O sistema estuarino do Delta do São Francisco-SE: análise ambiental com base no estudo de foraminíferos e tecamebas
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Data
2006-05-05
Autores
Semensatto Junior, Décio Luis [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O sistema estuarino do delta do Rio São Francisco, em Sergipe, sob intensas alterações nos últimos anos, consiste de manguezais, canais fluviais e de marés, uma estreita laguna e uma ilha-barreira segmentada por um inlet. Foraminíferos e tecamebas deste sistema foram estudados a partir de um total de 104 amostras coletadas em março de 1996 e março de 2004. A composição e estrutura da microfauna dos dois anos foram comparadas entre si e com os respectivos dados abióticos. Foi revelado um mosaico ecofaciológico, no qual as ecofácies se diferenciaram entre os anos e moveram seus limites como resposta às mudanças hidrodinâmicas e hidrohalínicas processadas no sistema: a) ecofácies Centropyxis-Miliammina fusca (1996) e Centropyxis-Difflugia-Miliammina fusca (2004), tipicamente sob influência de águas oligohalinas fortemente afetadas por descargas fluviais; b) ecofácies Miliammina fusca- Arenoparrella mexicana (1996 e 2004), ocupando domínios oligohalinos com menor influência fluvial; c) ecofácies Ammotium-Arenoparrella mexicana-Trochammina-Miliammina fusca-Ammonia (1996) e Ammotium-Ammobaculites (2004), típicas de ambientes mesopolihalinos; e d) ecofácies Quinqueloculina-Ammonia-Elphidium, associada ao canal lagunar predominantemente poli-euhalino. O reconhecimento do padrão de distribuição microfaunística permitiu delinear o modelo hidrodinâmico operante no sistema, estratégico para o planejamento de ações de contingência em eventuais derramamentos de óleo na região. Tais ecofácies indicam que o sistema se tornou mais doce em 2004. Adicionalmente, representam modelos de estruturação e distribuição microfaunística em estuário não poluído, conforme evidenciam os dados geoquímicos levantados...
The São Francisco river delta estuarine system, in Sergipe State, northeastern Brazil, under intense changes in the last years, consists of mangroves, fluvial and tidal channels, a narrow lagoon and a barrier island segmented by an inlet. Foraminifera and thecamoebians of this system were studied from a total of 104 samples collected in March 1996 and March 2004. The composition and the structure of communities of the two years were compared among themselves and with the respective abiotic data. An ecofaciological mosaic was revealed, in which ecofacies had changed along the years and had shifted its boundaries as a response to hydrodynamic and hydrohalinic changes processed at the system: a) Centropyxis-Miliammina fusca ecofacies (1996) and Centropyxis-Difflugia-Miliammina fusca ecofacies (2004), typically under influence of oligohaline waters strongly affected by fluvial discharges; b) Miliammina fusca-Arenoparrella mexicana ecofacies (1996 and 2004), occupying oligohaline domains under lower fluvial influence; c) Ammotium-Arenoparrella mexicana-Trochammina- Miliammina fusca-Ammonia ecofacies (1996) and Ammotium-Ammobaculites ecofacies (2004), typical from meso-polihaline environments; and d) Quinqueloculina-Ammonia- Elphidium ecofacies, associated to the poli-euhaline lagoonal channel. Recognizing microfaunistic distribution pattern allowed us to delineate the hydrodynamic model operating in the system, which is strategic to plan contingency actions in the case of eventual oil spills in the region. These ecofacies indicate that the system became fresher in 2004. Additionally, they represent structuring and distribution microfaunistic models in a non-polluted estuary, as evidenced by geochemical data; thus, they can be used as a reference to diagnose the impact level of a similar... (Complete abstract, click electronic address below)
The São Francisco river delta estuarine system, in Sergipe State, northeastern Brazil, under intense changes in the last years, consists of mangroves, fluvial and tidal channels, a narrow lagoon and a barrier island segmented by an inlet. Foraminifera and thecamoebians of this system were studied from a total of 104 samples collected in March 1996 and March 2004. The composition and the structure of communities of the two years were compared among themselves and with the respective abiotic data. An ecofaciological mosaic was revealed, in which ecofacies had changed along the years and had shifted its boundaries as a response to hydrodynamic and hydrohalinic changes processed at the system: a) Centropyxis-Miliammina fusca ecofacies (1996) and Centropyxis-Difflugia-Miliammina fusca ecofacies (2004), typically under influence of oligohaline waters strongly affected by fluvial discharges; b) Miliammina fusca-Arenoparrella mexicana ecofacies (1996 and 2004), occupying oligohaline domains under lower fluvial influence; c) Ammotium-Arenoparrella mexicana-Trochammina- Miliammina fusca-Ammonia ecofacies (1996) and Ammotium-Ammobaculites ecofacies (2004), typical from meso-polihaline environments; and d) Quinqueloculina-Ammonia- Elphidium ecofacies, associated to the poli-euhaline lagoonal channel. Recognizing microfaunistic distribution pattern allowed us to delineate the hydrodynamic model operating in the system, which is strategic to plan contingency actions in the case of eventual oil spills in the region. These ecofacies indicate that the system became fresher in 2004. Additionally, they represent structuring and distribution microfaunistic models in a non-polluted estuary, as evidenced by geochemical data; thus, they can be used as a reference to diagnose the impact level of a similar... (Complete abstract, click electronic address below)
Descrição
Palavras-chave
Ecologia aquatica, Biologia marinha, Manguezais - Brasil, Oceanografia biológica, Laguna, São Francisco river - Brazil
Como citar
SEMENSATTO JUNIOR, Décio Luis. O sistema estuarino do Delta do São Francisco-SE: análise ambiental com base no estudo de foraminíferos e tecamebas. 2006. 223 f. Tese (doutorado) - Universidade Estadual Paulista, Instituto de Geociências e Ciências Exatas, 2006.