Journal articles: 'Amazon River region'

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Oliveira-da-Costa, Marcelo, Miriam Marmontel, Daiane S. X. da-Rosa, André Coelho, Serge Wich, Federico Mosquera-Guerra, and Fernando Trujillo. "Effectiveness of unmanned aerial vehicles to detect Amazon dolphins." Oryx 54, no. 5 (October 23, 2019): 696–98. http://dx.doi.org/10.1017/s0030605319000279.

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AbstractQuantifying the abundance of species is essential for their management and conservation. Much effort has been invested in surveys of freshwater dolphins in the Amazon basin but river dimensions and complex logistics limit replication of such studies across the region. We evaluated the effectiveness of using unmanned aerial vehicles (UAVs) for surveying two Amazon dolphin species, the tucuxi Sotalia fluviatilis and pink river dolphin Inia geoffrensis, in tropical rivers. In 2016 we conducted drone and visual surveys over 80 km of the Juruá River in Brazil. The aerial surveys provided higher accuracy than human observers in counting individuals detected in groups. Compared to estimates derived from visual surveys, the use of UAVs could provide a more feasible, economical and accurate estimate of Amazon river dolphin populations. The method could potentially be replicated in other important areas for the conservation of these species, to generate an improved index of river dolphin populations in the Amazon.

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Rocha da Silva, Maria do Socorro, Eduardo Antonio Ríos-Villamizar, Hillândia Brandão da Cunha, Sebastião Átila Fonseca Miranda, Sávio José Filgueiras Ferreira, Sergio R. Bulcão Bringel, Núbia Abrantes Gomes, Domitila Pascoaloto, and Luana Monteiro Silva. "A CONTRIBUTION TO THE HYDROCHEMISTRY AND WATER TYPOLOGY OF THE AMAZON RIVER AND ITS TRIBUTARIES." Caminhos de Geografia 20, no. 72 (December 23, 2019): 360–74. http://dx.doi.org/10.14393/rcg207246295.

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The geological diversity of the Amazon Basin, as well as the pluvial regime, influences the characteristics of the waters. To know the water types of the rivers of the Amazon basin, 288 superficial water samples were collected, 94 of them along the Amazon River and 194 in their tributaries, from March 2009 to September 2012. The physical, chemical, and physicochemical properties were analyzed. Rivers with pH between 6.5 and 7.6 and electrical conductivity (40.00 - 80.00 μS cm-1) are water bodies that are influenced by the Andean region (e.g., the Amazon River and some of its right bank tributaries). On the other hand, the rivers with pH in the range of 3.5 to 5.5 and conductivity <30.00 μS cm-1, which are Amazon River’s left bank tributaries, reflect the characteristics of the Guiana Shield. The rivers with pH (6.0 to 7.0), low ionic charge, and conductivity <40.0 μS cm-1, such as the lower Amazon River’s right bank tributaries (Tapajos and Xingu) which are influenced by the Central Brazilian Shield, and also the middle/upper Amazon River’s right bank tributaries (Tefé, Coari and Jutaí).

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KANE, R. P. "Inter-annual variability of rainfalls in the Amazon basin and its vicinity." MAUSAM 58, no. 3 (November 26, 2021): 351–60. http://dx.doi.org/10.54302/mausam.v58i3.1330.

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An analysis of the rainfall series (12-month running means) of the 5° × 5° gridded data in the Amazon river basin and its vicinity (15° N – 20° S, 30° - 80° W) indicated that the rainfalls were highly variable both from year to year and from region to region. Correlations with even nearby regions hardly exceeded 0.50, though correlations were better (up to 0.70) in the regions near the eastern coast of Brazil. Moderate relationship with ENSO indices was obtained for the Amazon river basin and the regions to its north, and for NE Brazil, while moderate relationship with South Atlantic SST was obtained for NE Brazil and the region immediately to its west. All other relationships (with 30 hPa wind, North Atlantic Oscillation Index, etc.) were obscure.

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Nittrouer, Charles A., David J. DeMaster, Steven A. Kuehl, Alberto G. Figueiredo, Richard W. Sternberg, L. Ercilio C. Faria, Odete M. Silveira, et al. "Amazon Sediment Transport and Accumulation Along the Continuum of Mixed Fluvial and Marine Processes." Annual Review of Marine Science 13, no. 1 (January 3, 2021): 501–36. http://dx.doi.org/10.1146/annurev-marine-010816-060457.

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Sediment transfer from land to ocean begins in coastal settings and, for large rivers such as the Amazon, has dramatic impacts over thousands of kilometers covering diverse environmental conditions. In the relatively natural Amazon tidal river, combinations of fluvial and marine processes transition toward the ocean, affecting the transport and accumulation of sediment in floodplains and tributary mouths. The enormous discharge of Amazon fresh water causes estuarine processes to occur on the continental shelf, where much sediment accumulation creates a large clinoform structure and where additional sediment accumulates along its shoreward boundary in tidal flats and mangrove forests. Some remaining Amazon sediment is transported beyond the region near the river mouth, and fluvial forces on it diminish. Numerous perturbations to Amazon sediment transport and accumulation occur naturally, but human actions will likely dominate future change, and now is the time to document, understand, and mitigate their impacts.

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Cohen, Julia Clarinda Paiva, David Roy Fitzjarrald, Flávio Augusto Farias D'Oliveira, Ivan Saraiva, Illelson Rafael da Silva Barbosa, Adilson Wagner Gandu, and Paulo Afonso Kuhn. "Radar-observed spatial and temporal rainfall variability near the Tapajós-Amazon confluence." Revista Brasileira de Meteorologia 29, spe (December 2014): 23–30. http://dx.doi.org/10.1590/0102-778620130058.

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Standard Amazonian rainfall climatologies rely on stations preferentially located near river margins. River breeze circulations that tend to suppress afternoon rainfall near the river and enhance it inland are not typically considered when reporting results. Previous studies found surprising nocturnal rainfall maxima near the rivers in some locations. We examine spatial and temporal rainfall variability in the Santarém region of the Tapajós-Amazon confluence, seeking to describe the importance of breeze effects on afternoon precipitation and defining the areal extent of nocturnal rainfall maxima.We used three years of mean S band radar reflectivity from Santarém airport with a Z-R relationship appropriate for tropical convective conditions. These data were complemented by TRMM satellite rainfall estimates. Nocturnal rainfall was enhanced along the Amazon River, consistent with the hypothesis that these are associated with the passage of instability lines, perhaps enhanced by local channeling and by land breeze convergence. In the daytime, two rainfall bands appear in mean results, along the east bank of the Tapajós River and to the south of the Amazon River, respectively.

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Maslin, Mark A., and Stephen J. Burns. "Reconstruction of the Amazon Basin Effective Moisture Availability over the Past 14,000 Years." Science 290, no. 5500 (December 22, 2000): 2285–87. http://dx.doi.org/10.1126/science.290.5500.2285.

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Quantifying the moisture history of the Amazon Basin is essential for understanding the cause of rain forest diversity and its potential as a methane source. We reconstructed the Amazon River outflow history for the past 14,000 years to provide a moisture budget for the river drainage basin. The oxygen isotopic composition of planktonic foraminifera recovered from a marine sediment core in a region of Amazon River discharge shows that the Amazon Basin was extremely dry during the Younger Dryas, with the discharge reduced by at least 40% as compared with that of today. After the Younger Dryas, a meltwater-driven discharge event was followed by a steady increase in the Amazon Basin effective moisture throughout the Holocene.

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Yu, Di, Shidong Liu, Guangxue Li, Yi Zhong, Jun Liang, Jinghao Shi, Xue Liu, and Xiangdong Wang. "The River–Sea Interaction off the Amazon Estuary." Remote Sensing 14, no. 4 (February 20, 2022): 1022. http://dx.doi.org/10.3390/rs14041022.

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The Amazon River has the highest discharge in the world. Nevertheless, there is still a lack of the research on the interaction between river-diluted water and the ocean. This study used the remote sensing data (2008–2017) of the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Aqua satellite, and data of the currents, wind fields, sea surface temperature, and water depth. The river–sea interaction off the Amazon estuary was studied by analyzing the diffusion of river-diluted water and the distribution of surface suspended particulate matter (SPM). The results revealed that the Amazon estuary has a “filter effect,” whereby the distribution of the surface SPM exhibited significant spatial characteristics of being high in the nearshore area and low in the offshore area. Most of the SPM accumulated within the estuary in a fan shape, although some was distributed in the shallow water region of the continental shelf along the coasts on both sides of the estuary. The currents were found to limit the diffusion range of SPM. The flow direction and velocity of the North Brazil Current and the North Equatorial Countercurrent, which are largely driven by the magnitude of the trade wind stress, are the main forces controlling the long-distance diffusion of diluted water, thus forming unique river–sea interaction patterns in the Amazon estuary. This research provides a supplement and reference for the study of the diffusion process of SPM and river-diluted water, and on the estuarine river–sea interactions of other large rivers worldwide.

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L., Maria Doris Escobar, Izeni P. Farias, Donald C. Taphorn B., Miguel Landines, and Tomas Hrbek. "Molecular diagnosis of the arowanas Osteoglossum ferreirai Kanazawa, 1966 and O. bicirrhossum (Cuvier, 1829) from the Orinoco and Amazon River basins." Neotropical Ichthyology 11, no. 2 (June 2013): 335–40. http://dx.doi.org/10.1590/s1679-62252013000200011.

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The arowanas, fishes of Gondwanan origin, are represented in South America by the genus Osteoglossum. All species were initially reported as being exclusive to the Amazon region, with O. ferreirai restricted to the Negro River basin and O. bicirrhosum to the Amazon and Essequibo Rivers basin. Starting in the mid 1970's it was reported that O. ferreirai also occurs in the Orinoco River basin. In all regions the arowanas assumed significant socio-economic importance due to their popularity in the international ornamental fish trade, leading to over-exploitation of both species in some areas. The Orinoco populations are particularly heavily exploited, and thus conservation and management measures are needed. Both depend on the clarification of taxonomic status, and phylogenetic distinctness of the Orinoco populations. With the goal of molecularly characterizing the two species of Osteoglossum, and comparing populations of Osteoglossum from the Orinoco and Amazon basins, we characterized individuals sampled from eight localities, one in the Orinoco River basin and seven in the Amazon River basin. We sampled 39 individuals, obtaining 1004 base pairs, of which 79 were synapomorphies. Genetic distance between the two species calculated using the HKY + G model of molecular evolution was 8.94%. Intraspecific distances ranged from 0.42% in O. bicirrhosum to 0.10% in O. ferreirai. The genetic characterization confirmed the taxonomic status of O. ferreirai in the Orinoco basin, and suggested that its distribution in the Orinoco basin is unlikely to be the result of vicariance or natural dispersal, but rather an anthropic introduction.

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Pereira, Fabiana da Silva, and Ima Célia Guimarães Vieira. "Anthropic transformation in the Gurupi river basin, eastern Amazon." Sustentabilidade em Debate 10, no. 3 (December 31, 2019): 212–35. http://dx.doi.org/10.18472/sustdeb.v10n3.2019.23799.

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The objective of this paper was to evaluate the degree of anthropic transformation of a river basin in the Amazon region. We used the digital data of the TerraClass Project to calculate the Anthropic Transformation Index - ATI. In order to verify spatial and temporal changes along a decade in the Gurupi river basin, we used the database of the years 2004 and 2014. The results showed an increase of anthropic changes in the basin over a decade, as a result of forest cover conversion into agricultural and pastures areas. Although the Gurupi river basin remains at a regular level of degradation after a decade, the intensification of land use and land cover change is a threat to the few rainforest remnants of the river basin, which can lead the region to the next level of degradation, if effective forest protection, conservation and restoration actions are not implemented in the region.

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Godoy, Fernando Igor de, Edson Guilherme, Diego Pedroza, and Ricardo Antônio de Andrade Plácido. "Avifauna of the upper Purus River: relevant records for an area lacking ornithological surveys." Papéis Avulsos de Zoologia 61 (February 18, 2021): e20216121. http://dx.doi.org/10.11606/1807-0205/2021.61.21.

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Birds are the best-known vertebrate group, although many localities in the world are considered to be knowledge gaps. This is the case of many little-known environments in the Amazon biome, the world’s largest tropical forest. Here, we present a survey of birds in the upper Purus basin, comprising the municipalities of Manoel Urbano and Feijó in the Brazilian state of Acre, and Boca do Acre and Pauini in the state of Amazonas. In this region, poorly-studied habitats, such as open rainforest dominated by palms or bamboo, still predominate. We recorded 452 bird species during 45 field trips between May and July in 2016, and June to August in 2017. Twenty-four of these species are associated with bamboo habitat, 28 are endemic to the southwestern Amazon basin, and seven are threatened with extinction. This high diversity is typical of the western Amazon basin, one of the richest regions in the world in the number of species, due to the heterogeneity of the local environments. The data presented here highlight the importance of the region for the conservation of birds, including species typical of the western Amazon, some of which are still poorly-known.

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de Sousa, Rodrigo Silva, Gilmar Clemente Silva, Thiago Bazzan, Fernando de la Torre, Caroline Nebo, Diógenes Henrique Siqueira-Silva, Sheila Cardoso-Silva, et al. "Connections among Land Use, Water Quality, Biodiversity of Aquatic Invertebrates, and Fish Behavior in Amazon Rivers." Toxics 10, no. 4 (April 7, 2022): 182. http://dx.doi.org/10.3390/toxics10040182.

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Rivers in the Amazon have among the greatest biodiversity in the world. The Xingu River, one of the tributaries of the Amazon River, has a length of 1640 km, draining 510,000 km2 in one of the most protected regions on the planet. The Middle Xingu region in Brazil has been highly impacted by mining and livestock farming, leading to habitat fragmentation due to altered water quality. Therefore, comparing two rivers (the preserved Xingu River and the impacted Fresco River) and their confluence, the aims of the present study were to (1) assess the land uses in the hydrographic basin; (2) determine the water quality by measurements of turbidity, total solids, and metals (Cd, Cu, Fe, Mn, Pb, Zn, and Hg); (3) compare the zooplankton biodiversity; and (4) to evaluate the avoidance behavior of fish (Astyanax bimaculatus) when exposed to waters from the Xingu and Fresco Rivers. Zooplankton were grouped and counted down to the family level. For the analysis of fish avoidance, a multi-compartment system was used. The forest class predominated at the study locations, accounting for 57.6%, 60.8%, and 63.9% of the total area at P1XR, P2FR, and P3XFR, respectively, although since 1985, at the same points, the forest had been reduced by 31.3%, 25.7%, and 27.9%. The Xingu River presented almost 300% more invertebrate families than the Fresco River, and the fish population preferred its waters (>50%). The inputs from the Fresco River impacted the water quality of the Xingu River, leading to reductions in local invertebrate biodiversity and potential habitats for fish in a typical case of habitat fragmentation due to anthropic factors.

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Carmo, Lucas, Alline Mota, and Cecilia Manoel. "Hemopneumothorax Caused By River Stingray Accident In The Amazon Region." Residência Pediátrica 8, no. 1 (April 2018): 51–54. http://dx.doi.org/10.25060/residpediatr-2018.v8n1-09.

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Valerio, Aline de M., Milton Kampel, Vincent Vantrepotte, Nicholas D. Ward, and Jeffrey E. Richey. "Optical Classification of Lower Amazon Waters Based on In Situ Data and Sentinel-3 Ocean and Land Color Instrument Imagery." Remote Sensing 13, no. 16 (August 4, 2021): 3057. http://dx.doi.org/10.3390/rs13163057.

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Optical water types (OWTs) were identified from an in situ dataset of concomitant biogeochemical and optical parameters acquired in the Amazon River and its tributaries, in the Lower Amazon region, at different hydrological conditions from 2014 to 2017. A seasonal bio-optical characterization was performed. The k-means classification was applied to the in situ normalized reflectance spectra (rn(λ)), allowing the identification of four OWTs. An optical index method was also applied to the rn(λ) defining the thresholds of the OWTs. Next, level-3 Sentinel-3 Ocean and Land Color Instrument images representative of the seasonal discharge conditions were classified using the identified in situ OWTs as reference. The differences between Amazon River and clearwater tributary OWTs were dependent on the hydrological dynamics of the Amazon River, also showing a strong seasonal variability. Each OWT was associated with a specific bio-optical and biogeochemical environment assessed from the corresponding absorption coefficient values of colored dissolved organic matter (aCDOM) and particulate matter (ap), chlorophyll-a and suspended particulate matter (SPM) concentrations, and aCDOM/ap ratio. The rising water season presented a unique OWT with high SPM concentration and high relative contribution of ap to total absorption compared to the other OWTs. This bio-optical characterization of Lower Amazon River waters represents a first step for developing remote sensing inversion models adjusted to the optical complexity of this region.

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Shibuya, Akemi, and Jansen Zuanon. "Catfishes as prey items of Potamotrygonid stingrays in the Solimões and Negro rivers, Brazilian Amazon." Biota Neotropica 13, no. 1 (March 2013): 376–79. http://dx.doi.org/10.1590/s1676-06032013000100041.

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In spite of the fact that catfish have rarely been reported as food items in the diets of freshwater stingrays, they are commonly observed in the stomach contents of species inhabiting the Solimões and Negro rivers in the Brazilian Amazon. The stomach contents of six rays from the Solimões River and 64 from the Negro River were analyzed, and catfishes (distributed among the families Callichthyidae, Cetopsidae, Doradidae and Loricariidae) were found in the stomach contents of four and 10 of these rays, respectively, comprising a frequency of occurrence of 20%. These data indicate a relevant participation of catfishes in the diets of potamotrygonid rays in the Amazon, and may reflect the regional diversity and abundance of Siluriformes in the region.

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Ffield, Amy. "Amazon and Orinoco River Plumes and NBC Rings: Bystanders or Participants in Hurricane Events?" Journal of Climate 20, no. 2 (January 15, 2007): 316–33. http://dx.doi.org/10.1175/jcli3985.1.

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Abstract The Amazon and Orinoco River plumes and North Brazil Current (NBC) rings are investigated during the 1 June through 30 November Atlantic hurricane season to identify their impact on upper-ocean temperatures in the region and to draw attention to their potential role in hurricane maintenance and intensification. The analysis uses ocean temperature and salinity stratification data, infrared and microwave satellite-derived sea surface temperature (SST) data, and Atlantic tropical storm and hurricane tracks data. The Amazon–Orinoco River plume spreads into the western equatorial Atlantic Ocean forming an extensive (0°–20°N, 78°–33°W) 10–60-m-thick buoyant surface layer associated with the warmest surface temperatures (up to +3°C) in the region due to the freshwater barrier layer effect. At times the warm Amazon–Orinoco River plume is bisected by cool-surface NBC rings. For the 1960 to 2000 time period, 68% of all category 5 hurricanes passed directly over the historical region of the plume, revealing that most of the most destructive hurricanes may be influenced by ocean–atmosphere interaction with the warm plume just prior to reaching the Caribbean. Statistical analyses of tropical Atlantic SSTs and tropical cyclone wind speeds reveal a significant and unique relationship between warm (cool) SSTs in the Amazon–Orinoco River plume and stronger (weaker) tropical cyclone wind speeds between 35° and 55°W. This implies that warmer (cooler) plume SSTs due to increased (decreased) river discharge may directly contribute to a more (less) vigorous hurricane season.

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DE OLIVEIRA, ELANE D. CUNHA, ALAN C. DA CUNHA, NATALINA B. DA SILVA, RAQUEL CASTELO-BRANCO, JOÃO MORAIS, MARIA PAULA C. SCHNEIDER, SILVIA M. M. FAUSTINO, VITOR RAMOS, and VITOR VASCONCELOS. "Morphological and molecular characterization of cyanobacterial isolates from the mouth of the Amazon River." Phytotaxa 387, no. 4 (January 11, 2019): 269. http://dx.doi.org/10.11646/phytotaxa.387.4.1.

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The Amazon region contains a great diversity of species, and the Amazon River basin accounts for almost 20% of all the freshwater in the world. Despite the favorable environmental conditions in this region, little is known about the cyanobacterial diversity of this waterbody, especially at the mouth of the river. In this paper, we used the polyphasic approach to identify 14 cyanobacterial strains isolated in the Amazon River on the inlet site from a drinking water supply located close to the river mouth. The isolated strains were characterized based on morphology, behavior in culture, 16S rRNA gene sequencing, phylogenetic analysis and potential for toxin production. The isolated strains belong to seven different genera, namely, Alkalinema, Cephalothrix, Limnothrix, Leptolyngbya, Phormidium, Pseudanabaena and an unidentified Nostocales taxa that may represent a new genus. Strikingly, there were no new species, nor detection of gene clusters associated with cyanotoxin production. However, the phylogenetic placements of the Amazonian strains of Limnothrix and Pseudanabaena provide new insight into the taxonomy of these genera, reinforcing the need for taxonomic revision.

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Barcelos Neto, Aristóteles. "Festas para um nobre: ritual e (re)producao sociopolítica no Alto Xingu." Estudios Latinoamericanos 23 (December 31, 2003): 63–90. http://dx.doi.org/10.36447/estudios2003.v23.art4.

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Carvalho, Tiago P., Julio Araújo Flores, Jessica Espino, Giannina Trevejo, Hernan Ortega, Fernando C. Jerep, Roberto E. Reis, and James S. Albert. "Fishes from the Las Piedras River, Madre de Dios basin, Peruvian Amazon." Check List 8, no. 5 (September 1, 2012): 973. http://dx.doi.org/10.15560/8.5.973.

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We report results of an ichthyological survey on the Las Piedras basin, a tributary of the Madre de Dios River located in the southwestern portion of the Amazon Basin in southeastern Peru. Collections were made at low water (June, 2011) from 180 - 270 m elevation, within the Fitzcarrald Arch. This is the last of four expeditions to the region with the goal of comparing the ichthyofaunas across the headwaters of the largest tributary basins in the western Amazon: Juruá, Ucayali, Purús and Madre de Dios rivers. Twenty-one sites along the Las Piedras River and its tributaries were sampled and a total of 144 species belonging to 32 families and seven orders were captured and identified. The most diverse families were Characidae (34 spp.), Loricariidae (23 spp.), and Pimelodidae (19 spp.).

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FAVACHO, Breno Inglis, Jerson Rogério Pinheiro VAZ, André Luiz Amarante MESQUITA, Fábio LOPES, Antonio Luciano Seabra MOREIRA, Newton Sure SOEIRO, and Otávio Fernandes Lima da ROCHA. "Contribution to the marine propeller hydrodynamic design for small boats in the Amazon region." Acta Amazonica 46, no. 1 (March 2016): 37–46. http://dx.doi.org/10.1590/1809-4392201501723.

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ABSTRACTIn the Amazon, river navigation is very important due to the length of navigable rivers and the lack of alternative road networks. Boats usually operate in unfavorable conditions, since there is no hydrodynamic relation among propellers, geometry, and the dimensions of the boat hull. Currently, there is no methodology for propeller hydrodynamic optimization with low computational cost and easy implementation in the region. The aim of this work was to develop a mathematical approach for marine propeller design applied to boats typically found on Amazon rivers. We developed an optimized formulation for the chord and pitch angle distributions, taking into account the classical model of Glauert. A theoretical analysis for the thrust and torque relationships on an annular control volume was performed. The mathematical model used was based on the Blade Element Momentum Theory (BEMT). We concluded that the new methodology proposed in this work demonstrates a good physical behavior when compared with the theory of Glauert and the experimental data of the Wageningen B3-50 propeller.

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Paiva, R. C. D., W. Collischonn, M. P. Bonnet, and L. G. G. de Gonçalves. "On the sources of hydrological prediction uncertainty in the Amazon." Hydrology and Earth System Sciences 16, no. 9 (September 5, 2012): 3127–37. http://dx.doi.org/10.5194/hess-16-3127-2012.

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Abstract. Recent extreme events in the Amazon River basin and the vulnerability of local population motivate the development of hydrological forecast systems using process based models for this region. In this direction, the knowledge of the source of errors in hydrological forecast systems may guide the choice on improving model structure, model forcings or developing data assimilation systems for estimation of initial model states. We evaluate the relative importance of hydrologic initial conditions and model meteorological forcings errors (precipitation) as sources of stream flow forecast uncertainty in the Amazon River basin. We used a hindcast approach that compares Ensemble Streamflow Prediction (ESP) and a reverse Ensemble Streamflow Prediction (reverse-ESP). Simulations were performed using the physically-based and distributed hydrological model MGB-IPH, comprising surface energy and water balance, soil water, river and floodplain hydrodynamics processes. The model was forced using TRMM 3B42 precipitation estimates. Results show that uncertainty on initial conditions plays an important role for discharge predictability, even for large lead times (∼1 to 3 months) on main Amazonian Rivers. Initial conditions of surface waters state variables are the major source of hydrological forecast uncertainty, mainly in rivers with low slope and large floodplains. Initial conditions of groundwater state variables are important, mostly during low flow period and in the southeast part of the Amazon where lithology and the strong rainfall seasonality with a marked dry season may be the explaining factors. Analyses indicate that hydrological forecasts based on a hydrological model forced with historical meteorological data and optimal initial conditions may be feasible. Also, development of data assimilation methods is encouraged for this region.

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Paiva, R. C. D., W. Collischonn, M. P. Bonnet, and L. G. G. Gonçalves. "On the sources of hydrological prediction uncertainty in the Amazon." Hydrology and Earth System Sciences Discussions 9, no. 3 (March 20, 2012): 3739–60. http://dx.doi.org/10.5194/hessd-9-3739-2012.

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Abstract. Recent extreme events in the Amazon River basin and the vulnerability of local population motivate the development of hydrological forecast systems (HFSs) using process based models for this region. In this direction, the knowledge of the source of errors in HFSs may guide the choice on improving model structure, model forcings or developing data assimilation (DA) systems for estimation of initial model states. We evaluate the relative importance of hydrologic initial conditions (ICs) and model meteorological forcings (MFs) errors (precisely precipitation) as sources of stream flow forecast uncertainty in the Amazon River basin. We used a hindcast approach developed by Wood and Lettenmaier (2008) that contrasts Ensemble Streamflow Prediction (ESP) and a reverse Ensemble Streamflow Prediction (reverse-ESP). Simulations were performed using the physically-based and distributed hydrological model MGB-IPH, comprising surface energy and water balance, soil water, river and floodplain hydrodynamics processes. Model was forced using TRMM 3B42 precipitation estimates. Results show that uncertainty on initial conditions play an important role for discharge predictability even for large lead times (~1 to 3 months) on main Amazonian Rivers. ICs of surface waters state variables are the major source of hydrological forecast uncertainty, mainly in rivers with low slope and large floodplains. ICs of groundwater state variables are important mostly during low flow period and southeast part of the Amazon, where lithology and the strong rainfall seasonality with a marked dry season may be the explaining factors. Analyses indicate that hydrological forecasts based on a hydrological model forced with historical meteorological data and optimal initial conditions, may be feasible. Also, development of DA methods is encouraged for this region.

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Santos, Geraldo Mendes dos. "Alfred Wallace's Echoes in the Amazon." World Journal of Social Science 6, no. 1 (January 22, 2019): 15. http://dx.doi.org/10.5430/wjss.v6n1p15.

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This article deals with some aspects of Alfred Russel Wallace's historic journey to the Amazon between 1848 and1852. In it are highlighted the impressions that this naturalist has pointed out about the region, cities, indigenouscustoms and especially about fish of the Black River. More objectively, the article discusses the reasons for the trip,the two trips to the Uaupés River, and the strategic visions Wallace presented about food production in that distantregion. At the end is outlined a profile of the personality of this famous traveler and the lessons he left to posterity,especially to the young naturalists and scientists.

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de Linage, C., J. S. Famiglietti, and J. T. Randerson. "Forecasting terrestrial water storage changes in the Amazon Basin using Atlantic and Pacific sea surface temperatures." Hydrology and Earth System Sciences Discussions 10, no. 10 (October 15, 2013): 12453–83. http://dx.doi.org/10.5194/hessd-10-12453-2013.

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Abstract. Floods and droughts frequently affect the Amazon River basin, impacting transportation, river navigation, agriculture, and ecosystem processes within several South American countries. Here we examined how sea surface temperatures (SSTs) influence interannual variability of terrestrial water storage anomalies (TWSAs) in different regions within the Amazon basin and propose a modeling framework for inter-seasonal flood and drought forecasting. Three simple statistical models forced by a linear combination of lagged spatial averages of central Pacific (Niño 4 index) and tropical North Atlantic (TNAI index) SSTs were calibrated against a decade-long record of 3°, monthly TWSAs observed by the Gravity Recovery And Climate Experiment (GRACE) satellite mission. Niño 4 was the primary external forcing in the northeastern region of the Amazon basin whereas TNAI was dominant in central and western regions. A combined model using the two indices improved the fit significantly (p < 0.05) for at least 64% of the grid cells within the basin, compared to models forced solely with Niño 4 or TNAI. The combined model explained 66% of the observed variance in the northeastern region, 39% in the central and western regions, and 43% for the Amazon basin as a whole with a 3 month lead time between the SST indices and TWSAs. Model performance varied seasonally: it was higher than average during the rainfall wet season in the northeastern Amazon and during the dry season in the central and western regions. The predictive capability of the combined model was degraded with increasing lead times. Degradation was smaller in the northeastern Amazon (where 49% of the variance was explained using an 8 month lead time vs. 69% for a 1 month lead time) compared to the central and western Amazon (where 22% of the variance was explained at 8 months vs. 43% at 1 month). These relationships may enable the development of an early warning system for flood and drought risk. This work also strengthens our understanding of the mechanisms regulating interannual variability in Amazon fires, as water storage deficits may subsequently lead to decreases in transpiration and atmospheric water vapor that cause more severe fire weather.

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Diodato, Nazzareno, Naziano Filizola, Pasquale Borrelli, Panos Panagos, and Gianni Bellocchi. "The Rise of Climate-Driven Sediment Discharge in the Amazonian River Basin." Atmosphere 11, no. 2 (February 18, 2020): 208. http://dx.doi.org/10.3390/atmos11020208.

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The occurrence of hydrological extremes in the Amazon region and the associated sediment loss during rainfall events are key features in the global climate system. Climate extremes alter the sediment and carbon balance but the ecological consequences of such changes are poorly understood in this region. With the aim of examining the interactions between precipitation and landscape-scale controls of sediment export from the Amazon basin, we developed a parsimonious hydro-climatological model on a multi-year series (1997–2014) of sediment discharge data taken at the outlet of Óbidos (Brazil) watershed (the narrowest and swiftest part of the Amazon River). The calibrated model (correlation coefficient equal to 0.84) captured the sediment load variability of an independent dataset from a different watershed (the Magdalena River basin), and performed better than three alternative approaches. Our model captured the interdecadal variability and the long-term patterns of sediment export. In our reconstruction of yearly sediment discharge over 1859–2014, we observed that landscape erosion changes are mostly induced by single storm events, and result from coupled effects of droughts and storms over long time scales. By quantifying temporal variations in the sediment produced by weathering, this analysis enables a new understanding of the linkage between climate forcing and river response, which drives sediment dynamics in the Amazon basin.

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Carvalho, Fernando R., Lilian Casatti, Angelo R. Manzotti, and Délcero C. W. Ravazzi. "First record of Arapaima gigas (Schinz, 1822) (Teleostei: Osteoglossomorpha), the “pirarucu”, in the upper Paraná River basin, Southeast Brazil." Check List 11, no. 5 (September 9, 2015): 1729. http://dx.doi.org/10.15560/11.5.1729.

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Arapaima gigas (Schinz), the “pirarucu”, is one of largest freshwater fish of the Neotropical region, naturally occurring in the Amazon, Essequibo, and Orinoco river basins. Herein, it is first recorded from the Grande River, in the upper Paraná River basin. This record is based on the finding of one dead specimen on the left margin of the Grande River, and in situ observation of juveniles and adults in the river.

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Giffard, Pierrick, William Llovel, Julien Jouanno, Guillaume Morvan, and Bertrand Decharme. "Contribution of the Amazon River Discharge to Regional Sea Level in the Tropical Atlantic Ocean." Water 11, no. 11 (November 8, 2019): 2348. http://dx.doi.org/10.3390/w11112348.

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The Amazon River is by far the largest river by volume of water in the world, representing around 17% of the global riverine discharge to the oceans. Recent studies suggested that its impact on sea level is potentially important at global and regional scales. This study uses a set of regional simulations based on the ocean model NEMO to quantify the influence of the Amazon runoff on sea level in the Tropical Atlantic Ocean. The model is forced at its boundaries with daily fields from the ocean reanalysis GLORYS2V4. Air-sea fluxes are computed using atmospheric variables from DFS5.2, which is a bias-corrected version of ERAinterim reanalysis. The particularity of this study is that interannual daily runoffs from the up-to-date ISBA-CTRIP land surface model are used. Firstly, mean state of sea level is investigated through a comparison between a simulation with an interannual river discharge and a simulation without any Amazon runoff. Then, the impact of the Amazon River on seasonal and interannual variability of sea level is examined. It was shown that the Amazon River has a local contribution to the mean state sea level at the river mouth but also a remote contribution of 3.3 cm around the whole Caribbean Archipelago, a region threatened by the actual sea level rise. This effect is mostly due to a halosteric sea level contribution for the upper 250 m of the ocean. This occurs in response to the large scale advection of the plume and the downward mixing of subsurface waters at winter time. The Amazon discharge also induces an indirect thermosteric sea level contribution. However, this contribution is of second order and tends to counterbalance the halosteric sea level contribution. Regional mass redistributions are also observed and consist in a 8 cm decrease of the sea level at the river mouth and a 4.5 increases on continental shelves of the Gulf of Mexico and Caribbean Sea. In terms of variability, simulations indicate that the Amazon discharge may contributes to 23% and 12% of the seasonal and interannual sea level variances in the Caribbean Archipelago area. These variances are first explained by the Amazon time mean discharge and show very weak sensitivity to the seasonal and interannual variability of the Amazon runoff.

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McClain, Michael E., and Rosa E. Cossío. "The use of riparian environments in the rural Peruvian Amazon." Environmental Conservation 30, no. 3 (September 2003): 242–48. http://dx.doi.org/10.1017/s0376892903000237.

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River margins are valued for agriculture in the western Amazon because of their fertile soils and level surfaces. Riparian forests along river margins also provide valuable ecosystem services by protecting water quality and providing resources to aquatic organisms. Because inhabitants of the region rely on these aquatic resources, riparian deforestation may have unintended negative feedbacks on the health and well-being of rural communities. A survey of 79 households of mixed cultural background investigated how riparian environments were used, what mechanisms were in place for their conservation, and how local people valued them. Corn, beans and peanuts were cultivated preferentially in riparian areas, complementing the manioc and plantains grown on upland soils. People valued riparian areas for their ecosystem services and generally left a protective buffer of forest along rivers. Both the agricultural and ecological values of riparian areas may be preserved through proper management.

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Marengo, José A., Carlos A. Nobre, Javier Tomasella, Marcos D. Oyama, Gilvan Sampaio de Oliveira, Rafael de Oliveira, Helio Camargo, Lincoln M. Alves, and I. Foster Brown. "The Drought of Amazonia in 2005." Journal of Climate 21, no. 3 (February 1, 2008): 495–516. http://dx.doi.org/10.1175/2007jcli1600.1.

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Abstract In 2005, large sections of southwestern Amazonia experienced one of the most intense droughts of the last hundred years. The drought severely affected human population along the main channel of the Amazon River and its western and southwestern tributaries, the Solimões (also known as the Amazon River in the other Amazon countries) and the Madeira Rivers, respectively. The river levels fell to historic low levels and navigation along these rivers had to be suspended. The drought did not affect central or eastern Amazonia, a pattern different from the El Niño–related droughts in 1926, 1983, and 1998. The choice of rainfall data used influenced the detection of the drought. While most datasets (station or gridded data) showed negative departures from mean rainfall, one dataset exhibited above-normal rainfall in western Amazonia. The causes of the drought were not related to El Niño but to (i) the anomalously warm tropical North Atlantic, (ii) the reduced intensity in northeast trade wind moisture transport into southern Amazonia during the peak summertime season, and (iii) the weakened upward motion over this section of Amazonia, resulting in reduced convective development and rainfall. The drought conditions were intensified during the dry season into September 2005 when humidity was lower than normal and air temperatures were 3°–5°C warmer than normal. Because of the extended dry season in the region, forest fires affected part of southwestern Amazonia. Rains returned in October 2005 and generated flooding after February 2006.

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Costa, Marcondes, Luiz Carvalho, Patricia Pereira, and Glayce Valente. "IMPACTS OF URBAN DEVELOPMENT ON AN OXBOW LAKE IN THE AMAZON REGION: LANDSCAPE AND GEOCHEMICAL EVIDENCE." BOLETIM DO MUSEU DE GEOCIÊNCIAS DA AMAZÔNIA 7 (2020), no. 2 (December 1, 2020): 1–12. http://dx.doi.org/10.31419/issn.2594-942x.v72020i2a6mlc.

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Amapá Lake is an abandoned meander of the Acre River, the margins of which are occupied by agricultural settlements, smallholdings, fish farms and dirt roads. This paper discusses the impact of this occupation on the lake area based on field data and physical-chemical and elementary chemical analyses of the lake and river waters. The strong physical changes in the lake landscape have impacted the quality of its water. During the dry season (low water), when the temperature of the water reaches 30-34ºC, there is a proliferation of green algae and in the area affected by fish farms and smallholdings there is an increase in total dissolved solids, electrical conductivity, and transparency, while turbidity and total suspended solids become more concentrated during the flood season. The anthropogenic impact is also indicated by the higher levels of ammonia, chlorides, bromides, and phosphates in the water. However, the concentrations of dissolved metal ions are all consistent with those found in the Acre River, and other muddy water lakes and rivers in the Amazon basin, reflecting the mineralogy of the suspended material. The concentrations of most heavy metals (Pb, Cu, (Zn), Cd and Hg) are below 0.01 mg L-1, while that of Hg (0.006 mg L-1) is above the recommended limits for human consumption. Overall, the results of the study indicate that Amapá Lake is suffering ongoing impacts (physical and chemical) from urban development, which are mitigated by the periodic flooding of the river. Key words: Urban expansion, Environmental impacts, Waters, Heavy metals.

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Rostain, Stéphen. "WHERE THE AMAZON RIVER MEETS THE ORINOCO RIVER. ARCHAEOLOGY OF THE GUIANAS." Amazônica - Revista de Antropologia 4, no. 1 (June 16, 2012): 10. http://dx.doi.org/10.18542/amazonica.v4i1.880.

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Archaeological and interdisciplinary investigations conducted in the Guianas during these last 35 years offer a new picture of the pre-Columbian Guianas. Although archaeology still is relatively incipient in the Guianas, it is possible to draw up a panorama of the prehistory of this huge region. During the last millennium before the European Conquest, Guianas coast was divided into two main territories dominated by two different cultural entities. Cayenne Island in French Guiana was the key-area marking the boundary between two cultural traditions. Western coast up to the Guyana was dominated by cultures linked to the Arauquinoid Tradition originated in the Middle Orinoco. Eastern coast was occupied by cultures belonging to the Polychrome Tradition of the Lower Amazon. These two cultural entities grew up from ca. AD 600 up to their destruction by the European Conquest. Keywords: Archaeology, Guianas, arauquinoid tradition, polychrome tradition

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Campos, C. P., M. F. Catarino, and C. E. C. Freitas. "Stock assessment of the peacock bass Cichla temensis (Humboldt, 1821), an important fishing resource from the middle Negro river, Amazonas, Brazil." Brazilian Journal of Biology 80, no. 3 (September 2020): 506–10. http://dx.doi.org/10.1590/1519-6984.203124.

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Abstract Peacock bass Cichla temensis is an important species at the Amazon basin, since commercial, subsistence and recreational fisheries simultaneously exploit it. Cichla temensis is the preferred species by recreational fishers and it has been strongly exploited, mainly at the Negro river, the second largest tributary of the Amazon River. It was used data from experimental fisheries, collected at the middle stretch of Negro river, which were coupled with previously published data on its population dynamics, to run a yield per recruit model and build scenarios of sustainable fisheries. The results showed that the age of the first catch is a key variable to successful management of the peacock bass stocks at this region.

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Behling, Hermann, and Marcondes Lima da Costa. "Holocene Environmental Changes from the Rio Curuá Record in the Caxiuanã Region, Eastern Amazon Basin." Quaternary Research 53, no. 3 (May 2000): 369–77. http://dx.doi.org/10.1006/qres.1999.2117.

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AbstractHolocene environments have been reconstructed by multiproxy studies of an 850-cm-long core from Rio Curuá dating to >8000 14C yr B.P. The low-energy river lies in the eastern Amazon rain forest in the Caxiuanã National Forest Reserve, 350 km west of Belem in northern Brazil. Sedimentological, mineralogical, and geochemical dates demonstrate that the deposits correspond to two different environments, sediments of an active river before 8000 14C yr B.P. and later a passive river system. The pollen analytical results indicate four different local and regional Holocene paleoenvironmental periods: (1) a transition to a passive fluvial system and a well-drained terra firme (unflooded upland) Amazon rain forest with very limited development of inundated forests (várzea and igapó) (>7990–7030 14C yr B.P.); (2) a sluggish river with a local Mauritia palm-swamp and similar regional vegetation, as before (7030–5970 14C yr B.P.); (3) a passive river, forming shallow lake conditions and with still-abundant terra firme forest in the study region (5970–2470 14C yr B.P.); and (4) a blocked river with high water levels and marked increase of inundated forests during the last 2470 14C yr B.P. Increased charcoal during this last period suggests the first strong presence of humans in this region. The Atlantic sea level rise was probably the major factor in paleoenvironmental changes, but high water stands might also be due to greater annual rainfall during the late Holocene.

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PRUDENTE, Bruno da S., Pedro CARNEIRO-MARINHO, Roberta de M. VALENTE, and Luciano F. de A. MONTAG. "Feeding ecology of Serrasalmus gouldingi (Characiformes: Serrasalmidae) in the lower Anapu River region, Eastern Amazon, Brazil." Acta Amazonica 46, no. 3 (September 2016): 259–70. http://dx.doi.org/10.1590/1809-4392201600123.

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Abstract Studies on feeding ecology of fishes are important to understand the relationship between species and environmental seasonal variations. In tropical rivers, these relationships are mainly modeled by hydrological patterns. Thereby, this study aimed to assess the influence of fluviometric variation and life stage (juveniles and adults) in the feeding ecology of Serrasalmus gouldingi in the lower Anapu River region, located in Eastern Amazon, Pará, Brazil. Specimens were collected bimonthly, considering four different hydrological periods. We assessed the diet composition, feeding intensity and niche breadth of the species. Thirty-two dietary items were identified and grouped into ten categories. A total of 279 stomachs were analyzed, showing a predominance of fish fragments, followed by fruits and seeds. The diet composition of S. gouldingi differed only between drought and flood season, although it did not differ between juveniles and adults. An increase in feeding intensity was recorded during the rise in the water level, with a lower feeding intensity observed during transitional season. Serrasalmus gouldingi showed lower niche breadth during flood season, attributed to the high consumption of fruits and seeds, presenting an omnivorous diet with high tendency towards piscivory. Although less evident than in other Amazon watersheds, the flood pulse in the lower Anapu River region is an important factor influencing the feeding ecology of the species.

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Frederico, Renata G., Izeni P. Farias, Maria Lúcia Góes de Araújo, Patricia Charvet-Almeida, and José A. Alves-Gomes. "Phylogeography and conservation genetics of the Amazonian freshwater stingray Paratrygon aiereba Müller & Henle, 1841 (Chondrichthyes: Potamotrygonidae)." Neotropical Ichthyology 10, no. 1 (2012): 71–80. http://dx.doi.org/10.1590/s1679-62252012000100007.

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The family Potamotrygonidae is monophyletic comprising three genera: Paratrygon Duméril, Potamotrygon Garman and Plesiotrygon Rosa, Castello & Thorson. The distribution of most species in this family is restricted to a single basin or fluvial system. Only Potamotrygon motoro, Potamotrygon orbignyi and Paratrygon aiereba are found in more than one river basin. In this study we investigate genetic structuring of Paratrygon aiereba, from five rivers of the Amazon region: Negro, Solimões-Amazon-Estuary system, Tapajós, Xingu and Araguaia. Sixty-three individuals were sequenced for ATPase 6, and a representative subsample of 27 individuals was sequenced for COI. The COI dataset analysis indicated that Paratrygon is sister to all other potamotrygonid genera and species. Population parameters inferred from the analysis of ATPase 6 sequences revealed that the populations of this species are structured within each river, with no or nearly non-existent gene flow occurring between rivers and a positive correlation between geographic and genetic distances. Paratrygon aiereba is comprised of three geographically restricted clades with K2P interclade distances of at least 2%. Intraspecific divergence within P. aiereba is similar to the interspecific divergence observed in Potamotrygon spp. sampled throughout the same geographic area. Using the premises of COI barcoding and the allopatric distribution of the three P. aiereba clades, the taxon P. aiereba most likely comprises three distinct biological species. Since freshwater stingrays of the family Potamotrygonidae are highly exploited for the aquarium trade, management and conservation strategies need to be implemented at the level of each river basin, rather than at the level of the Amazon basin.

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Zuloeta Bonilla, Rosa, Ramchandra Bhandari, and Aldo Pérez Rodarte. "Multi-attribute assessment of a river electromobility concept in the Amazon region." Energy for Sustainable Development 61 (April 2021): 139–52. http://dx.doi.org/10.1016/j.esd.2021.01.007.

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Costa, Wilson, Pedro Amorim, and Pedro H. N. Bragança. "A new miniature killifish of the genus Melanorivulus (Cyprinodontiformes: Rivulidae) from the Xingu river drainage, Brazilian Amazon." Vertebrate Zoology 64, no. 2 (July 15, 2014): 193–97. http://dx.doi.org/10.3897/vz.64.e31479.

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Melanorivulus rubroreticulatus, new species, is described on the basis of material collected in the lower section of the Xingu river drainage, Brazilian Amazon. It is a member of a group endemic to the region encompassing the southern Amazonas river tributaries and the Parnaíba river basin. The new species is distinguished from other congeners of this group by the presence of broad red bars on the caudal fin in males, bars often interconnected to form reticulations, and short red bars contrasting with intense light blue ground colour on the anal-fin base. It represents the northern-most record for the group, besides being the only species occurring in the Amazon rain forest and possibly is also the smallest one, barely surpassing 25 mm of standard length.

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Heckenberger, Michael J., J. Christian Russell, Joshua R. Toney, and Morgan J. Schmidt. "The legacy of cultural landscapes in the Brazilian Amazon: implications for biodiversity." Philosophical Transactions of the Royal Society B: Biological Sciences 362, no. 1478 (January 8, 2007): 197–208. http://dx.doi.org/10.1098/rstb.2006.1979.

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For centuries Amazonia has held the Western scientific and popular imagination as a primordial forest, only minimally impacted by small, simple and dispersed groups that inhabit the region. Studies in historical ecology refute this view. Rather than pristine tropical forest, some areas are better viewed as constructed or ‘domesticated’ landscapes, dramatically altered by indigenous groups in the past. This paper reviews recent archaeological research in several areas along the Amazon River with evidence of large pre-European ( ca 400–500 calendar years before the present) occupations and large-scale transformations of forest and wetland environments. Research from the southern margins of closed tropical forest, in the headwaters of the Xingu River, are highlighted as an example of constructed nature in the Amazon. In all cases, human influences dramatically altered the distribution, frequency and configurations of biological communities and ecological settings. Findings of historical change and cultural variability, including diverse small to medium-sized complex societies, have clear implications for questions of conservation and sustainability and, specifically, what constitutes ‘hotspots’ of bio-historical diversity in the Amazon region.

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Lopes, Gerson P., Tamily C. M. Santos, and Paúl M. Velazco. "First record of Vampyrodes caraccioli (Thomas, 1889) (Chiroptera, Phyllostomidae) in the state of Amazonas and its updated distribution in Brazil." Check List 12, no. 3 (June 22, 2016): 1909. http://dx.doi.org/10.15560/12.3.1909.

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Abstract: The present note reports the first record of Vampyrodes caraccioli in the Brazilian state of Amazonas, and the central Amazon region, based on 44 specimens caught in the Auati-Paraná Extractive Reserve, north bank of the Solimões/Amazonas River. Our record fills a distribution gap of this species in the Brazilian Amazon and illustrates that the current knowledge on the distribution of Amazonian bats is far from complete.

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de Linage, C., J. S. Famiglietti, and J. T. Randerson. "Statistical prediction of terrestrial water storage changes in the Amazon Basin using tropical Pacific and North Atlantic sea surface temperature anomalies." Hydrology and Earth System Sciences 18, no. 6 (June 4, 2014): 2089–102. http://dx.doi.org/10.5194/hess-18-2089-2014.

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Abstract. Floods and droughts frequently affect the Amazon River basin, impacting transportation, agriculture, and ecosystem processes within several South American countries. Here we examine how sea surface temperature (SST) anomalies influence interannual variability of terrestrial water storage anomalies (TWSAs) in different regions within the Amazon Basin and propose a statistical modeling framework for TWSA prediction on seasonal timescales. Three simple semi-empirical models forced by a linear combination of lagged spatial averages of central Pacific and tropical North Atlantic climate indices (Niño 4 and TNAI) were calibrated against a decade-long record of 3°, monthly TWSAs observed by the Gravity Recovery And Climate Experiment (GRACE) satellite mission. Niño 4 was the primary external forcing in the northeastern region of the Amazon Basin, whereas TNAI was dominant in central and western regions. A combined model using the two indices improved the fit significantly (p < 0.05) for at least 64% of the grid cells within the basin, compared to models forced solely with Niño 4 or TNAI. The combined model explained 66% of the observed variance in the northeastern region, 39% in the central and western region, and 43% for the Amazon Basin as a whole, with a 3-month lead time between the climate indices and the predicted TWSAs. Model performance varied seasonally: it was higher than average during the wet season in the northeastern Amazon and during the dry season in the central and western region. The predictive capability of the combined model was degraded with increasing lead times. Degradation rates were lower in the northeastern Amazon (where 49% of the variance was explained using an 8-month lead time versus 69% for a 1-month lead time) compared to the central and western Amazon (where 22% of the variance was explained at 8 months versus 43% at 1 month). These relationships may contribute to an improved understanding of the climate processes regulating the spatial patterns of flood and drought risk in South America.

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Coelho, Caroliny Almeida, Marta Regina Da Silva Pereira, and Bruno Sampaio Amorim. "Preliminary Angiosperm Checklist in an Area South of the Madeira River, Manicoré, Amazonas, Brazil." Acta Brasiliensis 4, no. 1 (January 20, 2020): 1. http://dx.doi.org/10.22571/2526-4338254.

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Due to the large extent of the Amazon rainforest, research has historically focused on easily accessible locations. Thus, much of this region has little information available about its richness and plant distribution. Located south of the Madeira river, Municipality of Manicoré has a high number of phytophysiognomies, which may indicate the existence of a greater diversity of plant species. Therefore, from the compilation of previously collected records and based on botanical expeditions, this study evaluated the diversity and richness of angiosperms in Manicoré. We found 801 species, 409 genera and 106 families. Our data record 47 new occurrences for Amazonas State. Of these new occurrences, 12 are also the first record for the northern region. In addition, we have identified a new vine species of the genus Mandevilla Lindl. Given the well-known sample deficiency of the Amazon region, and considering the countless anthropogenic pressures that cities south of the Madeira river have been facing, knowledge of flora becomes increasingly urgent.

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Santini, W., J. M. Martinez, R. Espinoza-Villar, G. Cochonneau, P. Vauchel, J. S. Moquet, P. Baby, et al. "Sediment budget in the Ucayali River basin, an Andean tributary of the Amazon River." Proceedings of the International Association of Hydrological Sciences 367 (March 3, 2015): 320–25. http://dx.doi.org/10.5194/piahs-367-320-2015.

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Abstract. Formation of mountain ranges results from complex coupling between lithospheric deformation, mechanisms linked to subduction and surface processes: weathering, erosion, and climate. Today, erosion of the eastern Andean cordillera and sub-Andean foothills supplies over 99% of the sediment load passing through the Amazon Basin. Denudation rates in the upper Ucayali basin are rapid, favoured by a marked seasonality in this region and extreme precipitation cells above sedimentary strata, uplifted during Neogene times by a still active sub-Andean tectonic thrust. Around 40% of those sediments are trapped in the Ucayali retro-foreland basin system. Recent advances in remote sensing for Amazonian large rivers now allow us to complete the ground hydrological data. In this work, we propose a first estimation of the erosion and sedimentation budget of the Ucayali River catchment, based on spatial and conventional HYBAM Observatory network.

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SOUMIS, Nicolas, Marc LUCOTTE, Delaine SAMPAIO, Diane C. ALMEIDA, Dalie GIROUX, Silmara MORAIS, and Pierre PICHET. "Presence of oOrganophosphate Insecticides in fish of the Amazon River." Acta Amazonica 33, no. 2 (June 2003): 325–38. http://dx.doi.org/10.1590/1809-4392200332338.

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Trace levels of three organophosphate insecticides (OPI) were detected in eight fish species from the region of Santarém, State of Pará, Brazil. Individual concentrations of OPI in fish ranged from less than the detection limit to 2,1 ppb. Mean concentrations of chlorpyrifos, malathion, and methyl-parathion were 0,3 ± 0,3, 0,1 ± 0,1, and 0,3 ± 0,3 ppb, respectively. Pellona flavipinnis, the largest and fattest piscivorous species analyzed, was the most contaminated. Since an inhabitant of this Amazonian region consumes 220 g of fish per day on average, ingested doses of chlorpyrifos, malathion, and methyl-parathion may reach up to 308, 220, and 462 ng·d-1, respectively. Compared to acceptable daily intakes (ADI), quantities of OPI absorbed via fish consumption on a daily basis are far below deleterious levels. We estimated that even considering the highest OPI contents detected, the average daily fish consumption of anadult of 60 kg would have to increase by ca. 1 950, 5 450, and 2 600 times to reach ADI of chlorpyrifos, malathion, and methyl-parathion, respectively. Neither fish diet nor fish lipid content enabled us to completely explain the interspecific differences observed.

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Rodríguez-Zorro, Paula A., Bruno Turcq, Renato C. Cordeiro, Luciane S. Moreira, Renata L. Costa, Crystal H. McMichael, and Hermann Behling. "Forest stability during the early and late Holocene in the igapó floodplains of the Rio Negro, northwestern Brazil." Quaternary Research 89, no. 1 (December 21, 2017): 75–89. http://dx.doi.org/10.1017/qua.2017.99.

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AbstractLocated at the northwestern part of the Amazon basin, Rio Negro is the largest black-water river in the world and is one of the poorest studied regions of the Amazon lowlands. In the middle-upper part of the Rio Negro were retrieved sediment cores form Lake Acarabixi, which were analyzed using pollen, spores, charcoal, and geochemistry. The aim of this study was to detect the influences from humans and river dynamics on the vegetation history in the region. Two main periods of vegetation and river dynamics were detected. From 10,840 to 8240 cal yr BP, the river had a direct influence into the lake. The lake had a regional input of charcoal particles, which reflected the effect of the dry Holocene period in the basin. Furthermore, highland taxa such asHedyosmumandMyrsinewere found at that time along with igapó forest species that are characteristic to tolerate extended flooding likeEschweilera,Macrolobium, Myrtaceae,Swartzia, andAstrocaryum. During the late Holocene (1600 to 650 cal yr BP), more lacustrine phases were observed. There were no drastic changes in vegetation but the presence of pioneer species likeVismiaandCecropia, along with the signal of fires, which pointed to human disturbances.

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Macedo, Rodrigo Santana, Wenceslau Geraldes Teixeira, Hedinaldo Narciso Lima, Adriana Costa Gil de Souza, Francisco Weliton Rocha Silva, Omar Cubas Encinas, and Eduardo Góes Neves. "Amazonian dark earths in the fertile floodplains of the Amazon River, Brazil: an example of non-intentional formation of anthropic soils in the Central Amazon region." Boletim do Museu Paraense Emílio Goeldi. Ciências Humanas 14, no. 1 (April 2019): 207–27. http://dx.doi.org/10.1590/1981-81222019000100013.

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ABSTRACT Amazonian dark earths (ADEs) are fertile soils created by pre-Columbian Amerindian societies of the Amazon Basin. However, it is still not clear whether these soils were produced intentionally to improve infertile Amazonian upland soils or if they resulted from the accumulation of organic matter from sedentary settlements. This study characterizes the ADEs found in the naturally fertile alluvial floodplains of the Amazon River in the Central Brazilian Amazon according to total, exchangeable, and available contents of elements and organic carbon in soil profiles. ADEs contained higher levels of available elements and total P, Ca, Zn, and Cu. High total Cr, Ni, Co, and V content in these soils indicate that mafic minerals contributed to their composition, while higher contents of P, Zn, Ba, and Sr indicate anthropic enrichment. The presence of ADEs in floodplain areas strongly indicates non-intentional anthropic fertilization of the alluvial soils, which naturally contain levels of P, Ca, Zn, and Cu higher than those needed to cultivate common plants. The presence of archaeological sites in the floodplains also shows that pre-Columbian populations lived in these regions as well as on bluffs above the Amazon River.

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Mansur, Maria C. D., and Daniel M. Pimpão. "Triplodon chodo, a new species of pearly fresh water mussel from the Amazon Basin (Mollusca: Bivalvia: Unionoida: Hyriidae)." Revista Brasileira de Zoologia 25, no. 1 (March 2008): 111–15. http://dx.doi.org/10.1590/s0101-81752008000100015.

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A new species of the genus Triplodon Spix, 1827 is described based on shell samples collected on Rivers Jamari (Rondônia State) and Aripuanã (Amazonas State) from the Madeira River Basin; on the Amazon at Oriximiná and on the mouth of Tapajós River at Alter do Chão (Pará State). Triplodon chodo is a new species considered closely related to T. stevensi Lea, 1871, (described from the part of the River Essequibo which borders the Guianas). Triplodon chodo is distinguished from the latter by its smaller, lighter shell, the absence of a wing in the anterior region and by the delicate shape of the external sculpture, which is composed of minuscule nodules organized in rows that converge and crosses on the centre of the valves. The straight and vertical posterior margin forms a right or slightly obtuse angle with the shell's dorsal and ventral margins. The anterior region is short, low and slightly tapering, with the distal extremity situated on the half of the shell height. The dorsal and ventral margins are equally curved.

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PRATA, EDUARDO MAGALHÃES BORGES, RANGEL BATISTA DE CARVALHO, and ALBERTO VICENTINI. "Pagamea spruceana (Rubiaceae, Gaertnereae), a new species from flooded white-sand forests in the Upper Rio Negro region, Brazil." Phytotaxa 269, no. 3 (August 5, 2016): 186. http://dx.doi.org/10.11646/phytotaxa.269.3.2.

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Pagamea spruceana, a new species from Northwestern Amazon, Brazil, is endemic to the Upper Rio Negro region, in the Içana and Uaupés River Basins, and differs from other functionally dioecious species of Pagamea by its capitate and puberulous inflorescences and narrowly elliptic leaf blades with revolute and puberulous margins. Pagamea spruceana is the only species in the genus known from long-term inundated habitats (igapós) in the Amazon. The new species is here described and the affinities with morphologically similar and closely related species are discussed.

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Müller, Letícia Morgana, Renato Kipnis, Mariane Pereira Ferreira, Sara Marzo, Bianca Fiedler, Mary Lucas, Jana Ilgner, Hilton P. Silva, and Patrick Roberts. "Late Holocene dietary and cultural variability on the Xingu River, Amazon Basin: A stable isotopic approach." PLOS ONE 17, no. 8 (August 3, 2022): e0271545. http://dx.doi.org/10.1371/journal.pone.0271545.

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Although once considered a ‘counterfeit paradise’, the Amazon Basin is now a region of increasing interest in discussions of pre-colonial tropical land-use and social complexity. Archaeobotany, archaeozoology, remote sensing and palaeoecology have revealed that, by the Late Holocene, populations in different parts of the Amazon Basin were using various domesticated plants, modifying soils, building earthworks, and even forming ‘Garden Cities’ along the Amazon River and its tributaries. However, there remains a relatively limited understanding as to how diets, environmental management, and social structures varied across this vast area. Here, we apply stable isotope analysis to human remains (n = 4 for collagen, n = 17 for tooth enamel), and associated fauna (n = 61 for collagen, n = 28 for tooth enamel), to directly determine the diets of populations living in the Volta Grande do Rio Xingu, an important region of pre-Columbian cultural interactions, between 390 cal. years BC and 1,675 cal. years AD. Our results highlight an ongoing dietary focus on C3 plants and wild terrestrial fauna and aquatic resources across sites and time periods, with varying integration of C4 plants (i.e. maize). We argue that, when compared to other datasets now available from elsewhere in the Amazon Basin, our study highlights the development of regional adaptations to local watercourses and forest types.

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Carvalho, Tiago P., S. June Tang, Julia I. Fredieu, Roberto Quispe, Isabel Corahua, Hernan Orteaga, and James S. Albert. "Fishes from the upper Yuruá river, Amazon basin, Peru." Check List 5, no. 3 (September 1, 2009): 673. http://dx.doi.org/10.15560/5.3.673.

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We report results of an ichthyological survey of the upper Rio Yuruá in southeastern Peru. Collections were made at low water (July-August, 2008) near the headwaters of the Brazilian Rio Juruá. This is the first of four expeditions to the Fitzcarrald Arch — an upland associated with the Miocene-Pliocene rise of the Peruvian Andes — with the goal of comparing the ichthyofauna across the headwaters of the largest tributary basins in the western Amazon (Ucayali, Juruá, Purús and Madeira). We recorded a total of 117 species in 28 families and 10 orders, with all species accompanied by tissue samples preserved in 100% ethanol for subsequent DNA analysis, and high-resolution digital images of voucher specimens with live color to facilitate accurate identification. From interviews with local fishers and comparisons with other ichthyological surveys of the region we estimate the actual diversity of fishes in the upper Juruá to exceed 200 species.

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Dias, Camila Loureiro. "Jesuit Maps and Political Discourse: The Amazon River of Father Samuel Fritz." Americas 69, no. 01 (July 2012): 95–116. http://dx.doi.org/10.1017/s0003161500001814.

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Long associated with the context of territorial disputes on the definition of the Amazon frontiers of the Iberian empires in the late seventeenth and early eighteenth centuries, the map of the Amazon River designed by Jesuit Samuel Fritz is as famous as it is misunderstood. The map is, in fact, quite poorly understood, in both the field of cartographic history, where it would certainly occupy a place of importance, and the nascent field of Amazon social history, where it often serves as a supporting illustration. In fact, even the context in which this map was produced raises disputes that require further study, distinct from those undertaken by nationalist historiographies of the countries that share borders in Amazonia. For example, few studies have been carried out regarding the means of territorial occupation and their inherent conflicts during the first centuries of European colonization of this region. It is precisely for such analysis that the map of Samuel Fritz stands as an important document for historians: more than simply rendering the course of the Amazon River it transmits a political discourse, as does any map, intrinsic to the context in which it was produced.

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Dias, Camila Loureiro. "Jesuit Maps and Political Discourse: The Amazon River of Father Samuel Fritz." Americas 69, no. 1 (July 2012): 95–116. http://dx.doi.org/10.1353/tam.2012.0052.

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Abstract:

Long associated with the context of territorial disputes on the definition of the Amazon frontiers of the Iberian empires in the late seventeenth and early eighteenth centuries, the map of the Amazon River designed by Jesuit Samuel Fritz is as famous as it is misunderstood. The map is, in fact, quite poorly understood, in both the field of cartographic history, where it would certainly occupy a place of importance, and the nascent field of Amazon social history, where it often serves as a supporting illustration. In fact, even the context in which this map was produced raises disputes that require further study, distinct from those undertaken by nationalist historiographies of the countries that share borders in Amazonia. For example, few studies have been carried out regarding the means of territorial occupation and their inherent conflicts during the first centuries of European colonization of this region. It is precisely for such analysis that the map of Samuel Fritz stands as an important document for historians: more than simply rendering the course of the Amazon River it transmits a political discourse, as does any map, intrinsic to the context in which it was produced.

Journal articles on the topic 'Amazon River region'

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