Eutrophication level of Phragmites australis habitats at a shallow coastal lake, Paljassaare Peninsula, Tallinn.

The eutrophication level of a lake situated in the centre of the Paljassaare Peninsula, Estonia, was estimated using chemical characteristics of common reed (Phragmites australis). Comparison with other Estonian waterbodies revealed considerable differences. The N and P concentrations in the leaves and the N concentration in the stems of P. australis during the phenophase of early flowering were in Paljassaare (data from 11 sampling sites) 1.5-2-fold higher than in the eutrophic Lake Vortsjarv, in the high-productivity delta of the Kasari River, and in the Vaike Vain Strait. For P in stems the differences were even greater. The N/P ratio in P. australis shoots indicated N limitation in the lake and seashore on the Paljassaare Peninsula (N/P ratio 6-11), the Kasari River delta (ratio 8), and the Vaike Vain Strait (ratio 12), but P limitation in the oligotrophic Lake Tanavjarv (ratio 21). In the eutrophic Lake Vortsjarv the accessibility of N and P is probably balanced (N/P ratio 15). As large amounts of nutrients have accumulated in the lake on Paljassaare, the process of its growing over has accelerated during the last decade.