This report contains the results of some ecological and systematic studies on the diatoms from the Vaal Dam catchment area in the Transvaal, and the Bloukrans River in the Eastern Cape Province. In Part 1 the effects of high concentrations of nitrogen were studied in relation to the composition of the diatom associations. Water samples from four stations on the Bloukrans River were analysed chemically at certain intervals during the months of April and August 1967. Diatom samples collected from these stations at the beginning and end of each of these sampling periods were subjected to a "Thomasson Analysis" to determine the relative densities of the various species in the diatom associations. A statistical analysis of the results reflected a poor but positive correlation between the two variables, i.e. high numbers of nitrogen heterotrophic Nitzschiae were correlated with high concentrations of nitrogen, while low numbers were correlated with low concentrations. Part 2 presents the results of the ecological studies on the diatom associations of the Vaal Dam Catchment Area. In this section the diatom associations from each sampling point or station were subjected to a "Thomasson Analysis" to determine the relative densities of the different species in the associations. Employing already known correlations between environment and association, the results of this analysis were discussed and the ecological conditions for each sampling station were assessed. The associations were similar in composition over the entire catchment area, and indicated on the whole water of good quality. Points of pollution were detected, but were generally localised and the effects of the pollution were soon removed. Only the Waterval River showed evidence of more constant pollution. The associations provided evidence for some seasonal variation in their composition. Finally in Part 3 the systematics and taxonomy of the diatoms in the Vaal Dam catchment area are discussed. References are made to the original and more recent descriptions of each species found in this study, and a list of synonyms is given wherever 'possible. Comments on the systematics, taxonomy and autecology of each species are given, and the distribution of the species in South Africa and the Vaal Dam catchment area is discussed. A number of species, varieties and forms have been recorded for the first time in South Africa. During the course of this study 20 species have been described as new to science; the descriptions of some have been published, while the descriptions of the others will be published formally in the future. All species described as new or having interesting features are illustrated in the plates.

Diatoms are single-celled photosynthetic eukaryotes that substantially contribute to global primary productivity. They are also among the most diverse groups of organisms in Antarctica. Biogeographically, Antarctica is divided into three distinct regions including the Sub-Antarctic, Maritime Antarctic, and Continental Antarctic. Recent taxonomic revisions of diatoms within the Sub-Antarctic and Maritime Antarctic Regions have uncovered a number of endemic taxa initially misidentified as cosmopolitan due to species "force-fitting". Within Continental Antarctica, this taxonomic uncertainty has led to confusion about the environmental drivers of limno-terrestrial diatom communities, although this knowledge is important given the use of diatoms as regional bioindicators for environmental change. The purpose of this dissertation is to reevaluate the diatom flora of Continental Antarctica and determine variables that structure their communities within two historically and biologically important localities within East Antarctica; the Vestfold Hills and Windmill Islands. The erection of the genus Sabbea was performed to accommodate a long-misidentified species, Sabbea adminensis, that occurs within the Vestfold Hills and McMurdo Sound Region where it had been the source of taxonomic confusion since the...

The occurrence of some diatoms depends on degree of pollution and water quality. Due to this attribute are diatoms used as indicators for the environmental bioassessment. But the maximum use of diatoms for this purpose is complicated by high number of species which are defined based on the ultrastructural morphological features which are indistinguishable without the electron microscope. The aims of this study were to find out the influence of environmental factors, types of habitat and geography on the structure of diatom community. And find out if richness of higher taxonomic levels is correlated with species richness, in this case if it responds with the genetic diversity within diatom species complex Frustulia crassinervia-saxonica. In this study, 49 permanent slides from natural samples were analyzed. Samples were taken from benthos of different types of freshwater habitat - lakes, dams, pools, peat bogs, stream, wet wall on diverse localities in Europe, Canada, Greenland, Chile and New Zealand. In all slides were counted 300 cells which were determined based on the morphological features on genera level. Altogether 43 benthic genera were identified. The results of this thesis showed that number of genera correlated with pH gradient but do not correlate with other environmental factors -...

The purpose of this research was to examine the colonization process and relationship of physico-chemical parameters to diatom and protozoan communities colonizing polyurethane foam (PF) artificial substrates in lentic habitats. This was the first study to utilize multivariate techniques for comparison of protozoan and diatom communities The following hypotheses were examined in this study: 1. diatom and protozoan species accrual is similar because the organisms are approximately the same size and share similar ecological conditions, 2. protozoan assemblages are influenced by the physicochemical parameters of their environment, and 3. diatoms and photosynthetic protozoans are more closely related to the physico-chemical parameters of their environment than are the protozoans of all trophic groups. PF substrates were placed in the littoral zone of lentic habitats. Substrates were sampled through a time series and examined for their diatom and protozoan species' presence-absences. The first hypothesis was tested by using the MacArthur-Wilson equilibrium model and by fitting the data to the model by non·linear least squares regression. Protozoan species accrual fit the model in most cases, while diatom species accrual did not. The second part of the research dealt with five lentic habitats in northern lower Michigan which were sampled as described above and concurrent with organismal sampling several physico-chemical parameters were sampled. These environmental parameters included pH, alkalinity, conductivity, temperature, and concentrations of dissolved oxygen, chloride, silica, ammonia, and total and ortho-phosphate. Protozoan communities were examined using reciprocal averaging ordination. It was found that the bog and marsh had distinct communities, while the three lakes did not. Several physicochemical parameters and factors correlated significantly with axes generated by samples in species space. The final section tested the degree of relationship among diatoms, autotrophic protozoans, and protozoans to the physicochemical parameters and factors. pH had the highest correlations with the first axes for each group. Diatom communities had the greatest degree of relationship to the physico-chemical parameters, evidence for this is provided by the greatest number of correlations between ordination axes and the physico-chemical parameters and factors. / Ph. D. / incomplete_metadata