Biogeographical Characterisation of phytoplankton assemblages in high altitude, and high latitude European lakes
Tolotti, Monica; Forsström, Laura; Morabito, Guiseppe; Thaler, Bertha; Stoyneva, Maya; Cantonati, Marco; Šiško M., ; Lotter, A.
Phytoplankton species composition and diversity, geographic distribution, biomass and dominance, and their driving variables were investigated in a set of high altitude (alpine) and high latitude (subarctic) lakes located in the Alps, the Rila Mountains and in Finnish Lapland. The 138 lakes, extensively surveyed during summer 2000 as part of the European Project EMERGE (EVK1-CT-1999- 00032) and a regional project in the eastern Alps, cover a relatively wide range of morphological, chemical and nutrient gradients. Principal Component Analysis identified geography (and related variables, such as ice cover duration and water temperature) and catchment geology as responsible for the major environmental gradients in the lakes studied. The phytoplankton assemblages were found to be diverse, although mostly dominated by flagellates (chrysophytes, dinoflagellates and cryptophytes). Non motile green algae were quantitatively less important, with the exception of the Finnish lakes. Canonical Correspondence Analysis separated lakes located in Finnish Lapland from those in the Eastern Alps, based mainly on geographical location and related variables. Two minor satellite lake clusters located in the SW Alps and Rila Mountains were observed based on nitrogen level in the lakes and vegetation cover in the catchment, respectively. Different phytoplankton species composition and functionality characterised each lake cluster. Three key algal groups were outlined, which could be used for the ecological characterisation of remote mountain lakes, i. e. Conjugatophyceae (exclusive to the high latitude Finnish lakes), Dinophyceae (exclusive to the Eastern Alps) and Chrysophyceae (widely distributed in the lakes surveyed and ranked in at least four different functional groups).