渤、黄海颗粒有机碳空间分布及交换通量的季节性变化

Seasonal variations and exchange fluxes of particulate organic carbon in the Bohai Sea and Yellow Sea

海洋是地球上最大的碳库,对大气中的CO_(2)起着调控作用,在减缓全球变暖过程中起着重要作用。渤、黄海是典型的封闭-半封闭型陆架海,深入探讨渤、黄海颗粒有机碳(POC)变化特征和输运通量,对区域碳循环和海洋碳通量研究具有重要意义。通过2010年春秋两季、2016年夏季和2012年冬季渤、黄海的大面积实测数据,结合MODIS卫星遥感影像反演的叶绿素a(Chl-a),探讨了渤、黄海POC空间分布、影响因素、碳库及交换通量的季节性差异。结果表明:春季POC浓度最高,平均浓度0.34 mg/L;夏季次之,平均浓度0.30 mg/L;秋季平均浓度0.27 mg/L;冬季最低,平均浓度0.17 mg/L。不同季节POC空间分布基本一致,整体呈现“近岸高、离岸低,表层低、底层高”的特点,高值区主要位于黄河三角洲、山东半岛东侧和苏北浅滩-长江口北附近水域,低值区主要集中在南黄海中部深水区。不同季节影响POC分布的因素不同,春、秋两季受径流输入、沉积物再悬浮和浮游植物共同影响,夏季主要受控于浮游植物初级生产,沉积物再悬浮是影响冬季POC分布的主要原因。渤、黄海POC碳库呈明显的季节性变化,春季碳库最高,渤海与黄海分别为1.32×10^(6)t和6.71×10^(6)t;冬季碳库最低,渤海与黄海分别为7.21×10^(5)t和3.39×10^(6)t。约有6.55×10^(5) t/a POC通过渤海海峡由渤海进入黄海,POC输运主要集中在夏季。

The ocean is the largest carbon reservoir on Earth and plays an important role in mitigating global warming by regulating the amount of CO_(2) in the atmosphere. The Bohai Sea and Yellow Sea are typical semi-enclosed continental shelf marginal seas in China. Therefore, an in-depth study of the characteristics of particulate organic carbon(POC) changes and transport fluxes in the Bohai Sea and Yellow Sea is of great significance to understand carbon cycling and ocean carbon flux. The seasonal variations in spatial distribution and carbon pools of POC in the Bohai Sea and Yellow Sea were studied based on the measured data of different seasons from 2010to 2016. Results show that the concentration of POC was the highest in spring on average of 0.34 mg/L, while it was 0.30 mg/L in summer, 0.27 mg/L in autumn, and 0.17 mg/L in winter. The spatial distribution of POC in different seasons showed the same pattern. The concentration of POC was higher in the nearshore, lower in the offshore area, and the highest in the bottom layer. The areas with higher concentrations were mainly located near the Huanghe(Yellow) River Delta, the nearshore area off the east coast of the Shandong Peninsula, and the area near the northern Jiangsu Shoal in the north of the Changjiang(Yangtze) River estuary. The lower concentration areas were mainly concentrated in the deepwater area of the central part of the South Yellow Sea. The factors affecting the distribution of POC varied in season. In spring and fall, runoff input, sediment resuspension, and phytoplankton metabolism dominated the distribution of POC;in summer, the spatial distribution of POC was mainly controlled by the primary production of phytoplankton;and in winter, the main factor was the resuspension of sediments. In addition, POC carbon pools of the Bohai Sea and Yellow Sea showed significant seasonal variations,with the highest reserves in spring, being 1.32×10^(6) t and 6.71×10^(6) t in the Bohai Sea and Yellow Sea, and the lowest in winter for 7.21×10^(5) t and 3.39×10^(6) t, in the Bohai Sea and Yellow Sea, respectively. About 6.55×10^(5) t POC entered into the Yellow Sea from the Bohai Sea through the Bohai Strait every year and mainly concentrated in summer.