. 925 μmol /（ m^2·d）. These demonstrated that the Yantian Harbor was the weak source of atmospheric CO_2. There was significant difference for sea-air CO_2 between different sampling sites（ P〈0. 05）,and highly significant difference between different seasons（ P〈0. 01）. The sea-air CO_2 flux was the highest in autumn and spring,and was the lowest in summer. The seaair CO_2 flux in winter was lower than that in autumn,but there was no significant difference with that in spring. The sea-air CO_2 flux was lower in the bay mouth than that in the upstream sea area in autumn,spring and winter. Distribution of pCO_2 and sea-air CO_2 flux were mainly controlled by hydrological conditions and biological uptake in Yantian Harbor. The large-scale seaweed aquaculture is helpful diffusion of CO_2 across the sea-air interface.