SPATIAL AND TEMPORAL VARIATION OF BENTHIC ALGAL COMMUNITIES IN THE LITTORAL ZONE OF LAKE DONGHU

Lake Donghu is a shallow eutrophic lake, dominant population compositions of the benthic algal communities presented significantly seasonal patterns in the littoral zone of Lake Donghu, Cladophora glomerata and Melosiravarians were the most important species during all seasons except summer, and some species of Achnanthes dominated the littoral zone in summer. Although benthic algal biomass of different sites was slight different, dominant species was significantly different. C. glomerata was the largest fraction at moderately eutrophic site C and M. varians contributed the most biomass at hypereutrophic site A. In summer, monthly mean benthic algal biomass was the minimum with chl a 41.5 Lg/cm2, it increasing to peak biomass with chl a 55.3 Lg/cm2 at autumn or winter. The low summer biomass was the results of physical factors such as instability of condition caused by raining and the weak of light because of water level rising. The content of chl b and chl c, the ratios of chl b/a and chl c /a among different sites had significant difference. These results suggested that the heavy eutrophic increased the relative proportions of diatoms, meantime decreased the ratio of green algae in the benthic algal communities. It also suggested that the community structure of benthic algae were good biotic indicators for the lake ecosystem health status. The seasonal patterns of benthic algae biomass were different from those of phytoplankton,meanwhile, it was negatively correlated with water temperature. It indicated that water temperature and phytoplankton were not the direct factors on the benthic algal community in the littoral zone of the lake Donghu. C. glomerata offered foods and available habitat for invertebrates, and it played an important role in the ecosystem function of Donghu Lake.