| Seasonal changes of phytoplankton, epiphytic diatoms and benthic diatom assemblages in four mangrove areas of Houyu Bay in Fuding City, Fugong Village in estuary of Jiulong River, estuary of Zhangjiang River in Fujian and Futian in Shenzhen City of Guangdong Province, respectively, were studied from Jan. 2001 to Jan. 2003. Influences of salinity, pH, six single and mixed heavy metals (Cd2+, Cu2+, Zn2+, Pb2+, Mn2+ and Cr3+) on extracellular polymeric substances (EPS) secreted by benthic diatoms of Cylindrotheca closterium were also studied. The results were showed as following:1. Totally 167 species (including varieties) belonging to 6 phyta in 49 genera were identified in phytoplankton in four mangrove areas. 77 species (including varieties) belonging to 4 phyta in 32 genera were found in mangroves of Houyu Bay in Fuding City, 96 species (including varieties) belonging to 5 phyta in 39 genera in Fugong Village in estuary of Jiulong River, 86 species (including varieties) belonging to 6 phyta in 31 genera in estuary of Zhangjiang River, and 75 species (including varieties) belonging to 5 phyta in 25 genera in Futian in Shenzhen City, respectively. 20 common species occurred in four mangroves, and the farther distance between sample locations, theless in common species.2. Diatoms were dominant in phytoplankton of four sampling sites in each season, and the percentage of diatoms in total species number and density was more than 90 percent.3.Typical freshwater algae species occurred in phytoplankton of four mangrove areas, indicating the occurrence of the brackish water.4. Benthic and epiphytic diatoms closely related to mangroves occurred abundantly in phytoplankton of four sites, whose percentage in total species number was more than 50 percent.5. Redtide causative algae were found in four mangroves, but their distribution in 4 sites was different. Number and density of redtide causative algae was low in phytoplankton in Houyu Bary of Fuding City and estuary of Zhangjiang River, and redtide causative algae were dominant in Fugong Village in estuary of Jiulong River and Futian in Shenzhen City, showing water was polluted in some degree.6. Nanodiatoms were common or even dominant in four mangrove areas.7. Phytoplankton communities were characterized by abundant species and low density in Houyu Bay of Fuding City and estuary of Zhangjiang River, comparing to phytoplankton showing less species than 10 years before and simplified dominant species in Fugong Village of estuary of Jiulong River, and phytoplankton showing smaller cell, less species number, increasing density and more pollution tolerant species in Futian of Shenzhen City.8. According to relations between phytoplankton density andXIVtrophic level, diversity index and pollution level, we concluded that oligotrophic water occurred in Houyu Bay of Fuding City and estuary of Zhangjiang River, while mesotrophic water occurred in Fugong Village of estuary of Jiulong River, and eutrophic water occurred in Futian of Shenzhen City.9. Totally 152 species in 32 genera (including varieties) were observed in epiphytic diatoms in four mangroves, in which 70 species in 23 genera (including varieties) were found in Houyu Bay of Fuding City, 72 species in 32 genera (including varieties) in Fugong Village of estuary of Jiulong River, 88 species in 25 genera (including varieties) in estuary of Zhangjiang River and 77 species in 26 genera in Futian of Shenzhen City, respectively.10. Similar patterns were observed in epiphytic diatoms in four mangroves. Firstly, number of common species was high and took a high percentage in total species richness of 36% to 48%. Secondly, high BVI species were similar in four sites. Thirdly, dominant genera of four sites were Nitzschia and Navicula.11. Navicula mutica showing eutrophic water was dominant in epiphytic diatoms of mangroves in Fugong of Longhai City in summer, autumn and winter of 2002, while diversity index and evenness index of epiphytic diatom assemblages. Nitzschia fasciculate was do...
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