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Paleoreconstrução da Lagoa do Peixinho (Ilha do Pico, Açores) inferida através do estudo de fósseis da família Chironomidae (Diptera)
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| Documento Principal | 1.4 MB | Adobe PDF |
Authors
Abstract(s)
O conhecimento das condições ambientais passadas pode ser obtido através da análise de sedimentos. Uma vez que os sedimentos contêm informação armazenada ao longo do tempo, o seu estudo (paleolimnologia) constitui-se como uma ferramenta poderosa para reconstruir a história das lagoas e das condições ambientais passadas.
Com o objetivo de caracterizar as variações ecológicas da Lagoa do Peixinho (Pico) no passado e reconstruir as condições ambientais a que esteve exposta estudou-se os fósseis das cápsulas cefálicas (C.C.) de quironomídeos num registo sedimentar colhido nesta lagoa que compreende os últimos 2700 anos.
A partir das amostras obtidas foi feito a separação, recolha e identificação dos fósseis das C.C. de quironomídeos, para que, através da composição da comunidade, fosse possível determinar quais as alterações ambientais que ocorreram ao longo do registo. Os resultados obtidos evidenciam quatro zonas sedimentares com distintas composições e abundâncias específicas de quironomídeos que foram relacionadas com eventos ambientais locais e globais.
A zona mais profunda (Zona 1) do registo corresponde a um período onde ocorreram duas erupções vulcânicas responsáveis pelo desaparecimento de espécies que gradualmente recolonizaram o ecossistema e recuperaram a sua abundância.
A Zona 2 é caracterizada pelo aumento da abundância de espécies adaptadas a temperaturas mais elevadas, sendo interpretada como um período quente e húmido, conhecido como Medieval Climate Anomaly (MCA; ca. 1115 BP – ca. 715 BP). Na Zona 3 verificou-se uma substituição das espécies de climas mais quentes por espécies adaptadas a temperaturas mais baixas. Esta zona corresponde ao período mais frio e seco é denominado de Little Ice Age (LIA; ca. 715 BP – 165 BP). Nesta zona surgem alterações nos quironomídeos que dão indicações de alterações antrópicas do coberto vegetal da bacia da lagoa do Peixinho, com a presença de taxa indicadores de erosão.
No período mais recente, correspondente à Zona 4, verificou-se uma grande alteração na composição e abundância de quironomídeos, resultante, provavelmente, da introdução de peixes na lagoa, do aumento das atividades agrícolas e do aquecimento global.
ABSTRACT: Knowledge of past environmental conditions can be obtained through sediment analysis. Since sediments integrate information from various zones and processes of lacustrine ecosystems their study (paleolimnology) is a powerful tool to reconstruct the history of the lakes and the environmental conditions to which they were subjected. In order to characterize past ecological variations of the Peixinho lake (Pico) and reconstruct the environmental conditions to which it was exposed in the last 2700 years, a study was performed with chironomid fossils (cephalic capsules) that were preserved in the sedimentary record of this lake. The samples of fossilized chironomid cephalic capsules were separated, collected and identified, so that through the composition of the community, it would be possible to determine the environmental changes that occurred throughout the record. The results showed four sedimentary zones with distinct compositions and specific abundances of chironomids that were related to local, regional and global environmental events. The deepest zone (Zone 1) of the record corresponds to a period in which two volcanic eruptions took place and were responsible for the disappearance of species that gradually recolonized the ecosystem and regained their abundance. Zone 2 is characterized by an increase of the abundance of species adapted to higher temperatures and is interpreted as a warmer and humid period known as Medieval Climate Anomaly (MCA; ca. 1115 BP – ca. 715 BP). In Zone 3 there was a substitution of species of warmer climates for species adapted to lower temperatures. This period corresponds to the colder and drier period called Little Ice Age (LIA; ca. 715 BP – 165 BP). In this zone, there were changes in the chironomids assemblages that give indications of anthropogenic changes in the vegetation cover of the basin of the Peixinho lake, with the presence of taxa that indicate erosion. In the most recent period, corresponding to Zone 4, there was a great change in the composition and abundance of chironomids, probably due to the introduction of fish into the lake, the increase in agricultural activities and more recently the global warming.
ABSTRACT: Knowledge of past environmental conditions can be obtained through sediment analysis. Since sediments integrate information from various zones and processes of lacustrine ecosystems their study (paleolimnology) is a powerful tool to reconstruct the history of the lakes and the environmental conditions to which they were subjected. In order to characterize past ecological variations of the Peixinho lake (Pico) and reconstruct the environmental conditions to which it was exposed in the last 2700 years, a study was performed with chironomid fossils (cephalic capsules) that were preserved in the sedimentary record of this lake. The samples of fossilized chironomid cephalic capsules were separated, collected and identified, so that through the composition of the community, it would be possible to determine the environmental changes that occurred throughout the record. The results showed four sedimentary zones with distinct compositions and specific abundances of chironomids that were related to local, regional and global environmental events. The deepest zone (Zone 1) of the record corresponds to a period in which two volcanic eruptions took place and were responsible for the disappearance of species that gradually recolonized the ecosystem and regained their abundance. Zone 2 is characterized by an increase of the abundance of species adapted to higher temperatures and is interpreted as a warmer and humid period known as Medieval Climate Anomaly (MCA; ca. 1115 BP – ca. 715 BP). In Zone 3 there was a substitution of species of warmer climates for species adapted to lower temperatures. This period corresponds to the colder and drier period called Little Ice Age (LIA; ca. 715 BP – 165 BP). In this zone, there were changes in the chironomids assemblages that give indications of anthropogenic changes in the vegetation cover of the basin of the Peixinho lake, with the presence of taxa that indicate erosion. In the most recent period, corresponding to Zone 4, there was a great change in the composition and abundance of chironomids, probably due to the introduction of fish into the lake, the increase in agricultural activities and more recently the global warming.
Description
Dissertação de Mestrado, Biodiversidade e Biotecnologia, 27 de fevereiro de 2018, Universidade dos Açores.
Keywords
Chironomidae (Diptera) Lagoas (Ilha do Pico) Macroinvertebrados Paleolimnologia Peixinho Lake (Ilha do Pico) Paleolimnology
Pedagogical Context
Citation
Pimentel, Christopher James. “Paleoreconstrução da Lagoa do Peixinho (Ilha do Pico, Açores) inferida através do estudo de fósseis da família Chironomidae (Diptera)". 2018. 39 p.. (Dissertação de Mestrado em Biodiversidade e Biotecnologia). Ponta Delgada: Universidade dos Açores, 2017. [Consult. Dia Mês Ano]. Disponível em www:<http://hdl.handle.net/10400.3/4653>.