The centric diatom Puncticulata balatonis (Pantocsek) Wojtal et Budzynska, comb. nov., in the plankton of eutrophic-hypertrophic Rusalka Lake (Western Poland)

Cyclotella balatonis Pantocsek is probably a common and widely distributed component of the phytoplankton in mesotrophic to eutrophic European lakes and rivers. However, the distribution and ecology of the species are still unclear, since the species remained hidden in the broad C. radiosa (Grunow) Lemmermann - concept throughout most of the 20(th) century. Cyclotella balatonis was found to form quite a large population in the plankton of a small and shallow, urban, eutrophic to hypereutrophic lake (Rusalka Lake, Western Poland). The species occurred in the lake throughout the study period, from February till December 2007, with its highest number in the winter - spring period. The morphology and fine valve structure of the species are described in the paper, documented with light microscope (LM) and scanning electron microscope (SEM) micrographs, and discussed along with the species ecology. Additionally, Cyclotella balatonis is formally transferred into the genus Puncticulata [P. balatonis (Pant.) Wojtal et Budzynska, comb nov.], and compared with the morphologically similar taxa - P. radiosa (Lemmermann) Hakansson, P. conga (Ehrenberg) Hakansson and P. praetermissa (Lund) Hakansson.