Phytoplankton in three Tatra mountain lakes of different acidification status

Abstract

Seasonality and depth distribution of phytoplankton were studied in three alpine lakes of the High Tatra mountains: Nižné Terianske Pleso, Dlugi Staw and Starolesnianske Pleso. The lakes differ in size, depth, nutrient status (phosphorus) and acidification status (pH, alkalinity, calcium). The highest biomass was found in the small, shallow, phosphorus - rich and acidified lake Starolesnianske. An extremely low phytoplankton biomass was found in the medium sized Dlugi Staw, which is very poor in phosphorus and which is a transition lake between the acidified and bicarbonate ones. The Lake Nižné Terianske is a standard deep, oligotrophic high mountain lake by most of its characters, phytoplankton included. Most of phytoplankton of the three lakes are flagellates. In the non-acidified Lake Nižné Terianske the taxa contributing most to the biomass are Chrysophyceae (Chromulina and other) and dinoflagellates (Gymnodinium uberrimum, Woloszynskia). In the acidified Lake Starolesnianske the most important groups are green flagellates (Chlamydomonas) and dinoflagellates (Peridinium inconspicuum, Woloszynskia ordinata, Katodinium). The non-motile component (Chroococcus, Oocystis, centric diatoms) is sometimes important in the extremely poor phytoplankton of Długi Staw. Moreover, resting stages (mainly stomatocysts) often prevail over active phytoplankton in this lake. Seasonal variation in the amount of chlorophyll per unit biovolume was observed in the lakes Nižné Terianske and Starolesnianske, brought about apparently by changes of the underwater light climate.