Brazilian Basins Research Articles

Shape diversity of the fish genus Astyanax Baird & Girard, 1854 (Teleostei, Characidae) in adjacent basins

The Neotropical region is highly diverse in fresh water teleost fishes and extends through vast regions of South America. The genus Astyanax comprises small fish found in the tributaries and ditches of the great Brazilian basins, such as the Parana and Sao Francisco Rivers. This group has been ostensibly studied from a chromosomal and molecular point of view but is still involved in problems of phylogenetic location, justifying its position incertae sedis, while having a wide diversity of forms and habitats. Our study counted on the analysis of body shape variations in seven species of the genus Astyanax and in the bimaculatus, fasciatus, and scabripinnis complexes using geometric morphometrics. We obtained images of individuals from different localities in the Parana and Sao Francisco River basins, delineated two-dimensional anatomical landmarks that we then subjected to the generalized Procrustes analysis, and subsequent ordination by principal component analysis and canonical variate analysis. The results showed variation between two large groups, related mainly to variations in body height, indicating the probable existence of different evolutionarily significant units morphologically shaped by the pressure of the environment with what may be incipient speciation.

Mechanical behavior of carbonate reservoirs with single karst cavities

In recent years, operational issues during the exploration of Pre-salt reservoirs have aroused the interest of the Brazilian oil and gas industry in studying karstification and its effect on carbonate reservoirs. Since then, a massive research effort was dedicated to the geology of the Brazilian onshore karstified carbonate formations; however, geomechanical modeling of reservoirs with karstic cavities remains unexplored in the literature. This work analyzes the mechanical behavior of karstified carbonate reservoirs during the hydrocarbon production period. A synthetic case study based on real geologic horizons of a Brazilian basin is carried out to predict the mechanical response of the reservoir and surroundings. The presence of a preexistent cavity developing around the reservoir symmetry axis is postulated. Different scenarios of karstic geometry and filling material are considered. Results focus on reservoir compaction, surface subsidence, and stress paths in regions of interest of the reservoir, caprocks, and cavity wall. Comparative results show that the horizontal extension of the cavity and the compressibility of the filling material play an important role in reservoir integrity. The qualitative results are useful for the oil and gas industry in terms of identifying problematic regions for wells and establishing loading limits. The findings and the preliminary results of this innovative work shall guide further advanced analyses, especially in the area of dolines generation from karstic cavities.

Kerteszia cruzii and extra-Amazonian malaria in Brazil: Challenges due to climate change in the Atlantic Forest

Kerteszia cruzii is a sylvatic mosquito and the primary vector of Plasmodium spp., which can cause malaria in humans in areas outside the Amazon River basin in Brazil. Anthropic changes in the natural environments are the major drivers of massive deforestation and local climate change, with serious impacts on the dynamics of mosquito communities and on the risk of acquiring malaria. Considering the lack of information on the dynamics of malaria transmission in areas across the Atlantic Forest biome, where Ke. cruzii is the dominant vector, and the impact of climate drivers of malaria, the present study aimed to: (i) investigate the occurrence and survival rate of Ke. cruzii based on the distinct vegetation profiles found in areas across the coastal region of the Brazilian Atlantic Forest biome; (ii) estimate the extrinsic incubation period (EIP) and survival rates of P. vivax and P. falciparum parasites in Ke. cruzii under current and future scenarios. The potential distribution of Plasmodium spp. was estimated using simulation analyses under distinct scenarios of average temperature increases from 1 °C to 3.7 °C. Our results showed that two conditions are necessary to explain the occurrence and survival of Ke. cruzii: warm temperature and presence of the Atlantic Forest biome. Moreover, both Plasmodium species showed a tendency to decrease their EIP and increase their estimated survival rates in a scenario of higher temperature. Our findings support that the high-risk malaria areas may include the southern region of the distribution range of the Atlantic Forest biome in the coming years. Despite its limitations and assumptions, the present study provides robust evidence of areas with potential to be impacted by malaria incidence in a future scenario. These areas should be monitored in the next decades regarding the occurrence of the mosquito vector and the potential for malaria persistence and increased occurrence.

Lacustrine versus Marine Oils: Fast and Accurate Molecular Discrimination via Electrospray Fourier Transform Ion Cyclotron Resonance Mass Spectrometry and Multivariate Statistics

The ionizable molecular composition of 36 lacustrine oil samples and 29 marine oil samples from different off-shore Brazilian basins have been screened by ultrahigh-resolution and accuracy Fourier ...

Palynostratigraphy of the Ramon and Solimões formations in the Acre Basin, Brazil

The Acre Basin has a complex geology that is related to the Andean uplift and it still is one of the least understood Brazilian sedimentary basins due in part to difficulties in accessing outcrops. Its geological history is related to several subandean basins including Marañon, Ucayali and Madre de Dios in Peru, and the Solimões Basin in Brazil. These basins have potential for oil and gas which raised interest in the Brazilian oil industry since 1930. During this period, 11 wells were drilled in Acre, one of which is herein studied (2CDST001-AC). Available information from this 2600 m-thick borehole suggested an age spanning from the Albian to the Pliocene. We performed palynological analyses in 29 core-samples spread along the well. Our new data indicated much younger ages, spanning from Eocene to late Miocene together with a middle to late Miocene marine incursion. The palynological assemblage of the Solimões Formation in the Acre basin is similar to that of the adjacent Solimões Basin, but with a much thicker stratigraphic sequence offering a greater potential to unravel the history of western Amazonia during the Cenozoic.

Evaluation of water loss in transit and surface runoff in a Brazilian semi-arid basin

The objective of this work was to propose and evaluate a model to estimate transit water losses and surface runoff in a Brazilian semi-arid basin, fundamental components in the hydrological studies of the region, such as in the verification of hydrological connectivity. The study area was the Orós Reservoir Basin, located in the state of Ceará. The modeling of transit water loss and surface runoff were developed based on the work of Araújo and Ribeiro (1996) and Peter et al. (2014). In the proposed model, the parameter of loss in transit (k) was estimated at 0.027 km-1 for a section of the river basin, and when simulated for other stretches it provided good flow results at the end of the stretch, obtaining an NSE of 82%. The value of the runoff coefficient was estimated at 3% and when evaluating a spatial variation of this coefficient in the basin, the values varied from 2% to 12%, and the use of specialized runoff coefficient (RC) values promoted a higher NSE in the discharge simulation in the basin. It is concluded that the proposed model to estimate transit water losses and surface runoff demonstrated a high efficiency in the simulation of hydrological processes. The basin of Orós reservoir presented a high variability of the coefficient of surface runoff, justifying the need for a greater spatiality of this coefficient in heterogeneous environments.

The 1974 Tubarão River flood, Brazil: reconstruction of the catastrophic flood

Large magnitude floods occur in rare frequency, and most cases result in severe damages. Generally, the representation of extreme hydrological events presents high uncertainties regarding occurrence conditions, and low quality and quantity of data to support the event assessment. In this research, we performed a reconstruction of one historical flood based on flood memory and quantitative data. We developed a hydrological and hydraulic reconstruction of the catastrophic flood in a coastal basin in the southern region of Brazil. This event is among the 300th deadliest hydrological disasters in the globe. According to the data based on qualitative methodologies in combination with historical documents, we created the scenarios and analysed by computational model: precipitation, coastal tide height, wind direction and velocity and, channel depth. This analysis provided the academic community and state officials a further understanding of a critical hydrological disaster originated by a compound event at the Brazilian coastal basin.

Environmental Dynamic Efficiency Of Onshore Oil Fields Located At The Brazilian Coastal Basin

One of the main environmental concerns associated with the exploration and production of oil fields is related to the generation of produced water, this is a strategic challenge for companies since is resposible for the largest share of waste genretared by the oil industry. This theme is presented as multidisciplinary since it is a study with dynamic models in an environmental area linked to the oil industry. Thus, the present work aims to evaluate the performance of dynamic environmental sustainability, from the generation of produced water from onshore oil fields located at the coastal basins of Brazil with higher oil production. The data were made available by the ANP (National Petroleum Agency) from its website, totalizing 67 fields during the years 2014, 2015 and 2016. In addition, dynamic Data Envelopment Analysis was used to determine dynamic efficiency. The results showed a positive effect of the variables directional wells, vertical wells and age, the first two variable showed a fundamental role in determining environmental efficiencies. Therefore, the results allowed to state that there is a poor management of the technological resources in onshore fields of the Brazilian coastal basins, generating excessive amounts of produced water.

Carcharodontosauridae theropod tooth crowns from the Upper Cretaceous (Bauru Basin) of Brazil: A reassessment of isolated elements and its implications to palaeobiogeography of the group

Theropod tooth crowns are abundant in the Upper Cretaceous (post-Coniacian) continental deposits of the Bauru Group, Brazil. The distribution of anatomical crown features indicates that a variety of carnivorous dinosaurs inhabited the area at that time, which is consistent with fossil records from other parts of Gondwana. More specifically, some authors have attributed several isolated specimens to the Carcharodontosauridae; while this has important implications for palaeobiogeography and paleoecology, other scholars have argued that the clade became extinct during the Turonian. In this study, we conducted discriminant and phylogenetic analyses for 18 crowns putatively assigned to the Carcharodontosauridae. In short, the discriminant analysis suggested that the specimens should be tentatively assigned to the following groups: non-abelisauroid Ceratosauria, Abelisauridae, Neovenatoridae, Dromaeosauridae, and Pantyrannosauria. By contrast, the phylogenetic analysis indicated that all should be assigned to abelisaurid theropods, which is consistent with the theropod osteological records in both Brazil and Argentina. We recommend using a combined approach involving morphometric and phylogenetic tools when identifying isolated teeth, as this may yield more reliable identifications. We also suggest that all previous reports on the presence of post-Turonian carcharodontosaurids in the Bauru Group are invalid, which also corroborates previous work. Our results indicate that abelisaurids from the Bauru Basin were diverse in morphology and activity; that is, many were quite large and/or played important ecological roles. Findings also support the hypothesis that this taxon had a preference for semi-arid environments.

Aptian carbon-isotope record from the Sergipe-Alagoas Basin: New insights into oceanic anoxic event 1a and the timing of seawater entry into the South Atlantic

Carbon-isotope ratios derived from organic matter (δ13COM) are presented from Petrobras Well D, onshore Brazil, in the Sergipe-Alagoas Basin. These new data provide a unique view of Aptian palaeoenvironmental history of this low-latitude equatorial region and record the transition from continental to shallowwater marine settings. Comparison of the δ13COM record with that from the Campos–Santos Basins and an agecalibrated Tethyan reference curve allows construction of a detailed chemostratigraphic framework for Petrobras Well D. The evidence suggests that the interval represented by OAE 1a was dominated by deposition of coarse immature clastic sediments and shales deposited in predominantly continental environments with some local marine influence. The refined stratigraphy of Well D suggests synchroneity between a dramatic change in local water chemistry, interpreted as due to the entrance of seawater as consequence of a eustatic sealevel rise, in the Sergipe-Alagoas Basin and deposition of major South Atlantic evaporites present in the Espirito Santo–Campos–Santos Basins (Itaunas, Retiro and Ariri Formations). Furthermore, the more soluble salts in the Ibura Member (deposited elsewhere in the onshore part of the Sergipe-Alagoas Basin) likely postdate the major South Atlantic evaporites present in the Espirito Santo, Campos and Santos Basins. Evaporite deposition in these three southern Brazilian basins would have caused a significant decrease of the global sulphate inventory, which was followed by subsequent deposition of the salts of the Ibura Formation in the onshore part of the Sergipe-Alagoas Basin. Drawdown within these different basins would have led to a eustatic rise in sea level in the world ocean followed by a eustatic fall as refilling took place.

Tree community patterns along pond-upland topographic gradients, upper Uruguay River basin, southern Brazil

We investigated the interrelations between environmental variables (proxies for water availability and soil physico-chemical properties) and tree community patterns (diversity, composition and structure) along pond-upland topographic gradients within depressional watersheds in the upper Uruguay River basin in southern Brazil. Sampling plots were allocated in four topographic habitats: (1) inside ponds (wetland sites) and (2) immediately outside them, and in areas with (3) 60 cm and (4) 120 cm of elevation in relation to their limits (upland sites). Environmental conditions and forest composition varied along pond-upland gradients, but the diversity and structure of tree communities did not. Species turnover was associated with changes in topography-driven environmental conditions, notably water availability. Depressional watersheds show regionally unique abiotic and biotic features but are virtually unprotected by Brazilian private land legislation.

Effects of spatial distance, physical barriers, and habitat on a stream fish metacommunity

Metacommunity structure depends on environmental and spatial factors. Stream fishes are constrained to disperse within dendritic networks and waterfalls and other barriers add resistance to species dispersal. We evaluated the importance of environmental and spatial effects on fish metacommunity composition, adopting different models of spatial distance: overland, watercourse, resistance (physical barriers), cost distance (watercourse resistance), and asymmetrical dispersal (considering flow direction). Fishes were sampled in 31 riffle sites of a small subtropical basin of southern Brazil (~ 250 km2 effective study area). Using redundancy analysis (RDA) and variance partitioning, we found the best model was the one including flow direction weighted by watercourse distance plus environmental variables (overall adj-R2 = 0.42). However, the explanation of fish composition was greatly improved by weighting spatial distance by stream channel sinuosity or height of barriers. Reach slope and width were the two significant environmental variables. Our study supports that dispersal, in addition to environmental factors, affects stream fish metacommunity even in a watershed of small spatial extent. Detecting spatial effects in a small watershed depends on considering realistic watershed features that affect fish dispersal in drainage networks such as waterfalls and other physical barriers, and distance along the watercourse and flow direction.

Phylogenetic position of Diplostomum spp. from New World herons based on complete mitogenomes, rDNA operons, and DNA barcodes, including a new species with partially elucidated life cycle.

Diplostomum ardeae Dubois, 1969 has seldom been reported since its description from the great blue heron (Ardea herodias L., 1758) in the USA. Sequences obtained in this study from the barcode region of cytochrome c oxidase 1 (CO1) in diplostomids from black-crowned night heron (Nycticorax nycticorax (L., 1758)) in Puerto Rico matched data from D. ardeae from A. herodias in the type region. We also obtained DNA barcodes from morphologically similar diplostomids from a rufescent tiger heron (Tigrisoma lineatum (Boddaert, 1783)) and from metacercariae from eye lenses of Trachelyopterus galeatus (Linnaeus, 1766) from the Paraná River basin in Argentina and Brazil, respectively. Barcodes matched (97-100% identity) in these South American adult and larval specimens as well as in recently published sequences from metacercariae from 11 other siluriform fishes from the same region. Barcodes from the South American species, which we describe as Diplostomum lunaschiae n. sp., differed from those of D. ardeae by 7.2-9.8%, and the new species differs from D. ardeae in its size, pharynx:oral sucker length ratio, egg:body length ratio, and distribution of vitellaria. As in prior phylogenetic analysis of CO1 sequences, both D. ardeae and D. lunaschiae n. sp. were not associated with Diplostomum. In more character-rich analyses of nuclear rDNA and of mitochondrial genomes, D. ardeae was an early divergent member of clades of species of Diplostomum. Consequently, we continue to consider D. ardeae and D. lunaschiae n. sp. members of Diplostomum, in contrast to recent suggestions that these species may belong to a different genus.

Hydraulic Continuation of the Abyssal Flow From the Vema Channel in the Southwestern Part of the Brazil Basin

AbstractIn 2013 and 2018, Shirshov Institute of Oceanology performed 12 stations with conductivity‐temperature‐depth and lowered acoustic Doppler current profiler (LADCP) profiling in the southwestern part of the Brazil Basin in order to find continuations of hydraulic controlled flow of the coldest Antarctic bottom water that propagates along the deepest bed of the Vema Channel. Comparison of these measurements with the historical database and our previous measurements in the Vema Extension region (27°S, 34°W) showed that such a continuation of the flow does not exist in the valley directed to the east, which seemed to be a topographic extension of the Vema Channel. Continuation of the flow was found over the section at 25°34′S across the meridionally oriented channel (depth up to 4,950 m) approximately along 33°30′W north of the Vema Extension region. Northward velocity speeds exceeding 35 cm/s were measured in the bottom flow (100–150 m thick above the bottom), which is displaced to the western slope of the meridional channel. Transport in the high‐speed core (velocity speed greater than 10 cm/s, potential temperature less than 0.62°C) in this channel was estimated at 0.150 ± 0.007 Sv on the basis of the LADCP measurements. There are several indirect indications of the formation of a local spillway (or a cascade of spillways) here in the regime of hydraulic control overflow.

Amphi-American Neogene teleostean tropical fishes

During the last 20 years of paleontological expeditions in different sedimentary basins of Brazil, Colombia, Costa Rica, Ecuador, Jamaica, Trinidad, Panama, the Dominican Republic and Venezuela, teleost otoliths have been found along the tropical western central Atlantic (TWCA) and the tropical eastern central Pacific (TECP); these otoliths relate to the amphi-American distribution of fishes and the paleoceanographic and paleoenvironmental changes in the region during the Cenozoic. This study analyzes of the marine fish fossil based on comprehensive species records belonging to the Neogene period and listed at the generic level. Joint classification and ordination techniques were used to identify and analyze data comprising 169 genera belonging to 56 families and 20 orders, which were mostly represented by the demersal species that inhabit shallow waters. Analyses of principal components were used to calculate the covariance and the variance between formations, countries, basins, and age. The results showed that the main faunistic changes along the geochronological sequence in the Neogene basins of tropical America were a consequence of paleoenvironmental changes.

Assessment of water quality using principal component analysis: a case study of the Marrecas stream basin in Brazil

ABSTRACT Monitoring water quality is a fundamental process to ensure proper anthropogenic usage and environmental protection of this resource. This study collected monthly measurements of 9 parameters (pH, Temperature, BOD, Total Solids, Thermotolerant Coliforms, Dissolved Oxygen, Total Nitrogen and Total Phosphorus) in 5 sampling stations along the Marrecas water stream, during a 1-year period. Temporal and seasonal variations were analyzed and interpreted for each element, explaining how specific geographical and anthropogenic factors affected the water body. Principal Component Analysis (PCA) was applied to evaluate each element’s correlation and to reduce the number of parameters, easing the assessment of water quality for each location. Results were followed by the creation of an improved index for the region, which could better estimate the quality of water, only considering 4 of the original parameters. It was also recognized that each water body possesses several subtleties that impact on how its water quality should be measured and indexed into a single value, which validates the case for the creation of regional WQI’s.

Sporolithon franciscanum sp. nov. (Sporolithales, Rhodophyta), a New Rhodolith-Forming Species from Northeast Brazil

This paper describes Sporolithon franciscanum, a new rhodolith-forming species of non-geniculate coralline algae found at depths between 47–52 m near the São Francisco river mouth, the second largest and the most extensive drainage basin in Brazil, and also at the Abrolhos Bank, in the world´s largest rhodolith beds. DNA sequences from plastidial psbA and rbcL markers indicate that the species is unique compared to all other Sporolithon species that have thus far been sequenced. Since morpho-anatomical features of the new species are shared with some other Sporolithon species, its identification was only confirmed by DNA sequences.

A diagnostic framework to assess the governance of the São Francisco River Basin Committee, Brazil

AbstractEnvironmental governance requires integrating social‐institutional governance and river basin management as part of the sustainable river basin development. This remains challenging and few tools exist to facilitate this objective. As part of a diagnostic governance framework on basin management in the São Francisco River Basin in Brazil, this paper investigates the influence of four governance indicators of institutions, leadership, collaboration, and learning. Data on governance and biophysical condition were collected through semi‐structured stakeholder interviews and indicator scoring. Institutions were found to be robust and based on shared values, despite adherence to different paradigms (top‐down vs. bottom‐up) and lack of transparency and clarity of roles. It was found that leadership, and its function of decision making, required enhanced subsidiarity and autonomy for the river basin committee. Collaboration was based on mutual respect, but needed to be improved to achieve fairer water allocation and payments, social justice, and ecological sustainability. It was found that learning requires better knowledge transfer and capacity building at municipal level. The current São Francisco Basin Plan (2016–2025) will build on a robust history of capacity building, but should include governance indicators for performance evaluation of environmental governance.

An approach to reduce exploration risk using spectral decomposition, prestack inversion, and seismic facies classification

Petroleum companies have invested heavily in the exploration of frontier offshore basins in Brazil. Uncertainties associated with geologic complexity, lithostratigraphy, fluid content, and seismic resolution in these basins are the most common challenges. Many methods have been used to circumvent these issues, such as assessing seismic attributes, seismic inversion, spectral decomposition, and the integration of these methodologies to accomplish an optimal approach. Because of the complex geology of these areas, it is very difficult to identify potential reservoirs within one specific geologic formation. Hence, applying spectral decomposition to frontier basins of high geologic complexity can help overcome the challenges because in the frequency domain, it is possible to better define variability and lateral discontinuities. The correct choice of the spectral decomposition optimization approach is critical for accurate target zone representation as well as selection of the appropriate transform. Prestack inversion, spectral decomposition, and attribute seismic facies classification were applied to evaluate the extent of a reservoir and analyze whether an appraisal well has been sited at a good location. The results showed that the new appraisal well was planned at a good location but that its facies were not as good as those of the first discovery well, as confirmed after drilling.

The big picture of field hydrology studies in Brazil

ABSTRACT In-situ hydrological monitoring is essential for a proper decision-making process and modelling. Efforts have been made in Brazil to carry out field activities at the basin scale, but how complete and comprehensive are those studies? Where are they located? How long have they been carried out? What are the main findings? To answer these questions, an overview of experimental monitoring basins in Brazil is presented, listing their geographical locations, monitored variables, operational status, monitoring periods and main publications. We identified 60 monitored sites, spread across most Brazilian biomes, with an average monitoring period of 12 years. However, some publications from these monitoring studies are not fully accessible to the international community. Field hydrology activities in Brazil contribute to a better understanding of hydrological processes in humid and semi-arid regions and inform us about the impacts of land-use change on water quality and quantity.