Plankton Communities

Abstract

The spatial and temporal distributions of phytoplankton and zooplankton assemblages in the different limnological gradients of two Plitvice lakes (Kozjak and Prošće) are presented. The lakes are dimictic and oligo-mesotrophic. The phytoplankton community consists of 128 taxa belonging to the groups of Bacillariophyta, Charophyta, Chlorophyta Ochrophyta, Cyanobacteria, Cryptophyta and Miozoa, while the zooplankton community consists of 43 open water zone species: 35 Rotatoria, four Cladocera and four Copepoda. The main environmental factors affecting the phytoplankton community are nutrients (TP, TN) and conductivity. Chlorophyll a concentration is three times lower and total phytoplankton biomass is two times lower in Lake Kozjak than in Lake Prošće. Diatoms are the dominant component of phytoplankton in both lakes, while co-dominance of Ochhrophyta and Chlorophyta can be observed in Lake Prošće. A total of 18 Reynolds FGs are represented in Plitvice Lakes, with FGs A, B, C, D and P being the most represented in Lake Kozjak and B, C, D, E and F in Lake Prošće. The main environmental and spatial factors affecting zooplankton composition were compared to quantify shifts in their relative importance over time and to identify any factors affecting temporal changes.