Aquatic vegetation is very dynamic in space and time; its ability is to colonize quickly new localities on the one hand, on the other hand is highly vulnerable because of natural or man-made processes (e. g. terrestrialization, eutrophication, direct destruction). The Slovak national overviews of aquatic vegetation were done several years ago and are split into two volumes [1, 2]. Intensive research of aquatic habitats from last years brought hundreds of new relevés and several new plant communities have been documented for the first time in Slovakia. In addition, the new syntaxonomical approach designed for species-poor aquatic communities has been established [3].

The aims of this study are: i) to sum up information about aquatic vegetation (classes Lemnetea, Potametea and Charetea) from Slovakia, ii) to present preliminary results of new classification of Slovak aquatic vegetation.

Our dataset included 1220 relevés of aquatic vegetation. Relevés were gathered during years 1953–2015, there is no relevé from together 16 years. The most fruitful years were 2008, 2009, 2014 and 2015 (about 34 % of all relevés). The most productive authors were Helena Oťaheľová, Richard Hrivnák, Kateřina Bubíková and Jaroslav Rydlo. We applied new classification method designed for species-poor vegetation by Landucci et al. [3] using JUICE programe [4]. Totally, 1142 relevés were classified to association level. Altogether, classification distinguished 3 classes, 9 alliances and 52 associations. The most frequented associations were Lemnetum minoris, Ceratophylletum demersi and Potamo pectinati-Myriophylletum spicati. In contrary, associations with less than 10 relevés were communities of rare occurred species, e. g. Ricciocarpos natans, Groenlandia densa, Nitellopsis obtusa.