Paulo de Tarso Amorim Castro

Geological control of Podocnemis expansa and Podocnemis unifilis nesting areas in Rio Javaés, Bananal Island, Brazil

The distribution of the nests of Podocnemis expansa (Amazon turtle) and Podocnemis unifilis (yellow-spotted side neck turtle) along the point bars of the Javaes River in Bananal Island, demonstrates a clear preference of these chelonians for differentiated geological environments, in respect to the morphology, grain size or height of the nests in relation to the level of the river. The topographical distribution and the differences in the grain size of the sediments that compose the point bars of the river, originated from the multiple sedimentary processes, and make possible the creation and separation of different nesting environments. Each turtle species takes advantage of the place that presents physiographic characteristics appropriate to the hatching success of their eggs. The superposition of the P. expansa and P. unifilis nest placement areas is rare. The P. expansa nests are concentrated on the central portion of the beaches where successive depositional sedimentary events produced sandy banks more than 3.3 m above the river water level. The P. unifilis nests are distributed preferentially in the upstream and downstream portions along the point bars where the sandy deposits rarely surpass 1.5 m at the moment of laying. P. expansa nests located on the beaches of fine to medium sized sand hatch in a mean of 68 days, while those incubated on beaches of medium to coarse sand size take a mean of 54 days to hatch.

INFLUÊNCIA DE FEIÇÕES GEOLÓGICAS NA MORFOLOGIA DA BACIA DO RIO DO TANQUE (MG) BASEADA NO ESTUDO DE PARÂMETROS MORFOMÉTRICOS E ANÁLISE DE PADRÕES DE LINEAMENTOS

The Tanque River basin, left branch of the Santo Antonio River, middle Doce River valley, has channels and channel segments geologically controlled by faults and lithological contacts. The use of field work, aerial photographs, geological and topographic maps show that lineament patterns and morphometric parameters point to the control of the drainage system by NW-SE and NE-SW faults. The NW-SE faults control the drainage while NE-SW faults seems to be responsible for the sediment retention areas marked by local base water level and meandering pattern of the channels.

Análise morfométrica da bacia do Rio do Tanque, MG - Brasil

The hydrographic basin processes are very representative samples of the Earths relief dynamic therefore, they are frequently studied. However, the most of researches about this geological system are qualitative and, sometimes, insufficient to determinate the basin elements who influence the shape of the planet surface. In other side, the Morphometric Analysis Method is a kind of quantitative approach that reveals typical physic parameters of the studied basin, qualifying the environmental alterations. In this work, we used the Morphometric Analysis about the Rio do Tanque Basin, to determinate their morphologic and sedimentary peculiarities.

Thermal Environment Characteristics of Podocnemis expansa and Podocnemis unifilis Nesting Areas on the Javaés River, Tocantins, Brazil

ABSTRACT Subsurface temperature variation suggests that the thermal environment of giant Amazon river turtle (Podocnemis expansa) nests is influenced by the proximity of the water table and by the nest depth. The difference between vertical temperature gradients along fluvial beaches indicates that nest placement can exert a significant influence on substrate temperature. Temperatures decrease significantly with depth where P. expansa nest on the beach, but do not change with depth in lower beach areas where P. unifilis nest. Daily temperature variation decreases with depth along the entire beach.

Nest Placement of the Giant Amazon River Turtle, Podocnemis expansa, in the Araguaia River, Goiás State, Brazil

The giant Amazon river turtle (Podocnemis expansa) nests on extensive sand bars on the margins and interior of the channel during the dry season. The high concentration of nests in specific points of certain beaches indicates that the selection of nest placement is not random but is related to some geological aspects, such as bar margin inclination and presence of a high, sandy platform. The presence of access channels to high platform points or ramp morphology are decisive factors in the choice of nesting areas. The eroded and escarped margins of the beaches hinder the Amazon river turtle arriving at the most suitable places for nesting. Through the years, changes in beach morphology can alter nest distribution.The giant Amazon river turtle (Podocnemis expansa) nests on extensive sand bars on the margins and interior of the channel during the dry season. The high concentration of nests in specific points of certain beaches indicates that the selection of nest placement is not random but is related to some geological aspects, such as bar margin inclination and presence of a high, sandy platform. The presence of access channels to high platform points or ramp morphology are decisive factors in the choice of nesting areas. The eroded and escarped margins of the beaches hinder the Amazon river turtle arriving at the most suitable places for nesting. Through the years, changes in beach morphology can alter nest distribution.

THE IMPORTANCE OF NIDIFICATION ENVIRONMENT IN THE PODOCNEMIS EXPANSA AND PODOCNEMIS UNIFILIS PHENOTYPES (TESTUDINES: PODOCNEMIDIDAE)

Abstract This work analyses the influence that nest site characteristics have over natural incubation in freshwater turtles Podocnemis expansa and Podocnemis unifilis. Results indicate that neither carapace size nor weight of P. expansa hatchlings depends on environmental characteristics. This suggests that incubation occurs in a homogeneous environment in terms of moisture. On the other hand, embryonic development of P. unifilis is affected by soil moisture, and nests located in very humid beach areas generate smaller hatchlings than nests incubated in drier areas.

Annual and Seasonal Changes in the Structure of Litter-Dwelling Ant Assemblages (Hymenoptera: Formicidae) in Atlantic Semideciduous Forests

We surveyed ant fauna in the leaf litter in an Atlantic Semideciduous forest in the State Park of Rio Doce (PERD). The work aimed to produce basic information about habitat effects on diversity, as well as about how the ant fauna in a such buffered forest habitat, as the litter layer, could respond the climate variation in a short and long term. We sampled two years in two distinct forest physiognomies, which respond to different geomorphologic backgrounds, in dry and rainy seasons. Species composition, richness and abundance of these forests were distinct. However, both forests hosted similar numbers of rare and specialized, habitat demanding species, thus suggesting both are similarly well preserved, despite distinct physiognomies. However, the lower and more open forest was, more susceptible to dry season effects, showing a steeper decline in species numbers in such season, but similar numbers in the wet seasons. The pattern varied between years, which corroborates the hypothesis of a strongly variable community in response to subtle climatic variation among years. The present results are baselines for future long term monitoring projects, and could support protocols for early warnings of global climatic changes effects on biodiversity.

Análise estratigráfica e distribuição do arsênio em depósitos sedimentares quaternários da porção sudeste do Quadrilátero Ferrífero, bacia do Ribeirão do Carmo, MG

The Quadrilatero Ferrifero region, in the State of Minas Gerais, became internationally known due to the exploitation of gold in the eighteenth century. In this paper, we will present background values for arsenic in alluvial sediments from areas that were heavily affected by the exploitation of gold in the past, in the Carmo River Basin. The analyses of the facies succession of the alluvial profiles were carried out in the sedimentary deposits of flood plains, cutbank and alluvial terraces; this being the foundation for obtaining the arsenic background in the facies of the channel and flood plains. From the knowledge of the background obtained by the statistical method, and based on the construction of cumulative frequency curves on a linear scale, geochemical maps were generated in the SIG system. The acquisition of the background values and the geochemical map for arsenic in the Carmo River Basin, representing areas with anomalous concentrations of this element, are essential for the diagnosis and environmental planning of a mining district potentially contaminated by arsenic.

Hydrological stress as a limiting factor of the invasion of Limnoperna fortunei (Dunker, 1857) in the Upper Paraná River (Brazil)

Limnoperna fortunei (Dunker, 1857), is an asiatic mussel that arrived in South America in 1991. Since 2004, we have noticed that the advance of this species in the lower Paranaiba River, a tributary of the Upper Parana River, is slow when compared to the average speed of 240 km/year in the Parana River (middle and lower course). AIM: The goal of this work is to understand what factors are limiting the spread of L. fortunei in this stretch of the Paranaiba River. METHODS: Its occurrence and dispersion were sampled twelve times between March 2006 and November 2007 in the Paranaiba River, including the Sao Simao hydroelectric reservoir. Physicochemical characteristics of the water were analysed, and a Stream Length-Gradient Index calculated for the study area. RESULTS: Adult mussels were easily found attached to the hulls of barges that travel on this stretch of the Parana-Tiete waterway and on vessels that were docked in the harbours of grain exporters located in Sao Simao (GO). However, no larvae or adults were found near the harbours or upstream from them at the Sao Simao hydroelectric reservoir. The pH and concentration of calcium and dissolved oxygen values among lotic habitats and the reservoir were similar: DO values were close to 7 mg.L-1, the average pH was near 7, average values of total Ca ranged between 4 and 6 mg.L-1 and the chlorophyll-a levels were not restrictive to the mussel. CONCLUSION: Physical and chemical water parameters show that habitats were suitable for establishment of the mussel. In addition to a low pressure of propagules, this paper proposes some hydrological variables, such as the energy of the fluvial stretches, expressed by the Stream Length-Gradient Index and changes in flow downstream of the dam as barriers to the establishment of the species, discouraging larval settlement, and decreasing survival and recruitment.

Florística e caracterização de uma área de campo ferruginoso no Complexo Minerário Alegria, Serra de Antônio Pereira, Ouro Preto, Minas Gerais, Brasil

This study presents the floristic inventory of the rupestrian ferruginous field areas located inSerra de Antonio Pereira, in the south-southeast of Quadrilatero Ferrifero region in Ouro Preto, MG. There, two different substratcts were surveyed: the canga couracada, a hard ferruginous laterite, and itabirite rock outcrop. In each substract, 15 sample units (10mx10m) were studied. All the samples units were made with the same slope. The data collected were only restricted to the phanerogam species found in the samples units and surrounding areas. The floristic inventory done at Serra de Antonio Pereira found 182 species united in 47 families, of which 102 species occur inside the sample units and other 80 species in surrounding areas. The richest species families in the samples units were: Asteraceae (14 spp), Poaceae and Orchidaceae (8 spp each), Fabaceae and Melastomataceae (7 spp each), Myrtaceae and Verbenaceae (6 spp each), Cyperaceae, Lauraceae, Rubiaceae and Euphorbiaceae (4 spp each). Both the studied units, canga couracada and itabirite outcrop, showed similarities.