SUCCESSION OF THE PHYTOPLANKTON COMMUNITY IN RESPONSE TO ENVIRONMENTAL FACTORS IN NORTH LAKE ERHAI DURING 2009-2010

摘要

Phytoplankton samples were taken weekly from Sep-tember 2009 to November 2010 in Lake Erhai. The pur-pose was to obtain detailed information about the compo-sition variations in the phytoplankton community during the serious drought in 2009-2010 and to determine the driving force for the succession of the dominant genera. A total of 147 phytoplankton species were identified during our investigation. Among the 7 main divisions, the maxi-mum contribution (69%) belongs to the Chlorophyta division. The alternation of the dominant group was Cyano-phyta, Chlorophyta, and Bacillariophyta. The weekly variations in cell abundance and biomass of the dominant phytoplankton genera were examined. A succession character-ized by Psephonema and Asterionella (spring) →Melosira (summer) →Microcystis (autumn) →Microcystis and Psephonema (vvinter) emerged from the monthly average biomass.Weekly variations in the Shannon-Weaver index ranged between 0.269 and 2.183. Redundancy analysis results showed varied effects of environmental factors on the different phytoplankton dominant genera, with water tem-perature as the driving force for the seasonal succession of the dominant genera. The shift in succession pattern is induced by light intensity variation. In addition, the domi-nance of Psephonema in Winter is the first report in Lake Erhai in recent years.