The role of suspended sediments in the metabolism of micro and meso scale rivers of Rondonia, Brasil. / O papel dos sedimentos em suspensão no metabolismo de rios de micro e meso-escala no estado de Rondônia.

AUTOR(ES)

Michelle Cristine Cogo

DATA DE PUBLICAÇÃO

2005

RESUMO

Amazonian surface waters, encompassing rivers of distinct orders, from small streams to one of the largest of the world, the Amazon, are important components of the functioning of this continental-scale ecosystem. A paradigm about fluvial systems is that they integrate the processes that occur at their watersheds and, therefore, changes in land use/cover may directly interfere on physical and chemical parameters of the aquatic compartments. In some areas of the Amazon, such as in the state of Rondonia, for example, the landscape has been significantly altered, and the consequences of these changes are still poorly understood. It is well know that the conversion of forests into pastures, a common type of land use change in Rondonia, can cause the compactation of soils and increased erosion rates. At the same time, several studies have demonstrated that suspended sediments can be important sources of carbon and other nutrients to river metabolism. Based on those assumptions, this study aimed the evaluation of the importance of coarse (larger than 63 µm) and fine (smaller than 63 µm and larger than 0,1 µm) suspended sediments on the metabolism of some rivers of Rondonia. This assessment was made through incubations in the dark of samples enriched in sediments, in which the consumption of oxygen indicated respiration rates. In the case of fine suspended sediments, most incubated samples showed increased respiration rates as a result of the concentration of these particles. Coarse suspended sediments, on another side, only favor the increase in respiration rates during the high water period. These results are related to the composition of these sediments. Fine suspended sediments constitute a constant substract for the aquatic metabolism, as a result of their larger surface area and capacity for absorving organic substances and nutrients. Coarse sediments, however, only favor respiration during the high water period, when overland flow carries organic debris from land into the water systems. Although these two fractions of suspended sediments have different relative roles in the metabolism of rivers, it becomes evident from this data that increasing the erosion in the Amazon may affect significantly the metabolism of fluvial systems in this region.

ASSUNTO(S)

organic carbon sediments drainage basin ji-paraná carbono orgânico bacia hidrográfica uso do solo land cover metabolismo ji-paraná river aquatic ecosystems cobertura do solo land use sedimentos metabolism ecossistemas aquáticos rio

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