| Recently, coastal ecosystem health assessment is one of the hotspots in ecology research field, and to find comprehensive assessment tools of coastal ecological quality is the most important issues. The aim of ecosystem health research is to keep ecosystem self-organization and resilience. And managers and decision makers could take the corresponding measures to manage and restore degraded ecosystems, and also to achieve sustainable development of human society.Ecosystem health assessment methods can be divided into two categories, ecological indicator method and comprehensive indicator method. Ecological indicators method is concerned with ecosystem status, by using ecosystem structure and ecosystem function indicators. Comprehensive indicator method focuses on the benefits of human being, which combine multiple indicators including human health, social, and economic indicators etc., to consist comprehensive indicator system to evaluate ecosystem health. In this study, coastal ecosystem was used as research objective.AHP and grey clustering method were applied for ecosystem health assessment. The orientation was to find an optimized method for coastal ecosystem health assessment, by comparing the results under different methods mentioned above. Both AHP and grey clustering method are included in comprehensive indicator method, which is combined with a number of varied indicators to assess costal ecosystem health. According to the study results, Tianjin costal ecosystem was in the situation of sub-health in year 2007, while AHP was applied. Grey clustering method was applied to Yellow sea and Bohai sea, by assessing water quality index, sediment quality index, ecological index and comprehensive index based on year 1997. A conclusion can be made, that grey clustering method and single pollution index lead to a consistency, as the difference between results during the ecosystem health assessment was not significant. This proved that grey clustering method is suitable to be applied for costal ecosystem assessment. Tianjin costal ecosystem was taken as example, by applying different level of ecological indicators, such as Shannon index, Pielou evenness index, Simpson index and Margalef richness index, which are diversity index; also Bray-Curtis cluster analysis, PCA, NMDS, which are multivariate analysis methods; and K-dominance curve, ABC curve, W-statictic, which are based on biomass and abundance; in addition, exergy and specific exergy, which are thermodynamic index. All ecological indicators assessments were carried out under corresponding circumstances. Some ecological indicators were selected, which were able to reflect ecosystem health situation representatively and all-sided. At the same time, some indicators were found which were significant and systematical for the assessment.The results of 2005 to 2007 indicate that the ecological status of Tianjin coastal area, has significant interannual variation with succession of dominice species of benthic community in temporal scale. In spatial area, the South (DaGang DianChang area) and the North (Da Shen Tang area) of Tianjin coastal area have better ecological status, and the other areas between DaGang DianChang area and Da Shen Tang area and DaGang YouTian area are being partly perturbance. Research on the applicability of ecological index show that, (a) biodiversity index used in this study works well in most cases, but could not reflect the reality completely and accurately, (b) the evaluate results of ABC curves and W-statistic are not match with the actual, (c) results of multivariate analysis could refelt the similarity of ecosystem species composition, and the species changing during community succession, (d) exergy and specific exergy are further be able to indicate the real ecological status from both ecosystem function and ecosystem structure. The variation tendency of exergy and specific could indicate different perturbances, which gives the realistic picture of the ecological status of research region. |
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