| Ecosystem health refer to the ecosystem in a state of stability, sustainable, and keep its physical, chemical and biological integrity, which can provide human with different ecological product or service functions, and with the ability of self-regulation and certain repair under natural and anthropogenic interference. As bay is located in the interface of ocean, land, river, atmosphere and human society, the bay ecosystem exist various feedback among the subsystems. Broadly speaking, bay ecosystem should include nearshore land ecosystems, mudflat ecosystems and bay ecosystems. At the same time, bay ecosystem is also a complex ecosystem contains "natural-Economy-Society" system.Based on RS/GIS technology, combined with remote sensing image data, environmental monitoring data and social economic data, this paper take Yueqing Bay as study area and apply the PSR model to construct the bay ecosystem health comprehensive evaluation index system which contains 18 evaluation index that selected from land press, environment state and biological response. AHP and entropy method were used to determine the index weight of the index, and the matter element model was used to assess the yueqing bay ecosystem health, the result show that:(1) The ecosystem health in Yueqing Bay in spring was in worst level, and the results of the inner bay, middle bay and outer bay were worst level, moderate level and worst level, respectively. The ecosystem health in Yueqing Bay in summer was in moderate level, where the evaluation results in the inner bay, middle bay and outer bay were moderate level, excellent level and moderate level, respectively. The overall ecosystem health is not optimistic.(2) From the perspective of terrestrial pressure, the terrestrial pressure of Yueqing Bay ecosystem health has reached IV levels, namely poor levels. From the perspective of spatial distribution, the inner bay was best, and the middle bay was moderate while the outer bay was worst. From the perspective of individual indicators, the evaluation results of capita GDP (66300 CNY/person) and the intensity of human disturbance (0.36) in Yueqing Bay were in good grades; while the population density (910 people/km2), average COD emissions per unit area (1.26 t/km2·a) and natural shoreline retention rate (25.6%) were in poor grades. The intensity of mudflat reclamation (0.45) was moderate level, but the outer bay reclamation activities were very fierce which belong to poor grade. Population density, per unit area COD emissions, natural shoreline and mudflat reclamation retention strength became the main limiting factors in Yueqing Bay.(3) From the status of the environment, the result of comprehensive evaluation of ecosystem health in environmental status was excellent, but showing some salient features. Firstly, the result of environmental status in summer was superior than spring. Secondly, the spatial distribution of environmental status of the summer was decreased from outer bay to inner bay; and the results of the environmental status of the spring was decreased from middle bay, outer bay to inner bay. Thirdly, although the status of the environment is excellent, the index of organic pollutants and nutritional level was in high level. The water eutrophication was in severe condition. The index of organic pollutants and nutritional level becomes the main limiting factors in Yueqing Bay, and also became one of the major environmental problems in Yueqing Bay. Finally, the result of depositional environment and biological residues environment was in excellent and good level.(4) From the biological response, the result of biological response of ecosystem health evaluation in summer was superior than spring, but was poor in whole situation. The spatial distribution of biological response of the spring was decreased from outer bay, inner bay to middle bay and the summer was decreased from middle bay, inner bay to outer bay. The main reason of the poor biological response status was low primary productivity of phytoplankton in spring. |
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