First identification key for charophyte oospores from central Europe

Twenty-two central European stonewort species and two species groups belonging to the genera Chara, Lychnothamnus, Nitella, Nitellopsis and Tolypella may be identified by oospores using a dichotomous determination key based on binocular and light microscope features. Size, shape, colour, membrane decoration and ridge number are used as identification criteria. A detailed oospore description for each central European charophyte species allows a reliable identification to the species or species group level. Because of the importance and wide distribution of stoneworts in aquatic plant communities, the identification of oospores may give information on ecological parameters such as water temperature, chemistry and light regimes in charophyte stands. Ecological changes due to climatic or anthropogenic impacts may therefore be elucidated for past and present freshwater ecosystems.