| Based on the investigation data from the two cruises in April and August of 2006 in the area of Hangzhou Bay, total 55 species of phytoplankton, 53 species of zooplankton, 46 species of zoobenthos, and 49 species of inter-tidal biological were identified, and at the same time, 22 species of fish larvae and juveniles were determined. The phytoplankton was better in the diversity. The zooplankton biodiversity index varied from 0.54 to 3.65, and the index in August was larger than in April, and the index of Shallow-water type II net was larger than the index of Shallow-water type I plankton net. The zoobenthos biodiversity index ranged between 0.34 and 1.55, and also the index in August was larger than in April. The inter-tidal biological diversity was in the general level.Contrasting with the historical data, the density of phytoplankton showed growing trend over the years, and the average density of zooplankton were more than 100 ind/m~3 except it was larger in 2006, and the the average biomass of zooplankton were some dozens mg/m~3. The density of zoobenthos showed obvious increase variation trend in the last three years, while there was not much change of the biomass.The ecosystem health index of Hangzhou Bay was 23.3, and the condition of ecological health was in the sub-health level. The poor community structure of marine biology in Hangzhou Bay showed that the ecosystem was interfered seriously.Correlation Analysis indicated that, from 2004 to 2006, the density of phytoplankton and zooplankton performanced same variable trend, and there was positive correlation between them. The biomass and density of zooplankton showed obvious positive correlation in both two cruises of 2006, which indicated that the zooplankton biomass and density were consistent in time and space changes. Phytoplankton displayed neither correlation with water temperature nor with salinity, but the species of zooplankton showed obvious correlations with water temperature and salinity.
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