Abstract
Lake Batata is a typical Amazonian clear water lake which has undergone anthropogenic impacts. Thirty percent of its total area has been covered with bauxite tailings. Thus, it is possible to distinguish two areas in this ecosystem: the impacted and the natural. The goal of this research was to study C, N, and P content variation and the values of biomass, length, density, and culm diameter of Oryza glumaepatula at different depths in the natural and impacted areas of Lake Batata. The results obtained in this research suggest that the availability of P and N, in both water and sediment, is lower at the shallow site when compared to the deeper sites. On the other hand, C concentrations decreased as P and N concentrations increased. This may be explained by the structural function of C in aquatic macrophytes. At shallower sites, due to the reduced water column, individuals invest in supporting structures that display high C concentrations. The higher density and biomass of O. glumaepatula at the intermediate site indicate that this area presents the best conditions for germination and establishment of individuals of this species. The chemical composition and biometric parameters of O. glumaepatula have shown that this population has higher spatial variation in the natural area. In the impacted area, the absence of significant variations in N and P concentrations in O. glumaepatula among the three sampled sites promotes higher homogeneity in the stands. The high C:P and N:P ratios indicate that, in the impacted area, P is more limiting to the development of O. glumaepatula than it is in the natural area. The reduced values of biomass and density of O. glumaepatula in the impacted area suggest that the bauxite tailings limit the development of this population.
Highlights
Several species of aquatic macrophytes such as Oryza glumaepatula, Echinochloa polystachya, Paspalum repens, Paspalum pasunculatum, and Luziola spruceana, whose life cycles are influenced by the variation in the water level (Junk & Piedade, 1993; Piedade, 1995) are found in the Amazon region
This species develops as a terrestrial plant; as water level rises, it is covered by water, behaving as an aquatic plant (EnrichPrast, 1998)
As a consequence of these results, C:N, C:P and N:P ratios in O. glumaepatula increased from the deep to the shallow site (Table 1)
Summary
Several species of aquatic macrophytes such as Oryza glumaepatula, Echinochloa polystachya, Paspalum repens, Paspalum pasunculatum, and Luziola spruceana, whose life cycles are influenced by the variation in the water level (Junk & Piedade, 1993; Piedade, 1995) are found in the Amazon region. The species Oryza glumaepatula Steud is found in Amazonian Region lakes and rivers and germinates during the dry phase, in recently exposed lowlands with direct incidence of light. After germination, this species develops as a terrestrial plant; as water level rises, it is covered by water, behaving as an aquatic plant (EnrichPrast, 1998). Oryza glumaepatula colonizes transition zones between areas with periodically flooded vegetation (igapó forest) and those which are permanently flooded
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Schedule a callMore From: Brazilian journal of biology = Revista brasleira de biologia
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