Historical changes of phytoplankton functional groups in Lake Fuxian,Lake Erhai and Lake Dianchi since 1960s

Phytoplankton is one of the major primary producers and plays important roles in the aquatic ecosystems. The temporal and spatial variations of the algae could reflect the environmental dynamics. In light of the morphological,physiological and ecological characteristics of algae,phytoplankton functional groups theory was applied first time for these lakes to describe the tolerance and preference of algae in detail. The phytoplankton assemblages were considered to be good indicators of environmental conditions. The data of phytoplankton composition dated from the 1960 s was collected and analyzed for Lake Fuxian,Lake Erhai and Lake Dianchi,respectively. Great changes have taken place in phytoplankton assemblages in the three lakes during the past 60 years. The historical change of dominant phytoplankton functional groups was demonstrated as C,X2,Lo,F,P( 1960s)-H1,C,P( 1980s)- P,C,T( 1990s)-T( after 2000) for Lake Fuxian; J,Lo,MP,C,H1( 1960s)-C,H1( 1980s)-C,H1( 1990s)-C,H1,M( after 2000) for Lake Erhai; J,N,P,MP,Lo( 1960s)-J,P,MP,M( 1980s)-J,M( 1990s)-M( after 2000) for Lake Dianchi. The reduction of low-temperature tolerance species and increase of high-nutrition preference species dated from the 1960 s might give some indication of the environmental changes of warmer temperature and nutrients increases in the three lakes.