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Micrasterias foliacea (Desmidiales, Zygnematophyceae) is an interesting desmid species as its filamentous life form is quite different from all other species within the genus. Due to the large size of the filaments and cells, accurate species identification is easy. After its original description from Rhode Island (USA) it was recorded from five continents, but no record could be found of its presence in Europe. In this paper a review of the worldwide distribution of M. foliacea (Desmidiales, Zygnematophyceae) is presented, together with notes on the species' ecology. In addition to its currently known geographical distribution, the paper also records the species' presence at two new locations in southern Africa, namely Botswana (Okavango River) and Mozambique (Palma, Cabo Delgado). The paper presents a discussion of taxonomical levels of intraspecific taxa, based on morphological characteristics. It is proposed that the taxonomical status of M. foliacea Bailey ex Ralfs f. nodosa should be raised to the variety, as its nodular cell wall thickenings are unique morphological features. [ABSTRACT FROM AUTHOR]

Background: Effluents from agricultural activities, metal and peat mining, urban and industrial areas, informal settlements and wastewater treatment plants all influence tributaries feeding the Mooi River. All these land uses ultimately result in a deterioration of water quality in the Mooi River. Objectives: The main objective was to relate the effects of inflowing tributaries to water quality and phytoplankton assemblages in the Mooi River. Method: Physico-chemical environmental variables were compared with water quality objectives and known limits to assess general water quality in the Mooi River over a one-year period. Water quality and phytoplankton in tributaries were compared to that at sites upstream and downstream from their inflows to determine the extent to which the tributaries affected the Mooi River. Multivariate analysis assisted in the interpretation of phytoplankton and physico-chemical data at the different sites. Results: Seven phytoplankton phyla were identified in the Mooi River. Diatoms and green algae were most dense and diverse. Cyanobacteria were responsible for various problems, especially in the Wasgoedspruit where they dominated and reached high densities. Lowest phytoplankton density and diversity were found in the upstream and downstream sections of the river, while maximum density and diversity were found during summer in the middle reaches. The inflow of tributaries, especially the Wasgoedspruit, had a pronounced effect on water quality downstream. Phytoplankton density and diversity were less affected than chemical variables, especially nutrient concentrations. Conclusion: Various land use activities surrounding the Mooi River's tributaries contributed to a deterioration of water quality in the main stream of the Mooi River. [ABSTRACT FROM AUTHOR]

Background Botryococcus braunii is well known from all continents, but it has been sparsely recorded from Africa compared to other continents. The alga recently formed a rusty orange-red bloom in the Tilda Viljoen Dam, situated near Gobabis in Namibia. Blooms of this species are known to produce allelopathic substances that inhibit the growth and diversity of other phytoplankton, zooplankton and fish. Objectives The objective of this study was to record the presence of B. braunii in Namibia. Method Morphological features of the species were compared with illustrations and literature on B. braunii found in other continents of the world, particularly North America and Europe. Extensive literature surveys revealed its currently known geographical distribution. Results The organism responsible for the discolouration of the water was identified as B. braunii. Microscopic examination revealed large colonies that floated in a thick layer on the surface of the water. Literature searches on the geographical distribution of B. braunii revealed that this was the first record of this species' presence in Namibia. Conclusion The known geographical distribution of B. braunii was expanded to include Namibia. [ABSTRACT FROM AUTHOR]

Petalonema alatum (Borzì ex Bornet & Flahault) Correns is a nitrogen fixing, subaerial cyanobacterium characterized by a blue-green trichome surrounded by a very broad, lamellated mucous sheath. It typically grows on dripping limestone rocks in temperate regions, but it has also been observed in some calcareous lakes and limestone springs. Although the species is known to be present in the Americas, Europe and Asia, no records could be found for its presence in Africa. In the last decade, it was sampled twice from rock surfaces in cave overhangs in the Free State Province of South Africa, representing a first record of its presence in Africa. A taxonomic description, microscope images as well as detailed geographical distributions of P. alatum are provided. [ABSTRACT FROM AUTHOR]

The Vaal River has become so nutrient-enriched that algal blooms pose problems. A unique opportunity arose to determine if there were changes in the chemistry en algal composition of the Vaal River after oligomesotrophic Katse Dam (Lesotho) water was imported to augment supplies in the light of growing water demands in the Vaal River catchment area. Algal concentration and composition in the Vaal River during three periods (between 1992 and 1994,1998 and 2000, as well as 2004 and 2006) were compared to those in the Katse Dam (1998-2006). Some algal species, initially absent from the Vaal River, appeared in the river during and after transfer. Mixed algal assemblages found in the Vaal River before transfer of Katse Dam wafer gradually changed after transfer to assemblages mainly composed of cyanobacteria. The total algal concentration in the Vaal River Barrage doubled from the period between 1992 and 1994 to that between 2004 and 2006, indicating that the transfer of clear, oligomesofrophic Katse Dam water did not dilute the eutrophic Vaal River water sufficiently in order to reduce algal concentrations. Results showed that continuous downstream pollution and eutrophication of the Vaal River system eliminated the diluting effect of Katse imports. This resulted in changes in algal composition and concentration in the Vaal, characteristic of those associated with increasing eutrophication. [ABSTRACT FROM AUTHOR]