The East China Sea Kuroshio Nutrient On The International Changes And Its Influencing Factors Of Research

Nutrients are the important chemical substances in the marineecosystem, the most important nutritional element for the growth ofmarine organisms, and also the basis of the marine primary productionprocess and the ocean food chain. Because of the infect ofbiochemistry and hydrological elements, the distribution andproportion of the nutrients in ocean is not uniform and with significantmonthly change. Nutrients involved in the whole process of the lifeactivities of marine organisms, the relationship between nutrients andhydrological factors, the spatial distribution and process of change innutrients content and the limitation could affect on regional marineprimary productivity, then affecting the stability of marine ecosystemsand marine fisheries development.With the strengthening of human activities, coastal areas and rapideconomic development has brought tremendous pressure to thecoastal ecosystems. By the injection of the land runoff, urban sewageand industrial wastewater discharges, the nutrient content of coastalwaters continued to rise and destroyed the ecological balance ofcoastal waters. The most serious status is in East China Sea, biologicalresources of the coastal ecosystems is increasingly unable to meethuman demand for resources.In order to improve the proportion of deep-sea fishing and meetthe needs of the marine resources, the research in offshore marineecosystem and the development of fishery resources become thefocus attention of scientific and technical personnel. The Kuroshioregion in East China Sea which is rich region of fisheries resources, so theresearch on nutrients in this area relates to the sustainable developmentof China’s marine fisheries.This paper use the Nutrients World Ocean Atlas2009issued by NOAA in2010and topography data issued by NGDC to building thenutrients3D database of Kuroshio in East China Sea, by extract thecharacteristics section, eigenvalue, and numerical statistical to analysisthe monthly change of nutrient content, nutrient proportion andnutrient limitation in Kuroshio East China Sea.The results show that:(1) Nutrients concentrations increased from the surface to the deep,the change of concentration has different characteristics betweenupper of250m and deeper of250m. The average concentration of DINand P is basically the same. In upper250m, the maximumconcentration is in May and June, the minimum concentration is in Julyand August. In deeper250m, the maximum concentration is in Octoberto December, the minimum concentration is in July to October.Average concentration of Si is different from DIN and P, in upper250m,the maximum concentration of Si is in May to July, the minimumconcentration is in November and December. In deeper250m, themaximum concentration of Si is in April to May, the minimumconcentration is in September.(2) The nutrients concentration decreasing from offshore to opensea. High value centers of nutrients are concentrated in northeast ofTaiwan and southwest of Kyushu. Along the direction of Kuroshio axis,the monthly changes of nutrient is not obvious in the inlet and middle ofKuroshio. The strong upwelling system took high concentration ofnutrients from deeper into upper area in northeast of Taiwan andsouthwest of Kyushu, which is the reason of appears high nutrient valuecenter in these areas.(3) N/P、Si/N、Si/P in shallow waters of250m with a significant spatialdifferences. The spatial differences of N/P and Si/N are most obvious inAugust to September and March to April, the smaller differences occursin October to December. The spatial distribution of Si/P is different from N/P and Si/N, Strong regional differences appears in September, therelatively uniform spatial distribution appears in May to June.(4) The major nutrient concentrations limit in Kuroshio of East ChinaSea are N and P, which impact in shallow of300m. The nutrientconcentrations are higher than threshold concentration in300m todeeper area, so it can not appear the phenomenon of nutrientlimitation. Phytoplankton growth mainly occurs in the range of100~200m, the nutrient conditions for the region appears in thenortheastern Taiwan, the central area of Kuroshio and the southwest ofKyushu island on April to November, these areas will be the potentialfishery resource development regions.(5) Temperature, dissolved oxygen concentration has a greatimpact on nutrients which showing a high degree of a quadraticpolynomial relationship, and nutrient concentrations was highlynegatively correlated with them. Salinity and nutrients shows a linearrelationship and has a negative correlation with more than34.58valuein January to April and December, but the R2of fitting equation issmaller than others. This show that temperature and dissolved oxygenare involved in important environmental factor in the nutrient depletionand regeneration process. However, the impact of salinity on nutrients ismore complex.