The Netrient Seasonal Variation Characteristics And Comparison Of Several Assessment Methodsof Eutrophication In Qingduizi-bay

The continuous survey was carried out from 2008 to 2009 in sea area of Northern Yellow Sea in Qingduizi-bay(E123°17′～123°24′, N39°34′～39°44′). Seasonal variation characteristics of inorganic nitrogen, phosphor and N/P were analyzed. The result shows that the concn of inorganic nitrogen in autumn was highest in Qingduizi-bay which reaches 197.75μg/L. The concn of inorganic nitrogen in winter was lowest which was only 71.45μg/L. The concn of phosphate in autumn was highest which reaches 19.75μg/L, while it droped to 2.09μg/L fast, which was the lowest of the year. Ratio of inorganic nitrogen to phosphate rises to 110.5 in summer from 39 in spring, then drops to 22.2 in autumn and rises up to 75.7 in winter, all far above Redfield value 16.Evaluating on Qingduizi-bay, eutrophication degree with Nutrition Index Method, Evaluation of Organic Pollution Index Method, Potential Eutrophication Assessment Method and EU "Comprehensive Evaluation". It shows that the four types of eutrophication evaluation methods are essentially the same, which stating that the bays were eutrophic condition. It means that these four methods have been all effective.However, based on the comprehensive analysis of the four evaluation methods in the Qingduizi-bay's eutrophication evaluation, it is found that Evaluation of Organic Pollution Index Method is more accurate than Nutrition Index Method. Compared to the first two methods, Potential Eutrophication Assessment Method was more detailed, which can determine the specific limiting factor for eutrophication. EU "Comprehensive Evaluation" is the development trend of eutrophication evaluation in expanding these scope of the marine environment monitoring based on the further Exploration and research.To sum up, although Evaluation of Organic Pollution Index Method and Potential Eutrophication Assessment Method of the defect does not reflect the ecological effects of eutrophication, which is still the first choice of the Qingduizi-bay's eutrophication evaluation methods based on the ecological environment data in Qingduizi-bay at the present stage. The results of the research is of great significance to the correct understanding of the eutrophication status of the Qingduizi-bay marine'water, laying the foundation for future research about eutrophication in the Qingduizi-bay's water, protection and maintenance of Qingduizi-bay's ecological health and sustainable development as well.