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Hydropower expansion is increasingly responsible for connectivity and biodiversity loss in freshwater ecosystems. The Amazon basin, which supports the highest level of freshwater biodiversity globally, faces such unplanned expansion. Here, we demonstrate and quantify the impacts of two major hydroelectric dams on the Madeira River on the trans‐Amazonian movements of one apex predatory catfish (Brachyplatystoma rousseauxii) performing the longest migration known in freshwaters. Using otolith microchemistry, we show that above the dams, the former basin‐wide homing migration between the breeding grounds in the upper Madeira and the nursery in the Amazon estuary has now been replaced by residency. We found evidence suggesting downstream migration of juvenile fish past dams into the Amazon estuary and that some of them home back to the Madeira. However, we did not find evidence that the fish homing back from the estuary can access their breeding grounds in the upper Madeira; they remain blocked below the dams. Our results provide undisputable evidence that the conservation of the species primarily requires the reestablishment of connectivity with the construction of efficient fishways. [ABSTRACT FROM AUTHOR]

The state of Rondônia harbors 185 of the 399 species of mammals recorded from the Amazon biome, which corresponds to 46.4% of the total number of species. The state is also an important center of diversity and endemism, especially due to the presence of major biogeographical barriers such as the rio Madeira. We employed trap cameras and track surveys to assess the mammal community in the Base de Selva da Polícia Militar in Rondônia state, Brazil. During one year of survey, we recorded 40 species of medium-sized and large mammals, and, in our study, we recorded the highest mammal richness for a locality in Rondônia, which highlights the importance of private protected areas for mammal conservation in the state. Camera-trap records also showed the occurrence of threatened species. Finally, we provide recommendations for additional studies in this region that is threatened by deforestation and expansion of agriculture.

Monitoring sediment transport in a run-of-river hydropower dam was investigated to detect and quantify the siltation processes using Sentinel-2/MSI satellite images. We developed a method allowing us to assess the fate of sediment discharge in reservoirs and to map the locations of eroding and silting stream cross sections. This monitoring was achieved by retrieving the seasonal and interannual variation in suspended sediment concentration (SPM) longitudinally and by developing indices to detect local deviations from the overall SPM trend. A comparison between Sentinel-2 reflectance, processed for atmospheric and glint correction, and field measurements showed fine accuracy for the b8a/b4 band ratio (RMSE = 0.23 sr-1, N = 50) as well as a very good SPM retrieval performance for a wide range of concentrations [10–926 mg/L] with an RMSLE of 0.23 mg/L. SPM trend analysis demonstrated that significant (p

Abstract A new species of Cyphocharax is described from the rio Juma, which flows across the meridional Amazon basin and is a tributary of the rio Aripuanã in the rio Madeira fluvial system. Features distinguishing the new species from congeners include a longitudinally elongated caudal peduncle blotchextending from the vertical line through the adipose-fin terminus to the base of median caudal-fin rays, the number of scale series along the lateral line and between the lateral line and dorsal-fin origin, morphometric variation, and the patterns of pigmentation along the body. The species was discovered in a lesser-explored region and appears to be an endemic of the rio Aripuanã in the southern Amazon basin.

Copyright of Revista Arqueologia Pública is the property of Universidade Estadual de Campinas - Portal de Periodicos Eletronicos Cientificos and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Neotropical Ichthyology is the property of Neotropical Ichthyology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of GeSec: Revista de Gestao e Secretariado is the property of Sindicato das Secretarias e Secretarios do Estado de Sao Paulo (SINSESP) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Two new miniature species of the trichomycterid genus Tridens are described from the Madeira River drainage, Acre and Rondônia States, Brazil. Until this work, Tridens was a monotypic genus composed solely of Tridens melanops, from the Putumayo/Içá River drainage, upper Amazonas River basin. Tridens vitreus sp.n. is known from upper and middle Madeira River drainage and differs from all other congeners by the lack of pelvic fins and girdle and by vertebra and dorsal‐fin ray counts. Tridens chicomendesi sp.n. is known from Abunã River, middle Madeira River drainage and is distinguished from all other congeners by the number of vertebrae, dorsal‐fin ray count and anal‐fin base colouration pattern. Tr. chicomendesi sp.n. is further distinguished from T. vitreus by a combination of character states regarding the position of urogenital opening, dorsal‐fin position, anal‐fin position, maxillary barbel length, number of premaxillary teeth, number of dorsal‐fin rays, number of anal‐fin rays, number of lateral‐line system pores, frontal bone anatomy, degree of ossification of maxilla, anatomy of quadrate‐hyomandibular joint, size of posterodorsal process of hyomandibula, length of opercular patch of odontodes, number of interopercular odontodes, proportion of upper hypural plate cartilage relative to its area ; by the absence of a proximal, distal and ventral cartilages on ventral hypohyal; by the absence of a lateral process on basibranchial 4; by the presence of a cartilage block on the lateral process of autopalatine, the presence of a well‐developed ossification on proximal margin of ventral hypohyal, the presence of hypobranchial foramen; and by the presence of an anterior cartilaginous joint between quadrate and base of posterodorsal process of hyomandibula. This work represents the first species description for the subfamily Tridentinae in more than 30 years and for the genus Tridens since its original description in 1889. [ABSTRACT FROM AUTHOR]

Livelihood changes associated with forced displacement caused by large dams occur in a context of socio-environmental transformation, raising the question on how resettled people cope with and adapt while experiencing environmental change. This article analyses how environmental change is connected to householdś livelihood in communities displaced by the Madeira River hydroelectric dams, Santo Antônio and the Jirau, in the Brazilian Amazon. We adopted a mixed methods approach, exploring qualitative and quantitative aspects of the relationship between environmental changes and households' livelihood. The results indicate the decline of ecosystem-related activities, such as fisheries and floodplain agriculture, through the process of resettlement, period in which took place the major negative environmental impacts of the dams. These overlapped processes contributed to the livelihood displacement experienced by resettled communities, a trend intensified by the resettlement plans addressed by Impact Assessment process that incentivized the adoption of socioeconomic practices that weren't part of peoples' livelihoods, such as market-oriented agriculture and pisciculture projects. Such trends call for the urgency of preventing displacement over treating it by mitigation and compensation measures that fail to account immaterial losses, a crucial subject for future research. The results may help improve the revision of the resettlement plans for the studied dams, others in the region and plans for projects yet to come. [ABSTRACT FROM AUTHOR]

The enchantments of the rivers populate the imagination of the Amazonian riverside populations, so that there is an intricate mythical relationship that gives new meaning to water. It is in this context that the boto’s myth is strongly linked to the corporeality and sexuality of riverside women. It is interesting to note that in addition to the traditionally sense given to this myth, another meaning was identified, being distanced from the libidinous charm and, therefore, from the sexual connotation, approaching issues related to religion and spirituality. Therefore, this article aims to analyze the meaning linked to religious and spiritual issues given to the myth of the boto, in order to understand the implications in the lives of women who live in the riverside community of Nazaré - RO. The research was carried out in the riverside community of Nazaré, located on the left bank of the Madeira River, approximately 120 km from the city of Porto Velho. This study has a qualitative character and the methodological procedures used were bibliographic research, field research, characterized by semi-structured interviews with four women and informal conversations with ten others. [ABSTRACT FROM AUTHOR]

In the Amazon basin, several species are restricted to or occur primarily in habitats along rivers. However, little is known about habitat occupancy over time and how seasonal fluctuations in the level of rivers affect bird species occurrence in floodplains. In this study, we verified if the occupancy and detection probability of 10 floodplain bird specialist species are related to 3 environmental variables considered to be important for floodplain birds: the number of Tessaria shrubs, the number of Cecropia trees, and the number of other tree species. We also tested if occupancy and detection probabilities changed among flood pulse seasons. Our study was conducted at 19 sampling sites in the Madeira River floodplain in Rondônia, Brazil, including sites impacted by the Santo Antonio dam. Sampling was done with autonomous recorders and subsequent development of semi-automatic identification models for each species. The best occupancy models show that the number of Tessaria shrubs was positively related to occupancy probability for 4 species: Black-and-white Antbird (Myrmochanes hemileucus), Parker's Spinetail (Cranioleuca vulpecula), White-bellied Spinetail (Mazaria propinqua), and Plain-crowned Spinetail (Synallaxis gujanensis). The number of Cecropia trees was positively correlated with the occupancy of a single species, the Spotted Tody-Flycatcher (Todirostrum maculatum). The number of other trees was positively correlated for White-browed Antbird (Myrboborus leucophrys), Peruvian Warbling-Antbird (Hypocnemis peruviana), and Band-tailed Manakin (Pipra fasciicauda). Occupancy probability is similar among sampling periods, which indicates that species remain onsite. The detection probability, however, varied in 9 of the 10 species, probably related to seasonal variation in vocal activity. This variation in detectability needs to be considered in bird surveys in floodplains. In addition, the classification of floodplain species according to the type of habitat specialization can help define the species most vulnerable to environmental changes, such as those caused by hydroelectric plants in the Amazon. Na Bacia Amazônia, diversas espécies são restritas ou ocorrem primariamente em habitats ao longo dos rios. Entretanto, pouco se conhece sobre a ocupação do habitat ao longo do tempo e como as flutuações sazonais no nível dos rios afeta as espécies de aves que ocorrem nas várzeas. Nesse estudo, nós verificamos se a ocupação e a probabilidade de detecção de 10 espécies de aves especialistas em várzea são relacionadas com 3 variáveis ambientais consideradas importantes para aves de várzea: o número de arbustos do gênero Tessaria, o número de árvores do gênero Cecropia e o número de outras espécies de árvores. Nós também testamos se a ocupação e detectabilidade das espécies muda entre os períodos do pulso de inundação. Nosso estudo foi realizado em 19 sítios amostrais nas várzeas do rio Madeira no estado de Rondônia, Brasil, incluindo sítios impactados pela barragem de Santo Antonio. A amostragem foi feita com gravadores autônomos e posteriormente desenvolvido um modelo de identificação semi-automática para cada espécie. O melhor modelo de ocupação mostrou que o número de arbustos de Tessaria é positivamente relacionado a ocupação de 4 espécies: Myrmochanes hemileucus, Cranioleuca vulpecula, Mazaria propinqua e Synallaxis gujanensis. O número de árvores do gênero Cecropia foi positivamente relacionado a ocupação de uma única espécie, em Todirostrum maculatum. O número de outras árvores foi positivamente relacionado a ocupação de Myrmoborus leucophrys, Hypocnemis peruviana e Pipra fasciicauda. A probabilidade de ocupação é similar entre os períodos de amostragem, o que indica que as espécies permanecem nos locais. A probabilidade de detecção, porém, teve uma variação significante para 9 das 10 espécies, provavelmente relacionada a variação sazonal na atividade vocal. Essa variação na detectabilidade deve ser considerada nas amostragens de aves nas várzeas. Adicionalmente, a classificação das espécies de aves de várzea de acordo com o tipo de especialização em habitat pode ajudar a definir quais são as espécies mais vulneráveis a impactos ambientais, como os causados por usinas hidroelétricas. [ABSTRACT FROM AUTHOR]

Copyright of Revista Foco (Interdisciplinary Studies Journal) is the property of Revista Foco and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The recent large-scale hydropower development in the Amazon basin has raised concerns about the impacts on the movements of migratory fishes such as goliath catfish (Brachyplatystoma spp.). In the Madeira River, the efficiency of a 1400-m long fishway in the Santo Antônio hydropower plant (SAE HPP) was evaluated between 2012 and 2016 using telemetry techniques. Tagged fish (N = 388) were released 2000 m downstream of the dam and near the entrance or inside the fishway (N = 149). Fixed radio stations monitored fish movements and residence near 14 different structures of the SAE HPP; four acoustic receivers in the reservoir and one downstream the dam monitored whether fish moved away or past the dam. The findings revealed that 15% of the fish released downstream were detected near the dam but none were detected in the reservoir upstream. For the group of fish released in the fishway, no B. rousseauxii (N = 64) was detected moving upstream and into the reservoir and 5 individuals of B. vaillantii (N = 41) exited the fishway to the reservoir. This was the first long-term telemetry monitoring of fish movements near a dam in the Amazon and the results provided evidence of inefficiency of the fishway for the target species, which led the hydropower company to reconstruct the fishway. [ABSTRACT FROM AUTHOR]

The Madeira River Navigation and Improvement Project provides a unique opportunity to incorporate nature‐based solutions (NbS) into the built environment to promote sustainable communities and water resources infrastructure. The Madeira River has no major physical interventions (river training structures, navigation locks and dams, etc.) to improve navigation, and so is one of the world's last remaining undeveloped megarivers that exhibits natural morphological processes. The objective of this study is to create a safe, reliable, and sustainable navigation channel in the Madeira River. This is being accomplished by designing navigation improvement measures that leverage natural geomorphic processes of the river while minimizing conventional engineering practices that alter the river's morphology. To meet this objective, fluvial geomorphology analysis and hydrodynamic modeling studies have been performed to improve understanding of the morphological behavior of the system. Measures that incorporate beneficial reuse of dredged sediment within the system are being prioritized and incorporated into the study's design. Natural processes are being leveraged through the implementation of an adaptive management process to shape the navigation channel by incorporating the use of dynamic structures using natural local materials (e.g., large woody debris already in the system), a direct application of NbS in practice. This process includes extensive stakeholder collaboration and utilizing nature's energy to balance navigation, ecological, and social benefits along the Madeira River. This project demonstrates that nature‐based approaches not only provide navigation benefits but can also provide ecological and social benefits in ways that are sustainable in the long term, consistent with United Nations Sustainable Development Goals (SDGs) and the International Union for the Conservation of Nature's global standard for NbS. Integr Environ Assess Manag 2022;18:115–122. © 2021 SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA. KEY POINTS: The Madeira River is an undeveloped megariver where navigation is substantially inefficient during low water conditions due to sand shoals and rock outcrops, necessitating commercial navigators to implement various measures that increase travel time and costs.The Brazilian government initiated statistical hydrology, hydraulic model, fluvial geomorphology, and sediment transport model studies combined with an extensive stakeholder collaboration process to identify ways in which the river's natural geomorphology could be used to balance multiple benefits.Nature‐based solutions identified for implementation included use of large wood, innovative river training and stabilization structures, sediment beneficial use, and reuse of rocks currently obstructing the channel.These study results are being used to identify candidate locations for constructing features in future phases of the Madeira River project that in the long term will substantially limit dredging needs, while enhancing economic benefits and sustaining the river's ecology. [ABSTRACT FROM AUTHOR]

Copyright of Acta Zoologica Lilloana is the property of Fundacion Miguel Lillo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Bats are the second most diverse taxa of mammals in the world, after rodents. Some studies have evaluated if there is a relationship between the environment and the morphology of bats, because environmental conditions can have an important influence on the phenotype of the species. The aim of the present study is to evaluate the relationship between a morphological variable (body mass index - BMI) of populations of the species Artibeus planirostris and the environment, considering the climatic variation in two hydrographic basins of the center of the Brazilian Amazon. The hypothesis is that the BMI responds to the environmental variables of each site. This will be higher during the rainy season and in the high water period, responding to a high availability of resources, according to studies carried out in the same region. 400 bats were captured, of which 180 were males and 220 were females. Although the index seemed to show differences considering the sex of the individuals, both in the Madeiras river basin (ANOVA: gl = 1, F = 6.90, P = .00) and in the Purus river (ANOVA: gl = 1, F = 3.95, P = .01), there was no significant difference between the BMI and the different environments, considering the climate season. It is concluded that, in this study, no evidence was found to support the hypothesis about the influence of the environment on BMI in populations of the bat species Artibeus planirostris in the center of the Brazilian Amazon.

The Madeira River rises in the Andes, draining the southwestern Amazon basin and contributing up to 50% of the Amazon River sediment load. The Porto Velho station monitors the Upper Madeira basin and is located just downstream of the Jirau and Santo Antonio hydropower dams. At this station, decreasing trend (p < 0.10) of the surface suspended sediment concentration (SSSC) has been documented during the sediment peak season (December to February) for the 2003–2017 period. This study aims to evaluate the role of the rainfall variability on this documented decreasing trend. For this purpose, we applied correlation and trend analysis in water discharge, SSSC and rainfall time series over the main tributaries of the Upper Madeira basin. The decline of SSSC in December is attributed to the reduction of rainfall in the Madre de Dios sub-basin from the start of the rainy season in October. However, the SSSC negative trend (p < 0.10) in January and February is associated with a shift in the magnitude of rainfall during these months in the Andean region after 2008, and the dilution associated with base flow. These results reveal that the decline of SSSC in the Madeira River should not be evaluated just on the basis of the data downstream from the dams, but also of the processes upstream in the Andean part of the basin. In a context of drastic anthropogenic climate and environmental changes, understanding the combined influence of regional hydroclimate variability and human actions on erosion and sediment transport remains a critical issue for the conservation of the Amazon-Andes system.

Information about future streamflow is important for hydropower production planning, especially for damless hydro-power plants. The river flow is a reflection of various hydrological, hydrogeological, and meteorological factors, which increases the direct modeling difficulty, and favors the use of data-driven methods. In this paper, we propose the use of one-dimensional convolutional neural networks (1d-CNN) for multi-day ahead river flow forecasting and we present a multi-input model using correlated-input time-series. The proposed model was applied at the Madeira River, the Amazon's largest and most important tributary, near the Santo Antônio damless hydro-power plant. We compared the proposed correlated-input 1d-CNN to a single-input 1d-CNN model and some baseline models. Furthermore, we conclude that 1d-CNN performed better than all baseline models and that the correlated-input forecasting model is 5 times smaller than the single-input equivalent with accuracy improvements.

Host-parasite interactions between ticks and wild species are important for examining the ecology and distribution of ticks, as well as the consequences of these interactions for hosts and diseases. Ticks have medical importance because they are vectors of microorganisms and pathogens, such as viruses, bacteria, and protozoa, that can be transmitted to humans and other animals, causing serious disease. Like other anuran species, Rhinella marina also harbors a wide variety of parasites. This occurs mainly because of its large body size and because it occupies terrestrial environments, but also because it has direct contact with aquatic environments (larval and reproductive stages), thus presenting several opportunities for parasitic infections. This work has as main objective to describe the occurrences of host-parasite interactions between the species Rhinella marina (Linnaeus, 1758) and Amblyomma rotundatum (Koch, 1844) geographically expanding their occurrence in the Amazon rainforest through the Madeira River. During a herpetofauna survey, the first individual of R. marina was observed at 08:37 PM on September 20, 2020. The location is near a transect within a primary forest. This individual was parasitized by a single tick identified as Amblyomma rotundatum. On a second expedition, a second individual of R. marina was observed at 11:38 PM on January 5, 2021. The location is rural road C-01 in the municipality of Porto Velho-RO, which passes within a primary forest and deforested private properties. This individual was parasitized by nine ticks identified as Amblyomma rotundatum. An important observation to be made is that the occurrences of A. rotundatum parasitizing R. marina are 57 km apart and cross an important geographical barrier, the Madeira River of the Amazon basin. This work geographically expands the occurrence of A. rotundatum parasitism on R. marina and describes the natural histories of this host-parasite interaction of these species. [ABSTRACT FROM AUTHOR]

In the last decade, we have experienced a huge loss of biodiversity on the planet. One of the possible ways to overcome this loss is to focus on places of human interest, monitoring the changes and the impacts on biodiversity. In general, impact assessments of hydroelectric power-plants on terrestrial invertebrates have been conducted after installation of the dam. Monitoring biodiversity is expensive, and shortcuts are often used to access this information. Therefore the use of the higher-taxon approach seems appropriate for this purpose. We investigated the effectiveness of ant genus-level at predicting ant species-level responses overtime in two grains of the spatial scale (site and plot) in the area of influence of a hydroelectric power-plant in the Amazon basin. We used a database from six sites, sampled over seven years in 14 ant collection events. The samplings were standardized, with five collection points along with 250 m plots. We tested whether the variation in the spatio-temporal scales affected the predictive power of genus-level for the metrics of richness and composition. We investigated if there is a difference in the predictive response of genera as surrogates for the species when using different spatial scales (site and plot) and also if the effectiveness of the prediction of genera changes over time. Also, we evaluated the effects of the species: genus ratio on the prediction of genera as a surrogate for species richness and composition.We recorded a high positive correlation between the richness of genera and species. Also, detected high congruence among the composition of genera and species, and no species:genus ratio effect in the evaluated spatio-temporal scales. Thus, the robustness of genus data to predict the species-level does not change over time at both spatial scales under the influence area of ​​a hydroelectric power-plant in the Amazon basin. It reinforces the use of the higher-taxon approach, which can be a useful and efficient tool in biodiversity studies or long-term monitoring.

Large storage dams have widely documented impacts on downstream aquatic environments, but hydroelectric dams with little or no capacity for storage of water inflows (i.e., run-of-river) have received less attention. Two of the world’s largest run-of-river hydropower dams (Jirau and Santo Antônio, Brazil) are located on the Madeira River, the largest tributary to the Amazon River. Here we examine whether the Madeira dams have affected downstream seasonal flood pulses and short-term (daily and sub-daily) flow dynamics. We show that the combined effects of these dams on seasonal flood pulses were modest. However, dam operations significantly increased day-to-day and sub-daily flow variability. The increase in short-term flow variability is largely explained by rapid, short-term variations in river flow caused by fluctuations in energy demand (hydropeaking). Both the magnitude of hydropeaking and the mean absolute day-to-day change in discharge downstream of the dams doubled after dam closure. In addition, the median hourly rate of water level change downstream of the dams was three times higher than upstream. Our findings highlight that even run-of-river dams on very large rivers such as the Madeira—whose average discharge at the dam site is larger than that of the Mississippi River at its mouth—can alter downstream hydrology through hydropeaking. Although little studied in tropical floodplain rivers, hydropeaking by large run-of-river dams may be detrimental to downstream aquatic organisms and human populations that utilize the river for navigation and fisheries.

The present study aimed to validate depth data obtained through the key curve equation elaborated based on data from the Large Basin Hydrological Model (MGB) and Spatial Altimetry (Sentinel 3A). Using as a comparison for validation, depth data obtained through bathymetry. The values found in relation to the parameters of the key curve are coefficient A (250.074); coefficient B (1.738) and the Coefficient Z0 (13.788). The simulated flows produced consistent and applicable results for the study, thus making model calibration unnecessary. The percentage of confidence presented by the key curve was (95%). Values can be explained by section geometry. It was possible to identify the existence of uniformity in the data set, which indicates a good fit of the key curve. The difference between the data obtained by the key curve (MGB/Spatial Altimetry) and (in situ) related to the average depth was (1.17m). When compared, the values found related to the standard deviation, it was possible to identify a difference of (0.76 cm). The validation of geomorphological information related to variable depth can help create new alternatives for the hydrological monitoring of the Amazon basin. [ABSTRACT FROM AUTHOR]

Freshwater invertebrates occupy important roles in ecological processes and are frequently used as indicators of water quality. Their existence, however, is still obscure in many regions of the country, i.e. very few relevant studies have been conducted regarding their presence especially in the Amazon region. Thus, this study aimed to present an inventory of aquatic macroinvertebrates from the marginal region of an Amazonian lake. This study was conducted in a floodplain area, at the Extractivist Reserve of Cuniã Lake (margin of the Madeira River).To sample macrofauna, were collected sediment and aquatic macrophytes near the marginal region in seven sites during low-water season (August 2015) and the high-water season (February 2016). The environmental variables (water temperature (ºC), electric conductivity (μS /cm), pH, and dissolved oxygen (mg/L) were measured at each site and concentrations of organic matter in the sediment were also determined. A total of 28 taxa were recorded. The most significant taxa for the lake were the genera: Campsurus (Ephemeroptera: Polymitarcydae) and Tenagobia (Hemiptera: Corixidae. The lake presents diverse macrofauna, indicating good environmental quality and organic enrichment, which highlights the importance of flood in composition of local macrofauna.

The Madeira River is the most extensive tributary of the Amazon River and has the largest diversity of fishes in the world. On its right bank, the Madeira River receives the Jamari River, in which the first hydroelectric power plant (HPP) in State of Rondônia, Samuel HPP, was built. Besides this, other dams were built in the Jamari River and its tributaries, however, the available information in the scientific literature about the ichthyofaunistic diversity of this basin is rare. This work aims to provide an ichthyofaunistic inventory in a region of the Jamari river basin, in the State of Rondônia, where three small hydropower plants (SHPs) were implemented. The ichthyofauna was sampled in 16 expeditions between August 2015 and December 2018. Gill nets and seine nets were used with different meshes, as well as longlines and cast nets at different times of the day. Additionally, 81 INPA lots of species from the Samuel HPP area of influence were reanalyzed. Fish were identified according to the specialized literature, as well as in consultations with experts of various taxonomic groups. Voucher specimens of the species were cataloged and deposited in the ichthyological collection of the Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura (Nupélia) of the Universidade Estadual de Maringá. A total of 230 species were recorded, of which 22 were putative new species, 117 were added to the Jamari River basin and 28 to the Madeira River basin. The continuation of the studies in this section of the Jamari river basin is fundamental for analysis of local impact due to the presence of dams. Moreover, the addition of putative new species to the Madeira River basin indicates gaps in the knowledge of Neotropical ichthyofauna. [ABSTRACT FROM AUTHOR]

Freshwater invertebrates occupy important roles in ecological processes and are frequently used as indicators of water quality. Their existence, however, is still obscure in many regions of the country, i.e. very few relevant studies have been conducted regarding their presence especially in the Amazon region. Thus, this study aimed to present an inventory of aquatic macroinvertebrates from the marginal region of an Amazonian lake. This study was conducted in a floodplain area, at the Extractivist Reserve of Cuniã Lake (margin of the Madeira River). To sample macrofauna were collected sediment and aquatic macrophytes near the marginal region in seven sites during the lowwater season (August 2015) and the highwater season (February 2016). The environmental variables (water temperature, electric conductivity, pH, and dissolved oxygen were measured at each site and concentrations of organic matter in the sediment were also determined. A total of 28 taxa were recorded. The most significant taxa for the lake were the genera: Campsurus (Ephemeroptera: Polymitarcydae) and Tenagobia (Hemiptera: Corixidae). The lake presents diverse macrofauna, indicating good environmental quality and organic enrichment, which highlights the importance of flood in the composition of local macrofauna. [ABSTRACT FROM AUTHOR]

Flow modification of lotic ecosystems is one of the main threats to global freshwater biodiversity. Commonly, and in the river studied here, modification results from hydroelectric dam installation.We evaluated the impacts of damming on zooplankton communities in the Amazonian floodplain of the Madeira River (Porto Velho, Rondônia, Brazil) following construction in 2012 of the run‐of‐river dam of Jirau Hydroelectric Power Plant. Using data sampled between 2009 and 2015, we tested for discontinuities in zooplankton community composition attributable to damming and the naturally occurring flood pulse.The flood pulse remained the main predictor explaining variation in zooplankton community structure even with the installation of the dam on the Madeira River. Despite this, discontinuities for the entire zooplankton community and for the main compositional groups (testate amoebae, rotifers, cladocerans, and copepods) were detected in relation to the dam (pre‐/post‐dam periods), mainly in ebb and low water, and with weaker evidence of dam effects during flood and highwater hydrological periods.A multivariate regression tree explained 9.6% of the variation in zooplankton communities and identified four groups: (1) flood and high‐water periods; (2) low water post‐dam; (3) low water pre‐dam; and (4) ebb hydrological periods. The deviance in each multivariate regression tree node was attributable to variation in eight rotifer, three testate amoeba, and three copepod taxa.Our study demonstrates that the flood pulse, dam construction, and interaction between both of these factors affect zooplankton community structure in the Madeira River. While for many zooplankton community variables, effects occurred mainly during ebb and low‐water periods, some effects were also observed during high water and flood periods. We thus recommend the establishment of a permanent environmental monitoring programme during all hydrological periods in tropical floodplain rivers and the addition of sampling sites downstream from dams.Many rivers in the world are increasingly disrupted by multiple dams, yet little is known of their effects, especially for run‐of‐river dams. Our study identified short‐term impacts of only one run‐of‐river dam on zooplankton communities. More research is needed on the effects of multiple run‐of‐river dams on zooplankton and other biota, especially in tropical floodplain rivers, so that negative effects can be understood and ameliorated. [ABSTRACT FROM AUTHOR]

We isolated and characterized 10 new microsatellites loci for Paleosuchus trigonatus using ION TORRENT Sequencing Technology. We tested the transferability of these loci to three related species of the subfamily Caimaninae, and used these bi-parental markers to test population structure and genetic diversity of two populations of P. trigonatus impacted by hydroelectric dam construction on the Madeira (N = 16) and Xingu (N = 16) rivers. We also investigated the transferability of these markers to three related species: Paleosuchus palpebrosus (N = 5), Caiman crocodilus (N = 6) and Melanosuchus niger (N = 6). The genetic diversity of P. trigonatus was low in both the Madeira (He: 0.535 ± 0.148) and Xingu (He: 0.381 ± 0.222) populations, but the loci were sufficiently polymorphic to be used in system of mating and kinship studies in P. trigonatus. DAPC analysis with our set of microsatellites loci was able to separate the four species of Caimaninae studied and to detect a shallow genetic structure between Madeira and Xingu populations of P. trigonatus. AMOVA and STRUCTURE analyses using locprior model corroborate this shallow genetic structure. These novel molecular markers will be also useful in conservation genetics and phylogeographic studies of P. trigonatus, since they improve our ability to monitor the putative effects of dams on the loss of genetic diversity and allow us to investigate population dynamics and microevolutionary processes that occurred in the species. [ABSTRACT FROM AUTHOR]

Abstract The Madeira River thalweg includes two pool-to-pool spacing periods. First, standard pool-crossing sequences form 6 to 8 m deep pools. These pool-crossing sequences recur approximately every six channel widths (9.7 km or 6.8 W), on average. However, the Madeira study reach (between Manicoré and Porto Velho in Northern Brazil) is relatively straight, making these pools more frequent than meanders. Second, much deeper pools (13 to 30 m deep) also form at relatively regular, but much longer spacing (50–60 km, about 40 channel widths apart). The deeper "mega-pools" occur where the river reaches the edge of the Holocene alluvium, encountering resistant units (e.g., granite, mud clasts, and conglomerates) in the confining Pleistocene units. These two pool scales also occur on the Lower Mississippi River (downstream of Tarbert Landing). This study identified pool formation processes responsible for these two pool-depth and –spacing scales on two large sand-bed rivers. The analyses computed pool statistics and correlated the deepest pools with planform controls. Two distinct pool formation hypotheses explain the two pool types. The standard pools are "rhythmic" features, developed by macro-turbulent feedbacks, while the mega-pools are "forced" features imposed by the regional geology. The former are fundamentally periodic; the latter are not. However, periodogram analysis indicates that mega-pools on the Madeira form a second, relatively regular pool period. The regional geology, including the confining Pleistocene bluffs and, potentially, orthogonal neotectonic lineaments, imposed periodic regularity to these mega-pools on the Madeira River that is not observed on the Mississippi River, a comparably-sized sand-bed river with mega-pools. Highlights • Pool spacing on two large sand-bed rivers conform to the 5-7 channel widths rule. • The Madeira River has two relatively regular pool spacing periods. • The Madeira has regular "rhythmic" pools that conform to the 5-7W rule. • Deeper (13-30 m) "mega-pools" recur at relatively regular spacing where the river encounters resistant Pleistocene bluffs. • The Mississippi River also has smaller rhythmic pools between deep mega-pools. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the quality of fish meat in relation to inorganic contaminants (Zn, Pb, Cu, Cr, Ni and Hg), following the Brazilian Health Surveillance Agency (ANVISA) standards in five Amazonian fish exposed to untreated urban sewage. Trace metal concentrations were evaluated in the muscle tissues of Schizodon fasciatus (herbivorous), Potamorhina latior (detritivorous), Triportheus angulatus (omnivorous), Plagioscion squamosissimus (carnivorous) and Rhaphiodon vulpinus (piscivorous), sampled upstream and downstream of Santo Antônio’s Hydroelectric Dam, Madeira River (Porto Velho City, Brazil). An acid chemical digestion was used to extract trace metals from the tissues, and atomic absorption spectrometry methods were used to quantify the trace metal concentrations. Fish samples showed values above allowed limits for Cr (0.10 mg.kg-1 ), except in Plagioscion squamosissimus (0.09 mg.kg-1 ). Potamorhina latior specimens sampled downstream showed higher values for Cr (p

The study was conducted in Puruzinho lake (Humaitá, AM) considering seasonal periods of rainy and dry in way to elucidate the flood pulse importance in the deposition, remobilization and distributions of mercury and organic matter in bottom sediments in the Madeira River Basin (Brazilian Amazon). Bottom sediments and soils samples were analyzed for total mercury and organic matter. Mercury concentrations obtained in bottom sediment were 32.20-146.40 ng g-1 and organic matter values were 3.5 - 18.0%. The main region for accumulation of mercury and organic matter was in the central and deepest lake area In the rainy season there was a greater distribution of Hg and organic matter, mainly controlled by means of income of the Madeira river water during flooding, while the predominant process in the dry season was the remobilization of total Hg due to the resuspension of bottom sediments.

Impact of flooding on tropical forest ecosystems and their management is a little-studied area that is expected to become increasingly important under projected climate change. A demonstration of this was provided by the record-breaking 2014 flood of the Madeira River in Brazil. We assessed factors affecting survival of Brazilnut trees ( Bertholletia excelsa H.B.K.) under root asphyxia caused by flooding in the Lago do Capanã Grande Extractive Reserve in Manicoré municipality (county), Amazonas state, Brazil. Mortality was surveyed in three Brazilnut groves ( castanhais ) in 680 individual Brazilnut trees of which 357 had been exposed to flooding and 200 had been flooded for at least 83 days, which was the threshold for mortality effects. Trees were georeferenced and measured for DBH and the height above the ground of the flood-water mark. This information, together with topography from satellite data and water levels from hydrographic gauges, allowed calculation of the time each tree was flooded. None of the 323 unflooded trees died. The analysis indicates a relationship between mortality and duration of root asphyxia, killing 17% of the individuals exposed to flooding and 35% of the individuals that were flooded for periods greater than 109 days. Nevertheless, survival exceeded 50% for all flooding durations. The data suggest that larger trees have a greater probability of mortality for any given period of asphyxia. Expected increases in extreme flood events threaten a sustainable forest management system based on harvest of non-timber products. [ABSTRACT FROM AUTHOR]

The Madeira River is the second largest tributary of the Amazon River. It contributes approximately 13% of the Amazon River flow and it may contribute up to 50% of its sediment discharge to the Atlantic Ocean. Until now, the suspended sediment load of the Madeira River was not well known and was estimated in a broad range from 240 to 715 Mt yr −1 . Since 2002, the HYBAM international network developed a new monitoring programme specially designed to provide more reliable data than in previous intents. It is based on the continuous monitoring of a set of 11 gauging stations in the Madeira River watershed from the Andes piedmont to the confluence with the Amazon River, and discrete sampling of the suspended sediment concentration every 7 or 10 days. This paper presents the results of the suspended sediment data obtained in the Madeira drainage basin during 2002–2011. The Madeira River suspended sediment load is estimated at 430 Mt yr −1 near its confluence with the Amazon River. The average production of the Madeira River Andean catchment is estimated at 640 Mt yr −1 (±30%), the corresponding sediment yield for the Andes is estimated at 3000 t km −2 yr −1 (±30%), and the average denudation rate is estimated at 1.20 mm yr −1 (±30%). Contrary to previous results that had mentioned high sedimentation rates in the Beni River floodplain, we detected no measurable sedimentation process in this part of the basin. On the Mamoré River basin, we observed heavy sediment deposition of approximately 210 Mt yr −1 that seem to confirm previous studies. But while these studies mentioned heavy sedimentation in the floodplain, we showed that sediment deposition occurred mainly in the Andean piedmont and immediate foreland in rivers (Parapeti, Grande, Pirai, Yapacani, Chimoré, Chaparé, Secure, Maniqui) with discharges that are not sufficiently large to transport their sediment load downstream in the lowlands. [ABSTRACT FROM AUTHOR]

Rising in the Andes, the Madeira River drains the southwestern part of the Amazon basin, which is characterized by high geographical, biological and climatic diversity. This study uses daily records to assess the spatio-temporal runoff variability in the Madeira sub-basins. Results show that inter-annual variability of both discharge and rainfall differs between Andean and lowland tributaries. High-flow discharge variability in the Andean tributaries and the Guaporé River is mostly related to sea surface temperature (SST) in the equatorial Pacific in austral summer, while tropical North Atlantic (TNA) SST modulates rainfall and discharge variability in the lowlands. There also is a downward trend in the low-flow discharge of the lowland tributaries which is not observed in the Andes. Because low-flow discharge values at most lowland stations are negatively related to the SST in the tropical North Atlantic, these trends could be explained by the warming of this ocean since the 1970s.EDITOR A. CastellarinASSOCIATE EDITOR A. Viglione [ABSTRACT FROM PUBLISHER]

[Display omitted] • Flooding caused by the filling of Jirau dam resulted in high tree mortality. • Species richness estimates were also heavily affected by flooding. • The filling of Jirau dam dramatically increased annual herbaceous mortality rates. • High mortality rates were related to the longer flooded period. • Flooding was particularly associated with high Zingiberales mortality rates. Mega-dams have drastically altered the pulse of natural flooding in rivers of the Amazon, negatively affecting the biodiversity of different forest ecosystems. This study aimed to investigate the impacts of the Jirau dam on herbaceous assemblages, a relatively little studied biodiversity component. To accomplish this, we surveyed understorey herbs in 22 permanent plots (375 m2 each) between 2012 and 2019, before and after filling of the Jirau dam, and also measured a set of environmental predictors. Sampling comprised 178 morphospecies and 43,335 individuals. We found that species compositions in the pre-dam period differed in each of the sampled habitats (terra firme , transitional forest, várzea , and campinarana), and that such differences were mostly correlated with sum of bases, topography, C/N ratio, silt and pH. Environmental associations differed among three major groups of herbs (Ferns, Poales and Zingiberales). During the post-dam period, flooded plots showed high rates of mortality and recruitment close to 100 % and a sharp decline in species richness while non-flooded plots showed relative stability for these parameters. The number of flooded days and habitat type were strong predictors of mortality and recruitment rates. A combination of canopy opening driven by tree mortality and seasonal flooding after filling of the Jirau reservoir altered herb species composition in flooded plots, favouring the recruitment of Poales. Overall, herbaceous plants showed higher sensitivity to flooding caused by the Jirau dam when compared to trees sampled in the same site, reinforcing their potential as biodiversity targets for environmental assessments. [ABSTRACT FROM AUTHOR]

O trabalho teve como objetivo analisar o desembarque da pesca comercial na região do Médio rio Madeira, tendo como área focal o município de Manicoré, buscando identificar as espécies explotadas, os locais de pesca e sua contribuição para o abastecimento local de pescado. O desembarque foi amostrado diariamente, utilizando questionários aplicados aos pescadores após a comercialização do pescado. Foram desembarcadas no ano de 2002 aproximadamente 225,4 toneladas de pescado. Canoas motorizadas efetuaram mais expedições de pesca, entretanto os barcos de pesca desembarcaram uma maior produção. Os valores médios de desembarque foram de 11,2; 5,4 e 2,4 toneladas por mês para barcos, canoas e compradores de pescado respectivamente, sendo as capturas compostas por 32 espécies ou grupo de espécies, sendo jaraqui (Semaprochilodus spp), pacu (Mylossoma duriventre), curimatá (Prochilodus nigricans), sardinha (Triportheus spp) e jatuarana (Brycon spp), responsáveis por 75% do pescado desembarcado. Foram identificados 32 locais de pesca, sendo os mais explotados os rios Madeira e Manicoré, os lagos Acará e Boquerão e o igarapé Matupiri.The study aimed to analyze the landing of commercial fishing in Middle Madeira River, near Manicoré city, identifying the exploited species, fishing grounds and the contribution for the local supplying of fish. Fish landings were sampled daily, using questionnaires, given to fishermen after the fish sale. In 2002, 225.4 tons of fish were landed in Manicoré city. Motorized canoes undertook more fishing trips, but the higher fish landings were accomplished by boats. Mean values of fish landings were 11.2 tons/month, 5.4 tons/month and 2.4 tons/month for boats, motorized canoes and fish purchasers, respectively. 32 species or group of species were landed, with a predominance of jaraqui (Semaprochilodus spp), pacu (Mylossoma duriventre), curimatá (Prochilodus nigricans), sardinha (Triportheus spp) e jatuarana (Brycon spp), responsible for 75% of fish production. 32 fishing grounds were identified and the most exploited were the Madeira and Manicoré rivers, Acará and Boquerão lakes and the Matupiri stream.

The profile of sardine fishing, the Triportheus species, landed at the fishing market of Porto Velho (RO) between 1990 and 2004, was established by analyzing variations in the intra- and inter-annual yield as well as the length and general characteristics of the fishing. The annual production varied from 15,372 to 78,340kg (average = 33,482kg), totaling 5.46% of the overall production during the studied period. These variations can be related to the changes in the fishermen’s effort, as a reflex to searching for alternatives for fishing, or related to the level of the river, since the greatest annual yields were preceded by years of having more intense flooding. The monthly production varied from 0 to 21,456kg (average=2,876kg). Greater values of production were obtained in periods of lower hydrological levels (dry season) [r(Pearson)= -0.53. p

This study evaluated various aspects of the profile of pacu (Mylossoma spp., Myleus spp., Metynnis spp.) fish marketed on the Cai N’água floating platform of Porto Velho (RO) from 1985 to 2004. Inter- and intra-annual variations in yield, variation in fish length and general characteristics of the fishing are reported. The annual pacu yield ranged from 33,000kg to 146,000kg (average = 86,585kg), representing from 6.6% to 20.45% of the total landings in the studied period. These variations followed the hydrologic cycle, and the greatest yields were recorded in the years following the highest water levels. The monthly production ranged from 0 to 42,366kg (average = 5,772kg) and it was related to reproductive migration. The pacu presented variations in standard length from 14 to 20cm (18.72cm ± 3.69, mean ± sd). The fishing was based on the use of seines and gill nets and the main environments of capture were tributaries of the low Madeira River (Jamari, Oropiara, Machado and Novo Aripuanã). The CPUE calculated for 2003 to 2005 was 15kg*fisherman 1day-1 (sd = ±21). The results show that the category constituted during this period an important resource for local commercial exploitations, as verified in other regions of the Amazon.

Many commentators highlight the fertility of Anthropogenic Dark Earths (ADE), emphasizing their potential for sustainable agriculture. Some scholars believe that terra mulata (the less fertile, more extensive form of ADE) was created by means of agricultural practices used by large settled populations of pre-Columbian farmers. But what was it that these Amerindian farmers were growing? Until recently, scholarly consensus held that manioc does not perform well on ADE. New research on the middle Madeira River is showing, however, that this consensus was premature. In this region, the most common crop in ADE fields is bitter manioc. Farmers there have various landraces of manioc that they believe yield particularly well on ADE, and logically plant more of these varieties on ADE. Aspects of the behaviour and perception of manioc cultivation among 52 farmers at the community of Barro Alto were measured quantitatively on four terra firme soil types (Terra Preta, Terra Mulata, Oxisols and Ultisols). These farmers plant different configurations of landraces in different soils, according to their perception of the suitability of particular landraces and their characteristics to certain soil types and successional processes.This, in turn, shapes selective pressures on these varieties, as new genetic material incorporated from volunteer seedlings is more likely to contain traits present in the most prevalent landrace(s) in each soil type. Owing to localized population pressure at Barro Alto, manioc is under more intensive cultivation systems, with shorter cropping periods (5-10 months) and shorter fallow periods (1-2 years). The outcome of these processes is different co-evolutionary dynamics on ADE as opposed to non-anthropogenic soils. Further anthropological study of manioc swiddening in one of the richest agricultural environments in Amazonia can fill a gap in the literature, thus opening an additional window on the pre-Columbian period.

Over the last 20 years several projects carried on the Madeira River basin in the Amazon produced a great amount data on total Hg concentration in different fish species. In this paper we discuss temporal trends in Hg contamination and its relation to body weight in some of those fishes, showing that even within similar groups, such as carnivorous and non-migratory fish, the interspecies variability in Hg accumulation is considerable.Vários estudos têm sido desenvolvidos nos últimos 20 anos na bacia do Rio Madeira (Amazônia) com o objetivo de diagnosticar a presença de mercúrio em peixes e compreender o ciclo deste elemento no meio ambiente tropical. Neste artigo são discutidas tendências temporais na concentração de Hg e sua relação com a massa corporal de algumas espécies de peixes com diferentes hábitos alimentares, coletadas no Rio Madeira e no reservatório da hidroelétrica de Samuel, no Rio Jamari, Estado de Rondônia. Foi avaliada uma amostragem de peixes de 14 anos (1987 - 2000) com 86 espécies e um total de 1100 espécimes.

A adequação das estratégias do pescador à sazonalidade existente na Amazônia atesta o nível de conhecimento tradicional em relação à ecologia dos peixes e às variações da pesca nesse ambiente, como ocorre em outras regiões do Brasil. Nesse sentido, este trabalho teve como objetivo analisar a utilização dos ambientes de captura e a distribuição do esforço de pesca pela frota comercial em função do ciclo hidrológico. Foram coletados diariamente, entre junho de 2003 e maio de 2004, dados de desembarque e das expedições de pesca que ocorreram na região do Médio rio Madeira e submetidos à estatística descritiva. Os resultados mostraram que existiu uma tendência de aumento no esforço de pesca durante o período da enchente pelas embarcações da frota local, para compensar a queda na produção capturada. Os barcos de pesca e canoas motorizadas apresentaram valores médios de CPUE de 22,9 e 20,6 kg/pescador*dia, respectivamente. Ficou evidenciada também a maior utilização dos ambientes igarapés e lagos pelos pescadores de canoas motorizadas e do rio pelos pescadores dos barcos.The adaptation of the strategies of the fisherman to the seasonality in the Amazonian attests the level of traditional ecological knowledge in relation to the fish and to the variations of the fishing in that environment, as it happens in other regions of Brazil. In that sense the present work aimed to analyze the use of the fishing grounds and the distribution of the fishing effort by the commercial fleet in relation to the hydrological cycle. Data of fishing landings and fishing expeditions of the Medium Madeira River region were collected daily, from June of 2003 until May of 2004, and submitted to the descriptive statistics. The results showed that there was a tendency towards an increase in the fishing effort during the rising water season for the vessels of the local fleet, to compensate for the decrease in the captured production. The fishing boats and motorized canoes presented medium values of CPUE 22.9 and 20.6 kg/fisherman*day, respectively. It was also shown that fishermen of motorized canoes utilized the stream and lake environments the most, where as boat fishermen relied mainly on the river environment.

Selenium (Se) is an essential micronutrient that exerts multiple functions in the organism, and both its deficiency and excess can cause health impairments. Thus, it is important to monitor its levels in the population, especially in vulnerable groups, such as children from the Brazilian Amazon region, where there is a lack of information in this regard. The aim of this research was to study Se levels in the whole blood of children and teenagers (5-16 years old) from two riparian communities at the Madeira River (Cuniã RESEX and Belmont). Se level variations related to the communities' location, seasonality, diet, and body mass index (BMI) were assessed. Blood samples were collected in both communities for Se determinations, using ICP-MS and hemogram analyses, during May and September of 2011. Food frequency questionnaires were applied to assess consumption rates of specific food items. Non-parametric tests and linear multiple regressions were applied in the data analyses. Median Se levels were significantly higher during May (Cuniã RESEX 149 μg L; Belmont 85 μg L) compared to September (Cuniã RESEX 79 μg L; Belmont 53 μg L). No significant differences were found between the communities regarding BMI measurements and anemia prevalence. However, Se blood levels were significantly higher at the Cuniã RESEX compared to Belmont. In addition, the former showed higher fish and Brazil nut intakes, which may be the main Se sources for this community. These results contribute to a better understanding of Se reference levels for children and teenagers of Western Amazon riparian communities. [ABSTRACT FROM AUTHOR]

This work evaluates natural soil fertility on plain and flooded terrace areas, at Madeira River-RO fluvial plain, based on physics and chemicals analyses, (pH, OM, Al+2 + H+, exchange bases K+; Ca+2; Mg+2 e Al+3), physic-chemical (CEC, m% and V%), from the city of Porto Velho-RO to the city of Humaitá-AM. This kind of soil analysis is accomplished based on the percentage of base saturation (V%), which consists on physic-chemical phenomenon of ion absorption on clay and organic matter (OM) minerals. The soil samples were collected from temporary flooded plain strips and fluvial terraces with 20 km of intervals and 10 profiles described along the way, totalizing forty one (41) horizons. Using the EMBRAPA (1997) methods, the horizons A and B of each profile were considered. The results indicate four profiles with natural fertility deficiency: the Yellow Latosols at profile 1 and 2, Plintosols at profile 6 and Fluvic Neosols at profile 10, which may be related to the soil acidity, associated with high values of Al+3, as well on plain soils (Plintosols and Fluvic Neosols), as fluvial terrace (Latosols). Soils under the influence of flooding regime present high V%. The potential CEC values of analyzed horizons, were found low in consequence of the mineral composition of the clay, its values were correlated to the OM activities. However, the highest clay samples activities have been found on the superficial horizon of Plintosols at profile 6 (Cavalcante Community), where the potential CEC has arisen despite of reduction of OM content. The CEC varies from soil to soil, and what determine its values are the organic colloid/clay structures and the quantity of OM.

The extraction of gold in the Amazon, since 1970, has grown fast from a politic that was resulted in the creation of gold extraction reserves in this region. In the Madeira River the gold exploration is noticeable because of the deposition of mercury in the environment. This metal is toxic and it resists to degradation process, transforming itself chemically, till it gets to its organic form, known as very toxic. Its extensive usage in the gold recover has caused impacts to the environment and consequently to the population, according to studies already done. This study has as its goal to value the pollution by Hg in soils and the variation according to soil fractions. The soils were collected by profiles in 10 areas in the Madeira River. The determination of organic matter was done, according (BRASIL, 1999).To Hg determination it was selected the fraction