Physicochemical features of rivers and lakes in pantanal wetland

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Paraná Basin: Mineral resource potentials in Brazil, Uruguay, and Paraguay

The Paraná Basin is a Western Gondwanan cratonic basin that is better defined as the Paraná depositional site, since it has a diverse history as a basin. Sedimentation started in the Ordovician-Silurian, followed by extensive marine Devonian deposition. A Late Paleozoic/ Triassic facies cycle wedge was clearly built during Pangean time. The Early Cretaceous was characterized by extensive basaltic lava flows immediately before the break-up of Pangea. Following these rifting and drifting processes, the basin's structural framework was totally rebuilt, generating new depositional sites in the Late Cretaceous to Tertiary. Based on more recent data, at least two different basins may be defined during the evolution of what was once considered a unique basin. Nevertheless, even if considered as a single basin, the sedimentary pile of the Paraná Basin has considerable economic potential, until now exploited only rudimentarily, except for its groundwater resources. Aggregates, limestones, clays, industrial sands, gems, dimension stones, hydrocarbons, coal, peat, and uranium are some of the potential mineral resources of this basin. Copyright © 1997 by V. H. Winston & Son, Inc. All rights reserved.

Bayesian and multivariate methods applied to favorability quantification in recôncavo Basin and Ribeira Belt, Brazil

A methodology to define favorable areas in petroleum and mineral exploration is applied, which consists in weighting the exploratory variables, in order to characterize their importance as exploration guides. The exploration data are spatially integrated in the selected area to establish the association between variables and deposits, and the relationships among distribution, topology, and indicator pattern of all variables. Two methods of statistical analysis were compared. The first one is the Weights of Evidence Modeling, a conditional probability approach (Agterberg, 1989a), and the second one is the Principal Components Analysis (Pan, 1993). In the conditional method, the favorability estimation is based on the probability of deposit and variable joint occurrence, with the weights being defined as natural logarithms of likelihood ratios. In the multivariate analysis, the cells which contain deposits are selected as control cells and the weights are determined by eigendecomposition, being represented by the coefficients of the eigenvector related to the system's largest eigenvalue. The two techniques of weighting and complementary procedures were tested on two case studies: 1. Recôncavo Basin, Northeast Brazil (for Petroleum) and 2. Itaiacoca Formation of Ribeira Belt, Southeast Brazil (for Pb-Zn Mississippi Valley Type deposits). The applied methodology proved to be easy to use and of great assistance to predict the favorability in large areas, particularly in the initial phase of exploration programs. © 1998 International Association for Mathematical Geology.

Ticks (Acari: Ixodidae) associated with wild animals in the Pantanal region of Brazil

This paper describes the identification of ticks from wild animals of the Pantanal region in Brazil as part of a comprehensive study about established and emerging tick-host relationships and related pathological aspects. Eighty-one animals were captured (representing 13 species six orders), and ticks were found on 63 (78%). Tick species identified included Boophilus microplus (Canestrini), Amblyomma cajennense (F.), Amblyomma parvum Aragão, Amblyomma pseudoconcolor Aragão, Amblyomma scalpturatum Neumann, Amblyomma nodosum Neumann, Amblyomma ovale Koch, and Amblyomma tigrinum Koch. Dragging from grasslands yielded negative results compared with the high concentration of ticks that were collected from leaves in the forests.

Ticks associated with wild animals in the Nhecolândia Pantanal, Brazil

A study of ticks associated with wild animals was carried out from September 1996 to April 1998 at the Fazenda Alegria (21,000 ha), in the Nhecolândia Pantanal, State of Mato Grosso do Sul, Brazil, a sunken plain bordering the upper Paraguay river, located 19 × 08′S; 56 × 46′W. A total of 81 wild animals (13 species, 6 orders) were captured with the aid of nets, and ticks were found on 63 (78%). Tick species identified included Boophilus microplus (Canestrini), Amblyomma cajennense (F.), A. parvum (Aragão), A. pseudo-concolor (Aragão), A. scalpturatum (Neumann), A. nodosum (Neumann), A. ovale (Koch), and A. tigrinum (Koch). Dragging from grasslands (campos) yielded negative results compared to the high concentration of ticks, mainly nymphs, that were collected from leaves in the forests (capão). Predominance of immature instars (Amblyomma genera) was observed in the end of winter (August-September). Ticks were associated mainly with coatis, deer (Mazama gouazoubira) and anteater, and these animals may play a role in the epidemiology of tick-transmitted pathogens in the Pantanal if one considers their coexistence with local domestic animals.

Lower Permian Sphenopsids from Cerquilho, Northeastern Paraná Basin, Brazil

The Lower Permian sphenopsids Phyllotheca australis Brongniart, 1828, Stephanophyllites sanpaulensis Millan & Dolianiti, 1980a and Paracalamites australis Rigby, 1966b, from the Toca do Índio outcrop in Cerquilho Municipality (northeastern Paraná Basin, Tubarō Supergroup) are redescribed on the basis of newly collected specimens. Some aspects, such as the leafsheath opening angles of the whorls and the foliar transverse to oblique striae or wrinkles, are discussed in detail. Phyllotheca australis and Paracalamites australis are widespread in Gondwana and have no particular stratigraphic or phylogenetic value. Otherwise, the genus Stephanophyllites, although only found in the Paraná Basin and probably in Argentina (Bajo de Véliz Formation, close to the Carboniferous-Permian limit), can have a greater importance on account of some Raniganjia-like characters superimposed to a gross Phyllotheca-like morphology.

Factors affecting fish diversity and abundance in drying ponds and lagoons in the upper Paraná River basin, Brazil

Monthly samples were taken from April 1992 to March 1993 of fish assemblages present in six permanent lagoons and four ponds, fragmented from them during the drought period and during the terminal phases of desiccation, to evaluate changes in their diversity, abundance and dominance. Their relationships with hydrological and environment conditions were examined. A total of 63 fish species were identified. Species composition and abiotic factors were heterogeneous among the different water bodies. The proportion of piscivores and oxygen concentration were the determining factors for structuring the assemblages. The impact of piscivory upon fish diversity was neutral at the beginning and negative at the end of the dry season. In the terminal phase of desiccation, diversity was higher in ponds that contained a moderate proportion of piscivores than in these containing a higher proportion.

The fish fauna in tropical rivers: The case of the Sorocaba river basin, São Paulo, Brazil

A survey was carried out on the fish species in the Sorocaba River basin, the main tributary of the left margin of the Tietê River, located in the State of São Paulo, Brazil. The species were collected with gill nets. After identification of the specimens, their relative abundance, weight and standard length were determined. Up to the present moment there are not any studies that focus this subject in this hydrographic basin. Fifty-three species, distributed in eighteen families and six orders were collected. Characiformes were represented by twenty-eight species, Siluriformes by seventeen species, the Gymnotiformes by three species, Perciformes and Cyprinodontiformes by two species, and the Synbranchiformes by one species. Among the collected species there were two exotic. The most abundant species were Astyanax fasciatus and Hypostomus ancistroides. In relation to total weight the most representative species were Hoplias malabaricus and Hypostomus ancistroides. Cyprinus carpio, Prochilodus lineatus, Schizodon nasutus and Hoplias malabaricus were the most representative species in relation to average weight. Largest standard length were recorded for Sternopygus macrurus, Steindachnerina insculpta, Eigenmannia off. virescens and Cyprinus carpio.

Geogenic factors affecting the selenium(IV) distribution in sediments from Madeira River Basin, Brazil

This investigation was carried out at the Madeira River basin, located in the state of Rondônia, Brazilian Amazon. Sediments from Madeira River between Teotônio and Santo Antônio waterfalls along 25 km upstream from Porto Velho, the capital of Rondônia state, and from nine lakes located around Porto Velho municipality were chemically analyzed for Se (IV) in order to evaluate the main factors affecting the Se(IV) distribution in the environment, Selenite ion was chosen to investigate the selenium behavior in the area, because acid conditions are dominant there. The importance of clays, iron oxides, organic matter and minor refractory minerals was considered in order to explain most of the obtained data.

Dinâmica da ocupação do solo bacia do Rio Itiquira, Mato Grosso, Brasil

The study area corresponds to the basin of the Itiquira river high course, totalling 5,361km2. In this area a study of the environmental dynamics was made, applying SIG techniques and satellite images of the years 1966, 1985 and 1996. In 1966 the areas of natural vegetation (forests and groves) occupied 90.64% of the total of the area, which was diminished to 60.57% in 1985 and to only 36.66% in 1996. In this process, 289,382ha of a total of 485,928ha of natural vegetal covering had been lost. At the same time, the agrarian surfaces (agriculture and pasture) that occupied only 0.52% of the total area in 1966, increased to 34.89% in 1985 and to 59.04% in 1996. In 30 years there was an increase of 313,725ha of cultivated lands, corresponding to about 113 times the land occupation of the year of 1966 (2,798ha). The areas classified as urban show a gradual increase since 1966, from 39ha in 1996 to 58ha in 1985, and to 178ha in 1996. The other classes of soil use and occupation (reforestement areas, uncovered and affected by fire and humid areas) added were smaller than 4,27% in 1996.

Tolerância de perdas de solo na bacia do rio Itiquira, Mato Grosso, Brasil

The geographic area of the present study corresponds to the basin of the Itiquira river high course (Figure 1), in the portion that extends from the tributaries of its source, in the east of the plateau Correntes/Itiquira, in the neighbourhoods the city of Alto Garç as, to the scarp of the São Jerônimo mountain range, toward the west of Itiquira, in the state of Mato Grosso, totalizing 5,361 km 2. The area is placed in the eastern part of the Alto Paraguai basin, in the western portion of the Paraná Sedimentary Basin plateau. Through GIS techniques, it was possible to asses total soil losses from the Itiquira river basin, considering the years of 1966, 1985 and 1996, being based on the Universal Soil Loss Equation. Thus, in 1966 the basin lost 201,546.94 ton of soil, with an average loss of 0.37 ton/ha/year. Considering that the total area of the Itiquira river basin is of 536,100 ha, while in 1985 the soil losses had passed to 1,760,833.40 ton, with an increase of approximately 8.5 times. The average of soil losses in 1985 was of 3.28 ton/ha/year. In 1996 the basin lost 1,662,043.24 ton, with a reduction of only 9.4% in relation to 1985 but, in relation the 1966, the increase continued in the order of 8 times. The average losses per hectare in this year was in the order of 3.10 ton/ha/year (Chart 1). The map of potential of the laminar erosion for 1966 (Figure 3), shows to the highest values in small areas, situated in the northeast of the area, in Alto Garças, with values between 10 the 20 ton/ha/year and some spots in sources of the Itiquira and Ariranha rivers, with values between 1 the 5 ton/ha/year. In a general way, however, the area presents low soil loss for laminar erosion in this year, with inferior values to 1 ton/ha/year. The higher class of erosion, over 10 ton/ha/year, occupied 2,947 ha in 1966. In the year of 1985 (Figure 4), the erosive process spread over the entire studied area, and the class of erosion over of 10 ton/ha/year, already started to occupy 78,437 ha, implying an increase of approximately 27 times in 19 years. A strong increment in the erosive process was noticed in the western part of the area, to along the BR-163 road, exactly where great areas of natural vegetation (open pasture) had been transformed in culture and pasture areas. In the north-eastern part of the area it was also noticed an increment in the erosive process in agreement with the increase of culture areas and reduction of the natural areas, but it was not of so intense form as in the western portion of the area. In the year of 1996 (Figure 5), the class of erosion over of 10 ton/ha/year had diminished for a total of 53.499 ha noticing a retraction of the erosive process in the western part of the area, alongside the BR-163 road. On the other hand, it occurred a strong increment in the northern part of the area, in the neighbourhoods of the city of Alto Garças, alongside the BR-364 road and part of the MT-040 road. In a general way, in the outskirts of the city of Itiquira, in the central part of the area, it was verified an increase of the amount of zones with erosion between 0-1 ton/ha/year, passing to the immediately superior class, of 1-3 ton/ha/year; scarce data of hydrosedimentology in the UHE Itiquira (1999), shows good agreement with the values gotten for the EUPS (Chart 2). Based on the hydric classification proposal for FAO (1967) (Chart 3), it is noticed that areas with high degree of erosion (> 50) in the analysed area are very restricted, occupying 493 ha in 1985 and 332 ha in 1996 (Chart 4). In 1996 appeared as isolated spots in the north of Itiquira and Alto Garças, however beyond limits of the Itiquira river basin. These areas require special cares in its use as agricultural areas. Aiming at identifying and indicating the areas of potential risk of erosion and that need implementation of conservation practices, it was elaborated the map of limit of tolerance to the soil losses. In 1966 (Figure 6), areas with soil losses over of the tolerable were restricted to small spots located in the eastern part of the area, occupying 0.43% of the total of the area; already in 1985 (Figure 7), this percentage passed to 5.86%, spreading for all the area; in 1996 (Figure 8) it is observed a fast reduction of the areas with soil losses over of the tolerance limit, passing 5.43% of the total of the area. All the areas with losses over of the tolerable value must be considered as risk areas and were done in these areas studies for implementation of conservation practices.

Alien fishes in lakes of the Doce river basin (Brazil): Range, new occurrences and conservation of native communities

The present study shows the distribution of alien fish species in tropical lakes in the middle Doce river basin, southeastern Brazil, obtained from a rapid assessment program. The causes for their introductions were sport-fishing improvement in some specific lakes and aquaculture in the studied basin. Presently, these species have a wide distribution occurring in 41 of the 54 lakes studied, representing an actual threat to regional native fish community. The natural connection among lakes and streams during the rainy season and the dispersal mediated by local people are the main invasion agents for alien fishes. The success of these invaders is probably due to absence of pre-existing effective competitors or top-predators in the invaded communities. We consider that the eradication of alien fishes by means of the available management tools may be very difficult due to the large number of lakes invaded and to the wide spectrum of lake conditions and resources exploited by these alien species. We recommend the use of environmental education as a tool to stop the human-mediated dispersion of aliens and to improve conservation of native fish community in lakes where these alien species are not present yet. © 2004 Instituto de Ciências Biológicas - UFMG.

Seed dispersal of Attalea phalerata (Palmae) by Crested caracaras (Caracara plancus) in the Pantanal and a review of frugivory by raptors

We observed Crested caracaras (Caracara plancus) consuming and dispersing fruits of the palm Attalea phalerata at Pantanal, Brazil. We reviewed the literature of seed dispersal by raptors and suggest that raptors may affect seed dispersal by three different paths: secondary seed dispersal by preying on frugivorous birds, primary seed dispersal of ornithocoric fruits and primary seed dispersal of large, lipid-rich fruits. The latter path may be an important long-distance seed dispersal mechanism for large seeds.

Application of GPR in the study of a modern alluvial megafan: The case of the Taquari river in Pantanal wetland, West-Central Brazil

A novel and timely ground penetrating radar (GPR) survey has been carried out in Pantanal from Mato Grosso State, west-central Brazil. Fieldwork was carried out on February/2001 and August/2002 in an attempt to understand avulsion processes that are occurring within Taquari alluvial megafan. The main objectives were to map channel, crevasse and floodplain morphology, as well as active sedimentary bedforms. Many GPR profiles were acquired in the medium and lower Taquari River course. Subaqueous megaripples and exposed sand bars were identified in the medium fan area. Similar features were observed in the lower fan channels, where there were many crevasses in the marginal levees. During the flooding seasons, the flow splays out on to the floodplain, where new distributary channels are being formed. GPR data show that the lower fan, Taquari channel is topographically higher than the adjacent floodplain, thus favoring avulsion as a natural process of river course shifting. GPR data obtained during the wet and dry seasons, together with sedimentology information have been very important in characterizing the fluvial dynamics, and avulsion phenomena. © 2005 Springer Science+Business Media, Inc.

Sedimentation rates in the Corumbataí River basin, Brazil, derived from 210Pb measurements

Activity profiles of excess 210Pb measured in four sediment cores from the Corumbataí River basin, São Paulo State, Brazil, provided an opportunity to evaluate sedimentation rates that are helpful for defining appropriate management strategies for the hydrological resources in the basin. This is because Rio Claro city and other municipalities make extensive use of surface waters for drinking water supply. The radiochemical analysis of the sediment cores yielded apparent sediment mass accumulation rates of between 406 and 1014 mg cm-2 year-1 for secondary drainage lines, whereas an intermediate value of 546 mg cm-2 year-1 was found in the Corumbataí River, the main drainage system of the studied area. These values provided estimates of average linear sedimentation rates of between 3.1 and 16.2 mm year-1 that are compatible with field evidence, with the highest value corresponding with an area characterized by accumulation of sediment.