154 resultados para lotic


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Pós-graduação em Aquicultura - FCAV

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Conselho Nacional de Desenvolvimento Cientifico e Tecnológico (CNPq)

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The freshwater phytoplankton, responsible for a significant part of primary production in rivers and lakes, is of great importance for matter and energy available to other trophic levels of structuring aquatic food chains. In recent decades, the construction of dams, especially for the generation of electricity, produced changes not only in physical and chemical characteristics of rivers, but also in biocoenosis of these ecosystems. Thus, research is needed to expand the basic knowledge about these environments and subsidize actions appropriate conservation and management. Considering that lotic environments are relatively little studied, and the river-reservoir interaction, the work aims to analyze the limnological conditions and assemblies phytoplankton along the gradient established by the Itaipu reservoir and downstream stretch of the Paraná River. During two periods of the year, winter and summer, we analyzed nine sampling stations: one in lentic environment (the dam), six on the Parana River (each 5 km), at the mouth of a river Monday and another at the mouth of the Iguazu river. The phytoplankton community was composed of 315 taxa, with the class Bacillariophyceae most specious. At every point the richness was higher in summer and with a longitudinal trend in the increasing points after falling after the dam and the contribution of the tributaries. The number of taxa common to the three rivers was low in both study periods. The higher taxa can be explained by the variety of environments sampled, different residence times of water and nutrient concentrations, whereas the rivers Iguazu and Monday suffer high human influence. The greater abundance of organisms in the dam, in both periods, it should be the class Cryptophyceae contributing over 75% of total phytoplankton in point. In cluster analysis (composition and abundance)...(Complete abstract click electronic access below)

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Ichthyofaunistic studies aims to broad the knowledge of composition, abundance and distribution of species in certain areas, and when possible, to infer patterns of distribution, as well as extrinsic factors that affect these patterns in space and time. The Paranapanema River suffers the impact of the construction of hydroelectric power plants in cascade system along its main channel, changing the characteristics of lotic to lentic and semi-lentic. These changes affect the entire biocenosis and the surroundings of the reservoir and, in particular, the fish fauna. In this context, the aim of this study was to characterize the fish assemblage in two lakes and stretches of the main channel, located near the outfall of the Paranapanema River, Jurumirim reservoir area, comparing them to their composition and structure, using ecological indices as tools. Fish were caught every three months from April 2011 to January 2013, using gill nets of various mesh openings in four stretches: Environment 1 - Calha Sete Ilhas, Environment 2 - Calha Poço da Pedra, Environment 3 - Lagoa Sete Ilhas and Environment 4 - Lagoa Poço de Pedra. After the capture, the specimens were identified and biometric analysis was performed (total and standard length weight). We captured 4,006 individuals belonging to four orders and 34 species, 31 native species and three non-native species. In abundance (n) and number of species (S), there was a predominance of Characiformes (57 %) followed by Siluriformes (31%). Overall, most of the species was constant concerning the frequency of capture. The five most representative species in abundance were Schizodon intermedius, Cyphocarax modestus, Pimelodus maculatus, Hoplosternum littorale and Serrasalmus maculatus, contributing with 60% of total individuals captured. Regarding the stretches, these species present diversity (H'), evenness (E), dominance (D) and richness (d) of similar species, since the abundance was higher in ...

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Species of colonial green algae from 10 Conservation Units from the Southern Brazil were surveyed. The samplings were carried out in 105 stream reaches, consisting of 10 m length transects. In addition to biological data, some environmental variables were measured: depth, current velocity, water temperature, turbidity, specific conductance, pH, dissolved oxygen and nutrients (total nitrogen and orthophosphate). Three species of colonial green algae [Bohlin Ecballocystis pulvinata var. pulvinata, Tetraspora gelatinosa (Vaucher) Desvaux and T. lubrica (Roth) C Agard] were recorded and these species were described and illustrated. Based on the environmental data, it was observed some patterns of ecological distribution, including the occurrence of E. pulvinata var. pulvinata in environments with higher water temperature and current velocity values, while Tetraspora species typically occurred in environments with lower total nitrogen, orthophosphate and specific conductance values.

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Two drainage basins located in the mid-southern region of Paraná state were comparatively studied for analysis of limnological characteristics in lotic ecosystems. Ten segments of rivers and streams were evaluated in each basin, from June 4th through to June, 29th , 2007. The following physical and chemical parameters were measured: water temperature, specific conductance, oxygen saturation, pH, turbidity, current velocity and depth. The two drainage basins presented similar nominal values for all parameters investigated. There were significant differences between the two environments in relation to temperature, pH, and oxygen saturation. Cluster analysis revealed five small groups of samplings, each one with particular limnological characteristics. The Principal Components Analysis (PCA) confirmed the difference among the drainage basins. These results suggest an influence of regional and local factors in limnological characteristics of rivers and streams in the studied drainage basins.

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This study records, for the first time, the occurrence of all four male morphotypes in a population of Macrobrachium amazonicum from a continental environment, with an entirely freshwater life cycle. The specimens studied came from the Tietê River, state of São Paulo, Brazil, and were collected in a lotic environment downstream from Ibitinga Dam. This population was compared with other continental populations, including a population from the dam itself, collected in a previous study. Four samples of 30 minutes were taken monthly, using a trap, from January to April 2011. Each male specimen was measured with respect to seven body dimensions as follows: carapace length (CL), right cheliped length (RCL), dactyl length (DCL), propodus length (PPL), carpus length (CRL), merus length (ML) and ischium length (IL). The relative growth was analyzed based on the change in growth patterns of certain body parts in relation to the independent variable CL. The four male morphotypes proposed for the species were found using morphological and morphometric analyses. Different biological characteristics were found between the populations studied. The male population of the lake of Ibitinga and from Pantanal presented mean sizes and number of morphotypes lower than the population studied here. These differences seem to be closely related to ecological characteristics of the environments inhabited by these populations. Our results supported the hypothesis that coastal and continental populations of M. amazonicum belong to the same species.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)