Oxic methane production by cyanobacteria from the Brazilian Pantanal soda lakes

• Ano de defesa: 2022
• Autor(a) principal: Carvalho, Carolinne Rosa de
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Espectrometria de Massas com Membrana Interna (MIMS); Fosfonato; Membrane Inlet Mass Spectrometry (MIMS); Metadados; Metadata; Metanogênese; Methanogenesis; Phosphonate; Primary production; Produção primária
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/11/11138/tde-12082022-151233/

Methane (CH4) is one of the main greenhouse gases significantly impacting climate changes. The main biogenic source of methane in aquatic environments is archaeal methanogenesis, strictly anaerobic. However, recently, bacterial productions and emissions from highly oxygenated waters have been described in many systems \"Methane Paradox\", and cyanobacteria are considered as one of the main responsible organisms for the called oxic methane production (OMP). The Pantanal is one of the main Brazilian biomes, and the Nhecolândia sub-region encloses saline/alkaline or soda lakes with high levels of salinity, alkalinity (NaHCO3), and pH (>9). Previous studies on the Brazilian soda lakes have correlated elevated methane concentrations with the ones presenting intensive cyanobacterial blooms. In this study, we aim to explore occurrence of oxic methane production in the Pantanal soda lakes using metadata approaches from genomics and metagenomics and isolates bioassays to evaluate cyanobacteria\' potential for direct participation in methane production. Our first study on general OMP pathways applying metagenomics makers was satisfactory efficient to begin our analysis, and reinforced that the lakes with cyanobacterial blooms have higher methane concentrations in their water. Although several pathways were searched, their potential to occur depends on the lake\'s chemical properties. As the \'C-P lyase\' pathway had an interesting potential on lakes with blooms, we performed a deeper analysis, which is reported in chapter two. Here, we in fact verified that there is a microbial community able to use this pathway on the lakes, with factors, such as nitrogen and iron concentration favoring it. However, cyanobacteria are not the main responsible for it, so their role would be probably secondary in this case. Lastly, the study described in chapter three focused on monitoring cyanobacterial strains isolates from the soda lakes. We found methane production exclusive to cyanobacteria and highly correlated to carbon fixation processes. Therefore, we understand in this work that OMP on the soda lakes is unlike to be the major methane production emissions contribution. However, the cyanobacteria are able to produce methane, including the naturally occurring blooms, and also can indirectly influence other sources, which should be investigated for their real effect on greenhouse gas emissions.