Navegando por Autor "SILVA, Fernando Augusto Borges da"

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Acesso aberto (Open Access)
A aplicação da cromatografia gasosa acoplada (GC-FID), isótopos estáveis, palinologia e razão C:N na reconstituição paleoambiental de manguezais do Estado da Bahia e Espírito Santo.
(Universidade Federal do Pará, 2024-07-30) SILVA, Fernando Augusto Borges da; ALBERGARIA-BARBOSA, Ana Cecília Rizzatti de; http://lattes.cnpq.br/2666263256585897; FRANÇA, Marlon Carlos; http://lattes.cnpq.br/8225311897488790; https://orcid.org/0000-0002-3784-7702
Mangroves depend on ideal geomorphological, geochemical, and climatic factors to develop. Brazil, with its highly indented coastline under tropical and sub-tropical climate regimes, presents suitable conditions for the establishment of these ecosystems and distribution. The dynamics of these mangroves can be influenced by factors related to climatic variations and changes in hydrodynamic flow, resulting in modifications in sediment input and the origin of organic matter. These changes can be observed throughout the Holocene in different regions in of the country. On the northeast and southeast coast, the evolution of these ecosystems is associated with fluctuations in relative sea level (RSL) and sedimentary dynamics, while in the southern region, the change in the distribution of mangroves is a reflection of fluctuations in the RSL and climate changes caused by warming global. Recent studies seek to describe the evolution of these environments based on the elemental and isotopic characterization of organic matter. These constitute important tools in paleoenvironmental reconstruction. However, it is necessary to remember that the comparative analysis of the largest possible number of independent parameters is relevant as it adds value to the research and increases the reliability of the data to be analyzed, generating more precise information. Therefore, aiming to unravel the dynamics of organic matter in mangrove environments, as well as understanding movements of expansion and/or contraction of these ecosystems, analyzes of nalkanes were carried out using chromatography (GC-FID), associated with the sedimentary study, pollen data, isotopic and elemental analyses, synchronized with 14C and 210Pb dating, which allowed obtaining information about past biogeochemical processes and environmental changes during the Holocene and Anthropocene in the coastal plain at the mouth of the Itapicuru river (BA) and at the mouth of the Barra Seca and Jucu rivers (ES). Thus, the results of this research are presented in five scientific articles. The first, see chapter III, deals with the expansion of mangroves at the mouth of the Itapecuru river (BA) during the Anthropocene. The second scientific article (chapter IV) deals with the dynamics of mangroves at the mouth of the Barra Seca River, on the northern littoral of the State of Espírito Santo. The third article (chapter V) discusses the palynology tool used to understand the dynamics of coastal vegetation.The fourth article (chapter VI) presents the environmental changes that occurred at the mouth of the Jucu River, on the central coast of the State of Espírito Santo. Finally, the fifth article presents the results of n-alkanes analyses, compared with isotopic, elemental, palynological data, and 14C dating on the coastal plain of the Barra Seca River.
Acesso aberto (Open Access)
Dinâmica dos manguezais no litoral norte do Espírito Santo durante o Holoceno tardio
(Universidade Federal do Pará, 2018-07-01) SILVA, Fernando Augusto Borges da; FRANÇA, Marlon Carlos; http://lattes.cnpq.br/8225311897488790
This work aims to identify the mangrove dynamics in the North coast of Espírito Santo State, close to São Mateus (ES), during the Late-Holocene, using the depositional identification of paleoenvironments and the paleoflora, further a characterization of the sources of sedimentary organic matter and chronological determination of the events in the study area. In order to perform an integrated analysis of the palynological, C-14 data, sedimentological and geochemical data (δ13C, δ15N, C:N and C:S ratio), two sediment cores (MBN and LI-34) were sampled with a peat core sampler. The sedimentary profiles were extracted from mangroves close to the mouth of São Mateus and Barra Seca rivers. The deposits age was around ~2662 cal yr BP, characterized by sand cross laminations (facies Sc), lenticular heterolithic deposits (facies Hl), sand with parallel lamination (facies Sp), wavy heterolytic deposits (facies Hw), flaser heterolithic deposits (facies Hf and Sf), massive sand (facies Sm), sand parallel laminations (facies Smh facies), and mud with parallel laminations (facies Ml), with shells and vegetal fragments. The first facies association (A) consists of an estuarine point bar (~2662 and ~2215 cal yr BP), the second (B) consists of a tidal flat with mangrove/herbs vegetation, since at least ~2215 cal yr BP, and finally the third (C) such as an inlet, a typical distal estuarine channel (~1337 cal yr BP). The geochemical results indicate a mixture of C3 and C4 plants, near the basal portions, with a subsequent predominance of C3 plants towards the top of the samples, besides the presence of organic matter of marine/estuarine. The C:N ratio indicates an oscillation between the aquatic and terrestrial influences, corroborating the values of the C:S ratio (0.02-5.18), which also revealed a mixture of organic matter with marine/aquatic and terrestrial influence. The pollen results showed that the mangrove in this region has been present for at least 2662 cal yr BP, however, changes in its biodiversity have been observed, since currently this ecosystem is colonized mainly by the genus Laguncularia in the region of the mouth of the Barra Seca river, different from previous periods, where there was full development of Rhizophora and Avicennia trees. However, on the mouth of São Mateus river, the genus Rhizophora beginning the mangrove and after Avicennia. Thus, through of this study, it is possible to infer that there were no significant climatic oscillations in this region, however, the stabilization of the relative sea-level during the late-Holocene, as well as the sedimentary dynamics may be controlling the expansion/contraction process of these mangroves.