Lake Finsevatnet is a regulated monomictic alpine lake situated a little north of the Hardangerjøkulen glacier in Ulvik, Hordaland county. The lake is regulated 3,3 meters at most. Lake Flakavatnet is also a monomictic alpine lake, situated some kilometres north of lake Finsevatnet. The investigations were carried out from August 2003 to September 2004. Both qualitative and quantitative phytoplankton was collected in both lakes during this period, and so was water for chemical analyses.
Lake Finsevatnet is an oligo-mesotrophic lake while lake Flakavatnet is an oligotrophic lake. The conductivity is higher in lake Finsevatnet than in lake Flaka-vatnet, but the conductivity values are low in both lakes. The pH is weakly acid in both lakes and the alkalinity values are low. The oxygen-saturation is high in both lakes through the whole water-column, but lake Finsevatnet has a decrease towards the sediment in the ice-covered period. There where 90 recorded species in lake Finsevatnet (52 genera) represented within the Bacillariophyceae, Chlorophyceae, Chrysophyceae, Cryptophyceae, Cyanophyceae, Dinophyceae, Euglenophyceae and Xanthophyceae. In lake Flakavatnet 31 species where recorded (23 genera) within Bacillariophyceae, Chlorophyceae, Chrysophyceae, Cryptophyceae, Dinophyceae, Euglenophyceae and Xanthophyceae. The phytoplankton biomass in lake Finsevatnet was dominated by Rhizosolenia longiseta (Bacillariophyceae) almost throughout the year, but one of the winter samples was dominated by an unidentified dinoflagellate (Dinophyceae) together with Chromulina sp. (Chrysophyceae) and R. longiseta.Only one quantitatively phytoplankton analysis was executed in lake Flakavatnet (late winter 2004). This sample showed a lower biomass for lake Flakavatnet than was found in a comparable sample in lake Finsevatnet. The chrysophytes dominated the phytoplankton in this sample. The biomass of Chromulina sp. was particularly high.
The biomass value in lake Finsevatnet is higher in this study than found in a previous study.