The Research On Phytoplankton Community, Driving Environmental Factors And The Possibility Of Cyanobacterial Bloom In Dongping Lake, China

Dongping Lake has been employed in the east route of the South-to-North Water Diversion Project as one of the significant storing lakes and water channels. At present, studies on phytoplankton in lakes have been well reported, but the report about phytoplankton, cyanobacterial bloom together with its preventation and control in Dongping Lake still has been regarded as a negligible plate. Thus, investigations of phytoplankton community, distribution characteristics, environmental factors and the possibility of cyanobacterial blooms in Dongping Lake can provide technical guidance for the east route of the South-to-North Water Diversion Project and pollution control in this Lake, and afford detailed information for researching the impact of the South-to-North Water Diversion Project on phytoplankton in the future.Chapter one in this paper represents the research progress on algae, lake algae, freshwater lake algae and Dongping lake algae, and then put forward the research purposes and methodology for this study.Chapter two focuses on the phytoplankton distribution charateristics and the community structures using qualitative and quantitative methods. From May2010to October2012,207phytoplankton species which belong to103genera in8phyla have been identified in Dongping Lake. Chlorophyta accounting for44.0%of the total phytoplankton species was dominant, followed by Bacillariophyta (23.7%) and Cyanophyta (14.0%) and less other species. The total algae density, Chlorophyta density and Cyanophyta density in summer and autumn were all higher than the other two seasons. The cyanobacteria density of each monitoring station in summer and autumn which were all at higher levels showed little change. The seasonal succession patterns of phytoplankton were as follows:Bacillariophyta-Cryptophyta-Chlorophyta (spring), Cyanophyta-Chlorophyta-Bacillariophyta (summer and autumn), Chlorophyta-Cryptophyta-Bacillariophyta (winter). The eutrophic status of Dongping Lake was evaluated by modified trophic state index method (TSIM) and trophic state index method. The results indicated that the lake was lightly eutrophicated. The environmental factors influencing the phytoplankton population community structure of Dongping Lake were also analyzed through redundancy analysis and Pearson correlation analysis. Temperature, transparency and chemical oxygen demand were regarded as the main driving factors influencing the phytoplankton growth.Based on physical, chemical, biological and other factors causing algae blooms, chapter three analyzes the possibility of cyanobacterial blooms in Dongping Lake. The results indicated that the main factors on cyanobacteria growth were temperature, transparency and chemical oxygen demand, and the preponderant species of cyanobacteria in summer was Pseudanabaena limnetica which was not indicators of cyanobacterial blooms. Besides, the water quality of Dongping Lake was getting better with the implementation of the water diversion project. Thus, cyanobacterial blooms was less likely appeared. Aphanizomenon issatschenkoi, following Pseudanabaena limnetica which was the most dominant species in Dongping Lake, was confirmed to be able to produce microcystin and might have the potential of forming water blooms. Thus, we should strengthen monitoring and investigation of Aphanizomenon issatschenkoi in the future.The differences of phytoplankton community between Dongping Lake and Nansi Lake are compared in chapter four. The results shows that different hydrological condition caused the differences of physical and chemical indicators in two lakes, leading to the differences of phytoplankton community in spatial and temporal distributions, seasonal succession patterns, dominant species and environmental driving factors.