Messyasz, BeataRybak, AndrzejPikosz, MartaSzendzina, Lidia2014-06-162014-06-162013Messyasz et al. 2013, Biologie Animală, Supliment 1: 69-81.http://hdl.handle.net/10593/10961The genus Ulva (Ulvophyceae, Chlorophyta) consists of some 140 species which are present mainly in marine waters. Nine species occur in the inland waters in Poland (central Europe), of which U. flexuosa subsp. pilifera (Kützing) Bliding is the most widespread in the Wielkopolska region. The occurrence of Ulva species in any particular locality seems to be governed mainly by the availability of nutrients (N, P) than by the high levels of anthropogenic salinity in freshwaters. Freshwater Ulva can grow in different types of ecosystems from reservoir (Malta) through ponds (Tulce) or rivers (Nielba) and ending on drainage ditches. The main question addressed by this study was does the quantity and size of Ulva thalli increase together with the amount of nutrients in water? In addition, the aim of the study was to determine whether the development and the persistence for the long time of the big and dense Ulva patches exert influence for the aqueous ecosystem. We used freshwater Ulva as a model study species.enmacroalgeUlva sppfreshwater ecosystemsthallus and cells sizemorphologymorphologyPolandArtykuł