| The North Yellow Sea(NYS) is a semi-enclosed sea, which surrounded by Shandong Peninsula, Liaodong Peninsula and the Korean peninsula. It's also a material and energy exchange linkage of the Bohai Sea and South Yellow Sea(SYS). A number of water masses exist at different seasons in this area, as well as more complex coastal currents are the main factors of the complexity and uniqueness in NYS's biogenic elements seasonal distribution. In recent years, many of the studies aimed at seasonal changes, horizontal and vertical distributions of biogenic elements are mainly in SYS. The studies in the NYS are more concentrated in the coastal waters, while the studies for the whole NYS'biogenic elements distributions are less. The nutrient concentrations and nutrient structure of the North Yellow Sea Cold water mass(Yc) and the it's contribution to the NYS'researches are still blank. In this paper, based on the four cruises carried out from July 2006 to October 2007 in the NYS(Winter: in Jan; Spring: from Apr to May; Summer: from Jul to Aug; Autumn: in Oct), the hydrological and chemical properties'distributions in spatial and seasonal of NYS are discussed. According to temperature and salinity data, the water masses in four seasons in the NYS are divided, and the chemical properties in different water masses are discussed. Then the nutrient structure of every season in NYS are analyzed. In summer, the contribution of nutrients in the Yc are calculated. Conclusions are summarized as follows:⑴The water vertical mixed strongly in winter, stratified gradually in spring and then a stable thermocline formed in summer, till autumn the stratification weaken and disappear finally. Accordantly, the biogenic elements in water follow the process of "mixed evenly– stratification– mixed evenly". The nutrients are higher in autumn and winter, while lower in spring and summer. DO concentration influenced by water temperature and biological activity, so it's performance higher concentration in winter and spring, lower in summer and autumn. From the plane distribution, under the central area is the high-value areas of nutrients in four seasons, while the distributions have different characteristics in upper water in four seasons. The concentration of DO has opposite change with nutrients.⑵From winter to autumn, the NYS can be divided into 4, 7, 5, 5 water masses respectively. During spring to autumn, the nutrient concentrations of Yc are higher, especially in autumn, it's became the highest value of entire area. After the disappearance of the thermocline in winter, the higher content of PO4-P in Yc play a significant role in upgrade the concentration in the whole area.⑶Through the analysis of each water mass'nutrient structures in the four seasons in this area , find that the N/P and Si/P are the lowest in Yc from spring to autumn. So in autumn and winter, it's possible that the entire NYS'nutrient structures are affected by the Yc. The content of PO4-P is raised, and then ensure that the phytoplankton growth well and reproduction in spring.⑷Though the Yc with only 23.7% of the total volume of NYS, it's contribution of PO4-P, DIN and SiO3-Si can reach 54.7%, 38.8% and 29.5% respectively. And the contribute to PO4-P is the highest. Therefore, the disappearance of the thermocline induce the strong vertical mixing, and then high level nutrients are bringing from bottom to the surface, enhancing the nutrient concentrations in the whole NYS, and also improving the nutrient structures in NYS.
|
PDF Full Text Request