Diatoms have been proven to be reliable indicators of water quality in many countries of the world particularly Europe. The potential use of diatoms as indicators of water quality in South Africa was tested in the studies in this document. This study evaluates the potential use of diatom based indices by testing it against a macroinvertebrate index (SASS 5) and evaluating the variation in the index scores of the two indices due to changes in chemical water quality and habitat. It was concluded that the diatom monitoring system performs well as bioindicator of water quality. It was also concluded that it should be used as a complementary system to the much used SASS 5 invertebrate index. This conclusion was made due to the fact that diatoms react more directly to changes in water quality than macroinvertebrates (SASS 5), and macroinvertebrates react more readily to changes in habitat than diatoms. A further part of the study was to assess whether aut-ecological or diversity based diatom indices performed best in South African conditions. This study found that the ecological indices were more sensitive to changes in water quality than the diversity indices. The diatom based indices that performed best as water quality indicators were the specific pollution sensitivity index (SPI) and the biological diatom index (BDI). A standard method for the sampling, preparation and enumeration for diatoms to be used for index score generation is also suggested to ensure the comparability of diatom based index data to facilitate use of such bio monitoring data for management purposes. The main focus of the study was to eliminate some of the obstacles for the use of diatoms as bio indicators of water quality in South Africa. It is believe that this aim has been accomplished in the study. / Thesis (Ph.D. (Environmental Science))--North-West University, Potchefstroom Campus, 2008.

Made available in DSpace on 2016-06-02T19:32:16Z (GMT). No. of bitstreams: 1 DissPICO.pdf: 1390229 bytes, checksum: 6dfd0bd8898ab8895eb69028201e2edf (MD5) Previous issue date: 2005-05-18 / Universidade Federal de Minas Gerais / This work presents original data about aggregate formation by two diatoms, Aulacoseira granulata and Thalassiosira cf. duostra, isolated from Barra Bonita reservoir (Tietê river/ SP). Experiments were performed using a Couette floculator, a machine that promotes laminar fluid shear rates (G, s-1), in which particles in movement with several velocities will shock. Depending on their stickiness, the particles may or may not form aggregates. It was determined that different fluid shear rates can affect distinctly aggregate formation by the two algal species. At shear rates of 10 s-1, T. cf. duostra formed aggregates more intensively than A. granulata. However, aggregate formation by A. granulata was greater at a lower shear rate (3 s-1). The role of exopolysaccharides (EPS) produced by these species in aggregate formation by their cells/chains was also studied. The results showed that these compounds enhanced aggregation by both species. The addition of A. granulata EPS in Barra Bonita water, leaded to the formation of aggregates with larger relative surfaces (µm2) when compared to aggregates formed in Barra Bonita water in the absence of these compounds. This effect could be related to the hydrofobic characteristics of A. granulata EPS, which is composed of large amounts of terminal deoxy-sugars (fucose and rhamnose). When A. granulata chains were added to Barra Bonita water, the formed aggregates presented also larger relative surfaces. This increment leads to greater sinking rates and can promote important consequences for the cycling of matter in Barra Bonita reservoir. / Foi realizado o estudo inédito no país sobre a formação de agregados por duas espécies de diatomáceas isoladas do Reservatório de Barra Bonita (Rio Tietê/ SP), Aulacoseira granulata e Thalassiosira cf. duostra. Para tanto, utilizou-se um floculador Couette, aparelho constituído por dois cilindros que, quando em rotação, promovem a formação de um gradiente de cisalhamento em que partículas movendo-se com diferentes velocidades de deslocamento irão chocar-se. Tais partículas poderão permanecer aderidas ou não, dependendo de sua adesividade (stickiness). Foram determinados o coeficiente de decaimento do número de partículas em suspensão (part · mL-1) e o número de partículas agregadas ao final do experimento. Determinou-se que diferentes taxas de cisalhamento (G, s-1) afetam distintamente a formação de agregados em espécies diferentes de algas. T. cf. duostra apresentou maior agregação quando submetida a G= 10 s-1, apresentando coeficiente de decaimento e número de partículas agregadas aproximadamente 1,5 vez maiores que a G= 3 s-1. A. granulata agregou aproximadamente 1,5 vez mais partículas quando submetida a G= 3 s-1 do que a G= 10 s-1. Os exopolissacarídeos (EPS) produzidos por T. cf. duostra aumentaram mais de duas vezes o número de partículas agregadas no final da fase exponencial de crescimento em relação ao mesmo processo na ausência desses compostos. O EPS produzido por A. granulata aumentou em mais de uma vez a agregação no final da fase exponencial e no início da fase estacionária A adição de EPS produzido por A. granulata à água do Reservatório de Barra Bonita aumentou área relativa dos agregados em relação aos agregados formados sem a adição desses compostos, o que pode estar relacionado ao caráter hidrofóbico desse EPS. A adição das células dessa diatomácea à água do Reservatório também aumentou a área dos agregados formados. O aumento da área dos agregados provoca aumento das taxas de afundamento dessas partículas e representa importantes implicações na ciclagem de matéria no Reservatório de Barra Bonita.

abstract: Sea ice algae dominated by diatoms inhabit the brine channels of the Arctic sea ice and serve as the base of the Arctic marine food web in the spring. I studied sea ice diatoms in the bottom 10 cm of first year land-fast sea ice off the coast of Barrow, AK, in spring of 2011, 2012, and 2013. I investigated the variability in the biomass and the community composition of these sea-ice diatoms between bloom phases, as a function of overlying snow depth and over time. The dominant genera were the pennate diatoms Nitzschia, Navicula, Thalassiothrix, and Fragilariopsis with only a minor contribution by centric diatoms. While diatom biomass as estimated by organic carbon changed significantly between early, peak, and declining bloom phases (average of 1.6 mg C L-1, 5.7 mg C L-1, and 1.0 mg C L-1, respectively), the relative ratio of the dominant diatom groups did not change. However, after export, when the diatoms melt out of the ice into the underlying water, diatom biomass dropped by ~73% and the diatom community shifted to one dominated by centric diatoms. I also found that diatom biomass was ~77% lower under high snow cover (>20 cm) compared to low snow cover (<8 cm); however, the ratio of the diatom categories relative to particulate organic carbon (POC) was again unchanged. The diatom biomass was significantly different between the three sampling years (average of 2.4 mg C L-1 in 2011, 1.1 mg C L-1 in 2012, and 5.4 mg C L-1 in 2013, respectively) as was the contribution of all of the dominant genera to POC. I hypothesize the latter to be due to differences in the history of ice sheet formation each year. The temporal variability of these algal communities will influence their availability for pelagic or benthic consumers. Furthermore, in an Arctic that is changing rapidly with earlier sea ice and snowmelt, this time series study will constitute an important baseline for further studies on how the changing Arctic influences the algal community immured in sea ice. / Dissertation/Thesis / Masters Thesis Biology 2014

Made available in DSpace on 2016-06-02T19:29:14Z (GMT). No. of bitstreams: 1 TeseSES.pdf: 6032170 bytes, checksum: ceb780fd0ed8a11dc78bc4de37e256f0 (MD5) Previous issue date: 2004-03-09 / Financiadora de Estudos e Projetos / Diatoms are amongst the most representative groups of algae in periphytic communities. There is evidence that epilithic diatom assemblages are good indicators of environmental condition since species composition and population abundances change in a more or less predictable way due to pollution or contamination of surrounding waters. The present study investigated limnological characteristics of the Gravataí River, RS, Brazil, following, in the course of two seasons, variations of physical, chemical and biological variables, between September 2000 and August 2002. Spatial and temporal changes in the structure and diversity of epilithic diatom communities were studied in order to be applied as water quality indicators. Sampling of epilithic diatoms from stones used as artificial substrates were carried out every three months, in six sites along the river. Climatic, hydrological physical and chemical variables were simultaneously analyzed. A marked seasonal variability was observed regardig both climate and hydrology. Seasonal variation in temperature was wide, with a range of 20°C between summer and winter seasons and a one order of magnitude variation in river discharge. The results evidenced that Gravataí River has two distinct portions, the Upper-Middle stretch, oligotrophic, oligo-mesosaprobic, being placed in Class 1 or 2 regarding, water uses according to CONAMA classification and the Low Stretch , meso-eutrophic, meso-polisaprobic, Class 2, 3 and 4. There is a gradient descontinuity in the Middle course caused by the discharge of heavily polluted residual waters from Porto Alegre city, resulting on increments of labile organic matter and increase of 3 to 50 times on DBO and faecal coliforms, respectively. A total of 169 taxons were recorded in the epilithic diatom assemblages of Gravataí River during the studied period. The species Cocconeis placentula, Achnanthes sp, Selllaphora seminulum and Eolimna minima were particularly abundant in the autumn, whereas Gomphonema parvulum, Eunotia pectinalis and Navicula radiosa reached the highest densities in the winter. It was also observed that Nitzschia palea and Sellaphora seminulum became gradually dominant and constant species in the Low stretch of the river, for being more tolerant to pollution. The use of a biotic index considering both environmental variables and the relative abundances of species, combined as indicative values, well represented the gradient and temporam changes observed..Comparing these indices with those calculated using the Regional Water Quality Index available from literature gave very similar values evidenced that the model might adequately describe the water quality in the rivers of Rio Grande do Sul. / As diatomáceas constituem um dos grupos de algas mais representativos na comunidade perifítica. Existem evidências de que as mesmas são boas indicadoras das condições ambientais por terem a composição de espécies e a abundância das populações afetadas, de forma mais ou menos previsível, pela poluição ou contaminação das águas em que se desenvolvem. No presente estudo foram investigadas as características limnológicas do rio Gravataí, RS, Brasil, analisando-se suas características físicas, químicas e biológicas ao longo de dois ciclos sazonais, no período de setembro de 2000 a agosto de 2002. Foram estudadas, em detalhe, as variações espaciais e temporais na estrutura e diversidade das diatomáceas epilíticas, visando sua utilização como indicadores da qualidade da água. Amostragens trimestrais das diatomáceas epilíticas associadas a substratos artificiais rochosos foram realizadas em seis estações de amostragens ao longo do rio Gravataí e simultaneamente foram obtidas ou avaliadas as principais variáveis climatológicas e as características físicas e químicas da água. Houve uma marcante sazonalidade, com uma amplitude de variação de temperatura de 20°C, entre verão e inverno, e variação em uma ordem de magnitude na vazão do rio. O rio Gravataí tem dois trechos bastante distintos, o superior-médio, oligotrófico e oligomesosapróbico, com águas que podem ser enquadradas nas Classes 1 e 2, da resolução do CONAMA, n° 20 de 1986 e o trecho inferior, eutrófico, meso-polissapróbico, com águas nas Classes 2, 3 e 4. Existe uma descontinuidade no gradiente no curso médio do rio ocasionado pelo despejo de águas residuárias oriundas de Porto Alegre, resultando em incrementos de matéria orgânica lábil, com aumentos de até 3 e 50 vezes de DBO e coliformes fecais, respectivamente. Foram registrados um total de 169 taxons de diatomáceas epilíticas, ao longo do período de estudo. As espécies Cocconeis placentula, Achnanthes sp, Selllaphora seminulum e Eolimna minima foram tipicamente abundantes no período de outono, enquanto Gomphonema parvulum, Eunotia pectinalis e Navicula radiosa atingiram maiores densidades no inverno. Evidenciou-se, também, que as espécies Nitzschia palea e Sellaphora seminulum tornaram-se gradativamente dominantes e permanentes no trecho inferior do rio, por serem mais tolerantes à poluição. A aplicação de um índice biótico que leva em consideração tanto as características abióticas quanto a abundância relativa das espécies, combinados em valores indicativos, representou adequadamente os gradientes e as variações temporais observadas. Uma comparação dos valores deste índice com aqueles derivados da aplicação de um índice regional revela valores muito similares, evidenciando a adequação do modelo regional para representar a qualidade da água nos rios do Estado do Rio Grande do Sul.

Diatom analysis of basal part of profile PK-1-L contributes to multi-proxy research of former Lake Komořany. At this part of profile radiocarbon dating (dates sediments into Late Glacial and Early Holocene) and LOI (loss on ignition) had been conducted before, of which results have been utilized to more accurate interpretation of diatom analysis conclusions. Apart from diatom valves, presence of stomatocysts of Chrysophyceae has been observed. Having separated diatom valves from 32 sediment samples in intervals 0,4-0,6 cm, permanent preparates have been created. Concentration of valves in a gramme of dry sediment and relative abundance of diatom taxons in each sample have been investigated using light microscopy. In a half of samples subdominants and rare taxons have been observed separately to eliminate the interference from dominant taxons. Cluster analysis based on relative abundances of diatom taxons have been calculated and on its results have been subsequently determined three diatom accumulation zones (DAZ). Moreover trophic and saprobic indices have been calculated and levels of pH, conductivity and concentration of total phosphorus (TP) have been estimated by transfer functions. Even before beginning of Holocene the major shift in composition of diatom communities have happened, to the...