Magister Scientiae (Biodiversity and Conservation Biology) / Kelp forests are dynamic and productive ecosystems which host large biodiversity of sessile fauna and flora, including diatoms. These microalgae occur at the base of coastal marine food webs and contribute substantially to the productivity of marine ecosystems. Diatoms constitute one of the most common and species-rich groups of both phytoplankton and phytobenthos. Possessing a unique silica cell wall, diatoms play a key role in the global carbon and silicon cycles. As the changes in species composition of diatom communities are a direct reaction to the combination of environmental factors prevailing in their ecosystems, diatom analysis is widely and successfully used in biomonitoring of various environmental conditions and paleoecological reconstructions.

Dissertação (mestrado)—Universidade de Brasília, Departamento de Botânica, 2006. / Submitted by Carolina Campos (carolinacamposmaia@gmail.com) on 2009-11-13T18:16:13Z No. of bitstreams: 1 Simone Mogami Delgado.pdf: 6644298 bytes, checksum: 44e9a894abc4309fedf5e5c8a4e8b1e1 (MD5) / Approved for entry into archive by Guimaraes Jacqueline(jacqueline.guimaraes@bce.unb.br) on 2009-11-15T16:35:48Z (GMT) No. of bitstreams: 1 Simone Mogami Delgado.pdf: 6644298 bytes, checksum: 44e9a894abc4309fedf5e5c8a4e8b1e1 (MD5) / Made available in DSpace on 2009-11-15T16:35:48Z (GMT). No. of bitstreams: 1 Simone Mogami Delgado.pdf: 6644298 bytes, checksum: 44e9a894abc4309fedf5e5c8a4e8b1e1 (MD5) Previous issue date: 2006-05 / O Brasil possui em seu território uma vasta área de recursos hídricos pouco explorada cientificamente em relação à sua biodiversidade, em especial, os sistemas lóticos cobrem uma boa parte da região brasileira, contudo apresentam poucos estudos, principalmente em relação a diatomoflórula. Não obstante, o Distrito Federal (DF) possuí importantes mananciais, dentre eles a bacia do Descoberto que assume vital papel de abastecimento e lazer para a população local. Em vista disso, o presente estudo objetivou contribuir para ampliar o conhecimento florístico das diatomáceas perifíticas da ordem Naviculales do rio Descoberto. As coletas foram realizadas em junho e julho de 2003 (período de seca) e janeiro e fevereiro de 2004 (período de chuva) em cinco estações de amostragem ao longo do curso do rio Descoberto, contando com o total de 17 amostras analisadas taxonomicamente segundo o sistema de Round et al. (1990). Desta forma observou-se para a diatomoflórula (Bacillariophyceae: Naviculales) do rio Descoberto, 111 táxons, distribuídos em 10 famílias e quatro subordens. Foram registradas 42 citações pioneiras para o estado de Goiás e 78 para o Distrito Federal, o que significou 38% e 70% de citações pioneiras, respectivamente. As subordens Diploneidineae e Sellaphorineae foram as menores subordens registradas para a diatomoflórula do rio Descoberto, sendo observadas apenas um táxon para Diploneidineae e 19 táxons para Sellaphorineae. Neidiineae se caracterizou como a segunda maior subordem da Naviculales, possuindo 29 táxons, distribuídos em cinco gêneros e quatro famílias. Dentre todas as famílias que foram registradas, a mais representativa foi Naviculaceae (53 táxons) e, pertencente a esta, o gênero Navicula foi observado com maior riqueza, 35 espécies. Em relação à freqüência de ocorrência, 63% dos táxons foram classificados como comuns; 31%, como raros e 6%, como constantes. O período de seca registrou 109 táxons, enquanto que no período de chuva foram observados 36 táxon. Por fim, tem-se que as estações ajusante da barragem do rio Descoberto (Estações 3, 4 e 5) apresentaram maior riqueza que as anteriores, tanto para o período de seca quanto para o período de chuva, até mesmo para a estação que apresenta maior impacto antrópico (estação 5, a jusante o rio Melchior). _____________________________________________________________________________________ ABSTRACT / Brazil is a country rich in hydric resources whose biodiversity, specially the diatoms is poorly known. This study is a contribution to the knowledge of Naviculales from Descoberto river, Distrito Federal and State of Goiás. A total of 17 samples were taken during the dry (June and July – 2003) and rainy season (January and February – 2004) in five points along Descoberto river. Species identification followed Round et al. (1990) system. A total of 111 taxa distributed in 10 families and four suborders were identified, 42 being new for Goiás State and 78 to Distrito Federal, corresponding to 38% and 70%, respectively of the total of species. During the dry season 109 taxa were collected while only 36 were identified during the rainy season and the downstream river points (3, 4, 5) were richier than the amount points for both seasons (dry and rainy). The only a single taxon of Diploneidineae and 19 of Sellaphorineae were identified, the smallest suborders resitered in this study. Neidiineae was the second largest suborder with 29 taxa, distributed in five genera and four families. Naviculaceae was the family with the greatest number of species (53). Navicula was the genus with the greatest number of species (35). In respect of frequency of species, 63% of the taxa were considered as common, 31% as rare and 6% as constant.

Recent use of molecular methods to revisit taxonomically problematic diatom species revealed severe limitations of morphological species concept. Characterization of diatom species which was based solely on the morphology of their frustules often generated too broad species boundaries which inevitably lead to wrong conclusions about their ecology and distribution. Widespread opinion that many diatom species are cosmopolitan generalists resulted in a theory that dispersal of diatoms is not limited by geographical distance. However, a number of recent studies showed that dispersal of diatoms is governed by the same rules which matter for macroorganisms. Proposed master thesis addresses the topic of diversity and dispersal in diatom species complex Frustulia rhomboides sensu lato in Europe and New Zealand. Results suggest that: (1) although revealed molecular variability in this complex shows clear ecological and biogeographical signal, it is not correlated in morphology. This is another support to general need for adoption of different species concept in diatoms. (2) A considerably uneven ratio in species diversity of genus Frustulia found in ecological similar habitats in Europe and New Zealand supports the idea that diatom dispersal is limited and stressed the need for studies dealing with biogeography.

Submitted by Rosangela Silva (rosangela.silva3@unioeste.br) on 2018-08-14T17:44:03Z No. of bitstreams: 2 Gabriela Medeiros.pdf: 6515149 bytes, checksum: 7e73266c6f85d98e6c864ac4968df558 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-08-14T17:44:03Z (GMT). No. of bitstreams: 2 Gabriela Medeiros.pdf: 6515149 bytes, checksum: 7e73266c6f85d98e6c864ac4968df558 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-02-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Diatoms are commonly used as bioindicators for water quality as they possess an intrinsic relationship with environmental conditions. The Cascavel River (24º57’21'’ S, 53º27’19'’ W) has headwaters primarily within an urban perimeter. Therefore, we evaluated the response of its diatom community relative to environmental changes with the aim of characterizing and comparing three lotic environments across the Cascavel microbasin from distinct landscapes and with distinct physical characteristics. In June of 2016, 10 substrates were collected for periphyton extraction in locations with different uses and soil purposes (conservation, urban, and agriculture respectively). One-hundred and nine intragenic taxa and 30 genera were found. Eunotia and Gomphonema presented elevated and representative richness at all stations, with totals of 14 and 11 respectively. Pinnularia and Navicula (12 and 8 taxa respectively) were significant indicator at the more upstream points; while Encyonema, Achnanthidium and Navicula (5, 5, and 6 taxa respectively) occurred primarily downstream. The sampling stations were quite distinct in their density, species richness, and physical, chemical, and biological characteristics. The PERMANOVA test showed a significant difference between the stations based on the species abundance matrix (F = 5.04, R² = 0.15, p = 0.001), revealing the differences between the sampling stations’ communities. Upstream points within the conservation area possessed greater Eunotia density, which prefers low total nitrogen concentrations and electrical conductivity, which in turn reflects a well-preserved environment. The points in the urbanized area were characterized by high light availability associated with elevated electrical conductivity and high nitrate concentration favoring, thus, the development of cosmopolitan species such as Gomphonema lagenula, Gomphonema exilissimum, and Fragilaria gracillis. The agricultural points exhibited elevated flow, a factor limiting the dispersion of species and favoring the development of species from the genera Achnanthidium and Fragilaria. The variables related to the distribution of the community across the microbasin were flow, dissolved oxygen, electrical conductivity, nitrate, ammonia, and total coliforms, all of which distinguished the environments. Except for spatial self-correlation, there wasn’t a single environmental filtering explanation for the diatom community variation. The abiotic variables differentiated the environment in conjunction with the spatial variation, as along the river, physical characteristics such as depth, water volume, flow, solar incidence, concentration of solids, and temperature varied, directly interfering with the periphytic community’s primary production. / Diatomáceas são comumente utilizadas como bioindicadores da qualidade da água, uma vez que sua ocorrência possui intrínseca relação com as condições ambientais. O rio Cascavel (24º57’21'’ S e 53º27’19'’ W) tem grande parte de suas nascentes dentro do perímetro urbano. Assim, avaliamos a resposta da comunidade de diatomáceas em relação às alterações ambientais com o objetivo de caracterizar e comparar três ambientes lóticos com características físicas e de paisagem distintas, ao longo da microbacia rio Cascavel. Em junho de 2016, foram coletados 10 substratos para extração do perifíton em locais com diferentes usos e ocupação do solo (unidade de conservação, urbano e agrícolas respectivamente). Foram encontrados 109 taxa infragenéricos, e 30 gêneros. Eunotia e Gomphonema apresentam riqueza elevada e representativa em todas as estações, com um total de 14 e 11 taxa respectivamente. Pinnularia e Navicula (12 e 8 taxa respectivamente) foram significativamente indicadores do ponto mais a montante; enquanto Encyonema, Achnanthidium e Navicula (5, 5 e 6 táxons respectivamente) ocorrem principalmente em pontos a jusante. As estações de amostragem foram significativamente distintas quanto a densidade, riqueza de espécies e características físicas, químicas e biológicas. O teste de PERMANOVA mostrou diferença significativa entre as estações com base na matriz de abundância das espécies (F = 5.04, R² = 0.15, p = 0.001), evidenciando a diferença entre as comunidades das estações de amostragem. Os pontos a montante dentro da unidade de conservação foram os com maior densidade de espécies de Eunotia, as quais que possuem preferência por baixas concentrações de nitrogênio total e condutividade elétrica, refletindo um ambiente mais preservado. Os pontos em área urbanizada caracterizaram-se por alta disponibilidade de luz associada à elevada condutividade elétrica e à alta concentração de nitrato favorecendo, portanto, o desenvolvimento de espécies cosmopolitas tais como Gomphonema lagenula, Gomphonema exilissimum e Fragilaria gracillis. Pontos em área agrícola exibiram vazão elevada, fator limitante para a dispersão das espécies, e favoreceram o desenvolvimento de espécies dos gêneros Achnanthidium e Fragilaria. As variáveis relacionadas com a distribuição da comunidade ao longo da microbacia foram vazão, oxigênio dissolvido, condutividade elétrica, nitrato, amônio e coliformes totais, distinguindo os ambientes. Exceto pela autocorrelação espacial, não houve uma explicação única de filtragem ambiental para a variação da comunidade de diatomáceas. As variáveis abióticas diferenciaram o ambiente em conjunto com a variação espacial, uma vez que ao longo do rio, características físicas como profundidade, volume de água, vazão, incidência solar, concentração de sólidos e temperatura alteram-se, interferindo diretamente na produção primária da comunidade perifítica.

Objetivou-se, no presente estudo, avaliar a ação de extratos orgânicos e frações de plantas com atividade inseticida, bem como, a associação de extratos orgânicos brutos com terra de diatomácea no controle de Sitophilus zeamais Mots. (Coleoptera: Curculionidade), em milho armazenado. Os extratos foram obtidos por meio de maceração em solventes orgânicos (hexano, diclorometano e etanol), em ordem crescente de polaridade, das seguintes estruturas e espécies vegetais: ramos, folhas e sementes de Annona montana e de A. mucosa; ramos de Aristolochia cf. paulistana e folhas e ramos de Casearia sylvestris. No screening visando à identificação dos extratos mais promissores, verificou-se que os extratos de sementes de A. mucosa e de A. montana, em hexano e diclorometano, seguido pelos extratos de folhas das mesmas espécies, em hexano, foram os tratamentos mais promissores, os quais foram, então, selecionados para os ensaios seguintes. Entre os extratos promissores, os obtidos de sementes de A. mucosa em hexano e em diclorometano foram os que apresentaram os menores valores de concentração letal média (CL50) (110,28 e 149,79 ppm, respectivamente). Observou-se, ainda, pequena variação no tempo letal médio (TL50) (4,14 a 6,10 dias) dos extratos selecionados. Os extratos de sementes de A. mucosa, tanto em hexano como em diclorometano, apresentaram efeito de contato sobre S. zeamais, via aplicação tópica, entretanto, nenhum dos extratos selecionados apresentou efeito inseticida via contato em superfície contaminada (papel filtro). Verificou-se, ainda, que os extratos em hexano e em diclorometano de sementes de A. mucosa apresentam pequena redução na atividade inseticida após 56 dias de armazenamento, sendo estes os extratos com maior efeito residual quando aplicados em grãos de milho visando ao controle de S. zeamais. Na associação de terra de diatomácea com extratos de sementes de A. mucosa, em hexano, e de A. montana, em diclorometano, constatou-se efeito antagônico entre as duas técnicas, quando avaliada a mortalidade dos gorgulhos expostos a tais tratamentos. Posteriormente, com base nos resultados dos ensaios biológicos e na avaliação do perfil cromatográfico dos extratos brutos obtidos por cromatografia em camada delgada (CCD), selecionaram-se os extratos em hexano de sementes de A. mucosa e de A. montana para realização de fracionamentos biomonitorados com a finalidade de se obterem os compostos responsáveis pela bioatividade observada. As frações em diclorometano e em hidroálcool do extrato em hexano de A. montana e de A. mucosa, obtidas por partição líquido-líquido, apresentam efeito inseticida para S. zeamais, sem, contudo, haver diferença entre ambas as frações de cada extrato. Todas as frações bioativas, de ambos os extratos, foram analisadas por CCD, utilizando-se diferentes eluentes e reveladores, por cromatografia líquida de alta eficiência (CLAE) e por ressonância magnética nuclear de hidrogênio (RMN de 1H), e seus resultados mostraram a presença de alcalóides e acetogeninas em todas as amostras analisadas. Assim, possivelmente, compostos de tais classes químicas estão relacionados com a bioatividade observada. / The aim of the present study was to evaluate the effects of organic extracts and fractions of plants with insecticidal activity, as well as, the combination of crude organic extracts with diatomaceous earth in order to control Sitophilus zeamais Mots. (Coleoptera: Curculionidade) in stored corn. The extracts were obtained by maceration technique using organic solvents (hexane, dichloromethane and ethanol) respecting the order of increasing polarity. The species and their structures used were: branches, leaves and seeds of Annona montana and A. mucosa; branches of Aristolochia cf. paulistana and branches and leaves of Casearia sylvestris. In the screening assay, the most promising treatments were extracts from seeds of A. mucosa and A. montana, in hexane and dichloromethane, followed by extracts from leaves of the same species, in hexane. Thus, these extracts were selected for further tests. Among the promising extracts, the seed extract of A. mucosa in hexane and in dichloromethane showed the lowest Lethal Concentration (LC50) (110.28 and 149.79 ppm, respectively). There was a little variation in the Lethal Time (LT50) of the selected extracts ranged between 4.14 and 6.10 days. Seed extracts of A. mucosa, in hexane and dichloromethane, showed a contact effect to S. zeamais via topical application; althought, none of the selected extracts showed insecticidal effects by contact in contaminated surface (filter paper). Both hexane and dichloromethane extracts from seeds of A. mucosa showed a slight decrease in their insecticidal activity after 56 days being these values the highest residual effect among the extracts tested when applied on maize for the control of S. zeamais. The association of diatomaceous earth with A. mucosa seed extracts in hexane, as well as, A. montana in dichloromethane caused an antagonistic effect between the two techniques when evaluated the mortality of weevils exposed to such treatments. Supported by the results of biological tests and the evaluation of the chromatographic profile of crude extracts obtained by thin layer chromatography (TLC), we selected the hexanic extracts of A. mucosa and A. montana seeds to fractionation and identify the responsible compounds by the observed bioactivity. The hydroalcoholic and dichloromethanic fractions of the hexane extract of A. montana and A. mucosa, obtained by liquid-liquid partition, showed insecticidal effects on S. zeamais having no difference among them about the provoked mortalities. All the bioactive fractions of both extracts were analyzed with TLC, using different solvents and developers, by High Performance Liquid Chromatography (HPLC) and Proton Nuclear Magnetic Resonance (1H NMR), and their results showed alkaloids and acetogenins in all samples. Thus, possibly, compounds of these chemical classes may be related to the bioactivity observed.

Objetivou-se, no presente estudo, avaliar a ação de extratos orgânicos e frações de plantas com atividade inseticida, bem como, a associação de extratos orgânicos brutos com terra de diatomácea no controle de Sitophilus zeamais Mots. (Coleoptera: Curculionidade), em milho armazenado. Os extratos foram obtidos por meio de maceração em solventes orgânicos (hexano, diclorometano e etanol), em ordem crescente de polaridade, das seguintes estruturas e espécies vegetais: ramos, folhas e sementes de Annona montana e de A. mucosa; ramos de Aristolochia cf. paulistana e folhas e ramos de Casearia sylvestris. No screening visando à identificação dos extratos mais promissores, verificou-se que os extratos de sementes de A. mucosa e de A. montana, em hexano e diclorometano, seguido pelos extratos de folhas das mesmas espécies, em hexano, foram os tratamentos mais promissores, os quais foram, então, selecionados para os ensaios seguintes. Entre os extratos promissores, os obtidos de sementes de A. mucosa em hexano e em diclorometano foram os que apresentaram os menores valores de concentração letal média (CL50) (110,28 e 149,79 ppm, respectivamente). Observou-se, ainda, pequena variação no tempo letal médio (TL50) (4,14 a 6,10 dias) dos extratos selecionados. Os extratos de sementes de A. mucosa, tanto em hexano como em diclorometano, apresentaram efeito de contato sobre S. zeamais, via aplicação tópica, entretanto, nenhum dos extratos selecionados apresentou efeito inseticida via contato em superfície contaminada (papel filtro). Verificou-se, ainda, que os extratos em hexano e em diclorometano de sementes de A. mucosa apresentam pequena redução na atividade inseticida após 56 dias de armazenamento, sendo estes os extratos com maior efeito residual quando aplicados em grãos de milho visando ao controle de S. zeamais. Na associação de terra de diatomácea com extratos de sementes de A. mucosa, em hexano, e de A. montana, em diclorometano, constatou-se efeito antagônico entre as duas técnicas, quando avaliada a mortalidade dos gorgulhos expostos a tais tratamentos. Posteriormente, com base nos resultados dos ensaios biológicos e na avaliação do perfil cromatográfico dos extratos brutos obtidos por cromatografia em camada delgada (CCD), selecionaram-se os extratos em hexano de sementes de A. mucosa e de A. montana para realização de fracionamentos biomonitorados com a finalidade de se obterem os compostos responsáveis pela bioatividade observada. As frações em diclorometano e em hidroálcool do extrato em hexano de A. montana e de A. mucosa, obtidas por partição líquido-líquido, apresentam efeito inseticida para S. zeamais, sem, contudo, haver diferença entre ambas as frações de cada extrato. Todas as frações bioativas, de ambos os extratos, foram analisadas por CCD, utilizando-se diferentes eluentes e reveladores, por cromatografia líquida de alta eficiência (CLAE) e por ressonância magnética nuclear de hidrogênio (RMN de 1H), e seus resultados mostraram a presença de alcalóides e acetogeninas em todas as amostras analisadas. Assim, possivelmente, compostos de tais classes químicas estão relacionados com a bioatividade observada. / The aim of the present study was to evaluate the effects of organic extracts and fractions of plants with insecticidal activity, as well as, the combination of crude organic extracts with diatomaceous earth in order to control Sitophilus zeamais Mots. (Coleoptera: Curculionidade) in stored corn. The extracts were obtained by maceration technique using organic solvents (hexane, dichloromethane and ethanol) respecting the order of increasing polarity. The species and their structures used were: branches, leaves and seeds of Annona montana and A. mucosa; branches of Aristolochia cf. paulistana and branches and leaves of Casearia sylvestris. In the screening assay, the most promising treatments were extracts from seeds of A. mucosa and A. montana, in hexane and dichloromethane, followed by extracts from leaves of the same species, in hexane. Thus, these extracts were selected for further tests. Among the promising extracts, the seed extract of A. mucosa in hexane and in dichloromethane showed the lowest Lethal Concentration (LC50) (110.28 and 149.79 ppm, respectively). There was a little variation in the Lethal Time (LT50) of the selected extracts ranged between 4.14 and 6.10 days. Seed extracts of A. mucosa, in hexane and dichloromethane, showed a contact effect to S. zeamais via topical application; althought, none of the selected extracts showed insecticidal effects by contact in contaminated surface (filter paper). Both hexane and dichloromethane extracts from seeds of A. mucosa showed a slight decrease in their insecticidal activity after 56 days being these values the highest residual effect among the extracts tested when applied on maize for the control of S. zeamais. The association of diatomaceous earth with A. mucosa seed extracts in hexane, as well as, A. montana in dichloromethane caused an antagonistic effect between the two techniques when evaluated the mortality of weevils exposed to such treatments. Supported by the results of biological tests and the evaluation of the chromatographic profile of crude extracts obtained by thin layer chromatography (TLC), we selected the hexanic extracts of A. mucosa and A. montana seeds to fractionation and identify the responsible compounds by the observed bioactivity. The hydroalcoholic and dichloromethanic fractions of the hexane extract of A. montana and A. mucosa, obtained by liquid-liquid partition, showed insecticidal effects on S. zeamais having no difference among them about the provoked mortalities. All the bioactive fractions of both extracts were analyzed with TLC, using different solvents and developers, by High Performance Liquid Chromatography (HPLC) and Proton Nuclear Magnetic Resonance (1H NMR), and their results showed alkaloids and acetogenins in all samples. Thus, possibly, compounds of these chemical classes may be related to the bioactivity observed.

Les éléments transposables (ET) sont des séquences d‟ADN capables de se déplacer dans les génomes qui les hébergent. Les ET de type mariner (mariner-like element : MLE) ont été caractérisés chez les animaux et chez les plantes à fleurs terrestres mais pas chez les microalgues marines. Dans le présent travail, les MLE ont été recherchés chez les diatomées marines (Bacillariophycées) qui sont des microalgues possédant une enveloppe externe siliceuse. Elles ont colonisé tous les milieux aquatiques et constituent une part majeure du phytoplancton; de ce fait, elles jouent un rôle écologique clé dans le milieu marin.La caractérisation des MLE des diatomées a été réalisée au moyen d‟approches moléculaire et bio-informatique. La présence de MLE dans le génome de 10 espèces de diatomées a été mise en évidence grâce à l‟amplification de fragments d‟environ 380 pb. Ces fragments correspondent à une partie de la séquence conservée codant l‟enzyme responsable de la transposition des MLE : la transposase. L‟analyse des séquences obtenues, par des méthodes phylogénétiques, ainsi que la classification des MLE de diatomées mettent en évidence leur appartenance au groupe des MLE végétaux de la superfamille Tc1-mariner. Néanmoins, les séquences MLE de diatomées divergent considérablement par rapport aux MLE des plantes terrestres. Afin de déterminer si les diatomées ont la capacité de produire la transposase, l‟expression des MLE a été recherchée chez des diatomées soumises à des stress thermiques de courte durée (5 h). Nos travaux montrent que les MLE sont exprimés chez les trois espèces testées incluant la diatomée modèle Phaeodactylum tricornutum dont le génome a été séquencé récemment. L‟expression des MLE des diatomées est variable selon les conditions thermiques et selon les espèces.L‟ensemble de nos résultats suggère que les MLE sont ubiquistes dans les génomes de diatomées et qu‟ils sont présents de manière ancestrale dans la lignée végétale. Les MLE des diatomées forment trois nouvelles sousfamilles de la superfamille Tc1-mariner, la plus répandue des superfamilles d‟ET. De plus, leur expression suggère qu‟il existe des MLE capables de se déplacer dans le génome des diatomées. Si la transposition était vérifiée, ils pourraient alors être développés comme outils de mutagenèse. / Transposable elements (TE) are sequences able to move between two loci in the host genomes. Mariner-like element (MLE) are well characterized in animal and land plant genomes but not in marine microalgae. In this work, we have looked for MLE in marine diatoms (Bacillariophyceae) that are microalgae having a siliceous wall. They have colonized all aquatic environments and are a major component of the phytoplankton, so they play a major role in the ecology of marine environments.To characterize the diatom MLE, molecular and bio-informatics approaches were used. The presence of MLE was detected in ten diatom species which exhibited sequence fragments of about 380 pb. These fragments were identified as a section of the conserved sequence which encodes the enzyme responsible for MLE transposition, the transposase. Phylogeny and classification analysis of these fragments revealed that diatom MLE belong to the Tc1-mariner superfamily, and more precisely to the vegetal MLE group. Nevertheless, diatom MLE sequences diverged from the flowering plant MLE. In order to determine if MLE transposase is produced in diatoms, MLE expression was looked for in diatoms under thermal stresses. Our results showed that diatom MLE were expressed in the three species tested, including the model diatom Phaeodactylum tricornutum which was completely sequenced recently. Diatom MLE expression was dependent on the thermal conditions and on the species.Our results suggest that MLE are widespread in diatom genomes and that they have an ancestral presence in the green lineage. Diatom MLE cluster in three subfamilies in the huge ET Tc1-mariner superfamilly. Finally, the diatom MLE expression detected could reflect the existence of active MLE in diatom genomes. If this hypothesis were verified, it could lead to the development of mutagenesis tools.

iv ABSTRACT Benthic diatoms are due to a number of positive characteristics (such as high abundances, diversified communities, sensitive responses to environmental conditions, capturing long-term changes in the environmental conditions) currently the most commonly used bioindicators of the ecological status of freshwater ecosystems. However, due to problems associated with the use of traditional methods based on species composition (time-consuming identification, presence of species complexes, and requirements for calibration of water quality indexes for geographical regions) searching for alternative methods has been induced. The monitoring of the size structure of diverse diatom communities has been proposed as one of the methods. This approach would mainly eliminate the necessity of time-consuming determination of species. The main purpose of this thesis was therefore to determine the relationship between the size structure of benthic diatom communities, expressed as the relative biovolume, and selected environmental factors (pH, conductivity, habitat type) within freshwater lentic habitats. Furthermore, the variability of biovolume in dependence on environmental variables was compared with the change in species composition. If there would be a similar response pattern of both the biovolume and species...

A traditional species concept of diatoms is based on morphological characters of their siliceous boxes. A multidisciplinary approach to defining species of diatoms has revealed the hidden diversity within the traditionally defined species. But the newly recognized species are morphological variable and indistinguishable by the naked eye. Recent studies showed that different morphotypes show different ecological preferences. This master thesis focuses on the morphology of natural populations of the diatom species complex Frustulia rhomboides which contains both the traditional and the cryptic species, and it engages how the morphology reflects the effects of environmental conditions. Landmark methods of geometric morphometrics were used in order to analyze the morphological variability of diatom frustules of this species complex within various peat bog habitats in the Czech Republic. Selected environmental parameters were measured and the species composition of diatom communities present in the samples was investigated. These data were used to analyze the relationship between the environmental conditions and the cell shape variability within the complex. The analysis revealed the main trends of morphological variability related to different environmental conditions. Two morphotypes characteristic...

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.