Characteristics Of Phytoplankton In Taihu Lake Basin And Its Indication Significance In Aquatic Ecological Function Regionalization

Phytoplankton in Taihu Lake basin was set as the study object in order to investigate and monitor the distribution characteristics of phytoplankton in different seasons, and discuss the community distribution characteristics of phytoplankton in the different water areas in the basin and its interaction with the environmental factors such as water quality.which then combined with aquatic ecological function regionalization in the Taihu Lake basin and its corresponding index to analysis the characteristics of phytoplankton indicating the basin aquatic ecological function regionalization.To provide basic data and scientific guidance for the health of Taihu Lake basin ecosystem and management of the water system and offer reasonable protection for management of Taihu Lake basin ecosystem.122 field sampling points were set in Taihu Lake basin, four times surveys of the field were set in October 2012, May 2013, February 2014 and July 2014. Conclusions were got as follows through the analysis:(1)Phytoplankton in Taihu Lake basin had the characteristics of seasonal succession. In winter, Bacillariophyta occupied the dominant position in species and quantity, Cyanophyta and Chlorophyta increased rapidly and bacillariophyta declined in spring. After entering into the summer, Cyanophyta, Bacillariophyta and Chlorophyta were increased both in species and quantity, amplification of Cyanophyta were the maximum. There were some differences between seasonal succession of phytoplankton in lakes and rivers in autumn, quantity and species of Cyanophyta and Chlorophyta in lakes were kept increasing while there was a decrease of them in rivers, Bacillariophyta decreased both in lakes and rivers. The density and species of phytoplankton in lakes in Taihu Lake basin were the maximum in autumn while minimum in winter. The density and species of phytoplankton in rivers in Taihu Lake basin were the maximum in the summer while minimum in winter. Microcystis flos-aquae and Microcystis aeruginosa in Cyanophyta in lakes were the most common as dominant species. Cyclotella in Bacillariophyta and Chlorella in Chlorophyta in rivers were the most common as dominant species. In the results of water quality evaluation from dominant species of phytoplankton, most part of the main water were β-mesosaprobic zone, main lakes were polysaprobic zone. Analysis of Algae community diversity showed a large difference in the four seasons in Taihu Lake basin, phytoplankton diversity is the best in summer while the worst in winter. Margalef diversity index could commendably show the diversity of phytoplankton in Taihu Lake basin.(2)In the correlation analysis of phytoplankton in lakes in Taihu Lake basin and environmental factors, SS、NO3--N、N/P、CODMn、F-、TN、SO42-、CO32-、NH4+-N、PO43--P、TP and DO were the closely related environmental factors, and CODMn was the most related factor. TN and TP were closely related to the phytoplankton in the eastern plain area, while density and density ratio of phytoplankton in the western hilly region did not show closely related to TN and TP. Reflecting there was obvious difference in the environmental factors that affects the distribution of algae in different regions in Taihu Lake basin.(3) Analysis of the 5 level II aquatic ecological function regions in Taihu Lake basin showed a large difference in the five regions, also, the environmental factors that affects the distribution of algae also has obvious difference; there was obvious difference in distribution III aquatic ecological function regions in Taihu Lake basin. The further Analysis with the existing indicators of Level III regionalization in the Taihu Lake basin indicated that the algae characteristic indexes(margalef diversity index) could be considered as indicator of regionalization.