Epiphytic algae occurring on submerged macrophytes were investigated as part of a study on the ecological status of a shallow macrophyte-dominated lake, Lake Skomielno, which has been used for recreation and fishery. Relatively high variability in biomass (DM) and chlorophyll a contents in epiphyton on particular plants was noted. Generally, the biomass of epiphytic algae was much higher in spring and autumn than in summer. In total, 335 taxa were found on the studied macrophytes with representatives of the Chlorophyta (143 taxa) and Heterokontophyta class Bacillariophyceae (131 taxa) dominating. The species composition of epiphytic algae was related to host plant and seasons, the highest species richness was observed on Stratiotes aloides in spring and on Potamogeton lucens in autumn. The Jaccard similarity index revealed differentiation of diatom communities between the macrophytes. Our data suggest that in the studied lake S. aloides and P. lucens can provide better habitat conditions for higher numbers of epiphytic taxa, abundances and epiphyton standing crop than Ceratophyllum demersum and Chara spp. can. The dominance of diatom species (e.g. Pseudostaurosira brevistriata (Grun.) Williams & Round, Achnanthidium minutissimum (Kütz.) Czarnecki, and Cocconeis placentula Ehrenb.) that are known as bioindicators of slightly alkaline, sufficiently oxygen-saturated and meso-eutrophic waters corresponds well with the physico-chemical parameters of Lake Skomielno.
