||The freshwater lake of Lysimachia is situated in the area of Aitoloakarnania, near the town of Agrinio, in western Central Greece. Lake Lysimachia (Agelokastro lake, Konopi or Hydria) has a surface area of 1300 ha, a circumference of 17 km, maximum length of 6.25 km, a maximum width of 2.85 km, and a depth of up to 9m. It has a tectonic origin and occurs across the tectonic graben of Agrinio. It has positive water balance, because of the high input of water due to the streams and the sublacustrine inflow of karstic water. Lake Lysimachia has a relatively large drainage basin and is influenced by the water coming from Ermitsas stream, as well as the water of lake Trichonida (through Alampei ditch). It exhibits strong seasonal fluctuations of its water level, which is due to the high evaporation rate during summer and drainage to the river Acheloos (Leontaris, 1967). During the winter it often overflows. From the thermal point of view Lysimachia is warm monomictic lake. It belongs to the Carbonate type (Overbeck et al., 1982).Lake Lysimachia is surrounded by alluvial deposits, where cultivated fields mainly with Nicotiana tabbacum exist. In several places permanent or seasonal marshes occur. A macrovegetational study of the aquatic tracheophytes was carried out by Koumpli-Sovatzi & Vallianatou (1985). The natural shore-line vegetation particularly consists of herbs (Scirpus holoschoenus, Paspalum paspaloides, Mentha aquatica, Kickxia elatine, Cyperus longus, Carex otrubae, Juncus acutus etc.). Some shrubs (Vitex agnus-castus) and trees (Platanus orientalis, Salix alba, Populus alba) have scattered distributions. The species dominating near the shore line is Phragmites australis. It forms an extremely dense, almost continuous reed-fringe, mainly near the waters edge, as well as in the upper infralittoral zone and is interrupted in several places only, by human activities. The greatest characteristic cover is presented by the species Paspalum paspaloides. The submerged species Vallisneria spiralis predominates in the lower infralittoral zone, forming dense stands, while Ceratophyllum demersum, Myriophyllum spicatum and Najas marina present the lower cover.