Phytoplankton community in lentic habitats of large karstic river – riverine and barrage lake system

Taxonomical and functional composition of phytoplankton show clear seasonal patterns in the different lotic and lentic habitats. Compositional changes in phytoplanktic communities, with physical and chemical parameters of water were studied from April to September in2017 in two lentic habitats on Krka River, Visovac and Brljan lakes, for deepening the knowledge about the functioning and structural characteristics of these specific habitats. During sampling, temperature and oxygen were measured in depth profiles providing stratification curve and the position of deep chlorophyll a (Chla) maximum. Stratification was detected in the summer months in Lake Visovac, while there was no stratification in Lake Brljan. Deep Chl a maximum was not detected in these lakes, but clear anoxia was present in summer in Lake Visovac. Temperature and oxygen profiles indicated that Lake Brljan is a riverine system, while Lake Visovac is lake with much longer retention time. Taxonomic composition and Functional groups (FGs) clearly reflected to hydrological characteristics of the habitat. Centric diatoms belonging to FGs D and P as typical potamoplankton dominated in riverine Lake Brljan. Barrage Lake Visovac was characterized by the co-dominance and seasonal changes of centric diatoms, chrysophytes and dinoflagellates. Seasonal change in FGs composition (C-X2, U-L0) indicated the mesotrophic status of the stratified lake what was also confirmed by the results of physical and chemical parameters.