O papel dos podzóis hidromórficos na exportação e bioacumulação de metilmercúrio em igarapés de terra firme na Amazônia Central
Upland forest streams of the Central Amazon are unique aquatic systems that are structurally and functionally different from larger rivers. These small streams have short, unpredictable and multimodal flood-pulses that are influenced by local rainfall. The biogeochemical cycles in these systems are...
| Autor principal: | Vasconcelos, Moema Rachel Ribeiro de |
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| Grau: | Dissertação |
| Idioma: | por |
| Publicado em: |
Instituto Nacional de Pesquisas da Amazônia - INPA
2020
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| Acesso em linha: |
https://repositorio.inpa.gov.br/handle/1/11374 http://lattes.cnpq.br/0102190232694454 |
| Resumo: |
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Upland forest streams of the Central Amazon are unique aquatic systems that are structurally and functionally different from larger rivers. These small streams have short, unpredictable and multimodal flood-pulses that are influenced by local rainfall. The biogeochemical cycles in these systems are almost unknown. Since these systems are relatively unpredictable, long term studies are needed to comprehend their functionality. This study aimed to investigate the role of soil type on the export and bioaccumulation of methyl mercury (MeHg) in upland forest streams of the Central Amazon. Limnological measurements and water samples for MeHg analyses were collected monthly from October 2012 to October 2013 in two headwater streams drained by different kind of soils (podzol/Igarapé da Campina and latossolo/Igarapé Barro Branco) in natural biological reserves in the Central Amazon. Macroinvertebrates and fish for total mercury (THg) determination were collected in April 2012 in both streams. MeHg concentrations in water varied from 0.04 to 0.50 ng/L in the Igarapé da Campina and between 0.02 and 0.04 ng/L in Igarapé Barro Branco. In both sampled streams, MeHg concentrations were negatively correlated with dissolved organic carbon concentrations, and positively correlated with electric conductivity. Physical soil characteristics of the basins and the interaction between mercury and organic matter influenced export mercury to the aquatic system and, consequently, its availability to methylating bacteria. In both streams, MeHg export was highest during the rainy season, probably due to soil leaching, lateral flooding and soil hydromorphism during this period, processes conducive to mercury export and methylation. THg concentrations in omnivorous (Macrobrachium spp.) and carnivorous (Erythrinus erythrinus) organisms were higher in Igarapé da Campina than those in Igarapé Barro Branco. However, concentrations in insectivorous allochthonous (Pyrrhulina cf. brevis) were similar in both basins. The THg levels in omnivores and carnivores, which fed on aquatic food items, reflected the MeHg differences between streams while insectivores, feeding on allochthonous food items, did not. Methyl mercury dynamics in streams were influenced by the physical characteristics of basin soils and by local rainfall seasonality. |