Fluorescência da clorofila a como ferramenta para monitoramento ambiental em restinga
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Data
2024-05-27
Autores
Silva Junior, Romário de Oliveira
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Universidade Federal do Espírito Santo
Resumo
The rupture of the Fundão Dam in 2015 released about 50 million m³ of mining waste into the Rio Doce basin, marking a significant event in Brazil's environmental history. This disaster caused severe impacts on adjacent ecosystems, including the Restinga vegetation, which plays a crucial role in coastal protection and pollutant filtration. This study investigated the long-term ecological impacts of the disaster using chlorophyll a fluorescence (FChl) as a sensitive and precise method to monitor the phytotoxic effects of metal contamination in the Restinga ecosystem. Common herbaceous species in the Restinga—Blutaparon portulacoides, Canavalia rosea, Ipomoea imperati, Ipomoea pes caprae, and Scaevola plumieri—were selected to evaluate temporal changes in metal concentrations in their leaves and the effects on photosynthetic metabolism. The experiments included in situ studies to monitor metal concentrations and their effects on photosynthesis over three years, and ex situ experiments with plants cultivated in greenhouses subjected to different concentrations of formulated nutrient solutions. A gradual increase in metal levels was observed during periods of higher precipitation and Rio Doce flow, with I. pes-caprae showing higher values of the Bioaccumulation Factor (BAF). The plants showed an increase in Photosystem I (PSI) activity to compensate for inhibitory effects on Photosystem II (PSII), particularly during periods of higher contaminant exposure. This adjustment involved increased cyclic electron transport, regulating the energy balance between ATP and NADPH and neutralizing oxidative damage. The stress tolerance mechanisms in situ could be mimicked under different mineral stress conditions, conducted through two ex situ experiments. In the first experiment, the best nutritional solution was determined to investigate different contaminants in Restinga plants. A nutrient solution formulated at 75% ionic strength showed higher accumulation of nitrogen (N), phosphorus (P), and sodium (Na), and changes in chlorophyll a fluorescence in the first ten days of treatment, indicating a rapid photochemical adjustment during the initial days of nutritional alteration. The JIP test parameters stood out for distinguishing between treatments, although the performance indices (PITOTAL and PIABS) did not allow for such distinction, suggesting the action of regulatory mechanisms to maintain energy and avoid photoinhibition. Additionally, a second ex situ study focused on Canavalia rosea, which was cultivated with nutrient solution and subjected to high concentrations of Cu, Mn, and Zn. The results revealed that Cu had the most deleterious effect on photosynthetic attributes, while Zn stimulated protective mechanisms. FChl indicated inhibition of electron transport and increased energy dissipation, evidencing photochemical damage. The increased production of phenolic compounds suggested an antioxidant response to stress caused by these metals. Chlorophyll a fluorescence proved to be an effective tool for monitoring the impacts of mineral waste contamination in the Restinga ecosystem. The Restinga plants developed adaptive mechanisms, such as cyclic electron transport, to mitigate oxidative damage and maintain photosynthetic productivity during mineral stress both in situ and ex situ. This study provides valuable insights for the conservation and rehabilitation of fragile ecosystems affected by environmental disasters
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Contaminação por metais , Monitoramento ambiental , Bioacumulação , Fluorescência da clorofila , Fotoproteção , Restinga , Desastre ambiental , Metal contamination , Environmental monitoring , Bioaccumulation , Chlorophyll fluorescence , Photoprotection , Environmental disaster