THE SEASONAL EFFECTS ON THE ENCRUSTATION OF CHAROPHYTES IN TWO HARD-WATER LAKES

Encrustation and element content of six charophyte species from two hard-water lakes were investigated monthly for a period of 1year. Seasonal patterns were analyzed for the interaction of water chemistry. Encrustation followed a seasonal pattern for Chara contraria, Chara subspinosa, and Nitellopsis obtusa in Lake Kruselin and for Chara globularis and Chara tomentosa in Lake Lutzlow. However, no seasonality in the precipitated CaCO3 was observed for C.subspinosa in Lake Lutzlow and for C.tomentosa in Lake Kruselin, indicating a lake-specific dependency. Species-specific encrustation was found. Chara contraria and N.obtusa encrusted the most in June and August, whereas C.subspinosa and Nitella flexilis/opaca exhibited lowest encrustation in March and April. The precipitated CaCO3 of charophytes correlated negatively to the concentration of total inorganic carbon in both lakes. Element content of plant dry weight was species-specific for Ca and K, and lake-specific for Mg. No specific pattern was found for the TP and Fe contents. The results showed seasonal, species, and lake-specific influences on the encrustation of charophytes.