“…In comparisons with other freshwater systems it is important again to consider that nutrient concentration or stock of plants can vary strongly through the growing season (Rejmánková, 1978). The nutrient concentration for C. demersum has been shown to be highest at the beginning of the growing season in spring (April), decreasing in summer, and increasing in autumn again (Gerloff & Krombholz, 1966;Best, 1977;Körner, 1996). In our study, the P and N concentrations of the biomass of C. demersum varied between 0.9-1.0% and 3.1-3.5%, respectively.…”