Northern East China Sea Nutrient Distribution And Influencing Factors

Because of the large number of population, the contradiction between population growth and the reduction of arable land have become increasingly prominent. Offshore development and utilization of biological resources related to food safety in China. Understanding and knowing our coastal ecosystem services, the key to the process of food production and sustainable mechanism, healthy, sustained development and utilization of coastal resources and environment, not only to promote the sustained development of the boost can not be ignored, but also provide an important guarantee of food safety in China.Nutrients are the major biogenic material of marine ecosystem is the most important marine primary productivity factor, is the key elements of study the marine ecosystem. There are much water sources in northern East China Sea. Such as off northeastern Taiwan's ocean currents, the Taiwan Warm Current, the Yangtze diluted water, the Yellow low-salt, the West Korea coastal current and the Kuroshio and so on. Different water sources interactions cause complex and changing hydrological environment in this pool. So that the area has long been popular with marine and fisheries research attention.Cold vortex is usually cyclonic vortex, the cold eddy region usually presented upwelling, upwelling and cold vortex complement each other to form a cold vortex - upwelling system. Lower layer nutrient can be brought to the upper by upwelling. So there is a potential fishery. At the same time, eddy center's sea surface is lower than the surrounding. In this study, the East China Sea circulation in the previous review, nutrient research based on three databases, there are NOAA, NGDC, TOPEX / POSEIDON databases. Analyzed the marine environment by the techniques of plotting and numerical analysis of MATLAB. By studying nutrients'spatial and temporal changes in the northern of East China Sea to analyze the distribution of nutrients, sea surface topography and the cold vortex - upwelling system relations. We found that:I. Nutrient distribution in the northern of East China Sea:Firstly, the general characters of Nitrate and Phosphate distribution in the northern East China Sea are similar; their concentrations in the northwest of the study area are higher than that in the southeast, decrease from the near shore to offshore, increase from the surface to the bottom. The maximum of Silicate also is in the Northwest of the area, but there is a sub-maximum concentration in the Northeast. Secondly, the nutrients concentration increased with depth in all seasons; there is not any nutrient cline. The average concentrations of nutrients in the surface are the highest in winter; Nitrate in the 50 ~ 150 meters layer and Silicate in the 50 ~ 200 meters layer are the highest in summer; there are weak changes in the bottom during four seasons, of which 400 ~ 500m layer Phosphate, Silicate concentration is larger in autumn. Finally there are high-nutrient closed contours in four seasons, which is high-nutrient water mass. The high-Nitrate nutrition water masse′s center moves from the south to the north-east, then the west, and finally to the southeast. This center moves within 125~128°E, 29~31°N in four seasons. There is also a cycle of change in intensity, the strongest is in winter, the weakest is in summer; high - Phosphate nutrient center locates on 125.5°E, 30.5°N, and Silicate locates on 128.5°E, 30.5°N.II. The northern of East China Sea surface topography features:(1) There are different intensities of high and low sea-level closed contour in every week. Among them, significantly lower sea level closed contour in winter and spring.(2) Seasonal sea surface topography presents unique characteristics:①The sea surface topography of northwest is higher than southeast in autumn and winter.②On the contrary, higher in southeast in spring.③Sea surface topography being high during the summer in across the research region.(3) Mean sea level diagram shows that there are four types'sea-level features.①The first was southwest - northeast direction, northwest and southeast of the high, middle low.②The second was southwest - northeast direction to northwest, southeast high.③The third was the South - North to the east and west, high, middle low.④The fourth was the South - North to the west higher than the east.(4) The study area of low sea-level closed contour, is also a region of high nutrient salt mass, centre of the cold eddy in southwest of Cheju Island; the low closed contour center in the northern of East China Sea the center and the high nutrient salt movement with cold vortex center close.III. The main ways of affect the distribution nutrients in the northern of East China Sea:Horizontal transport, vertical mixing, atmospheric deposition, including the Yangtze River and other surface runoff, the Taiwan warm current, Kuroshio frontal eddy, upwelling, sediment - water interface exchange atmospheric deposition. Circulation systems are an important factor that affects the distribution of nutrients and sea surface topography in the area. Nutrient distribution, sea surface topography and the cold eddy - upwelling systems have a close relationship among the three:(1) The cold eddy - upwelling system in southwest of Cheju Island bring a lot of nutrients from the bottom to the top. Nutrients concentrate in the region and form a high-nutrient mass.(2) Temperature of the cold eddy region is lower than surrounding water. Water specific volume is small. So the sea level is usually lower than the surrounding waters. The cold vortex center has a low-lying closed contour in year-round, especially in winter and spring.