Avaliação da diversidade de macrófitas aquáticas do rio Paraguai, entre a cidade de Cáceres e Estação Ecológica de Taiamã, Pantanal Mato-Grossense, Brasil

Abstract

The Paraguay River, show spatial and temporal heterogeneity, due it had many secondary channels, oxbow lakes, baías, corixos floodplains, due to the Flood Pulse. Therefore these sets of factors are important for the aquatic macrophyte structuration on floodplains. This research had as main purpose, to evaluate the aquatic macrophyte of the Paraguay River, from Cáceres to Taiamã Ecological Station into the Pantanal of Mato Grosso State. For so, the sample collects were realized between April of 2008 to April of 2009, covering all the hydrological periods. Therefore on each period it was registered the environmental variables, water and air temperature, water level, transparency, pH, dissolved oxygen, water electric conductivity, nitrogen and phosphorous nutrients, calcium, magnesium, potassium, sodium and the biological variable: though the cover of the community of water macrophyte, using a square, where was measured the cover degree according to the visualization. With these data were possible to analyze the composition, abundance, diversity and biological way of life. To shown the results of this study, it was separated into two chapters. The first one, The spatial and temporal dynamics of the aquatic macrophytes in the Paraguay river and in the parental lakes . On this were addressed the spatial and temporal dynamics of the structure and composition of the aquatic macrophyte composition and the environmental variables on many lakes with different degree of connectivity with the Paraguay River. The samples collects were realized on 11 neighboring lakes along the Paraguay river, showing three different kinds of connectivity (unconnected, directly connected to river and indirect connected to the river) While into the river the collects were realized onto ten points, downstream to each lake. The limnologic variables show strong correlation with flood pulse. The Paraguay River show high values of dissolved oxygen and pH during dry period and filling water period and the lakes shown high values of conductivity. The directly connected lakes show big richness of species and biologic way of life, and high values of diversity during all hydrologic periods. Eichhornia azurea, Eichhornia crassipes and Salvinia auriculata were the species who show the biggest abundance mainly in the river. The aquatic macrophyte ordination of the free floating kind showed the biggest abundance during flood in the river and in all hydrological periods in the lakes. The fix floating/emergent dominated on the Paraguay River. The environment studied shown difference during dry and filling period and was grouped on the flood period, when the water levels make the homogenization of the System River, lake and flood plain. The second chapter The functional sectors of the Paraguay river determine the aquatic macrophyte 9 domination , The text show the discussion about the dynamic and the community of the aquatic macrophyte, into three sections of the Paraguay river, which are different in the geomorphology. Where this functional sectors describe the segments of the river differentiated by the changes in the kind of the standard of the Channel flooding area, on the width of the river, in the inclination of the valley, on the sinuosity and on the effect of the confluence of the tributaries with the entry of different water and sediments. The sectors analyzed were: Meander, Straight and transition. On each sector were analyzed the cover the aquatic macrophyte community and the environmental variables of the lakes and the Paraguay river, during dry and flood period. The variable dissolved oxygen (dry period) and water electric conductivity (flood and dry period), analyzed though the ANOVA text, shown exist significant differences between sectors. Analyzing the composition and structure of the aquatic macrophyte community, it was observed that in the meander sector, the lakes, both periods, shown bigger richness and bigger diversity of species in relation to another lakes in another sectors, while the transition sector shown bigger richness and diversity during flood period. Probably these differences are related to the fluvial geomorphology, typical of each sector. The meandric sector is a sector with high sinuosity, which favor a high number of lakes, secondary channels, ancient channels of the river and floodplain. The Paraguay river shown bigger richness and diversity of species on the transition sector, on both hydrological periods, probably due to the presence of many fix floating species and/or emergent. However it is possible to verify that the abundance of Eichhornia azurea and Salvinia auriculata species, on the meandric and transition sectors, enforce the similarity which exists between these lakes during dry period. The lakes of the straight sector are more deep in relation to the another, what probably, favor the high abundance of Salvinia auriculata, make these not similar to another.