The influence of rain in limnological characteristics of Viruá wetlands, Brazilian Amazon

Abstract

Aim: Floodplains occupy a vast area of the Amazon basin but little is known of how their physical and limnological characteristics respond to local and regional ecological processes. In the Negro River basin and its main tributary, the Branco River, there are large areas that are seasonally flooded by water from local rainfall and that are not directly connected to major rivers. One such area is the floodplain of Viruá National Park, in Roraima state, northern Brazil. Methods: The physical and chemical limnological characteristics of 19 plots in this area were monitored over three years (2008)(2009)(2010), with samples collected each year at the beginning and end of the rainy season (May to August). Results: The water bodies studied had low mean values for electrical conductivity (22.0 ± 14.0 µS*cm -1 ) and pH (4.8 ± 0.7), relatively high temperatures (26.6 ± 2.7 °C), and moderate values for dissolved oxygen saturation (43.0 ± 21.5%) and water transparency (87.9 ± 38.7 cm). There was no significant difference in the limnological characteristics of the aquatic plots between the beginning and end of the rainy seasons in 2008 and 2010, but there were significant differences in 2009 due to an atypical rainfall pattern with two short dry spells during the rainy season. Multivariate analysis showed that the highest temporal variations in the limnological characteristics of the aquatic plots resulted from changes in water transparency, and these changes were related to soil type, elevation of the plot, and the particular micro-basins to which they were connected. Conclusions: This dynamic is different from that of most floodplains in the Amazon region, where the limnological pattern is well-defined seasonally and strongly dependent on the direct connectivity to large river systems. Floodplains not connected to large rivers should receive special attention in relation to the expected impacts of global climate change because of their high dependence on local rainfall.Keywords: water transparency, seasonal variation, wetland, Branco River basin, Viruá National Park, temporary ponds. Resumo: Objetivos:As planícies alagáveis da Amazônia ocupam uma vasta área e compreender os padrões das características limnológicas dessas planícies é de grande importância para os processos ecológicos locais e regionais. Na bacia do rio Negro e de seu principal afluente, o rio Branco, há grandes áreas sazonalmente alagadas que são abastecidas principalmente por chuvas locais e não são conectadas diretamente com grandes rios. Uma dessas áreas é a planície alagável do Parque Nacional do Viruá, em Roraima, no extremo norte do Brasil. Métodos: Foram monitoradas as características físicas e limnológicas de 19 parcelas durante três anos (2008 -2010), com coletas realizadas no início e no fim do período de chuvas (maio -agosto). Resultados: Os corpos d'água estudados apresentaram baixos valores médios de condutividade elétrica (22.0 ± 14,0 µS*cm -1 ) e pH (4.8 ± 0.7). A temperatura foi relativamente alta (26.6 ± 2.7 °C) e o oxigênio dis...

Checklist of the ichthyofauna of the Rio Negro basin in the Brazilian Amazon

“…In the middle Rio Negro, for example, there are large floodplains located between the cities of Barcelos and Santa Isabel do Rio Negro as well as in the lower portion of the Rio Branco basin, in Roraima State. These extensive interfluvial regions become flooded during the rainy seasons and, in some areas, may remain flooded even during periods of extreme drought, due to the high level of the water table and the presence of hydromorphic soils (Fittkau et al 1975; Goulding et al 1988; Marshall et al 2011; Vale et al 2014). These areas harbor many species of small fish, several of them of great importance for the ornamental fish trade (Chao et al 2001; Anjos et al 2009).…”

Taxonomic, functional, and phylogenetic perspectives on butterfly spatial assembly in northern Amazonia

“…Amazonian white‐sand forests encompass peculiar vegetation structure and soil properties (Baraloto et al ., ; Damasco et al ., ; Ter Steege et al ., ; do Vale et al ., ). In the dry season, the high temperature and the minimum moisture levels challenge water supply and maintenance, whereas in the rainy season, the open vegetation provides few refuges from heavy rain, wind and inundation.…”

“…Data on flood regime in Viruá were obtained from the Brazilian Biodiversity Research Program (PPBio) database (do Vale et al ., for methods). We sampled butterflies in 12 plots periodically flooded and 12 plots free from flooding effects.…”

“…Throughout the Amazon Basin, ombrophilous forests meet with white‐sand vegetation to form extensive and diverse landscape mosaics (Fine et al ., ; Ter Steege et al ., ). In general, white‐sand forests have lower plant species diversity (Fine et al ., ; Guevara et al ., ), nutrient‐poor soils and are under the influence of periodic flooding due to rainfall (do Vale et al ., ), contrasting with plant‐ and nutrient‐rich non‐flooded ombrophilous forests. As a result, sharp environmental gradients of herbivore resources (host plants, plant juices) and abiotic factors (light intensity, flood regime) are created (Coomes & Grubb, ; Baraloto et al ., ).…”

Characterization of Organic Matter under Different Pedoenvironments in the Viruá National Park, in Northern Amazon

“…In this environment, microbial activity is restricted because of the lack of dissolved oxygen in soils (caused by periodic saturation), nutrient deficiency, slow SOM decomposition, and the presence of recalcitrant plant matter. Due to these characteristics, vast areas of the lower Branco River and the middle Negro River have been called the "Northern Pantanal" (Santos et al, 1993;Vale et al 2014). Thus, knowledge of the physical and chemical characteristics of these environments can provide a benchmark for comparisons with future scenarios.…”