The Distribution And Influence Factors Of Organic Carbon In The Bohai Sea And Yellow Sea Of 2010

As an important part of the global carbon cycle, ocean organic carbon cycle is closely related to the various links of matter and energy flow in the marine ecological system. The Bohai Sea and Yellow Sea step across different latitudes, the terrestrial inputs, oceanic circulation and structure of the ecological system are major different, so the deep analysis of the distributions, transportions, transformations and the control mechanism of dissolved organic carbon(DOC) and particulate organic carbon(POC) is of great significance to understand the ocean organic carbon cycle in the offshore. In this paper, based on the two cruises carried out in the spring and autumn in 2010 in the Bohai Sea and Yellow Sea, the concentration, distributions and influence factors of DOC and POC were discussed, while in the cold water mass of the Yellow Sea which has typical hydrology and ecological environment, the distribution and control mechanism of DOC and POC were mainly studied. Conclusions were summarized as follows:(1) In spring and autumn of 2010, the horizontal distribution of DOC and POC in the Bohai Sea and Yellow Sea overall shows that: the concentration of DOC and POC is generally higher in the north and the coastal water area, lower in the south and offshore; In vertical distribution, it is higher in upper layer than that in the middle layer, but it is increased at the bottom layer, also it is higher in spring than in autumn.(2) In spring, the concentration of DOC is ranged from 2.01 to 4.71mg/L in the Bohai Sea and ranged from 0.96 to 4.25mg/L in the Yellow Sea, while the average concentration separately is 2.64±0.50mg/L and 2.12±0.58mg/L. The highest DOC content is mainly found in the coastal water of the western of Bohai Sea, Shandong peninsula and the northeast of Yangtze River Estuary, which is mainly affected by the terrestrial inputs and coastal current, and the low DOC value is found in the central of south Yellow Sea which is mainly controlled by the dilution of low DOC current from the East China Sea. In autumn, the concentration of DOC is ranged from 1.51 to 3.00mg/L in the Bohai Sea and ranged from 0.96 to 2.51mg/L in the Yellow Sea, while the average concentration separately is 2.19±0.28mg/L and 1.58±0.29mg/L. Separately influenced by the phytoplankton and terrestrial inputs, the high DOC value appears in the middle of the Laizhou Bay and the coastal of Shandong peninsula, and the low DOC value is also found in the central of south Yellow Sea, at the same time, it is also low in the northeast of Yangtze River Estuary. In sections, the distribution of DOC is higher in the coastal water and surface which is affected by terrestrial inputs, but in the offshore it is decreasing form the surface to the bottom, which is because that the field production of phytoplankton is restricted.(3) In spring, the concentration of POC is ranged from 251.47 to 1268.00μg/L in the Bohai Sea and ranged from 78.11 to 9189.90μg/L in the Yellow Sea, while the average concentration separately is 530.40±186.62μg/L and 413.59±794.23μg/L. The high POC value appears in the Huanghe Estuary and north of Jiangsu Province, the low POC value is found in the central of south Yellow Sea. In autumn, the concentration of POC is ranged from 35.00 to 1229.33μg/L in the Bohai Sea and ranged from 49.08 to 2741.93μg/L in the Yellow Sea, while the average concentration separately is 347.96±238.31μg/L and 302.26±349.85μg/L. In the Bohai Sea, the high POC value is found in the Bohai Bay and the middle of the Bohai Channel, also the concentration of POC is higher in the northeast of Yangtze River Estuary at the bottom layer. The horizontal distribution and the vertical change of POC both are in connection with terrestrial inputs, the field production of phytoplankton and sediment resuspension. In the coastal water, the high POC value is found and it is uniform in the vertical distribution, which is mainly affected by the terrestrial inputs and the sediment resuspension; but in the offshore, it is lower and the vertical distribution is different, which is contoraled by the field production of phytoplankton.(4) In autumn, the cold water mass is clearly found below thirthy meters in the north and south Yellow Sea, which shows low temperature, high salt and high nutrient; also mainly affected by the water stratification and temperature, the DOC and Chlorophyll-a concent are lower. The average concentration of DOC and POC in the south cold water mass separately is 1.41±0.21mg/L and 148.42±66.17μg/L, while in the north cold water mass, the average concentration of DOC and POC is 1.65±0.23mg/L and 183.37±132.70μg/L. The concentration of DOC and POC in the cold water mass is decreasing with depth except for the bottom layer, the surface is mainly affected by the field production of phytoplankton.