Navegando por Assunto "Rio Xingu (Médio)"

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Acesso aberto (Open Access)
Composição, riqueza e abundância de espécies de anfíbios na região do médio rio Xingú
(Universidade Federal do Pará, 2009) LIMA, Amanda André; GALATTI, Ulisses; http://lattes.cnpq.br/1040132527458660
This study aimed to identify the amphibian fauna of different habitats in the region of the Middle Rio Xingu. We selected six sites, with samples taken from three breaths, between November 2007 and March 2008, totaling 48 days. We identified six types of habitats in the region: terra-firme forest, seasonally flooded forest (lowland), banks of the river, "pedral”, pond area and area with antropic disturbance. For data collection were used two field sampling methods: pitfall traps with drift fences and visual surveys. The traps were installed only in areas of terra-firme forest, while visual survey was employed in all types of habitats identified. The sampling resulted in the record of 56 species of amphibians and eight species were identified and recorded in previous studies in the area. Species diversity and richness were higher in Caracol site, where the predominance of the terra-firme forest was observed, and lower in the Ilha Grande, which is dominated by seasonally flooded forest. Nine reproductive modes were recorded in the study area, all found in the terra-firme forest and only three in the "pedral" which may reflect the low environment heterogeneity of this area. Two tests of similarity were performed to compare study sites, one for each method of collection. Similarity analysis of the data from visual surveys showed more similarity for species composition between areas of terra-firme forest than the other habitats. Cluster analysis between this study and other surveys conducted in the Amazon grouped the study area to another area also located in the Middle Xingu.
Acesso aberto (Open Access)
Distribuição espaço-temporal de macroinvertebrados aquáticos do médio Rio Xingu, Altamira - PA
(Universidade Federal do Pará, 2008-08-29) JESUS, Allan Jamesson Silva de; CAMARGO-ZORRO, Mauricio; http://lattes.cnpq.br/5423657235023988
The arm of this study was to avaluate the structure of the Benthic Macroinvertebrate assemblage an annual cycle in the Xingu River system, Brazil, measuring the annual secondary production. Two environments were studied in the middle Xingu River: the main channel and an insular lake. In the Lake were investigate the marginal and deeper habitats, with an Ekman-Birge grab. The habitats studied in the main channel were the rapids and the low flowing waters, with a surber net and corer. Were collected 23,432 macrobenthic orgamisms of 43 taxa, 8 classes and 4 phyla. The insects and gastropods compose the 47% and 36% of the total individuals collected, respectively. Rapids show the main taxa diversity. The fluvial low flowing and the marginal lake environments were very similar in species number. The mean density during the low waters was 1,605.75 ind.m-2, and during the flooding season was 894.43 ind.m-2. Leptophlebiidae, Hydropsychidae and Chironomidae were, respectively, the most relative abundants in the River with 29,0%, 21,4% and 13,07%. However, in the Lake Chironomidae (34,6%), Oligochaeta (23,2%), Chaoboridade (14,7%) and Nematoda (14,5%) were the most relative abundants. The macroinvertebrate assemblages differences between habitats were related with oxygen deficit in the waters and nutrients dissolved. The rapids were the more dissimilar habitat between all studied.
Acesso aberto (Open Access)
Diversidade e abundância de algas epilíticas no setor do médio Rio Xingu-PA
(Universidade Federal do Pará, 2010-08-31) BASTOS, Alessandra dos Santos Matni; CAMARGO-ZORRO, Mauricio; http://lattes.cnpq.br/5423657235023988
The periphyton is defined as a complex community of microorganisms (fungi, algae, bacteria, animals), which along with organic and inorganic particles is loosely or firmly adhered to a substrate submerged. Epilithic algae (bedrock) are organims found in environments of rivers and rapids, and other ecosystems. This paper aims to list the diversity of epilithic algae, estimate their relative abundance and frequency of occurrence during an annual cycle. In the main channel of the river Xingu was selected environment rapids of Boa Esperança and localities Arroz Cru. The epilíton was removed, properly identified and preserved in Transeau solution and subsequently analyzed in the laboratory. Were listed 132 species belonging to 78 genera. The total richness observed for Boa Esperança and Arroz Cru, in the months studied were 108 and 101 species respectively. Among all classes, Bacillariophyceae expressed greater contribution in both localities in terms of richness and abundance. The epilithic specie more abundant was Aulacoseira granulata (Ehrenberg) Simonsen (Bacillariophyceae), in the locations studied. In november/2006 and january/2007 (flood) occurred at higher densities mean: 133 and 124 ind.cm-2 in the riverine environment Boa Esperança. In the Arroz Cru was 107 and 90 ind.cm-2. The lowest mean density occurred in march/2007 (filled) with 26 ind.cm-2 in the riverine environment and Boa Esperança in august 2006 (flood) with 15 ind.cm-2 in Arroz Cru. The diversity of epilíton varied among seasons. The precipitation, wind, turbidity and nutrients, possibly influence the variations of abundance, richness and density.
Acesso aberto (Open Access)
Effect of seasonal flooding cycle on litterfall production in alluvial rainforest on the middle Xingu River (Amazon basin, Brazil)
(Universidade Federal do Pará, 2015-08) CAMARGO-ZORRO, Mauricio; GIARRIZZO, Tommaso; JESUS, Allan Jamesson Silva de
The assumption for this study was that litterfall in floodplain environments of the middle Xingu river follows a pattern of seasonal variation. According to this view, litterfall production (total and fractions) was estimated in four alluvial rainforest sites on the middle Xingu River over an annual cycle, and examined the effect of seasonal flooding cycle. The sites included two marginal flooded forests of insular lakes (Ilha Grande and Pimentel) and two flooded forests on the banks of the Xingu itself (Boa Esperança and Arroz Cru). Total litterfall correlated with rainfall and river levels, but whereas the leaf and fruit fractions followed this general pattern, the flower fraction presented an inverse pattern, peaking in the dry season. The litterfall patterns recorded in the present study were consistent with those recorded at other Amazonian sites, and in some other tropical ecosystems.
Acesso aberto (Open Access)
Effect of waterfalls and the flood pulse on the structure of fish assemblages of the middle Xingu River in the eastern Amazon basin
(Instituto Internacional de Ecologia, 2015-08) BARBOSA, Thiago Augusto Pedroso; BENONE, Naraiana Loureiro; RUFFEIL, Tiago Octavio Begot; GONÇALVES, Alany Pedrosa; SOUSA, Leandro Melo de; GIARRIZZO, Tommaso; JUEN, Leandro; MONTAG, Luciano Fogaça de Assis
The structure of fish assemblages in Neotropical rivers is influenced by a series of environmental, spatial and/or temporal factors, given that different species will occupy the habitats that present the most favourable conditions to their survival. The present study aims to identify the principal factors responsible for the structuring of the fish assemblages found in the middle Xingu River, examining the influence of environmental, spatial, and temporal factors, in addition to the presence of natural barriers (waterfalls). For this, data were collected every three months between July 2012 and April 2013, using gillnets of different sizes and meshes. In addition to biotic data, 17 environmental variables were measured. A total of 8,485 fish specimens were collected during the study, representing 188 species. Total dissolved solids, conductivity, total suspended matter, and dissolved oxygen concentrations were the variables that had the greatest influence on the characteristics of the fish fauna of the middle Xingu. Only the barriers and hydrological periods played a significant deterministic role, resulting in both longitudinal and lateral gradients. This emphasizes the role of the connectivity of the different habitats found within the study area in the structuring of its fish assemblages.
Acesso aberto (Open Access)
Influence of the flood pulse on the reproduction of Tocantinsia piresi (Miranda Ribeiro) and Auchenipterus nuchalis (Spix & Agassiz) (Auchenipteridae) of the middle Xingu River, Brazil
(Universidade Federal do Pará, 2015-08) FREITAS, Tiago Magalhães da Silva; PRUDENTE, Bruno da Silveira; OLIVEIRA, Valéria de Albuquerque; OLIVEIRA, Mairo Nazareno Carvalho de; PRATA, Erival Gonçalves; SOUSA, Híngara Leão; MONTAG, Luciano Fogaça de Assis
This study investigates the influence of the flood pulse on the reproductive biology of the auchenipterids Tocantisia piresi (Miranda Ribeiro, 1920) and Auchenipterus nuchalis (Spix & Agassiz, 1829) from the middle Xingu River in the Brazilian state of Pará. The specimens were collected every three months between April, 2012, and January, 2014, covering four distinct periods (flood, ebb, dry, and filling). The sex ratio, size at first maturity, gonadosomatic index, and condition factor were analysed in the two species, and evaluated in the context of the different hydrological periods. A total of 897 specimens of T. piresi were collected, of which 467 were female, and 430 males, and 383 A. nuchalis (286 females and 97 males). In T. piresi, the sex ratio was biased only in the filling and ebb periods, whereas in A. nuchalis, it departed significantly from the expected ratio of 1:1 in all periods, with a predominance of females. The female T. piresi mature at a smaller size than the males, with the opposite of the pattern being recorded in A. nuchalis. In T. piresi, the breeding peak was observed during the low water periods, whereas in A. nuchalis, the peak was recorded in the flood periods. Male and female T. piresi presented similar positively allometric growth rates, whereas in A. nuchalis, growth was negatively allometric, but rates were different between genders. A higher condition factor was recorded in the females of both species during the ebb period. Overall, the results of this study reveals distinct flood pulse effects on the reproductive parameters of the two auchenipterid species studied; for A. nuchalis the spawning seems to happen at the flood period and for T. piresi at the dry season of the middle Xingu River.