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  • Author: Beata Messyasz x
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Differences in the ultrastructure of two selected taxa of phytoplankton in a thermally stratified Lake Holzmaar (Germany)

Abstract

This paper presents the results of ultrastructural studies and ecological aspects of some phytoplankton species belonging to the groups of cyanobacteria (Planktothrix rubescens, Synechocystis aquatilis) and green algae (Desmodesmus grahneisii). Specimens were collected during summertime from the mesotrophic and stratified Lake Holzmaar (Western Germany) as planktonic forms from the pelagic zone. The highest cyanobacterium concentration was detected in the metalimnion, where the alkaline pH, low phosphorus and high nitrogen contents were recorded. P. rubescens was characterized by straight filaments up to 1000 μm long and 5.4-8 μm wide and numerous aerotopes in cells. The accompanying algae were identified by ultrastructural analysis and photographic documentation was provided. In the case of D. grahneisii, chloroplast was situated in the parietal part of cell, with one large, oval pyrenoid and, in addition, the granular and spiny cell wall was an important taxonomical criterium for the Desmodesmus genus. This is in contrast with the cyanobacterium S. aquatilis, in which a homogeneous content with visible chromatoplasma was mostly distributed throughout the cell. This algal association was stable in the epilimnion characterized by the presence of high temperature, pH values (>8), nitrate nitrogen and oxygen concentrations

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New data on distribution, morphology and ecology of Oedogonium capillare Kützing ex Hirn (Oedogoniales, Chlorophyta) in Poland

Abstract

Algological investigations were focused on taxonomy, chorology and ecology of threatened filamentous green alga species in Poland. Studies on Oedogonium capillare Kützing ex Hirn growing in large quantities in association with Cladophora rivularis (Linnaeus) Hoek in pond were conducted. The aim of these studies was to describe the distribution, ecology and morphology of O. capillare as part of a more comprehensive study of this filamentous green alga. It is the eighth record in Poland for O. capillare. Filaments of O. capillare were grown over a wide pH range (7.3-9.6) and in high variability of nutrients. Vegetative cells, oogonia and antheridia were observed, which allowed taxonomic identification. O. capillare occurs in eutrophic waters which requires protection of its habitat.

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Spring phytoplankton and periphyton composition: case study from a thermally abnormal lakes in Western Poland

Abstract

Getting to know the response of different groups of aquatic organisms tested in altered thermal environments to environmental conditions makes it possible to understand processes of adaptation and limitation factors such as temperature and light. Field sites were located in three thermally abnormal lakes (cooling system of power plants), in eastern part of Wielkopolska region (western Poland): Pątnowskie, Wąsosko-Mikorzyńskie and Licheńskie. Water temperatures of these lakes do not fall below 10°C throughout the year, and the surface water temperature in spring is about 20˚C. In this study, we investigated the species structure of the spring phytoplankton community in a temperature gradient and analyzed diversity of periphyton collected from alien species (Vallisneria spiralis) and stones. 94 taxa belonging to 56 genera of algae (including phytoplankton and periphyton) were determined. The highest number of algae species were observed among Chlorophyta (49), Bacillariophyceae (34) and Cyanobacteria (6). In spite of important differences in temperature in the investigated lakes, taxonomic composition of phytoplankton was comparable. Thermophilic species: Glochidinium penardiforme and Cylindrospermopsis raciborskii were found in the species structure (blooms were not observed). The obtained data also showed that the biotic surface of Vallisneria spiralis was a better substrate for Bacillariophyceae colonization than stones. The examination in the spring season of these thermally altered lakes, indicated the taxonomic composition of phytoplankton typical for eutrophic reservoirs (not heated). There was no replacement of any phytoplankton groups which are characteristic for spring conditions, even if there were changes in the competition dynamics.

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