LAUSR

Abstract Restoration of urban lakes becomes necessary to slow down unfavourable processes and to recover theirrecreational role. Macrophyte communities are good bioindicators, thus they can be used to assess the effectiveness of restoration. The aim of the study was to determine the dynamics and patternof macrophyte recovery as a result of the restoration measures in a degraded shallow urban lake characterized by strong cyanobacterial blooms. Annual changes in the composition and areal coverage of littoral macrophyte phytocoenoses, and in the Ecological State Macrophyte Indexwere recorded using a GPS and the ArcGIS programme and analysed in relation to changes in water quality for three years following restoration measures (phosphorus inactivation, aeration, and biomanipulation). The shifts were statistically significant in the first two for total nitrogenconcentrationand three years for chlorophyll aconcentration, whereas total phosphorus concentration only decreased significantly in the third year. Changes in water transparency were not significant. The ecological status of the lakewas good or moderate. A characteristic pattern of recovery was observed. Phytocenotic richness increased (from 9 to 12 communities) and total phytolittoral area decreased (from 42 to 37 ha, i.e. 12%) during restoration efforts. The area of hypereutrophic plant communities ( Ceratophylletumdemersi , Hydrocharitetummorsus-ranae , Typhetumangustifoliae ) decreased, the former submerged community returned ( Potametumlucentis ) and the area of some existing communities (e.g. nympheids) increased. Slow return of elodeidswas caused by low transparency andlack of submerged vegetation propagules, which are the most probable limiting factors of the recolonization process.