Estudo da comunidade de diatomáceas associada à presença de glifosato em biofilmes de cursos d’água do Alto Jacuí, RS, Brasil

• Ano de defesa: 2024
• Autor(a) principal: Ferreira, Guilherme Veiga
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Santa Maria; Brasil; Ciências Biológicas; UFSM; Programa de Pós-Graduação em Agrobiologia; Centro de Ciências Naturais e Exatas
• Palavras-chave em Português: Diatomáceas; Glifosato; RS; Biofilmes; Agrotóxicos; Diatoms; Glyphosate; Biofilms; Pesticides; CNPQ::CIENCIAS BIOLOGICAS
• Link de acesso: http://repositorio.ufsm.br/handle/1/33161

Environmental stress associated with soil and water contamination can directly affect biodiversity and ecosystem functions. The use of biological matrices, such as epilithic biofilms and the associated diatom community, has been increasing over the years, mainly due to their ability to respond quickly and serve as diagnostics for environmental studies. In Rio Grande do Sul, the most widely used herbicide is glyphosate, a toxic compound that, due to incorrect land use and application measures, can affect and alter the composition of epilithic biofilms. Thus, the objective of this study was to characterize the diatom communities present in epilithic biofilms of different environments, relating them to abiotic measurements of water quality, biofilm and vegetation cover. Two river basins were evaluated, one located in the city of Júlio de Castilhos and the other in the city of Quinze de Novembro, both in the central region of Rio Grande do Sul. The basins represent different land use histories. Epilithic biofilm samples were collected in May for both basins and again in December for the Quinze de Novembro basin during 2020. The samples were freeze-dried, oxidized, and permanent slides were made with Naphrax as an embedding medium. For qualitative and quantitative analysis, a Leica DM750 optical microscope with 1000x magnification was used, the species present were identified, and 800 valves were counted on each slide. Species with abundance greater than 0.50% and present in at least two samples were selected for numerical analyses. To compare the diatom assemblages, NMDS, clustering, ANOSIM, and Shannon diversity index analyses were performed for the following comparisons (I) between the two basins, spatially; (II) comparing the first collection between the two basins, temporally; (III) comparing the first and second collections from the Quinze de Novembro basin, temporally. The abiotic data on water, biofilms and vegetation cover were made available by Dr. Gracieli Fernandes, with authorization for use. A total of 144 species were identified, of which the ANOSIM test showed a significant difference only for comparison I (p=0.04). The Quinze de Novembro basin presented the highest diversity index (0.83), with the most representative genera in both basins being Eunotia and Pinnularia (23), followed by Gomphonema (13) and Navicula (12). Glyphosate did not present significance; in contrast, vegetation cover was significant for the composition and structure of biofilms (p=0.01). This work contributes to the discussion of the use of new sampling methods to evaluate aquatic systems influenced by soil-water material transfer. In addition, it provides new taxonomic data and possible new species and occurrences, contributing to floristic surveys, geographic and ecological studies in the state of RS.