Phytoplankton qualitative and quantitative analyses from the upper, middle and lower Morava River stretches and from lowermost Dyje River in November 2005 are presented. In the late autumn phytoplankton samples taken from the Morava in two sampling points in the Czech Republic (Olomouc, Lanžhot), and in one point in Bratislava-Devín, Slovakia, 346 species and infraspecific taxa belonging to 118 genera were determined. The highest number of species (incl. infraspecific taxa) was found in Bacillariophyceae - 153, following by Chlorophyceae - 100. About 19 taxa have not been yet registered in the lowest stretch of the Morava River. Koliella elongata (NYGAARD) NYGAARD (Chlorophyceae, Ulotrichales) is a new record for Slovakia. In the Dyje River, the main right side tributary of the Morava, 115 species and infraspecific taxa belonging to 49 genera were found, from them 79 species and infraspecific taxa (66% of total taxa) from Bacillariophyceae, while Chlorophyceae were represented only by 16 species and 1 variety.
In the Morava River the highest phytoplankton abundance was 29 317 cells per ml, and the highest value of phytoplankton biomass was 16.0 mm³.l^-1. In the Dyje River the respective values were 4 085 per ml and 2.4 mm³.l^-1.

Current knowledge on the phytoplankton composition of the Zámecký Pond at Lednice (Moravia, Czech Republic) is presented. The pond has become a National Nature Reserve, and its use for fishery is highly limited by the purpose of nature conservation. The fish stock of the studied pond has the greatest influence on the structure and abundance of phytoplankton. Altogether 343 taxa of cyanophytes and algae were found during the whole hydrobiological monitoring.

Surface waters affected by eutrophication produce more biomass and enable development of organisms which are difficult to remove during the water treatment technology. The increasing numbers of organisms in treated water cause the problems during the treatment process, namely in coagulation and filtration stages. The quality of water has to be controlled and monitored by drinking water suppliers during all stages of the treatment process beginning at the water source until the end of distribution systems. The knowledge of ecological requirements of individual organisms for water quality evaluation, and the impact on biological stability of drinking water is used for evaluation of control points in the water treatment process. The critical points that should be monitored during the water treatment process and further distribution of water are presented in this paper.

Planktonic representatives of nostocacean genus Anabaena belong to the group of important water-bloom-forming cyanobacteria. Their populations develop mostly in summertime, especially in eutrophicated water bodies. Hence, they can strongly influence the quality of various kinds of surface waters. For clear identification, unambiguous species definition and a complete knowledge of the range of morphological variability of single morphospecies are necessary.. This review of the literature summarizes studies connected with the taxonomy of the above mentioned cyanobacterial group, mainly with respect to phenotypic features and morphological variability in relation to changing growth conditions.

The composition and dynamics of phytoplankton communities in different types of floodplain pools (the River Morava floodplain, the Czech Republic) were studied in relation to selected physical and chemical parameters. Significant differences in phytoplankton were found between meadow and forest types of pools. On the contrary, no significant differences were found between periodical and permanent types of pools and between natural and artificial pools. Seasonal dynamics of phytoplankton is significant and is influenced by temperature course during the year.

Randomly selected samples of cyanobacterial mats growing on wetted walls of two distinct localities (Barranco de las Augustias, and Los Tilos) in La Palma (the Canary Islands) were collected. The collected samples contained twelve cyanobacteria morphotypes (determined according traditional system). Populations of both localities were dominated by coccoid cyanobacteria (Aphanothece pallida and Aphanothece cf. saxicola) and in some sampling sites by filamentous cyanobacteria Nostoc spp. and Leptolyngbya spp. In spite of the fact that the Canary Islands are characterized by a high level of species endemism mainly in terrestrial plants, most of the isolated cyanobacteria are considered to be cosmopolitan or widespread. But also some unknown morphotypes, e.g. Calothrix sp., were found to be common. Morphological changes in Calothrix were studied using light microscope and remarkable morphological changes in the type of branching and filament morphology were found.

The single cell gel electrophoresis or Comet assay is a sensitive, reliable, rapid and economic method for DNA double- and single-strand breaks, alkali-labile sites and delayed repair site detection, in eukaryotic individual cells. Given its overall characteristics, this method has been widely used over the past few years in several different areas. In this paper we review briefly the basic data about the principles, methodology and applications of this assay and we discuss also the possible explanation for not achieving comets to date in singlecell green alga Chlamydomonas reinhardtii.

The confocal microscopy proves useful in the investigations of chloroplast morphology and ontogeny of several coccal green algae. The three-dimensional images allow the reconstruction of the chloroplast morphology and the exact determination of the chloroplast number in the cell. This character is essential for species determination in numerous genera of coccal green algae. The simple method of pyrenoid visualisation by confocal images is demonstrated. Within the pyrenoid we can recognise the structure and shape of the invaginated thylakoids. In comparison with the methodically difficult transmission electron microscopy, the confocal microscopy provides a simple and appropriate method for the morphological and taxonomic studies of various algal taxa.