Lipídios como indicadores de processos biogeoquímicos em sedimentos da margem continental do Estado do Rio de Janeiro

• Autor(a) principal: Cordeiro, Lívia Gebara Muraro Serrate
• Data de Publicação: 2011
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/14256
• topic: Sedimentary organic matter; Molecular markers; Lipids; Submarine canyons; Campos basin; Matéria orgânica sedimentar; Marcadores moleculares; Lipídios; Cânions submarinos; Bacia de Campos; Campos, Bacia de (RJ) - Análise de sedimentação; Lipídios; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::QUIMICA ORGANICA

This study is part of the Habitats Project - Campos Basin Environmental Heterogeneity - coordinated by CENPES/PETROBRAS, a multidisciplinary project that considers environmental characterization of the different features and habitats of the Brazilian South-Eastern continental margin. The aim of this thesis was to investigate the processes related to the origin, transport and accumulation of organic matter (OM) in sediments of the continental margin of the Campos Basin (RJ).To this end, the elemental composition of organic matter (carbon and nitrogen) - determined by dry combustion - and lipids (sterols, alcohols and fatty acids) - determined by GCMS and GC-FID - were considered. It was analyzed 215 samples of surface sediment (0-2 cm depth) collected in two samplings (dry and rainy seasons of 2008/2009), distributed over 12 isobaths (25 to 3000 m) along transects distributed from north to south of the basin. Moreover, it was also considered samples from the 400 to 1900 m isobaths in two submarine canyons (Almirante Câmara and Grussaí) in the northern basin. Based on the results, the sedimentary OM continental shelf and slope of Campos Basin was considered to be essentially autochthonous, derived from primary and secondary producers. As a consequence, a significant fraction of OM is reactive and therefore is potentially bioavailable to benthic organisms. However, significant spatial gradients in the quality and quantity of sedimentary OM were observed. In the continental shelf (25 m to 150 m depths), concentrations of lipids were intermediate and there was a predominance of labile sedimentary OM. Exceptions to this general feature were the areas influenced by coastal upwelling and/or sub-surface water intrusion (near Cabo Frio, Cabo de São Tomé and the northern boundary of the basin), where high concentrations of both total organic carbon and lipids were measured. In the upper and middle slope (400 to 1300 m) concentrations of OM were notably higher, but with greater influence of bacterial processes changing their original composition. And in the lower slope (1900 to 3000 m) concentrations of OM were very low and only the lipids more resistant to bacterial degradation were found in measurable concentrations. This suggested the export of materials from the continental shelf along the depth gradient, possibly due to the action of eddies and meanders of the Brazil Current and bottom currents operating in the region. Moreover, for its lability and bioavailability, the OM in the sediment can have a major influence on the ecology of benthic communities, particularly those located on the upper slope. The Almirante Câmara and Grussaí canyons revealed to be regions of OM accumulation and important features on the transport of OM with nutritional value for benthic communities of middle and lower slope.