Reconstrução paleolimnológica da eutrofização na represa Guarapiranga com base em multitraçadores biogeoquímicos
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Data
2013-05-27
Autores
Silva, Luciane Fontana da [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A represa Guarapiranga é o segundo reservatório de abastecimento público mais importante para a Região Metropolitana de São Paulo e um dos mais ameaçados pelos impactos antropogênicos. Nós inferimos o histórico da eutrofização nesta represa para o período ~1919-2010, em duas regiões (montante e barragem), usando multitraçadores [(marcadores da geoquímica bulk: COT, NT, PT, isótopos estáveis de δ13C e δ15N) e diatomáceas]. Foram amostrados dois perfis sedimentares (75 e 21 cm, respectivamente) nas regiões de barragem (mais impactada) e na região de montante (menos impactada), os quais foram seccionados a cada 1 cm. As subamostras foram submetidas às análises físicas, químicas (litologia, cronologia pelo 210Pb, densidade, teor de umidade, granulometria, cobre, fósforo total, nitrogênio total, isótopos estáveis [δ13C e δ15N]) e biológicas (análises qualitativa e quantitativa das diatomáceas). De acordo com a cronologia, o perfil 1 (região da barragem) abrangeu o período de ~1919-2010 e o perfil 2 (região de montante), de ~1982-2010. Os dados foram avaliados mediante análises exploratórias multivariadas, de agrupamento e índices de diversidade. Foram inventariados 77 táxons infragenéricos, distribuídos em 29 gêneros. A alteração na composição florística foi caracterizada pelo acentuado declínio no número de espécies e pela redução de elementos bentônicos. A similaridade entre a comunidade pretérita e recente foi baixa e de apenas 12,5%. Marcadas alterações na comunidade de diatomáceas e na geoquímica orgânica ocorreram relativamente simultâneas no tempo, e caracterizaram três fases e quatro subfases paleoambientais no perfil 1. Nas condições iniciais da represa [~1919-1932, subfase 1a] foi detectada vegetação inundada (plantas C3) durante sua fase de construção. Espécies...
Gurapiranga Reservoir is the second most important public water supply in São Paulo Metropolian Region, and also is one of the most threatened by human impacts. We inferred the trophic state history of this large reservoir for the period 1919-2010, in two regions (upstream and dam), using a multiproxy approach [(geochemistry (TOC, TN, TP, C/N, δ15N, δ13C) and diatom assemblages]. Two sediment cores (75 and 21 cm) were sampled, respectively near the dam (the most impacted region) and in the upstream zone (the least impacted region), which were sectioned every 1 cm. Sub-samples were subjected to physical, chemical (lithology, chronology by 210Pb, density, water content, granulometry, copper, total phosphorus, total nitrogen and stable isotope [δ13C and δ15N]) and biological analyses (diatom assemblages). According to geochronology, profile 1 (dam region) covered the period 1919-2010 and profile 2 (upstream region) the period 1982-2010. Data were analyzed by multivariate exploratory analyzes, clustering and diversity indexes. We recorded 77 taxa, distributed in 29 genera. The change in the floristic composition was characterized by a sharp decline in the number of species and the reduction of benthic elements. Similarity between the early and modern assemblages was very low (12.5%). Marked shifts in geochemistry and diatom assemblages enabled identification of three paleolimnological phases and four subphases in sediment profile 1 (dam region). The initial condition was characterized by flooded vegetation (C3 plants) for the construction of the dam [~1919-1932, subphase 1a]. Early diatom assemblage was dominated by benthic, acidophilus and oligotrophic taxa (e.g. Eunotia species), and by high richness and diversity. After ca. 1932 [subphase 1b] there was a shift to dominance by a planktonic species... (Complete abstract click electronic access below)
Gurapiranga Reservoir is the second most important public water supply in São Paulo Metropolian Region, and also is one of the most threatened by human impacts. We inferred the trophic state history of this large reservoir for the period 1919-2010, in two regions (upstream and dam), using a multiproxy approach [(geochemistry (TOC, TN, TP, C/N, δ15N, δ13C) and diatom assemblages]. Two sediment cores (75 and 21 cm) were sampled, respectively near the dam (the most impacted region) and in the upstream zone (the least impacted region), which were sectioned every 1 cm. Sub-samples were subjected to physical, chemical (lithology, chronology by 210Pb, density, water content, granulometry, copper, total phosphorus, total nitrogen and stable isotope [δ13C and δ15N]) and biological analyses (diatom assemblages). According to geochronology, profile 1 (dam region) covered the period 1919-2010 and profile 2 (upstream region) the period 1982-2010. Data were analyzed by multivariate exploratory analyzes, clustering and diversity indexes. We recorded 77 taxa, distributed in 29 genera. The change in the floristic composition was characterized by a sharp decline in the number of species and the reduction of benthic elements. Similarity between the early and modern assemblages was very low (12.5%). Marked shifts in geochemistry and diatom assemblages enabled identification of three paleolimnological phases and four subphases in sediment profile 1 (dam region). The initial condition was characterized by flooded vegetation (C3 plants) for the construction of the dam [~1919-1932, subphase 1a]. Early diatom assemblage was dominated by benthic, acidophilus and oligotrophic taxa (e.g. Eunotia species), and by high richness and diversity. After ca. 1932 [subphase 1b] there was a shift to dominance by a planktonic species... (Complete abstract click electronic access below)
Descrição
Palavras-chave
Guarapiranga, Reservatório de (SP), Aquatic ecology, Ecologia aquatica, Eutroficação, Paleolimnologia, Matéria orgânica, Biogeoquimica
Como citar
SILVA, Luciane Fontana da. Reconstrução paleolimnológica da eutrofização na represa Guarapiranga com base em multitraçadores biogeoquímicos. 2013. 225 f. Tese - (doutorado) - Universidade Estadual Paulista Júlio de Mesquita Filho, Instituto de Biociências de Rio Claro, 2013.