Flagellate algae (Chrysophyceae,Dinophyceae,Cryptophyceae)in 48 high mountain lakes of the northerm and southern slope of the Eastern Alps:biodiversity,taxa distribution and their driving variables

摘要

Survey samplings onlater summer phytoplankton communities wee carried out on 48 hihg mountain lakes located on the austrian and italian slopes of the Eastern Alps.The lakes of North Tyrol (A)and South Tyrol (I)were sampled in 2000 as part of the EU project EMERGE (EVK1-CT-1999-00032).The lakes of Trentino (I)were investigated in other research projects during 1996 and 1997 (Adamello mountain range)and 2000 (catchment of the River Avisio),respectively.The objectives of this paper are :(1)to study taxonomy and biodiversity of chrysophyceae.Dinophyceae and cryptophyceae in hihg altitude lakes of the easter Alps;(2)to identify functional flagellate groups characterising lakes with similar habitat projperties,(3)to identify the environmental variables driving abundanc4e and sistribution of the three selected algal groups,thus contributing to the selection of sensitive bionidicator taxa.The lakes investigated show rather wide morphoogical,chamical and dtrophic state gradients.Flagellate algae account for a median relative aboundance (R.A.)of 68%.Chrysophyceae are the most important group in terms of biodiversity and R.A..Special flagellate associations could be related to lake teatures,like catchment geology,mineralization level and nutrient concentrations.However,the distribution of flagellatealgae did not allow a complete geographical separation of the lakes studied in the differetn districts.multivariate canonical analyses indictate that the distribution of Chrysophyceae is mainly driven by NO_3-N concentration and thermal conditions,while dinophyceae are driven by a combination of alkalinity,altitude,thermal conditions and,less importantly,untrient concentration.physical properties of hte lakes,such as thermal conditiona and lake depth,represent the principal drivig variables for cryptophyceae.The responses to the fifferet environmental variables suggest that the three flagellate groups analysed might be used as indicatiors for environmental changes inhigh mountain lakes of the Eastern Alps.