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1

Larval Pseudoproleptus sp. (Nematoda: Cystidicolidae) found in the Amazon river prawn Macrobrachium amazonicum (Decapoda: Palaemonidae) in Brazil.  

PubMed

Previously undescribed infective larvae of the cystidicolid nematode Pseudoproleptus sp. (probably conspecific with the nematode originally described as Heliconema izecksohni Fabio, 1982, a parasite of freshwater fish in Brazil), were found encapsulated in the hemocel of the Amazon river prawn Macrobrachium amazonicum (Heller) (Decapoda: Palaemonidae) from the natural canals on the Mexiana Island (Amazon River Delta), Pardá State, Brazil. The prevalence in prawns (body length 48-110 mm) examined in January and March 2008 (n = 44) was 32%, with an intensity of 1-6 (mean 2) larvae per crustacean. The nematode larvae (body length 19.7-25.7 mm), characterized by the cephalic end provided with a helmet-like cuticular structure having a thickened free posterior margin, are described based on light and scanning electron microscopy. Apparently prawns play a role as intermediate hosts for this nematode species. This is the first record of a larval representative of Cystidicolidae in South America and the first record of a species of Pseudoproleptus Khera, 1955, in the Neotropics. Heliconema izecksohni is transferred to Pseudoproleptus as Pseudoproleptus izecksohni (Fabio, 1982) n. comb. PMID:19014207

Moravec, Frantisek; Santos, Cláudia P

2009-06-01

2

Amazon River  

article title:  Mouth of the Amazon River     View Larger Image ... Flowing over 6450 kilometers eastward across Brazil, the Amazon River originates in the Peruvian Andes as tiny mountain streams that ...

2013-04-17

3

Amazon River  

... the Rio Solimoes and the Rio Negro converge to form the Amazon River. This image from the Multi-angle Imaging SpectroRadiometer (MISR) ... date:  Jul 23, 2000 Images:  Amazon River location:  South America thumbnail:  ...

2013-04-17

4

The Amazon, measuring a mighty river  

USGS Publications Warehouse

The Amazon, the world's largest river, discharges enough water into the sea each day to provide fresh water to the City of New York for over 9 years. Its flow accounts for about 15 percent of all the fresh water discharged into the oceans by all the rivers of the world. By comparison, the Amazon's flow is over 4 times that of the Congo River, the world's second largest river. And it is 10 times that of the Mississippi, the largest river on the North American Continent.

U.S. Geological Survey

1967-01-01

5

Amazon River Cycles Carbon Faster than Thought  

NSF Publications Database

... 05-126Amazon River Cycles Carbon Faster than Thought Carbon is Returned to Atmosphere in Five Short ... gas carbon dioxide far faster - than anyone realized. Most of the carbon being exhaled as carbon ...

6

Tectonics and paleogeography along the Amazon river  

Microsoft Academic Search

The main structural and geomorphological features along the Amazon River are closely associated with Mesozoic and Cenozoic tectonic events.The Mesozoic tectonic setting is characterised by the Amazonas and Marajó Basins, two distinct extensional segments. The Amazonas Basin is formed by NNE–SSW normal faults, which control the emplacement of dolerite dykes and deposition of the sedimentary pile. In the more intense

João Batista Sena Costa; Ruth Léa Bemerguy; Yociteru Hasui; Maur??cio da Silva Borges

2001-01-01

7

Biogeochemistry of carbon in the Amazon River  

Microsoft Academic Search

Depth-integrated, discharge-weighted water samples were collected over 1,800km ofthe Amazon River on eight cruises at different stages of the hydrograph, 1982-1984. Fine (FPOC, 163 pm) and coarse (CPOC, > 63 rm) particulate organic carbon as weight percentage of suspended sediment varied between 0.9-1.5% for FPOC and 0.5-3.49\\/o for CPOC. Concentrations of FPOC ranged from 5 mg liter-' upriver to 2

JEFFREY E. RICHEY; JOHN I. HEDGES; ALLAN H. DEVOL; PAUL D. QUAY; REYNALDO VICTORIA; LUIZ MARTINELLI; BRUCE R. FORSBERG

1990-01-01

8

Size distribution of Amazon River bed sediment  

USGS Publications Warehouse

The first recorded observations of bed material of the Amazon River were made in 1843 by Lt William Lewis Herndon of the US Navy, when he travelled the river from its headwaters to its mouth, sounding its depths, and noting the nature of particles caught in a heavy grease smeared to the bottom of his sounding weight1. He reported the bed material of the river to be mostly sand and fine gravel. Oltman and Ames took samples at a few locations in 1963 and 1964, and reported the bed material at O??bidos, Brazil, to be fine sands, with median diameters ranging from 0.15 to 0.25 mm (ref. 2). We present here a summary of particle-size analyses of samples of streambed material collected from the Amazon River and its major tributaries along a reach of the river from Iquitos in Peru, ???3,500 km above Macapa?? Brazil, to a point 220 km above Macapa??3. ?? 1980 Nature Publishing Group.

Nordin, C. F.; Meade, R. H.; Curtis, W. F.; Bosio, N. J.; Landim, P. M. B.

1980-01-01

9

Gene discovery from an ovary cDNA library of oriental river prawn Macrobrachium nipponense by ESTs annotation.  

PubMed

The oriental river prawn, Macrobrachium nipponense, is an important crustacean species in aquaculture. However, early gonad maturity is a ubiquitous problem which devalues the product quality. While husbandry and nutritional management have achieved little success in tackling this issue, a molecular approach may discover the genes involved in reproduction and development, which will provide the basic knowledge on reproductive control. In this study, a high-quality cDNA library of prawn was constructed from the ovary tissue. A total of 3294 successful sequencing reactions yielded 3256 expressed sequence tags (ESTs) longer than 100 bp. The cluster and assembly analyses yielded 1514 unique sequences including 414 contigs and 1168 singletons. About 719 (47.49%) unique sequences were identified as orthologs of genes from other organisms. By sequence comparability analysis, 28 important genes including cathepsin B, chromobox protein, Cdc2, cyclin B, DEAD box protein and ADF/cofilin protein were expressed. These genes may be involved in reproductive and developmental functions in prawn. Peritrophin consisting of cortical rods was also found in this species. The identification of these EST sequences in M. nipponense would improve our understanding on the genes that regulate reproduction and development in prawn species. This study also lays the groundwork for development of molecular markers related to ovary development in other prawn species. PMID:20403747

Wu, Ping; Qi, Dan; Chen, Liqiao; Zhang, Hao; Zhang, Xiaowei; Qin, Jian Guang; Hu, Songnian

2009-06-01

10

Chemical and physical denudation in the Amazon River Basin  

Microsoft Academic Search

We present major and trace element data on the suspended and dissolved phases of the Amazon River and its main tributaries. The Sr isotopic composition of the dissolved load is also reported. Special attention is paid to the abundances of REE and to their fractionation between the dissolved and suspended phase. The rivers of the Amazon Basin are among the

Jérôme Gaillardet; Bernard Dupre; Claude J. Allegre; Philippe Négrel

1997-01-01

11

Backwater effects in the Amazon River basin of Brazil  

Microsoft Academic Search

The Amazon River mainstem of Brazil is so regulated by differences in the timing of tributary inputs and by seasonal storage of water on floodplains that maximum discharges exceed minimum discharges by a factor of only 3. Large tributaries that drain the southern Amazon River basin reach their peak discharges two months earlier than does the mainstem. The resulting backwater

Robert H. Meade; José M. Rayol; Sylvio C. Da Conceicão; José R. G. Natividade

1991-01-01

12

Amazon River Discharge and Climate Variability: 1903 to 1985  

Microsoft Academic Search

Reconstruction of an 83-year record (1903 to 1985) of the discharge of the Amazon River shows that there has been no statistically significant change in discharge over the period of record and that the predominant interannual variability occurs on the 2- to 3-year time scale. Oscillations of river discharge predate significant human influences in the Amazon basin and reflect both

Jeffrey E. Richey; Carlos Nobre; Clara Deser

1989-01-01

13

Amazon River investigations, reconnaissance measurements of July 1963  

USGS Publications Warehouse

The first measurements of the flow of the Amazon River were made in July 1963 as a joint project of the University of Brazil, the Brazilian Navy, and the U.S. Geological Survey. The discharge of the Amazon River at Obidos was 7,640,000 cfs at an annual flood stage somewhat lower than the average. For comparison the maximum known discharge of the Mississippi River at Vicksburg is about 2,300,000 cfs. Dissolved-solids concentrations and sediment loads of the Amazon River and of several major tributaries were found to be low.

Oltman, Roy Edwin; Sternberg, H. O'R.; Ames, F. C.; Davis, L. C.

1964-01-01

14

Radium and barium in the Amazon River system  

SciTech Connect

Data for /sup 226/Ra and /sup 228/Ra in the Amazon River system show that the activity of each radium isotope is strongly correlated with barium concentrations. Two trends are apparent, one for rivers which drain shield areas and another for all other rivers. These data suggest that there has been extensive fractionation of U, Th, and Ba during weathering in the Amazon basin. The /sup 226/Ra data fit a flux model for the major ions indicating that /sup 226/Ra behaves conservatively along the main channel of the Amazon River.

Moore, W.S.; Edmond, J.M.

1984-03-20

15

Radium and barium in the Amazon River system  

Microsoft Academic Search

Data for ²²⁶Ra and ²²⁸Ra in the Amazon River system show that the activity of each radium isotope is strongly correlated with barium concentrations. Two trends are apparent, one for rivers which drain shield areas and another for all other rivers. These data suggest that there has been extensive fractionation of U, Th, and Ba during weathering in the Amazon

Willard S. Moore; John M. Edmond

1984-01-01

16

Life history traits of the Monsoon River prawn Macrobrachium malcolmsonii (Milne-Edwards, 1844) (Palaemonidae) in the Ganges (Padma) River, northwestern Bangladesh  

Microsoft Academic Search

The Monsoon River prawn, Macrobrachium malcolmsonii (Milne-Edwards, 1844), is one of the dominant benthic species in the Ganges River. Our study describes some biological parameters including sex ratio, length–frequency distributions (LFD), length–weight relationships (LWR), and relative-condition (Kn) factor of M. malcolmsonii in the lower part of the Ganges River, northwestern Bangladesh. A total of 502 specimens of the ranges 3.54–11.76?cm

Jun Ohtomi; Ahmed Jaman; Saleha Jasmine; Robert L. Vadas Jr

2012-01-01

17

Life history traits of the Monsoon River prawn Macrobrachium malcolmsonii (Milne-Edwards, 1844) (Palaemonidae) in the Ganges (Padma) River, northwestern Bangladesh  

Microsoft Academic Search

The Monsoon River prawn, Macrobrachium malcolmsonii (Milne-Edwards, 1844), is one of the dominant benthic species in the Ganges River. Our study describes some biological parameters including sex ratio, length–frequency distributions (LFD), length–weight relationships (LWR), and relative-condition (Kn) factor of M. malcolmsonii in the lower part of the Ganges River, northwestern Bangladesh. A total of 502 specimens of the ranges 3.54–11.76?cm

Jun Ohtomi; Ahmed Jaman; Saleha Jasmine; Robert L. Vadas Jr

2011-01-01

18

Coagulation and settling of Amazon River suspended sediment  

Microsoft Academic Search

Sampling of the water column on the Amazon continental shelf was conducted in June July 1983, and shipboard measurements of the particle size distribution were accomplished utilizing techniques that permit measurement of flocs. These data indicated a volumetric concentration maximum about 100 km offshore from the Amazon River mouth, with maxima of the mean particle size in suspension in the

Ronald J. Gibbs; Lohit Konwar

1986-01-01

19

River dynamics and the diversity of Amazon lowland forest  

Microsoft Academic Search

We suggest here that large-scale natural forest disturbance and primary succession in the lowland rainforests of the Peruvian Amazon is caused by lateral erosion and channel changes of meandering rivers. Our results indicate that in the upper Amazon region, primary succession on newly deposited riverine soils is a major mode of forest regeneration. Landsat imagery analyses show that 26.6% of

Jukka Salo; Risto Kalliola; Ilmari Häkkinen; Yrjö Mäkinen; Pekka Niemelä; Maarit Puhakka; Phyllis D. Coley

1986-01-01

20

Major Element Geochemistry of the Amazon River System.  

National Technical Information Service (NTIS)

Samples of surface waters and precipitation were collected on the Amazon main channel, its major tributaries, and headwater rivers in the Peruvian and Bolivian Andes. Collection was done between 1976 and 1978. The bulk of the samples were obtained during ...

R. F. Stallard

1980-01-01

21

Backwater effects in the Amazon River basin of Brazil  

USGS Publications Warehouse

The Amazon River mainstem of Brazil is so regulated by differences in the timing of tributary inputs and by seasonal storage of water on floodplains that maximum discharges exceed minimum discharges by a factor of only 3. Large tributaries that drain the southern Amazon River basin reach their peak discharges two months earlier than does the mainstem. The resulting backwater in the lowermost 800 km of two large southern tributaries, the Madeira and Puru??s rivers, causes falling river stages to be as much as 2-3 m higher than rising stages at any given discharge. Large tributaries that drain the northernmost Amazon River basin reach their annual minimum discharges three to four months later than does the mainstem. In the lowermost 300-400 km of the Negro River, the largest northern tributary and the fifth largest river in the world, the lowest stages of the year correspond to those of the Amazon River mainstem rather than to those in the upstream reaches of the Negro River. ?? 1991 Springer-Verlag New York Inc.

Meade, R. H.; Rayol, J. M.; Da, Conceicao, S. C.; Natividade, J. R. G.

1991-01-01

22

Backwater effects in the Amazon River basin of Brazil  

NASA Astrophysics Data System (ADS)

The Amazon River mainstem of Brazil is so regulated by differences in the timing of tributary inputs and by seasonal storage of water on floodplains that maximum discharges exceed minimum discharges by a factor of only 3. Large tributaries that drain the southern Amazon River basin reach their peak discharges two months earlier than does the mainstem. The resulting backwater in the lowermost 800 km of two large southern tributaries, the Madeira and Purús rivers, causes falling river stages to be as much as 2 3 m higher than rising stages at any given discharge. Large tributaries that drain the northernmost Amazon River basin reach their annual minimum discharges three to four months later than does the mainstem. In the lowermost 300 400 km of the Negro River, the largest northern tributary and the fifth largest river in the world, the lowest stages of the year correspond to those of the Amazon River mainstem rather than to those in the upstream reaches of the Negro River.

Meade, Robert H.; Rayol, José M.; da Conceicão, Sylvio C.; Natividade, José R. G.

1991-09-01

23

Hydrodynamic modelling of the Amazon River: Factors of uncertainty  

NASA Astrophysics Data System (ADS)

Hydrodynamic modelling of Amazonian rivers is still a difficult task. Access difficulties reduce the possibilities to acquire sufficient good data for the model calibration and validation. Current satellite radar technology allows measuring the altitude of water levels throughout the Amazon basin. In this study, we explore the potential usefulness of these data for hydrodynamic modelling of the Amazon and Napo Rivers in Peru. Simulations with a 1-D hydrodynamic model show that radar altimetry can constrain properly the calibration and the validation of the model if the river width is larger than 2500 m. However, sensitivity test of the model show that information about geometry of the river channel and about the water velocity are more relevant for hydrodynamic modelling. These two types of data that are still not easily available in the Amazon context.

Chávarri, Eduardo; Crave, Alain; Bonnet, Marie-Paule; Mejía, Abel; Santos Da Silva, Joecila; Guyot, Jean Loup

2013-07-01

24

Biological Uptake of Dissolved Silica in the Amazon River Estuary  

Microsoft Academic Search

Approximately 25 percent of the dissolved silica carried by the Amazon River is depleted through diatom production in the inner estuary. Annual production of opaline frustules is estimated to be 15 million tons. However, few diatoms accumulate in modern shelf sediments and chemical recycling appears to be slight. Instead, many frustules apparently are transported landward into the river system, where

John D. Milliman; Edward Boyle

1975-01-01

25

Seasonal sediment storage on mudflats adjacent to the Amazon River  

Microsoft Academic Search

210Pb and 234Th activity profiles in sediment cores from underconsolidated mudflats 300 km downdrift of the Amazon river mouth record an ephemeral surface layer of fine-grained sediment up to 1.5 m thick. This layer contains about l.5 × 108 tons of Amazon sediment deposited rapidly (~1 cm\\/d) from a fluid-mud suspension (10–400 g\\/l) during the months between January and June.

M. A. Allison; C. A. Nittrouer; G. C. Kineke

1995-01-01

26

Mouths of the Amazon River, Brazil, South America  

NASA Technical Reports Server (NTRS)

Huge sediment loads from the interior of the country flow through the Mouths of the Amazon River, Brazil (0.5S, 50.0W). The river current carries hundreds of tons of sediment through the multiple outlets of the great river over 100 miles from shore before it is carried northward by oceanic currents. The characteristic 'fair weather cumulus' pattern of low clouds over the land but not over water may be observed in this scene.

1991-01-01

27

Rates and mechanisms of shoreface progradation and retreat downdrift of the Amazon river mouth  

Microsoft Academic Search

Field surveys of the 350-km shoreline adjacent to the Amazon river mouth reveal three distinct types: erosional mud, accretionary sand, and accretionary mud. Formation of these zones is controlled by the delivery of Amazon suspended sediment, mediated by the hydrodynamic regime. Erosional mud shorelines extend from Rio Araguari (near the Amazon river mouth) northwestward 280 km to 3.5 °N (near

M. A. Allison; C. A. Nittrouer; L. E. C. Faria

1995-01-01

28

Mercury in the Tapajós River basin, Brazilian Amazon: A review  

Microsoft Academic Search

This paper presents a review about mercury contamination and human exposure in the Tapajós River basin (Brazil), one of the major tributaries of the Amazon impacted by traditional gold mining from the mid 1980s. The most recent review in this region was published more than ten years ago and since then many articles about environment and especially human populations have

J. J. Berzas Nevado; R. C. Rodríguez Martín-Doimeadios; F. J. Guzmán Bernardo; M. Jiménez Moreno; A. M. Herculano; J. L. M. do Nascimento; M. E. Crespo-López

2010-01-01

29

Organic carbon-14 in the Amazon River system  

SciTech Connect

Coarse and fine suspended particulate organic materials and dissolved humic and fulvic acids transported by the Amazon River all contain bomb-produced carbon-14, indicating relatively rapid turnover of the parent carbon pools. However, the carbon-14 contents of these coexisting carbon forms are measurably different and may reflect varying degrees of retention by soils in the drainage basin. 20 references, 1 table.

Hedges, J.I.; Ertel, J.R.; Quay, P.D.; Grootes, P.M.; Richey, J.E.; Devol, A.H.; Farwell, G.W.; Schmidt, F.W.; Salati, E.

1986-03-07

30

Dissolved humic substances of the Amazon River system1  

Microsoft Academic Search

Aquatic humic and fulvic acids from nine mainstem and seven major tributary sites in the Amazon River Basin are characterized by their elemental and lignin phenol compositions. Com- bined humic substances represent 60% of the riverine dissolved organic carbon (DOC), with fulvic to humic acid (FA : HA) ratios in the mainstem averaging 4.7 -t 1 .O. All dissolved humic

John R. Ertel; John I. Hedges; Allan H. Devol; Jefrey E. Richey

1986-01-01

31

Organic carbon-14 in the Amazon River system  

Microsoft Academic Search

Coarse and fine suspended particulate organic materials and dissolved humic and fulvic acids transported by the Amazon River all contain bomb-produced carbon-14, indicating relatively rapid turnover of the parent carbon pools. However, the carbon-14 contents of these coexisting carbon forms are measurably different and may reflect varying degrees of retention by soils in the drainage basin. 20 references, 1 table.

J. I. Hedges; J. R. Ertel; P. D. Quay; P. M. Grootes; J. E. Richey; A. H. Devol; G. W. Farwell; F. W. Schmidt; E. Salati

1986-01-01

32

Suspended sediment dynamics in the Amazon River of Peru  

NASA Astrophysics Data System (ADS)

The erosion and transport of sediments allow us to understand many activities of significance, such as crust evolution, climate change, uplift rates, continental processes, the biogeochemical cycling of pollutants and nutrients. The Amazon basin of Peru has contrasting physiographic and climatic characteristics between the Andean piedmont and the plains and between the north and south of the basin which is why there are 8 gauging stations located along the principal rivers of the Andean piedmont (Marañón, Huallaga, Ucayali) and the plain (Marañón, Tigre, Napo, Ucayali and Amazon rivers). Since 2003, the ORE-Hybam (IRD-SENAMHI-UNALM) observatory has performed out regular measurements at strategic points of the Amazon basin to understand and model the systems, behavior and long-term dynamics. On the Andean piedmont, the suspended yields are governed by a simple model with a relationship between the river discharge and the sediment concentration. In the plain, the dilution effect of the concentrations can create hysteresis in this relationship on a monthly basis. The Amazon basin of Peru has a sediment yield of 541 *106 t year-1, 70% comes from the southern basin.

Armijos, Elisa; Crave, Alain; Vauchel, Philippe; Fraizy, Pascal; Santini, William; Moquet, Jean-Sèbastien; Arevalo, Nore; Carranza, Jorge; Guyot, Jean-Loup

2013-07-01

33

Genetic diversity analysis of oriental river prawn, Macrobrachium nipponense, in Yellow River using microsatellite marker.  

PubMed

To assess the genetic status of this species, the genetic diversity of wild Macrobrachium nipponense from seven geographic locations in the Yellow River basin were investigated using 20 polymorphic microsatellite DNA loci. The genetic diversity between populations was indicated by the mean number of alleles per locus and mean observed heterozygosity (H) and the expected H, which was arranged from 2 to 10, from 0.4705 to 0.5731, and from 0.5174 to 0.6146, respectively. Hardy-Weinberg equilibrium analysis indicated that a deficiency of heterozygotes existed in all seven populations. Both the F(ST) and AMOVA analyses showed that there is significant difference on population differentiation among populations. The UPGMA clustering tree demonstrated that their close relationship is consistent with their geographic proximity. The data suggest that this Yellow River population has a wide genetic base that is suitable for breeding. PMID:24301938

Qiao, H; Lv, D; Jiang, S F; Sun, S M; Gong, Y S; Xiong, Y W; Jin, S B; Fu, H T

2013-01-01

34

Bacterial carbon metabolism in the Amazon River system  

Microsoft Academic Search

Bacterial abundance and production and community respiration were measured at several mainstem and tributary stations in November-December 1988, April-May 1990, and August-September 199 1 in a 1,950- km reach of the Amazon River between Vargem Grande and Obidos, Brazil. Bacterial abundances averaged 1.1 x 1 O9 cells liter - L in the mainstem during the three cruises, and rates of

RONALD BENNER; STEPHEN OPSAHL; GERARDO CHIN-LEO; JEFFREY E. RICHEY; BRUCE R. FORSBERG

1995-01-01

35

Prawn Park - Taupo, New Zealand  

SciTech Connect

A freshwater prawn farm enterprise was established in 1987 in New Zealand to make use of geothermal waste heat from the Wairakei power generating field on the North Island. Approximately 2200 tons of prawns are imported each year into New Zealand, therefore, an effort was initiated to try and capture some of this market with a domestic product. Presently, there are 19 ponds varying in size from 0.2 to 0.35 ha (0.5 to 0.9 acres) with an average temperature of 24{degrees}C. The water comes from two different sources: river water and heated water from the plate heat exchanger. The farm is presently capable of producing up to 30 tonnes (33 tons) of prawns per annum of prawns, with plans for expansion of the operation in the near future.

Lund, J.W.; Klein, R. [Prawn Park, Taupo (New Zealand)

1995-10-01

36

Suspended sediments of the modern Amazon and Orinoco rivers  

USGS Publications Warehouse

The Amazon and Orinoco Rivers are massive transcontinental conveyance systems for suspended sediment. They derive about 90% of their sediment from the Andes that support their western headwaters, transport it for thousands of kilometers across the breadth of the continent and deposit it in the coastal zones of the Atlantic. At their points of maximum suspended-sediment discharge, the Amazon transports an average of 1100-1300 ?? 106 tons per year and the Orinoco transports about 150 ?? 106 tons per year. Relations of sediment discharge to water discharge are complicated by unusual patterns of seasonal storage and remobilization, increased storage and reduced transport of sediment in the middle Orinoco during periods of peak water discharge, and storage of suspended sediment in the lower Amazon during rising discharge and resuspension during falling discharge. Spatial distributions of suspended sediment in cross-sections of both rivers are typically heterogeneous, not only in the vertical sense but also in the lateral. The cross-channel mixing of tributary inputs into the mainstem waters is a slow process that requires several hundred kilometers of downriver transport to complete. Considerable fine-grained sediment is exchanged between rivers and floodplains by the combination of overbank deposition and bank erosion. ?? 1994.

Meade, R. H.

1994-01-01

37

Phytoplankton biomass and productivity in the Amazon River plume: correlation with seasonal river discharge  

Microsoft Academic Search

Phytoplankton biomass and primary productivity were assessed on the continental shelf in the plume of the Amazon River during a series of cruises conducted within periods of minimum, maximum, rising and falling river discharge. Chlorophyll concentrations were greatest (up to 25.5 ?g l?1) in a zone located outside the turbid, high nutrient, low salinity riverine waters but shoreward of the

Walker O. Smith; David J. Demaster

1996-01-01

38

The history of the introduction of the giant river prawn, Macrobrachium cf. rosenbergii (Decapoda, Palaemonidae), in Brazil: New insights from molecular data  

PubMed Central

The giant river prawn, Macrobrachium cf. rosenbergii, is one of the most cultivated freshwater prawns in the world and has been introduced into more than 40 countries. In some countries, this prawn is considered an invasive species that requires close monitoring. Recent changes in the taxonomy of this species (separation of M. rosenbergii and M. dacqueti) require a re-evaluation of introduced taxa. In this work, molecular analyses were used to determine which of these two species was introduced into Brazil and to establish the geographic origin of the introduced populations that have invaded Amazonian coastal waters. The species introduced into Brazil was M. dacqueti through two introduction events involving prawns originating from Vietnam and either Bangladesh or Thailand. These origins differ from historical reports of the introductions and underline the need to confirm the origin of other exotic populations around the world. The invading populations in Amazonia require monitoring not only because the biodiversity of this region may be affected by the introduction, but also because admixture of different native haplotypes can increase the genetic variability and the likelihood of persistence of the invading species in new habitats.

Iketani, Gabriel; Pimentel, Luciana; Silva-Oliveira, Glaucia; Maciel, Cristiana; Valenti, Wagner; Schneider, Horacio; Sampaio, Iracilda

2011-01-01

39

Climatic variability between SST and river discharge at Amazon region  

NASA Astrophysics Data System (ADS)

Climatic variability, related both to precipitation and river discharge, has been associated to ocean variability. Authors commonly relate Pacific sea surface temperature (SST) variation to South America (SA) precipitation. Zonal displacement of Walker cell, with intensified subsidence over northern portion of SA, Subtropical Jet strengthening/weakening over extratropical latitudes of SA are, respectively, dynamical reasons scientifically accepted for increasing and depletion of precipitation at the respective areas. Many studies point out the influence of tropical Atlantic SST anomalies in relation to precipitation/river discharge variability over northeast of Brazil. Aliseos variability at tropical Atlantic is also a physic process that contributes to explain precipitation and river flow variability over SA, mainly over the north portion. In this study, we aim to investigate the temporal correlation between SST, mainly from Pacific and Atlantic oceans, and rivers discharge at the Amazon region. Ji-Parana, Madeira and Tapajós river discharge in monthly and annual scale, between 1968 and 2008, were the time series selected to reach the purpose. Time series for river discharge were obtained from Agência Nacional de Águas (ANA, in Portuguese) and, SST data were obtained from CDC/NOAA. Before linear correlation computations between river discharge and SST have been made, seasonal cycle and linear tendency were removed from all original time series. Areas better correlated to river discharge at Amazon region show oceanic patterns apparently associated to PDO (Pacific Decadal Oscillation) and ENSO (El Niño-South Oscillation) variability, with absolute values greater than 0.3 and reaching 0.5 or 0.6. The spatial pattern observed at Pacific basin is similar to that showed by the first mode of PCA (Principal Component Analysis), such seen in many studies (the "horse shoe" pattern). In general, negative correlation values appear far more to the west of Pacific basin while positive values are appear over areas a bit more to east. Central and east areas over Equatorial Pacific show negative values to the discharge series analyzed. ENSO events are well correlated to precipitation anomalies over Amazon region. Positive/negative SST anomalies over central-east Equatorial Pacific are associated to few/more precipitation/river discharge over Amazon region. Madeira discharge is especially well and negatively correlated to SST at tropical North Atlantic areas, showing absolute values greater than 0.5. In this case, the increase/decrease of river discharge over Amazon region when SST anomaly at the tropical north Atlantic is negative/positive can be explained by the strengthened/weakened winds over the equatorial side of the subtropical high during these situations. Pacific and Atlantic areas that show good correlations to river discharge at Amazon region may be potential variables in a linear model to simulation and prediction of discharge.

Silva, M. E.; Silva, E. R. L.

2012-04-01

40

The Amazon continuum dataset: quantitative metagenomic and metatranscriptomic inventories of the Amazon River plume, June 2010  

PubMed Central

Background The Amazon River is by far the world’s largest in terms of volume and area, generating a fluvial export that accounts for about a fifth of riverine input into the world’s oceans. Marine microbial communities of the Western Tropical North Atlantic Ocean are strongly affected by the terrestrial materials carried by the Amazon plume, including dissolved (DOC) and particulate organic carbon (POC) and inorganic nutrients, with impacts on primary productivity and carbon sequestration. Results We inventoried genes and transcripts at six stations in the Amazon River plume during June 2010. At each station, internal standard-spiked metagenomes, non-selective metatranscriptomes, and poly(A)-selective metatranscriptomes were obtained in duplicate for two discrete size fractions (0.2 to 2.0 ?m and 2.0 to 156 ?m) using 150 × 150 paired-end Illumina sequencing. Following quality control, the dataset contained 360 million reads of approximately 200 bp average size from Bacteria, Archaea, Eukarya, and viruses. Bacterial metagenomes and metatranscriptomes were dominated by Synechococcus, Prochlorococcus, SAR11, SAR116, and SAR86, with high contributions from SAR324 and Verrucomicrobia at some stations. Diatoms, green picophytoplankton, dinoflagellates, haptophytes, and copepods dominated the eukaryotic genes and transcripts. Gene expression ratios differed by station, size fraction, and microbial group, with transcription levels varying over three orders of magnitude across taxa and environments. Conclusions This first comprehensive inventory of microbial genes and transcripts, benchmarked with internal standards for full quantitation, is generating novel insights into biogeochemical processes of the Amazon plume and improving prediction of climate change impacts on the marine biosphere.

2014-01-01

41

Transcriptome Analysis of the Oriental River Prawn, Macrobrachium nipponense Using 454 Pyrosequencing for Discovery of Genes and Markers  

PubMed Central

Background The oriental river prawn, Macrobrachium nipponense, is an economically and nutritionally important species of the Palaemonidae family of decapod crustaceans. To date, the sequencing of its whole genome is unavailable as a non-model organism. Transcriptomic information is also scarce for this species. In this study, we performed de novo transcriptome sequencing to produce the first comprehensive expressed sequence tag (EST) dataset for M. nipponense using high-throughput sequencing technologies. Methodology and Principal Findings Total RNA was isolated from eyestalk, gill, heart, ovary, testis, hepatopancreas, muscle, and embryos at the cleavage, gastrula, nauplius and zoea stages. Equal quantities of RNA from each tissue and stage were pooled to construct a cDNA library. Using 454 pyrosequencing technology, we generated a total of 984,204 high quality reads (338.59Mb) with an average length of 344 bp. Clustering and assembly of these reads produced a non-redundant set of 81,411 unique sequences, comprising 42,551 contigs and 38,860 singletons. All of the unique sequences were involved in the molecular function (30,425), cellular component (44,112) and biological process (67,679) categories by GO analysis. Potential genes and their functions were predicted by KEGG pathway mapping and COG analysis. Based on our sequence analysis and published literature, many putative genes involved in sex determination, including DMRT1, FTZ-F1, FOXL2, FEM1 and other potentially important candidate genes, were identified for the first time in this prawn. Furthermore, 6,689 SSRs and 18,107 high-confidence SNPs were identified in this EST dataset. Conclusions The transcriptome provides an invaluable new data for a functional genomics resource and future biological research in M. nipponense. The molecular markers identified in this study will provide a material basis for future genetic linkage and quantitative trait loci analyses, and will be essential for accelerating aquaculture breeding programs with this species.

Ma, Keyi; Qiu, Gaofeng; Feng, Jianbin; Li, Jiale

2012-01-01

42

Molecular cloning and characterization of the lipopolysaccharide and ?-1,3-glucan binding protein from oriental river prawn, Macrobrachium nipponense.  

PubMed

The lipopolysaccharide and ?-1,3-glucan binding protein (LGBP), one of the pattern recognition proteins, plays an important role in the innate immune response of invertebrates. A 1,506 bp full-length cDNA of a LGBP gene was cloned and characterized from the oriental river prawn Macrobrachium nipponense (named as MnLGBP). Analysis of the nucleotide sequence revealed that the cDNA clone has an open reading frame of 1,119 bp, encoding a protein of 372 amino acids including a 21-aa signal peptide. The calculated molecular mass of the mature protein (351 aa) was 39.9 kDa with an estimated pI of 4.63. The MnLGBP sequence contains: (1) two putative integrin-binding motifs, (2) a glucanase motif, (3) two putative N-glycosylation sites, (4) one protein kinase C phosphorylation site, and (5) a putative recognition motif for ?-1,3-linkage of polysaccharides. Sequence comparison based on the deduced amino acid sequence of MnLGBP showed varied identity of 89, 76 and 74 % with those of Macrobrachium rosenbergii LGBP, Marsupenaeus japonicus ?-1,3-glucan binding proteins, and Fenneropenaeus chinensis LGBP, respectively. Quantitative RT-PCR results showed that MnLGBP was expressed in nerve, intestine, muscle, gill, heart, haemocytes and at the highest level in hepatopancreas. After challenge with the pathogen, Aeromonas hydrophila and Vibrio parahaemolyticus, the expression of MnLGBP mRNA was significantly upregulated in the hepatopancreas compared to the control group. At the same time, the mRNA level of MnproPO increased dramatically at 48 h after injection of bacteria. These data should be helpful to better understand the function of MnLGBP in the prawn immune system. PMID:24584659

Xiu, Yunji; Wu, Ting; Liu, Peng; Huang, Ying; Ren, Qian; Gu, Wei; Meng, Qingguo; Wang, Wen

2014-06-01

43

Daily water level by ENVISAT altimetry of the Amazon River  

NASA Astrophysics Data System (ADS)

Radar Altimetry is a remote sensing technique applied in order to obtain the level of water of the hydrological processes, mostly in remote regions such as in the Amazon basin. However, the altimetry satellites have a limitation in their temporal resolution, which in the case of ENVISAT is 35 days, which prevents the study of short-term hydrological events alert of floods and droughts and etc. Thus, a method of obtaining altimetric daily time series water level, based on a linear model of interpolation by optimization with multi-objective criteria was applied, using data from in situ on pluvial stations, along the Amazon River. The altimetry data validation show accurate results with a RMS of 11 cm, while the estimates carried out by the model obtained 63% of altimetric daily time series water level data with RMS less than 40 cm, thus allowing the use of altimetry data daily at various hydrological studies, hydrodynamic modeling and monitoring of extreme events.

Sousa, A. C.; Pereira, P.; Silva, J. S.; Calmant, S.; Seyler, F.

2013-05-01

44

Iron cycling in the Amazon River Basin: the isotopic perspective  

NASA Astrophysics Data System (ADS)

With the global climate change and increasing anthropic pressure on nature, it is important to find new indicators of the response of complex systems like the Amazon River Basin. In particular, new tracers like iron isotopes may tell us much on processes such as the chemical exchanges between rivers, soils and the biosphere. Pioneering studies revealed that for some river waters, large ?57Fe fractionations are observed between the suspended and dissolved load (Bergquist and Boyle, 2006), and isotopic variations were also recognized on the suspended matter along the hydrological cycle (Ingri et al., 2006). On land, soil studies from various locations have shown that ?57Fe signatures depend mostly on the weathering regime (Fantle and DePaolo, 2004; Emmanuel et al., 2005; Wiederhold et al., 2007; Poitrasson et al., 2008). It thus seems that Fe isotopes could become an interesting new tracer of the exchanges between soils, rivers and the biosphere. We therefore conducted Fe isotope surveys through multidisciplinary field missions on rivers from the Amazon Basin. It was confirmed that acidic, organic-rich black waters show strong Fe isotope fractionation between particulate and dissolved loads. Furthermore, this isotopic fractionation varies along the hydrological cycle, like previously uncovered in boreal waters suspended matter. In contrast, unfiltered waters show very little variation with time. It was also found that Fe isotopes remain a conservative tracer even in the case of massive iron loss during the mixing of chemically contrasted waters such as the Negro and Solimões tributaries of the Amazon River. Given that >95% of the Fe from the Amazon River is carried as detrital materials, our results lead to the conclusion that the Fe isotope signature delivered to the Atlantic Ocean is undistinguishable from the continental crust value, in contrast to previous inferences. The results indicate that Fe isotopes in rivers represent a promising indicator of the interaction between organic matter and iron in rivers, and ultimately the nature of their source in soils. As such, they may become a powerfull tracer of changes occurring on the continents in response to both weathering context and human activities. References: Bergquist, B.A., Boyle, E.A., 2006. Iron isotopes in the Amazon River system: Weathering and transport signatures. Earth and Planetary Science Letters, 248: 54-68. Emmanuel, S., Erel, Y., Matthews, A., Teutsch, N., 2005. A preliminary mixing model for Fe isotopes in soils. Chemical Geology, 222: 23-34. Fantle, M.S., DePaolo, D.J., 2004. Iron isotopic fractionation during continental weathering. Earth and Planetary Science Letters, 228: 547-562. Ingri, J., Malinovsky, D., Rodushkin, I., Baxter, D.C., Widerlund, A., Andersson, P., Gustafsson, O., Forsling, W., Ohlander, B., 2006. Iron isotope fractionation in river colloidal matter. Earth and Planetary Science Letters, 245: 792-798. Poitrasson, F., Viers, J., Martin, F., Braun, J.J., 2008. Limited iron isotope variations in recent lateritic soils from Nsimi, Cameroon: Implications for the global Fe geochemical cycle. Chemical Geology, 253: 54-63. Wiederhold, J.G., Teutsch, N., Kraemer, S.M., Halliday, A.N., Kretzchmar, R., 2007. Iron isotope fractionation in oxic soils by mineral weathering and podzolization. Geochimica et Cosmochimica Acta, 71: 5821-5833.

Poitrasson, Franck; Vieira, Lucieth; Mulholland, Daniel; Seyler, Patrick; Sondag, Francis; Allard, Thierry

2014-05-01

45

Photochemical and microbial consumption of dissolved organic carbon and dissolved oxygen in the Amazon River system  

Microsoft Academic Search

Bacterial and photochemical mineralization of dissolved organic matter were investigated in the Amazon River system. Dissolved oxygen, dissolved organic carbon (DOC), and bacterial growth were measured during incubations conducted under natural sunlight and in the dark. Substrate addition experiments indicated that the relatively low rates of bacterial activity in Amazon River water were caused by C limitation. Experiments to determine

R. M. W. Amon; R. Benner

1996-01-01

46

Amazon River carbon dioxide outgassing fuelled by wetlands  

NASA Astrophysics Data System (ADS)

River systems connect the terrestrial biosphere, the atmosphere and the ocean in the global carbon cycle. A recent estimate suggests that up to 3 petagrams of carbon per year could be emitted as carbon dioxide (CO2) from global inland waters, offsetting the carbon uptake by terrestrial ecosystems. It is generally assumed that inland waters emit carbon that has been previously fixed upstream by land plant photosynthesis, then transferred to soils, and subsequently transported downstream in run-off. But at the scale of entire drainage basins, the lateral carbon fluxes carried by small rivers upstream do not account for all of the CO2 emitted from inundated areas downstream. Three-quarters of the world's flooded land consists of temporary wetlands, but the contribution of these productive ecosystems to the inland water carbon budget has been largely overlooked. Here we show that wetlands pump large amounts of atmospheric CO2 into river waters in the floodplains of the central Amazon. Flooded forests and floating vegetation export large amounts of carbon to river waters and the dissolved CO2 can be transported dozens to hundreds of kilometres downstream before being emitted. We estimate that Amazonian wetlands export half of their gross primary production to river waters as dissolved CO2 and organic carbon, compared with only a few per cent of gross primary production exported in upland (not flooded) ecosystems. Moreover, we suggest that wetland carbon export is potentially large enough to account for at least the 0.21 petagrams of carbon emitted per year as CO2 from the central Amazon River and its floodplains. Global carbon budgets should explicitly address temporary or vegetated flooded areas, because these ecosystems combine high aerial primary production with large, fast carbon export, potentially supporting a substantial fraction of CO2 evasion from inland waters.

Abril, Gwenaël; Martinez, Jean-Michel; Artigas, L. Felipe; Moreira-Turcq, Patricia; Benedetti, Marc F.; Vidal, Luciana; Meziane, Tarik; Kim, Jung-Hyun; Bernardes, Marcelo C.; Savoye, Nicolas; Deborde, Jonathan; Souza, Edivaldo Lima; Albéric, Patrick; Landim de Souza, Marcelo F.; Roland, Fabio

2014-01-01

47

Amazon River carbon dioxide outgassing fuelled by wetlands.  

PubMed

River systems connect the terrestrial biosphere, the atmosphere and the ocean in the global carbon cycle. A recent estimate suggests that up to 3 petagrams of carbon per year could be emitted as carbon dioxide (CO2) from global inland waters, offsetting the carbon uptake by terrestrial ecosystems. It is generally assumed that inland waters emit carbon that has been previously fixed upstream by land plant photosynthesis, then transferred to soils, and subsequently transported downstream in run-off. But at the scale of entire drainage basins, the lateral carbon fluxes carried by small rivers upstream do not account for all of the CO2 emitted from inundated areas downstream. Three-quarters of the world's flooded land consists of temporary wetlands, but the contribution of these productive ecosystems to the inland water carbon budget has been largely overlooked. Here we show that wetlands pump large amounts of atmospheric CO2 into river waters in the floodplains of the central Amazon. Flooded forests and floating vegetation export large amounts of carbon to river waters and the dissolved CO2 can be transported dozens to hundreds of kilometres downstream before being emitted. We estimate that Amazonian wetlands export half of their gross primary production to river waters as dissolved CO2 and organic carbon, compared with only a few per cent of gross primary production exported in upland (not flooded) ecosystems. Moreover, we suggest that wetland carbon export is potentially large enough to account for at least the 0.21 petagrams of carbon emitted per year as CO2 from the central Amazon River and its floodplains. Global carbon budgets should explicitly address temporary or vegetated flooded areas, because these ecosystems combine high aerial primary production with large, fast carbon export, potentially supporting a substantial fraction of CO2 evasion from inland waters. PMID:24336199

Abril, Gwenaël; Martinez, Jean-Michel; Artigas, L Felipe; Moreira-Turcq, Patricia; Benedetti, Marc F; Vidal, Luciana; Meziane, Tarik; Kim, Jung-Hyun; Bernardes, Marcelo C; Savoye, Nicolas; Deborde, Jonathan; Souza, Edivaldo Lima; Albéric, Patrick; Landim de Souza, Marcelo F; Roland, Fabio

2014-01-16

48

Trace elements and radionuclides in the Connecticut River and Amazon River estuary  

SciTech Connect

The Connecticut River, its estuary and the Amazon River plume were studied to elucidate processes which control the flux of nuclides to the sea. Major ions (Ca, Mg, Na, Cl, Bicarbonate) and selected trace elements (Ra, Ba, Cu, Si) are introduced to the Connecticut River in proportion to the total dissolved load of various groundwaters. Si, Ra, and Ba are subject to removal from solution by seasonal diatom productivity; whereas the other groundwater-derived elements are found in proportion to TDS both time and space. These nuclides are released in the estuary when a portion of the Ra, Ba, and Si in riverine biogenic detritus is trapped in salt marshes and coves bordering the estuary where it redissolves and is exported to the main river channel at ebb tide. In the Amazon River estuary, the Ra and Ba are released in mid-salinity waters. Ra and Ba together with Si are subsequently removed by diatom productivity as reflected in increased Ra and Ba in the suspended particles and depleted dissolved nuclide concentrations in samples from the high productivity zone. In both the Connecticut River system and the Amazon River plume, Cu behaves conservatively; whereas the fates of Fe and Al are linked to soil-derived humic acids. Trace elements in Amazon plume sediments are found simply in proportion to the percentage of fine-grained size materials, despite low Th-228/Ra-228 mean residence times in the plume and the presence of Cs-137 in the sediment column. Estimates of the total flux of nuclides to the oceans can best be calculated on a mass balance basis using groundwater inputs. Unless significant repositories for nuclides exist in the river-estuarine system, the groundwater flux of dissolved nuclides is net flux to the ocean despite the reactions which occur in both rivers and estuaries.

Dion, E.P.

1983-01-01

49

Dietary Studies on the Predatory Fishes of the Norman River Estuary, with Particular Reference to Penaeid Prawns  

NASA Astrophysics Data System (ADS)

The predatory fish community and their prey in the Norman Rivere estuary, Gulf of Carpentaria Australia, are compared with the communities of other tropical inshore areas, to investigate patterns of predation in tropical inshore areas particularly in relation to penaeid prawns. Abiotic factors (turbidity, freshwater input) and diversity of habitat types affect the composition of both prey and predator communities, resulting in large differences in the communities of tropical inshore waters. The stomach contents of 2059 predatory fish from the Norman River estuary were analysed over four sampling trips in the wet and dry seasons. The stomachs of 61% (1255 fish) of 54 species contained a total of 676·2 g (dry weight) of food, while 39% (804 fish) were empty. Teleosts were the main component of the diet (by dry weight) of 13 of the 22 species analysed, followed by annelids for two species. Five species had only teleosts in their stomachs. Most predator species ate benthic or bentho-pelagic prey, while three species— Rhizoprionodon taylori, Scomberoides commersonianusand Leptobrama mulleri—ate mainly pelagic prey. Although 19 species ate some penaeids, only Polydactylus sheridaniate little else. This species, Lates calcariferand Eleutheronema tetradactylumate 94·5% of all the penaeid prey and 97·9% of all the commercially important penaeid prey recorded in the study. Penaeid predation indices (calculated from gillnet catch rates, proportion of penaeids in the diet and a consumption rate of 3% body weight per day) were 0·23 g of penaeid per net-metre per day for P. sheridani, 0·15 for L. calcariferand 0·03 for E. tetradactylum. Commercially important penaeid predation indices were 0·11, 0·13 and 0·01, respectively. These values are intermediate between those previously recorded for the main penaeid predators in other inshore areas of the Gulf of Carpentaria (Embley River estuary and Groote Eylandt).

Salini, J. P.; Brewer, D. T.; Blaber, S. J. M.

1998-06-01

50

Microspatial gene expression patterns in the Amazon River Plume.  

PubMed

We investigated expression of genes mediating elemental cycling at the microspatial scale in the ocean's largest river plume using, to our knowledge, the first fully quantitative inventory of genes and transcripts. The bacterial and archaeal communities associated with a phytoplankton bloom in Amazon River Plume waters at the outer continental shelf in June 2010 harbored ?1.0 × 10(13) genes and 4.7 × 10(11) transcripts per liter that mapped to several thousand microbial genomes. Genomes from free-living cells were more abundant than those from particle-associated cells, and they generated more transcripts per liter for carbon fixation, heterotrophy, nitrogen and phosphorus uptake, and iron acquisition, although they had lower expression ratios (transcripts?gene(-1)) overall. Genomes from particle-associated cells contributed more transcripts for sulfur cycling, aromatic compound degradation, and the synthesis of biologically essential vitamins, with an overall twofold up-regulation of expression compared with free-living cells. Quantitatively, gene regulation differences were more important than genome abundance differences in explaining why microenvironment transcriptomes differed. Taxa contributing genomes to both free-living and particle-associated communities had up to 65% of their expressed genes regulated differently between the two, quantifying the extent of transcriptional plasticity in marine microbes in situ. In response to patchiness in carbon, nutrients, and light at the micrometer scale, Amazon Plume microbes regulated the expression of genes relevant to biogeochemical processes at the ecosystem scale. PMID:25024226

Satinsky, Brandon M; Crump, Byron C; Smith, Christa B; Sharma, Shalabh; Zielinski, Brian L; Doherty, Mary; Meng, Jun; Sun, Shulei; Medeiros, Patricia M; Paul, John H; Coles, Victoria J; Yager, Patricia L; Moran, Mary Ann

2014-07-29

51

Contrasting iron isotopic compositions in river suspended particulate matter: the Negro and the Amazon annual river cycles  

NASA Astrophysics Data System (ADS)

Iron isotopic compositions (?FeIRMM-1456) of suspended particulate matter (SPM) from two major rivers in the Amazon Basin, the Amazon River itself (at the Óbidos Station) and the Negro River (at the Serrinha Station), were investigated in the present study. The main objective was to search for temporal variations during their annual river cycles. ?FeIRMM-1456 values for the Amazon River at Óbidos range between 0.00 and +0.15‰, indistinguishable from the average continental crust value. In contrast, the iron isotopic compositions of the Negro River (Serrinha Station) SPM vary between -0.34 and -0.82‰, whereas the dissolved matter is isotopically heavier in this river. The lack of significant isotopic variations in the Amazon River indicates that one individual SPM subsurface sample is representative of the river during the whole annual river cycle, in opposition to results obtained for the Negro River. The data suggest that in organic-poor white water rivers, such as the Amazon, iron isotopic signatures of the suspended fraction reflect a detrital crustal component with little isotopic fractionation. On the other hand, in the organic-rich Negro River, which has tropical podzols as the main iron source, the iron redox cycling at the water-soil interface influences the iron isotopic composition.

dos Santos Pinheiro, Giana Márcia; Poitrasson, Franck; Sondag, Francis; Cochonneau, Gérard; Vieira, Lucieth Cruz

2014-05-01

52

Similarities and differences between a large meandering river and an anabranching river: the Ucayali and Amazon River cases  

NASA Astrophysics Data System (ADS)

The Ucayali is one of the largest freely meandering rivers in the world and its planform migration produces complex meander shapes dominated by not only fluvial erosion but mainly geotechnical processes since changes on water stage are appreciable compared to medium- and small-meander rivers. The Amazon is one of the largest anabranching rivers in the world and it is formed by the confluence of the anabranching Marañon River together with the meandering Ucayali River. The seasonal increase and decrease in water and sediment discharges from the Amazonian lowland rivers produce changes in the river’s planform configuration, river flooding, and streambank erosion affecting nearby towns and navigation and shoaling issues. Even though, extensive work has been dedicated to understand both river systems, there is still no absolute understanding of their physically-based formation processes and dynamics, especially at large scales as these lowland Amazonian rivers. The Ucayali Meandering River migrates at greater rates than the Amazon Anabranching River mainly due to their single channel condition; however localized secondary channels of the latter could behave as meandering channels dominating and modifying the planform dynamics of the entire anabranching system. Insights on how a large meandering river (Ucayali) is similar and at the same time different from an anabranching river (Amazon) will be described herein. A team composed of the Earth Processes & Environmental Flows Group (EPEF) at the University of Pittsburgh and the Directorate of Hydrology and Navigation (DHN) from the Peruvian Navy is working towards gathering information and field measurements concerning the dynamics of the Amazonian rivers. Therefore, based on three-dimensional velocity and bed morphodynamic measurements (performed in both river systems using acoustic profilers and echo sounders respectively) combined with mathematical hydrodynamic models, some insights on the flow structure, bed morphology and planform dynamics of large meandering and anabranching systems are presented.

Abad, J. D.; Paredes, J. R.; Montoro, H.

2010-12-01

53

The Amazon River plume during AMASSEDS: Spatial characteristics and salinity variability  

Microsoft Academic Search

The Amazon River discharge forms a plume of low-salinity water that extends offshore and northwestward over the north Brazilian shelf. Observations acquired as part of A Multidisciplinary Amazon Shelf SEDiment Study (AMASSEDS) are used to characterize the spatial structure and temporal variability of the Amazon Plume. Four shipboard conductivity-temperature-depth (CTD) surveys spanning the shelf from 1°S to 5°N during rising

Steven J. Lentz; Richard Limeburner

1995-01-01

54

Degradation of terrestrially derived macromolecules in the Amazon River  

NASA Astrophysics Data System (ADS)

Temperate and tropical rivers serve as a significant source of carbon dioxide to the atmosphere. However, the source of the organic matter that fuels these globally relevant emissions is uncertain. Lignin and cellulose are the most abundant macromolecules in the terrestrial biosphere, but are assumed to resist degradation on release from soils to aquatic settings. Here, we present evidence for the degradation of lignin and associated macromolecules in the Amazon River. We monitored the degradation of a vast suite of terrestrially derived macromolecules and their breakdown products in water sampled from the mouth of the river throughout the course of a year, using gas chromatography time-of-flight mass spectrometry. We identified a number of lignin phenols, together with 95 phenolic compounds, largely derived from terrestrial macromolecules. Lignin, together with numerous phenolic compounds, disappeared from our analytical window following several days of incubation at ambient river temperatures, indicative of biological degradation. We estimate that the net rate of degradation observed corresponds to 30-50% of bulk river respiration. Assuming that a significant fraction of these compounds is eventually remineralized to carbon dioxide, we suggest that lignin and other terrestrially derived macromolecules contribute significantly to carbon dioxide outgassing from inland waters.

Ward, Nicholas D.; Keil, Richard G.; Medeiros, Patricia M.; Brito, Daimio C.; Cunha, Alan C.; Dittmar, Thorsten; Yager, Patricia L.; Krusche, Alex V.; Richey, Jeffrey E.

2013-07-01

55

Trace elements and radionuclides in the Connecticut River and Amazon River estuary  

SciTech Connect

The Connecticut River, its estuary, and the Amazon River estuary were studied to elucidate some of the processes which control river water chemistry and the flux of elements to the sea. The approach taken was to identify inputs to the Connecticut River and to investigate geochemical processes which modify the dissolved load. The form and quantity of nuclides which are in turn supplied to the estuary are altered by processes unique to that transition zone to the ocean. The Connecticut River estuary was sampled on a seasonal basis to investigate the role of the estuary in controlling the flux of elements to the sea. The knowledge gained from the Connecticut River study was applied to the quantitatively more significant Amazon River estuary. There a variety of samples were analyzed to understand the processes controlling the single greatest flux of elements to the Atlantic Ocean. The results indicate that estimates of the total flux of nuclides to the oceans can best be calculated based on groundwater inputs. Unless significant repositories for nuclides exist in the river-estuarine system, the groundwater flux of dissolved nuclides is that which will eventually be delivered to the ocean despite the reactions which were shown to occur in both rivers and estuaries. 153 references, 63 figures, 28 tables.

Dion, E.P.

1983-01-01

56

Spatio-temporal geochemistry of mercury in the waters of the Tapajós and Amazon rivers, Brazil  

Microsoft Academic Search

Spatial and temporal variations of mercury (Hg) concentrations were monitored in the surface waters from the lower portion of the Tapajos River, the Arapiuns River, its principal tributary, and the Amazon River at its confluence with the Tapajos. In the rivers, Hg concentrations in the water column are governed by the concentration of suspended particles. Hg in the filtered water

M. Roulet; M. Lucotte; R. Canuel; N. Farella; Y. G. De Freitos Goch; J. R. Pacheco Peleja; J.-R. D. Guimarães; D. Mergler; M. Amorim

2001-01-01

57

Tidal controls on the formation of fine-scale sedimentary strata near the Amazon river mouth  

Microsoft Academic Search

The Amazon river mouth provides a dynamic setting for studying the formation of sedimentary strata under conditions where fluvial and marine processes merge. River-mouth anchor stations were occupied for diurnal tidal cycles during three stages of river flow, and reoccupied for consecutive spring and neap tides during two stages of river flow. At each anchor station, box cores were collected

John M. Jaeger; Charles A. Nittrouer

1995-01-01

58

Logging along the Amazon River and estuary: Patterns, problems and potential  

Microsoft Academic Search

Over the last several centuries most of the logging in the Brazilian Amazon has occurred along the Lower Amazon River and estuary and for good reason. Timber has been abundant there, the costs of wood extraction and transport have been low, and access to markets has been good. In this paper we first characterize the structure of the wood sector

Ana Cristina Barros; Christopher Uhl

1995-01-01

59

Estimating Water Slope in Amazon River Tributaries Using the Shuttle Radar Topography Mission Digital Elevation Model  

Microsoft Academic Search

Extracting river height from the Shuttle Radar Topography Mission digital elevation model (SRTM DEM) for four Amazon River tributaries found water surface elevation standard deviations of 6.16 m for the Madeira River, 7.47 m for the Purus River, 5.28 m for the Negro River, and 5.35 m for the Branco River. Standard deviations and slopes were found for the Madeira,

J. Hamski; G. Lefavour; D. Alsdorf; T. Pavelsky

2006-01-01

60

Seroprevalence of Toxoplasma gondii in free-living Amazon River dolphins (Inia geoffrensis) from central Amazon, Brazil.  

PubMed

Toxoplasma gondii is an important pathogen in aquatic mammals and its presence in these animals may indicate the water contamination of aquatic environment by oocysts. Serum samples from 95 free-living Amazon River dolphins (Inia geoffrensis) from the Mamirauá Sustainable Development Reserve (RDSM), Tefé, Amazonas, Central Amazon, Brazil were tested for T. gondii antibodies using the modified agglutination test (MAT). Antibodies (MAT ? 25) to T. gondii were found in 82 (86.3%) dolphins with titers of 1:25 in 24, 1:50 in 56, and 1:500 in 2. Results suggest a high level contamination of the aquatic environment of the home range of these animals. PMID:21764516

Santos, P S; Albuquerque, G R; da Silva, V M F; Martin, A R; Marvulo, M F V; Souza, S L P; Ragozo, A M A; Nascimento, C C; Gennari, S M; Dubey, J P; Silva, J C R

2011-12-29

61

Exportation of organic carbon from the Amazon River and its main tributaries  

Microsoft Academic Search

As part of a joint Brazilian-French project, entitled Hydrology and Geochemistry of the Amazon Basin, we carried out a seven-year study (1994-2000) on the distribution, behaviour and flux of particulate and dissolved organic carbon in the Amazon River and its main tributaries (the Negro, Solimões, Branco, Madeira, Tapajós, Xingú and Trombetas rivers).The concentrations of particulate and dissolved organic carbon varied

Patricia Moreira-Turcq; Patrick Seyler; Jean Loup Guyot; Henri Etcheber

2003-01-01

62

Sources and transport of particulate organic carbon in the Amazon River and estuary  

NASA Astrophysics Data System (ADS)

Stable carbon isotope ratios have been used to study the sources of particulate organic carbon (POC) in the Amazon River and its tributaries as well as to examine the transport of the riverine POC into the oceanic environment. POC in the upper reaches of the Amazon River has more positive ? 13C values (-24·5 to -28·0‰) than that in the middle and lower reaches (-27·9 to -30·1‰). The ? 13C content of POC from the tributaries is generally more negative than that observed in the Amazon main channel. This ? 13C evidence shows that the POC in the Amazon main channel is predominantly of terrestrial origin rather than a result of in situ production. A large range of ? 13C values (-17·5 to -28·4‰) is observed in the Amazon estuary and plume and is attributed to the mixing of riverine and marine POC. POC ? 13C measurements detect riverine organic detritus as far as 290 km offshore in a direction parallel to the river channel; the isotopic signal of riverine POC can be seen as far as 1100 km to the north-west of the river mouth in the Amazon River plume.

Cai, D.-L.; Tan, F. C.; Edmond, J. M.

1988-01-01

63

Integrating GRACE measured water storage change observations into the Hillslope River Routing (HRR) in the Amazon and Congo River Basins  

Microsoft Academic Search

In this study, GRACE measured water storages are used to constrain the Hillslope River Routing (HRR) model in the Amazon and Congo River Basins. The GRACE measured water storages change observations are de-correlated, filtered and signal leakage corrected with an approximate spatial resolution of longer than 200 km (half-wavelength). The HRR model provides similar scale total water storage changes by

R. E. Beighley; Y. He; R. L. Ray; J. Guo; C. Shum

2009-01-01

64

Chemical and Carbon Isotope Composition of Varzeas Sediments and Its Interactions with Some Amazon Basin Rivers.  

National Technical Information Service (NTIS)

Varzea sediment samples were collected on the banks of Amazon rivers and in the most important tributaries. The samples were taken in three different river stages. The major cations, pH, total nitrogen, total phosphorus, carbon and delta(sup 13)C values w...

L. A. Martinelli

1986-01-01

65

Vocalizations of Amazon River Dolphins, Inia geoffrensis: Insights into the Evolutionary Origins of Delphinid Whistles  

Microsoft Academic Search

Oceanic dolphins (Odontoceti: Delphinidae) produce tonal whistles, the structure and function of which have been fairly well characterized. Less is known about the evolutionary origins of delphinid whistles, including basic information about vocal structure in sister taxa such as the Platanistidae river dolphins. Here we characterize vocalizations of the Amazon River dolphin (Inia geoffrensis), for which whistles have been reported

Jeffrey Podos; Vera M. F. da Silva; Marcos R. Rossi-Santos

2002-01-01

66

Major and trace elements of stream sediments from the lowermost Amazon River  

Microsoft Academic Search

Geochemical results from river-bottom sediments taken from the lowermost Amazon River are presented. Bedload sediments were analyzed for 10 major and 38 minor elements. Mud bulk sediments exhibit a tendency to a slight enrichment in Cr, Mn, Rb, Sr, Zr, Cs, Ba and Hf, pointing to the importance of these elements in the silt fraction. Generally, Cu, Zn, Rb, Cs,

Helenice Vital; Karl Stattegger

2000-01-01

67

Molecular cytogenetic characterization of the Amazon River dolphin Inia geoffrensis.  

PubMed

Classical and molecular cytogenetic (18S rDNA, telomeric sequence, and LINE-1 retrotransposon probes) studies were carried out to contribute to an understanding of the organization of repeated DNA elements in the Amazon River dolphin (boto, Inia geoffrensis). Twenty-seven specimens were examined, each presenting 2n = 44 chromosomes, the karyotype formula 12m + 14sm + 6st + 10t + XX/XY, and fundamental number (FN) = 74. C-positive heterochromatin was observed in terminal and interstitial positions, with the occurrence of polymorphism. Interstitial telomeric sequences were not observed. The nucleolar organizer region (NOR) was located at a single site on a smallest autosomal pair. LINE-1 was preferentially distributed in the euchromatin regions, with the greatest accumulation on the X chromosome. Although the karyotype structure in cetaceans is considered to be conserved, the boto karyotype demonstrated significant variations in its formula, heterochromatin distribution, and the location of the NOR compared to other cetacean species. These results contribute to knowledge of the chromosome organization in boto and to a better understanding of karyoevolution in cetaceans. PMID:23010983

Bonifácio, Heidi L; da Silva, Vera M F; Martin, Anthony R; Feldberg, Eliana

2012-09-01

68

Biogenic gases and the oxidation and reduction of carbon in Amazon River and floodplain waters  

Microsoft Academic Search

Concentrations of COZ, 02, CH4, and N,O in the Amazon River system reflect an oxidation- reduction sequence in combination with physical mixing between the floodplain and the mainstem. Concentrations of CO, ranged from 150 PM in the Amazon mainstem to 200-300 PM in aerobic environments and up to 1,000 PM in oxygen-depleted environments of the floodplain. Apparent oxygen utilization (AOU)

JEFFREY E. RICHEY; ALLAN H. DEVOL; STEVEN C. WOFSY; REYNALDO VICTORIA; MARIA N. G. RIBERIO

1988-01-01

69

Water resources, salinity and salt yields of the rivers of the Bolivian Amazon  

NASA Astrophysics Data System (ADS)

This is the first time that the water resources, the salinity and the yields of the upper basins of the Madera River have been reported. Formed by the confluence of the Beni and Mamore, the Madera is one of the world's largest rivers: 17,000 m 3s -1, approximately half the discharge of the Congo River. It has a dissolved discharge close to that of the Congo River: 1 ts -1 of ions. Likewise, the Beni and the Mamore Rivers, are also classified as large rivers, greater than the Volga River, the largest in Europe, and the Niger River, the second largest in Africa. The amounts of water involved are considerable. The average dissolved content of these rivers, 57-61 mg l -1 respectively, is relatively low to medium. Many types of water, classified according to their ionic compositions, have been characterized in the Andes, the Amazon Plain, and in the main drainage axis. The slightly mineralized black water of the plain seems the most unique type. Recycling of water vapor in the Amazon Basin is confirmed by the low chloride and sodium contents of the water in the plain. Thus the importance of this phenomenon in the genesis of rainfall throughout the basin is emphasized. The contribution of the Upper Madera River to the Amazon River is 9.7% of the water and 10.9% of ionic load.

Roche, Michel-Alain; Jauregui, Carlos Fernandez

1988-06-01

70

Variations of Amazon River channel flow observed by satellite gravity data  

NASA Astrophysics Data System (ADS)

The hydrological cycle of Amazon River basin, which is the largest drainage in the world, plays important roles in global climate change. During the last decade, Amazonia has experienced abnormal climate events related with recent global climate change such as severe droughts in 2005 and 2010 and extreme flooding in 2009. In this study, we show the variations of Amazon River channel flow associated with the extreme climate events with satellite gravity observation. The channel flow signal is identified via applying Empirical Orthogonal Function (EOF) for GRACE gravity data. The leading principal component (PC) shows the similar temporal variations of the Amazon River water level from satellite altimetry observation, and its spatial pattern is similar to geographic location of the river channel. The 2nd mode exhibits the North-South dipole pattern of water mass variations with the river channel as the base, and this explains one of causes for the flooding and droughts. This study of the water mass variation along the river channel is potentially useful to examine Amazon River base flow when combined with the total discharge estimate from GRACE and reanalysis.

Eom, J.; Seo, K.

2013-12-01

71

Trapping of sediment along the Amazon tidal river in diverse floodplain environments  

NASA Astrophysics Data System (ADS)

The Amazon tidal river, the freshwater reach that is influenced by tides, extends roughly 800 kilometers upstream of the river mouth. Previous studies suggest that up to one third of the sediment measured at the upstream limit of tides does not reach the ocean, and is likely trapped along the tidal river. Here we present data from a variety of depositional environments along this reach, including intertidal vegetated floodplains, floodplain lakes, and drowned tributary confluences. Sediment delivery to each of these environments is temporally variable as a result of changing tides and river stage, and spatially variable along the continuum from the purely fluvial upstream condition to the strongly tidal downstream environment. Short-term instrument records and direct observations are paired with sedimentological and radiochemical techniques to identify mechanisms of sediment exchange between river and floodplain and associated patterns of sediment accumulation. Sediments in vegetated intertidal floodplains exhibit tidal laminations and incised channel networks similar to muddy marine intertidal areas. Floodplain lakes experience dramatic seasonal changes in size, and during high flows of the river skim water and sediment from the Amazon River by providing a shortcut relative to the meandering mainstem. Amazon sediment is fluxed into the drowned tributary confluences (rías) of the Xingu and Tapajos Rivers by density-driven underflows. In the Tapajos Ría, sediment from the Amazon River has built a 25-km long birdfoot delta, suggesting these tributaries may be net sinks of sediment, rather than sources. These findings help define the importance of each tidal environment in trapping Amazon sediment before it reaches the marine environment.

Fricke, A. T.; Nittrouer, C. A.; Ogston, A. S.; Nowacki, D. J.; Souza Filho, P. W.; Silveira, O.; Asp, N. E.

2013-12-01

72

Organic matter in Bolivian tributaries of the Amazon River: A comparison to the lower mainstream  

Microsoft Academic Search

We determined the concentrations and compositions of coarse particulate (.63 mm), fine particulate (0.1-63mm), and dissolved (0.001-0.1 mm) organic matter collected along a river reach extending from a first-order stream in the Bolivian Andes, through the Beni River system, to the lower Madeira and Amazon Rivers. Dissolved organic carbon (DOC) concentrations increased down the total reach from ;80 to 350

John I. Hedges; Emilio Mayorga; Elizabeth Tsamakis; Michael E. McClain; Anthony Aufdenkampe; Paul Quay; Jeffrey E. Richey; Ron Benner; Steve Opsahl; Brenda Black

2000-01-01

73

Fluid dynamics, sediment transport and turbulent mixing at large confluences of the Amazon River  

NASA Astrophysics Data System (ADS)

The Clim-Amazon Project aims to study temporal sedimentary records to understand the mechanisms involved in climate and geodynamic changes and the processes involved in dissolved and suspended load evolution of the Amazon River basin from the Miocene to present. The knowledge of the present Amazon River sediment discharge and of its variability is fundamental since it can be linked to the on-going climatic and erosion processes at the regional scale. Understanding the relationships between these processes will be helpful to better interpret the observations of the past sedimentation rates. Within this general objective the aim of this study is to investigate the complex fluid dynamics, sediment transport and water quality processes occurring at the large confluences in the Amazon River, through a combination of theoretical, experimental (field) and numerical research. In the last decades a wide body of theoretical, experimental, and field research has emerged on the fluvial dynamics of river confluences, which are integral and ubiquitous features of river networks. Through this research substantial advances have been made into understanding the hydrodynamics and morphodynamics of river confluences which will be outlined here. However, to date most experimental studies have focused either on laboratory confluences or on small to medium sized natural confluences, whereas an extremely limited number of investigations about the confluences on large rivers. Presently little is understood about how river confluence hydrodynamics may vary with the size of the river, especially in the largest rivers. The Amazon River is the largest river in the World, with approximately 15,000 sub-branches joining the Amazon River within the Amazon Basin including some of the largest confluences on Earth. A study region containing three of the larger confluences between Manacapuru and Itacoatiara will be used as part of this study, with the primary focus being the confluence of the Rio Negro and Rio Solimões. The primary objective of this study is to develop a conceptual model for flow dynamics and sediment transport about such large confluences through analysis of field data, to assist with general objectives of the Clim-Amazon Project and improve general understanding of large confluence dynamics. While another objective is to apply CFD methods based on field measurements to improve the understanding of the dynamical processes that determine water quality parameters and sediment transport, mixing and accumulation at the confluences of large rivers such as the Amazon River. Therefore the main focus of this presentation will be the proposed field methodology for collecting hydrodynamic, sediment transport, water quality and bathymetric data about these large confluences within the study region of the Amazon River. As well as how the data collected during these field measurements will be analysed and used to develop conceptual and numerical models of such large confluences.

Trevethan, Mark; Gualtieri, Carlo; Filizola, Naziano; Ianniruberto, Marco

2014-05-01

74

The evolution of organic matter along the lower Amazon River continuum - Óbidos to the ocean  

NASA Astrophysics Data System (ADS)

The influence of the Amazon River on global hydrologic and biogeochemical cycling is well recognized. The Amazon River provides roughly 16% of the global freshwater supply to the ocean and is a significant source of CO2 to the atmosphere, outgassing 0.5 Pg C y-1 to the atmosphere--a flux roughly equivalent to the amount of carbon 'sequestered' by the Amazon rainforest (Field et al, 1998; Richey et al., 2002; Malhi et al., 2008). However, much of our understanding of the flux of matter from the Amazon River into the Atlantic Ocean (and atmosphere) is limited to measurements made at and upstream of Óbidos, 900 km upstream from the actual river mouth. Further, there are few to no observations documenting the transformation of organic matter in a parcel of water as it travels downstream of Óbidos into the ocean. Here we explore the hydrological and biogeochemical evolution of the lower Amazon River continuum, from Óbidos to the Atlantic Ocean. A suite of dissolved and particulate organic matter (OM) parameters were measured during a series of five river expeditions with stations at Óbidos, the Tapajós tributary, the mouth of the Lago Grande de Curuai floodplain lake, both the north and south channels of the Amazon River mouth near Macapá, and the confluence of the Amazon and Tocantins Rivers near Belém. In addition to bulk carbon isotopic signatures, a suite of biomarkers including dissolved and particulate lignin-derived phenols were measured to trace the sources and degradation history of terrestrial vascular plant derived OM throughout the continuum. Dissolved and particulate lignin phenol concentrations both correlated positively with river discharge in the Amazon River mainstem, with variable export patterns from the tributaries and floodplains. As organic matter travels along the continuum it is degraded by microbial composition, fuelling gross respiration and CO2 outgassing. The flux of organic carbon to the ocean is chemically recalcitrant as a result of the constant biological processing of labile OM throughout the lower river. We estimate that 40% of the vascular plant-derived organic carbon sequestered by the terrestrial biosphere is degraded within soils, 55% is degraded along the river continuum, and less than 5% is delivered to the ocean (Ward et al., 2013) References Cited Field, C., M. Behrenfeld, J. Randerson, and P. Falkowski. 1998. Primary production of the biosphere: Integrating terrestrial and oceanic components. Science 281, 237-240. Malhi, Y., Roberts, J.T., Betts, R.A., Killeen, T.J., Li, W., Nobre, C.A. 2008. Climate change, deforestation, and the fate of the Amazon. Science 319, 169-172. Richey, J. E., Melack, J. M., Aufdenkampe, A. K., Ballester, V. M. & Hess, L. L. 2002. Outgassing from Amazonian rivers and wetlands as a large tropical source of atmospheric CO2. Nature 416, 617-620. Ward, N.D.; Keil, R.G.; Medeiros, P.M.; Brito, D.C.; Cunha, A.C.; Dittmar, T.; Yager, P.L.; Krusche, A.V.; Richey, J.E. 2013. Degradation of terrestrially derived macromolecules in the Amazon River. Nature Geoscience. doi: 10.1038/ngeo1817

Ward, N. D.; Keil, R. G.; Medeiros, P. M.; Brito, D.; Cunha, A.; Sawakuchi, H. O.; Moura, J. S.; Yager, P. L.; Krusche, A. V.; Richey, J. E.

2013-12-01

75

Marine environmental changes at the Brazilian equatorial margin related to Amazon River evolution during the Neogene  

NASA Astrophysics Data System (ADS)

Today, the nutrient-rich Amazon River outflow causes massive algal blooms in the western equatorial Atlantic Ocean, forming a considerable carbon sink as well as a primary food source in the otherwise oligotrophic surface water. However, the history of this high-productivity system is largely unknown, although a strong relation to the evolution of the Amazon River can be expected. The Amazon submarine fan provides direct evidence for the development of a transcontinental river system, of which the base of the primarily Andean-sourced siliciclastic deposits is dated as late Miocene. Ditch cuttings from Amazon Fan exploration 'Well 2' were made available by Petrobras for microfossil and lithological research. 'Well 2' is located on the uppermost fan at a water depth of 750 meters. Organic-walled dinoflagellate cyst and foraminifer assemblages were studied to reconstruct Neogene marine environmental changes in relation to the Amazon River development. Planktonic foraminifera are present throughout the studied section and largely confirm the already available biostratigraphic age determination based on nannofossils. Benthic foraminifer assemblages indicate that the paleo-water depth has not substantially deviated from current conditions. The ecological affinities of most observed dinocyst taxa are well known, which allows us to reconstruct changes in paleo-productivity based on the assemblages. Mineral composition suggests that local river systems already drained into the Amazon basin before the onset of the transcontinental system, but environmental conditions remained oligotrophic at this time. Decreased abundances of both dinocysts and planktonic foraminifera during the Pleistocene are related to highest sedimentation rates (dilution effect). Overall, a complex interplay of orogenesis, climatic and sea level variations during the Neogene are responsible for the fluvially-induced changes in the marine environment at the Atlantic margin.

Lammertsma, Emmy; Troelstra, Simon; Sangiorgi, Francesca; Chemale, Farid, Jr.; do Carmo, Dermeval A.; D'Avila, Roberto; Soares, Emilson; Hoorn, Carina

2014-05-01

76

Storage and remobilization of suspended sediment in the lower amazon river of Brazil  

USGS Publications Warehouse

In the lower Amazon River, suspended sediment is stored during rising stages of the river and resuspended during falling river stages. The storage and resuspension in the reach are related to the mean slope of the flood wave on the river surface; this slope is smaller during rising river stages than during falling stages. The pattern of storage and resuspension damps out the extreme values of high and low sediment discharge and tends to keep them near the mean value between 3.0 ?? 106 and 3.5 ?? 106 metric tons per day. Mean annual discharge of suspended sediment in the lower Amazon is between 1.1 ?? 109 and 1.3 ?? 109 metric tons per year.

Meade, R. H.; Dunne, T.; Richey, J. E.; Santos, U. De. M.; Salati, E.

1985-01-01

77

Monitoring river water levels in the Amazon Basin using ICESat GLAS  

NASA Astrophysics Data System (ADS)

The use of the ICESat (Ice, Cloud and land Elevation Satellite) sensor GLAS (Geoscience Laser Altimeter System) for monitoring terrestrial water levels is relatively unexplored. Now, these data are being used to investigate water levels of the River Amazon. Catchments like that of the River Amazon are often poorly monitored from the ground due to their large size and the expense associated with installing and maintaining gauge networks. Using space-borne remote sensing to create virtual gauging stations allows more data to be obtained for such uses as hydraulic model input. However, another issue associated with the gauges of the Amazon, other than the limited number and the distances between them (up to 200 km), is the inconsistent geodetic levelling. Corrections of the geodetic levels of the Amazon gauges have never been fully published, though attempts have been made using Topex/Poseidon. Now these corrections will be found using ICESat. GLAS is ideal for this research due to the small footprint of approximately 70 m. Although monitoring of terrestrial hydrology was not within the mission objectives, initial investigations have been promising. A proof of concept study has now been carried out, using comparisons between ICESat GLAS elevations and reliable gauge stations on the Mississippi River and the River Danube. This study has shown that GLAS is able to accurately measure water elevations. GLAS will now be used to correct selected Amazon gauges with the aim of using the results to update the HEC-RAS and LISFLOOD-FP models for a 325 km stretch of the Amazon which has been previously investigated.

Hall, A. C.; Schumann, G.; Bamber, J. L.; Bates, P. D.

2010-12-01

78

Branco River Stage Gradient Determination and Amazon Hydrologic Studies Using GPS Water Level Measurements  

Microsoft Academic Search

This study presents the result of a demonstration of Global Positioning System (GPS) hydrologic studies in a remote area. A GPS campaign was conducted using a GPS-equipped vessel and a GPS buoy to measure water level along Rio Branco, a tributary of the Amazon. The GPS water level data agree well with river gauge data and with ENVISAT radar altimeter

Kai-Chien Cheng; Stephane Calmant; Chung-Yen Kuo; Hong-Zeng Tseng; C. K. Shum; Frederique Seyler; Joecila Santos Da Silva

2009-01-01

79

Experimentally Demonstrated Echolocation in the Amazon River Porpoise, Inia Geoffrensis (Blainville).  

National Technical Information Service (NTIS)

Echolocation and related behavior in the Amazon River porpoise Inia geoffrensis was investigated to demonstrate biological sonar within the context of operant conditioning. It was found that the Inia's click train ranged from 25 to 200 kHz; major energy w...

R. H. Penner A. E. Murchison

1970-01-01

80

The Amazon river breeze and the local boundary layer: I. Observations  

Microsoft Academic Search

Observations of the diurnal evolution of the planetary boundary layer over the Amazon rain forest, made at sites close to the confluence of the Solimões and Negro rivers (approximately at 3°S, 60°W) near Manaus, Amazonas, Brazil, show the existence of a diurnal rotation of the wind near the surface and the frequent presence of low-level nocturnal wind maxima. These circulations

AMAURI PEREIRA DE OLIVEIRA; David R. Fitzjarrald

1993-01-01

81

The water budget in the Amazon River basin during the FGGE period  

Microsoft Academic Search

The seasonal change of the water budget in the Amazon River basin during the FGGE period is investigated, using the global objective analysed data set, precipitation data and discharge data. Some difference is found between the annual water vapour flux convergence and the annual runoff obtained by discharge data. This is due to the characteristics of the global objective analysed

HIROSHI MATSUYAMA; KOOITI MASUDA

1993-01-01

82

Estimating suspended sediment concentrations in surface waters of the Amazon River wetlands from Landsat images  

Microsoft Academic Search

A method has been developed, based on spectral mixture analysis, to estimate the concentration of suspended sediment in surface waters of the Amazon River wetlands from Landsat MSS and TM images. Endmembers were derived from laboratory reflectance measurements of water-sediment mixtures with a range of sediment concentrations. Using these references spectra, the authors applied a linear mixture analysis to multispectral

L. A. K. Mertes; M. O. Smith; J. B. Adams

1993-01-01

83

VENEZUELAN EQUINE ENCEPHALITIS FEBRILE CASES AMONG HUMANS IN THE PERUVIAN AMAZON RIVER REGION  

Microsoft Academic Search

A survey was conducted from October 1, 1993 to June 30, 1995 to determine the arboviral etiologies of febrile illnesses in the city of Iquitos in the Amazon River Basin of Peru. The study subjects were patients who were enrolled at medical care clinics or in their homes by Peruvian Ministry of Health (MOH) workers as part of the passive

DOUGLAS M. WATTS; JOHNNY CALLAHAN; CINDY ROSSI; M. STEVEN OBERSTE; J. T. ROEHRIG; MARK T. WOOSTER; JONATHAN F. SMITH; C. B. CROPP; ELMER M. GENTRAU; NICK KARABATSOS; DUANE GUBLER; CURT G. HAYES

84

Mercury in Fish-eating Communities of the Andean Amazon, Napo River Valley, Ecuador  

Microsoft Academic Search

This exploratory study aimed to examine the relationship between fish eating habits, human mercury levels, and mercury levels in fish in three communities of the Napo River Valley, Ecuadorian Andean Amazon, a region without gold mining but with significant deforestation and volcanic soils with naturally high mercury levels. By recognizing the politicoeconomic factors which cause deforestation, the cultural factors which

Jena Webb; Nicolas Mainville; Donna Mergler; Marc Lucotte; Oscar Betancourt; Robert Davidson; Edwin Cueva; Edy Quizhpe

2004-01-01

85

Modeling River Hydrologic Regime and Spawning of Migratory Catfishes in Southeastern Peruvian Amazon  

NASA Astrophysics Data System (ADS)

Seasonal hydrologic conditions and catfish larvae production were evaluated in the Madre de Dios River in order to determine whether environmental conditions influence the reproductive activity of a group of large, commercially important catfishes, in the Southeastern Peruvian Amazon. A simple stochastic model of floods is presented to describe the influence of the natural high flow regime on observed patterns of catfish larvae release and drifting. Daily river stage records at Puerto Maldonado are related to weekly larval catches to determine the association between flood and spawning events. On the basis of hydroclimatologic characteristics of Andean- Amazon regions, available long-term historical rainfall records are employed to approximate the likely inter- annual variability of floods within this Amazon headwater basin. Major larval drift appeared associated with stages of over the 5 m, or "Biologic Hydrologic Significant Events" (BSE), which act as triggers, or a reasonable surrogates, for spawning responses of these species. The timing of BSEs, estimated from the historical rainfall records, appear to be uniformly distributed during the rain season and their inter-arrival times exponential. These observations provided the basis of the stochastic model describing the likelihood of volumes of larvae releases from the headwater region to lowland Amazon. The ecologically significant role of the hydroclimatology of this region in the complete life cycle of this important Amazon fish resource is illustrated.

Canas, C. M.; Waylen, P. R.

2008-05-01

86

Seasonal dynamics in methane emissions from the Amazon River floodplain to the troposphere  

Microsoft Academic Search

Methane fluxes to the troposphere from the three principal habitats of the floodplain of the Amazon River main stem (open waters, emergent macrophyte beds, and flooded forests) were determined along a 1,700-km reach of the river during the low-water period of the annual flood cycle (November-December 1988). Overall, emissions averaged 68 ({plus minus} 20) mg CHâ m⁻² d⁻¹ and were

Allan H. Devol; Jeffrey E. Richey; Bruce R. Forsberg; Luiz A. Martinelli

1990-01-01

87

Iron isotopes in the Amazon River system: Weathering and transport signatures  

Microsoft Academic Search

Trace metal clean plankton tows, river samples, aerosol leachates, and porewater samples from the Amazon River system were measured for their iron isotopic composition. The overall isotopic range observed was 1.5‰ with Fe isotopic variability observed between different types of tributaries. Dissolved Fe and suspended load Fe from two main channel sites were isotopically similar (? ?0.1 to ?0.3‰). In contrast,

B. A. Bergquist; E. A. Boyle

2006-01-01

88

Source, transport and fluxes of Amazon River particulate organic carbon: Insights from river sediment depth-profiles  

NASA Astrophysics Data System (ADS)

In order to reveal particulate organic carbon (POC) source and mode of transport in the largest river basin on Earth, we sampled the main sediment-laden tributaries of the Amazon system (Solimões, Madeira and Amazon) during two sampling campaigns, following vertical depth-profiles. This sampling technique takes advantage of hydrodynamic sorting to access the full range of solid erosion products transported by the river. Using the Al/Si ratio of the river sediments as a proxy for grain size, we find a general increase in POC content with Al/Si, as sediments become finer. However, the sample set shows marked variability in the POC content for a given Al/Si ratio, with the Madeira River having lower POC content across the measured range in Al/Si. The POC content is not strongly related to the specific surface area (SSA) of the suspended load, and bed sediments have a much lower POC/SSA ratio. These data suggest that SSA exerts a significant, yet partial, control on POC transport in Amazon River suspended sediment. We suggest that the role of clay mineralogy, discrete POC particles and rock-derived POC warrant further attention in order to fully understand POC transport in large rivers.

Bouchez, Julien; Galy, Valier; Hilton, Robert G.; Gaillardet, Jérôme; Moreira-Turcq, Patricia; Pérez, Marcela Andrea; France-Lanord, Christian; Maurice, Laurence

2014-05-01

89

The geochemistry of rare earth elements in the Amazon River estuary  

SciTech Connect

The estuarine geochemistry of rare earth elements (REEs) was studied using samples collected in the Amazon River estuary from the AmasSeds (Amazon Shelf SEDiment Study) cruise of August 1989. Extensive removal of dissolved (0.22 [mu]m filtered) trivalent REEs from river water occurs in the low (0--6) salinity region. Removal by the salt-induced coagulation of river colloids leads to fractionation among the REE(III) series; the order of removal is light REEs > middle REEs > heavy REEs. There also is the enhanced removal of Ce (relative to trivalent La and Nd) in the low salinity (0--6) zone and in the zone of high biological activity. This is the first field observation of strong Ce removal associated with coagulation of river colloids and biological productivity. The argument is made that the decrease in the Ce anomaly across a biological front is caused by biologically mediated oxidation of Ce(III) to Ce(IV). Coagulation of river colloids and biologically mediated oxidation of Ce(III) lead to fractionation of REE(III) and redox modification of Ce. These processes result in the REE composition becoming fractionated relative to the Amazon River water and crust and more evolved toward the REE composition of the oceans. This study implies that reactions in estuaries play significant, yet poorly understood roles in controlling the REE composition and Ce anomaly of the oceans. 46 refs., 9 figs., 2 tabs.

Shokovitz, E.R. (Woods Hole Oceanographic Institution, MA (United States))

1993-05-01

90

Mercury pollution in the Tapajos River basin, Amazon  

Microsoft Academic Search

There is increasing concern about the potential neurotoxic effects of exposure to methylmercury for the 6 million people living in the Amazon, even in regions situated far away from the gold mines (garimpos), considered to be the major source of mercury pollution. In November 1998, a spot investigation on mercury contamination was conducted in three fishing villages (Barreiras, Rainha, and

Masazumi Harada; Junko Nakanishi; Eiichi Yasoda; Maria da Conceicâo N Pinheiro; Teiichi Oikawa; Geraldo de Assis Guimarâes; Bernardo da silva Cardoso; Takako Kizaki; Hideki Ohno

2001-01-01

91

Depth-integrated suspended sediment and geochemical fluxes in large rivers: the Amazon River system  

NASA Astrophysics Data System (ADS)

Erosion and weathering produce a wide range of residual solid products, in terms of size, density, mineralogy and chemical composition. These solid products are then transported by rivers from the continents to the oceans as suspended particulate matter (SPM) and bedload. Large rivers account for an important part of this transfer of sediments at the global scale. In those rivers, deep channels allow for vertical differentiation, or sorting, of suspended sediment, following their size and density. This hydrodynamic sorting results in vertically heterogeneous depth-profiles in terms of SPM concentration and size distribution (e.g. Garcia, 2008), which in turn likely result in an heterogeneous chemical composition of SPM throughout channel depth (e.g. Galy, 2007), which has to be evaluated. We sampled river water of the main tributaries of the Amazon River system (in the lowland basin), at two distinct water-stages, at various depths following depth-profiles, using a point depth-sampler. After filtration, and SPM recovery, SPM concentration, grain size distribution and chemical composition were determined. River discharge and water velocity throughout the sampled cross-sections were recorded using Acoustic Doppler Current Profiler (ADCP). The large increase in SPM concentration with depth observed at most of the sampled depth-profiles is well accounted for by the Rouse model (e.g. Rouse, 1950). This analysis allows us to reliably infer the SPM concentration and grain size distribution throughout the sampled river cross-section, and thus to estimate the spatially-integrated instantaneous SPM flux using ADCP data (Bouchez et al., 2010). The study also emphasizes the potential role of particle aggregation, within the river system, as a complicating factor regarding the prediction of these depth-integrated SPM fluxes from easily measurable hydrodynamic parameters (surface SPM concentration and grain size, and water velocity). Then, using the previous analysis, combined with the strong correlation between grain size parameters and chemical composition of suspended sediment observed in our set of samples, we deduce the chemical composition of SPM throughout the cross-section, and thus the spatially-integrated chemical fluxes transported as suspended load for a number of elements. These results are finally compared with “simple” estimates relying on the geochemistry of channel surface suspended sediments. This highlights the different behaviors of chemical elements with respect to hydrodynamic sorting in large rivers. References: M.H. Garcia, 2008, Sedimentation engineering: processes, measurements, modeling and practice, EWRI. V. Galy et al., 2007, Nature 450 : 407-411. H. Rouse, 1950, Engineering Hydraulics, Wiley, New York. J. Bouchez et al., 2010, Hydrol. Proc., accepted.

Bouchez, J.; Lupker, M.; Gaillardet, J.; Metivier, F.; France-Lanord, C.; Maurice, L.

2010-12-01

92

Geochemical behavior of rare earth elements and other trace elements in the Amazon River  

NASA Astrophysics Data System (ADS)

Rivers transport large amounts of dissolved and suspended particulate material from the catchment area to the oceans and are a major source of trace metals to seawater. The Amazon River is the world's largest river and supplies approximately 20% of the oceans' freshwater (Molinier et al., 1997). However, the behavior of trace elements, especially particle-reactive elements such as the rare earth elements (REE), within the river as well as in the estuary is not well constrained and rather little is known about their transport mechanisms. This study aims at understanding the transport properties of particle-reactive elements in the Amazon River and some of its major tributaries, including the Rio Solimões, Rio Negro, Tapajos, Xingu and Jari Rivers. Samples were taken at 12 stations, seven of which were located in the Amazon mainstream, while the other five stations sampled its tributaries. To account for the effects of variable discharge, the samples were collected during periods of high and low discharge. We present data for major and trace elements, including REE, of the dissolved and suspended load of these samples. First results indicate that the shale-normalized REE pattern of the dissolved load (filtered through 0.2 µm membranes) of the Amazon mainstream and the Rio Solimões confirm earlier studies (Elderfield et al., 1990; Gerard et al., 2003) and show an enrichment of the middle REE relative to the light and heavy REE (LaSN/GdSN: 0.25 - 0.32; GdSN/YbSN: 1.54 - 1.78). In contrast to the Amazon mainstream and the Rio Solimões, which are considered to be whitewater rivers, blackwater rivers, such as the Rio Negro, have a flat REE pattern with higher REE concentrations than whitewater rivers. The third water-type found in the Amazon Basin is clearwater, e.g. Rio Tapajos, with REE patterns in between those of the other two types, i.e. LaSN/GdSN: 0.55 - 0.70; GdSN/YbSN: 1.26 - 1.55. A similar behavior can be identified for other major and trace elements. While elements such as Ca, Mg, Sr or U are relatively high in whitewater rivers, their concentrations are generally lower in clearwater rivers and lowest in blackwater rivers. In contrast, elements including Si, Rb and Cs have their highest concentrations in blackwater rivers, intermediate concentrations in clearwater rivers and their lowest concentrations in whitewater river. [1] Elderfield H., Upstill-Goddard R. and Sholkovitz E.R. (1990): The rare earth elements in rivers, estuaries and coastal seas and their significance to the composition of ocean waters. Geochim.Cosmochim.Acta, 54, 971-991 [2] Gerard M., Seyler P., Benedetti M.F., Alves V.P., Boaventura G.R. and Sondag, F. (2003): Rare earth elements in the Amazon basin. Hydrological Processes, 17, 1379-1392 [3] Molinier M., Guyot J.L., Callede J., Guimaraes V., Oliveira E. and Filizola N. (1997): Hydrologie du bassinamazonien. Evironment et développement en Amazonie brésiliènne, Thery H. (ed.), Berlin Publ., Paris; 24-41

Merschel, Gila; Bau, Michael; Dantas, Elton Luiz

2014-05-01

93

Distribution and flux of /sup 226/Ra and /sup 228/Ra in the Amazon River estuary  

SciTech Connect

Measurements of /sup 226/Ra and /sup 228/Ra in the Amazon River estuary show that desorption from riverborne suspended particulate matter in the estuary increases the riverine flux of both isotopes to the ocean by a factor of approximately 5 over the flux attributable to radium dissolved in the river water alone. The total Amazon flux supplies approximately 0.20% of the /sup 226/Ra and approximately 2.6% of the /sup 228/Ra standing crops in the near-surface Atlantic (0-200 m). Diffusive flux from estuarine and shelf sediments and desorption from resuspended sediments in the region of the estuary approximately double the estuarine /sup 226/Ra concentration and quadruple the estuarine /sup 228/Ra concentration above that caused by the dissolved and desorbed river components alone.

Key, R.M.; Sarmiento, J.L.; Stallard, R.F.; Moore, W.S.

1985-07-20

94

Source area and seasonal variation of dissolved Sr isotope composition in rivers of the Amazon basin  

NASA Astrophysics Data System (ADS)

We present dissolved Sr isotope data collected over 8 years from three main river systems from the Amazon Basin: Beni-Madeira, Solimões, Amazon, and Negro. The data show large 87Sr/86Sr ratio variations that were correlated with the water discharge and geology of the source areas of the suspended sediments. The Beni-Madeira system displays a high average 87Sr/86Sr ratio and large 87Sr/86Sr fluctuations during the hydrological cycle. This large average value and fluctuations were related to the presence of Precambrian rocks and Ordovician sediments in the source area of the suspended sediment of the river. In contrast, the Solimões system displays a narrow range of Sr isotope ratio variations and an average value close to 0.709. This river drains mostly Phanerozoic rocks of northern Peru and Ecuador that are characterized by low Sr isotope ratios. Despite draining areas underlain by Precambrian rocks and having high 87Sr/86Sr ratios, such rivers as the Negro and Tapajós play a minor role in the total Sr budget of the Amazon Basin. The isotopic fluctuations in the Beni-Madeira River were observed to propagate downstream at least as far as Óbidos, in the Amazon River. This signal is characterized by an inverse relationship between the concentration of elemental Sr and its isotopic ratios. During the raining season there is an increase in Sr isotopic ratio accompanied by a decrease in elemental Sr concentration. During the dry season, the Sr isotopic ration decreases and the elemental Sr concentration increases.

Santos, Roberto V.; Sondag, Francis; Cochonneau, Gerard; Lagane, Christelle; Brunet, Pierre; Hattingh, Karina; Chaves, Jeane G. S.

2014-05-01

95

A RETROSPECTIVE STUDY OF PATHOLOGIC FINDINGS IN THE AMAZON AND ORINOCO RIVER DOLPHIN (INIA GEOFFRENSIS) IN CAPTIVITY  

Microsoft Academic Search

River dolphins are especially susceptible to negative human impacts. For their conservation, attempts of relocation or procreation ex situ may become important in the future to avoid their extinction. Additional knowledge and medical experiences of river dolphin management in captivity may aid such conservation efforts. The medical records and necropsy and histopathology reports on 123 captive Amazon River dolphins (Inia

Christopher J. Bonar; Ernesto O. Boede; Manuel García Hartmann; Joanne Lowenstein-Whaley; Esmeralda Mujica-Jorquera; Scott V. Parish; James V. Parish; Michael M. Garner; Cynthia K. Stadler

2007-01-01

96

Rivers in the sea - Can we quantify pigments in the Amazon and the Orinoco River plumes from space?  

NASA Technical Reports Server (NTRS)

Coastal Zone Color Scanner (CZCS) images of the western tropical Atlantic (1979-1982) were combined into monthly mean surface pigment fields. These suggest that Amazon River water flows along northeastern South America directly toward the Caribbean sea early in the year. After June, however, the North Brazil Current is shunted eastward, carrying a large fraction of Amazon water into the North Equatorial Countercurrent (NECC). This eastward flow causes diminished flow through the Caribbean, which permits northwestward dispersal of Orinoco River water due to local Ekman forcing. The Orinoco plume crosses the Caribbean, leading to seasonal variation in surface salinity near Puerto Rico. At least 50 percent of the pigment concentration estimated in these plumes seems due to viable phytoplankton.

Muller-Karger, Frank E.; Walsh, John J.; Carder, Kendall L.; Zika, Rod G.

1989-01-01

97

Particulate organic carbon, sterols, fatty acids and pigments in the Amazon River system  

Microsoft Academic Search

Water samples were collected from the Amazon River system during a high flood period, in June 1989, and lipids associated with particles retained on GF\\/F filters were examined. Particles showed a highly variable organic carbon content (1.8–29.0%). Corresponding organic carbon concentrations varied from 0.36 to 1.13 mg\\/l. The flood conditions encountered during the sampling period may feed exceptional inputs of

A. Saliot; L. Mejanelle; P. Scribe; J. Fillaux; C. Pepe; A. Jabaud; J. Dagaut

2001-01-01

98

Distribution and partition of total mercury in waters of the Tapajós River Basin, Brazilian Amazon1  

Microsoft Academic Search

Filtered water and particulate burdens of Hg 0.43)2.81 ngrl and 0.28)13.13 ngrl, respectively in the Tapajos ´ . River Brazilian Amazon are one order of magnitude lower than previously reported concentrations in Amazonian waters. Hg content in the water column is influenced by the amount of particulate matter and is independent from upstream goldmining activities. The particulate load of Hg

M. Roulet; M. Lucotte; R. Canuel; I. Rheault; S. Tran; Y DEFREITOSGOG; N FARELLA; R SOUZADOVALE; C SOUSAPASSOS; E DEJESUSDASILVA

1998-01-01

99

Sr?Nd?Pb isotope systematics in Amazon and Congo River systems: constraints about erosion processes  

Microsoft Academic Search

87Sr86Sr, 143Nd144Nd, 206Pb204Pb, 207Pb204Pb and 208Pb204Pb isotopic ratios and Rb, Sr, Sm, Nd, U, Pb and Th concentrations have been measured in the suspended loads of the Congo and Amazon rivers and their tributaries. In the dissolved load, 87Sr86Sr, Rb, Sr, Nd, Sm, U, Pb and Th concentrations are also reported.These results show that Nd, Sm, Th and Pb are

Claude J. Allègre; Bernard Dupré; Philippe Négrel; Jérôme Gaillardet

1996-01-01

100

A significant CO2 sink in the tropical Atlantic Ocean associated with the Amazon River plume  

Microsoft Academic Search

During Meteor cruise 55 a strong undersaturation of surface seawater with respect to atmospheric CO2 was found in the Amazon River plume which is advected into the surface circulation of the tropical Atlantic. A conservative estimate of the plume-related CO2 sink in the tropical Atlantic yields a net air-sea flux of 0.014 +\\/- 0.005 Pg C yr-1. The corresponding average

Arne Körtzinger

2003-01-01

101

Compositions and fluxes of particulate organic material in the Amazon River  

Microsoft Academic Search

Lignin, elemental, and stable carbon isotope compositions are reported for local plants and for coarse (>63 pm) and fine (~63 pm) suspended particulate materials collected along a 1,950-km reach of the lower Amazon River during four contrasting stages of the 1982-1983 hydrograph. Fluxes of chemically recognizable lignin in the two size classes generally parallel each other along the mainstem with

JOHN I. HEDGES; WAYNE A. CLARK; PAUL D. QUAY; JEFFREY E. RICHEY; ALLAN H. DEVOL; UMBERTO DE M. SANTOS

1986-01-01

102

C-13\\/C-12 of atmospheric CO2 in the Amazon basin - Forest and river sources  

Microsoft Academic Search

Results are presented of measurements of the CO2 concentrations and C-13\\/C-12 ratios in CO2 in air samples collected from within the Amazonian rain forest and over the Amazon river between 1982 and 1987. Results indicate the presence of a diurnal cycle in the CO2 concentration and the C-13\\/C-12 ratio. It was found that the CO2 input to air in the

Paul Quay; Stagg King; Dave Wilbur; Jeffrey Richey; Steven Wofsy

1989-01-01

103

Numerical simulation of drainage reversal of the Amazon River during Andean orogeny  

NASA Astrophysics Data System (ADS)

The uplift of Central and Northern Andes occurred concomitantly with an important reorganization of the drainage pattern in Northern South America. During the Early Miocene, the fluvial systems that flowed from the Amazonian Craton toward the sub-Andean basins and northward to the Caribbean were replaced by a megawetland, the Pebas system, covering a large fraction of the Western Amazonia. In the Late Miocene the Pebas system progressively disappeared and gave place to the transcontinental Amazon River, connecting the Andes and the equatorial Atlantic margin. A previous work suggested that the reversal of the Amazon River and the disappearance of the Pebas system were driven by dynamic topography promoted by mantle convection. Based on numerical models that couple surface processes, flexural isostasy and crustal thickening due to orogeny, here I propose that the response of the surface processes to the uplift of the Central and Northern Andes, along with the flexural isostasy of the lithosphere, can explain the drainage reversal of the Amazon River during the Miocene without invoking dynamic topography induced by mantle convection. In addition I observed that the existence, the permanence and the size of a megawetland in Northern South America is controlled by the rate of crustal thickening in the orogeny, the rate of erosion and, mainly, the efficiency of the sediment transport through the drainage basins during the Andean uplift.

Sacek, Victor

2014-05-01

104

Seasonal dynamics in methane emissions from the Amazon River floodplain to the troposphere  

SciTech Connect

Methane fluxes to the troposphere from the three principal habitats of the floodplain of the Amazon River main stem (open waters, emergent macrophyte beds, and flooded forests) were determined along a 1,700-km reach of the river during the low-water period of the annual flood cycle (November-December 1988). Overall, emissions averaged 68 ({plus minus} 20) mg CH{sub 4} m{sup {minus}2} d{sup {minus}1} and were significantly lower than similar emissions determined previously for the high-water period, 184 ({plus minus} 41) mg CH{sub 4} m{sup {minus}2} d{sup {minus}1} (July-August 1986). This difference was due to significantly lower emissions from floating macrophyte environments. Low-water emissions from open waters and flooded forest areas were not significantly different than at high water. A monthly time series of methane emissions from eight lakes located in the central Amazon basin showed similar results. Average annual emission from the lakes was 125 ({plus minus} 28) mg CH{sub 4} m{sup {minus}2} d{sup {minus}1}. Methane emissions from lakes were significantly higher during the high water period, again primarily due to an increase in emissions from macrophyte habitats. The data were used to calculate a seasonally weighted annual emission to the troposphere from the Amazon River main stem floodplain of 5.1 Tg yr{sup {minus}1}, which indicates the importance of the area in global atmospheric chemistry.

Devol, A.H.; Richey, J.E. (Univ. of Washington, Seattle (USA)); Forsberg, B.R. (Instituto Nacional de Pesquisas da Amazonia, Manaus (Brazil)); Martinelli, L.A. (Centro de Energia Nuclear na Agricultura, Piracicaba (Brazil))

1990-09-20

105

Seasonal dynamics in methane emissions from the Amazon River floodplain to the troposphere  

NASA Technical Reports Server (NTRS)

Methane fluxes to the troposphere from the three principal habitats of the floodplain of the Amazon River main stem (open waters, emergent macrophyte beds, and flooded forests) were determined along a 1700-km reach of the river during the low-water period of the annual flood cycle (November-December 1988). Overall, emissions averaged 68 mg CH4/sq m per day and were significantly lower than similar emissions determined previously for the high-water period, 184 mg CH4/sq m per day (July-August 1986). This difference was due to significantly lower emissions from floating macrophyte environments. Low-water emissions from open waters and flooded forest areas were not significantly different than at high water. A monthly time series of methane emission from eight lakes located in the central Amazon basis showed similar results. The data were used to calculate a seasonally weighted annual emission to the troposphere from the Amazon River main stem floodplain of 5.1 Tg/yr, which indicates the importance of the area in global atmospheric chemistry.

Devol, Allan H.; Richey, Jeffrey E.; Forsberg, Bruce R.; Martinelli, Luiz A.

1990-01-01

106

Molecular cloning of two tropomyosin family genes and expression analysis during development in oriental river prawn, Macrobrachium nipponense.  

PubMed

This paper reports that Slow-tonic S2 tropomyosin (Sst) and Slow tropomyosin isoform (Sti) was highly expressed in androgenic gland transcriptome of Macrobrachium nipponense, which may play crucial roles in sexual differentiation to maleness. In this study, two Sst and Sti gene homologues designated as Mnsst and Mnsti were cloned and characterized from a freshwater prawn M. nipponense. The full-length cDNA of Mnsst and Mnsti consists of 997bp and 1926bp, respectively, with an ORF of 852bp encoding 284 amino acids, and the similarity in ORF reached to 95.82%. The deduced amino acid sequences of Mnsst and Mnsti shared the highest identity with Slow-tonic S2 tropomyosin and Slow tropomyosin isoform of Homarus americanus. Real-time quantitative RT-PCR showed that the Mnsst and Mnsti genes were expressed in different tissues with the highest level of expression in the androgenic gland, implying that these two genes may be related to sex-determination in M. nipponense. Real-time quantitative RT-PCR revealed that in addition, Mnsst and Mnsti were speculated to be related with embryonic organogenesis of M. nipponense, especially for the formation of complete mouthpart and digestive organ and stimulating larval changes of morphology and initiate metamorphosis, the results of present study implied that the two genes may play complex and important roles in sex differentiation of M. nipponense. Thus, we isolated two candidate genes that may advance the studies of sex-determination mechanism in M. nipponense and even the whole crustacean species, as well as promoting the all-male population culture of M. nipponense. PMID:24809964

Jin, Shubo; Jiang, Sufei; Xiong, Yiwei; Qiao, Hui; Sun, Shengming; Zhang, Wenyi; Li, Fajun; Gong, Yongsheng; Fu, Hongtuo

2014-08-10

107

Contributions from the Amazon River mouth to the carbonate and nutrient dynamics of the tropical Atlantic Ocean (Invited)  

NASA Astrophysics Data System (ADS)

The Amazon River contributes considerable freshwater and dissolved constituents to the global ocean, and its low-salinity plume offshore significantly impacts the carbon and nutrient cycles of the western tropical North Atlantic Ocean. Viewing the river-plume-ocean system as a continuum, rather than a point source, is a key component of the ROCA / ANACONDAS project effort. Here we report the findings of a multi-season field effort in the lower reach of the Amazon mainstem and offshore plume to determine the concentrations and variability of the full carbonate system as well as dissolved inorganic nitrogen, phosphorus, and silica at the mouth, providing for the first time the critical "river end members" for the Amazon's contribution to the sea. We find that concentrations at the mouth differ significantly from measurements made upriver at Manaus and Óbidos, historically used to represent the Amazon's contribution. With these new end members, the impact of the plume on the tropical marine ecosystem can be better determined, including its role as a globally significant atmospheric carbon dioxide sink and its sensitivity to change. These data, in combination with other microbial and geochemical data from the Amazon River continuum, improve our understanding of the links between the river, the plume, and the tropical Atlantic carbon cycle, as well as improve predictive capabilities of future climate change impacts. True color satellite image of Amazon River plume - NASA pCO2 versus salinity for outer Amazon River plume with color bar showing chlorophyll a fluorescence. Line is linear regression through the data, not a mixing line.

Yager, P. L.; Richey, J. E.; Page, B. P.; Ward, N.; Krusche, A. V.; Weber, S.; Montoya, J. P.; Rezende, C. E.

2013-12-01

108

Simulating hydrologic and hydraulic processes throughout the Amazon River Basin  

USGS Publications Warehouse

Presented here is a model framework based on a land surface topography that can be represented with various degrees of resolution and capable of providing representative channel/floodplain hydraulic characteristics on a daily to hourly scale. The framework integrates two models: (1) a water balance model (WBM) for the vertical fluxes and stores of water in and through the canopy and soil layers based on the conservation of mass and energy, and (2) a routing model for the horizontal routing of surface and subsurface runoff and channel and floodplain waters based on kinematic and diffusion wave methodologies. The WBM is driven by satellite-derived precipitation (TRMM_3B42) and air temperature (MOD08_M3). The model's use of an irregular computational grid is intended to facilitate parallel processing for applications to continental and global scales. Results are presented for the Amazon Basin over the period Jan 2001 through Dec 2005. The model is shown to capture annual runoff totals, annual peaks, seasonal patterns, and daily fluctuations over a range of spatial scales (>1, 000 to <4D7M km2). For the period of study, results suggest basin-wide total water storage changes in the Amazon vary by approximately +/-5 to 10 cm, and the fractional components accounting for these changes are: root zone soil moisture (20%), subsurface water being routed laterally to channels (40%) and channel/floodplain discharge (40%). Annual variability in monthly water storage changes by +/-2.5 cm is likely due to 0D5 to 1 month variability in the arrival of significant rainfall periods throughout the basin. Copyright ?? 2009 John Wiley & Sons, Ltd.

Beighley, R. E.; Eggert, K. G.; Dunne, T.; He, Y.; Gummadi, V.; Verdin, K. L.

2009-01-01

109

Turbulent mixing in the Amazon River: The isotopic memory of confluences  

NASA Astrophysics Data System (ADS)

Rivers continuously discharge dissolved material to the oceans. Dissolved compounds partially result from water-rock interactions, which produce a large range of water chemical and isotopic compositions. These waters are collected by rivers, that are commonly assumed to be well-mixed with regard to their different tributaries, as a result of turbulent dispersion. In this paper, we test this hypothesis on the Solimões River (at Manacapuru), the largest tributary of the Amazon River, by analyzing the sodium concentration and strontium isotopic composition of river water on a transverse section at different depths. High-precision measurements reveal lateral heterogeneities. This reflects poor mixing between two main river masses, that have distinct chemical and isotopic signatures, a hundred kilometers downstream from their confluence: the Solimões mainstream and the Purús River. Using sodium concentration data, the transverse dispersion coefficient is estimated for the studied Solimões reach (the Earth's largest river on which such an estimate now exists), and is found to be 1.8 ± 0.2 m 2/s. Comparison with previously reported data highlights the potential role of bed morphology and islands in the efficiency of lateral mixing in large rivers. We finally demonstrate that the characteristic length of lateral mixing downstream from confluences in large rivers is at least of several tens of kilometers.

Bouchez, Julien; Lajeunesse, Eric; Gaillardet, Jérôme; France-Lanord, Christian; Dutra-Maia, Poliana; Maurice, Laurence

2010-02-01

110

Amazon River enhances diazotrophy and carbon sequestration in the tropical North Atlantic Ocean  

PubMed Central

The fresh water discharged by large rivers such as the Amazon is transported hundreds to thousands of kilometers away from the coast by surface plumes. The nutrients delivered by these river plumes contribute to enhanced primary production in the ocean, and the sinking flux of this new production results in carbon sequestration. Here, we report that the Amazon River plume supports N2 fixation far from the mouth and provides important pathways for sequestration of atmospheric CO2 in the western tropical North Atlantic (WTNA). We calculate that the sinking of carbon fixed by diazotrophs in the plume sequesters 1.7 Tmol of C annually, in addition to the sequestration of 0.6 Tmol of C yr?1 of the new production supported by NO3 delivered by the river. These processes revise our current understanding that the tropical North Atlantic is a source of 2.5 Tmol of C to the atmosphere [Mikaloff-Fletcher SE, et al. (2007) Inverse estimates of the oceanic sources and sinks of natural CO2 and the implied oceanic carbon transport. Global Biogeochem Cycles 21, doi:10.1029/2006GB002751]. The enhancement of N2 fixation and consequent C sequestration by tropical rivers appears to be a global phenomenon that is likely to be influenced by anthropogenic activity and climate change.

Subramaniam, A.; Yager, P. L.; Carpenter, E. J.; Mahaffey, C.; Bjorkman, K.; Cooley, S.; Kustka, A. B.; Montoya, J. P.; Sanudo-Wilhelmy, S. A.; Shipe, R.; Capone, D. G.

2008-01-01

111

Particulate organic matter distribution along the lower Amazon River: addressing aquatic ecology concepts using fatty acids.  

PubMed

One of the greatest challenges in understanding the Amazon basin functioning is to ascertain the role played by floodplains in the organic matter (OM) cycle, crucial for a large spectrum of ecological mechanisms. Fatty acids (FAs) were combined with environmental descriptors and analyzed through multivariate and spatial tools (asymmetric eigenvector maps, AEM and principal coordinates of neighbor matrices, PCNM). This challenge allowed investigating the distribution of suspended particulate organic matter (SPOM), in order to trace its seasonal origin and quality, along a 800 km section of the Amazon river-floodplain system. Statistical analysis confirmed that large amounts of saturated FAs (15:0, 18:0, 24:0, 25:0 and 26:0), an indication of refractory OM, were concomitantly recorded with high pCO(2) in rivers, during the high water season (HW). Contrastingly, FAs marker which may be attributed in this ecosystem to aquatic plants (18:2?6 and 18:3?3) and cyanobacteria (16:1?7), were correlated with higher O(2), chlorophyll a and pheopigments in floodplains, due to a high primary production during low waters (LW). Decreasing concentrations of unsaturated FAs, that characterize labile OM, were recorded during HW, from upstream to downstream. Furthermore, using PCNM and AEM spatial methods, FAs compositions of SPOM displayed an upstream-downstream gradient during HW, which was attributed to OM retention and the extent of flooded forest in floodplains. Discrimination of OM quality between the Amazon River and floodplains corroborate higher autotrophic production in the latter and transfer of OM to rivers at LW season. Together, these gradients demonstrate the validity of FAs as predictors of spatial and temporal changes in OM quality. These spatial and temporal trends are explained by 1) downstream change in landscape morphology as predicted by the River Continuum Concept; 2) enhanced primary production during LW when the water level decreased and its residence time increased as predicted by the Flood Pulse Concept. PMID:23029412

Mortillaro, Jean-Michel; Rigal, François; Rybarczyk, Hervé; Bernardes, Marcelo; Abril, Gwenaël; Meziane, Tarik

2012-01-01

112

Particulate Organic Matter Distribution along the Lower Amazon River: Addressing Aquatic Ecology Concepts Using Fatty Acids  

PubMed Central

One of the greatest challenges in understanding the Amazon basin functioning is to ascertain the role played by floodplains in the organic matter (OM) cycle, crucial for a large spectrum of ecological mechanisms. Fatty acids (FAs) were combined with environmental descriptors and analyzed through multivariate and spatial tools (asymmetric eigenvector maps, AEM and principal coordinates of neighbor matrices, PCNM). This challenge allowed investigating the distribution of suspended particulate organic matter (SPOM), in order to trace its seasonal origin and quality, along a 800 km section of the Amazon river-floodplain system. Statistical analysis confirmed that large amounts of saturated FAs (15:0, 18:0, 24:0, 25:0 and 26:0), an indication of refractory OM, were concomitantly recorded with high pCO2 in rivers, during the high water season (HW). Contrastingly, FAs marker which may be attributed in this ecosystem to aquatic plants (18:2?6 and 18:3?3) and cyanobacteria (16:1?7), were correlated with higher O2, chlorophyll a and pheopigments in floodplains, due to a high primary production during low waters (LW). Decreasing concentrations of unsaturated FAs, that characterize labile OM, were recorded during HW, from upstream to downstream. Furthermore, using PCNM and AEM spatial methods, FAs compositions of SPOM displayed an upstream-downstream gradient during HW, which was attributed to OM retention and the extent of flooded forest in floodplains. Discrimination of OM quality between the Amazon River and floodplains corroborate higher autotrophic production in the latter and transfer of OM to rivers at LW season. Together, these gradients demonstrate the validity of FAs as predictors of spatial and temporal changes in OM quality. These spatial and temporal trends are explained by 1) downstream change in landscape morphology as predicted by the River Continuum Concept; 2) enhanced primary production during LW when the water level decreased and its residence time increased as predicted by the Flood Pulse Concept.

Mortillaro, Jean-Michel; Rigal, Francois; Rybarczyk, Herve; Bernardes, Marcelo; Abril, Gwenael; Meziane, Tarik

2012-01-01

113

Estimating suspended sediment concentrations in surface waters of the Amazon River wetlands from Landsat images  

SciTech Connect

A method has been developed, based on spectral mixture analysis, to estimate the concentration of suspended sediment in surface waters of the Amazon River wetlands from Landsat MSS and TM images. Endmembers were derived from laboratory reflectance measurements of water-sediment mixtures with a range of sediment concentrations. Using these references spectra, the authors applied a linear mixture analysis to multispectral images after accounting for instrument and atmosphere gains and offsets. Sediment concentrations were estimated for individual pixels from the mixture analysis results based on a nonlinear calibration curve relating laboratory sediment concentrations and reflectance to endmember fractions. The uncertainty in the sediment concentrations derived from this analysis for three Amazon images is predicted to be within [plus minus] 20 mg/L, and the concentrations fall within a range of concentrations of suspended sediment that were measured at several times and places in the field over the past 15 years. The emphasis of their work is to use the patterns of sediment concentrations to compute the approximate volumes of sediment that are transferred between the main channel and floodplain of the Amazon River. However, the methodology can be applied universally if the optical properties of water and sediment at the site are known, and it is, therefore, useful for the study of suspended sediment concentrations in surface waters of wetlands elsewhere.

Mertes, L.A.K.; Smith, M.O.; Adams, J.B. (Univ. of Washington, Seattle (United States))

1993-03-01

114

15 N natural abundance in plants of the Amazon River floodplain and potential atmospheric N 2 fixation  

Microsoft Academic Search

Summary The15N natural abundance values of various Amazon floodplain (várzea) plants was investigated. Samples of young leaf tissues were collected during three different periods of the river hydrography (low water, mid rising water and high water) and during one period in the Madeira River (high water). A large variation of15N abundance was observed, both among the different plant types and

L. A. Martinelli; R. L. Victoria; P. C. O. Trivelin; A. H. Devol; J. E. Richey

1992-01-01

115

Fish assemblages of the Casiquiare River, a corridor and zoogeographical filter for dispersal between the Orinoco and Amazon basins  

Microsoft Academic Search

Aim The aim of this study was to determine whether the Casiquiare River functions as a free dispersal corridor or as a partial barrier (i.e. filter) for the interchange of fish species of the Orinoco and Negro\\/Amazon basins using species assemblage patterns according to geographical location and environmental features. Location The Casiquiare, Upper Orinoco and Upper Negro rivers in southern

Kirk O. Winemiller; Hernán López-Fernández; Donald C. Taphorn; Leo G. Nico; Aniello Barbarino Duque

2008-01-01

116

Phosphorus in sediments of the Amazon River and estuary: Implications for the global flux of phosphorus to the sea  

Microsoft Academic Search

The distribution of various forms of P in suspended and depositional bank sediments of the Amazon River and bottom sediments of the mixing and freshwater portions of the Amazon estuary and shelf have been determined using a modified sequential extraction method. Forms of P distinguished are: P associated with ferric oxides\\/hydroxides (Fe-P), organic P (org-P), P extracted with acetate buffer

Robert A. Berner; Ji-Long Rao

1994-01-01

117

The Late Miocene paleogeography of the Amazon Basin and the evolution of the Amazon River system  

Microsoft Academic Search

On the basis of paleontological content (vertebrates and palynology) and facies analysis from river banks, road cuts, and three wells, we have assigned the uppermost levels of the Solimões Formation in western Amazonia, Brazil, to the Late Miocene. The vertebrate fossil record from outcropping sediments is assigned to the Huayquerian–Mesopotamian mammalian biozones, spanning 9–6.5Ma. Additionally, we present results that demonstrate

Edgardo M. Latrubesse; Mario Cozzuol; Silane A. F. da Silva-Caminha; Catherine A. Rigsby; Maria Lucia Absy; Carlos Jaramillo

2010-01-01

118

The impacts of land use changes in the mercury flux in the Madeira River, Western Amazon.  

PubMed

Changes in hydrochemistry and Hg distribution in the Madeira River from Porto Velho to the confluence with the Amazon River were studied in two cruises in 1997 and 2002. Water conductivity was similar in both periods, but the pH was significantly higher in 2002, in particular along the middle reaches of the river. Total suspended matter concentrations also increased from 1997 to 2002 along the same river portion, which is a result of forest conversion to other land uses, in particular pastures and agriculture accelerated during the interval between the cruises. Dissolved Hg concentrations were similar along the river in both cruises, but particulate Hg concentrations increased significantly along the middle portion of the river, although the suspended matter from 2002 was relatively poorer in Hg compared to that from 1997. Since particulate Hg represents more than 90% of the total Hg present in the river water, there was a significant increase in the total Hg transport in the Madeira River. Although gold mining has nearly ceased to exist in the region, the remobilization of Hg from forest soils through conversion to other land uses is responsible for maintaining relatively high Hg content in the Madeira River environment. PMID:22441596

Lacerda, Luiz D; Bastos, Wanderley R; Almeida, Marcelo D

2012-03-01

119

Methane flux from the Amazon River floodplain - Emissions during rising water  

NASA Technical Reports Server (NTRS)

Methane flux data obtained during a period of high and falling water level in the course of the dry season of 1985 (the Amazon Boundary Layer Experiment, ABLE 2A) and a period of moderate and rising water during the wet season of 1987 (ABLE 2B) were used to characterize the influence of seasonal variations in the vegetation, water column depth, and chemistry, as well as atmospheric dynamics, on the methane flux from the Amazon River floodplain. It was found that the annual estimate of methane from wetlands is identical to the annual estimate made by Matthews and Fung (1987) (both at 111 Tg). However, it was found that peatlands between 50 and 70 N contribute 39 Tg, with the large areas of forested and nonforested bogs making up 37 Tg of this figure, while the figures of Matthews and Fung were 63 and 62 Tg, respectively.

Bartlett, Karen B.; Crill, Patrick M.; Bonassi, Jose A.; Richey, Jeffrey E.; Harriss, Robert C.

1990-01-01

120

Methane flux from the Amazon River floodplain - Emissions during rising water  

NASA Astrophysics Data System (ADS)

Methane flux data obtained during a period of high and falling water level in the course of the dry season of 1985 (the Amazon Boundary Layer Experiment, ABLE 2A) and a period of moderate and rising water during the wet season of 1987 (ABLE 2B) were used to characterize the influence of seasonal variations in the vegetation, water column depth, and chemistry, as well as atmospheric dynamics, on the methane flux from the Amazon River floodplain. It was found that the annual estimate of methane from wetlands is identical to the annual estimate made by Matthews and Fung (1987) (both at 111 Tg). However, it was found that peatlands between 50 and 70 N contribute 39 Tg, with the large areas of forested and nonforested bogs making up 37 Tg of this figure, while the figures of Matthews and Fung were 63 and 62 Tg, respectively.

Bartlett, Karen B.; Crill, Patrick M.; Bonassi, Jose A.; Richey, Jeffrey E.; Harriss, Robert C.

1990-09-01

121

Seasonal uranium distributions in the coastal waters off the Amazon and Mississippi Rivers  

USGS Publications Warehouse

The chemical reactivity of uranium was investigated across estuarine gradients from two of the world's largest river systems: the Amazon and Mississippi. Concentrations of dissolved (<0.45 ??m) uranium (U) were measured in surface waters of the Amazon shelf during rising (March 1990), flood (June 1990) and low (November 1991) discharge regimes. The dissolved U content was also examined in surface waters collected across estuarine gradients of the Mississippi outflow region during April 1992, August 1993, and November (1993). All water samples were analyzed for U by isotope dilution inductively coupled plasma mass spectrometry (ICP-MS). In Amazon shelf surface waters uranium increased nonconservatively from about 0.01 ??g l-1 at the river's mouth to over 3 ??g l-1 at the distal site, irrespective of river discharge stage. Observed large-scale U removal at salinities generally less than 15 implies a) that riverine dissolved U was extensively adsorbed by freshly-precipitated hydrous metal oxides (e.g., FeOOH, MnO2) as a result of flocculation and aggregation, and b) that energetic resuspension and reworking of shelf sediments and fluid muds on the Amazon shelf released a chemically reactive particle/colloid to the water column which can further scavenge dissolved U across much of the estuarine gradient. In contrast, the estuarine chemistry of U is inconclusive within surface waters of the Mississippi shelf-break region. U behavior is most likely controlled less by traditional sorption and/or desorption reactions involving metal oxides or colloids than by the river's variable discharge regime (e.g., water parcel residence time during estuarine mixing, nature of particulates, sediment storage and resuspension in the confined lower river), and plume dispersal. Mixing of the thin freshwater lens into ambient seawater is largely defined by wind-driven rather than physical processes. As a consequence, in the Mississippi outflow region uranium predominantly displays ConserVative behavior; removal is evident only during anomalous river discharge regimes. 'Products-approach' mixing experiments conducted during the Flood of 1993 suggest the importance of small particles and/or colloids in defining a depleted U versus salinity distribution.

Swarzenski, P. W.; McKee, B. A.

1998-01-01

122

Dynamics of sediment transport in large tropical tidal rivers via observations in the Mekong and Amazon  

NASA Astrophysics Data System (ADS)

Of the ten largest-discharge river systems worldwide, freshwater delivery to the ocean from tropical rivers comprises approximately 72% of the total. Tropical-river suspended-sediment loads make up about 45% of the total among the same ten largest rivers. In this context, flow and sediment dynamics of tropical river systems are crucial to a comprehensive understanding of global river budgets. The processes by which sediment is eroded, transported, trapped, and ultimately exported from tidal rivers--where tides propagate but oceanic salinity is absent or only ephemerally present--are poorly understood, even though previous research suggests up to one-third of riverine sediment loads may be trapped within tidal rivers. In an effort to better understand these processes, we present and contrast results from several campaigns along two large tropical tidal rivers: the Mekong and Amazon. Under conditions of high and low seasonal discharge, three cross-sections within the Mekong tidal river were each occupied for a 25-hour tidal cycle, during which ADCP and CTD transects were completed every 15-30 minutes. In this transitional environment between fluvial and estuarine conditions, flow reversed throughout the water column during both low and high flow at all locations, and a strongly sheared flow was present during lesser flood tides. Salinity was spatially variable over seasons: during low flow, salinity in excess of 10 PSU was observed 30 km upstream during maximum flood, while at the same location during high flow, salinity was less than 0.5 PSU at all times. Conditions were partially stratified during low flow. When present, stratification was in the form of a salt wedge during high flow. Suspended sediment was well mixed or exhibited a Rouse-like profile in fresh regions; suspended-sediment concentration within the salt wedge was generally less, except during periods of strong near-bottom flow within the salt-wedge water mass. During both seasons and at all locations, distinct, preferential pathways of water and sediment within the cross-sections were present through the tidal cycles, which may foster development of the rapidly prograding islands within the tidal river. Data collected from seasonal cruises along the geographically vast Amazon tidal river provide context for more spatially constrained studies on the Mekong tidal river and highlight the contrasts between these two large tropical river systems. Ongoing work in these two systems provides a basis for improved understanding of sediment-transport processes within the tidal reach and ultimate quantity, timing, and character of sediment delivered to the ocean.

Nowacki, D. J.; Ogston, A. S.; Nittrouer, C. A.; Fricke, A. T.; Van, P.; Souza Filho, P. W.; Silva, M. S.

2013-12-01

123

Simulation of absolute water surface elevations in a global river model: a case study in the Amazon River  

NASA Astrophysics Data System (ADS)

Water level dynamics in continental-scale rivers is an important factor for surface water studies and flood hazard management. However, most continental-scale river models have not focused on the reproduction of water level because the storage and movement of surface waters are regulated by smaller scale topography than their grid resolutions. Here we analyzed the water level dynamics simulated by a state- of-the-art global river model, CaMa-Flood, with sub-grid representation of floodplain topography. As a case study, hydrodynamics simulation in the Amazon River was accomplished, and the simulated water surface elevations along the mainstem were compared against Envisat altimetry. The seasonal cycle of the simulated water surface elevations are in agreement with the altimetry (correlation coefficient >0.69, annual amplitude error <1.6 m). The accuracy of absolute water surface elevations was also good (averaged RMSE of 1.83 m), and the associated errors were within the range of the model uncertainty due to channel cross-section parameters. Then, the ocean tide variation at river mouth was incorporated for simulating the tidal effect in the inland Amazon basin, which requires realistic representation of absolute water surface elevations. By applying power-spectra analysis to the simulated water level variations, the 15-day cycle due to spring and neap tides was detected at Obidos located 800 km upstream from the river mouth. The reproduction of the ocean tide propagation to the inland region suggests that CaMa-Flood includes the main physical processes needed to accurately simulate the water level dynamics in continental-scale rivers.

Yamazaki, Dai; Lee, Hyongki; Alsdorf, Doug; Dutra, Emanuel; Kim, Hyungjun; Kanae, Shinjiro; Oki, Taikan; Bates, Paul

2013-04-01

124

Pathways of clay mineral transport in the coastal zone of the Brazilian continental shelf from Ceará to the mouth of the Amazon River  

NASA Astrophysics Data System (ADS)

The transport pathways of fine sediments (fraction <2 ?m) along the Brazilian continental shelf from Ceará to the Amazon River mouth were studied by means of clay mineral analyses. On the continental shelf southeast of the Amazon mouth, fluctuations in clay mineral compositions reflect simple mixing between the suspended load of the North Brazil Current and sediment from several smaller rivers. Previously, clay mineral variations west of the Amazon mouth have been explained by variable settling velocities of different grain-size classes within the <2 ?m fraction or by selective coagulation of individual clay mineral groups. By contrast, our experiments with river bank samples show that selective coagulation does not occur in Amazon River sediments. A more appropriate explanation for observed variations in clay mineral composition off the Amazon mouth seems to be, similarly to that for the shelf between Ceará and the Amazon mouth, a mixing of Amazon sediments with suspended material of the North Brazil Current. This interpretation is supported by data on clay mineral composition east and south of the Amazon mouth, showing more affinity to sediments of the North Brazil Current than to the suspended load of the Amazon River. Additionally, relatively low sedimentation rates and low concentrations of fine-grained sediments on the shelf suggest that high riverine input by the Amazon River does not overprint the sediments of the North Brazil Current in this region. The strong North Brazil Current shunts the Amazon suspended load in a north-westerly direction along the north-eastern coast of South America. Hence, stronger sedimentation of Amazon sediments would occur only west of the river mouth.

de Morais, J. O.; Tintelnot, M.; Irion, G.; Souza Pinheiro, L.

2006-03-01

125

Estimating Water Slope in Amazon River Tributaries Using the Shuttle Radar Topography Mission Digital Elevation Model  

NASA Astrophysics Data System (ADS)

Extracting river height from the Shuttle Radar Topography Mission digital elevation model (SRTM DEM) for four Amazon River tributaries found water surface elevation standard deviations of 6.16 m for the Madeira River, 7.47 m for the Purus River, 5.28 m for the Negro River, and 5.35 m for the Branco River. Standard deviations and slopes were found for the Madeira, Purus, and Branco rivers by fitting a simple, straight line to the SRTM heights with ~1000 km of flow distance. A second order polynomial was used for the Negro River. Resulting water surface slopes are 3.63 cm/km for the Madeira, 2.83 cm/km for the Purus, and 6.95 cm/km for the Branco whereas a range in slope from 7.00 to 2.10 cm/km was found for the Negro. Using a conservative, annual minimum water slope estimate of 2 cm/km for each tributary leads to reach length requirements of 616 km for the Madiera, 747 km for the Purus, 528 km for the Negro, and 535 km for the Branco to clearly delineate slope. The Global Rain Forest Mapping project's synthetic aperture radar mosaics (GRFM SAR) provide river width. Channel width is computed at each GRFM SAR pixel along a center line obtained by thresholding the Laplacian of an image containing the distance from each channel pixel to the nearest bank pixel. For the Purus River a depth estimate of 15 m and a Manning's n of 0.03 are assumed in calculating river flow velocities using Manning's equation. Using the estimated velocity of 1.04 m/s, the calculated Purus River discharge is 8500 m3/s. state.edu/water/

Hamski, J.; Lefavour, G.; Alsdorf, D.; Pavelsky, T.

2006-12-01

126

Phosphorus in sediments of the Amazon River and the global flux of P to the sea  

SciTech Connect

A modification of the sequential extraction method of Ruttenberg (1990), for the determination of various forms of phosphorus in soils and sediments, has been applied to suspended and bank sediments of the Amazon River and river-derived marine bottom muds of the Amazon shelf. The following forms of phosphate are distinguished: P associated with hydrous ferric oxides (Fe-P), organic P (org-P), detrital apatite (detr-P), authigenic and/or biogenic Ca-phosphates (auth-P), and total phosphorus. (Use of H[sub 2]O[sub 2] to determine org-P results in loss of phosphorus which renders it inferior to the Aspila or difference-by-ignition method). Results indicate that: (1) org-P drops as riverine sediments become deposited in the marine environment; (2) org-P and Fe-P both drop as sediment is deposited on river banks and subjected to plant growth; (3) detr-P anticorrelates with Fe-P due probably to the association of detr-P with coarser size fractions combined with the correlation of increased Fe-oxide content with finer size fractions; (4) auth-P undergoes negligible change between riverine and marine environments; (5) total P in marine sediments is distinctly lower than that in suspended sediment of the river. These results suggest that dissolved phosphorus is added to the oceans by rivers via the bacterial decomposition of river-transported organic matter and possibly by the desorption and possibly by the desorption of P from Fe-oxides, in addition to that carried in solution. If these results can be extrapolated to a global basis, presently used residence times for phosphate in seawater are too high.

Rao, Ji Long; Berner, R.A. (Yale Univ., New Haven, CT (United States). Dept. of Geology and Geophysics)

1992-01-01

127

Study of the anabranch dynamics for different sinuosity stages in the Upper Amazon River Basin  

NASA Astrophysics Data System (ADS)

The Upper Peruvian Amazon River is characterized by a sequence of anabranching structures, which are composed by several channels behaving as non-developed and quasy-freely meandering channels. The widest channel in these anabranching structures is considered as the main channel or main anabranch while the other channels are secondary anabranches. Based on satellite imagery, it is observed that the main channels show different sinuosities along the Upper Peruvian Amazon River valley. Little is known about the effects of the planform characteristics of the main channel into the morphodynamics of the secondary anabranches. Thus, two study sites were selected to characterize anabranching structures with low and medium-high sinuosity main channels. For the low sinuosity main channel case, an area at the tri-point boundary between Colombia-Brazil and Peru was selected. For the medium-high sinuosity main channel case, an area upstream of Iquitos City (the largest city in the Peruvian Amazon Rainforest) was selected. A field campaign was carried out on 2010 and 2011 for the medium-high and low sinuosity stages respectively. On this field campaign velocity measurement, bathymetry and water surface elevations were obtained. With the field data it was possible to develop and validate a two dimensional shallow water numerical model to study the hydrodynamics on both sites. This allows us to discuss the effects of the current planform configuration of the anabranching structures into the short-term behavior of individual channels. In past studies, temporal analysis of the Amazon River planform have been carried out using satellite imagery with special focus into the floodplain, main channel, number of islands and valley slope. However, the dynamics in these anabranching structures containing multiple channels have not been studied in detailed. The metrics obtained for this study were sinuosity, channel width and annual migration rates. It was confirmed that in a medium to high sinuosity stage, the secondary anabranches behave as non-developed meanders. Also, it was concluded that the planform for secondary anabranches in all main channel sinuosity stages are controlled by the main anabranch migration.

Frias, C. E.; Mendoza, A.; Dauer, K.; Abad, J. D.; Montoro, H.; Paredes, J.; Vizcarra, J.

2013-12-01

128

Mercury pollution in the Tapajos River basin, Amazon: mercury level of head hair and health effects.  

PubMed

There is increasing concern about the potential neurotoxic effects of exposure to methylmercury for the 6 million people living in the Amazon, even in regions situated far away from the gold mines (garimpos), considered to be the major source of mercury pollution. In November 1998, a spot investigation on mercury contamination was conducted in three fishing villages (Barreiras, Rainha, and Sao Luiz do Tapajos) on the Tapajos River, an effluent of the Amazon, situated several hundred kilometers downstream from the gold-mining areas. A total of 132 fishermen and their families volunteered for the current study. As was anticipated, the total mercury levels in the head hair collected from the fishing villages were relatively high (14.1-20.8 ppm on the average) and the number of subjects with a high total mercury level over 10 ppm (the least upper bound of a normal value) was 103 (78.0%) in total, along with various symptoms, thereby suggesting wide mercury contamination in the Tapajos River basin. Moreover, in view of the absence of other diseases (e.g., alcoholism or malaria), a high intake of fish containing a methylmercury level, and high hair mercury levels in addition to the various symptoms such as sensory disturbance (especially glove-and-stocking type, which is characteristic of Minamata disease), tremor, failure in two-point discrimination, and slight balancing failure, several subjects examined were diagnosed with mild Minamata disease. The findings obtained suggest, thus, that the mercury pollution in the Amazon should be crucially observed for head hair mercury level and health in a much broader region. PMID:11686639

Harada, M; Nakanishi, J; Yasoda, E; Pinheiro, M C; Oikawa, T; de Assis Guimarâes, G; da Silva Cardoso, B; Kizaki, T; Ohno, H

2001-10-01

129

The pathways and properties of the Amazon River Plume in the tropical North Atlantic Ocean  

NASA Astrophysics Data System (ADS)

The Amazon River Plume spreads across the tropical North Atlantic creating a barrier to vertical mixing. Here using a 1/6° HYCOM model and data from three research cruises in May-June 2010, September-October 2011, and July 2012, we investigate the pathways and properties of the plume. Four plume pathways for export of freshwater from the western tropical North Atlantic are identified. These consist of direct and indirect pathways to the northwest, and eastward pathways toward the subtropical gyre and toward Africa in the North Equatorial Counter Current. Because of the seasonality and cooccurrence of these pathways, plume characteristics are highly variable. Two pathways export water to the Caribbean, however the time scales associated with those direct and indirect pathways (3 versus 6+ months) differ, leading to different salinity characteristics of the plume water. Models results show that the Amazon river and tropical precipitation have similar magnitude impact on the observed seasonal cycle of freshwater within the western tropical Atlantic and at the 8°N, 38°W PIRATA mooring. Freshwater associated with the Amazon also influences surface salinity in winter as far as 20W in the model. The mean plume salinity minimum leads maximum discharge, highlighting the importance of currents and advection rather than discharge in maintaining plume properties. Plume pathways are tied to the underlying current structure, with the North Equatorial Counter Current jet preventing direct freshwater transport into the southern hemisphere. The plume influences underlying currents as well, generating vertical current shear that leads to enhanced eddy stirring and mixing in the model simulations.

Coles, Victoria J.; Brooks, Maureen T.; Hopkins, Julia; Stukel, Michael R.; Yager, Patricia L.; Hood, Raleigh R.

2013-12-01

130

Integrating GRACE measured water storage change observations into the Hillslope River Routing (HRR) in the Amazon and Congo River Basins  

NASA Astrophysics Data System (ADS)

In this study, GRACE measured water storages are used to constrain the Hillslope River Routing (HRR) model in the Amazon and Congo River Basins. The GRACE measured water storages change observations are de-correlated, filtered and signal leakage corrected with an approximate spatial resolution of longer than 200 km (half-wavelength). The HRR model provides similar scale total water storage changes by integrating vertical water balance, lateral surface and subsurface kinematic wave routing, and channel plus floodplain diffusion wave routing models. The period of study is 2003 through 2008. The model forcing data are TRMM precipitation and MODIS air temperature, albedo, cloud cover and leaf area index. The HRR model parameters accounting for the thickness of the rooting zone layer, timing of the subsurface response to the channel network and speed of the flood wave are calibrated using the GRACE estimates of water storage change. The resulting model predictions are compared to corresponding streamflow data in the Amazon Basin and historical flow data in the Congo Basin. The results of this study quantify the predictive capabilities of a large scale hydrologic model driven primarily with Satellite data and without calibrating to in-situ streamflow data.

Beighley, R. E.; He, Y.; Ray, R. L.; Guo, J.; Shum, C.

2009-12-01

131

Metagenomics of the water column in the pristine upper course of the Amazon river.  

PubMed

River water is a small percentage of the total freshwater on Earth but represents an essential resource for mankind. Microbes in rivers perform essential ecosystem roles including the mineralization of significant quantities of organic matter originating from terrestrial habitats. The Amazon river in particular is famous for its size and importance in the mobilization of both water and carbon out of its enormous basin. Here we present the first metagenomic study on the microbiota of this river. It presents many features in common with the other freshwater metagenome available (Lake Gatun in Panama) and much less similarity with marine samples. Among the microbial taxa found, the cosmopolitan freshwater acI lineage of the actinobacteria was clearly dominant. Group I Crenarchaea and the freshwater sister group of the marine SAR11 clade, LD12, were found alongside more exclusive and well known freshwater taxa such as Polynucleobacter. A metabolism-centric analysis revealed a disproportionate representation of pathways involved in heterotrophic carbon processing, as compared to those found in marine samples. In particular, these river microbes appear to be specialized in taking up and mineralizing allochthonous carbon derived from plant material. PMID:21915244

Ghai, Rohit; Rodriguez-Valera, Francisco; McMahon, Katherine D; Toyama, Danyelle; Rinke, Raquel; Cristina Souza de Oliveira, Tereza; Wagner Garcia, José; Pellon de Miranda, Fernando; Henrique-Silva, Flavio

2011-01-01

132

Metagenomics of the Water Column in the Pristine Upper Course of the Amazon River  

PubMed Central

River water is a small percentage of the total freshwater on Earth but represents an essential resource for mankind. Microbes in rivers perform essential ecosystem roles including the mineralization of significant quantities of organic matter originating from terrestrial habitats. The Amazon river in particular is famous for its size and importance in the mobilization of both water and carbon out of its enormous basin. Here we present the first metagenomic study on the microbiota of this river. It presents many features in common with the other freshwater metagenome available (Lake Gatun in Panama) and much less similarity with marine samples. Among the microbial taxa found, the cosmopolitan freshwater acI lineage of the actinobacteria was clearly dominant. Group I Crenarchaea and the freshwater sister group of the marine SAR11 clade, LD12, were found alongside more exclusive and well known freshwater taxa such as Polynucleobacter. A metabolism-centric analysis revealed a disproportionate representation of pathways involved in heterotrophic carbon processing, as compared to those found in marine samples. In particular, these river microbes appear to be specialized in taking up and mineralizing allochthonous carbon derived from plant material.

McMahon, Katherine D.; Toyama, Danyelle; Rinke, Raquel; Cristina Souza de Oliveira, Tereza; Wagner Garcia, Jose; Pellon de Miranda, Fernando; Henrique-Silva, Flavio

2011-01-01

133

Fish contamination and human exposure to mercury in Tartarugalzinho River, Amapa State, Northern Amazon, Brazil. A screening approach  

Microsoft Academic Search

This study reports for the first time, the Hg concentrations in the fish fauna of the Tartarugalzinho river basin - an important gold mining region in Amapa State, Northern Amazon - and evaluates human exposure to Hg due to fish consumption in the area. We analyzed 16 fish species (carnivorous and omnivorous) common in the aquatic environment of the Tartarugalzinho

E. D. Bidone; Z. C. Castilhos; T. J. S. Santos; T. M. C. Souza; L. D. Lacerda

1997-01-01

134

ASSESSMENT OF THE SENSORS MODIS\\/TERRA AND WFI\\/CBERS-2 FOR THE AMAZON RIVER SUSPENDED SEDIMENT MONITORING  

Microsoft Academic Search

Suspended sediment load plays an important role in coastal processes. They can be used as a proxy for water quality variables such as turbidity, pollution and primary production. The large spatial and temporal variability of coastal environments, e.g. Amazon River mouth, makes it difficult the acquisition of spatially meaningful in situ data on suspended sediments. To overcome that problem the

G. S. F. Molleri; E. M. L. M. Novo; M. Kampel; L. M. G. Fonsecaa

135

Origins and processing of organic matter in the Amazon River as indicated by carbohydrates and amino acids  

Microsoft Academic Search

Aldose, amino acid, and elemental compositions were determined for flux-weighted samples of coarse (> 63 pm) and fine (< 63 pm) particulate organic material and ultrafiltered (> 1,000 Daltons) dissolved organic matter collected at three sites along the Brazilian Amazon River and six of its major tributaries. Concentrations of total organic C (TOC) were relatively uniform (55Ok 100 PM) at

JOHN I. HEDGES; GREGORY L. COWIE; JEFFREY E. RICHEY; PAUL D. QUAY; RONALD BENNER; MIKE STROM; BRUCE R. FORSBERG

1994-01-01

136

The influence of the Amazonian floodplain ecosystems on the trace element dynamics of the Amazon River mainstem (Brazil).  

PubMed

The purpose of this paper is to forecast the role of riverine wetlands in the transfer of trace elements. One of the largest riverine wetlands in the world is the floodplain (várzea) of the Amazon River and its tributaries (Junk and Piedade, 1997). The central Amazon wetlands are constituted by a complex network of lakes and floodplains, named várzeas, that extend over more than 300,000 km2 (Junk, W.J., The Amazon floodplain--a sink or source for organic carbon? In Transport of Carbon and Minerals in Major World Rivers, edited by E.T. Degens, S. Kempe, R. Herrera, SCOPE/UNEP; 267-283, 1985.) and are among the most productive ecosystems in the world due to the regular enrichment in nutrients by river waters In order to understand if the adjacent floodplain of Amazon River have a significant influence on the trace element concentrations and fluxes of the mainstem, the concentrations of selected elements (i.e., Al, Mn, Fe, Co, Cu, Mo, Rb, Sr, Ba, and U) have been measured in the Amazon River water (Manacapuru Station, Amazonas State, Brazil) and in lake waters and plants (leaves) from a várzea(Ilha de Marchantaria, Amazonas State, Brazil) during different periods of the hydrological cycle. Four plant species (two perennial species: Pseudobombax munguba and Salix humboldtiana, and two annual herbaceous plants: Echinochloa polystachya and Eichhornia crassipes) were selected to represent the ecological functioning of the site. Time series obtained for dissolved Mn and Cu (<0.20 microm) in Amazon River water could not be explained by tributary mixing or instream processes only. Therefore, the contribution of the waters transiting the floodplains should be considered. These results suggest that the chemical composition of the waters draining these floodplains is controlled by reactions occurring at sediment-water and plant-water interfaces. Trace elements concentrations in the plants (leaves) vary strongly with hydrological seasonality. Based on the concentration data and the biological productivity of floodplain ecosystems, a first order approximation of trace element storage (permanent or temporary) in the vegetation of these floodplains was made. It was found that floodplain-mainstem elemental fluxes make a significant contribution to the dissolved flux of the Amazon River. This study is part of the Brazilian_French joint research program Hybam (Hydrology and Geochemistry of the Amazonian Basin). PMID:15740771

Viers, Jérôme; Barroux, Guénaël; Pinelli, Marcello; Seyler, Patrick; Oliva, Priscia; Dupré, Bernard; Boaventura, Geraldo Resende

2005-03-01

137

Sr and Nd isotopes of suspended sediments from rivers of the Amazon basin  

NASA Astrophysics Data System (ADS)

The Rb-Sr and Sm-Nd isotopic systems are important tools to constrain the provenance of sediment load in river systems. This study presents the isotopic composition of Sr and Nd isotopes and major and minor elements in suspended sediments from the Marañón-Solimões, Amazonas and Beni-Madeira rivers. The data were used to constrain the source region of the sediments and to better understand the main seasonal and spatial transport processes within the basin based on the variations of the chemical and isotopic signals. They also allow establishing a relationship between sediment concentrations and flow rate values. The study presents data collected during a hydrological year between 2009 and 2010. The Marañón-Solimões River presents low Sr isotopic values (0.7090-0.7186), broad EpslonNd(0) range (-15.17 to -8.09) and Nd model (TDM) ages varying from 0.99 to 1.81 Ga. Sources of sediments to the Marañón-Solimões River include recent volcanic rocks in northern Peru and Ecuador, as well as rocks with long crustal residence time and carbonates from the Marañón Basin, Peru. The Beni-Madeira River has more radiogenic Sr isotope values (0.7255-0.7403), more negative EpslonNd(0) values (-20.46 to -10.47), and older Nd isotope model ages (from 1.40 to 2.35 Ga) when compared to the Marañón-Solimões River. These isotope data were related to the erosion of Paleozoic and Cenozoic foreland basins that are filled with Precambrian sediments derived from the Amazonian Craton. These basins are located in Bolivian Subandina Zone. The Amazon River presents intermediate isotopic values when compared to those found in the Marañón-Solimões and Beni-Madeira rivers. Its Sr isotope ratios range between 0.7193 and 0.7290, and its EpslonNd(0) values varies between -11.09 and -9.51. The Nd isotope model ages of the suspended sediments vary between 1.28 and 1.77 Ga. Concentrations of soluble and insoluble elements indicate a more intense weathering activity in sediments of the Beni-Madeira River. This river has a larger difference in the Sr isotopic composition between the diluted and solid phases, which has been assigned to the high level of weathering of its sediment source area. In the Beni-Madeira River sub-basin dominates weathering of silicate rocks, while in the Marañón-Solimões River sub-basin there also weathering of carbonate and evaporitic rocks.

Hatting, Karina; Santos, Roberto V.; Sondag, Francis

2014-05-01

138

Altimetric profiles of Amazon rivers and gage levels gained by GPS-PPP  

NASA Astrophysics Data System (ADS)

A key application of GNSS data for hydrology is the characterization of river altimetric profiles, including the levelling of gauges. In the present work we use the GINS-PC software developed at CNES/GRGS to determine thousands of kilometers long altimetric profile along the major rivers of the Amazon basin. The profiles are processed using data obtained from GPS receivers installed on board boats. We present the capability of the PPP kinematic with integer ambiguities fixing strategy implemented in GINS-PC in processing GPS data collected with moving stations. We point on the specific corrections and cautions that are necessary during the data collection and the data processing. The accuracy of the profiles is evaluated by comparing the results with fix points at gauge stations, or by comparing solutions obtained for several stations installed on the same boat Base applications of the method are to enable the leveling of 1- remote gages without any specific field work but initial installation of GPS stations on boats cruising the river network and 2- leveling of cross sections for the determination of the riverbed slope. Examples are presented with accuracy assessment. These profiles are further used to assess the capability of other space technics to provide altimetric profiles of rivers, namely DEMs such as SRTM, ACE2 or ASTER in the one hand and radar altimetry (JASON-2, ENVISAT) in the other hand.

Moreira, D. M.; Calmant, S.; Perosanz, F.; Rotunno Filho, O. C.; Santos, A.; Seyler, F.; Bonnet, M.; Gennero, M.; Monteiro, A. E.

2013-12-01

139

Prawn postlarvae fishing in coastal Bangladesh: Challenges for sustainable livelihoods  

Microsoft Academic Search

Fishing for prawn (Macrobrachium rosenbergii) postlarvae is a major contributor to the livelihoods of the coastal poor in Bangladesh, including women. A study of coastal livelihoods along the lower Pasur River in southwest Bangladesh indicates that on average 40% of total annual income comes from postlarvae fishing during the few months involved. However, indiscriminate fishing of wild postlarvae, with high

Nesar Ahmed; Max Troell; Edward H. Allison; James F. Muir

2010-01-01

140

The effects of CO2 on phytoplankton community structure in the Amazon River Plume  

NASA Astrophysics Data System (ADS)

The Amazon River Plume results from an enormous discharge of freshwater and organic matter into the Atlantic Ocean. It is a unique environment with a natural pCO2 gradient in the surface waters of the plume that range from 130-950 ?atm. The response of coastal marine phytoplankton to increased anthropogenic CO2 emission is still unknown, hence the Amazon River Plume gradient can serve as a natural laboratory to examine the potential influence of atmospheric CO2 increases and ocean acidification on phytoplankton community composition. A two pronged study was undertaken: the first in which shipboard samples from a 2010 cruise to the Amazon River Plume were analyzed to examine the distribution of 3 major phytoplankton groups (diatoms, diatom-diazotroph associations [DDAs], and the diazotroph Trichodesmium spp.) with respect to the natural pCO2 gradient; the second in which the growth response of Thalassiosira weisflogii, a representative diatom species, was examined under experimentally manipulated CO2 conditions. Cruise data analysis showed that diatoms were found with higher cell counts around 150 ?atm; DDAs seemed to dominate waters within the narrow range of 350-400 ?atm CO2; and the diazotroph Trichodesmium spp. grew in a wide range of pCO2 conditions, but with higher cell counts at upwards of 500 ?atm. Phytoplankton group distributions along the CO2 gradient may be due to differences in their carbon-concentrating mechanism (CCMs) efficiencies. The CO2 manipulation apparatus was assembled such that the cells were grown under three different CO2 environments. Differential growth of T. weisflogii was observed at 150, 400, and 800 ppm CO2 treatment. T. weisflogii grew at all three CO2 concentrations, reflecting diatoms' physiological flexibility and efficient CCMs. Absorption spectra analysis of pigments and Fast Repetition Rate Fluorometer analysis indicate potential changes in photosynthetic machinery with different CO2 treatments. Future CO2 manipulation experiments on representative DDA and diazotroph species will be undertaken to compare the growth responses of the 3 major phytoplankton groups to changes in CO2. Additionally, analysis on fatty acid compositions with different CO2 treatments will be done to assess potential changes in nutritive value for higher trophic levels. Underway pCO2 measurements with overlaid cell counts from the 2010 cruise data CO2 manipulation experiment data- growth curve (in vivo chlorophyll a fluorescence) for the 3 CO2 treatments

Chen, T. L.; Goes, J. I.; Gomes, H. R.; McKee, K. T.

2013-12-01

141

A Mineralogical and Organic Geochemical Overview of the Effects of Holocene Changes in Amazon River Flow on Floodplain Lakes  

NASA Astrophysics Data System (ADS)

A synthesis of the impacts of the Amazon River hydrological changes on the sedimentation process of organic matter (OM) in three different floodplain lakes (Santa Ninha, Maracá, and Comprido lakes) is presented in this study. Today the Santa Ninha and Maracá lakes are directly and permanently connected with the main channel of the Amazon River, in contrast to Comprido Lake, which is indirectly and periodically influenced by the Amazon River due to its high distance from the main channel. All the sedimentary lake records showed a reduced river inflow due to dry climatic conditions during the Early and Middle Holocene followed by a humid Late Holocene with an increased fluvial input. In Santa Ninha and Maraca Lakes the reduced river inflow period was characterized by sediments with a low abundance of smectite (on average ~20 wt. %), a clay mineral mainly transported by the fluvial system, high total organic carbon (TOC) contents (on average ~8.2 wt. %) and a predominant acidic soil OM input evidenced by high branched glycerol dialkyl glycerol tetraethers (GDGT) concentrations (on average 180 ?g gTOC-1). During the Late Holocene, a higher smectite abundance (on average ~43 wt. %) and a low TOC content (on average ~1.4 wt. %) pointed to dilution with the riverine lithogenic matter. This was accompanied by a proportional increase in the aquatically-produced crenarchaeol, suggesting an increased lake water level. In Comprido Lake, a sedimentation gap occurred during the Early and Middle Holocene. The humid Late Holocene, after 3,000 cal years BP, was characterized by high TOC values (on average ~9 wt. %) as well as a sharp increase in soil OM input as revealed by the increase in branched GDGT concentrations (on average ~81 ?g gTOC-1), but the smectite content was low (on average ~14 %). This suggests that in Comprido Lake the soil OM input from the local catchment area was predominant during the humid Late Holocene due to its high distance from the Amazon River main stem. Consequently, our study shows that the sedimentation processes of OM in Amazonian floodplain lakes are strongly influenced by variations in the hydrodynamic regime of the Amazon River during the Holocene. However, its impacts on floodplain lakes were different, mainly depending on the distance from the main stem of the Amazon River.

Moreira, Luciane; Patricia, Moreira-Turcq; Kim, Jung-Hyun; Turcq, Bruno; Renato, Cordeiro; Sandrine, Caquineau; Sinninghe Damsté, Jaap

2014-05-01

142

[Prevalence of arterial hypertension in communities along the Madeira River, Western Brazilian Amazon].  

PubMed

The aim of this cross-sectional study was to estimate the prevalence of hypertension among adults (n = 841) in communities along the Madeira River in the Brazilian Amazon, prior to startup of the Santo Antônio Hydroelectric Plant. The study gathered information on sociodemographic conditions, history of diseases, habits, fish consumption, and anthropometric parameters. Logistic regression was used to calculate odds ratios and the respective confidence intervals. Among the riverine communities, 26% (95%CI: 23%-29%) of adults presented hypertension (29% in men [95%CI: 24%-33%] and 23% in women [95%CI: 19%-27%]). Factors associated with hypertension were age, BMI, and place of residence in men and age, triglycerides, and blood glucose in women. The findings can contribute to strategies for state and municipal health services to monitor and prevent cardiovascular events. PMID:24005927

Oliveira, Beatriz Fátima Alves de; Mourão, Dennys de Souza; Gomes, Núbia; Costa, Janaina Mara C; Souza, Andreia Vasconcelos de; Bastos, Wanderley Rodrigues; Fonseca, Marlon de Freitas; Mariani, Carolina Fiorillo; Abbad, Guilherme; Hacon, Sandra S

2013-08-01

143

Ontogeny of the plastron of the giant Amazon River turtle, Podocnemis expanse (Schweigger, 1812) (Testudines, Podocnemididae).  

PubMed

Podocnemis expanse, known popularly as the giant Amazon river turtle, is widely exploited. This makes specimens available for various studies, and we used this opportunity to investigate aspects of the development of the plastron. We examined several stages of pre- and post- hatching development in embryos and hatchlings collected starting from day 18 of natural incubation. Embryos and hatchlings were cleared and double stained for cartilage and bone. The epiplastron, endoplastron, hyoplastron, hypoplastron, xiphiplastron, and mesoplastron bones form the complete plastron of this turtle. In stage 16, bone centers become visible in most of the bones of the plastron. Alizarin Red stain retention indicated that the sequence of bone ossification is as follows: first the hyoplastron and the hypoplastron, then the endoplastron followed by the xiphiplastron, and lastly the mesoplastron. The epiplastron bone shows an ossification center only in stage 20. All these elements have independent ossification centers and join together only later. The plastron closes completely seven months after hatching. PMID:19663644

Gonçalves Vieira, Lucélia; Quagliatto Santos, André L; Campos Lima, Fabiano; Souza Pinto, José G

2009-07-01

144

Exchanges of sediment between the flood plain and channel of the Amazon River in Brazil  

USGS Publications Warehouse

Sediment transport through the Brazilian sector of the Amazon River valley, a distance of 2010 km, involves exchanges between the channel and the flood plain that in each direction exceed the annual flux of sediment out of the river at O??bidos (???1200 Mt yr-1). The exchanges occur through bank erosion, bar deposition, settling from diffuse overbank flow, and sedimentation in flood-plain channels. We estimated the magnitude of these exchanges for each of 10 reaches of the valley, and combined them with calculations of sediment transport into and out of the reaches based on sediment sampling and flow records to define a sediment budget for each reach. Residuals in the sediment budget of a reach include errors of estimation and erosion or deposition within the channel. The annual supply of sediment entering the channel from bank erosion was estimated to average 1570 Mt yr-1 (1.3 ?? the O??bidos flux) and the amount transferred from channel transport to the bars (380 Mt yr-1) and the flood plain (460 Mt yr-1 in channelized flow; 1230 Mt yr-1 in diffuse overbank flow) totaled 2070 Mt yr-1 (1.7 ?? the O??bidos flux). Thus, deposition on the bars and flood plain exceeded bank erosion by 500 Mt yr-1 over a 10-16 yr period. Sampling and calculation of sediment loads in the channel indicate a net accumulation in the valley floor of approximately 200 Mt yr-1 over 16 yr, crudely validating the process-based calculations of the sediment budget, which in turn illuminate the physical controls on each exchange process. Another 300-400 Mt yr-1 are deposited in a delta plain downstream of O??bidos. The components of the sediment budget reflect hydrologie characteristics of the valley floor and geomorphic characteristics of the channel and flood plain, which in turn are influenced by tectonic features of the Amazon structural trough.

Dunne, T.; Mertes, L. A. K.; Meade, R. H.; Richey, J. E.; Forsberg, B. R.

1998-01-01

145

Iron isotope composition of the suspended matter along depth and lateral profiles in the Amazon River and its tributaries  

NASA Astrophysics Data System (ADS)

Samples of suspended matter were collected at different locations, seasons, depths and lateral profiles in the Amazon River and three of its main tributaries, the Madeira, the Solimões and the Negro rivers. Their iron isotope compositions were studied in order to understand the iron cycle and investigate the level of isotopic homogeneity at the river cross-section scale. Samples from four depth profiles and three lateral profiles analyzed show suspended matter ?57Fe values (relative to IRMM-14) between -0.501 ± 0.075‰ and 0.196 ± 0.083‰ (2SE). Samples from the Negro River, a blackwater river, yield the negative values. Samples from other stations (whitewater rivers, the Madeira, the Solimões and the Amazon) show positive values, which are indistinguishable from the average composition of the continental crust (?57FeIRMM-14 ˜ 0.1‰). Individual analyses of the depth and lateral profiles show no significant variation in iron isotope signatures, indicating that, in contrast to certain chemical or other isotopic tracers, one individual subsurface sample is representative of river deeper waters. This also suggests that, instead of providing detailed information on the riverine iron cycling, iron isotopes of particulate matter in rivers will rather yield a general picture of the iron sources.

dos Santos Pinheiro, Giana Márcia; Poitrasson, Franck; Sondag, Francis; Vieira, Lucieth Cruz; Pimentel, Márcio Martins

2013-07-01

146

Old sediment in young rivers- a multiple cosmogenic nuclide study in the Amazon basin  

NASA Astrophysics Data System (ADS)

The burial dating technique using in-situ produced cosmogenic isotope pairs (26Al and 10Be) of stationary geomorphic units like terrace deposits has become a valuable tool in deriving sediment deposition chronologies or paleo-denudation rates. In this study, we use 26Al/10Be ratios in detrital sediment from Amazonian rivers to explore the degrees of pre-erosional floodplain burial duration and burial depth as well as degrees of sediment mixing between the active modern rivers and old floodplain reservoirs. 26Al/10Be ratios below a surface production rate ratio of ~6.5 indicate sediment burial, as production of nuclides ceases due to deep shielding in the floodplain and differential decay of 26Al over 10Be causes 26Al/10Be ratios to decrease. Burial depths and durations can be constrained from a modified version of the erosion island plot (26Al/10Be ratio vs. 10Be nuclide concentration diagram) calculated for continuous irradiation during shallow burial. In order to constrain sediment mixing, we analyzed >40 samples for their 26Al/10Be ratios, encompassing the Andean as well as the Guyana and Brazilian Shield headwaters, and the main Amazonian lowland rivers that receive sediment from these differently eroding source areas (Solimões, Amazon, Madeira, Tapajós). The following first-order implications emerge: (i) samples from rapidly denuding Andean headwater streams typically are not affected by burial. (ii) in the Guyana and Brazilian Shield headwaters, average 26Al/10Be ratios are ~5.0, with burial durations between 0.5-1.0 Myr at burial depths around 3 m. (iii) in lowland rivers of central Amazonia that mostly drain the cratonic headwaters (Tapajós, Madeira), coarser grain sizes (> 500 µm) yield 26Al/10Be ratios similar to their cratonic headwaters, whereas finer grain sizes (125-500 µm) reflect the unburied modern stream sediment. (iv) in lowland rivers receiving most sediment from Andean headwaters (Solimões, Amazon), no trend for burial ratio vs. grain size is observable, and typical 26Al/10Be ratios of the main Amazon River are ~5.3, with associated average burial durations of <1 Myr at average depths of ~12 m. Here, also finer grain sizes show deeper burial at ratios <5.0. We observe that when plotted in an erosion island plot, central Amazonian samples evolve along mixing lines between a non-buried Andean end member (represented by modern fluvial sediment produced from hillslope erosion in the source area under continuous cosmic-ray exposure), and a deeply buried end member represented by ~Miocene floodplain sediment. The slope of the mixing lines is hereby a function of the prevailing denudation rate prior burial. For the Miocene floodplain end member, very low burial ratios of ~ 3.0 and long burial durations of ~10 Myr have been measured (Wittmann and von Blanckenburg, 2009). This buried sediment is incorporated into modern, Andean-derived sediment during channel avulsions. Using this dataset, we cannot only constrain the mixing of sediments from different provenances in the classical sense, but can also trace mixing fractions and account for floodplain burial of sediment along the long transfer of sediment from their source areas to the central Amazonian lowlands.(Wittmann, H., and von Blanckenburg, F., 2009, Cosmogenic nuclide budgeting of floodplain sediment transfer: Geomorphology, v. 109, no. 3-4, p. 246-256.)

Wittmann, Hella; von Blanckenburg, Friedhelm; Maurice, Laurence; Guyot, Jean-Loup; Kubik, Peter

2010-05-01

147

Revealing forms of iron in river-borne material from major tropical rivers of the Amazon Basin (Brazil)  

NASA Astrophysics Data System (ADS)

The present study deals with the direct determination of colloidal forms of iron in river-borne solids from main rivers of the Amazon Basin. The contribution of different forms of colloidal iron have been assessed using ultrafiltration associated with various techniques including electron paramagnetic resonance spectroscopy (EPR), high resolution transmission electron microscopy (HRTEM), and micro proton-induced X ray emission analysis (?PIXE). EPR shows the presence of Fe 3+ bound to organic matter (Fe 3+-OM) and colloidal iron oxides. Quantitative estimate of Fe 3+-OM content in colloidal matter ranges from 0.1 to 1.6 weight % of dried solids and decreases as the pH of the river increases in the range 4 to 6.8. The modeling of the field data with the Equilibrium Calculation of Speciation and Transport (ECOSAT) code demonstrates that this trend is indicative of a geochemical control resulting from the solubility equilibrium of Fe oxyhydroxide phase and Fe binding to organic matter. Combining EPR and ?PIXE data quantitatively confirms the presence of colloidal iron phase (min. 35 to 65% of iron content), assuming no divalent Fe is present. In the Rio Negro, HRTEM specifies the nature of colloidal iron phase mainly as ferrihydrite particles of circa 20 to 50 Å associated with organic matter. The geochemical forms of colloidal iron differentiate the pedoclimatic regions drained by the different rivers, corresponding to different major weathering/erosion processes. Modeling allows the calculation of the speciation of iron as mineral, organic and dissolved phases in the studied rivers.

Allard, T.; Menguy, N.; Salomon, J.; Calligaro, T.; Weber, T.; Calas, G.; Benedetti, M. F.

2004-07-01

148

New dactylogyrids (Monogenea) parasitizing the gills of catfishes (Siluriformes) from the Amazon River basin in Peru.  

PubMed

Three dactylogyrid (Monogenea) species are described from the gills of siluriform fishes from the rivers around Iquitos, tributaries of the Amazon River in Peru: Demidospermus centromochli n. sp. from Centromochlus heckelii (de Filippi) (Auchenipteridae) and Demidospermus macropteri n. sp. and Ameloblastella unapi n. sp. from Calophysus macropterus (Lichtenstein) (Pimelodidae). The new species of Demidospermus differ from their congeners in having 2 different hook shapes. Ameloblastella unapi n. sp. differs from the other 3 species of the genus in having anchors with an elongate, straight shaft and a short point that forms a 90 degrees angle, a coiled (counterclockwise) male copulatory organ with 13-14 rings, and a coiled vaginal tube. Based on the present study, Pseudovancleaveus Franca, Issac, Pavanelli, and Takemoto, 2003, is regarded as a junior subjective synonym of Ameloblastella Kritsky, Mendoza-Franco, and Scholz, 2000. The finding of Demidospermus and Ameloblastella spp. on these siluriforms extends our host and geographic knowledge of species of these monogenean genera to Peru. PMID:19215149

Mendoza-Franco, Edgar F; Scholz, T

2009-08-01

149

Fish contamination and human exposure to mercury in Tartarugalzinho river, Amapa State, Northern Amazon, Brazil. A screening approach  

Microsoft Academic Search

This study reports for the first time, the Hg concentrations in the fish fauna of the Tartarugalzinho river basin — an important\\u000a gold mining region in Amapa State, Northern Amazon — and evaluates human exposure to Hg due to fish consumption in the area.\\u000a We analyzed 16 fish species (carnivorous and omnivorous) common in the aquatic environment of the Tartarugalzinho

E. D. Bidone; Z. C. Castilhos; T. J. S. Santos; T. M. C. Souza; L. D. Lacerda

1997-01-01

150

A seasonal tropical sink for atmospheric CO 2 in the Atlantic ocean: the role of the Amazon River discharge  

Microsoft Academic Search

In the western equatorial Atlantic ocean, near-surface observations show that during summertime, the low-salinity oceanic water, arising from mixing with the Amazon River discharge at the equator, has low CO2 fugacity levels. Near the coast of South America where the salinities are the lowest (S<20), the fugacity of oceanic CO2 decreases down to 150 ?atm and the shelf area acts

J. F Ternon; C Oudot; A Dessier; D Diverres

2000-01-01

151

Particle size of sediments collected from the bed of the Amazon River and its tributaries in May and June 1977  

USGS Publications Warehouse

One-hundred-eight samples of bed material were collected from the Amazon River and its major tributaries between Belem, Brazil , and Iquitos, Peru. Samples were taken with a standard BM-54 sampler or with pipe dredges from May 18 to June 5, 1977. Most of the samples have median diameters in the size range of fine to medium sand and contain small percentages of fine gravel. Complete size distributions are tabulated. (Woodard-USGS)

Nordin, Carl F.; Meade, R. H.; Curtis, W. F.; Bosio, N. J.; Delaney, B. M.

1979-01-01

152

Particle size of sediments collected from the bed of the Amazon River and its tributaries in June and July 1976  

USGS Publications Warehouse

Sixty-five samples of bed material were collected from the Amazon River and its major tributaries between Belem, Brazil, and Iquitos, Peru. Samples were taken with a standard BM-54 sampler, a pipe dredge, or a Helley-Smith bedload sampler. Most of the samples have median diameters in the size range of fine to medium sand and contain small percentages of fine gravel. Complete size distributions are tabulated.

Nordin, Carl F., Jr.; Meade, R. H.; Mahoney, H. A.; Delany, B. M.

1977-01-01

153

Role of gas exchange in the inorganic carbon, oxygen, and ²²²Rn budgets of the Amazon River  

Microsoft Academic Search

Dissolved oxygen, ²²²Rn, pCOâ, alkalinity, respiration rate, and discharge have been measured at eight mainstem and seven tributary stations during February-March 1984 in a 1700-km stretch of the Amazon River between Vargem Grande and Obidos in Brazil. Air-water gas exchange rates were estimated two ways: measurements of the flux of ²²²Rn int floating domes yielded an average boundary layer thickness

ALLAN H. DEVOL; PAUL D. QUAY; JEFFREY E. RICHEY; LUIZ A. MARTINELLI

1987-01-01

154

Excitation–emission fluorescence matrix to study pH influence on organic matter fluorescence in the Amazon basin rivers  

Microsoft Academic Search

A study of the three-dimensional excitation–emission fluorescence matrix (EEFM) of organic matter from the Amazon basin rivers is reported in this paper. The EEFM, applied to the fractions obtained from sequential tangential ultrafiltration (STUF), give spectroscopic informations on the fluorescent properties of particulate (>0.22?m), colloidal and dissolved (<5kD) organic matter. STUF process does not seem to alter the characteristic peaks

N. Patel-Sorrentino; S. Mounier; J. Y. Benaim

2002-01-01

155

Physical observations in the plume region of the Amazon River during peak discharge---I. Surface variability  

Microsoft Academic Search

Satellite imagery in the 0.4-1.1 mum band from GOES, NOAA-7 and NIMBUS-7 and shipboard measurements of suspended sediment concentration and chlorophyll are synthesized. Five main surface features are delineated in the plume region of the Amazon during peak discharge: a River Zone (RZ), Interaction Zones A, B and C (IZA, IZB, IZC), and a Nearshore Zone (NZ). The loci, temporal

Thomas B. Curtin; Richard V. Legeckis

1986-01-01

156

Physical and biological contributions to the western tropical North Atlantic Ocean carbon sink formed by the Amazon River plume  

Microsoft Academic Search

Dissolved inorganic carbon (DIC) and total alkalinity (TA) were measured in the upper 1000 m of the western tropical North Atlantic Ocean (WTNA; study area 3–15°N, 40–59°W) in January–February and July–August 2001. Concentrations of DIC and TA in surface samples (0–10 m) influenced by the Amazon River plume were up to 400 ?mol C kg?1 (?20%) lower than oceanic surface

S. R. Cooley; P. L. Yager

2006-01-01

157

Flooding dynamics on the lower Amazon floodplain: 1. Hydraulic controls on water elevation, inundation extent, and river-floodplain discharge  

NASA Astrophysics Data System (ADS)

Modeling the routing of flood waters across large floodplains is challenging because flows respond to dynamic hydraulic controls from complex geomorphology, vegetation, and multiple water sources. In this study, we analyzed the topographic and hydrologic controls of inundation dynamics of a large floodplain unit (2440 km2) along the lower Amazon River. We combined land topography derived from the Shuttle Radar Topography Mission (SRTM) with underwater topography derived from an extensive echo-sounding survey to generate a seamless digital elevation model (DEM). Floodplain inundation was simulated using LISFLOOD-FP, which combines one-dimensional river routing with two-dimensional overland flow, and a local hydrological model. For the first time, accurate simulation of filling and drainage of an Amazon floodplain was achieved with quantification of changes in water elevation, flooding extent, and river-floodplain exchange. We examined the role of diffuse overbank versus channelized flows on river-floodplain exchange. Diffuse overbank flows represent 93% of total river to floodplain discharge and 54% of floodplain to river discharge. Floodplain discharge during high-water was four times higher than field observation values when the SRTM v.4 DEM with no correction was used for simulation because of a -4.4 m elevation bias originating from residual motion errors of the SRTM interferometric baseline.

Rudorff, Conrado M.; Melack, John M.; Bates, Paul D.

2014-01-01

158

Comparison of bacterial communities in the Solimões and Negro River tributaries of the Amazon River based on small subunit rRNA gene sequences.  

PubMed

The microbiota of the Amazon River basin has been little studied. We compared the structure of bacterial communities of the Solimões and Negro Rivers, the main Amazon River tributaries, based on analysis of 16S rRNA gene sequences. Water was sampled with a 3-L Van Dorn collection bottle; samples were collected at nine different points/depths totaling 27 L of water from each river. Total DNA was extracted from biomass retained by a 0.22-?m filter after sequential filtration of the water through 0.8- and 0.22-?m filters. The 16S rRNA gene was amplified by PCR, cloned and sequenced, and the sequences were analyzed with the PHYLIP and DOTUR programs to obtain the operational taxonomic units (OTUs) and to calculate the diversity and richness indices using the SPADE program. Taxonomic affiliation was determined using the naive Bayesian rRNA Classifier of the RDP II (Ribosomal Database Project). We recovered 158 sequences from the Solimões River grouped into 103 OTUs, and 197 sequences from the Negro River library grouped into 90 OTUs by the DOTUR program. The Solimões River was found to have a greater diversity of bacterial genera, and greater estimated richness of 446 OTUs, compared with 242 OTUs from the Negro River, as calculated by ACE estimator. The Negro River has less bacterial diversity, but more 16S rRNA gene sequences belonging to the bacterial genus Polynucleobacter were detected; 56 sequences from this genus were found (about 30% of the total sequences). We suggest that a more in-depth investigation be made to elucidate the role played by these bacteria in the river environment. These differences in bacterial diversity between Solimões and Negro Rivers could be explained by differences in organic matter content and pH of the rivers. PMID:22183948

Peixoto, J C C; Leomil, L; Souza, J V; Peixoto, F B S; Astolfi-Filho, S

2011-01-01

159

Mercury distribution and exchanges between the Amazon River and connected floodplain lakes.  

PubMed

This work presents the distribution and the partition of mercury (Hg) in the Curuai floodplain lakes along the Amazon River. The maximum Total Filtered Hg (T-FHg) concentrations in the floodplain lakes (28 to 52 pmol L(-1)) coincide with the maximum T-FHg concentrations of the Amazon River and are measured during the flooding period. The lowest T-FHg values (3 to 5 pmol L(-1)) are observed during the flood peak of the mainstream, during the rainy season, when waters are diluted by the local rainfall. In this system, Hg is mainly transported in the particulate phase, confirmed by elevated values of the Hg partition coefficient (4.77

Maia, Poliana Dutra; Maurice, Laurence; Tessier, Emmanuel; Amouroux, David; Cossa, Daniel; Pérez, Marcela; Moreira-Turcq, Patricia; Rhéault, Isabelle

2009-11-15

160

Late Quaternary Paleohydrology of the Madre de Dios River, southwestern Amazon Basin, Peru  

NASA Astrophysics Data System (ADS)

Late Quaternary climatic and hydrologic variability triggered changes in fluvial deposition and erosion along the course of the Madre de Dios River, Peru, the largest tributary basin of the Madeira basin, itself the largest tributary basin of the Amazon. Three laterally extensive, Quaternary-age, terrace tracts are present within the Madre de Dios basin. Analysis of sedimentary facies, present in the modern cut banks and terraced sequences, along with radiocarbon dates on fossil wood and leaf material preserved in the terraced strata, allow reconstruction of the Late Quaternary depositional history of the sedimentary sequences, including determination of the approximate timing of aggradation and downcutting episodes and its relationship to the timing of past climate change in this portion of the Amazon basin and beyond. The Quaternary sediments underlying the terraces most often recorded deposition in a coarse-grained meandering fluvial system. The T3 terrace, the highest terrace, is underlain by the Miocene (?) Ipururi Formation, which is unconformably overlain by the late Miocene-Pleistocene (?) (> 48,000 cal yrs BP) Madre de Dios Formation, a multistory coarse-sandy to gravelly channel and point bar complex. The latter was downcut before 29,850 ± 100 cal yrs BP. This downcut landscape was infilled by meandering fluvial strata characterized by gravelly channel deposits in a sequence dominated by floodplain and lateral accretion deposits. These strata were in turn downcut to form the T2 terrace before 11,970 ± 100 cal yrs BP. A third episode of aggradation resulted in the deposition of a sand-dominated meandering channel complex that infilled the T2 valley and was subsequently downcut after 3780 ± 50 cal yrs BP. This most recent terrace is infilled by the modern fluvial sediment, which has been actively aggrading since at least 870 ± 50 cal yrs BP. Importantly, the Madre de Dios fluvial system actively aggraded between 30,000 and 25,000 cal yrs BP, (and likely much younger, as dated samples were, thus far, only found near the base of the T2 sequence). This observation implies that some combination of (1) increased precipitation and decreased temperature, (2) decreased evapotranspiration and increased runoff, (3) increased Andean glacial erosion and increased sediment supply, and (4) decreased atmospheric CO 2 (hence decreased rain-forest primary productivity and altered rain-forest physiology/ecology), entering the last glacial maximum period brought about increased floodplain deposition in the southwestern Amazon. Elsewhere in the Amazon basin few, if any, fluvial sediments of this age range have been observed. The start of the next major phase of aggradation coincided with the Younger Dryas and suggested that floodplain sedimentation in the lowlands was again related to cold and wet conditions in the adjacent highlands (and perhaps in the lowlands as well) and that Madre de Dios history was also tied to large-scale global climate. This aggradation may have continued throughout the early and mid-Holocene, until at least 3,780 cal yr BP. If so (and this is uncertain), this episode of sedimentation took place during a dry period.

Rigsby, Catherine A.; Hemric, Erin M.; Baker, Paul A.

2009-12-01

161

Reconnaissance investigations of the discharge and water quality of the Amazon River  

USGS Publications Warehouse

Selected published estimates of the discharge of Amazon River in the vicinity of Obidos and the mouth are presented to show the great variance of available information. The most reasonable estimates prepared by those who measured some parameters of the flow were studied by Maurice Parde, who concluded that the mean annual discharge is 90,000 to 100,000 cms (cubic meters per second) or 3,200,000 to 3,500,000 cfs (cubic feet per second). A few published estimates of discharge at mouth of 110,000 cms (3,900,000 cfs) based on rainfall-runoff relationships developed for other humid regions of the world are available. Three measurements of discharge made at the Obidos narrows in 1963-64 by a joint Brazil-United States expedition at high, low, and medium river stage are referred to the datum used at the Obidos gage during the period of operation, 1928-46, and a relationship between stage and discharge prepared on the basis of the measurements and supplementary data and computations. Recovery of the original Obidos gage datum is verified by referring the 1963-64 concurrent river stages at Manaus, Obidos, and Taperinha to gage relation curves developed for Manaus-Obidos and Obidos-Taperinha for periods of concurrent operation, 1928-46 and 1931-46, respectively. The average discharge, based on the stage-discharge relation and record of river stage for the period 1928-46, is computed to be 5,500,000 cfs (157,000 cms) for the Obidos site. The greatest known flood at Obidos, that of June 1953, is computed to have been a flow of 12,500,000 cfs (350,000 cms) at stage of 7.6 meters (24.9 feet) in the main channel and an indeterminate amount of overflow which, under the best assumed overflow conditions, may have amounted to about 10 percent of the main channel flow. Overflow discharge at stage equivalent to mean annual discharge is judged to be an insignificant percentage of flow down the main channel. Miscellaneous data collected during the flow measurements show that the tidal effect reaches upstream to Obidos at extremely low flows, the distribution of velocities in stream verticals is affected by large-scale turbulence, the standard procedure of basing mean velocity in vertical on the average of point velocities measured at 20 and 80 percent of the total depth is valid, and there is a low Manning roughness coefficient of 0.019 (English units). Samples of suspended sediment taken with a point sampler at various depths in selected verticals show, for the Obidos site, a variation in concentration from 300 to 340 mg/l (milligram per liter) near the streambed to 50 to 70 mg/l in the upper part of the verticals. Median diameter of bed material at Obidos averaged about 0.20 mm (millimeter) in a range of 0.15 to 0.25 ram. Analyses of water samples collected at Obidos in July and November 1963 and August 1964 are presented. The reconnaissance measurements of 1963-64 provide a well-supported value of mean annual water discharge of Amazon River at Obidos and the mouth. Many more measurements of flow and water-quality characteristics are needed to obtain more exact values of discharge, suspended sediment, and salt load.

Oltman, Roy Edwin

1968-01-01

162

How important is it to integrate riverine suspended sediment chemical composition with depth? Clues from Amazon River depth-profiles  

NASA Astrophysics Data System (ADS)

The vertical variability in mineralogical, chemical and isotopic compositions observed in large river suspended sediments calls for a depth-integration of this variability to accurately determine riverine geochemical fluxes. In this paper, we present a method to determine depth-integrated chemical particulate fluxes of large rivers, based on river sampling along depth-profiles, and applied to the Amazon Basin lowland tributaries. The suspended particulate matter (SPM) concentration data from depth-profiles is modeled for a number of individual grain size fractions using the Rouse model, which allows to predict the grain size distribution of suspended sediment throughout the whole river cross-section. Then, using (1) the relationship between grain size distribution and the Al/Si ratio (2) relationships between the Al/Si ratio and the chemical concentrations, the chemical composition of river sediment is predicted throughout the river cross-section, and integrated to yield the depth-integrated chemical particulate flux for a number of chemical elements (e.g. Si, Al, Fe, Na, REEs, …). For elements such as Al, Fe, REEs, Th, the depth-integrated flux is around twice as high as the one calculated from river surface sample characteristics. For Na and Si, the depth-integrated flux is three times higher than the "surface" estimate, due to the enrichment of albite and quartz at the bottom of the river. Depth-integrated 87Sr/ 86Sr composition of suspended sediment, also predictable using this method, differs by more than 10 -3 from the surface sample composition. Finally, potential implications of depth-integrated estimates of Amazon sediment chemistry are explored. Depth-integration of particulate 87Sr/ 86Sr isotopic ratios is necessary for a reliable use of Sr isotopes as a provenance tracer. The concept of steady-state weathering of a large river basin is revisited using depth-integrated sediment composition. This analysis shows that, in the Amazon Basin river, the previously observed discrepancy between (1) weathering intensities of channel surface sediment and (2) silicate-derived dissolved fluxes is only slightly accounted for by the vertical variability of suspended sediment weathering intensities. This observation confirms that most large rivers basins are not eroding at steady-state.

Bouchez, Julien; Lupker, Maarten; Gaillardet, Jérôme; France-Lanord, Christian; Maurice, Laurence

2011-11-01

163

Calculations of river-runoff in the GISS GGM: impact of a new land-surface parameterization and runoff routing model on the hydrology of the Amazon River  

Microsoft Academic Search

This study examines the impact of a new land-surface parameterization and a river routing scheme on the hydrology of the Amazon basin, as depicted by the NASA\\/Goddard Institute of Space Studies (GISS) global climate model (GCM). The more physically realistic land surface scheme introduces a vegetation canopy resistance and a six-layer soil system. The new routing scheme allows runoff to

J. A. Marengo; J R Miller; G L Russell; C. E. Rosenzweig; F. Abramoloulos

1994-01-01

164

Spatial patterns of hydrology, geomorphology, and vegetation on the floodplain of the Amazon river in Brazil from a remote sensing perspective  

Microsoft Academic Search

The spatial heterogeneity of hydrology and vegetation during high-water periods in geomorphically distinct reaches of the Amazon River in Brazil was determined based on semivariance statistics. The spatial statistics were derived from three classified Landsat Thematic Mapper images representing upstream to downstream geomorphic characteristics. In the upstream river reach, scroll-bar topography on the floodplain tends to channelize floodwater into floodplain

Leal A. K. Mertes; Darin L. Daniel; John M. Melack; Bruce Nelson; Luiz A. Martinelli; Bruce R. Forsberg

1995-01-01

165

Mid-Holocene Drought in the Andes and Associated Impacts on Hydrology of the Amazon River  

NASA Astrophysics Data System (ADS)

Pollen, charcoal, and radiocarbon analyses were performed on a 2m-long sediment core obtained from Lake Tapera (coastal Amapa) to provide the paleoenvironmental history of this part of Amazonia. Detrended Correspondence Analysis was applied to the pollen data to improve visualization of sample distribution and similarity. The chronology was based on seven AMS radiocarbon dates, which allowed the establishment of a basal age (8,060 yrs BP) and identification of a sedimentary hiatus lasting 5,500 years (c. 7,100-1600 yrs BP) in Lake Tapera. Because the timing of the hiatus overlapped with the highest Holocene sea-level (5,000 yrs BP), which would have increased the local water table preventing the lake from drying out, it is clear that sea-level was not important in maintaining the lake level. As Lake Tapera apparently depended on riverine flood waters, the sedimentary gap was probably caused by reduced Amazon River discharge, due to an extremely dry period in the Andes (8,000-5,000 years BP), when precipitation levels markedly decreased. One of the impacts of this drought in the Andes was a c. 100m drop in Lake Titicaca water depth. The contrasting presence before and after the hiatus of Andean pollen (river transported) in the record of Lake Tapera supports this interpretation. The pollen analysis also shows that when sedimentation resumed in 1,620 cal. years BP, vegetation around the lake was changed from forest into savanna. This record demonstrates the need to improve our understanding of climate changes and the extent of their associated impacts on the environment.

de Toledo, M. B.; Bush, M. B.; Figueiredo, A. G.

2007-05-01

166

Differentiation in the fertility of Inceptisols as related to land use in the upper Solimões river region, western Amazon.  

PubMed

The Upper Solimões river region, western Amazon, is the homeland of indigenous populations and contains small-scale agricultural systems that are important for biodiversity conservation. Although traditional slash-and-burn agriculture is being practiced over many years, deforestation there is relatively small compared to other Amazon regions. Pastures are restricted to the vicinity of cities and do not spread to the small communities along the river. Inceptisols are the main soil order (>90%) in the area and have unique attributes including high Al content and high cation exchange capacity (CEC) due to the enrichment of the clay fraction with 2:1 secondary aluminosilicates. Despite its importance, few studies have focussed on this soil order when considering land use effects on the fertility of Amazon soils. Thus, the objective of this study was to evaluate changes in soil fertility of representative land use systems (LUSs) in the Upper Solimões region, namely: primary rainforest, old secondary forest, young secondary forest, agroforestry, pasture and agriculture. LUSs were significantly differentiated by the chemical attributes of their topsoil (0-20 cm). Secondary forests presented soil chemical attributes more similar to primary rainforest areas, while pastures exhibited the highest dissimilarity from all the other LUSs. As a whole, soil chemical changes among Inceptisols dominated LUSs showed patterns that were distinct from those reported from other Amazon soils like Oxisols and Ultisols. This is probably related to the presence of high-activity clays enriched in exchangeable aluminum that heavily influenced the soil chemical reactions over the expected importance of organic matter found in most studies conducted over Oxisol and Ultisol. PMID:19853281

Moreira, Fatima Maria de Souza; Nóbrega, Rafaela Simão Abrahão; Jesus, Ederson da Conceição; Ferreira, Daniel Furtado; Pérez, Daniel Vidal

2009-12-20

167

Effects of stocking density, periphyton substrate and supplemental feed on biological processes affecting water quality in earthen tilapia-prawn polyculture ponds  

Microsoft Academic Search

The technical and economic potentials of tilapia, Oreochromis niloticus (L.), and giant river prawn, Macrobrachium rosenbergii (de Man), polyculture in periphyton-based systems are under investigation in an extensive research programme. This article is a combined analysis of data from four experiments exploring the effects of periphyton, fish, prawn and feed on water quality. Factor analysis and ancova models applied to

Mohammed Sharif Uddin; A. Milstein; Mohammed Ekram Azim; Mohammed Abdul Wahab; Marc Verdegem; Johan Verreth

2008-01-01

168

A comparison of dissolved humic substances from seawater with Amazon River counterparts by sup 13 C-NMR spectrometry  

SciTech Connect

Although dissolved organic matter (DOM) in seawater constitutes one of the major reservoirs of reduced carbon on earth, the biochemical and geographic origins of this material and its hydrophobic humic component remain unclear. Rivers have been suggested as a potentially important source of marine DOM, but this implication has not yet been systematically tested by direct comparisons of the bulk structural characteristics of DOM isolated from representative ocean reservoirs and their major river sources. The authors report here such a comparison and find that dissolved humic substances isolated from surface and deep seawater in the East Equatorial and north Central Pacific are enriched in nitrogen and {sup 13}C and depleted in unsaturated carbon with respect to counterparts from the Amazon River system. Based on these observations, riverine dissolved humic substances appear to comprise a small fraction of seawater humic substances and therefore must be efficiently and rapidly removed from the ocean.

Hedges, J.I. (Univ. of Washington, Seattle (United States)); Hatcher, P.G. (Pennsylvania State Univ., University Park (United States)); Ertel, J.R. (Univ. of Georgia, Athens (United States)); Meyers-Schulte, K.J. (Naval Ocean Research Group, San Diego, CA (United States))

1992-04-01

169

A clip-domain serine proteinase homolog (SPH) in oriental river prawn, Macrobrachium nipponense provides insights into its role in innate immune response.  

PubMed

In this study, a clip-domain serine proteinase homolog designated as MnSPH was cloned and characterized from a freshwater prawn Macrobrachium nipponense. The full-length cDNA of MnSPH was 1897 bp and contained a 1701 bp open reading frame (ORF) encoding a protein of 566 amino acids, a 103 bp 5'-untranslated region, and a 93 bp 3'-untranslated region. Sequence comparison showed that the deduced amino acids of MnSPH shared 30-59% identity with sequences reported in other animals. Tissue distribution analysis indicated that the MnSPH transcripts were present in all detected tissues with highest in the hepatopancreas and ovary. The MnSPH mRNA levels in the developing ovary were stable at the initial three developmental stages, then increased gradually from stage IV (later vitellogenesis), and reached a maximum at stage VI (paracmasis). Furthermore, the expression of MnSPH mRNA in hemocytes was significantly up-regulated at 1.5 h, 6 h, 12 h and 48 h post Aeromonas hydrophila injection. The increased phenoloxidase activity also demonstrated a clear time-dependent pattern after A. hydrophila challenge. These results suggest that MnSPH participates in resisting to pathogenic microorganisms and plays a pivotal role in host defense against microbe invasion in M. nipponense. PMID:24878742

Ding, Zhili; Kong, Youqin; Chen, Liqiao; Qin, Jianguang; Sun, Shengming; Li, Ming; Du, Zhenyu; Ye, Jinyun

2014-08-01

170

Physical and biological contributions to the western tropical North Atlantic Ocean carbon sink formed by the Amazon River plume  

NASA Astrophysics Data System (ADS)

Dissolved inorganic carbon (DIC) and total alkalinity (TA) were measured in the upper 1000 m of the western tropical North Atlantic Ocean (WTNA; study area 3-15°N, 40-59°W) in January-February and July-August 2001. Concentrations of DIC and TA in surface samples (0-10 m) influenced by the Amazon River plume were up to 400 ?mol C kg-1 (˜20%) lower than oceanic surface samples. In this region, physical dilution by river water dominates DIC and TA inventories, driving CO2 partial pressure (pCO2) well below atmospheric levels. Nevertheless, DIC concentrations at most plume-influenced stations were 10-90 ?mol C kg-1 below levels expected from conservative mixing of seawater with low-salinity, low-CO2 Amazon River water. In this otherwise oligotrophic region, the diazotrophs Trichodesmium spp. and Richelia intracellularis were often abundant, supporting a link between increased carbon drawdown and nitrogen fixation in the outer plume. Net community production in the plume must surpass the fluxes of inorganic carbon from below and air-sea CO2 replacement to leave biologically mediated DIC deficits, which is possible under observed conditions. Biological activity lowers plume pCO2 30-120 ?atm below the conservative mixing line, and contributes to a CO2 deficit in the northern WTNA that outlasts the plume's physical structure.

Cooley, S. R.; Yager, P. L.

2006-08-01

171

The distribution of thiamin and pyridoxine in the western tropical North Atlantic Amazon River plume.  

PubMed

B-vitamins are recognized as essential organic growth factors for many organisms, although little is known about their abundance and distribution in marine ecosystems. Despite their metabolic functions regulating important enzymatic reactions, the methodology to directly measure different B-vitamins in aquatic environments has only recently been developed. Here, we present the first direct measurements of two B-vitamins, thiamin (B1), and pyridoxine (B6), in the Amazon River plume-influenced western tropical North Atlantic (WTNA) Ocean, an area known to have high productivity, carbon (C) and dinitrogen (N2) fixation, and C sequestration. The vitamins B1 and B6 ranged in concentrations from undetectable to 230 and 40 pM, respectively. Significantly higher concentrations were measured in the surface plume water at some stations and variation with salinity was observed, suggesting a possible riverine influence on those B-vitamins. The influences of vitamins B1 and B6 on biogeochemical processes such as C and N2 fixation were investigated using a linear regression model that indicated the availability of those organic factors could affect these rates in the WTNA. In fact, significant increases in C fixation and N2 fixation were observed with increasing vitamin B1 concentrations at some low and mesohaline stations (stations 9.1 and 1; p value <0.017 and <0.03, respectively). N2 fixation was also found to have a significant positive correlation with B1 concentrations at station 1 (p value 0.029), as well as vitamin B6 at station 9.1 (p value <0.017). This work suggests that there can be a dynamic interplay between essential biogeochemical rates (C and N2 fixation) and B-vitamins, drawing attention to potential roles of B-vitamins in ecosystem dynamics, community structure, and global biogeochemistry. PMID:23471170

Barada, Laila P; Cutter, Lynda; Montoya, Joseph P; Webb, Eric A; Capone, Douglas G; Sañudo-Wilhelmy, Sergio A

2013-01-01

172

Microsatellite loci for population and parentage analysis in the Amazon River dolphin (Inia geoffrensis de Blainville, 1817).  

PubMed

We developed specific primers for microsatellite DNA regions for the Amazon River dolphin or boto Inia geoffrensis, for use in population and conservation genetic studies. We also tested their transferability for two other species, Pontoporia blainvillei (sister taxon of I. geoffrensis) and Sotalia guianensis. A total of 12 microsatellite loci were polymorphic for the boto. An additional 25 microsatellite loci previously isolated from other cetacean species were also tested in the boto. The 26 polymorphic microsatellite loci indicate they will be excellent markers for studies of population structure and kinship relations of the boto. PMID:21564703

Gravena, Waleska; Hrbek, Tomas; DA Silva, Vera M S; Astolfi-Filho, Spartaco; Farias, Izeni P

2009-03-01

173

Amazon And Negro River Breeze And Manaus Urban Area Influence In Surface Wind And Water Vapor Daily Cycles  

NASA Astrophysics Data System (ADS)

Close to the urban area of Manaus the Negro and Amazon rivers provide a scenario where river breeze can be particularly well detected due to their width of about 5 - 10 km. Previous studies have looked into the river breeze in the Amazon Basin and detected their influence in surface data, particularly into the effect on wind and moisture. The heat island effect of the Manaus urban area has also been demonstrated using surface temperature data. Here we present an analysis using 35 years of surface weather station hourly data from the two Manaus airports, Eduardo Gomes (AEG) and Ponta de Pelada (APP). The location of these stations allows the analysis of local circulations contrasting the evolution close to the margin and in the Southern tip of the urban area and a more inland location (APP) about 25 km to the Northewest of AEG. We focus on dew point temperature, water vapor pressure, wind speed and direction providing direction statistics for the two stations and contrasting the evolution in the dry and wet seasons.In the AEG weather station data we found relatively high values of accumulated frequency of the southwest and northwest wind in the period from 9 am to 6 pm (local time - LT) due to the action of the river breeze associated to the Negro River. In June and July (dry season), when the wind was blowing from the Southeast (river-breeze wind), high values of vapor pressure (VP) were observed during the daytime due to the transport of moist air from river to land. In the wind frequency data of the APP weather station we verified maximums in nighttime and minimums in daytime period when the wind direction was from the Northwest. These characteristics of maximums and minimums of wind frequency were observed in Northeastern winds only in the dry season. High frequency of South winds in daytime and minimums in nighttime period also indicates the action of river breeze. When the wind direction was southern, we found high values of VP (e.g, higher than 30.5 hPa in several months). This occurs because southern wind, often times associated to river breeze, transports moist air from Negro River to land. The opposite, low levels of VP, was observed when the wind direction was northern, which in some cases are land-breeze wind. The northern wind transports dry air from Manaus city which decreases the values of VP over the APP region.

Dos Santos, M.; da Silva Dias, M. F.; Freitas, E. D.; Meteorologia Aplicada A Sistemas de Tempo Regionais-Master

2013-05-01

174

Role of gas exchange in the inorganic carbon, oxygen, and /sup 222/Rn budgets of the Amazon River  

SciTech Connect

Dissolved oxygen, /sup 222/Rn, pCO/sub 2/, alkalinity, respiration rate, and discharge have been measured at eight mainstem and seven tributary stations during February-March 1984 in a 1700-km stretch of the Amazon River between Vargem Grande and Obidos in Brazil. Air-water gas exchange rates were estimated two ways: measurements of the flux of /sup 222/Rn int floating domes yielded an average boundary layer thickness of 78..mu..m, and oxygen mass balance calculations resulted in an average of 38..mu..m. Given a boundary layer thickness on the order of 50..mu..m, CO/sub 2/ loss to the atmosphere in the entire reach would have been 37.4 kmol s/sup -1/, which is about equal to the total tributary dissolved inorganic carbon (DIC) input and is about half of the total fluvial DIC input to the section. Thus, CO/sub 2/ evasion is a major component of Amazon River DIC balance. Because gas exchange within the section was rapid relative to water travel time through the section, a quasi-steady state was maintained between respiratory input and evasion of CO/sub 2/. Dissolved /sup 222/Rn activities in the mainstem varied from 3.5 to 8.3 dpm liter/sup -1/ and were always highly supersaturated with respect to the atmosphere. Dissolved radon was also not supported by decay of /sup 222/Ra in the mainstem. A /sup 222/Rn mass balance indicated that direct groundwater input into this stretch of the Amazon mainstem probably accounted for no more than 1% of water discharge.

Devol, A.H.; Quay, P.D.; Richey, J.E.; Martinelli, L.A.

1987-01-01

175

Potamotrygon limai, sp. nov., a new species of freshwater stingray from the upper Madeira River system, Amazon basin (Chondrichthyes: Potamotrygonidae).  

PubMed

Potamotrygon limai, sp. nov., is described from the Jamari River, upper Madeira River system (Amazon basin), state of Rondônia, Brazil. This new species differs from congeners by presenting unique polygonal or concentric patterns formed by small whitish spots better defined over the posterior disc and tail-base regions. Potamotrygon limai, sp. nov., can be further distinguished from congeners in the same basin by other characters in combination, such as two to three rows of midtail spines converging to a single irregular row at level of caudal sting origin, proportions of head, tail and disc, patterns of dermal denticles on rostral, cranial and tail regions, among other features discussed herein. Potamotrygon limai, sp. nov., is most similar to, and occurs sympatrically with, P. scobina, and is distinguished from it by lacking ocellated spots on disc, by its characteristic polygonal pattern on posterior disc, a comparatively much shorter and broader tail, greater intensity of denticles on disc, more midtail spine rows at tail-base, and other features including size at maturity and meristic characters. Potamotrygon limai, sp. nov., is also distinguished from other species of Potamotrygon occurring in the Amazon region, except P. scobina, by presenting three angular cartilages (vs. two or one). This new species was discovered during a detailed taxonomic and morphological revision of the closely related species P. scobina, and highlights the necessity for thorough and all-embracing taxonomic studies, particularly in groups with pronounced endemism and morphological variability. PMID:24870898

Fontenelle, João Pedro; Da Silva, João Paulo C B; De Carvalho, Marcelo R

2014-01-01

176

Impact of seasonal hydrological variation on the distributions of tetraether lipids along the Amazon River in the central Amazon basin: implications for the MBT/CBT paleothermometer and the BIT index.  

PubMed

Suspended particulate matter (SPM) was collected along the Amazon River in the central Amazon basin and in three tributaries during the rising water (RW), high water (HW), falling water (FW) and low water (LW) season. Changes in the concentration and the distribution of branched glycerol dialkyl glycerol tetraethers (brGDGTs), i.e., the methylation index of branched tetraethers (MBT) and the cyclization of brGDGTs (CBT), were seen in the Amazon main stem. The highest concentration of core lipid (CL) brGDGTs normalized to particulate organic carbon (POC) was found during the HW season. During the HW season the MBT and CBT in the Amazon main stem was also most similar to that of lowland Amazon (terra firme) soils, indicating that the highest input of soil-derived brGDGTs occurred due to increased water runoff. During the other seasons the MBT and CBT indicated an increased influence of in situ production of brGDGTs even though soils remained the main source of brGDGTs. Our results reveal that the influence of seasonal variation is relatively small, but can be clearly detected. Crenarchaeol was mostly produced in the river. Its concentration was lower during the HW season compared to that of the other seasons. Hence, our study shows the complexity of processes that influence the GDGT distribution during the transport from land to ocean. It emphasizes the importance of a detailed study of a river basin to interpret the MBT/CBT and BIT records for paleo reconstructions in adjacent marine setting. PMID:23966986

Zell, Claudia; Kim, Jung-Hyun; Abril, Gwenaël; Sobrinho, Rodrigo Lima; Dorhout, Denise; Moreira-Turcq, Patricia; Sinninghe Damsté, Jaap S

2013-01-01

177

Bioaccumulation of polychlorinated biphenyls and metals from contaminated sediment by freshwater prawns, Macrobrachium rosenbergii and clams, Corbicula fluminea  

Microsoft Academic Search

Freshwater prawns,Macrobrachium rosenbergii, and clams,Corbicula fluminea, were exposed for 48 or 50 days to three concentrations of a river sediment that contained environmental contaminants such as polychlorinated biphenyls (PCBs) and metals. Sediment was obtained twice during 1980 from the same location. Prawns were exposed to the first batch, sediment 5–80, which contained higher concentrations of some metals and PCBs compared

Henry E. Tatem

1986-01-01

178

Influence of the Amazon River discharge on the biogeography of phytoplankton communities in the western tropical north Atlantic  

NASA Astrophysics Data System (ADS)

An Advanced Laser Fluorometer (ALF) capable of discriminating several phytoplankton pigment types was utilized in conjunction with microscopic data to map the distribution of phytoplankton communities in the Amazon River plume in May-June-2010, when discharge from the river was at its peak. Cluster analysis and Non-metric Multi-Dimensional Scaling (NMDS) helped distinguish three distinct biological communities that separated largely on the basis of salinity gradients across the plume. These three communities included an “estuarine type” comprised of a high biomass mixed population of diatoms, cryptophytes and green-water Synechococcus spp. located upstream of the plume, a “mesohaline type” made up largely of communities of Diatom-Diazotroph Associations (DDAs) and located in the northwestern region of the plume and an “oceanic type” in the oligotrophic waters outside of the plume made up of Trichodesmium and Synechococcus spp. Although salinity appeared to have a substantial influence on the distribution of different phytoplankton groups, ALF and microscopic measurements examined in the context of the hydro-chemical environment of the river plume, helped establish that the phytoplankton community structure and distribution were strongly controlled by inorganic nitrate plus nitrite (NO3 + NO2) availability whose concentrations were low throughout the plume. Towards the southern, low-salinity region of the plume, NO3 + NO2 supplied by the onshore flow of subsurface (?80 m depth) water, ensured the continuous sustenance of the mixed phytoplankton bloom. The large drawdown of SiO3 and PO4 associated with this “estuarine type” mixed bloom at a magnitude comparable to that observed for DDAs in the mesohaline waters, leads us to contend that, diatoms, cryptophytes and Synechococcus spp., fueled by the offshore influx of nutrients also play an important role in the cycling of nutrients in the Amazon River plume.

Goes, Joaquim I.; Gomes, Helga do Rosario; Chekalyuk, Alexander M.; Carpenter, Edward J.; Montoya, Joseph P.; Coles, Victoria J.; Yager, Patricia L.; Berelson, William M.; Capone, Douglas G.; Foster, Rachel A.; Steinberg, Deborah K.; Subramaniam, Ajit; Hafez, Mark A.

2014-01-01

179

Boat-Based Eddy Covariance Measurements of CO2 and H2O Exchange Over Amazon and Tapajos Rivers and Lakes  

NASA Astrophysics Data System (ADS)

Recent reports suggest that gas evasion of carbon dioxide from the Amazon river and its tributaries to the atmosphere may play an important role in the regional carbon budget. These gas transfer rates were estimated using air-water concentration gradients and gas transfer coefficients (piston velocities) derived from floating chamber measurements. Chamber techniques have inherent uncertainties due to their effect on the near-surface air turbulence. The micrometeorological technique of eddy covariance is attractive since it is a direct measurement of gas exchange and samples over a much larger area. In August 2004, we mounted equipment on a small riverboat to measure CO2 and H2O fluxes from the rivers and lakes near Santarem, Para. The motion of the boat was recorded using an inertial measurement package combined with a GPS receiver, and subtracted from the measured winds. We experimented with both thin-wall Teflon tubing and headspace equilibrators to measure the concentration of CO2 in the water continuously. Our sampling strategy included both "under-way" measurements and stationary (moored) 24-hour measurements on the Amazon and Tapajos rivers, and lakes connected to these rivers. CO2 concentration in the Amazon river and a connected lake was 3000-5000 ppm, much higher than the Tapajos river and a connected lake (range 400-1200 ppm). The "signal-to-noise" ratio was therefore greater for fluxes measured above the Amazon. Preliminary calculations indicate fluxes of order 1-2 micromoles/m2/s over the Amazon and 0.6-1 micromoles/m2/s over the Tapajos, and the calculated gas transfer velocity agrees with existing ocean-based parameterizations.

Miller, S.; Freitas, H.; Read, E.; Goulden, M.; Rocha, H.; Doughty, C.

2004-12-01

180

Mapping the Amazon: Manaus  

NSDL National Science Digital Library

The largest city along the Amazon River is Manaus. NASAs mosaic says that thirty percent of the surrounding area is wetlands. Scientists listed worked as a team on Mosaicking Software and Mosaic Production.

Snodgrass, Stuart; Chapman, Bruce; Curkendall, David; Freeman, Tony; Miller, Craig; Siegel, Herb

2002-03-14

181

Methylmercury exposure affects motor performance of a riverine population of the Tapajós river, Brazilian Amazon.  

PubMed

Gold mining and deforestation in the Brazilian Amazon are increasing mercury pollution of the extensive water system, exposing riverine populations to organic mercury through fish-eating. The aim of the present study was to evaluate the effect of such exposure on motor performance. This cross-sectional study was carried out in May 1996, in a village located on the banks of the Tapajós river in the Amazonian Basin, Brazil. Information concerning sociodemographics, health, smoking habits, alcohol drinking, dietary habits and work history were collected using an interview-administered questionnaire. Mercury concentrations were measured by cold vapor atomic absorption in blood and hair of each participant, of whom those aged between 15 and 79 years were assessed for motor performance (n = 84). Psychomotor performance was evaluated using the Santa Ana manual dexterity test, the Grooved Pegboard Fine motor test and the fingertapping motor speed test. Motor strength was measured by dynamometry for grip and pinch strength. Following the exclusion of 16 persons for previous head injury, working with mercury in the goldmining sites, or for diabetes, the relationship between performance and bioindicators of mercury was examined using multivariate statistical analyses, taking into account covariables. All participants in the study reported eating fish, which comprised 61.8% of the total meals eaten during the preceding week. The median hair total mercury concentration was 9 microg/g. Organic mercury accounted for 94.4 = 1.9% of the total mercury levels. Multivariate analysis of variance indicated that hair mercury was inversely associated with overall performance on the psychomotor tests, while a tendency was observed with blood mercury. Semipartial regression analyses showed that hair total mercury accounted for 8% to 16% of the variance of psychomotor performance. Neither hair nor blood total mercury was associated with the results of the strength tests in women and men. Although dose-effect relationships were observed in this cross-sectional study, they may reflect higher exposure levels in the past. The findings of this study demonstrated neurobehavioral manifestations of subtle neurotoxic effects on motor functions, associated with low-level methylmercury exposure. PMID:10787135

Dolbec, J; Mergler, D; Sousa Passos, C J; Sousa de Morais, S; Lebel, J

2000-04-01

182

The source and fate of sediment and mercury in the Tapajós River, Pará, Brazilian Amazon: Ground and space-based evidence  

Microsoft Academic Search

We present results of mercury (Hg) in surface waters and soils and an analysis of satellite imagery from the Tapajós River basin, Brazilian Amazon, and the Reserva Garimpeira do Tapajós, the legal gold mining district of the basin.Hg bound to suspended sediment was roughly 600 and 200 times the concentration of dissolved Hg per litre of water, in impacted and

Kevin Telmer; Maycira Costa; Rômulo Simões Angélica; Eric S. Araujo; Yvon Maurice

2006-01-01

183

The source and fate of sediment and mercury in the Tapajos River, Para´ , Brazilian Amazon: Ground and space-based evidence  

Microsoft Academic Search

We present results of mercury (Hg) in surface waters and soils and an analysis of satellite imagery from the Tapajos River basin, Brazilian Amazon, and the Reserva Garimpeira do Tapajos, the legal gold mining district of the basin. Hg bound to suspended sediment was roughly 600 and 200 times the concentration of dissolved Hg per litre of water, in impacted

Kevin Telmera; Eric S. Araujof; Yvon Mauriceg

184

Boat-Based Eddy Covariance Measurements of CO2 and H2O Exchange Over Amazon and Tapajos Rivers and Lakes  

Microsoft Academic Search

Recent reports suggest that gas evasion of carbon dioxide from the Amazon river and its tributaries to the atmosphere may play an important role in the regional carbon budget. These gas transfer rates were estimated using air-water concentration gradients and gas transfer coefficients (piston velocities) derived from floating chamber measurements. Chamber techniques have inherent uncertainties due to their effect on

S. Miller; H. Freitas; E. Read; M. Goulden; H. Rocha; C. Doughty

2004-01-01

185

Impact of seasonal hydrological variation on the distributions of branched and isoprenoid tetraether lipids along the Amazon River in the central Amazon basin: Implications for the MBT/CBT paleothermometer and the BIT index  

NASA Astrophysics Data System (ADS)

We assessed the effects of hydrodynamical variations on the distributions and sources of branched and isoprenoid glycerol dialkyl glycerol tetraethers (brGDGTs and isoGDGTs, respectively) transported by the Amazon River in the central Amazon basin. Particulate suspended matter was collected in the Amazonian rivers and floodplain lakes at four different seasons (rising water, high water, falling water, and low water) at 6 stations along the main stem of the Amazon River, 3 tributaries (Negro, Madeira, and Tapajós) and 5 floodplain lakes (Manacapuru, Janauacá, Mirituba, Canaçari and Curuai). The concentration and distribution of brGDGTs of both core lipid (CL) and intact polar lipid (IPL)-derived fractions were investigated applying IPL-derived brGDGTs as an indicator of brGDGTs derived from recently-living cells. The organic carbon (OC)-normalized concentrations of CL brGDGTs mimicked the trend of the hydrological variation with highest concentrations during the high water season. The CL brGDGT distributions were most alike those of lowland Amazon (terra firme) soils during the high water season, indicating that input of soil-derived, allochthonous brGDGTs to the Amazon River was highest at that period. Accordingly, the methylation index of branched tetraethers (MBT) and the cyclization ratio of branched tetraethers (CBT) varied corresponding to the hydrological changes, with the increasing influence of in situ produced brGDGTs in rivers and floodplain lakes during the low water season. The concentrations of CL crenarchaeol were highest during the low water season, due to increased autochthonous production. The concentration changes of both brGDGTs and crenarchaeol lead to a variation of the branched and isoprenoid tetraether (BIT) index between 0.4 (low water) and 0.9 (high water). Hence, our study hints at the effect of hydrodynamical variations on the source of brGDGTs and isoGDGTs transported by rivers to the ocean and emphasized the importance of a detailed study of a river basin before applying the MBT/CBT paleothermometer and the BIT index in the adjacent marine setting.

Zell, Claudia; Kim, Jung-Hyun; Lima Sobrinho, Rodrigo; Moreira-Turcq, Patricia; Abril Abril, Gwenaël; Sinninghe Damsté, Jaap S.

2013-04-01

186

The relationship between the water level of the Amazon River and the fate of the zooplankton population in lago Jacaretinga. A Várzea Lake in the Central Amazon  

Microsoft Academic Search

In a várzea lake of the Central Amazon the planktonic crustaceans disappear almost completely after the inflow of suspension?rich Amazon water. An initial small increase in numbers of individuals is accompanied by increased egg production in Diaphanosoma sarsi and Notodiaptomus amazonicus, suggesting an improved food supply for the Zooplankton. Possible reasons for the complete disappearance of the crustaceans are discussed,

E. R. de Andrade

1978-01-01

187

Discharge and suspended sediment flux estimated along the mainstream of the Amazon and the Madeira Rivers (from in situ and MODIS Satellite Data)  

NASA Astrophysics Data System (ADS)

Water and suspended sediment fluxes are considered during the period 2000-2008 in a region including the full Amazon River from the confluence of the Negro River to Santarém, the end part of the Solimões River, and the lower part of the Madeira River. Three types of data are used: water discharge estimated from field measurements, and suspended sediment obtained from field measurements and derived from MODIS satellite data. A generalized least square method including a propagating term is developed in order to propagate the signal upward and downward the river. The approach is introduced and tested. Several experiments are considered in order, first, to estimate the ability to propagate the signal from stations located before the confluences of Negro and Madeira Rivers to stations located on the Amazon River; second to investigate the possibility to propagate the signal along the Amazon River which dynamics is coupled with floodplains dynamics; and third to produce optimal solutions of water and sediment fluxes. For each experiment, the influence of field and satellite data is compared. The approach is efficient in the upper part of the region of study where the Solimões, the Negro and the Madeira Rivers meet and fails in the lower part of the region where interactions between Amazon River and floodplains play an important role on the fluxes' dynamics. The optimal experiment includes in situ and satellite data from all the stations available and is used to analyse the recent evolution of suspended sediment flux along the Amazon River and its interaction with the large coupled floodplains. A high accumulation rate is observed during the 2000-2002 period, followed by decreasing rates until 2005 and by increasing values in 2006 and 2007. Our results suggest that floodplains extending along a river reach of 390 km-long between Itacoatiara and Óbidos trap about 15% of the suspended sediment flux passing at Óbidos. The simulated deposition rate is of about 0.3 Mt km-1 yr-1 corresponding to an accretion rate of about 27 mm yr-1.

Mangiarotti, S.; Martinez, J.-M.; Bonnet, M.-P.; Buarque, D. C.; Filizola, N.; Mazzega, P.

2013-04-01

188

Increasing the profitability of traditional, planted rubber agroforests at the Tapajós river, Brazilian Amazon  

Microsoft Academic Search

The planted rubber agroforests of the Tapajós region in eastern Pará State, Brazilian Amazon, are a traditional land use practice of intermediate intensity between extractivism in natural forest and plantation agriculture, and thus of potential interest especially for inhabited conservation areas and Extractive Reserves. We measured rubber production of five groves of 23–40 years of age on representative soil types

G. Schroth; V. H. F. Moraes; M. S. S. da Mota

2004-01-01

189

Mercury pollution in the Tapajos River basin, Amazon Mercury level of head hair and health effects  

Microsoft Academic Search

There is increasing concern about the potential neurotoxic effects of exposure to methylmercury for the 6 million people living in the Amazon, even in regions situated far away from the gold mines (garimpos), considered to be the major source of mercury pollution. In November 1998, a spot investigation on mercury contamination was conducted in three fishing villages (Barreiras, Rainha, and

Masazumi Haradaa; Maria da Conceicao; N. Pinheiroc; Hideki Ohnod

190

The dispersal of the Amazon and Orinoco River water in the tropical Atlantic and Caribbean Sea: Observation from space and S-PALACE floats  

Microsoft Academic Search

Abstract The temporal,evolutionof,spatial pattern s of the colored water mass,associated with the discharges of the Amazon and Orinoco Rivers between,1997 and,2002 was,examined,using concurrent,in situ and,satellite observations,in the regionboun ded,by 0 1N–241 Na n d7,01W–401W. Patches of low-salinity (? 32–34) surface waters,were,frequently observed,with Salinity Profiling Autonomous,LAgrangian Current Explorer (S-PALACE) floats as far as 2000 km,away from the mouths,of the Amazon,and Orinoco

Chuanmin Hu; Ellyn T. Montgomery; Raymond W. Schmitt; Frank E. Muller-Karger

2004-01-01

191

The Influence of Historical and Potential Future Deforestation on the Stream Flow of the Amazon River -- Land Surface Processes and Atmospheric Feedbacks  

NASA Astrophysics Data System (ADS)

Global economic and regional population and development pressures have resulted in high rates of deforestation in the Amazon River basin, mostly in the eastern and southern portion of the basin. Recent deforestation rates reflect the global demand for Brazilian free-range beef and soybeans with about 22,000 km2 deforested each year between 2000 and 2004 and 7000 km2 deforested in the final months of 2007. Land cover and land use changes influence the quantity of surface water resources by changing how incoming precipitation and radiation are partitioned among sensible and latent heat fluxes, runoff, and river discharge and altering regional and continental scale precipitation patterns. Results from coupled land surface and global climate model simulations clarify a few important points about the impact of deforestation on the Amazon River: 1) The local evapotranspiration decrease and subsequent discharge increase can be a significant fraction of the water balance when greater than 50% of a watershed is deforested. 2) The atmospheric feedbacks from large-scale deforestation may be of the same order of magnitude as the changes to local land surface processes, but of opposite sign and are not limited to those basins where deforestation has occurred. 3) Changes to discharge and aquatic environments with future deforestation of the Amazon will likely be a complex function of how much vegetation has been removed from a particular watershed and how much has been removed from the entire Amazon Basin.

Coe, M. T.; Costa, M. H.; Soares-Filho, B.

2008-12-01

192

Molecular differentiation of species of the genus Zungaro (Siluriformes, Pimelodidae) from the Amazon and Paraná-Paraguay River basins in Brazil.  

PubMed

Fish species of the Zungaro genus (Siluriformes, Pimelodidae) are amongst the largest migratory fish in Latin America and have considerable economic importance for commercial fishing in Brazil. However, natural populations of this large catfish are experiencing a severe decline. There are significant taxonomical inconsistencies for this fish. Two geographically separated species of the fish were initially described, one endemic in the Amazon and another in the Paraná-Paraguay River basins. A taxonomic review had recently proposed that there is only one Zungaro species in Brazil, based on morphological data. We made a molecular study of Zungaro populations in an attempt to solve taxonomical inconsistencies and to analyze genetic diversity in natural populations of this genus. We analyzed two regions of the mitochondrial DNA (the control region and the ATPase 6 gene region) of individuals sampled from the Paraná-Paraguay River and Amazon River basins. Analyses based on p-distances and maximum likelihood phylogenetic models showed a genetic difference between populations corresponding to different species. Genetic differentiation between Zungaro populations was at the same level as that observed between other Siluriformes species, using the same DNA sequences. We conclude that Zungaro species of the Paraná-Paraguay River basin do not belong to the same species found in the Amazon basin. This finding has a significant implication for conservation of this fish, given that populations are disappearing at a high rate in the Paraná-Paraguay River basin, mainly due to impoundments. PMID:22095604

Boni, T A; Padial, A A; Prioli, S M A P; Lucio, L C; Maniglia, T C; Bignotto, T S; Panarari-Antunes, R S; Prioli, R A; Prioli, A J

2011-01-01

193

Placentation in dolphins from the Amazon River Basin: the Boto, Inia geoffrensis, and the Tucuxi, Sotalia fluviatilis  

PubMed Central

A recent reassessment of the phylogenetic affinities of cetaceans makes it timely to compare their placentation with that of the artiodactyls. We studied the placentae of two sympatric species of dolphin from the Amazon River Basin, representing two distinct families. The umbilical cord branched to supply a bilobed allantoic sac. Small blood vessels and smooth muscle bundles were found within the stroma of the cord. Foci of squamous metaplasia occurred in the allanto-amnion and allantochorion. The interhemal membrane of the placenta was of the epitheliochorial type. Two different types of trophoblastic epithelium were seen. Most was of the simple columnar type and indented by fetal capillaries. However, there were also areolar regions with tall columnar trophoblast and these were more sparsely supplied with capillaries. The endometrium was well vascularised and richly supplied with actively secreting glands. These findings are consistent with the current view that Cetacea are nested within Artiodactyla as sister group to the hippopotamids.

da Silva, Vera MF; Carter, Anthony M; Ambrosio, Carlos E; Carvalho, Ana F; Bonatelli, Marina; Lima, Marcelo C; Miglino, Maria Angelica

2007-01-01

194

Methylmercury exposure affects motor performance of a riverine population of the Tapajós river, Brazilian Amazon  

Microsoft Academic Search

Gold mining and deforestation in the Brazilian Amazon are increasing mercury pollution of the extensive water system, exposing\\u000a riverine populations to organic mercury through fish-eating. The aim of the present study was to evaluate the effect of such\\u000a exposure on motor performance. This cross-sectional study was carried out in May?1996, in a village located on the banks of\\u000a the Tapajs

J. Dolbec; D. Mergler; C.-J. Sousa Passos; S. Sousa de Morais; J. Lebel

2000-01-01

195

Characteristics and spatio-temporal variability of the Amazon River Basin Water Budget  

Microsoft Academic Search

The spatio-temporal variations of the water budget components in the Amazon region are investigated by using a combination of hydrometeorological observations and moisture fluxes derived from the NCEP\\/NCAR reanalyses, for the period 1970–1999. The key new finding of this study identifies the major differences in the water balance characteristics and variability between the northern and southern parts of the basin.

Jose A. Marengo

2005-01-01

196

NEW LOCALITIES FOR THE BLACK-FACED HAWK (LEUCOPTERNIS MELANOPS) SOUTH OF THE AMAZON RIVER AND DESCRIPTION OF THE IMMATURE PLUMAGE OF THE WHITE-BROWED HAWK (LEUCOPTERNIS KUHLI)  

Microsoft Academic Search

The Black-faced Hawk (Leucopternis melanops) and White-browed Hawk (L. kuhli) are forest- based, Amazonian raptors whose distributions have been considered to be mutually exclusive north and south of the Amazon River, respectively. The occurrence of L. melanops south of the river was first indicated by a specimen collected by A. M. Olalla on the lower Tapajos River 70 years ago.

FABIO SARUBBI; RAPOSO DO AMARAL; BRET M. WHITNEY

197

Human exposure to mercury due to goldmining in the Tapajos River basin, Amazon, Brazil: Speciation of mercury in human hair, blood and urine  

Microsoft Academic Search

To obtain the basic information on human exposure to mercury (Hg) due to gold mining activities in Amazon, total mercury (T-Hg) and methylmercury (MeI Ig) were determined for human hair, blood and\\/or urine samples collected from populations living in gold mining area and fishing villages upstream of the Tapajos River basin. Abnormally high levels of T-Hg were observed in hair

H. Akagi; O. Malm; F. J. P. Branches; Y. Kinjo; Y. Kashima; J. R. D. Guimaraes; R. B. Oliveira; K. Haraguchi; W. C. Pfeiffer; Y. Takizawa; H. Kato

1995-01-01

198

Composition of wax esters, triglycerides and diacyl glyceryl ethers in the jaw and blubber fats of the Amazon River dolphin ( Inia geoffrensis )  

Microsoft Academic Search

The lower jaw fat of the Amazon River dolphinInia geoffrensis contains 52.8% wax ester, 44.7% triglyceride and 2.5% diacyl glyceryl ether, while its dorsal blubber fat is >98% triglyceride.\\u000a Examination of the intact lipids, the derived fatty acids and the derived fatty alcohols by gas chromatography reveals that\\u000a the blubber triglycerides show characteristics of freshwater fish fats, but the jaw

R. G. Ackman; C. A. Eaton; Carter Litchfield

1971-01-01

199

Spatial and temporal rainfall variability near the Amazon-Tapajós confluence  

Microsoft Academic Search

Do the influences of river breezes or other mesoscale effects lead to a systematic river proximity bias in Amazon rainfall data? We analyzed rainfall for a network of 38 rain gauges located near the confluence of the Tapajós and Amazon rivers in the eastern Amazon Basin. Tipping bucket rain gauges worked adequately in the Amazon rainfall regime, but careful field

David R. Fitzjarrald; Ricardo K. Sakai; Osvaldo L. L. Moraes; Raimundo Cosme de Oliveira; Otávio C. Acevedo; Matthew J. Czikowsky; Troy Beldini

2008-01-01

200

The estuarine chemistry and isotope systematics of 234,238U in the Amazon and Fly Rivers  

USGS Publications Warehouse

Natural concentrations of 238U and ??234U values were determined in estuarine surface waters and pore waters of the Amazon and Fly (Papua New Guinea) Rivers to investigate U transport phenomena across river-dominated land-sea margins. Discharge from large, tropical rivers is a major source of dissolved and solid materials transported to the oceans, and are important in defining not only oceanic mass budgets, but also terrestrial weathering rates. On the Amazon shelf, salinity-property plots of dissolved organic carbon, pH and total suspended matter revealed two vastly contrasting water masses that were energetically mixed. In this mixing zone, the distribution of uranium was highly non-conservative and exhibited extensive removal from the water column. Uranium removal was most pronounced within a salinity range of 0-16.6, and likely the result of scavenging and flocculation reactions with inorganic (i.e., Fe/Mn oxides) and organic colloids/particles. Removal of uranium may also be closely coupled to exchange and resuspension processes at the sediment/water interface. An inner-shelf pore water profile indicated the following diagenetic processes: extensive (???1 m) zones of Fe(III) - and, to a lesser degree, Mn(IV) - reduction in the absence of significant S(II) concentrations appeared to facilitate the formation of various authigenic minerals (e.g., siderite, rhodocrosite and uraninite). The pore water dissolved 238U profile co-varied closely with Mn(II). Isotopic variations as evidenced in ??234U pore waters values from this site revealed information on the origin and history of particulate uranium. Only after a depth of about 1 m did the ??234U value approach unity (secular equilibrium), denoting a residual lattice bound uranium complex that is likely an upper-drainage basin weathering product. This suggests that the enriched ??234U values represent a riverine surface complexation product that is actively involved in Mn-Fe diagenetic cycles and surface complexation reactions. In the Fly River estuary, 238U appears to exhibit a reasonably conservative distribution as a function of salinity. The absence of observed U removal does not necessarily imply non-reactivity, but instead may record an integration of concurrent U removal and release processes. There is not a linear correlation between ??234U vs. 1/ 238U that would imply simple two component mixing. It is likely that resuspension of bottom sediments, prolonged residence times in the lower reaches of the Fly River, and energetic particle-colloid interactions contribute to the observed estuarine U distribution. The supply of uranium discharged from humid, tropical river systems to the sea appears to be foremost influenced by particle/water interactions that are ultimately governed by the particular physiographic and hydrologic characteristics of an estuary. ?? 2004 Elsevier Ltd. All rights reserved.

Swarzenski, P.; Campbell, P.; Porcelli, D.; McKee, B.

2004-01-01

201

The estuarine chemistry and isotope systematics of 234,238U in the Amazon and Fly Rivers  

NASA Astrophysics Data System (ADS)

Natural concentrations of 238U and ?234U values were determined in estuarine surface waters and pore waters of the Amazon and Fly (Papua New Guinea) Rivers to investigate U transport phenomena across river-dominated land-sea margins. Discharge from large, tropical rivers is a major source of dissolved and solid materials transported to the oceans, and are important in defining not only oceanic mass budgets, but also terrestrial weathering rates. On the Amazon shelf, salinity-property plots of dissolved organic carbon, pH and total suspended matter revealed two vastly contrasting water masses that were energetically mixed. In this mixing zone, the distribution of uranium was highly non-conservative and exhibited extensive removal from the water column. Uranium removal was most pronounced within a salinity range of 0-16.6, and likely the result of scavenging and flocculation reactions with inorganic (i.e., Fe/Mn oxides) and organic colloids/particles. Removal of uranium may also be closely coupled to exchange and resuspension processes at the sediment/water interface. An inner-shelf pore water profile indicated the following diagenetic processes: extensive (˜1 m) zones of Fe(III)—and, to a lesser degree, Mn(IV)—reduction in the absence of significant S(II) concentrations appeared to facilitate the formation of various authigenic minerals (e.g., siderite, rhodocrosite and uraninite). The pore water dissolved 238U profile co-varied closely with Mn(II). Isotopic variations as evidenced in ?234U pore waters values from this site revealed information on the origin and history of particulate uranium. Only after a depth of about 1 m did the ?234U value approach unity (secular equilibrium), denoting a residual lattice bound uranium complex that is likely an upper-drainage basin weathering product. This suggests that the enriched ?234U values represent a riverine surface complexation product that is actively involved in Mn-Fe diagenetic cycles and surface complexation reactions. In the Fly River estuary, 238U appears to exhibit a reasonably conservative distribution as a function of salinity. The absence of observed U removal does not necessarily imply non-reactivity, but instead may record an integration of concurrent U removal and release processes. There is not a linear correlation between ?234U vs. 1/238U that would imply simple two component mixing. It is likely that resuspension of bottom sediments, prolonged residence times in the lower reaches of the Fly River, and energetic particle-colloid interactions contribute to the observed estuarine U distribution. The supply of uranium discharged from humid, tropical river systems to the sea appears to be foremost influenced by particle/water interactions that are ultimately governed by the particular physiographic and hydrologic characteristics of an estuary.

Swarzenski, Peter; Campbell, Pamela; Porcelli, Don; McKee, Brent

2004-12-01

202

Sciadicleithrum juruparii n. sp. (Monogenea: Ancyrocephalidae) from the gills of Satanoperca jurupari (Heckel) (Osteichthyes: Cichlidae) in the Guamá River, Amazon Delta, Brazil.  

PubMed

Sciadicleithrum juruparii n. sp. is described from the gills of the Neotropical cichlid fish Satanoperca jurupari (Heckel) caught in the Guamá River, in the delta of the Amazon River, at Belém, Pará State, Brazil. Diagnostic characters of the new species are a basally articulated male copulatory organ with clockwise coils and an accessory piece; a ventral bar with a median process; similar hooklets; vagina in the form of a sclerotised tube; and a sinistral vaginal aperture with a sclerotised papilla lying in a small surface depression. It is the only species of Sciadicleithrum Kritsky, Thatcher & Boeger, 1989 with a medial projection on the ventral bar. PMID:22581249

de Melo, Marly de Fátima Carvalho; dos Santos, Jeannie Nascimento; Santos, Cláudia Portes

2012-06-01

203

Turbulent mixing in the Amazon River: The isotopic memory of confluences  

Microsoft Academic Search

Rivers continuously discharge dissolved material to the oceans. Dissolved compounds partially result from water–rock interactions, which produce a large range of water chemical and isotopic compositions. These waters are collected by rivers, that are commonly assumed to be well-mixed with regard to their different tributaries, as a result of turbulent dispersion. In this paper, we test this hypothesis on the

Julien Bouchez; Eric Lajeunesse; Jérôme Gaillardet; Christian France-Lanord; Poliana Dutra-Maia; Laurence Maurice

2010-01-01

204

Estimation of erosion and sedimentation yield in the Ucayali river basin, a Peruvian tributary of the Amazon River, using ground and satellite methods  

NASA Astrophysics Data System (ADS)

Since 2003, the works of HYBAM observatory (www.ore-hybam.org) has allowed to quantify with accuracy, precision and over a long period Amazon's main rivers discharges and sediments loads. In Peru, a network of 8 stations is regularly gauged and managed in association with the national meteorological and Hydrological service (SENAMHI), the UNALM (National Agrological University of La Molina) and the National Water Agency (ANA). Nevertheless, some current processes of erosion and sedimentation in the foreland basins are still little known, both in volumes and in localization. The sedimentary contributions of Andean tributaries could be there considerable, masking a very strong sedimentation in subsidence zones localized between the control points of the HYBAM's network. The development of spatial techniques such as the Altimetry and reflectance measurement allows us today to complete the ground's network: HYBAM's works have allowed establishing a relation between surface concentration and reflectance in Amazonian rivers (Martinez et al., 2009, Espinoza et al., 2012) and reconstituting water levels series (Calmant et al., 2006, 2008). If the difficulty of calibration of these techniques increases towards the upstream, their use can allow a first characterization of the tributaries contributions and sedimentation zones. At world level, erosion and sedimentation yields in the upper Ucayali are exceptional, favored by a marked seasonality in this region (Espinoza et al., 2009, Lavado, 2010, Pépin et al., 2010) and the presence of cells of extreme precipitation ("Hotspots") (Johnson et al., 1976, Espinoza et al, 2009a). The upper Ucayali drainage basin is a Piggyback where the River run with a low slope, parallel to the Andean range, deposing by gravity hundred millions a year of sands, silts and clays. In this work, we thus propose an estimation of sedimentation and erosion yield in the Ucayali river basin using ground and satellite methods.

Santini, William; Martinez, Jean-Michel; Guyot, Jean-Loup; Espinoza, Raul; Vauchel, Philippe; Lavado, Waldo

2014-05-01

205

Monitoring mercury exposure in reproductive aged women inhabiting the tapajós river basin, Amazon.  

PubMed

Among Amazonian communities, exposure to methylmercury is associated mainly with fish consumption that may affect fetal development in pregnant women. Therefore a temporal assessment was performed to assess the exposure of reproductive aged women to mercury who reside in the riparian communities of São Luís do Tapajós and Barreiras located in the Tapajós basin of the Brazilian Amazon from 1999 to 2012. The total mercury concentration in the 519 hair samples was assessed by cold vapor atomic absorption spectrometry. Data analysis showed that the average total mercury concentration decreased from 1.066 to 0.743 ?g/g in those years. In 1999 the proportion of volunteers with mercury levels ?10 ?g/g was approximately 68 %. In general, exposure to mercury decreased among women of reproductive age, but the potential risks to reproduction and human health is still an issue as 22 % of the woman continued showing high mercury levels (?10 ?g/g) in 2012. PMID:24789525

de Oliveira Corvelo, Tereza Cristina; Oliveira, Erika Abdon Fiquene; de Parijós, Amanda Magno; de Oliveira, Claudia Simone Baltazar; do Socorro Pompeu de Loiola, Rosane; de Araújo, Amélia A; da Costa, Carlos Araújo; de Lima Silveira, Luiz Carlos; da Conceição Nascimento Pinheiro, Maria

2014-07-01

206

New views on "old" carbon in the Amazon River: Insight from the source of organic carbon eroded from the Peruvian Andes  

NASA Astrophysics Data System (ADS)

rivers play a key role in the delivery of particulate organic carbon (POC) to large river systems and the ocean. Due to the extent of its drainage area and runoff, the Amazon River is one of Earth's most important biogeochemical systems. However, the source of POC eroded from the humid region of the Eastern Andes and the input of fossil POC from sedimentary rocks (POCfossil) remains poorly constrained. Here we collected suspended sediments from the Kosñipata River during flood events to better characterize Andean POC, measuring the nitrogen to organic carbon ratio (N/C), stable carbon isotopes (?13Corg) and radiocarbon (?14Corg). ?14Corg values ranged from -711‰ to -15‰, and significant linear trends between ?14Corg, N/C and ?13Corg suggested that this reflects the mixing of POCfossil with very young organic matter (?14Corg ~ 50‰) from the terrestrial biosphere (POCnon-fossil). Using N/C and ?14Corg in an end-member mixing analysis, we quantify the fraction of POCfossil (to within 0.1) and find that it contributes a constant proportion of the suspended sediment mass (0.37 ± 0.03%) and up to 80% of total POC. In contrast, the relative contribution of POCnon-fossil was variable, being most important during the rising limb and peak discharges of flood events. The new data shed light on published measurements of "old" POC (low ?14Corg) in Andean-fed tributaries of the Amazon River, with their ?14Corg and ?13Corg values consistent with variable addition of POCfossil. The findings suggest a greater persistence of Andean POC in the lowland Amazon than previously recognized.

Clark, K. E.; Hilton, R. G.; West, A. J.; Malhi, Y.; GröCke, D. R.; Bryant, C. L.; Ascough, P. L.; Robles Caceres, A.; New, M.

2013-05-01

207

FRESHWATER PRAWN FARMING IN GHER SYSTEMS IN SOUTHWEST BANGLADESH  

Microsoft Academic Search

The livelihoods of a large number of farmers are associated with freshwater prawn (Macrobrachium rosenbergii) farming in gher (modified rice fields with high, broad peripheral dikes) systems in southwest Bangladesh. Most farmers integrated prawn with fish and rice in their gher and followed extensive methods using low inputs. Although farmers have improved their social and economic conditions through prawn farming,

Nesar Ahmed; Janet H. Brown; James F. Muir

2008-01-01

208

Top-down, bottom-up and physical controls on diatom-diazotroph assemblage growth in the Amazon River Plume  

NASA Astrophysics Data System (ADS)

The nutrient-rich waters of the Amazon River Plume (ARP) support dense blooms of diatom-diazotroph assemblages (DDA) that introduce large quantities of new nitrogen to the planktonic ecosystem and, unlike other nitrogen-fixers, are likely to directly fuel vertical carbon flux. To investigate the factors controlling DDA blooms, we develop a five phytoplankton (cyanobacteria, diatoms, unicellular microbial diazotrophs, DDA, and Trichodesmium), two zooplankton model and embed it within a 1/6° resolution physical model of the tropical and subtropical Atlantic. The model generates realistic DDA blooms in the ARP and also exhibits basin-wide primary production, nitrogen fixation, and grazing rates consistent with observed values. By following ARP water parcels with synthetic Lagrangian drifters released at the river mouth we are able to assess the relative impacts of grazing, nutrient supply, and physical forcing on DDA bloom formation. DDA bloom formation is stimulated in the silica-rich water of the ARP by decreases in grazing pressure when mesozooplankton (which co-occur in high densities with coastal diatom blooms) concentrations decrease. Bloom termination is driven primarily by silica limitation of the DDA. In agreement with in situ data, this net growth niche for DDA exists in a salinity range from ~ 20-34 PSU, although this co-occurrence is coincidental rather than causative. Because net growth rates are relatively modest, bloom formation in ARP water parcels depends critically on the time spent in this ideal habitat, with high DDA biomass only occurring when water parcels spent > 23 days in the optimal habitat niche.

Stukel, M. R.; Coles, V. J.; Brooks, M. T.; Hood, R. R.

2013-08-01

209

Top-down, bottom-up and physical controls on diatom-diazotroph assemblage growth in the Amazon River plume  

NASA Astrophysics Data System (ADS)

The nutrient-rich waters of the Amazon River plume (ARP) support dense blooms of diatom-diazotroph assemblages (DDAs) that introduce large quantities of new nitrogen to the planktonic ecosystem and, unlike other nitrogen-fixers, are likely to directly fuel vertical carbon flux. To investigate the factors controlling DDA blooms, we develop a five phytoplankton (cyanobacteria, diatoms, unicellular microbial diazotrophs, DDAs, and Trichodesmium), two zooplankton model and embed it within a 1/6° resolution physical model of the tropical and subtropical Atlantic. The model generates realistic DDA blooms in the ARP and also exhibits basin-wide primary production, nitrogen fixation, and grazing rates consistent with observed values. By following ARP water parcels with synthetic Lagrangian drifters released at the river mouth we are able to assess the relative impacts of grazing, nutrient supply, and physical forcing on DDA bloom formation. DDA bloom formation is stimulated in the nitrogen-poor and silica-rich water of the ARP by decreases in grazing pressure when mesozooplankton (which co-occur in high densities with coastal diatom blooms) concentrations decrease. Bloom termination is driven primarily by silica limitation of the DDAs. In agreement with in situ data, this net growth niche for DDAs exists in a salinity range from ∼20-34 PSU, although this co-occurrence is coincidental rather than causative. Because net growth rates are relatively modest, bloom formation in ARP water parcels depends critically on the time spent in this ideal habitat, with high DDA biomass only occurring when water parcels spent >23 days in the optimal habitat niche.

Stukel, M. R.; Coles, V. J.; Brooks, M. T.; Hood, R. R.

2014-06-01

210

Association of calcium with colloidal particles and speciation of calcium in the Kalix and Amazon rivers  

NASA Astrophysics Data System (ADS)

A considerable amount of colloidally bound Ca has been detected in water samples from Amazonian rivers and the Kalix River, a sub-arctic boreal river. Fractionation experiments using several analytical techniques and processing tools were conducted in order to elucidate the matter. Results show that on average 84% of the total Ca concentration is present as free Ca. Particulate, colloidal and complexed Ca constitute the remaining 16%, of which the colloidal fraction is significant. Ultrafiltration experiments show that the colloidal fraction in the sampled Amazonian rivers and the Kalix River range between 1% and 25%. In both the Amazonian and the Kalix rivers the technique of cross-flow ultrafiltration was used to isolate particles and colloids. The difference in concentration measured with ICP-AES and a Ca ion-selective electrode in identical samples was used to define the free Ca concentration and thus indirectly the magnitude of the particulate, colloidal and complexed fractions. Results from the Kalix and Amazonian rivers are in excellent agreement. Furthermore, the results show that the colloidal concentrations of Ca can be greatly overestimated (up to 227%) when conventional analysis and calculation of ultrafiltration data is used due to retention of free Ca ions during the ultrafiltration process. Calculation methods for colloidal matter are presented in this work, using complementary data from ISE analysis. In the Kalix River temporal changes in the fractionation of Ca were studied before, during and after a spring-flood event. Changes in the size distribution of colloidally associated Ca was studied using FlFFF (Flow Field-Flow Fractionation) coupled on-line to a HR ICP-MS. The FlFFF-HR ICP-MS fractograms clearly show the colloidal component of Ca, supporting the ultrafiltration findings. During winter conditions the size distribution of colloidally associated Ca has a concentration maximum at ˜5 to 10 nm in diameter, shifting to smaller sizes (<5 nm) during and after the spring flood. This shift in size distribution follows a change in the river during this period from ironoxyhydroxy colloids being the most important colloidal carrier phase to humic substances during and after the spring flood. WHAM and NICA-Donnan models were used to calculate the amount of colloidally bound Ca. The results similar for both models, show that on average 16% of the Ca may be associated to a colloidal phase, which is in broad agreement with the measurements.

Dahlqvist, Ralf; Benedetti, Marc F.; Andersson, Karen; Turner, David; Larsson, Tobias; Stolpe, Björn; Ingri, Johan

2004-10-01

211

Seasonal effects of wastewater to the water quality of the Caeté river estuary, Brazilian Amazon.  

PubMed

Bragança's socioeconomic situation is highly dependent on estuarine and marine biological resources that are influenced by tidal cycles and climatology. Field measurements (hydrological, hydrodynamic and microbiological variables) were taken in the most urbanized zone from Caeté estuary to characterise the quality of the local environment. During the dry period, the estuary was more eutrophic and presented the highest temperature (30.5 degrees C in Oct./06), salinity (17 psu in Feb./07), pH (8.24 in Feb./07) and fecal coliform (> 1000 MPN/100 ml in Dec./06 and Feb./07) values. The phytoplankton Cyclotella meneghiniana, Coscinodiscus centralis and other r-strategist species were observed. The lack of basic hydric canalization was responsible for the local contamination, especially during the dry period when more concentrated wastewater from the city was emitted into the estuary, showing the human influence on the reduction of local estuarine water quality. In Bragança, the fishery is considered one of the main economic activities so, this contamination is worrisome because a large part of the local economy depends on biological resources and, thus, the contamination could negatively affect the environmental health of this Amazon ecosystem. PMID:20563427

Pereira, Luci C C; Monteiro, Marcela C; Guimarães, Danielly O; Matos, Jislene B; Costa, Rauquírio M da

2010-06-01

212

Correlation between river slope and meandering variability (obtained by DGPS data) and morphotectonics for two Andean tributaries of the Amazon river: the case of Beni (Bolivia) and Napo (Ecuador-Peru) rivers.  

NASA Astrophysics Data System (ADS)

The Beni river drains a catchment area of 282 000 km2 of which 40 percent are located in the Cordillera of the Bolivian and Peruvian Andes, and the rest in the Amazonian plain : the studied reaches runs from Guanay (Andean Piedmont) to Riberalta (junction with Madre de Dios river) that represents a distance by the river of 1055 km. The Napo river starts in the Ecuadorian Andes and leaves Ecuador in Nuevo Rocafuerte (27 400 km2) and enters in Peru until its junction with the Amazon river : the studied section runs from Misahualli (Andean Piedmont) to this junction, that represents a distance by the river of 995 km. The GPS data were acquired using a mobile GPS embarked on a boat and 4 fixed bases located along the Beni river, 6 along the Napo river and the two rivers profile calculated from post-treated differential GPS solutions. For the Beni river, two sectors were identified: - the upstream sector (~230 km) between Guanay (414 m) and 50 km downstream Rurrenabaque (245 m) is located in Andean Piedmont, which consists in a series of thrusts associated with anticlines and synclines (the subandean zone), and presents slope values range between 135 cm/km and 10 cm/km and an average index of sinuosity (IS) of 1.29, - the downstream sector (~ 820 km) which runs in Amazonian plain (until Riberalta -165 m-), is characterized by an average slope of 8 cm/km and an average IS of 2.06 (this sector is much more homogeneous and the Beni river shows a meandering channel). For the Napo River, three sectors were identified: - the first sector (~140 km) between Misahualli (401 m) and Coca (265 m), is located in Andean Piedmont (subandean zone) and presents slope values range between 170 cm/km and 30 cm/km and an average IS of 1.6, - the second sector (~250 km) between Coca (when the Napo river enters in the Amazonian plain) and Nuevo Rocafuerte (190 m), presents slope values range between 30 cm/km and 20 cm/km and an average IS of 1.2, and a convex-up shape profile corresponding to the preserved part of the Pastaza-Napo Megafan, not yet affected by headwater erosion, - the third sector (~600 km) between Nuevo Rocafuerte and the confluence with the Amazon river (101 m), where the Napo river flows through the quaternary deposits of the Pastaza-Napo Megafan, presents slope values ranging from 20 to 10 cm/km and an average IS of 1.2, and is characterized by a more classical concave-up shape profile. Our main results established using DGPS data (an important difference between the slope and IS averages of the Napo and the Beni rivers in their Amazonian part, respectively ~20 cm/km and ~8 cm/km, ie a ratio ~2.5, 1.2 and 2.06, ie a ratio ~0.6) bring an additional explanation to the results obtained by the preceding authors, with balance methods, and confirm respectively the erosion and the sedimentation behaviour of the Napo and the Beni rivers.

Bourrel, L.; Darrozes, J.; Guyot, J.; Christophoul, F.; Bondoux, F.

2007-05-01

213

MERCURY IN FISH OF THE TAPAJÓS RIVER IN THE BRAZILIAN AMAZON  

Microsoft Academic Search

We studied total mercury (Hg) concentrations, as well as bioaccumulation and bioamplification of Hg in the ichtyofauna of three lakes located on the Tapajós River. Particular attention was paid to possible temporal and spatial variations in Hg levels. The results of two sampling campaigns corresponding to the rainy season (April-May\\/2000) and rising water season (January\\/2001) are presented. Bioamplification of Hg

D. Sampaio da Silva; M. Lucotte; M. Roulet; H. Poirier; D. Mergler; M. Crossa

214

Methane flux from the Amazon River floodplain: Emissions during rising water  

Microsoft Academic Search

During April and May of 1987, an extensive methane flux data set from Amazonian wetland habitats was collected during the wet season as river water levels were high and rising. This work extends measurements made in the dry season of 1985, when water levels were falling. A total of 284 flux measurements were made in the three primary floodplain environments

Karen B. Bartlett; Patrick M. Crill; Jose A. Bonassi; Jeffrey E. Richey; Robert C. Harriss

1990-01-01

215

Fish assemblages of the Casiquiare River, a corridor and zoogeographical filter for dispersal between the Orinoco and Amazon basins  

USGS Publications Warehouse

Aim: The aim of this study was to determine whether the Casiquiare River functions as a free dispersal corridor or as a partial barrier (i.e. filter) for the interchange of fish species of the Orinoco and Negro/Amazon basins using species assemblage patterns according to geographical location and environmental features. Location: The Casiquiare, Upper Orinoco and Upper Negro rivers in southern Venezuela, South America. Methods: Our study was based on an analysis of species presence/absence data and environmental information (11 habitat characteristics) collected by the authors and colleagues between the years 1984 and 1999. The data set consisted of 269 sampled sites and 452 fish species (> 50,000 specimens). A wide range of habitat types was included in the samples, and the collection sites were located at various points along the entire length of the Casiquiare main channel, at multiple sites on its tributary streams, as well as at various nearby sites outside the Casiquiare drainage, within the Upper Orinoco and Upper Rio Negro river systems. Most specimens and field data used in this analysis are archived in the Museo de Ciencias Naturales in Guanare, Venezuela. We performed canonical correspondence analysis (CCA) based on species presence/absence using two versions of the data set: one that eliminated sites having < 5 species and species occurring at < 5 sites; and another that eliminated sites having < 10 species and species occurring at < 10 sites. Cluster analysis was performed on sites based on species assemblage similarity, and a separate analysis was performed on species based on CCA loadings. Results: The CCA results for the two versions of the data set were qualitatively the same. The dominant environmental axis contrasted assemblages and sites associated with blackwater vs. clearwater conditions. Longitudinal position on the Casiquiare River was correlated (r2 = 0.33) with CCA axis-1 scores, reflecting clearwater conditions nearer to its origin (bifurcation of the Orinoco) and blackwater conditions nearer to its mouth (junction with the Rio Negro). The second CCA axis was most strongly associated with habitat size and structural complexity. Species associations derived from the unweighted pair-group average clustering method and pair-wise squared Euclidean distances calculated from species loadings on CCA axes 1 and 2 showed seven ecological groupings. Cluster analysis of species assemblages according to watershed revealed a stronger influence of local environmental conditions than of geographical proximity. Main conclusions: Fish assemblage composition is more consistently associated with local environmental conditions than with geographical position within the river drainages. Nonetheless, the results support the hypothesis that the mainstem Casiquiare represents a hydrochemical gradient between clearwaters at its origin and blackwaters at its mouth, and as such appears to function as a semi-permeable barrier (environmental filter) to dispersal and faunal exchanges between the partially vicariant fish faunas of the Upper Orinoco and Upper Negro rivers. ?? 2008 The Authors.

Winemiller, K. O.; Lopez-Fernandez, H.; Taphorn, D. C.; Nico, L. G.; Duque, A. B.

2008-01-01

216

Methane flux from the Amazon River floodplain: Emissions during rising water  

SciTech Connect

During April and May of 1987, an extensive methane flux data set from Amazonian wetland habitats was collected during the wet season as river water levels were high and rising. This work extends measurements made in the dry season of 1985, when water levels were falling. A total of 284 flux measurements were made in the three primary floodplain environments of open-water lakes and channels, floating grass mats, and flooded forests, along approximately 1,500 km of the central floodplain. Emissions (means and standard errors) were 74 {plus minus} 14 mg CH{sub 4}/m{sup 2}/d (open water), 201 {plus minus} 35 mg CH{sub 4}/m{sup 2}/d (grass mats), and 126 {plus minus} 20 mg CH{sub 4}/m{sup 2}/d (flooded forests). These values were not significantly different from the majority of those from 1985, in part due to the high variability in flux seen at both times. Although ebullition was a significant component of methane emissions at both periods, the frequency of bubbling and its contribution to total flux was lower during the period of rising water than during falling water. A prominent diurnal pattern in atmospheric methane concentrations was observed, with minimum levels of about 1.75 ppm at midday and a maximum of 2.12 ppm at about midnight. Given the relatively small season changes observed in flux at the two stages of the rivers hydrographic curve, earlier estimates of regional methane flux remain largely unchanged. Revision of global estimates of wetland methane sources based on these tropical data and recently published figures for northern peatlands indicated that tropical wetlands may be more important than previously suggested, but that wetland sources overall remain at approximately 110 Tg/yr.

Bartlett, K.B.; Crill, P.M. (College of William and Mary, Williamsburg, VA (USA)); Bonassi, J.A. (Universidade de Sao Paulo (Brazil)); Richey, J.E. (Univ. of Washington, Seattle (USA)); Harriss, R.C. (Univ. of New Hampshire, Durham (USA) NASA Langley Research Center, Hampton, VA (USA))

1990-09-20

217

Biology of Penaeid Prawns in Northern Australia,  

National Technical Information Service (NTIS)

The prawn fisheries of northern Australia are spread around 5000 km of coastline in some of the country's most isolated regions and were developed as recently as the late 1960s. The first major development followed surveys by CSIRO, the Queensland Governm...

B. J. Hill

1987-01-01

218

The ¹⁸O:¹⁶O of dissolved oxygen in rivers and lakes in the Amazon Basin: Determining the ratio of respiration to photosynthesis rates in freshwaters  

Microsoft Academic Search

The concentration and ¹⁸O:¹⁶O ratio of dissolved oxygen were measured for 23 rivers and lakes of the Amazon Basin during 1988, 1990, and 1991. With only two exceptions, the rivers and lakes had dissolved oxygen concentrations that were at 20-90% of atmospheric saturation levels. The δ¹⁸O of the dissolved oxygen ranged from 15 to 30% (vs. SMOW). The δ¹⁸O for

P. D. Quay; D. O. Wilbur; J. E. Richey; A. H. DEVOL; R. BENNER; B. R. FORSBERG

1995-01-01

219

Influence of ecological factors and of land use on mercury levels in fish in the Tapajós River basin, Amazon  

Microsoft Academic Search

Mercury (Hg) contamination of riparian communities and of environmental compartments of the Amazon can be directly related to the occupation of the territory. The objective of this study was to identify the characteristics of aquatic environments that are associated with high levels of Hg in ichthyofauna. Our research aimed at determining the influence of variables related to fish ecology, types

D. Sampaio da Silva; M. Lucotte; S. Paquet; R. Davidson

2009-01-01

220

The Pan-Amazonian Ucayali Peneplain, late Neogene sedimentation in Amazonia, and the birth of the modern Amazon River system  

Microsoft Academic Search

We review the Neogene geologic history of lowland Amazonia in an attempt to focus attention on areas of agreement, as well as areas in dispute, in this research arena. We reinterpret pre-existing hypotheses, present new data, and discuss new insights intended to support a unified synthesis of the Amazon Basin as a single sedimentary basin, albeit on a vast scale,

Kenneth E. Campbell Jr.; Carl David Frailey; Lidia Romero-Pittman

2006-01-01

221

Raft River Geothermal Aquaculture Experiment. Phase II.  

National Technical Information Service (NTIS)

Channel catfish, tilapia and Malaysian prawns were cultured directly in geothermal water for approximately seven months at the Department of Energy, Raft River Geothermal Site, to evaluate the organisms throughout a grow-out cycle. Parameters evaluated in...

D. K. Campbell F. L. Rose J. C. Kent L. R. Watson J. F. Sullivan

1979-01-01

222

Mercury inputs into the Amazon Region, Brazil  

Microsoft Academic Search

Mercury inputs into the Brazilian Amazon ecosystem due to goldmining activities are quantified based on data from various Brazilian Mineral and Environmental Agencies as well as field works. Total losses of Hg were estimated to be 1.32 kg Hg\\/kg Au from which 45% are released into rivers and 55% into the atmosphere. Total Hg input to the Amazon may contribute

W. C. Pfeiffer; L. Drude de Lacerda

1988-01-01

223

A time series analysis of Prochilodus nigricans landings caught by small-scale fisheries in the lower stretch of the Amazon River.  

PubMed

We developed a time series analysis using data on curimatã (Prochilodus nigricans), which landed in Santarém, a small city located on the right banks of the Amazon River. A 10-year record of monthly average catches per day of P. nigricans was analyzed using forecasting procedures in the open-source software GRETL 1.7.8. We established two models from the identifications made with the correlograms of hyperparametrization and seasonal differences. The autoregressive terms of the model reach three years, indicating that individuals of the species are being caught around the age of three. This may indicate that the curimatãs in the landings at Santarém from 1992 to 2002 were more than two years old, potentially a sign of a lack of fishing pressure on the lower age groups. PMID:23644788

Santana, I F; Freitas, C E C

2013-02-01

224

(210)Pb and composition data of near-surface sediments and interstitial waters evidencing anthropogenic inputs in Amazon River mouth, Macapá, Brazil.  

PubMed

Activity profiles of excess (210)Pb determined in three sediment cores from Amazon River mouth, Macapá city, Brazil, provided the evaluation of sedimentation rates, contributing to a better knowledge of the hydrological conditions in the site that is the capital of Amapá State and is drained by the waters of the huge Amazon River. Chemical data were also determined in the sediments, allowing identify signatures coupled to anthropogenic inputs held in the past in Amapá State. Significant direct relationships between LOI (loss on ignition) and organic matter were found for all sediments profiles. Silica was found to be inversely related to organic matter in the three profiles; its decrease accompanied an increase on the specific surface of the sediments. This relationship was confirmed by a great number of inverse significant correlations among silica and oxides Na(2)O, K(2)O, CaO, MgO, Al(2)O(3), P(2)O(5), Fe(2)O(3) and MnO. It was possible to identify the role of organic matter on adsorption of several oxides in the core sediments profiles. Apparent sediment mass accumulation rates corresponding to values between 450 and 2510 mg cm(-2)yr(-1) were obtained, and are compatible with the results of others studies. The (210)Pb activities in one sampling point suggested the occurrence of anthropogenic inputs related to the initial period of the mining activities conducted in Serra do Navio, Amapá State, for the commercialization of Mn ores. This was reinforced by the abrupt fluctuations in chemical data obtained for the sediments and composition of the interstitial waters occurring there. The Atlantic hurricane activity also appeared to affect the sedimentation rates in the area, as two different values were recorded in each profile. PMID:21353731

Nery, José Reinaldo Cardoso; Bonotto, Daniel Marcos

2011-04-01

225

Rubber agroforests at the Tapajós river, Brazilian Amazon—environmentally benign land use systems in an old forest frontier region  

Microsoft Academic Search

Scientific and public attention concerned with natural rubber (Hevea brasiliensis) production in the Amazon has focused on the high-tech practice of double-grafted, leaf blight resistant and high-yielding rubber clones on the one hand, and the low-tech practice of extractive use of natural rubber stands on the other. The intermediate, traditional practice of enriching slash-and-burn plots with rubber trees and managing

Götz Schroth; Paulo Coutinho; Vicente H. F. Moraes; Ana Luisa Albernaz

2003-01-01

226

Water slope and discharge in the Amazon River estimated using the shuttle radar topography mission digital elevation model  

Microsoft Academic Search

We find that the standard deviation, hence error, of the water surface elevation data from the Shuttle Radar Topography Mission (SRTM) is 5.51 m for basin-wide, regional and local Amazon mainstem reaches. This error implies a minimum reach length of 733km in order to calculate a reliable water-surface slope. Resulting slopes are 1.92 +\\/- 0.19 cm\\/km for Manacapuru, 2.86 +\\/-

Gina LeFavour; Doug Alsdorf

2005-01-01

227

The influence of changes in lifestyle and mercury exposure in riverine populations of the Madeira River (Amazon Basin) near a hydroelectric project.  

PubMed

In the Amazon Basin, naturally occurring methylmercury bioaccumulates in fish, which is a key source of protein consumed by riverine populations. The hydroelectric power-plant project at Santo Antônio Falls allows us to compare the Hg exposure of riverine populations sparsely distributed on both sides of the Madeira river before the area is to be flooded. From 2009 to 2011, we concluded a population survey of the area (N = 2,008; representing circa 80% of community residents) that estimated fish consumption and mercury exposure of riverine populations with different degrees of lifestyle related to fish consumption. Fish samples from the Madeira river (N = 1,615) and 110 species were analyzed for Hg. Hair-Hg was significantly lower (p < 0.001) in less isolated communities near to the capital of Porto Velho (median 2.32 ppm) than in subsistence communities in the Cuniã Lake, 180 km from Porto Velho city (median 6.3 ppm). Fish Hg concentrations ranged from 0.01 to 6.06 µg/g, depending on fish size and feeding behavior. Currently available fish in the Madeira river show a wide variability in Hg concentrations. Despite cultural similarities, riparians showed hair-Hg distribution patterns that reflect changes in fish-eating habits driven by subsistence characteristics. PMID:24577285

Hacon, Sandra S; Dórea, José G; Fonseca, Márlon de F; Oliveira, Beatriz A; Mourão, Dennys S; Ruiz, Claudia M V; Gonçalves, Rodrigo A; Mariani, Carolina F; Bastos, Wanderley R

2014-03-01

228

Effect of Inclusion of Prawn and Mola on Water Quality and Rice Production in Prawn-Fish-Rice Culture System  

Microsoft Academic Search

A long term experiment for a period of sixteen weeks was conducted from August to November, 2005 to observe the effects of inclusion of prawn (Macrobrachium rosenbergii) and mola (Amblypharyngodon mola) on water quality and rice production. To achieve the target, four treatments each with three replications were set in the experiment. In all treatments, prawn was stocked with mola

Rohul Amin; M. Salauddin

2008-01-01

229

Microsatellite markers for the tambaqui (Colossoma macropomum, Serrasalmidae, Characiformes), an economically important keystone species of the Amazon River floodplain.  

PubMed

Colossoma macropomum is a keystone species of the Amazon floodplain, and is an important but severely overexploited commercial species. To provide tools for addressing ecological and conservation questions, we developed 14 highly polymorphic microsatellite markers that had between four and 21 alleles per locus in the 25 tested individuals. With the exception of comparisons involving the locus Cm1F5 that also showed heterozygosity deficiency, no pairs of loci were at linkage disequilibrium. Many of the microsatellite loci were also variable in three other serrasalmid species which span the phylogenetic depth of the Serrasalmidae. PMID:21564774

Santos, Maria D Conceição F; Hrbek, Tomas; Farias, Izeni P

2009-05-01

230

Morphobiological aspects of Rhodnius brethesi Matta, 1919 (Hemiptera:Reduviidae) from the Upper and Middle Negro River, Amazon region of Brazil: I - scanning electron microscopy.  

PubMed

The occurrence of autochthonous cases of Chagas disease in the Amazon region of Brazil over recent decades has motivated an intensification of studies in this area. Different species of triatomines have been identified, and ten of these have be proven to be carriers of the parasite Trypanosoma cruzi or " cruzi-like " parasites. Studies conducted in the municipalities of Santa Isabel do Rio Negro and Barcelos, located on the Upper and Middle of the Negro River, microregion of Negro River, state of Amazonas have confirmed not only that Rhodnius brethesi is present in the palm tree Leopoldinia piassaba, but also that this insect was recognized by palm fiber collectors. A morphological study of eyes, inter-ocular and inter-ocellar regions, antennae, buccula, labrum, rostrum, stridulatory sulcus and feet, including the apex of the tibia, spongy fossette and ctenidium was conducted by scanning electron microscopy. The buccula and the stridulatory sulcus presented notable differences in specimens of different genera and also of different species. These data make it possible to suggest that the details presented in these structures can be included as diagnostic characteristics to be used in new dichotomous keys, thereby contributing towards studies of taxonomy and systematics and furnishing backing for comparative analysis of specimens collected from different localities. PMID:16444425

Dos Santos-Mallet, Jacenir Reis; Junqueira, Angela Cristina Verissimo; Moreira, Carlos José de Carvalho; Andrade, Zelia; Coura, José Rodrigues; Gonçalves, Teresa Cristina Monte

2005-12-01

231

Hydrologic benchmarking of meteorological drought indices at interannual to climate change timescales: a case study over the Amazon and Mississippi river basins  

NASA Astrophysics Data System (ADS)

Widely used metrics of drought are still derived solely from analyses of meteorological variables such as precipitation and temperature. While drought is generally a consequence of atmospheric anomalies, the impacts to society are more directly related to hydrologic conditions. The present study uses a standardized runoff index (SRI) as a proxy for river discharge and as a benchmark for various meteorological drought indices (scPDSI, SPI, SPEI_th, and SPEI_hg respectively). Only 12-month duration droughts are considered in order to allow a direct (no river routing) comparison between meteorological anomalies and their hydrological counterpart. The analysis is conducted over the Mississippi and Amazon river basins, which provide two contrasted test beds for evaluating drought indices at both interannual (using detrended data) and climate change (using raw data) timescales. Looking first at observations over the second half of the 20th century, the simple SPI based solely on precipitation is no less suitable than more sophisticated meteorological drought indices at detecting interannual SRI variations. Using the detrended runoff and meteorological outputs of a five-member single model ensemble of historical and 21th century climate simulations leads to the same conclusion. Looking at the 21st century projections, the response of the areal fraction in drought to global warming is shown to be strongly metric dependent and potentially overestimated by the drought indices which account for temperature variations. These results suggest that empirical meteorological drought indices should be considered with great caution in a warming climate and that more physical water balance models are needed to account for the impact of the anthropogenic radiative forcings on hydrological droughts.

Joetzjer, E.; Douville, H.; Delire, C.; Ciais, P.; Decharme, B.; Tyteca, S.

2013-12-01

232

Water quality changes in floodplain lakes due to the Amazon River flood pulse: Lago Grande de Curuaí (Pará).  

PubMed

Assurance of water quality for human consumption is essential for public health policies. In the Amazon floodplain, the seasonal water level variation causes periodic flooding of marginal areas that are usually used for settlements, agriculture and livestock. Therefore, the exchange of materials between the terrestrial and aquatic ecosystem affects the proportion of suspended and dissolved components in water and its physical-chemical characteristics, and consequently the quality of the water used by local people. Following this approach, the aim of this study is to evaluate changes in water quality in Lago Grande de Curuaí floodplain, Óbidos, Pará in response to the flood pulse, during one hydrological year from 2003 to 2004, based on water use classes (according to National Water Agency 357/2005 resolution) using chlorophyll-a and dissolved oxygen concentration as parameters and the eutrophication index. Ordinary kriging was applied to interpolate chlorophyll-a and dissolved oxygen and to predict values at non sampled locations. Each location was then classified according to water use acceptable parameters and to Carlson Trophic State Index modified by Toledo to map lake water classes and trophic status. The result showed that Lago Grande de Curuaí floodplain is a supereutrophic system, with levels of dissolved oxygen and chlorophyll-a not suitable for human supply during the receding water phase. These areas are located near the riverine communities, which can cause health problems due to the presence of potentially toxic algae. Therefore, monitoring water quality in Amazon lakes is essential to ensure the availability has appropriate quality for human and animal supplies. PMID:21881783

Affonso, A G; Barbosa, C; Novo, E M L M

2011-08-01

233

Geothermal aquaculture: a guide to freshwater prawn culture  

SciTech Connect

Biological data of the Malaysian prawn, Macrobrachium rosenbergii, are summarized. A history on its rearing techniques is given, but through the use of geothermal water or industrial warm water effluent, its range can be expanded. The use of wasted geothermal water at the Oregon Institute of Technology for prawn ponds is noted. Pond management and design; the hatchery design and function for larval culture; and geothermal applications (legal aspects and constraints) are discussed. (MCW)

Hayes, A.; Johnson, W.C.

1980-05-01

234

Ultrastructural description of Ceratomyxa microlepis sp. nov. (phylum Myxozoa): a parasite infecting the gall bladder of Hemiodus microlepis, a freshwater teleost from the Amazon River.  

PubMed

A new ceratomyxid parasite was examined for taxonomic identification, upon being found infecting the gall bladder of Hemiodus microlepis (Teleostei: Hemiodontidae), a freshwater teleost collected from the Amazon River, Brazil. Light and transmission electron microscopy revealed elongated crescent-shaped spores constituted by two asymmetrical shell valves united along a straight sutural line, each possessing a lateral projection. The spores body measured 5.2 ± 0.4 µm (n = 25) in length and 35.5 ± 0.9 µm (n = 25) in total thickness. The lateral projections were asymmetric, one measuring 18.1 ± 0.5 µm (n = 25) in thickness and the other measuring 17.5 ± 0.5 µm (n = 25) in thickness. Two equal-sized subspherical polar capsules measuring 2.2 ± 0.3 µm in diameter were located at the same level, each possessing a polar filament with 5-6 coils. The sporoplasm was binucleate. Considering the morphometric data analyzed from the microscopic observations, as well as the host species and its geographical location, this paper describes a new myxosporean species, herein named Ceratomyxa microlepis sp. nov.; therefore representing the first description of a freshwater ceratomyxid from the South American region. PMID:23579792

Azevedo, Carlos; Rocha, Sónia; Casal, Graça; São Clemente, Sérgio Carmona; Matos, Patrícia; Al-Quraishy, Saleh; Matos, Edilson

2013-04-01

235

Ultrastructural description of Ceratomyxa microlepis sp. nov. (Phylum Myxozoa): a parasite infecting the gall bladder of Hemiodus microlepis, a freshwater teleost from the Amazon River  

PubMed Central

A new ceratomyxid parasite was examined for taxonomic identification, upon being found infecting the gall bladder of Hemiodus microlepis (Teleostei: Hemiodontidae), a freshwater teleost collected from the Amazon River, Brazil. Light and transmission electron microscopy revealed elongated crescent-shaped spores constituted by two asymmetrical shell valves united along a straight sutural line, each possessing a lateral projection. The spores body measured 5.2 ± 0.4 µm (n = 25) in length and 35.5 ± 0.9 µm (n = 25) in total thickness. The lateral projections were asymmetric, one measuring 18.1 ± 0.5 µm (n = 25) in thickness and the other measuring 17.5 ± 0.5 µm (n = 25) in thickness. Two equal-sized subspherical polar capsules measuring 2.2 ± 0.3 µm in diameter were located at the same level, each possessing a polar filament with 5-6 coils. The sporoplasm was binucleate. Considering the morphometric data analyzed from the microscopic observations, as well as the host species and its geographical location, this paper describes a new myxosporean species, herein named Ceratomyxa microlepis sp. nov.; therefore representing the first description of a freshwater ceratomyxid from the South American region.

Azevedo, Carlos; Rocha, Sonia; Casal, Graca; Clemente, Sergio Carmona Sao; Matos, Patricia; Al-Quraishy, Saleh; Matos, Edilson

2013-01-01

236

Flooding dynamics on the lower Amazon floodplain  

NASA Astrophysics Data System (ADS)

We analyzed flooding dynamics of a large floodplain lake in the lower reach of the Amazon River for the period between 1995 through 2010. Floodplain inundation was simulated using the LISFLOOD-FP model, which combines one-dimensional river routing with two-dimensional overland flow, and a local hydrological model. Accurate representation of floodplain flows and inundation extent depends on the quality of the digital elevation model (DEM). We combined digital topography (derived from the Shuttle Radar Topography Mission) with extensive floodplain echo-sounding data to generate a hydraulically sound DEM. Analysis of daily water balances revealed that the dominant source of inflow alternated seasonally among direct rain and local runoff (October through January), Amazon River (March through August), and seepage (September). As inflows from the Amazon River increase during the rising limb of the hydrograph, regional floodwaters encounter the floodplain partially inundated from local hydrological inputs. At peak flow the floodplain routes, on average, 2.5% of the total discharge for this reach. The falling limb of the hydrograph coincides with the locally dry period, allowing seepage of water stored in sediments to become a dominant source. The average annual inflow from the Amazon River was 58.8 km3 (SD = 33.5), representing more than three thirds (80%) of inputs from all sources, with substantial inter-annual variability. The average annual net export of water from the floodplain to the Amazon River was 7.9 km3 (SD = 2.7).

Rudorff, C.; Melack, J. M.; Bates, P. D.

2013-05-01

237

Influence of the Amazon River on dissolved and intra-cellular metal concentrations in Trichodesmium colonies along the western boundary of the sub-tropical North Atlantic Ocean  

NASA Astrophysics Data System (ADS)

Despite the ecological importance of Trichodesmium spp. for the global oceanic nitrogen budget, there is limited information on their trace metal composition in field samples. We report dissolved (<0.22 ?m) metal concentrations measured in surface waters (Ag, Cd, Co, Cu, Fe, Mo, Ni, P, Pb and V) and in the total and the intracellular pool (Ag, Al, Cd, Co, Cu, Fe, Mn, Mo, Ni, P, Pb, V) of Trichodesmium populations collected in the western subtropical North Atlantic Ocean (April-May 2003) within the influence of the Amazon River plume. Dissolved element distributions were strongly influenced by the River discharge, with concentrations of some elements varying directly (i.e. Cd, Mo and V) or inversely (Ag, Co, Cu, Fe, Ni, P and Pb) with surface salinity. Intracellular metal values to phosphorous ratios (mol:mol) for Cd, Co, Cu, Fe, Mn, Mo, Ni and V ranged from 9.0×10-6 for Cd to 4.4×10-2 for Fe. Although total metal composition was significantly correlated with the intracellular content in the Trichodesmium colonies for some elements (e.g., Co, Cu, V), metal pools in the phytoplankton did not co-vary with the dissolved metal concentrations, suggesting that water column measurements may not be good predictors of the intracellular metal concentrations. The impact of physical parameters and bioactive elements on biological processes in Trichodesmium such as nitrogen fixation, carbon drawdown and biomass production was explored by using a principal component analysis test (PCA). The analysis indicates that the biological drawdown of dissolved inorganic carbon (DIC) by Trichodesmium seems to be influenced by the internal content of Fe, Co, Cd, Cu and Mn, while nitrogen fixation seems more influenced by the internal concentration of Mo, Ni and V and by the dissolved phosphorous concentrations.

Tovar-Sanchez, A.; Sañudo-Wilhelmy, S. A.

2010-08-01

238

Influence of the Amazon River on dissolved and intra-cellular metal concentrations in Trichodesmium colonies along the western boundary of the sub-tropical North Atlantic Ocean  

NASA Astrophysics Data System (ADS)

Despite the ecological importance of Trichodesmium spp. for the global oceanic nitrogen budget, there is limited information on their trace metal composition in field samples. We report dissolved (<0.22 ?m) metal concentrations measured in surface waters (Ag, Cd, Co, Cu, Fe, Mo, Ni, P, Pb and V) and in the total and the intracellular pool (Ag, Al, Cd, Co, Cu, Fe, Mn, Mo, Ni, P, Pb, V) of Trichodesmium populations collected in the western subtropical North Atlantic Ocean (April-May 2003) within the influence of the Amazon River plume. Dissolved element distributions were strongly influenced by the River discharge, with concentrations of some elements varying directly (i.e. Cd, Mo and V) or inversely (Ag, Co, Cu, Fe, Ni, P and Pb) with surface salinity. Intracellular metal values to phosphorous ratios (mol:mol) for Cd, Co, Cu, Fe, Mn, Mo, Ni and V ranged from 9.0 × 10-6 for Cd to 4.4 × 10-2 for Fe. Although total metal composition was significantly correlated with the intracellular content in the Trichodesmium colonies for some elements (e.g., Co, Cu, V), metal pools in the phytoplankton did not co-vary with the dissolved metal concentrations, suggesting that water column measurements may not be good predictors of the intracellular metal concentrations. The impact of physical parameters and bioactive elements on biological processes such as nitrogen fixation, carbon drawdown and biomass production in Trichodesmium colonies was explored by using a principal component analysis test (PCA). The analysis indicated that the biological drawdown of dissolved inorganic carbon (DIC) by Trichodesmium seems to be influenced by the internal content of Fe, Co, Cd, and Cu, while nitrogen fixation seems more influenced by mixed layer depth and dissolved Fe and Ni concentrations.

Tovar-Sanchez, A.; Sañudo-Wilhelmy, S. A.

2011-01-01

239

Inverse mercury and selenium concentration patterns between herbivorous and piscivorous fish in the Tapajos River, Brazilian Amazon.  

PubMed

We evaluated the levels of selenium and mercury in five fish species commonly eaten by local populations of the Brazilian Amazon. Fish specimens were sampled in two lotic and three lentic areas at two different phases of the hydrological cycle. Analyses of Carbon and Nitrogen stable isotopes allowed us to confirm the trophic levels of the fish species (one herbivorous, two omnivorous and two piscivorous) and verify that these levels remained unchanged with the habitats and the season. The levels of selenium and mercury in fish varied from 50ng/g to 1006ng/g and from 17ng/g to 3502ng/g respectively. For both seasons, fish from lotic ecosystems presented higher selenium concentrations. An inverse pattern was observed between selenium and mercury concentrations within the trophic chain, and this in both seasons. Indeed, the highest mean concentrations of selenium and lowest mean concentrations of mercury were measured in the herbivorous species and the opposite in the piscivorous species. Our results unequivocally demonstrate that local riverside populations will maximize the selenium health benefits of eating fish while minimizing their risk of being chronically exposed to mercury by preferentially consuming herbivorous species and to some extent omnivorous species, while avoiding piscivorous species. PMID:23921221

Sampaio da Silva, D; Lucotte, M; Paquet, S; Brux, G; Lemire, M

2013-11-01

240

Relative prawn production and benthic macroinvertebrate densities in unfed, organically fertilized, and fed pond systems  

Microsoft Academic Search

Relative prawn production rates in unfed, organically fertilized, and fed pond systems were evaluated. Populations of benthic macroinvertebrates that potentially serve as forage organisms in these systems were also evaluated and compared with ponds without prawns to evaluate forage preferences. Juvenile prawns (x? = 0.36 ± 0.02 g) were stocked into nine 0.04 ha ponds at a density of 39

James H Tidwell; Shawn D Coyle; Carl D Webster; John D Sedlacek; Paul A Weston; Wanda L Knight; Sankie J Hill; Louis R D'Abramo; William H Daniels; Marty J Fuller

1997-01-01

241

Total basin discharge for the Amazon and Mississippi River basins from GRACE and a land-atmosphere water balance  

Microsoft Academic Search

Freshwater discharge along continental margins is a key Earth system variable that is not well monitored globally. Here we propose a method for estimating monthly river basin outflows based on the use of new GRACE satellite estimates of terrestrial water storage changes in a coupled land-atmosphere water balance. Using GRACE land water storage changes (which include changes in groundwater storage)

T. H. Syed; J. S. Famiglietti; J. Chen; M. Rodell; S. I. Seneviratne; P. Viterbo; C. R. Wilson

2005-01-01

242

The M2 tide on the Amazon shelf  

Microsoft Academic Search

As part of A Multidisciplinary Amazon Shelf Sediment Study (AMASSEDS), moored and shipboard current measurements made over the Amazon shelf during 1990-1991 have been analyzed to determine the dominant semidiurnal tidal constituent, the M2. These results have been combined with coastal sea level data from within the Amazon and Para Rivers, the adjacent shelf, and with satellite-derived tidal elevation data

Robert C. Beardsley; Julio Candela; Richard Limeburner; W. Rockwell Geyer; Steven J. Lentz; Belmiro M. Castro; David Cacchione; Nelson Carneiro

1995-01-01

243

Factors controlling nutrient concentrations in Amazon floodplain lakes  

Microsoft Academic Search

Nutrient chemistry in lakes of the central floodplain of the Amazon River is influenced by the relative mix of waters of river and local origin. At high water the lakes contained primarily river water, lake and river total nitrogen (TN) levels were similar, concentrations of total suspended solids (TSS), soluble reactive phosphorus (SRP), dissolved inorganic nitrogen (DIN), and total phosphorus

BRUCE R. FORSBERG; ALLAN H. DEVOL; JEFFREY E. RICHEY; LUIZ A. MARTINELLI; HUMBERTO DOS SANTOS

1988-01-01

244

Mercury methylation along a lake–forest transect in the Tapajós river floodplain, Brazilian Amazon: seasonal and vertical variations  

Microsoft Academic Search

The seasonal and spatial variations of net methylmercury production in sediments, soils and other sites were evaluated by assays with 203Hg at different depths and locations along a lake–forest transect at lake Enseada Grande, Tapajós river. Soil and sediment samples were taken at the surface and at different depths up to 9 cm. Fresh samples and acidified controls (1–3 g

Jean Remy Davée Guimarães; Marc Roulet; Marc Lucotte; Donna Mergler

2000-01-01

245

Solar aquaculture: A wintering technique for parent prawns  

SciTech Connect

A new method of providing the warm water needed for parent prawn wintering using solar energy is described. Using solar energy for prawn wintering involves heat collection, heat storage and temperature maintenance. The system designed provides sufficient energy for the safe wintering of prawns with suitable water temperatures. The temperature control facilities consist of three parts: a salt gradient solar pond, a shallow solar pond and a plastic house. The technique involves use of a shallow solar pond for collection and storage of heat. The average temperature in the wintering pond plastic house was 11 degrees C and the minimum temperature in January was 5.4 degrees C. This system allowed the wintering process to be conducted using solar energy alone and may extend aquaculture to higher latitudes. The ratio of net profit with the solar energy system over investment is 1.5 which makes it economically viable.

Cao Jin Long [Aquaculture Res. Inst., Shandong Province (China)

1994-09-01

246

ULTRASTRUCTURE OF THE PRAWN NERVE SHEATHS  

PubMed Central

The sheaths from freshly teased nerve fibers of the prawn exhibit a positive radial birefringence, consistent with their EM appearance as highly organized laminated structures composed of numerous thin cytoplasmic sheets or laminae bordered by unit membranes and arranged concentrically around the axon. The closely apposed membranes in these sheaths are fragile and often break down into rows of vesicles during fixation. Desmosome-like attachment zones occur in many regions of the sheath. The membranes within these zones resist vesiculation and thereby provide a "control" region for relating the type of vesicles formed in the fragile portions of the sheaths to the specific fixation conditions. It is proposed that during fixation the production of artifactual vesicles is governed by an interplay of three factors: (a) direct chemical action of the fixative on the polar strata of adjacent unit membranes, (b) osmotic forces applied to membranes during fixation, and (c) the pre-existing natural relations between adjacent membranes. It is found that permanganate best preserves the continuity of the membranes but will still produce vesicles if the fixative exerts severe osmotic forces. These results support other reports (19) of the importance of comparing tissues fixed by complementary procedures so that systematic artifacts will not be described as characteristic of the natural state.

Doggenweiler, C. F.; Heuser, John E.

1967-01-01

247

U-Pbdating on detrital zircon and Nd and Hf isotopes related to the provenance of siliciclastic rocks of the Amazon Basin: Implications for the origin of Proto-Amazonas River  

NASA Astrophysics Data System (ADS)

Previous provenance studies along the Amazonas river have demonstrated that the Amazon drainage basin has been reorganized since the Late Cretaceous with the uplift of the Andes and the establishment of the transcontinental Amazon fluvial system from Late Miocene to Late Pleistocene (Hoorn et al., 1995; Potter, 1997, Wesselingh et al., 2002; Figueiredo et al. 2009, Campbell et al., 2006, Nogueira et al. 2013).There is a lack of data from Eastern and Central Amazonia and only limited core data from the Continental Platform near to current Amazonas river mouth. Central Amazonia is strategic to unveil the origin of Amazonas River because it represents the region where the connection of the Solimões and Amazonas basin can be studied through time (Nogueira et al. 2013). Also, there is a shortage of information on the old Precambrian and Paleozoic sediment sources relative to Cretaceous and Miocene siliciclastic deposits of the Solimões and Amazonas basins. We collected stratigraphic data, detrital zircon U-Pb ages and Nd and Hf isotopes from Precambrian, Paleozoic, Cretaceous and Miocene siliciclastic deposits of the Northwestern border of Amazonas Basin. They are exposed in the Presidente Figueiredo region and in the scarps of Amazon River, and occur to the east of the Purus Arch. This Northwest-Southeast trending structural feature that divides the Solimões and Amazonas basin was active at various times since the Paleozoic. Detrital zircon ages for the Neoproterozoic Prosperança Formation yielded a complex signature, with different populations of Neoproterozoic (550, 630 and 800 Ma) and Paleoproterozoic to Archean sources (1.6, 2.1 and 2.6 Ga). Also Nd and Hf isotopes show two groups of TDM model ages between 1.4 to 1.53 Ga and 2.2 and 3.1 Ga. Sediments typical of Paleozoic sedimentary rocks of the Nhamundá and Manacapuru Formations revealed NdTDM model ages of 1.7, 2.2 and 2.7 Ga, but Hf isotopes and U-Pb zircon ages are more varied. They characterize a provenance dominated by Mesoproterozoic sources (1.0, 1.2 Ga) and subordinate Neoproterozoic(550-800 Ma) and Archean derivation (2.67 Ga). On the other hand, detrital zircon and Hf and NdTDM model ages for the Cretaceous Alter do Chão Formation yielded a unique Paleoproterozoicages between 2.0 and 2.3 Ga that can be correlated to sources derived from Maroni-Itacaiúnas and Central Amazonian basement provinces. The contribution of Precambrian and Paleozoic rocks exposed during the installationof the Amazonas drainage were probably significant .Such a large contribution from Neoproterozoic and Mesoproterozoic sources are not common in the proximal Amazon Craton basement .This new proposal open new perspectives to understand better the initial history of Amazon River with indication of the probable source areas during Late Cenozoic. Campbell Jr.; Frailey,C.D.; Romero-Pittman, G. 2006. The Pan-Amazonian UcayliPeneplain, late Neogenesedimentacion in Amazonia, and the Birth on the Modern Amazon River system.Palaeogeography,Palaeoclimatology, Palaeoecology. 239 (2006) 166-219 Figueiredo, J.,Hoorn, C., Van der Vem, P., Soares, E. 2009. Late Miocene onset of the Amazon River and the Amazon deep-sea fan: Evidence from the Fozdo Amazonas Basin. Geology, 37(7):619-622. Hoorn,C.; Guerrero, J.; Sarmiento, G. 1995. Andean tectonics as a cause for changing drainage patterns in Miocene Northern South America. Geology, v.23, p-237-240. Nogueira, A.C.R.; Silveira, R.R.; Guimarães, J.T.F. 2013. Neogene-Quaternary sedimentary and paleovegetation history of the eastern Solimões Basin, central Amazon region.Journal of South American Earth Sciences , v. 46, p. 89-99, 2013. Potter, P.E. 1997. The Mesozoic and Cenozoic paleodrainage of South America: a natural history. Journal of South American Earth Science.v.10. p.331-344 Wesselingh, F. P., et al., 2002. Lake-Pebas: a palaeocological reconstruction of a Miocene long-lived lake comples in Western Amazônia. Cainozoic Research 1 (1-2), 35-81.

Dantas, Elton Luiz; Silva Souza, Valmir; Nogueira, Afonso C. R.; Ventura Santos, Roberto; Poitrasson, Franck; Vieira Cruz, Lucieth; Mendes Conceição, Anderson

2014-05-01

248

Prawn landings and their relationship with the extent of mangroves and shallow waters in western peninsular Malaysia  

NASA Astrophysics Data System (ADS)

This study investigated changes in landings of all prawns, white prawns (mainly Penaeus merguiensis), mangrove extent, rainfall and the area of shallow water in western peninsular Malaysia. The most important state for both the landings of all prawns and white prawns was Perak where about 50% of all prawns and 35% of white prawns were landed. This is also the state with the largest, and most stable, extent of mangrove forest reserve (40?000 ha) and the largest area of shallow water (<5 m deep). Juvenile prawns from Perak may contribute to the landings of the nearby, adjacent states of Penang and Selangor, where the second highest landings for white prawns and total prawns, respectively, were found. The area of shallow water accounted for the greatest proportion of variation in landings of both all prawns and white prawns, and was the most significant variable fitted to multiple regressions of landings and coastal attributes (area of shallow water, mangrove area, length of coastline). Although there was a significant linear relationship between the landings of total prawns and mangrove area in both the 1980s and 1990s, this was not the case for the mangrove-dependent white prawns where a significant relationship was found only for the 1990s. Furthermore, landings of all prawns and white prawns in Selangor and Johor, where large losses of mangrove forest reserve have been recorded, appear to have been maintained or increased in the 1990s. The lack of a clear relationship between mangrove loss and prawn landings may be due to the migration of prawns from adjacent areas or that other attributes of mangroves, such as the length of mangrove-water interface, may be more important for the growth and survival of prawn populations than total area of mangroves.

Loneragan, N. R.; Ahmad Adnan, N.; Connolly, R. M.; Manson, F. J.

2005-04-01

249

Biology of penaeid prawns in the Suez Canal lakes  

Microsoft Academic Search

A study was made from January 1988 to March 1989 of the penaid prawns in the Great Bitter Lake and Lake Timsah located in the central part of the Suez Canal. Two species of Red Sea origin were investigated,Metapenaeus stebbingi andTrachypenaeus curvirostris; the former is by far the commoner. Both species displayed seasonal breeding over the period April to October,

A. A.-F. A. Gab-Alla; R. G. Hartnoll; A.-F. Ghobashy; S. Z. Mohammed

1990-01-01

250

Geochemistry of Amazon Basin supported by the ADCP measurements  

NASA Astrophysics Data System (ADS)

The Amazon River is the largest river in the world in volume of water. The basin has 6.915.000 Km2, but the last gauging station of Amazon River with regular and continuous measurements of discharge and sediment transport are Óbidos station with 4.670.000 Km2. Óbidos It is also the last stream gauge station with no or less tidal effect observed from Atlantic Ocean and registered. The Clim-Amazon Project has been done the first measurements with the purpose to acquire geochemical and hydrological informations downstream Óbidos station. The system studied has input data of sediments load after Óbidos, and the output of the system, at the Amazon River is at Macapá, close to the mouth of Amazon river. And flow the main tributaries along this way, between these two stations. To evaluate the geochemical source, the mass balance, and isotopic geochemistry is necessary the informations about the traces the main chemical elements, transported by the discharge from the main rivers of this area: Tapajos, Xingu, Paru, Jari, and the Amazon River at Monte Alegre and at Macapá. The ADCP - Acoustic Doppler Current Profile, equipment is used to get the stream discharge value at the moment of transect. But also get two more informations necessary for the geochemistry, and do the collecting points profiles. The place with most velocity at transect or the place with more backscatter. These informations are related with the sediment load of the river. Or which one can provide the better idea of how are transported the sediments at the measured transects. What was to observe was the main speed of the stream flow or the main backscatter sectional. The main purpose of the work is to show how works the correlation between the backscatter and speed data given by the ADCP, downstream Óbidos, and the main confluences of Amazon River, until Macapá. The ADCP measurements support the geochemical studies and the course of sediments load transported by the discharge of these rivers.

Paca, Victor; Moreira, Daniel; Monteiro, Achiles; Roig, Henrique

2014-05-01

251

Radium isotopes in coastal waters on the Amazon shelf  

Microsoft Academic Search

Radium isotope distributions on the continental shelf adjacent to the Amazon River are a complex function of salinity. The river and seawater endmembers for each radium isotope are low. Data from intermediate salinities plot as a highly scattered region above the conservative mixing line connecting the river and ocean endmembers. Spatial and temporal variability in sediment mixing and water residence

Willard S. Moore; Heather Astwood; Candice Lindstrom

1995-01-01

252

Rice fields to prawn farms: a blue revolution in southwest Bangladesh?  

Microsoft Academic Search

This paper examines freshwater prawn (Macrobrachium rosenbergii) farming in southwest Bangladesh where a large number of farmers have converted their rice fields to export oriented prawn\\u000a farms, locally known as gher. The gher design potentially provides good opportunities for diversified production of prawn, fish, rice and dike crops, that has brought\\u000a about a ‘blue revolution’. The average annual yield of

Nesar Ahmed; Edward H. Allison; James F. Muir

2010-01-01

253

Reproductive indices in natural nests of giant Amazon river turtles Podocnemis expansa (Schweigger, 1812) (Testudines, Podocnemididae) in the Environmental Protection Area Meanders of the Araguaia River.  

PubMed

A count was made of unhatched eggs and hatchling live and dead Podocnemis expansa turtles in 327 natural nests located on the beaches of the Environmental Protection Area (EPA) Meanders of the Araguaia River, to determine the percentage of hatching (94.63%), non-hatching (5.37%), survival (94.24%) and hatchling mortality (5.76%), and the average percentage of dead hatchlings during the 15 days in the nursery (0.97%). The mean number of hatchlings per nest was determined from the sum of the number of live and dead hatchlings divided by the total number of nests, while the mean number of eggs per nest was determined from the sum of live and dead hatchlings and unhatched eggs divided by the number of nests. These calculations yielded the following mean values: live hatchlings (88.98 ± 23.94), dead hatchlings (0.37 ± 0.93), unhatched eggs (5.07 ± 9.57), and total number of eggs (94.42 ± 21.30). The reproductive efficiency of the wild population of P. expansa can be affected by many environmental factors such as temperature, humidity and rainfall. In addition, man-made factors like the presence of chemicals in the water and the potential for infectious disease also have significant impact. The reproductive indices data obtained from this study are indispensable for future investigations of hatching anomalies. PMID:22437402

Alves-Júnior, J R F; Lustosa, A P G; Bosso, A C S; Balestra, R A M; Bastos, L F; Miranda, L B; Santos, A L Q

2012-02-01

254

Meander Migration in the Amazon Basin  

NSDL National Science Digital Library

This activity is targeted at introductory to upper division undergraduate courses in geomorphology or Earth system science. Students view time series animation of satellite imagery of part of the Amazon River basin (Rio Ucayali) which is actively migrating. Students are asked to describe verbally and with sketches the changes in channel location and channel features over time. They then compare the very active section of the river with other rivers nearby to get a sense of overall activity of meandering streams. This is prelude to hypothesis development and testing: why is the Rio Ucayali so active? Students explore some potential causes to explain the cause of lateral mobility of this river.

Hasbargen, Les

255

The {sup 18}O:{sup 16}O of dissolved oxygen in rivers and lakes in the Amazon Basin: Determining the ratio of respiration to photosynthesis rates in freshwaters  

SciTech Connect

The concentration and {sup 18}O:{sup 16}O ratio of dissolved oxygen were measured for 23 rivers and lakes of the Amazon Basin during 1988, 1990, and 1991. With only two exceptions, the rivers and lakes had dissolved oxygen concentrations that were at 20-90% of atmospheric saturation levels. The {delta}{sup 18}O of the dissolved oxygen ranged from 15 to 30% (vs. SMOW). The {delta}{sup 18}O for the lakes were the lowest at 15-23%. {delta}{sup 18}O < 24.2{per_thousand} (the atmospheric equilibrium value) are the result of photosynthetic oxygen input. The {delta}{sup 18}O of the rivers, in contrast, ranged from 24 to 30{per_thousand} > 24.2{per_thousand} resulted from respiration. Despite this clear difference between the {delta}{sup 18}O for rivers and lakes, these water bodies had similar levels of oxygen undersaturation. The {delta}{sup 18}O and dissolved oxygen concentrations are used to determine the ratio of community respiration (R) to gross photosynthesis (P) rates. R:P varied between {approximately}1 and 1.5 for lakes and between 1.5 and 4 for rivers. For all rivers and lakes, the measured {delta}{sup 18}O indicated the presence of photosynthetically produced oxygen, with the highest proportion occurring in lakes. The {delta}{sup 18}O of dissolved oxygen is a unique tracer of photosynthetic oxygen and provides, through a determination of R:P, a means of quantifying the heterotrophic state of freshwaters. 29 refs., 8 figs., 4 tabs.

Quay, P.D.; Wilbur, D.O.; Richey, J.E. [Univ. of Washington, Seattle, WA (United States)] [and others

1995-06-01

256

Quantitative and Qualitative Bacterial Flora of Giant Freshwater Prawn Macrobrachium rosenbergii Cultured in Earthen Ponds in Saudi Arabia  

Microsoft Academic Search

Quantitative and qualitative analyses of bacterial flora associated with the digestive tract of the giant freshwater prawn Macrobrachium rosenbergii cultured in earthen ponds of Saudi Arabia were carried out. Bacterial counts and flora of prawn-culture pond water, sediment, and prawn carapaces, along with important physicochemical parameters, were investigated, and the isolates were identified to the genus or species level. Total

M. Naim Uddin; A. H. Al-Harbi

2005-01-01

257

The impact of global positioning systems and plotters on fishing power in the northern prawn fishery, Australia  

Microsoft Academic Search

The impact of global positioning systems (GPS) and plotter systems on the relative fishing power of the northern prawn fishery fleet on tiger prawns (Penaeus esculentus Haswell, 1879, and P. semisulcatus de Haan, 1850) was investigated from commercial catch data. A generalized linear model was used to account for differences in fishing power between boats and changes in prawn abundance.

Carolyn M. Robins; You-Gan Wang; David Die

1998-01-01

258

Mercury and flooding cycles in the Tapajós river basin, Brazilian Amazon: The role of periphyton of a floating macrophyte ( Paspalum repens)  

Microsoft Academic Search

Methylmercury (MeHg) increases mercury (Hg) toxicity and is biomagnified in the trophic chain contaminating riverine Amazon populations. Freshwater macrophyte roots are a main site of Hg methylation in different Brazilian environments. Paspalum repens periphyton was sampled in four floodplain lakes during the dry, rainy and wet seasons for measurement of total Hg (THg), MeHg, Hg methylation potentials, %C, %N, ?13C,

Sérgio A. Coelho-Souza; Jean R. D. Guimarães; Márcio R. Miranda; Hugo Poirier; Jane B. N. Mauro; Marc Lucotte; Donna Mergler

2011-01-01

259

[Determination of 4-hexylresorcinol residues in prawns and crabs].  

PubMed

A method for the determination of 4-hexylresorcinol residues in prawn and crab meat by HPLC was developed. 4-Hexylresorcinol in prawn and crab meats was extracted with methanol using a homogenizer. The extract was diluted 4 times with water, and the diluted solution was passed through a C18 cartridge. The cartridge was washed with water and methanol-water (4 : 6), and then 4-hexylresorcinol was eluted with acetonitrile-0.1% phosphoric acid (55 : 45). The eluate was separated on a Capcell Pak C18 MG column with a mobile phase of acetonitrile-0.1% phosphoric acid (6 : 4) and 4-hexylresorcinol was determined with a UV detector (210 nm). Recoveries of 4-hexylresorcinol from commercial prawn and crab meats spiked at 1.0 and 10 microg/g were 82.4-92.2 and 88.9-91.8%, respectively. The determination limit of 4-hexylresorcinol was 1.0 microg/g in the samples. PMID:16440790

Nakazato, Mitsuo; Matsumoto, Hiroko; Kasuya, Yoko; Yasuda, Kazuo

2005-12-01

260

The use of customised probiotics in the cultivation of western king prawns (Penaeus latisulcatus Kishinouye, 1896).  

PubMed

This study presents a comprehensive review of probiotics usage in aquaculture with a specific emphasis on our research series on the effectiveness of the customised probiotics, Pseudomonas synxantha and Pseudomonas aeruginosa on the cultivation of western king prawns, Penaeus latisulcatus. These customised probiotics resulted from tests using five inhibition test methods between the bacteria isolated from two commercial probiotic products and Vibrio spp. isolated from western king prawns and other aquatic animals. The results proved the suitability and safety of these probiotics in the cultivation of western king prawns as they conclusively met all the essential requirements for appropriate probiotics. These probiotics have shown similar beneficial effects as the common prebiotics, Bio-Mos and beta-1,3-d-glucan on the growth, survival and immune responses of the prawns. The supplementation of probiotics with the formulated feed was more efficacious and more practical than direct application into the rearing media. The prawns exposed to the combined probiotics were healthier than those exposed to the individual probiotics. P. aeruginosa was more effective for improving prawn health than P. synxantha. The probiotic-fed prawns were not influenced by Vibrio harveyi at 10(3) CFU ml(-1) for 36 h of challenge. In conclusion, these customised probiotics can be used as appropriate probiotics and as a suitable replacement of antibiotics, for disease control in western king prawn aquaculture. PMID:19463955

Van Hai, Ngo; Buller, Nicky; Fotedar, Ravi

2009-08-01

261

Studies on the Functional Morphology and Ecology of the Atyid Prawns of Dominica  

Microsoft Academic Search

Six species of atyid prawns, representing five genera, occur in streams on the West Indian island of Dominica (figures 1-0). The ecology and habits of each are described and the relation of features of gross morphology to ways of life noted. Xiphocaris elongata, the most primitive living atyid, is a lightly built prawn whose adult habits are related to life

G. Fryer

1977-01-01

262

THE SUSTAINABLE LIVELIHOODS APPROACH TO THE DEVELOPMENT OF FRESHWATER PRAWN MARKETING SYSTEMS IN SOUTHWEST BANGLADESH  

Microsoft Academic Search

A conceptual framework, drawn from an approach to poverty reduction known as the Sustainable Livelihoods Approach (SLA), is applied to understanding the role of freshwater prawn (Macrobrachium rosenbergii) marketing systems in southwest Bangladesh. Freshwater prawn marketing potentially provides economic returns and social benefits to the rural poor. Although the potential benefits are great, a number of constraints were identified for

Nesar Ahmed; Catherine Lecouffe; Edward H. Allison; James F. Muir

2009-01-01

263

Freshwater prawn farming in Bangladesh: history, present status and future prospects  

Microsoft Academic Search

Within the overall agro-based economy in Bangla- desh, freshwater prawn (Macrobrachium rosenbergii) farming is currently one of the most important sec- tors of the national economy. During the last two dec- ades, its development has attracted considerable attention for its export potential. Freshwater prawn farming o¡ers diverse livelihood opportunities for a large number of rural poor. Although the prospects for

Nesar Ahmed; Harvey Demaine; James F Muir

2008-01-01

264

NASA Earth Observatory: Escape from the Amazon  

NSDL National Science Digital Library

As part of NASA's Earth Observatory, visitors to the Escape from the Amazon Web site are invited to "Accompany NASA scientists as they explore our world and unravel the mysteries of climate and environmental change." The Escape from the Amazon feature focuses on the buildup of carbon dioxide and its effect on global climate change, and the role that forests play in reversing this trend. Also included as the second part of the feature is an introduction to the large-scale Biosphere-Atmosphere Experiment in Amazonia. This feature highlights the enormity and significance of the Amazon River Valley and its effect on global climate. This Web site is a great outreach and educational tool offered by NASA and should be interesting to lay readers, scientists, and teachers. Several great graphics help to illustrate the information provided.

Lindsey, Rebecca.; Simmon, Robert.

265

Expedition to Peruvian Andes Confirms the Source of the Amazon  

NSDL National Science Digital Library

A US-led, National Geographic Society expedition says it has confirmed the location for the exact source of the Amazon River. The source lies on a 5,597 meter high peak called Nevado Mismi in the Peruvian Andes. The National Geographic team had established Mismi as the river's source in 1971, but in recent years the possibility had been raised that the actual source was at another mountain. Pinpointing the Amazon's source was made possible through use of modern geographic information systems. This week's In the News investigates the geography and conservation issues of the mighty river and its basin.

Sanders, Hilary C.

2000-01-01

266

The status of infectious disease in the Amazon region.  

PubMed

The Amazon River basin region is a vast territory with an area >7 million km2, encompassing parts of 9 South American countries: Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname, and Venezuela. The Amazon River, the longest river in the world, traverses the region from west to east, fed by multiple tributaries. The region also contains the largest tropical rainforest in the world, situated on a massive plain whose altitude is near sea level. With a climate characterized by high temperatures and humidity and copious rainfall, the region has the densest and most varied ecosystem in the world. PMID:19331757

Tauil, Pedro Luiz

2009-04-01

267

Methylmercury in hair samples from different riverine groups, Amazon, Brazil  

Microsoft Academic Search

The present study was aimed to evaluate comparatively the levels of methylmercury (MeHg) in human hair, collected from different groups of Amazonian populations exposed to contamined fish. The study was undertaken in fishing villages and gold mining areas, mainly in the Tapajós and Madeira river basins, two of the main tributaries of Amazon river. The study population included 125 hair

H. A. Kehrig; O. Malm; H. Akagi

1997-01-01

268

Distribution and partition of total mercury in waters of the Tapajós River Basin, Brazilian Amazon 1 The present investigation is part of an ongoing study, the CARUSO project (CRDI-UFPa-UQAM), initiated to determine the sources, fate and health effects of the presence of MeHg in the area of the Lower Tapajós. 1  

Microsoft Academic Search

Filtered water and particulate burdens of Hg (0.43–2.81 ng\\/l and 0.28–13.13 ng\\/l, respectively) in the Tapajós River (Brazilian Amazon) are one order of magnitude lower than previously reported concentrations in Amazonian waters. Hg content in the water column is influenced by the amount of particulate matter and is independent from upstream goldmining activities. The particulate load of Hg in the

M Roulet; M Lucotte; R Canuel; I Rheault; S Tran; Y. G De Freitos Gog; N Farella; R Souza do Vale; C. J Sousa Passos; E De Jesus da Silva; D Mergler; M Amorim

1998-01-01

269

Fishing Effort and Catch Composition of Urban Market and Rural Villages in Brazilian Amazon  

Microsoft Academic Search

The management of small-scale freshwater fisheries in Amazon has been based usually on surveys of urban markets, while fisheries of rural villages have gone unnoticed. We compared the fishing characteristics (catch, effort and selectivity) between an urban market and five small villages in the Lower Tocantins River (Brazilian Amazon), downstream from a large reservoir. We recorded 86 and 601 fish

Gustavo Hallwass; Priscila Fabiana Lopes; Anastacio Afonso Juras; Renato Azevedo Matias Silvano

2011-01-01

270

Spatial and temporal rainfall variability near the Amazon-Tapajós confluence  

NASA Astrophysics Data System (ADS)

Do the influences of river breezes or other mesoscale effects lead to a systematic river proximity bias in Amazon rainfall data? We analyzed rainfall for a network of 38 rain gauges located near the confluence of the Tapajós and Amazon rivers in the eastern Amazon Basin. Tipping bucket rain gauges worked adequately in the Amazon rainfall regime, but careful field calibration and comparison with collocated conventional rain gauges were essential to incorporate daily totals from our array into regional maps. Stations very near the large rivers miss the afternoon convective rain, as expected if a river breeze promotes subsidence over the river, but paradoxically, this deficiency is more than compensated by additional nocturnal rainfall at these locations. The NOAA Climate Prediction Center (CPC) Morphing technique (CMORPH) passive infrared inferred rainfall data do an adequate job of describing medium scale variability in this region, but some localized breeze effects are not resolved at 0.25° resolution. For areas inland from the rivers, nocturnal rainfall contributes less than half of total precipitation. A large-scale rainfall increase just to the west of Santarém manifests itself locally as a `tongue' of enhanced rain from along the wide area of open water at the Tapajós-Amazon confluence. The Amazon River breeze circulation affects rainfall more than does the Tapajós breeze, which moves contrary to the predominant wind. East of the riverbank, the effects of the Tapajós breeze extend only a few kilometers inland. Rainfall increases to the north of the Amazon, possibly the result of uplift over elevated terrain. Dry season rainfall increases by up to 30% going away from the Amazon River, as would be expected given breeze-induced subsidence over the river.

Fitzjarrald, David R.; Sakai, Ricardo K.; Moraes, Osvaldo L. L.; Cosme de Oliveira, Raimundo; Acevedo, OtáVio C.; Czikowsky, Matthew J.; Beldini, Troy

2008-03-01

271

The Vine Trust's Amazon Hope boats--providing a dental service on the Amazon.  

PubMed

The Vine Trust's Amazon Hope Project is a medical and dental programme providing healthcare to communities along the Amazon River in Peru. Volunteers from the UK and other countries work alongside Peruvian staff employed by their partner organization, Union Biblica del Peru, to provide a health service from a boat which serves communities on several tributaries who otherwise would have no other access to care. The dental programme involves a basic restorative and extraction service, with scope to develop a preventive programme. Clinical Relevance: Dentists'and DCPs' skills are transferable globally: this article illustrates how one volunteer dental project is working to provide relevant and sustainable dental health care in the Amazon jungle. PMID:23505857

Mason, Shona M C

2013-01-01

272

Carbon isotopic composition of Amazon shelf sediments  

SciTech Connect

The distribution of carbon isotopes in Amazon shelf sediment is controlled by the same processes that are forming the modern subaqueous delta. The terrestrial (-27 to -25 per thousand) isotopic carbon signal observed in surficial sediments near the river mouth extends over 400 km northwest along the shelf. Terrestrial carbon is associated with areas of rapid sediment accumulation (topset and foreset regions). A sharp boundary between terrestrial (-27 to -25 per thousand) and marine (-23 to -22 per thousand) isotopic carbon values in surficial sediments is associated with a change in depositional conditions (foreset to bottomset regions) and a decrease in sediment accumulation rate. POC water-column isotopic values (-27 per thousand) near the river mouth are similar to the underlying surficial-sediment TOC isotopic values, but POC water-column samples collected 20 km off the river mouth have marine carbon isotopic values (-22 to -19 per thousand) and differ from the underlying surficial-sediment TOC isotopic values. These water column observations are related to variations in turbidity and productivity. Down-core isotopic variation is only observed in cores taken in areas of lower sediment accumulation rates. These observations indicate that the organic carbon in Amazon shelf sediment is dominantly terrestrial in composition, and the location of deposition of this carbon is controlled by modern processes of sediment accumulation. The modern Amazon shelf is similar to large clinoform shale deposits of the Cretaceous in North America. Thus, the stratigraphic setting may help predict the isotopic variations of carbon in ancient deposits.

Showers, W.J.; Angle, D.G.; Nittrouer, C.A.; Demaster, D.J.

1985-02-01

273

Biochemical Stress Responses in Tissues of the Prawn Macrobrachium malcolmsonii on Exposure to Endosulfan  

Microsoft Academic Search

This study was conducted to investigate the induction of biochemical stress responses in Macrobrachium malcolmsonii following exposure to endosulfan and to determine the most sensitive parameter of endosulfan-induced stress in this species of prawn. Intermolt juvenile prawns were exposed to three sublethal concentrations of endosulfan (10.6, 16.0, and 32.0 ng\\/L) for a period of 21 days. Samples were taken from

P. Saravana Bhavan; P. Geraldine

2001-01-01

274

Gut microflora of two saltmarsh detritivore thalassinid prawns, Upogebia africana and Callianassa kraussi  

Microsoft Academic Search

The presence and digestive capabilities of bacteria associated with the digestive systems and habitats of two saltmarsh-burrowing\\u000a detritivore thalassinid prawns (Upogebia africana andCallianassa kraussi) was examined.U. africana is a filter-feeding prawn inhabiting muddy deposits, whereasC. kraussi, a deposit feeder, inhabits coarser more sandy deposits. Scanning electron microscopy was used to examine the gut lining\\u000a and associated microflora and the nature

Jean M. Harris; Lindsay J. Seiderer; Michael I. Lucas

1991-01-01

275

Flooding and carbon dynamics on the lower Amazon floodplain  

NASA Astrophysics Data System (ADS)

The Amazon basin stores and cycles large quantities of water and carbon, and floodplains are an important part of these processes. In this dissertation, I studied the interactions of hydrological and biogeochemical processes over a large floodplain unit in the eastern Amazon, the Curuai floodplain. I combined digital topography derived from the Shuttle Radar Topography Mission with extensive echo-sounding data to generate a hydraulically correct digital elevation model. Floodplain inundation was simulated over a period of 15 years (1995-2010) using LISFLOOD-FP, which combines one-dimensional river routing with two-dimensional overland flow, and a local hydrological model. An accurate filling and drainage of the floodplain was achieved with quantification of changes in water elevation, flooding extent, and river-floodplain flows. Levee height and channel topography were the main controls of river-floodplain exchanges during high and low-water, respectively. The inflow from the Amazon River corresponded to 82% of annual inputs from all sources, with dominant sources of inflow varying seasonally among direct rain and local runoff (November), Amazon River (December through August) and groundwater seepage (September and October). A water balance analysis and concentrations and transformations of carbon from other studies on the central Amazon floodplain were used to compute the fluxes through the major pathways of carbon loss from the Curuai floodplain. Carbon dioxide outgassing represented 86% of the total carbon loss and its seasonal and spatial variability was further investigated. The seasonal changes in lake mixing patterns exerted an important control over both carbon dioxide production and gas transfer velocities. The range of spatial variation in carbon dioxide concentration was least at low water and largest at high water. Gas transfer coefficients that take into account both wind and heat fluxes at the lake's surface were approximately four times higher than values previously used in regional estimates of gas evasion from lakes on the Amazon floodplain.

Rudorff, Conrado de Moraes

276

Nile perch, Lates niloticus , predation on the freshwater prawn, Caridina nilotica , in the Nyanza Gulf, Lake Victoria, East Africa  

Microsoft Academic Search

The percentage of Nile perch, Lates niloticus, containing the prawn, Caridina nilotica, declined from 60–85%, for fish between 5 and 40 cm total length, to less than 10% for fish larger than 80 cm in length. The maximum number of prawns eaten by a Nile perch increased steadily, from 10 prawns for a fish in the 5–9.9 cm length group,

Nicholas F. Hughes

1992-01-01

277

Contribution of mangrove detritus to juvenile prawn nutrition: a dual stable isotope study in a Malaysian mangrove forest  

Microsoft Academic Search

Dual stable C and N ratio analyses of primary producers and prawns have clarified the important role of mangrove detritus\\u000a as the primary food source of juvenile prawns inhabiting the upper estuaries of the Matang mangrove swamp in Malaysia. The\\u000a contribution of mangrove carbon to prawn tissues, as high as 84%, decreased in the offshore direction, as the contribution\\u000a by

V. C. Chong; C. B. Low; T. Ichikawa

2001-01-01

278

Importance of estuarine mangroves to juvenile banana prawns  

NASA Astrophysics Data System (ADS)

Offshore catches of banana prawns, Penaeus merguiensis, are correlated with the extent of mangrove forests. However, recent evaluation has questioned whether the apparent relationship between juvenile penaeids and mangroves reflects specific utilisation of mangroves or just the use of shallow, organically rich, muddy habitats. We investigated this by focussing on juvenile P. merguiensis within 30 mangrove estuaries spanning 650 km of the coast of north-eastern Australia. We investigated a range of hierarchically clustered spatial scales and within-estuary spatial resolutions, as well as variables representing a variety of estuary structural factors, anthropogenic impacts, and particular hypotheses about the ways in which mangroves could influence P. merguiensis catch per unit effort (CPUE). Estuary to estuary differences, rather than climatic zone or the proximity of other estuaries, was the major large scale spatial influence on CPUE. At the among-estuaries scale mangrove extent appeared to influence CPUE but was extensively confounded with the effects of two non-mangrove variables; intertidal extent and substrate type. The fact that 3 alternative measures of connectivity with mangrove forests were not influential, points to the importance of the non-mangrove variables rather than mangrove extent. At the within-estuary scale, P. merguiensis CPUE was correlated with the extent of shallow water but not with mangrove variables. The spatial and temporal extent of sampling support a strong conclusion that factors associated with mangroves alone do not drive abundances of juvenile prawns. Nevertheless, despite being the dominant habitat, mangroves are only one of a mosaic of interacting habitats occurring in the tropical estuaries inhabited by juvenile penaeids (Sheaves, 2009), so causal relationships are complex and difficult to define unambiguously.

Sheaves, Marcus; Johnston, Ross; Connolly, Rod M.; Baker, Ronald

2012-12-01

279

In-Depth Tanscriptomic Analysis on Giant Freshwater Prawns  

PubMed Central

Gene discovery in the Malaysian giant freshwater prawn (Macrobrachium rosenbergii) has been limited to small scale data collection, despite great interest in various research fields related to the commercial significance of this species. Next generation sequencing technologies that have been developed recently and enabled whole transcriptome sequencing (RNA-seq), have allowed generation of large scale functional genomics data sets in a shorter time than was previously possible. Using this technology, transcriptome sequencing of three tissue types: hepatopancreas, gill and muscle, has been undertaken to generate functional genomics data for M. rosenbergii at a massive scale. De novo assembly of 75-bp paired end Ilumina reads has generated 102,230 unigenes. Sequence homology search and in silico prediction have identified known and novel protein coding candidate genes (?24%), non-coding RNA, and repetitive elements in the transcriptome. Potential markers consisting of simple sequence repeats associated with known protein coding genes have been successfully identified. Using KEGG pathway enrichment, differentially expressed genes in different tissues were systematically represented. The functions of gill and hepatopancreas in the context of neuroactive regulation, metabolism, reproduction, environmental stress and disease responses are described and support relevant experimental studies conducted previously in M. rosenbergii and other crustaceans. This large scale gene discovery represents the most extensive transcriptome data for freshwater prawn. Comparison with model organisms has paved the path to address the possible conserved biological entities shared between vertebrates and crustaceans. The functional genomics resources generated from this study provide the basis for constructing hypotheses for future molecular research in the freshwater shrimp.

Mohd-Shamsudin, Maizatul Izzah; Kang, Yi; Lili, Zhao; Tan, Tian Tian; Kwong, Qi Bin; Liu, Hang; Zhang, Guojie; Othman, Rofina Yasmin; Bhassu, Subha

2013-01-01

280

Proliferation of hydroelectric dams in the Andean Amazon and implications for Andes-Amazon connectivity.  

PubMed

Due to rising energy demands and abundant untapped potential, hydropower projects are rapidly increasing in the Neotropics. This is especially true in the wet and rugged Andean Amazon, where regional governments are prioritizing new hydroelectric dams as the centerpiece of long-term energy plans. However, the current planning for hydropower lacks adequate regional and basin-scale assessment of potential ecological impacts. This lack of strategic planning is particularly problematic given the intimate link between the Andes and Amazonian flood plain, together one of the most species rich zones on Earth. We examined the potential ecological impacts, in terms of river connectivity and forest loss, of the planned proliferation of hydroelectric dams across all Andean tributaries of the Amazon River. Considering data on the full portfolios of existing and planned dams, along with data on roads and transmission line systems, we developed a new conceptual framework to estimate the relative impacts of all planned dams. There are plans for 151 new dams greater than 2 MW over the next 20 years, more than a 300% increase. These dams would include five of the six major Andean tributaries of the Amazon. Our ecological impact analysis classified 47% of the potential new dams as high impact and just 19% as low impact. Sixty percent of the dams would cause the first major break in connectivity between protected Andean headwaters and the lowland Amazon. More than 80% would drive deforestation due to new roads, transmission lines, or inundation. We conclude with a discussion of three major policy implications of these findings. 1) There is a critical need for further strategic regional and basin scale evaluation of dams. 2) There is an urgent need for a strategic plan to maintain Andes-Amazon connectivity. 3) Reconsideration of hydropower as a low-impact energy source in the Neotropics. PMID:22529979

Finer, Matt; Jenkins, Clinton N

2012-01-01

281

Lead exposure in indigenous communities of the Amazon basin, Peru  

Microsoft Academic Search

Since 2006, three studies have reported elevated levels of lead (Pb) among the indigenous population of the Corrientes river, in the Amazon basin of Peru. Due to the large evidence of environmental pollution related to oil exploitation in the area, this activity has been suggested as the source of exposure. This study aimed to evaluate Pb levels in the population

Cynthia Anticona; Ingvar A. Bergdahl; Thomas Lundh; Yuri Alegre; Miguel San Sebastian

282

Mercury contamination in the Brazilian Amazon. Environmental and occupational aspects  

Microsoft Academic Search

Mercury (Hg) contamination of miners, riparian and Indian populations and fish in the Amazon region, due to gold extracting activities, has been studied. Samples of hair, urine, and blood of Indians and prospectors, and hair from riparian fish-eating population and fishes from Madeira river, respectively, were collected and analyzed by Cold Vapor, Atomic Absorption Spectrometry (CV-AAS) techniques. The results obtained

A. C. Barbosa; A. A. Boischio; G. A. East; I. Ferrari; A. Gonçalves; P. R. M. Silva; T. M. E. da Cruz

1995-01-01

283

The riverine silicon isotope composition of the Amazon Basin  

NASA Astrophysics Data System (ADS)

We present here the first large-scale study of riverine silicon isotope signatures in the Amazon Basin. The Amazon and five of its main tributaries were studied at different seasons of the annual hydrological cycle. The ?30Si signature of the dissolved silicon (DSi) exported to the estuary (weighted for DSi flux) for the period considered is estimated at +0.92‰. A river cross-section shows the homogeneity of the Amazon River regarding DSi concentration and isotope ratio. The biogenic silica (BSi) concentration measured in surface water from all rivers is generally small compared to the DSi reservoir but large variations exist between rivers. Very low isotope signatures were measured in the upper Rio Negro (?30Si = +0.05 ± 0.06‰), which we explain both by an equilibrium between clay formation and dissolution and by gibbsite formation. The Si isotope fractionation in the Andean tributaries and the Amazon main stem can be explained by clay formation and follow either a Rayleigh or a batch equilibrium fractionation model. Our results also suggest that the formation of 2:1 clays induces a fractionation factor similar to that of kaolinite formation.

Hughes, H. J.; Sondag, F.; Santos, R. V.; André, L.; Cardinal, D.

2013-11-01

284

Spatial and temporal distribution in density and biomass of two Pseudodiaptomus species (Copepoda: Calanoida) in the Caeté river estuary (Amazon region--North of Brazil).  

PubMed

Spatial and temporal density and biomass distribution of the planktonic copepods Pseudodiaptomus richardi and P. acutus along a salinity gradient were investigated in the Caeté River Estuary (North-Brazil) in June and December, 1998 (dry season) and in February and May, 1999 (rainy season). Copepod biomass was estimated using regression parameters based on the relation of dry weight and body length (prosome) of adult organisms. The Caeté River Estuary was characterized by high spatial and temporal variations in salinity (0.8-37.2). Exponential length-weight relationships were observed for both Pseudodiaptomus species. Density and biomass values oscillated between 0.28-46.18 ind. m-3 and 0.0022-0.3507 mg DW. m-3 for P. richardi; and between 0.01-17.02 ind. m-3 and 0.0005-0.7181 mg DW. m-3 for P. acutus. The results showed that the contribution of P. richardi for the secondary production in the Caeté River Estuary is more important in the limnetic zone than in other zones where euhaline-polyhaline regimes were predominant. However, it was not possible to observe a clear pattern of spatial and temporal distribution for P. acutus. PMID:16862295

Magalhães, A; Costa, R M; Liang, T H; Pereira, L C C; Ribeiro, M J S

2006-05-01

285

Methylmercury in hair samples from different riverine groups, Amazon, Brazil  

Microsoft Academic Search

The present study was aimed to evaluate comparatively the levels of methylmercury (MeHg) in human hair, collected from different\\u000a groups of Amazonian populations exposed to contamined fish. The study was undertaken in fishing villages and gold mining areas,\\u000a mainly in the Tapajs and Madeira river basins, two of the main tributaries of Amazon river. The study population included\\u000a 125 hair

H. A. Kehrig; O. Malm; H. Akagi

1997-01-01

286

Lost in the Amazon  

NSDL National Science Digital Library

The Lost in the Amazon curricular unit is a series of minds-on and hands-on engineering activities based on an adventure scenario set in the Amazon rainforest in Brazil. Students imagine themselves to be a team of EnviroTech engineers returning to the U.S. from a conference in Brasilia, Brazil. When their plane crashes deep in the Amazon forest, they work in groups to overcome various obstacles in their quest to survive and reach the nearest city as quickly and safely as possible. Motivated by this adventurous theme, students discover, learn and apply the following: 1) classification of plants and insects; 2) general categorizing skills; 3) process skills: problem solving and critical thinking; 4) scientific testing and experimentation; 5) materials properties.

Adventure Engineering

287

Kinetic analysis of gill (Na?,K?)-ATPase activity in selected ontogenetic stages of the Amazon River shrimp, Macrobrachium amazonicum (Decapoda, Palaemonidae): interactions at ATP- and cation-binding sites.  

PubMed

We investigated modulation by ATP, Mg²?, Na?, K? and NH?? and inhibition by ouabain of (Na?,K?)-ATPase activity in microsomal homogenates of whole zoeae I and decapodid III (formerly zoea IX) and whole-body and gill homogenates of juvenile and adult Amazon River shrimps, Macrobrachium amazonicum. (Na?,K?)-ATPase-specific activity was increased twofold in decapodid III compared to zoea I, juveniles and adults, suggesting an important role in this ontogenetic stage. The apparent affinity for ATP (K(M) = 0.09 ± 0.01 mmol L?¹) of the decapodid III (Na?,K?)-ATPase, about twofold greater than the other stages, further highlights this relevance. Modulation of (Na?,K?-ATPase activity by K? also revealed a threefold greater affinity for K? (K?.? = 0.91 ± 0.04 mmol L?¹) in decapodid III than in other stages; NH?? had no modulatory effect. The affinity for Na? (K?.? = 13.2 ± 0.6 mmol L?¹) of zoea I (Na?,K?)-ATPase was fourfold less than other stages. Modulation by Na?, Mg²? and NH?? obeyed cooperative kinetics, while K? modulation exhibited Michaelis-Menten behavior. Rates of maximal Mg²? stimulation of ouabain-insensitive ATPase activity differed in each ontogenetic stage, suggesting that Mg²?-stimulated ATPases other than (Na?,K?)-ATPase are present. Ouabain inhibition suggests that, among the various ATPase activities present in the different stages, Na?-ATPase may be involved in the ontogeny of osmoregulation in larval M. amazonicum. The NH??-stimulated, ouabain-insensitive ATPase activity seen in zoea I and decapodid III may reflect a stage-specific means of ammonia excretion since functional gills are absent in the early larval stages. PMID:22544049

Leone, Francisco Assis; Masui, Douglas Chodi; de Souza Bezerra, Thais Milena; Garçon, Daniela Pereira; Valenti, Wagner Cotroni; Augusto, Alessandra Silva; McNamara, John Campbell

2012-04-01

288

Enhancing phagocytic activity of hemocytes and disease resistance in the prawn Penaeus merguiensis by feeding Spirulina platensis  

Microsoft Academic Search

Exposing the prawn Penaeus merguiensis to the bacteria Vibrio harveyi and Escherichia coli for an hour or feeding the prawns with Spirulina (Arthrospira) platensis (0.3% w\\/w feed) enhanced the phagocytic activity of their hemocytes. Improvement of the phagocytic activity was primarily through the activation of the hemocytes. The activated phagocytic hemocytes had a higher capacity to engulf foreign agents, such

Yuan-Kun Lee; Pei-Fern Chew; Boon-Seng Soh; Lai Yee Tham

2003-01-01

289

Challenges and Opportunities for Co-Management of a Migratory Fish (Prochilodus nigricans) in the Peruvian Amazon  

Microsoft Academic Search

Fisheries co-management lies at the center of environmental, social, and economic issues in the lower Pastaza River basin in the Peruvian Amazon. In this remote region, the intermingling of black and white water systems creates unique aquatic habi- tats that harbor diverse assemblages of fishes, including Prochilodus nigricans, a migratory species of high ecological and socioeconomic importance throughout the Amazon.

Mariana Montoya

290

Oxidation and Reduction Rates for Organic Carbon in the Amazon Mainstream Tributary and Floodplain, Inferred from Distributions of Dissolved Gases.  

National Technical Information Service (NTIS)

Concentrations of CO2, O2, CH4, and N2O in the Amazon River system reflect an oxidation-reduction sequence in combination with physical mixing between the floodplain and the mainstem. Concentrations of CO2 ranged from 150 microM in the Amazon mainstem to ...

J. E. Richey A. H. Devol S. C. Wofsy R. Victoria M. N. G. Riberio

1986-01-01

291

CTD Observations on the North Brazil Shelf during a Multidisciplinary Amazon Shelf SEDiment Study, AMASSEDS, August 1989.  

National Technical Information Service (NTIS)

CTD and acoustic Doppler current profiler (ADCP) observations were made on the North Brazil shelf adjacent to the mouth of the Amazon River during R/V Iselin cruise I8909 August 3-14, 1989 as part of A Multidisciplinary Amazon Shelf SEDiment Study (AMASSE...

R. Limeburner R. C. Beardsley

1989-01-01

292

CTD Observations on the North Brazil Shelf during a Multidisciplinary Amazon Shelf SEDiment Study (AMASSEDS), May-June 1990.  

National Technical Information Service (NTIS)

Hydrographic (CTD) and acoustic Doppler current profiler (ADCP) observations were made on the North Brazil shelf adjacent to the mouth of the Amazon River during R/V Iselin cruise I9004 May 23-June 13, 1990 as part of A Multidisciplinary Amazon Shelf SEDi...

R. Limeburner R. C. Beardsley

1991-01-01

293

CTD Observations on the North Brazil Shelf during a Multidisciplinary Amazon Shelf SEDiment Study (AMASSEDS), February-March 1990.  

National Technical Information Service (NTIS)

Hydrographic (CTD) and acoustic Doppler current profiler (ADCP) observations were made on the North Brazil shelf adjacent to the mouth of the Amazon River during R/V Iselin cruise I9002 February 10-March 29, 1990 as part of A Multidisciplinary Amazon Shel...

R. Limeburner R. C. Beardsley

1991-01-01

294

The Amazon and climate  

NASA Technical Reports Server (NTRS)

The climatologies of cloudiness and precipitation for the Amazon, are reviewed and the physical causes of some of the observed features and those which are not well known are explained. The atmospheric circulation over the Amazon is discussed on the large scale tropical circulations forced by deep diabatic heating sources. Weather deforestation which leads to a reduction in evapotranspiration into the atmosphere, and a reduction in precipitation and its implicated for the gobal climate is discussed. It is indicated that a large scale clearing of tropical rainforests there would be a reduction in rainfall which would have global effects on climate and weather both in the tropical and extratropical regions.

Nobre, C. A.

1984-01-01

295

Fishing for prawn larvae in Bangladesh: an important coastal livelihood causing negative effects on the environment.  

PubMed

Freshwater prawn (Macrobrachium rosenbergii) farming in Bangladesh has, to a large extent, been dependent on the supply of wild larvae. Although there are 81 freshwater prawn hatcheries in the country, a lack of technical knowledge, inadequate skilled manpower, and an insufficient supply of wild broods have limited hatchery production. Many thousands of coastal poor people, including women, are engaged in fishing for wild prawn larvae along the coastline during a few months each year. On average, 40% of the total yearly income for these people comes from prawn larvae fishing activity. However, indiscriminate fishing of wild larvae, with high levels of bycatch of juvenile fish and crustaceans, may impact negatively on production and biodiversity in coastal ecosystems. This concern has provoked the imposition of restrictions on larvae collection. The ban has, however, not been firmly enforced because of the limited availability of hatchery-raised larvae, the lack of an alternative livelihood for people involved in larvae fishing, and weak enforcement power. This article discusses the environmental and social consequences of prawn larvae fishing and concludes that, by increasing awareness among fry fishers, improving fishing techniques (reducing bycatch mortality), and improving the survival of fry in the market chain, a temporal ban may be a prudent measure when considering the potential negative impacts of bycatch. However, it also suggests that more research is needed to find out about the impact of larvae fishing on nontarget organisms and on the populations of targeted species. PMID:20496649

Ahmed, Nesar; Troell, Max

2010-02-01

296

Regulation of essential heavy metals (Cu, Cr, and Zn) by the freshwater prawn macrobrachium malcolmsonii (Milne Edwards)  

SciTech Connect

Despite the low concentrations of heavy metals in the surrounding medium, aquatic organisms take them up and accumulate them in their soft tissues to concentrations several fold higher than those of ambient levels. Knowledge of accumulation patterns of a particular trace metal is a prerequisite for understanding the significance of an observed metal concentration in a particular animal, especially from the aspect of biomonitoring. Many marine invertebrates accumulate heavy metals without any regulation and the accumulation necessarily being associated with mechanisms to store the metals in a detoxified form. Two detoxification mechanisms have been described, both of which may occur in one specimen. Heavy metals can either be bound up in insoluble metalliferous {open_quote}granules{close_quote}, or are bound to soluble metal-binding ligands, such as metallothioneins. Some marine decapod crustaceans have an innate ability to regulate the internal concentrations of essential but potentially toxic metals within a constant level, presumably to meet their metabolic demands. However, at present, there is no such information relating to freshwater decapod crustaceans, especially shrimps which occupy a totally different environment. Macrobrachium malcolmsonii, a potential aquaculture species for freshwater is found in abundance in one of the major Indian rivers, the Cauvery. In the present study, an attempt was made to determine whether the freshwater prawn, M. malcolmsonlii, is able to regulate the three essential elements, copper, chromium and zinc, over a wide range of dissolved concentrations. These three metals were chosen because the Cauvery River receives pollutants containing these metals.

Vijayram, K. [Periyar E.V.R. College, Tiruchirappalli (India)] [Periyar E.V.R. College, Tiruchirappalli (India); Geraldine, P. [Bharathidasan Univ., Tiruchirappalli (India)] [Bharathidasan Univ., Tiruchirappalli (India)

1996-02-01

297

Simulation of SWOT measurements over the Amazon delta  

NASA Astrophysics Data System (ADS)

The purpose of our study is to evaluate SWOT’s skills with the high mode of resolution (pixel: 4m x 10 to 70m) to highlight estuaries dynamic or to complete a lack of in situ data used by the hydrodynamic models . To reach this goal we have two simulators: one end-to-end developed by S. Biancamaria at Legos and another one developed by the help of industrials Altamira Information and Cap Gemini which describes the physic phenomenon. Both of them need a full description of the instantaneous water states described by a DEM and model’s output. We present first results on the Amazon’s delta due to his peculiar tided-sensitivity. To perform our simulation we have used the hydrodynamic finite element model T-UGOm, the Ore-Hybam data base and data collected during a campaign realised in 2010 over the Amazon river.

Lion, C.; Lyard, F.; Calmant, S.; Crétaux, J.; Le Bars, Y.; Fjortoft, R.

2010-12-01

298

Ontogenic study of isozymes in giant tiger prawn, Penaeus monodon (Crustacea: Decapoda)  

NASA Astrophysics Data System (ADS)

The patterns of isozyme variation throughout the life cycle of the giant tiger prawn, Penaeus monodon were described for ten enzyme systems (G3PD, MDH, LGG, GPI, MPI, FBP, PGM, LDH, PGD, and PROT). The zymograms showed little variation in the number of isozymic loci expressed during larval development compared with results reported for other penaeid prawns. There were specific ontogenic patterns at some loci. As larvae developed beyond the embryonic stage, there was a tendency for intensity of staining and complexity of banding patterns to increase.

Tong, Jin-Gou; Ballment, E.; Benzie, J. A. H.

1996-12-01

299

Modern sedimentation in the Lower Negro River, Amazonas State, Brazil  

Microsoft Academic Search

The Negro River, which flows through the north central Amazon Basin, is one of the largest tributaries of the Amazon. The name “Negro” comes from the colour of its water, which reflects the large quantity of dissolved humic acids and iron oxides that also gives the water its characteristic acid pH. The river is estimated to have the fifth largest

Elena Franzinelli; Hailton Igreja

2002-01-01

300

Was the 2009 flood the most hazardous or the largest ever recorded in the Amazon?  

NASA Astrophysics Data System (ADS)

Floods are fundamental components of Amazon nature and culture. The large flood of 2009, however, opened a new perspective on hazards and disasters in the Amazon basin. More than 238,000 residents from 38 municipalities were affected by floods along the Amazon River and lower reaches of its tributaries. Never before has a flood in the Amazon produced such a dramatic effect on the local population. The magnitude of the disaster suggested it was the largest recorded Amazon flood since the beginning of measurements in 1928 at Óbidos and that it could represent the largest recorded flood on Earth. A complex combination of atmospheric and hydrologic factors made the 2009 Amazon flood the most hazardous. It was the result of large scale and regional climatic events, non-typical mechanisms of flood transmission generating complex inter-relations in time and space between the main system and the tributaries, and recent urban growth of riverine cities without adequate planning. Our measurements at Óbidos, however, indicate that the 2009 flood was the highest recorded Amazon stage, but most likely not the largest water discharge. We propose as well that the magnitude of the Amazon floods at Óbidos has been overestimated for decades and that the available values of flood discharge have been a source of error for a multidisciplinary set of scientists developing climate and environmental modeling.

Filizola, Naziano; Latrubesse, Edgardo M.; Fraizy, P.; Souza, R.; Guimarães, V.; Guyot, J.-L.

2014-06-01

301

Impact of cyclones and aquatic macrophytes on recruitment and landings of tiger prawns Penaeus esculentus in Exmouth Gulf, Western Australia  

NASA Astrophysics Data System (ADS)

The cover of seagrasses and macroalgae, landings and fishery-independent measures of spawning stock and recruitment for brown tiger prawns, were monitored immediately following a major cyclone in Exmouth Gulf, Western Australia in March 1999. Anecdotal evidence on the extent of seagrass from 1990 to 1998 suggests that the cyclone caused a major, immediate disruption and loss of the seagrass/macroalgal beds (to ?2% cover), the critical prawn nursery habitat, and mangroves in the shallow inshore waters of the system. Prawn landings and recruitment to the fishery were not affected in the year of the cyclone, but were markedly lower in the two years immediately afterwards and then increased as the cover of macrophytes increased to over 40% in 2003. Tiger prawn landings and catch rates were not affected in Shark Bay, a system 500 km south of Exmouth Gulf that did not experience cyclonic disturbance. Seagrasses in Exmouth Gulf showed a succession of species from small colonising species (Halophila ovalis and Halodule uninervis) to larger, broad-leaved species (Cymodocea serrulata, Syringodium isoetifolium) only two years after the cyclone. The recruitment and landings of tiger prawns were correlated significantly with the total cover of macroalgae and seagrass. The large loss of seagrass and macroalgae reduced the settling habitat for postlarvae and the nursery habitat for juvenile tiger prawns, probably leading to the lower recruitment to the fishery. These findings suggest that the extent of seagrass and macroalgae are some of the factors defining the productivity of the tiger prawn fishery in Exmouth Gulf.

Loneragan, N. R.; Kangas, M.; Haywood, M. D. E.; Kenyon, R. A.; Caputi, N.; Sporer, E.

2013-07-01

302

Comparison of Late Quaternary Climate Development Between the Niger Catchment Area and the Amazon Basin  

Microsoft Academic Search

The inorganic terrigenous fraction of marine sediments offers a great number of different and well established proxy parameters to investigate the development of continental climate. In this study we present high resolution records of terrigenous source elements from the Niger River and the Amazon River fans. Sediment cores are well dated by radiocarbon measurements. Elemental records from both regions reveal

M. Zabel; V. Ettwein; M. Maslin; R. R. Schneider

2003-01-01

303

Fishing Effort and Catch Composition of Urban Market and Rural Villages in Brazilian Amazon  

Microsoft Academic Search

The management of small-scale freshwater fisheries in Amazon has been based usually on surveys of urban markets, while fisheries\\u000a of rural villages have gone unnoticed. We compared the fishing characteristics (catch, effort and selectivity) between an\\u000a urban market and five small villages in the Lower Tocantins River (Brazilian Amazon), downstream from a large reservoir. We\\u000a recorded 86 and 601 fish

Gustavo Hallwass; Priscila Fabiana Lopes; Anastacio Afonso Juras; Renato Azevedo Matias Silvano

2011-01-01

304

Mapping the Amazon: The Mouth of the Amazon  

NSDL National Science Digital Library

The Amazon rain forest is the largest tropical forest in the world. It stretches across South America from nearly ocean to ocean. No seasonal view of this territory existed until a NASA-university collaboration began mapping the Amazon - from space. Scientists listed worked as a team on Mosaicking Software and Mosaic Production.

Snodgrass, Stuart; Chapman, Bruce; Curkendall, David; Freeman, Tony; Miller, Craig; Siegel, Herb

2002-03-14

305

Uranium geochemistry on the Amazon shelf: Evidence for uranium release from bottom sediments  

SciTech Connect

In Amazon-shelf waters, as salinity increases to 36.5 x 10{sup {minus}3}, dissolved uranium activities increase to a maximum of 4.60 dpm 1{sup {minus}1}. This value is much higher than the open-ocean value (2.50 dpm 1{sup {minus}1}), indicating a source of dissolved uranium to shelf waters in addition to that supplied from open-ocean and riverine waters. Uranium activities are much lower for surface sediments in the Amazon-shelf sea bed (mean: 0.69 {plus minus} .09 dpm g{sup {minus}1}) than for suspended sediments in the Amazon river (1.82 dpm g{sup {minus}1}). Data suggest that the loss of particulate uranium from riverine sediments is probably the result of uranium desorption from the ferric-oxyhydroxide coatings on sediment particles, and/or uranium release by mobilization of the ferric oxyhydroxides. The total flux of dissolved {sup 238}U from the Amazon shelf (about 1.2 x 10{sup 15} dpm yr{sup {minus}1}) constitutes about 15% of uranium input to the world ocean, commensurate to the Amazon River's contribution to world river-water discharge. Measurement of only the riverine flux of dissolved {sup 238}U underestimates, by a factor of about 5, the flux of dissolved {sup 238}U from the Amazon shelf to the open ocean.

McKee, B.A.; DeMaster, D.J.; Nittrouer, C.A. (North Carolina State Univ., Raleigh (USA))

1987-10-01

306

The hearing abilities of the prawn Palaemon serratus.  

PubMed

The mechanism of sound reception and the hearing abilities of the prawn (Palaemon serratus) have been studied using a combination of anatomical, electron microscopic and electrophysiological approaches, revealing that P. serratus is responsive to sounds ranging in frequency from 100 to 3000 Hz. It is the first time that the Auditory Brainstem Response (ABR) recording technique has been used on invertebrates, and the acquisition of hearing ability data from the present study adds valuable information to the inclusion of an entire sub-phylum of animals when assessing the potential impact of anthropogenic underwater sounds on marine organisms. Auditory evoked potentials were acquired from P. serratus, using two subcutaneous electrodes positioned in the carapace close to the supraesophageal ganglion and the statocyst (a small gravistatic organ located below the eyestalk on the peduncle of the bilateral antennules). The morphology of the statocyst receptors and the otic nerve pathways to the brain have also been studied, and reveal that P. serratus possesses an array of sensory hairs projecting from the floor of the statocyst into a mass of sand granules embedded in a gelatinous substance. It is the purpose of this work to show that the statocyst is responsive to sounds propagated through water from an air mounted transducer. The fundamental measure of the hearing ability of any organism possessing the appropriate receptor mechanism is its audiogram, which presents the lowest level of sound that the species can hear as a function of frequency. The statocyst of P. serratus is shown here to be sensitive to the motion of water particles displaced by low-frequency sounds ranging from 100 Hz up to 3000 Hz, with a hearing acuity similar to that of a generalist fish. Also, recorded neural waveforms were found to be similar in both amplitude and shape to those acquired from fish and higher vertebrates, when stimulated with low-frequency sound, and complete ablation of the electrophysiological response was achieved by removal of the statocyst. PMID:15664317

Lovell, J M; Findlay, M M; Moate, R M; Yan, H Y

2005-01-01

307

Impact of Cattle Shed Effluent on Certain Biochemical Parameters of the Freshwater Prawn Caridina weberi  

Microsoft Academic Search

2 Abstract: Domestic sewage consists of discharges of dirty water from cattle shed, bathrooms, lavatories and kitchens. It is a complex mixture of mineral and organic matters in many forms, including large and small particles of solid matter, substances in solution, in suspensions and in colloidal and pseudocolloidal dispersion. The freshwater prawn, Caridina weberi was exposed to various concentrations of

P. Thenmozhi; P. Ronald Ross; K. Balakrishnan

308

An assessment of Bycatch Reduction Devices in a tropical Australian prawn trawl fishery  

Microsoft Academic Search

Our study assessed 16 different Bycatch Reduction Devices (BRDs) for use in Australia's Northern Prawn Fishery (NPF), during three cruises in the Gulf of Carpentaria. The study was a response to pressure from conservation and community groups to make harvesting of the sea more selective and less damaging to the non-target communities. The approach was to incrementally improve the performance

David Brewer; Nicholas Rawlinson; Steve Eayrs; Charis Burridge

1998-01-01

309

Incidental capture, direct mortality and delayed mortality of sea turtles in Australia's Northern Prawn Fishery  

Microsoft Academic Search

The species composition, catch and mortality rates of sea turtles captured incidentally by the tiger prawn fishery on Australia's northern coast in 1989 and 1990 were estimated by monitoring the fishery's catch. In 1990, the delayed rate of mortality from damage was estimated and the size composition was measured. Five species of turtles were captured: the flatback (Natator depressa, 59%

I. R. Poiner; A. N. M. Harris

1996-01-01

310

Modifications to reduce bycatch in prawn trawls: A review and framework for development  

Microsoft Academic Search

The incidental capture of non-target species fromprawn trawling has recently attracted worldwide attention. Primarily, concerns arisefrom the perception that prawn trawls catch anddiscard large numbers of juveniles of species that,when larger, are targeted in other commercial andrecreational fisheries. While several managementoptions are available, the majority of fisheries inthe world have attempted to address this issue throughphysical modifications to trawls, designed

Matt K. Broadhurst

2000-01-01

311

Cypermethrin toxicity to aquatic life: bioassays for the freshwater prawn Palaemonetes argentinus.  

PubMed

Cypermethrin (CY) effects were evaluated in freshwater prawn Palaemonetes argentinus, a common member of the aquatic fauna in the vegetated littoral of lotic and lentic environment of La Plata basin. LC50 was calculated, and oxygen uptakes together with ammonia-N excretion were related to biocide concentrations. Behavioral and growth changes were analyzed, and a unique application of CY was evaluated in P. argentinus micropopulations. LC50 and their 95% confidence limit were 0.0031 microg CY L(-1) (0.0023-0.0039) for 24 h and 0.0020 microg CY L(-1) (0.0014-0.0027) for 96 h. Oxygen uptake and ammonia-N excretion increased in the prawns kept in CY solutions. The behavioral effect was hyperactivity. Although prawns in biocide groups have null or negative growth, the intermolt period was 246% larger than in the control group. Moreover, the mortality in the second cycle was 100%. A unique application of pyrethoid provoked high mortality after 50 days. The low concentrations of this biocide affected the survival and altered the prawn metabolic activity, behavioral and ecdysis cycle. These results suggest that juveniles of P. argentinus are much more sensitive to CY pollution than other crustaceans, fish, and tadpoles. PMID:16418889

Collins, P; Cappello, S

2006-07-01

312

A Simple "in Vitro" Culture of Freshwater Prawn Embryos for Laboratory Investigations  

ERIC Educational Resources Information Center

Giant freshwater prawn ("Macrobrachium rosenbergii" De Man) embryos can be cultured "in vitro" to hatching in 15% (v/v) artificial seawater (ASW). This technique can be applied as a bioassay for testing toxicity or for the effects of various substances on embryo development and can be used as a simple and low-cost model for studying embryo…

Porntrai, Supaporn; Damrongphol, Praneet

2008-01-01

313

Effects and toxicity of phthalate esters to hemocytes of giant freshwater prawn, Macrobrachium rosenbergii  

Microsoft Academic Search

Phthalate esters (PAEs) have been considered as environmental pollutants and have been subject to control in the United States of America and Japan. The aim of this study was to investigate the effects and toxicity of eight PAEs to hemocytes and the defense functions of giant freshwater prawn (Macrobrachium rosenbergii), including hemocytic adhesion, pseudopodia formation, phenoloxidase (PO) activity, and superoxide

Hung-Hung Sung; Wei-Yi Kao; Yi-Jen Su

2003-01-01

314

The value of patches of intertidal seagrass to prawns depends on their proximity to mangroves  

Microsoft Academic Search

Penaeid prawns were sampled with a small seine net to test whether catches of postlarvae and juveniles in seagrass were affected by the distance of the seagrass (mainly Zostera capricorni) from mangroves and the density of the seagrass in a subtropical marine embayment. Sampling was replicated on the western and eastern sides of Moreton Bay, Queensland, Australia. Information on catches

Greg A. Skilleter; Andrew Olds; Neil R. Loneragan; Yuri Zharikov

2005-01-01

315

Molecular and immunological responses of the giant freshwater prawn, Macrobrachium rosenbergii, to the organophosphorus insecticide, trichlorfon.  

PubMed

Trichlorfon is an organophosphorus (OP) insecticide that is used as an agriculture pesticide to destroy insects, a human medicine to combat internal parasites, and an ectoparasiticide in the livestock and aquaculture industries, but which has caused aquatic toxicity in the prawn industry. The aim of this study was to investigate the effects of trichlorfon on molecular and enzymatic processes of the immunological response of the giant freshwater prawn, Macrobrachium rosenbergii, at 0, 0.2, and 0.4mgL(-1) with 0, 3, 6, 12, and 24h of exposure. The total hemocyte count (THC), respiratory bursts (RBs), phenoloxidase (PO) activity, and superoxide dismutase (SOD) activity were examined to evaluate immunological responses and oxidative stress. Results showed that THCs of the prawn exposed to trichlorfon at both concentrations (0.2 and 0.4mgL(-1)) had increased after 12 and 24h; SOD and PO activities had significantly increased at 3h, whereas production of RBs had dramatically increased as oxidative stress at each sampling time after exposure to trichlorfon compared to the control. A potential biomarker of OPs, acetylcholinesterase (AChE) revealed a significant decrease after exposure for 6h, and showed a time-dependent tendency. Immune gene expressions, including prophenoloxidase (proPO), the lipopolysaccharide- and ?-1,3-glucan-binding protein (LGBP), peroxinectin (PE), ?2-macroglubulin (?2M), transglutaminase (TG), and copper, zinc (Cu,Zn)-SOD, of prawns exposed to trichlorfon at 0, 0.2, and 0.4mgL(-1) for 0, 6, and 24h were further evaluated. Expressions of all of the immune genes significantly decreased when prawns were exposed to 0.4mgL(-1) trichlorfon for 24h, and among them, an increase in SOD expression was seen after exposure to 0.4mgL(-1) for 6h. Prawns exposed to trichlorfon within 24h exhibited the decrease of circulating hemocytes, and also the induction of oxidative stress, which caused subsequent damage to DNA formation of immune genes. From these results, we concluded that immunological responses and immune gene expressions of prawn exposed to trichlorfon at 0.4mgL(-1) for 24h were perturbed, thus causing a deficiency in immunity and subsequent increased susceptibility to pathogen infections. PMID:23340335

Chang, Chin-Chyuan; Rahmawaty, Atiek; Chang, Zhong-Wen

2013-04-15

316

Flooding dynamics on the lower Amazon floodplain: 2. Seasonal and interannual hydrological variability  

NASA Astrophysics Data System (ADS)

We analyzed seasonal and interannual variability in hydrological fluxes and inundation dynamics of a large floodplain unit (2440 km2) along the lower Amazon River over a period of 15 years (1995-2010). Floodplain inundation was simulated using LISFLOOD-FP, which combines one-dimensional river routing with two-dimensional overland flow, and a local hydrological model. Dominant sources of inflow varied seasonally among direct rain and local runoff (November), Amazon River (December to August) and seepage (September and October). Shifts in timing of dominance among the water balance components occurred conform variations in annual peak stage. The period of dominance of river inflow over total floodplain influxes began about 1 month earlier and ended 1 month later in the 2009 high flood year compared to the 1998 low flood year. On average, river to floodplain discharge represented 0.75% of the Amazon River discharge at Óbidos and 82% of the annual hydrological influxes to the floodplain. We observed an up to ninefold variation in river-floodplain annual discharge. Relatively small increments in main stem peak discharge cause disproportionately large changes in the flow routed through the floodplain. Despite the higher frequency of years with lower minimum stages, the intensification of the hydrological cycle of the Amazon Basin is causing substantially greater amounts of riverine water to flow across floodplain environments.

Rudorff, Conrado M.; Melack, John M.; Bates, Paul D.

2014-01-01

317

Methane emissions to the troposphere from the Amazon floodplain  

NASA Technical Reports Server (NTRS)

The magnitudes of CH4 emissions to the troposphere from the Amazon River floodplain and the mechanism of these emissions were investigated using the data of 94 individual flux measurements made along a 1700-km stretch of the river during July/August 1985. The overall average rate of CH4 emission from wetlands was found to be 390 mg CH4/sq m per day, with the highest emissions (590 mg CH4/sq m per day) attributed to the water surfaces covered by aquatic macrophytes. Ebullition was the dominant mechanism of emission, accounting for 85 percent of the total. Surface-water CH4 concentrations were highly supersaturated, averaging 6.4 micromolar. The annual emission of CH4 from the Amazon Basin to the troposphere, estimated from the area and the known emission rate, is about 10 CH4 Tg/yr, indicating the importance of the area in the global atmospheric CH4 cycle.

Devol, Allen H.; Richey, Jeffrey E.; Clark, Wayne A.; King, Stagg L.; Martinelli, Luiz A.

1988-01-01

318

Methane Evasion and Carbon Dynamics on the Amazon Floodplain  

NASA Astrophysics Data System (ADS)

The fringing floodplain along the 2600 km reach of the Amazon River in Brazil inundates up to about 80,000 km squared of flooded forests, open water and floating macrophytes. These habitats outgas significant amount of carbon dioxide and methane as a result of autochthonous and allochthonous fixation and exchanges of carbon on the floodplain and with the neighboring uplands. Based on our measurements and those of others, we have assembled sufficient data to characterize the following fluxes and transformations in a representative central Amazon floodplain lake: inputs of litterfall, dissolved organic carbon (DOC) in rainfall, DOC and particulate organic carbon (POC) in streams, DOC in groundwater seepage; exchanges of DOC and POC with the mainstem river; net primary productivity of floating macrophyes, periphyton and phytoplankton; sedimentation; carbon dioxide and methane evasion. These data are the basis for models of carbon processing and methane evasion.

Melack, J. M.

2007-12-01

319

The toxic effect of phthalate esters on immune responses of giant freshwater prawn ( Macrobrachium rosenbergii) via oral treatment  

Microsoft Academic Search

A previous in vitro study has indicated that four phthalate esters (PAEs) could damage hemocytes and decreases the cellular immunity of prawns [Sung, H.H., Kao, W.Y., Su, Y.J., 2003. Effects and toxicity of phthalate esters to hemocytes of giant freshwater prawn, Macrobranchium rosenbergii. Aquat. Toxicol. 64, 25–37]. The aim of this study was to investigate the in vivo effect of

Wen-Liang Chen; Hung-Hung Sung

2005-01-01

320

Isolation and characterization of a female-specific DNA marker in the giant freshwater prawn Macrobrachium rosenbergii  

PubMed Central

In this study, a female-specific DNA marker in the freshwater prawn Macrobrachium rosenbergii was identified through amplified fragment length polymorphism (AFLP). The AFLP-derived sequence-characterized amplified region (SCAR) marker was tested in over 200 individuals, giving reproducible sex identification. Further molecular characterization of the sex-marker's genomic region (?3?kb long) revealed the presence of tandem and inverted repeats. The ?3-kb sequence was identified both in male and female prawns, but with subtle differences: a deletion of 3?bp (present in female prawn but absent in male prawn) identified upstream of the SCAR marker sequence and two female-specific single-nucleotide polymorphisms, both indicating that male prawns are homozygous, whereas female prawns are heterozygous in this locus. Fluorescent in situ hybridization showed the ?3-kb sequence to be unique: to the best of our knowledge, this is the first report of a unique sex-specific sequence observed in situ in crustaceans. The sex-specific marker identified in M. rosenbergii may have considerable applied merit for crustacean culture in that it will enable the determination of genetic sex at early developmental stages when phenotypic differences are not identifiable.

Ventura, T; Aflalo, E D; Weil, S; Kashkush, K; Sagi, A

2011-01-01

321

ENVISAT altimetry over narrow reaches of the Amazon basin contributors  

NASA Astrophysics Data System (ADS)

The lower limit in river width of the capability of radar altimetry to retrieve river stages is still a matter of debate. The Amazon basin includes rivers of all size, from as wide as several kilometers to as narrow as a few tens of meters. We have derived ~500 series in this basin over the entire range of reach widths. In the present study, we analyze the quality of these series with respect to the reach width criterion. We show that high quality series (rms error around 20 cm) can be retrieved even for reaches as narrow as 100m, as well as for km wide reaches. Such a result suggests that in a basin such as the Amazon basin, even more valuable series could be derived, probably more than a thousand. Such a dataset of water stages densely distributed throughout the basin is clearly a major dataset for any kind of study dealing with the hydrology of the Amazon basin. A preliminary test with a few series derived in the Congo basin suggests that similar results can be expected for this basin, too.

Silva, J. S.; Calmant, S.; Seyler, F.; Research Team Of Rhasa

2013-05-01

322

How Pecten Brazil drilled the Amazon basin  

SciTech Connect

Pecten Brazil overcame numerous obstacles to drill two exploratory wells in the Amazon Basin last year. These included: The threat of low water in normally navigable rivers. Dense jungle growth at both locations. Lack of suitable roads for heavy hauling. Inconvenient distances from supply points. An unusual basalt formation responsible for unique drilling problems. Hundreds of helicopter lifts to move drilling rigs, supplies, and personnel. Pecten contracted with Petrobras, the Brazilian national oil company, to evaluate three blocks in the Amazon jungle, each about 68 miles (110 km) on a side, through seismic study and ultimate drilling. Planning for the drilling phase got started on March 17, 1981 with December 1 targeted as spud date for the first well. Actual spud date was November 25, 5 days ahead of schedule, in spite of all obstacles. Pecten has a mid-Amazonas block now under seismic investigation for possible exploratory drilling. Logistics problems in this one provide new difficulties, as the area is extremely wet. Most work is carried on by boat. The company is also looking offshore Bahia, testing the possible extension of the Renconcavo basin. Two wells have already provided good shows of a high pour point oil, with flow rates from 400 to 1,000 b/d. Another area of interest to Pecten is offshore Rio Grande do Norte.

Bleakley, W.B.

1983-09-01

323

Reexamining the late Cenozoic geologic evolution of the Amazon basin  

NASA Astrophysics Data System (ADS)

The recent geologic evolution of the Amazon basin has been the focus of many recent studies. Our own research and our review of the literature suggest a need for reevaluation of many aspects of this history including several key questions: What was the timing of Andean uplift (especially, the Western Cordillera)? What is the relationship between the northernmost Solimões Formation and northern Andean tectonic activity? What is the precise age of the lowermost levels of the Solimões Formation? Were there marine incursions? Are tidal deposits recorded in Amazonia? Was there a very large, long-lived, Miocene "Pebas" megalake in the western Amazon? When did the trans-continental, eastern outlet, Amazon drainage become established? What is the antiquity of the Amazon fan? Correct answers to these questions are essential in order to gain a better understanding of the climatic and biogeographic history of the Amazon basin. Although several authors have suggested the existence of late Miocene tidal sediments deposited during a sea-level high stand and marine transgressions into the Amazon basin from the north (Caribbean Sea) or from the south (Paranáense Sea), both the existence of a late Miocene seaway through western Amazonia and the existence of thousands of square kilometers affected by tides are difficult to support. The faunal composition and pollen content of the upper Miocene Solimões Formation are inconsistent with tidal/marine environments. And, as we have demonstrated, deposits in Peruvian Amazonia that have been attributed to Miocene tidal environments are actually fluvial sediments that have been environmentally and chronologically misinterpreted. Further, the existence of a giant paleolake in western Amazonia during the middle to late Miocene is inconsistent with our paleoenvironmental reconstructions of shifting rivers in aggradational conditions - reconstructions that are consistent with the interpretations of the Solimões Formation in other parts of the basin and with sedimentary architecture at both basin scale and depositional-system scale. We have previously suggested that ca. 5 Ma, during the period when low-angle subduction was fully developed in the Nazca Plate between ~3° and 15°S, reorganization of drainage resulted in the transformation of the southwestern Brazilian Amazon from a basin that trapped sediments to an erosional region that contributed sediments to the Amazon fluvial system. It is likely that at that time the lowland fluvial systems of southwestern Amazonia began to drain to the Atlantic Ocean. A ca. 5 Ma reorganization of the Amazon fluvial system and its connection with the Atlantic Ocean is consistent with the record of terrigenous deposits in the Ceara Rise, close to the Amazon cone. Our analysis of new cores and seismic data from the Amazon fan, as well as a combined morphostratigraphic and biostratigraphic analysis of the western Amazonian lowlands, will provide additional clues to the relationship between tectonics, sea level, and the evolution of the trans-continental Amazon drainage.

Rigsby, C. A.; Latrubesse, E. M.; Baker, P. A.; Silva, C. G.

2010-12-01

324

Rivers  

NSDL National Science Digital Library

This site features pages to more than twenty NASA radar images of the world's major river systems. The image pages contain a brief description of the respective processes and setting, and are available for download. The images were created with the Spaceborne Imaging Radar-C and X-Band Synthetic Aperture Radar (SIR-C/X-SAR) as part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions. The multi-frequency data will be used by the international scientific community to better understand the global environment and how it is changing.

Pavlovsky, Rich

325

Rivers of Destiny  

NSDL National Science Digital Library

These summaries and video excerpts examine the health of four river systems - the Mississippi, the Amazon, the Jordan and the Mekong, and how environmental problems are facing those who depend on them. There is an account of the flooding in Grafton, Illinois in 1993, one of many towns to suffer devastating damage when the upper Mississippi River overflowed its banks. The video excerpts are from the "Journey to Planet Earth" television series; each is approximately three minutes in length.

326

Feasibility of using hydrothermal resources in Malaysian prawn aquaculture. Final report  

SciTech Connect

The potential application of geothermal resources in South Carolina for freshwater prawn aquaculture was examined. In coastal S.C. 23 existing geothermal well sites were identified which encompassed an area which ranged from Georgetown to Beaufort. Depth averaged approx. 615 m while temperature averaged approx. 37/sup 0/C. Artesian flow rates varied from 190 to 2650 1/min. Detailed water quality analyses were conducted at 12 sites. In general, major differences from surface waters were in chlorides, fluorides, dissolved solids, ph, alkalinity, and ammonia levels. A detailed replicated laboratory study was conducted to examine the effect of geothermal water on growth and survival of prawns. After 42 days very poor survival was recorded from the various 100% geothermal water treatments. However, 50:50 mixture of shallow well water and geothermal water resulted in a survival rate of 83%, which was similar to the control treatments. Growth was also similar to that observed among the control animals.

Smith, T.I.J.; Rhodes, R.J.; Wannamaker, A.W.

1982-08-01

327

Total and inorganic arsenic in freshwater fish and prawn in Thailand.  

PubMed

Total and inorganic arsenic levels were determined in 120 samples of eight freshwater animal species collected from five distribution centers in the central region of Thailand between January and March 2011. Eight species with the highest annual catch, consisting of seven fish species and one prawn species, were analyzed. Concentrations of inorganic arsenic (on a wet weight basis) ranged from 0.010 ?g/g in giant prawn (Macrobrachium rosenbergii) to 0.230 ?g/g in striped snakehead (Channa striata). Climbing perch (Anabas testudineus) exhibited the highest mean concentrations of total arsenic (0.459 ± 0.137 ?g/g), inorganic arsenic (0.121 ± 0.044 ?g/g), and percentage of inorganic arsenic (26.2%). Inorganic arsenic levels found in freshwater animals in this study were much lower than the Thai regulatory standard of 2 ?g/g. PMID:23043844

Saipan, Piyawat; Ruangwises, Suthep; Tengjaroenkul, Bundit; Ruangwises, Nongluck

2012-10-01

328

Review of neurobehavioral deficits and river fish consumption from the Tapajós (Brazil) and St. Lawrence (Canada)  

Microsoft Academic Search

Our research group is carrying out studies on neurobehavioral changes associated with eating fish from the Upper St. Lawrence River (Québec, Canada) and the Lower Tapajós River (Brazilian Amazon). Here, these studies are reviewed with respect to exposure, effects and intervention. Although mercury (Hg) levels in piscivorous fish are similar in both regions, in the Amazon, fish constitutes the dietary

Donna Mergler

2002-01-01

329

Mercury and methylmercury in fish and human hair from the Tapajós river basin, Brazil  

Microsoft Academic Search

Mercury is being released in the Amazon in an abusive way due to goldmining activities. The Tapajós river basin was the first to be intensively exploited in the modern Amazon gold rush. Fish and hair samples as the best indicators of human methylmercury contamination were investigated in the main cities and villages along the Tapajós river basin. The upper basin

Olaf Malm; Fernando J. P. Branches; Hirokatsu Akagi; Miriam B. Castro; Wolfgang C. Pfeiffer; Masazumi Harada; Wanderley R. Bastos; Hiroo Kato

1995-01-01

330

Impact of organophosphates on the ovarian changes in freshwater caridean prawn Caridina weberi.  

PubMed

The toxicity of the pesticides (organophosphates) malathion, dimecron and monochrotophos was tested on the freshwater caridean prawn, Caridina weberi. The lethal concentration was determined in experiments carried out up to 96 hrs. The effect of organophosphates on the reproduction was shown by observing the histological changes in the ovary. The tissues were highly damaged, with loss of ooplasmic material, lack of distinct nucleus, nucleolus and chromatin material. PMID:6545997

Nagabhushanam, R; Sarojini, R; Reddy, T S

1984-01-01

331

Tributyltin oxide induced alterations in exuvial weight and calcium content of the prawn, Caridina rajadhari  

Microsoft Academic Search

Moulting is the predominent feature of crustaceans. Cyclic cuticle deposition and resorption of calcium from old cuticle occur\\u000a in relation to the crustacean moult cycle. Prolonged exposure of the prawn,Caridina rajadhari to media containing sublethal doses (0·015, 0·020, 0·025 and 0·040 ppm) of tributyltin oxide led to an apparent increase\\u000a in dry weight of exuvia as well as an increase

R Nagabhushanam; P S Reddy; R Sarojini

1990-01-01

332

Yolk and copper utilisation during embryogenesis of the freshwater prawn Caridina nilotica  

Microsoft Academic Search

Yolk and copper utilisation during embryogenesis of the fresh-water prawnCaridina nilotica var.bengalensis (De Man) have been described. The egg number\\/brood increased with increase in length as well as volume (L\\u000a 8) of the mother animal. The water content increased from 61·3% (I stage) to 76·4% (III stage) as development proceeded. Fat\\u000a appeared to be the major source of energy for

R Ponnuchamy; S Ayyappan; S Ravichandra Reddy; Katre Shakuntala

1979-01-01

333

Characterization of Tri and Tetranucleotide Microsatellites in the Black Tiger Prawn, Penaeus monodon  

Microsoft Academic Search

In order to characterize tri- and tetranucleotide microsatellites in the black tiger prawn, Penaeus monodon, a genomic library of P. monodon was screened with the repeats (GAA)n, (GATA)n, (GGAT)n, (GGAA)n and (CACC)n. In the 79 positive clones isolated, the repeats (GATA)n was found at the highest frequency, followed by the (GAA)n while the other sequence types were rare or not

S Pongsomboon; A Tassanakajon

334

Variation in lipid classes during the molting cycle of the prawn Penaeus japonicus  

Microsoft Academic Search

The variation in the concentration and fatty acid composition of lipid classes during the molting cycle of the prawn Penaeus japonicus was investigated. The lipid concentration of the whole body reached a maximum at mid-premolt (Stage D2) and then decreased to low level at late premolt (Stage D3–4). The accumulation of lipids during the premolt period seemed to be attributable

S. Teshima; A. Kanazawa; H. Okamoto

1977-01-01

335

Involvement of opioid peptides in the regulation of reproduction in the prawn Penaeus indicus  

NASA Astrophysics Data System (ADS)

The possible involvement of an endogenous opioid system in the regulation of ovarian development in the prawn Penaeus indicus was investigated. Injection of leucine-enkephalin significantly increased the ovarian index and oocyte diameter in a dose-dependent manner. In contrast, injection of methionine-enkephalin significantly decreased the ovarian index and oocyte diameters. These results provide evidence to support the hypothesis that an opioid system is involved in the regulation of reproduction in crustaceans.

Sreenivasula Reddy, P.

336

Cypermethrin Toxicity to Aquatic Life: Bioassays for the Freshwater Prawn Palaemonetes argentinus  

Microsoft Academic Search

Cypermethrin (CY) effects were evaluated in freshwater prawn Palaemonetes argentinus, a common member of the aquatic fauna in the vegetated littoral of lotic and lentic environment of La Plata basin. LC50 was\\u000a calculated, and oxygen uptakes together with ammonia-N excretion were related to biocide concentrations. Behavioral and growth\\u000a changes were analyzed, and a unique application of CY was evaluated in

P. Collins; S. Cappello

2006-01-01

337

Selection of marine yeasts for the generation of single cell protein from prawn-shell waste  

Microsoft Academic Search

Marine yeasts (33 strains) were isolated from the coastal and offshore waters off Cochin. The isolates were identified and then characterized for the utilization of starch, gelatin, lipid, cellulose, urea, pectin, lignin, chitin and prawn-shell waste. Most of the isolates were Candida species. Based on the biochemical characterization, four potential strains were selected and their optimum pH and NaCl concentration

R. Rhishipal; Rosamma Philip

1998-01-01

338

Acute toxicity of organochlorine insecticide endosulfan to the giant freshwater prawn Macrobrochium rosenbergii  

NASA Astrophysics Data System (ADS)

Endosulfan, an organochlorine pesticide, is highly toxic and effective at controlling pests in agriculture, horticulture, and public health programs. In this study, static bioassays were used to evaluate the toxicity of endosulfan to freshwater prawns ( Macrobrachium rosenbergii) of various lengths (1.5±0.03, 4±0.08, and 7±0.06 cm). Additionally, the activities of peroxidase (POD), acid phosphatase (ACP), alkaline phosphatase, acetylcholinesterase (AChE), and Na+/K+-ATPase were analyzed to reflect the effects of endosulfan exposure. The 96 h LC50 of endosulfan for prawns 1.5, 4, and 7 cm long were 1.86, 4.53, and 6.09 ?g/L, respectively, improved tolerance to endosulfan with growth. The POD activities of test organisms exposed to low concentrations of endosulfan were inhibited, indicating the presence of oxygen damaged tissue. Moreover, a notable decrease in AChE activity was observed due to overstimulation of neurotransmission, which might result in abnormal behavior. The effect caused by endosulfan on phosphatase production in the hepatopancreas of prawns 1.5, 4, and 7 cm long was different because the ability of nonspecific immune regulation increased with growth. The 96 h LC50 values obtained in this study could be used in the formulation of water-quality criteria in China. Moreover, the changes in enzymes activities of M. rosenbergii under stress of endosulfan could be applied in the establishment of early warning indicators for bio-safety.

Dai, Xilin; Xiong, Zhaodi; Xie, Jian; Ding, Fujiang

2014-01-01

339

Nutrient Budgets and Effluent Characteristics in Giant Freshwater Prawn (Macrobrachium rosenbergii) Culture Ponds.  

PubMed

It is important to understand nutrient budgets of aquaculture practices for efficiency of input resources and to utilize all output nutrient sources. The aim of the present study was to develop a nutrient budget for giant freshwater prawn (Macrobrachium rosenbergii) culture ponds. The study was conducted in farmer's ponds (0.25-0.5 ha) of Odisha, India, and the results showed that feed accounted 97 % total nitrogen (N), 98.7 % total phosphorus (P) and 90 % total organic carbon (OC), respectively. The harvested prawn accounted for recovery of 37 % N, 10 % P and 15 % OC, respectively. The N, P and OC accumulated in sediment were 52 %, 76 %, and 65 %, respectively. Nutrient loads in the effluents were 2.22 ± 0.66 kg inorganic N, 0.40 ± 0.15 kg P, and 21.01 ± 6.4 kg OC per ton of prawn production. The present study implicated that high nutrient values observed in both water and sediment provide important opportunities for nutrient reuse through pond sediment applications to croplands as an organic manure, as well as pond water irrigation to crops as a "liquid fertilizer". PMID:24522829

Adhikari, Subhendu; Sahu, Bharat Chandra; Mahapatra, Abhijit S; Dey, Lambodar

2014-05-01

340

Follow-up of mercury levels in fish, human hair and urine in the Madeira and Tapajós basins, Amazon, Brazil  

Microsoft Academic Search

Informal economy of gold mining has contaminated some important river basins in Amazon. Follow-up studies on critical compartments showed some areas with high Hg levels in fish as well as in human hair samples. Average Hg in piscivorous fish in the Madeira river itself was 846 ppb (N=284) with a maximum of 3921 ppb. Mercury in fish from non polluted

O Malm; JRD Guimarães; MB Castro; WR Bastos; JP Viana; FJP Branches; EG Silveira; WC Pfeiffer

1997-01-01

341

Low-water maps of the groundwater table in the central Amazon by satellite altimetry  

NASA Astrophysics Data System (ADS)

plays a fundamental role in rainforest environments, as it is connected with rivers, lakes, and wetlands, and helps to support wildlife habitat during dry periods. Groundwater reservoirs are however excessively difficult to monitor, especially in large and remote areas. Using concepts from groundwater-surface water interactions and ENVISAT altimetry data, we evaluated the topography of the groundwater table during low-water periods in the alluvial plain of the central Amazon. The water levels are monitored using an unprecedented coverage of 491 altimetric stations over surface waters in the central Amazon. The groundwater table maps interpolated at spatial resolutions ranging from 50 to 100 km are consistent with groundwater wells data. They provide evidence of significant spatiotemporal organization at regional scale: heterogeneous flow from the hillslope toward the main rivers is observed, as well as strong memory effects and contrasted hydrological behaviors between the North and the South of the Amazon.

Pfeffer, Julia; Seyler, Frédérique; Bonnet, Marie-Paule; Calmant, Stéphane; Frappart, Frédéric; Papa, Fabrice; Paiva, Rodrigo C. D.; Satgé, Frédéric; Silva, Joecila Santos Da

2014-03-01

342

Deforestation, floodplain dynamics, and carbon biogeochemistry in the Amazon Basin  

NASA Astrophysics Data System (ADS)

Three aspects of the physical geographic environment of the Amazon Basin are considered: (1) deforestation and reforestation, (2) floodplain dynamics, and (3) fluvial geomorphology. Three independent projects are coupled in this experiment to improve the in-place research and to ensure that the Shuttle Imaging Radar-B (SIR-B) experiment stands on a secure base of ongoing work. Major benefits to be obtained center on: (1) areal and locational information, (2) data from various depression angles, and (3) digital radar signatures. Analysis will be conducted for selected sites to define how well SIR-B data can be used for: (1) definition of extent and location of deforestation in a tropical moist forest, (2) definition and quantification of the nature of the vegetation and edaphic conditions on the (floodplain) of the Amazon River, and (3) quantification of the accuracy with which the geometry and channel shifting of the Amazon River may be mapped using SIR-B imagery in conjunction with other remote sensing data.

Bryan, M. L.; Dunne, T.; Richey, J.; Melack, J.; Simonett, D. S.; Woodwell, G.

1984-07-01

343

Deforestation, floodplain dynamics, and carbon biogeochemistry in the Amazon Basin  

NASA Technical Reports Server (NTRS)

Three aspects of the physical geographic environment of the Amazon Basin are considered: (1) deforestation and reforestation, (2) floodplain dynamics, and (3) fluvial geomorphology. Three independent projects are coupled in this experiment to improve the in-place research and to ensure that the Shuttle Imaging Radar-B (SIR-B) experiment stands on a secure base of ongoing work. Major benefits to be obtained center on: (1) areal and locational information, (2) data from various depression angles, and (3) digital radar signatures. Analysis will be conducted for selected sites to define how well SIR-B data can be used for: (1) definition of extent and location of deforestation in a tropical moist forest, (2) definition and quantification of the nature of the vegetation and edaphic conditions on the (floodplain) of the Amazon River, and (3) quantification of the accuracy with which the geometry and channel shifting of the Amazon River may be mapped using SIR-B imagery in conjunction with other remote sensing data.

Bryan, M. L.; Dunne, T.; Richey, J.; Melack, J.; Simonett, D. S.; Woodwell, G.

1984-01-01

344

Atmospheric mercury concentrations in the basin of the amazon, Brazil.  

PubMed

A wide regional mercury pollution in Amazon, Brazil is closely associated with goldmining that has been carried out in the basin of tributaries of the Amazon since the eighteenth century. Possible involvement has been discussed on atmospheric circulation in distributing the volatile pollutant. We developed a portable air sampler for the collection of mercury compounds and determined atmospheric mercury concentrations at several sites in Brazil including the basin of the Amazon tributaries. The mean concentration of total mercury was between 9.1 and 14.0 ng/m(3) in the basin of the Uatumã River located in the tropical rain forest far from goldmining sites and from urbanized area. These mercury levels exceeded the background level previously reported in rural area and, furthermore, were higher than concentrations observed in Rio de Janeiro and in Manaus that were compatible with the reference values for urban area. Mercury concentrations were also determined in gold refineries in the basin of the Tapajos River, and detected at a significant but not a health deteriorating level. Although only preliminary data were available, the present observations were in favor of the hypothesis that mercury is distributed widely by long distant transport by the atmospheric circulation after released at gold mining sites. PMID:21432539

Hachiya, N; Takizawa, Y; Hisamatsu, S; Abe, T; Abe, Y; Motohashi, Y

1998-01-01

345

Ballast water: A threat to the Amazon Basin.  

PubMed

Ballast water exchange (BWE) is the most efficient measure to control the invasion of exotic species from ships. This procedure is being used for merchant ships in national and international voyages. The ballast water (BW) salinity is the main parameter to evaluate the efficacy of the mid-ocean ballast water exchange. The vessels must report to the Port State Control (PSC), via ballast water report (BWR), where and how the mid-ocean BWE was performed. This measure allows the PSC to analyze this information before the ship arrives at the port, and to decide whether or not it should berth. Ship BW reporting forms were collected from the Captaincy of Santana and some ships were visited near the Port of Santana, located in Macapá (Amazon River), to evaluate the BW quality onboard. We evaluated data submitted in these BWR forms and concluded that the BWE efficacy might be compromised, because data contained in these BWR indicate that some ships did not change their BW. We found mistakes in filling the BWR forms and lack of information. Moreover, these ships had discharged BW with high level of salinity, Escherichia coli and total coliforms into the Amazon River. We concluded that the authorities of the Amazon Region need to develop more efficient proceedings to evaluate the ballast water reporting forms and BW quality, as there is potential risk of future invasion of exotic species in Brazilian ports. PMID:24928458

Pereira, Newton Narciso; Botter, Rui Carlos; Folena, Rafael Dompieri; Pereira, José Pinheiro Fragoso Neto; da Cunha, Alan Cavalcanti

2014-07-15

346

Effects of different fertilization and feeding regimes on the production of integrated farming of rice and prawn Macrobrachium rosenbergii (De Man)  

Microsoft Academic Search

An experiment was conducted in rice fi eld plots each of 30 m 2 to determine the appropriate combination of feeding and fertilization regimes for the giant freshwater prawn Macrobrachium rosenbergii (De Man. 1979) cultured along with rice in rice fi elds. There were four treatments: rice culture only with regular fertilization (A, control); rice-prawn integrated culture with regular fertilization

Dao Huy Giap; Yang Yi; Chang Kwei Lin

2005-01-01

347

Capture efficiency of the freshwater prawn Palaemonetes argentinus (Nobili 1901) on the Culex pipiens s.l. (Linnaeus 1758) mosquitoes larvae  

Microsoft Academic Search

The predation consists of a chain of events divided in three phases: encounter, capture and ingestion. We filmed the prawn Palaemonetes argentinus depredate on mosquitoes larvae (Culex pipiens s.l.) in aquaria, watching an increment in the swimming activity of prawns then to recognize the movement of the larvae by mechanoreceptors. The encounters of prey demand in the aquaria with small

Federico Giri; Pablo Collins; José Maciá

2004-01-01

348

Effect of Trap Soak-Time on the Trap-Selectivity Profile and By-Kill in Prawn-Trap Fisheries  

Microsoft Academic Search

Canada's Department of Fisheries and Oceans seeks to manage British Columbia's prawn fishery by limiting the season length, vessel entry, and the number of prawn traps per vessel. However, fishers can still adjust their effort by increasing the number of trap lifts during the season. This study examines the effect of trap soak-time on size-selectivity, looks at how it translates

Christopher S. Wright; Peter Panek

349

New sediment budget calculations for the submarine Amazon Delta indicates enhanced modern sediment fluxes of the Amazon system  

NASA Astrophysics Data System (ADS)

The submarine Amazon Delta is one major sink in the Amazon source-to-sink system. It is estimated, that the Amazon transports around 1200 Mt/yr. Around 50% of this river sediment load, namely 400 - 800 Mt/yr, is stored on the submarine delta, leading to sedimentation rates of decimeters per year (Nittrouer et al., 1995). The majority of the remaining sediments is deposited on the lower delta plain of the Amazon, but another significant portion is accumulated at the Amapa shoreline or is bypassed further northwestwards. These sediment budget calculations are mainly based on radioisotopic profiles measured at sediment cores in the frame of the AmasSeds project, which was carried out in the 1980ties and 1990ties (Nittrouer et al., 1995). Here we present another approach for calculating mass fluxes in the Amazon system. Within the Project AMADEUS, a cooperation between the MARUM, Bremen, Germany and the University Sao Paulo, Brazil, high-resolution seismic multichannel seismic data and sediment echosounder data (PARASOUND) were collected during Cruise MSM20/3 in February/March 2012. Main emphases of the surveying were set to the forset and bottomset of the delta, where most of the accretion occurs. A special outcome of the new data is the comparison with PARASOUND data collected in 1996 during Cruise M34/4. Due to several crossing points of both data sets it is now possible to carry out direct measurements of the accumulation during these 16 years. Another time horizon is a prominent unconformity spreading over the submarine delta, since the sedimentation on top of this unconformity had been dated to start roughly 100 yrs ago (Sommerfield et al., 1995). Mapping of this unconformity as well as the reflector representing the seafloor of 1996 gives the opportunity to calculate volumes and mass of the sediment stored within the survey area for two different time spans. First calculations show, that the sediment accumulation on the submarine delta since 1996 is significantly enhanced compared to the 100 years before. Also the comparison of the accumulation from 1996 to 2012 with results from the AmasSeds project suggests that the storage of sediments notably increased within the last decades. Even the main survey area of MSM 20/3 comprises just <20% of the area of the entire submarine delta, the mass of sediments accumulated there is in the same order of magnitude as calculated for the complete submarine delta by Nittrouer et al. (1995). Additionally, a notable deposition between 1996 and 2012 is observed outside of the main survey area. These results indicate a considerable increase of the sediment delivery by the Amazon River in recent times instead of just a reorganization of the sediment distribution, which finally may suggest amplified erosion in the Amazon Basin. However, this new calculation gives a valuable contribution to understand the modern Amazon source-to-sink system. References: C. A. Nittrouer, S. A. Kuehl, R. W. Sternberg, A. G. Figueiredo Jr., L. E.C. Faria, 1995, An introduction to the geological significance of sediment transport and accumulation on the Amazon continental shelf, Marine Geology, 125, p. 177-192. C. K. Sommerfield, C. A. Nittrouer, A. G. Figueiredo, Stratigraphic evidence of changes in Amazon shelf sedimentation during the late Holocene, 1995, Marine Geology, 125, p. 351-371.

Schwenk, T.; Haberkern, J.; Mulitza, S.; Chiessi, C. M.

2013-12-01

350

New sediment budget calculations for the submarine Amazon Delta indicates enhanced modern sediment fluxes of the Amazon system  

NASA Astrophysics Data System (ADS)

The submarine Amazon Delta is one major sink in the Amazon source-to-sink system. It is estimated, that the Amazon transports around 1200 Mt/yr. Around 50% of this river sediment load, namely 400 - 800 Mt/yr, is stored on the submarine delta, leading to sedimentation rates of decimeters per year (Nittrouer et al., 1995). The majority of the remaining sediments is deposited on the lower delta plain of the Amazon, but another significant portion is accumulated at the Amapa shoreline or is bypassed further northwestwards. These sediment budget calculations are mainly based on radioisotopic profiles measured at sediment cores in the frame of the AmasSeds project, which was carried out in the 1980ties and 1990ties (Nittrouer et al., 1995). Here we present another approach for calculating mass fluxes in the Amazon system. Within the Project AMADEUS, a cooperation between the MARUM, Bremen, Germany and the University Sao Paulo, Brazil, high-resolution seismic multichannel seismic data and sediment echosounder data (PARASOUND) were collected during Cruise MSM20/3 in February/March 2012. Main emphases of the surveying were set to the forset and bottomset of the delta, where most of the accretion occurs. A special outcome of the new data is the comparison with PARASOUND data collected in 1996 during Cruise M34/4. Due to several crossing points of both data sets it is now possible to carry out direct measurements of the accumulation during these 16 years. Another time horizon is a prominent unconformity spreading over the submarine delta, since the sedimentation on top of this unconformity had been dated to start roughly 100 yrs ago (Sommerfield et al., 1995). Mapping of this unconformity as well as the reflector representing the seafloor of 1996 gives the opportunity to calculate volumes and mass of the sediment stored within the survey area for two different time spans. First calculations show, that the sediment accumulation on the submarine delta since 1996 is significantly enhanced compared to the 100 years before. Also the comparison of the accumulation from 1996 to 2012 with results from the AmasSeds project suggests that the storage of sediments notably increased within the last decades. Even the main survey area of MSM 20/3 comprises just <20% of the area of the entire submarine delta, the mass of sediments accumulated there is in the same order of magnitude as calculated for the complete submarine delta by Nittrouer et al. (1995). Additionally, a notable deposition between 1996 and 2012 is observed outside of the main survey area. These results indicate a considerable increase of the sediment delivery by the Amazon River in recent times instead of just a reorganization of the sediment distribution, which finally may suggest amplified erosion in the Amazon Basin. However, this new calculation gives a valuable contribution to understand the modern Amazon source-to-sink system. References: C. A. Nittrouer, S. A. Kuehl, R. W. Sternberg, A. G. Figueiredo Jr., L. E.C. Faria, 1995, An introduction to the geological significance of sediment transport and accumulation on the Amazon continental shelf, Marine Geology, 125, p. 177-192. C. K. Sommerfield, C. A. Nittrouer, A. G. Figueiredo, Stratigraphic evidence of changes in Amazon shelf sedimentation during the late Holocene, 1995, Marine Geology, 125, p. 351-371.

Schwenk, T.; Haberkern, J.; Mulitza, S.; Chiessi, C. M.

2011-12-01

351

Examining how land surface effects modulate rainfall in the eastern Amazon Basin  

NASA Astrophysics Data System (ADS)

In the Amazon, it is important to apportion rainfall by storm type. In the eastern Amazon (approximately from Belém to Santarém) rainfall associated with large instability lines produces nearly half of the total, and this is complemented by that produced by rainfall from local convective systems. Our recent observational studies in the indicate that the relative importance of the nocturnal squall lines is exaggerated if one relies solely on data from the climate stations along the Amazon River channel. River breezes inhibit convective rainfall near the main channel, but in some areas river proximity effects lead to enhanced nocturnal rainfall of squall origin. Moreover, enhanced rainfall to the north of the Amazon main channel could be the result of orographic uplift. In this study we complement a limited climatological study of instability lines with two mesoscale model (Brazilian version of RAMS, B-RAMS) case studies to examine the effects of topography and river proximity on rain producing mechanisms in the eastern Amazon Basin. Two numerical experiments were done to examine the relative importance of these two rain-producing mechanisms in the region. In each, three nested grids were used. Results from the prototype simulation for the propagating squall line were compared with GOES images, NCEP reanalyses, and data from the LBA-ECO surface station network near Santarém (approximately 55°W). In this case we also examined the role of topography on squall line development by performing a sensitivity test of the case study squall development with and without topography. The locally-dominated convection study was based on a case of slack easterlies during cold frontal penetration into the western Amazon region.

Fitzjarrald, D.; Cohen, J. P.

2009-05-01

352

Bilingual Education and Language Use among the Shipibo of the Peruvian Amazon.  

ERIC Educational Resources Information Center

Investigates how language choice for education contributes to changes in the way a society views and uses language in the context of the Peruvian Amazon. Oral surveys were administered to Shipibo people in 13 communities along the Ucayali River of eastern Peru where a transition type bilingual education program was introduced several decades ago.…

Tacelosky, Kathleen

2001-01-01

353

Trophic Structure and Bioaccumulation of Mercury in Fish of Three Natural Lakes of the Brazilian Amazon  

Microsoft Academic Search

The bioaccumulation of mercury by fish was studied in three natural lakes lining the Tapajós River, Brazilian Amazon. The Hg content variations are also reported between the rainy and the rising water seasons. Position of fish in the food chain and the source of carbon at the base of the food chain were determined using nitrogen and carbon stable isotopes

D. Sampaio Da Silva; M. Lucotte; M. Roulet; H. Poirier; D. Mergler; E. Oliveira Santos; M. Crossa

2005-01-01

354

Seasonal and habitat differences in the abundance of primates in the Amazon (Tapajos) National Park, Brazil  

Microsoft Academic Search

Twelve species of primates occur in the Amazon (Tapajs) National Park. The abundance of these species varies with habitat\\u000a type and extent of human disturbance. Seasonality of rainfall and river level significantly affect the abundance of primates\\u000a in seasonally inundated forest but not in upland forest types.

Lyn C. Branch

1983-01-01

355

CTD Observations on the North Brazil Shelf During A Multidisciplinary AMazon Shelf SEDiment Study (AMASSEDS).  

National Technical Information Service (NTIS)

Hydrographic (CTD) and acoustic Doppler current profiler (ADCP) observations were made on the North Brazil shelf adjacent to the mouth of the Amazon River. These observations were obtained during a large-scale survey on Leg 3 in support of geological and ...

R. Limeburner I. D. Soares J. Candela R. C. Beardsley

1992-01-01

356

Stratigraphic age, sedimentation rate and source rocks of the Amazon Fan  

NASA Astrophysics Data System (ADS)

The evolution of Amazon Fan, a large sedimentary structure at the Brazilian passive margin, is directly connected with the Andean mountains and the Amazon River development. Sr, Nd and Pb isotopes studies combined with palynological information have been conducted in Late Miocene to Pleistocene section of the Amazon submarine fan to constrain the sedimentary age, source rocks and sedimentation rate of main sedimentary sequences deposited during the period. Age of the sedimentary rocks were inferred from the palynological data and Sr isotope signature from foraminifers, integrated with seismic and drill holes data. The whole section had a very high sedimentation rate with significant increase in the last 3 Ma, from Late Pliocene to present, which it may be related to uplift of the continental margin as a result of isotastic compensation due to load of Amazon Fan sedimentary package deposited from Late Miocene to Early Pliocene and main uplift of the Northern Andes. Although the most foraminifera shells have 87Sr/86Sr ratio in the range of the expected value for the estimated age, there were samples with 87Sr/86Sr ratio lower and higher than those used for the Sr isotope curve. The increase of 87Sr/86Sr ratio is assigned to Amazon River strontium fluxes whereas lower ratios may be due to diagenetic processes or fluid percolation driven by thick sedimentary overload, as much as 10,000 m, in the Amazon submarine fan. Contribution of the Precambrian rocks of the Amazonian Craton versus Andean rocks as source of the sediments for Amazon Fan during its evolution was estimated by the Sm-Nd and Pb isotope data in the pelitic rocks. Nd and Pb isotopes in fine-grained sediments allowed to identify both signal, where contribution Precambrian basement rocks are recognized by Archean and Paleoproterozoic Nd model ages and higher radiogenic Pb signature.

Chemale Junior, Farid; Ayup, Ricardo N.; Barboza, Eduardo; Moura, Candido A. V.

2014-05-01

357

Nutrient dynamics in Amazon shelf waters: results from AMASSEDS  

NASA Astrophysics Data System (ADS)

Four hydrographic cruises were conducted on the Amazon shelf as part of the AMASSEDS field program. During each cruise, approximately 55 stations were occupied and nutrients, as well as other hydrographic parameters, were measured. The results of this time series sampling program indicate that the nutrient concentrations in the riverine end-member (silicate = 144 ?mol kg -1, phosphate = 0.7 ?mol kg -1, nitrate = 16 ?mol kg -1, ammonium = 0.4 ?mol kg -1, and urea = 0.9 ?mol kg -1) remain relatively constant, despite a two-fold seasonal variation in river water discharge rate. Of the major nutrients (nitrate, phosphate, ammonium and silicate), nitrate shows the greatest seasonal change in riverine end-member concentration with a high value (23 ?mol kg -1) during the March cruise (rising river discharge) and a low value (12 ?mol kg -1) during the November cruise (falling river discharge). Nitrate is the dominant nutrient form of inorganic nitrogen throughout most of the river/ocean mixing zone, however, in the outershelf area, where nitrate has been depleted by biological production, this nutrient occurs at concentrations comparable to the other nitrogen species (ammonium, nitrite and urea), which are at levels < 1 ?mol kg -1. Nearshore, high turbidity inhibits phytoplankton production because of light limitation, whereas on the outershelf, nitrate appears to be limiting growth more than silicate or phosphate. Nutrient uptake was observed during all four cruises, however, nearly all of this production must be regenerated in shelf bottom waters, because very little of the biogenic materials are buried in the seabed (silicate burial <4% of flux to algal blooms; ˜10% burial of biologically available inorganic nitrogen reaching the river/ocean mixing zone; and <3% burial of phosphate flux to shelf environment). Clearly the Amazon shelf is not an efficient nutrient trap. Initial estimates of primary production on the Amazon shelf suggest that algal blooms are sustained by regeneration to a large extent (up to 83%, 69% and 59% for N, P and Si, respectively) as well as by riverine and upwelled sources. Nutrient budget calculations have been used to establish the dominant external source of nutrients to the algal blooms occurring on the outer shelf. Based on flux core measurements, diffusive nutrient fluxes from Amazon shelf sediments are very low relative to riverine supply rates (silicate flux out = 1.3% of riverine flux, the nitrate plus ammonium flux is essentially zero, and the phosphate seabed flux shows removal of ˜2% of the riverine flux). Inventories of naturally occurring 210Pb were used to estimate the onshore flow of subsurface water onto the Amazon shelf. The radiochemical data indicate that the flux of water onto the shelf may be as much as five to ten times greater than the annual flow of the Amazon River. The nutrient flux from this shoreward movement of ocean water (originating at a depth of 60-100 m water depth) accounts for about 80% of the externally supplied ammonium, 52% of the externally supplied phosphate, 38% of the externally supplied nitrate, and 17% of the externally supplied silicate reaching the outer shelf, with the remainder of the nutrient fluxes coming from the river. Therefore, the outershelf algal blooms are supported to a significant extent by the shoreward flux of nutrients from offshore, subsurface waters.

Demaster, David J.; Pope, Robert H.

1996-03-01

358

Challenges in understanding the sources of bioaccumulated metals in biota inhabiting turbid river systems.  

PubMed

Bioaccumulation of As, Cd, Cu, Pb and Zn by Macrobrachium prawns was observed to occur in the Strickland River downstream of a gold mine at Porgera, Papua New Guinea. This was despite the total metal concentrations of waters and sediments indicating no difference from reference sites within tributaries. To provide information on potential sources and bioavailability of metals to prawns, an extensive range of analyses were made on waters, suspended solids, deposited sediments and plant materials within the river system. Dissolved metal concentrations were mostly sub-micrograms per liter and no major differences existed in concentrations or speciation between sites within the Strickland River or its tributaries. Similarly, no differences were detected between sites for total or dilute acid-extractable metal concentrations in bed sediments and plant materials, which may be ingested by the prawns. However, the rivers in this region are highly turbid and the dilute acid-extractable cadmium and zinc concentrations in suspended solids were greater at sites in the Strickland River than at sites in tributaries. The results indicated that mine-derived inputs increased the proportion of these forms of metals or metalloids in the Strickland River. These less strongly bound metals and metalloids would be more bioavailable to the prawns via the dietary pathway. The results highlighted many of the difficulties in using routine monitoring data without information on metal speciation to describe metal uptake and predict potential effects when concentrations are low and similar to background. The study indicated that the monitoring of contaminant concentrations in organisms that integrate the exposure from multiple exposure routes and durations may often be more effective for detecting impacts than intermittent monitoring of contaminants in waters and sediments. PMID:24014223

Cresswell, Tom; Smith, Ross E W; Simpson, Stuart L

2014-02-01

359

Modelling sustainable international tourism demand to the Brazilian Amazon  

Microsoft Academic Search

The Amazon rainforest is one of the world's greatest natural wonders and holds great importance and significance for the world's environmental balance. Around 60% of the Amazon rainforest is located in the Brazilian territory. The two biggest states of the Amazon region are Amazonas (the upper Amazon) and Pará (the lower Amazon), which together account for around 73% of the

Jose Angelo Divino; Michael Mcaleer

2009-01-01

360

Central Amazon Floodplain Hydrodynamics  

NASA Astrophysics Data System (ADS)

Amazon floodplain wetlands contain high biological diversity for which the flow regime, particularly the flood-pulse, provides the driving force. Surface water flow is recognized as the key factor in the establishment and maintenance of wetland ecosystems and their functioning, exerting a strong control on channel formation and determining the spatial and temporal complexity of wetland habitats. However, the hydrodynamics of seasonally flooded wetlands in the Amazon basin remains poorly quantified through ground observations, satellite observations or modelling. In this research, fieldwork was conducted between March and August 2012 for 850 km^{2} of várzea floodplain to the south of a 75 km reach of the Rio Solimões, downstream (east) of the confluence with the Rio Purus. The primary aim of this was to collect ground-based measurements of surface water flows from mid-rising, through high-water to mid-falling flood conditions to allow a detailed picture of floodplain hydrodynamics to be constructed. Four 10-day periods of fieldwork were completed, during which measurements were taken at 42 locations along the floodplain channel network and in floodplain lakes, together with main channel measurements on the Solimões and Purus. Measurements were obtained of: (i) flow rates along floodplain channels, using an Acoustic Current Doppler Profiler (ADCP); (ii) runoff from terra firma via measurement of flows out of ria lakes at the southern edge of the floodplain; (iii) water conductivity; and (iv) suspended sediment concentrations. Overbank flow rates from the Rio Solimões and Rio Purus into the floodplain forest were also obtained using a current meter at several locations during high water. In addition, floodplain channel and lake depths were obtained using continuous recording of sonar connected to a Global Positioning System, enabling the estimation of bathymetry. Using these measurements, detailed hydrodynamic maps of the floodplain were produced from mid-rising to mid-falling flood stages. Initial results show that floodplain channels play an important role in floodplain hydrodynamics, carrying the bulk of flood water into the floodplain during rising water. Once main-channel water levels are above-bankfull, overbank flow directly into the floodplain forest becomes significant. At high-water, the flow rate out of the Purus along the major floodplain channel was 2,200 m^{3}s^{-1}, representing around 10% of the total Purus channel flow ( 23,000 m^{3}s^{-1} at Beruri). In addition, an estimated 2,000 - 4,000 m^{3}s^{-1} of overbank flow occurred from the lower Purus into the floodplain. Floodplain channel flow from the Solimões was less significant than from the Purus at less than 1,000 m^{3}s^{-1}, under 1% of Solimões channel flow ( 116,000 m^{3}s^{-1} upstream of the Purus); however overbank flow into the floodplain forest may have been as much as 10,000 m^{3}s^{-1} along the study reach. Terra firma runoff, measured at the outflows of ria lakes, contributed an insignificant amount of flow during the measurement periods. The first-order estimate of flow through the floodplain area during high water was 15,000 to 17,000 m^{3}s^{-1} (an average of 17.6 to 20.0 m^{3}s^{-1} per km^{2}), with 30-40% of the flow contributed by the Purus.

Wilson, M. D.; Vega, M. C.; Forsberg, B. R.

2012-12-01

361

Are severe droughts in western Amazon here to stay?  

NASA Astrophysics Data System (ADS)

Droughts do not immediately come to mind when one thinks of climate extremes that impact western Amazon (WA), where luscious green rainforest predominates. However, droughts in recent years have made the news due to their large socio-economic impacts, such as increased occurrence of fires, respiratory problems related to smoke and reduced fisheries and fluvial transportation due to low river levels. The two most recent notorious droughts in the region were those of 2005 and 2010, both referred to as a "100-year drought". Whether the severity of recent droughts is related to low frequency natural climate variability and/or climate change is not clear. To assess the relative importance of different modes of temporal variability on WA precipitation we calculate the dry season months (JAS) Standardized Precipitation Index (SPI) from two gridded precipitation datasets over a period of 76 years and statistically decompose them into interannual, inter-decadal and trend components. The same analysis is done for the Negro River standardized minimum water level, a major Amazon tributary for which nearly 100 years of data can be obtained. As we will show, the majority of the total variance of SPI from both precipitation datasets and minimum river water level is explained by internannual variability, and the least by trend. Additionally, the dry season precipitation variability in this region is shown to respond to anomalous North Tropical Atlantic (NTA) sea surface temperature (SST), especially over the last 15 years. To explore whether the different time scales of JAS SPI show similar relationship over the longer time period available (76 yrs), the partitioned time series are correlated to averaged April through September tropical SST. We find the strongest relationship to be with the north-south tropical Atlantic SST gradient (not the NTA alone) in both interannual and inter-decadal time scales, whereas the variability of tropical Pacific SST, know to affects eastern Amazon precipitation, shows no significant relationship to WA JAS SPI variability.

Fernandes, K.; Goddard, L.; Baethgen, W.; Pinedo-Vasquez, M.

2012-12-01

362

Bacterial flora associated with larval rearing of the giant freshwater prawn, Macrobrachium rosenbergii  

Microsoft Academic Search

Quantitative and qualitative analyses of bacterial flora associated with larval rearing of the giant freshwater prawn, Macrobrachium rosenbergii, along with important water quality parameters, were carried out over a larval cycle. Total viable counts (TVC) varied between 1.1±0.6×104 and 9.8±1.5×106 colony forming units (cfu) ml?1 in water, 2.4±0.4×105 and 8.6±1.6×106 cfu g?1 in eggs and 2.5±1.4×104 and 1.6±1.0×108 cfu g?1

P. V. Phatarpekar; V. D. Kenkre; R. A. Sreepada; U. M. Desai; C. T. Achuthankutty

2002-01-01

363

Amazon Deforestation and Climate Change  

Microsoft Academic Search

A coupled numerical model of the global atmosphere and biosphere has been used to assess the effects of Amazon deforestation on the regional and global climate. When the tropical forests in the model were replaced by degraded grass (pasture), there was a significant increase in surface temperature and a decrease in evapotranspiration and precipitation over Amazonia. In the simulation, the

J. Shukla; C. Nobre; P. Sellers

1990-01-01

364

Finding Food in the Amazon  

NSDL National Science Digital Library

In this activity, the students will investigate a variety of plants and animals common to the Amazon through research. They will determine the plant or animal characteristics that make them edible or useful for the trip and learn to categorize them by comparing similarities and/or differences.

Adventure Engineering

365

Amazon RainForest Fires  

Microsoft Academic Search

Charcoal is common in the soils of mature rain forests within 75 kilometers of San Carlos de Rio Negro in the north central Amazon Basin. Carbon-14 dates of soil charcoal from this region indicate that numerous fires have occurred since the mid-Holocene epoch. Charcoal is most common in tierra firme forest Oxisols and Ultisols and less common in caatinga and

Robert L. Sanford; Juan Saldarriaga; Kathleen E. Clark; Christopher Uhl; Rafael Herrera

1985-01-01

366

Cyclic sediment deposition within Amazon deep-sea fan  

SciTech Connect

The Upper and middle Amazon Fan has grown in a cyclic fashion. An individual deposition cycle consists of (1) a widespread basal, acoustically transparent seismic unit (interpreted as debris-flow deposits) that fills and levels preexisting topographic lows, and (2) a levee complex built of overlapping channel-levee systems. Two and possibly three cycles have been identified within the Amazon Fan. The levee complex beneath one debris flow originated from a different submarine canyon than did the levee complex above the debris flow, suggesting that these levee complexes formed during different sea level lowstands. Calculations based on present sediment discharge of the Amazon River suggest that an entire levee complex can form within the time span of a single glacial stage, such as the Wisconsin; however, the levee complex probably could not have formed during the relatively short time interval when sea level rose rapidly at the end of a glacial stage. The basal seismic units (debris-flow deposits) may have been deposited at any time during sea level fluctuations. Although seismic evidence suggests that this cyclic sedimentation pattern may be related to glacio-eustatic sea level variations, cyclic fan growth may be attributed to other processes as well. For example, a bottom-simulating reflector (BSR) observed within the upper fan appears to be a gas hydrate. Migration of the hydrate phase boundary during sea level fluctuations and diapiric activity may be mechanisms for initiating widespread debris flows. 10 figs.

Manley, P.L.; Flood, R.D.

1988-08-01

367

Population dynamics of Niger River prawn (Macrobrachium felicinum) in Lower Taylor Creek, Niger Delta, Nigeria  

Microsoft Academic Search

The population dynamics of Macrobrachium felicinum (Holthuis, 1949) in Lower Taylor Creek, Niger Delta, Nigeria, was analysed using monthly length-frequency data (June 2008 – May 2010). This study was aimed at determining the status of fishery and establishing the levels of exploitation that will give sustainable yields. The FAO-ICLARM stock assessment tool (FISAT II) software was used to estimate population

T onbarapagha Kingdom; Aduabobo Ibitoruh Hart

2012-01-01

368

Uranium in river water  

SciTech Connect

The concentration of dissolved uranium has been determined in over 250 river waters from the Orinoco, Amazon, and Ganges basins. Uranium concentrations are largely determined by dissolution of limestones, although weathering of black shales represents an important additional source in some basins. In shield terrains the level of dissolved U is transport limited. Data from the Amazon indicate that floodplains do not represent a significant source of U in river waters. In addition, the authors have determined dissolved U levels in forty rivers from around the world and coupled these data with previous measurements to obtain an estimate for the global flux of dissolved U to the oceans. The average concentration of U in river waters is 1.3 nmol/kg, but this value is biased by very high levels observed in the Ganges-Brahmaputra and Yellow rivers. When these river systems are excluded from the budget, the global average falls to 0.78 nmol/kg. The global riverine U flux lies in the range of 3-6 [times] 10[sup 7] mol/yr. The major uncertainty that restricts the accuracy of this estimate (and that of all other dissolved riverine fluxes) is the difficulty in obtaining representative samples from rivers which show large seasonal and annual variations in runoff and dissolved load.

Palmer, M.R. (Univ. of Bristol (United Kingdom)); Edmond, J.M. (Massachusetts Inst. of Technology, Cambridge, MA (United States))

1993-10-01

369

hydrochemistry of the Andeans and sub-andeans Amazon basins - Weathering and CO2 consumption rates.  

NASA Astrophysics Data System (ADS)

Measuring mountain weathering rates, estimating their role on C cycle and identifying the parameters which control them are key to better constrain the knowledge of the continental-ocean-atmosphere interactions over geological timescale. The Andes, in contrast to the Himalaya, have received poor attention in terms of chemical weathering. Several authors have worked on the Amazon river basin, but it is difficult to assess the role of the Andes (10% of the surface area of the Amazon river basin) by only sampling the Amazon at mouth or sampling its largest tributaries. As shown by earlier works, the Upper-Amazon basins are the main matter source of the Amazon basin. The studied area participates at more than 70% of the Amazon weathering rates while it contributes to the total discharge on 30% for 27% of the total area. The studied area is comprised between latitude 0°47'N and 20°28'S and between longitude 79°36'W and 58°45'W and can be divided in three major hydrosystems (the Napo river at North, the Maranon-Ucayali rivers on the central part and the upper Madeira at south) which can be separated on Andes and sub-Andes parts. This work presents the results of the HYBAM research program (present-day hydro-geodynamics of the Amazon Basin) on the upper Amazon basin. The concentration of major elements was analyzed on a monthly basis, sampling at 26 gauging stations which include the Andean basins of the Amazon River and a part of the downstream catchment domain. The objectives of this work are i) calculate the major elements fluxes and their spatial distribution, ii) estimate the present-day rate of rock weathering, as well as the flux of atmospheric/soil CO2 consumption from total rock and silicate weathering, and iii) constrain the major environmental factor which controls the dissolved matter production using unique high temporal and spatial resolution data sampling. The main difficulty of studying large river geochemistry is to separate the main sources of the dissolved matter. Studying the temporal dynamic exportation of each element and their main associations helps to better constrain the main matter origin per sub basins and to identify the main processes of production. Variability of runoff rates and lithology between the 3 hydrosystems mainly explain the intersystem weathering rates variability. o The convergence of high runoff rates and main volcanic lithology on Napo basin implies a high weathering rate compared to other basins of the studied area and the main world basins. o Due to the high presence of evaporites and carbonates rocks, the Maranon and Ucayali hydrosystems controls more than 60% of the Amazon hydrochemistry. o Sandstone lithology and low runoff rates on Upper Madeira basins imply a poor contribution of this basin on Amazon dissolved load. Sub-andean plains basins can take place a major role on weathering balance. On the carbonates basins of Maranon Ucayali the subandes catchments contributes to more than 40% to the dissolved load of the hydrosystem. It can reflect the importance of the weathering of sediments exported from Andes or/and the importance of the upper plain weathering rate. The role of environmental parameters, which control those processes, can be partly constrained over the studied area and are compared to other world results. Those results give new keys to better understand the role of major orogenese zones on global weathering processes and its effect on C cycle.

Moquet, Jean-Sébastien; Crave, Alain; Viers, Jérome; Guyot, Jean-Loup; Lagane, Christelle; Sven Lavado Casimiro, Waldo; Pombosa, Rodrigo; Noriega, Luis; Chavary, Eduardo

2010-05-01

370

Act No. 24994 of 19 January 1989. Basic Law on the Rural Development of the Peruvian Amazon Region.  

PubMed

This Act sets forth the government's policy on rural development of the Peruvian Amazon region. Major objectives of the Act include the promotion of new rural settlements in the Amazon region, the promotion of migration from the Andes to the Amazon region, and the stimulation of agriculture, livestock, and forestry activities in the Amazon region. The following are the means that the government will use, among others, to attain these goals: 1) the development of Population Displacement Programmes, which will give individual persons and families economic and logistic support in moving; 2) the establishment of Civic Colonizing Services, temporary mobile units, which will offer settlers health services, education services, technical assistance with respect to agriculture and livestock, and promotional credits; 3) the creation of the Council for Amazon River Transport to coordinate and recommend activities to improve river transport; 4) the granting to settlers of land, free education for their children, medical care, technical training and assistance with respect to agriculture, and a supply of seeds; 5) the exemption of certain investors from payment of income taxes; and 6) the granting of a wide range of incentives for agricultural production. The Act also creates a Council for Planning and Development in the Amazon Region to draw up and approve a Plan for the Development of the Amazon Region. It calls for the rational use of the natural resources of the Amazon Region in the framework of preserving the ecosystem and preventing its ruin and delegates to the regional governments the authority to enter into contracts on the use of forest materials and to undertake reforestation programs. Finally, the Act provides various guarantees for the native population, including guarantees with respect to land and preservation of ethnic and social identity. PMID:12344257

1989-01-01

371

Can high-frequency sound affect gas-bubble dynamics? A study in the intact prawn Palaemon elegans.  

PubMed

Underwater sound beacons (pingers) are employed in professional and scientific diving for location and navigation. Previous studies have demonstrated that exposure to acoustic fields may lead to the emergence of bubbles and cavities in tissues by rectified diffusion. However, this issue was studied mainly in vitro in various gels and isolated tissues. In the present study, we used the intact prawn Palaemon elegans, whose transparent shell makes it possible to conduct continuous microscopic observation of gas-bubble dynamics in the intact living prawn, to study the effect of high-frequency sound. In a crossover designed experiment, prawns were exposed to hyperbaric pressure of 203 kPa for 10 min, followed by decompression at 40 m/min (control). This procedure was carried out in the study group during transmission of a 37-kHz, 0.25-W, 10-ms pulse width, 1 pulse/s pulse interval. A significant increase was found in the mean volume of bubbles present for a longer period of time, in a higher percentage of the high-frequency sound-exposed prawns. We suggest that this sound exposure causes more gaseous micronuclei to grow into bubbles, and more of the dissolved gas to shift into the gas phase. PMID:11179625

Arieli, Y; Arieli, R; Shupak, A

2000-11-01

372

Toxicity of Drilling Waste and Its Impact on Gill Structure of Post Larvae of Tiger Prawn (Penaeus monodon)  

Microsoft Academic Search

The study to evaluate the toxicity of used drilling muds (drilling wastes) and their impact on gill structure of the post larvae of tiger prawn Penaeus monodon has been done. The results showed that the 96 h LC50 of used drilling muds ranged from 30740 and 78271 ppm SPP. All toxicity values considered to be above the standard of Indonesian

Agoes Soegianto; Bambang Irawan; Mochammad Affandi

373

Prey ingestion and live food selectivity of marble goby ( Oxyeleotris marmorata) using rice field prawn ( Macrobrachium lanchesteri) as prey  

Microsoft Academic Search

Marble goby (Oxyeleotris marmorata), a carnivorous fish native to freshwater in Asia-Pacific region, is a high-valued species in many Asian countries. The present study consisting of three experiments was conducted to determine the appropriate density, size and ingestion time of marble goby fingerlings on rice field prawn (Macrobrachium lanchesteri) as prey. Results showed that the ingestion rate of marble goby

Nguyen Phu Hoa; Yang Yi

2007-01-01

374

Effect of crude oil petroleum hydrocarbons on protein expression of the prawn Macrobrachium borellii.  

PubMed

Hydrocarbon pollution is a major environmental threat to ecosystems in marine and freshwater environments, but its toxicological effect on aquatic organisms remains little studied. A proteomic approach was used to analyze the effect of a freshwater oil spill on the prawn Macrobrachium borellii. To this aim, proteins were extracted from midgut gland (hepatopancreas) of male and female prawns exposed 7 days to a sublethal concentration (0.6 ppm) of water-soluble fraction of crude oil (WSF). Exposure to WSF induced responses at the protein expression level. Two-dimensional gel electrophoresis (2-DE) revealed 10 protein spots that were differentially expressed by WSF exposure. Seven proteins were identified using MS/MS and de novo sequencing. Nm23 oncoprotein, arginine methyltransferase, fatty aldehyde dehydrogenase and glutathione S-transferase were down-regulated, whereas two glyceraldehyde-3-phosphate dehydrogenase isoforms and a lipocalin-like crustacyanin (CTC) were up-regulated after WSF exposure. CTC mRNA levels were further analyzed by quantitative real-time PCR showing an increased expression after WSF exposure. The proteins identified are involved in carbohydrate and amino acid metabolism, detoxification, transport of hydrophobic molecules and cellular homeostasis among others. These results provide evidence for better understanding the toxic mechanisms of hydrocarbons. Moreover, some of these differentially expressed proteins would be employed as potential novel biomarkers. PMID:23570752

Pasquevich, M Y; Dreon, M S; Gutierrez Rivera, J N; Vázquez Boucard, C; Heras, H

2013-05-01

375

Impact of TBT on the vitellogenesis and sex hormones in freshwater prawn Macrobrachium rosenbergii (De Man, 1879)  

PubMed Central

Background Tributyltin (TBT) is a ubiquitous persistent xenobiotic that can be found in freshwater, estuarine and marine ecosystem. TBT is a strong endocrine disrupting compound (EDC) that can cause toxic threat to aquatic organisms. Imposex, sexual deformities and endocrine dysfunctions are the causes of TBT to most of the aquatic organisms. Effect of TBT on the vitellogenesis and sex hormonal changes in Macrobrachium rosenbergii has never been reported. Hence, the present investigation was undertaken to find out the impact of TBT on histological changes in the different reproductive tissues, sex hormonal alterations and level of biomarkers like vitellogenin and vitellin in M. rosenbergii. Results The present investigation documents the possible impact of tributyltin (TBT) on the vitellogenesis in freshwater female prawn M. rosenbergii. TBT at 10 ng/l, 100 ng/l and 1000 ng/l concentrations were exposed individually to prawns for a period of three months. At higher concentration of 1000 ng/l, the ovarian development was arrested and ovary remained at spent stage. At lower concentration of TBT (10 ng/l), the development proceeded up to early vitellogenic stage. At intermediate concentration of 100 ng/l TBT, the ovary remained at pre vitellogenic stage and thereafter no development was noticed. Histological results indicated the normal ovarian development with vitellogenic oocytes, filled with yolk globules in control prawn. On the other hand, the TBT treated groups showed reduction in yolk globules, fusion of developing oocytes and abundance of immature oocytes. Immunofluorescence staining denoted the remarkable reduction in vitellin content in ovary of TBT treated prawn. Hence, TBT had conspicuously inhibited the vitellogenesis by causing hormonal imbalance in M. rosenbergii. Conclusion TBT had notably inhibited the vitellogenesis due to hormonal imbalance. This endocrine dysfunction ultimately impaired the oogenesis in the freshwater female prawn M. rosenbergii.

2013-01-01

376

Fire in the Brazilian Amazon  

Microsoft Academic Search

Regenerating forests have become a common land-cover type throughout the Brazilian Amazon. However, the potential for these\\u000a systems to accumulate and store C and nutrients, and the fluxes resulting from them when they are cut, burned, and converted\\u000a back to croplands and pastures have not been well quantified. In this study, we quantified pre- and post-fire pools of biomass,\\u000a C,

R. F. Hughes; J. B. Kauffman; D. L. Cummings

2000-01-01

377

Effects of dietary administration of water hyacinth (Eichhornia crassipes) extracts on the immune responses and disease resistance of giant freshwater prawn, Macrobrachium rosenbergii.  

PubMed

The hot-water extract of Eichhornia crassipes leaves (ECE) was produced and incorporated into the diet of the prawn, Macrobrachium rosenbergii, as an immunostimulant. Survival rates of prawn against Lactococcus garvieae, and its immune parameters including the total haemocyte count (THC), different haemocyte count (DHC), phenoloxidase (PO) activity, respiratory bursts (RBs), superoxide dismutase (SOD) activity, glutathione peroxidase (GPx) activity, transglutaminase (TG) activity, haemolymph coagulation time, and phagocytic activity and clearance efficiency against L. garvieae by M. rosenbergii were determined when prawn (23.0 ± 2.8 g) were fed ECE-containing diets at 0, 1.0, 2.0 and 3.0 g kg(-1). Prawn fed a diet containing ECE at 2.0 and 3.0 g kg(-1) for 12 days showed significantly increased THC, HC, GC, PO activity, RBs, SOD activity, GPx activity, and TG activity, and a significantly decreased coagulation time. The phagocytic activity and clearance efficiency against L. garvieae of prawn fed the ECE-containing diets at 1.0, 2.0, and 3.0 g kg(-1) were significantly higher than those of prawn fed the control diet at 3-12 days. Survival rates of M. rosenbergii fed the diet containing ECE at concentrations of 2 and 3 g kg(-1) were significantly higher than those fed the control diet after challenge with L. garvieae for 48-144 h. The relative percentage survival of prawn fed the 1.0, 2.0, and 3.0 g kg(-1) ECE-containing diets for 12 days were 17.5%, 39.1%, and 52.2%. It was concluded that the ECE can be used as an immunostimulant for prawn through dietary administration to enhance immune responses and resistance of M. rosenbergii against L. garvieae. PMID:23603238

Chang, Chin-Chyuan; Tan, Hui-Ching; Cheng, Winton

2013-07-01

378

Direct use of low temperature geothermal water by Aquafarms International, Inc. for freshwater aquaculture (prawns and associated species). An operations and maintenance manual  

SciTech Connect

In connection with an ongoing commercial aquaculture project in the Coachella Valley, California; a twelve month prawn growout demonstration project was conducted. This project began in August, 1979 and involved the use of low temperature (85/sup 0/F) geothermal waters to raise freshwater prawns, Macrobrachium rosenbergii (deMan), in earthen ponds. The following publication is an operations and maintenance guide which may by useful for those interested in conducting similar enterprises.

Broughton, R.; Price, M.; Price, V.; Grajcer, D.

1984-04-01

379

Greenhouse Gas Evasion from Amazon Reservoirs and Lakes  

NASA Astrophysics Data System (ADS)

Few studies of carbon dioxide or methane evasion from Amazon lakes or reservoirs span a full year and include multiple stations and local meteorological data. Based on measurements in Lake Curuai, a large floodplain lake in the lower Amazon basin, made at 71 to 74 stations during the four hydrological phases of inundation and draining, we illustrate the spatial patterns associated with proximity to the shore and to inflows. Carbon dioxide exchange with the atmosphere was calculated based on three gas exchange models. Values computed using equations based on wind and buoyancy flux averaged 85% higher than those based only on wind. Estimates using a surface renewal model depended upon the mixed layer depth. Carbon dioxide and methane concentrations and evasion to the atmosphere were sampled over a year from multiple stations in Balbina Reservoir and downstream in the Uatuma River. In addition, samples and evasion measurements were made during four periods in the Samuel, Tucurui and Curua-Una reservoirs and downstream rivers. Degassing can be important as water passes through hydroelectric turbines, and we developed a sampler designed to avoid losses during the collections near the depth of the turbines. For depths greater than 20 m, carbon dioxide and methane concentrations in water samples collected with new sampler averaged 34% and 116% higher than those collected with a standard sampler, respectively. Annual greenhouse gas emission from Balbina Reservoir plus downstream evasion, including the carbon dioxide equivalent of methane emissions, was estimated as 3 Tg C per year.

Melack, J. M.; Kemenes, A.; Rudorff, C.; Forsberg, B.; MacIntyre, S.

2011-12-01

380

Effects of hot-water extract of banana (Musa acuminata) fruit's peel on the antibacterial activity, and anti-hypothermal stress, immune responses and disease resistance of the giant freshwater prawn, Macrobrachium rosenbegii.  

PubMed

The hot-extracts isolated from fruit's peel of banana, Musa acuminata, was evaluated on the antibacterial activity to pathogens from aquatic animals, and immunostimulating potential, disease resistance and anti-hypothermal stress in giant freshwater prawn, Macrobrachium rosenbergii through injection administration. The banana peel extract (BPE) showed good activity against 1 Gram-positive and 3 Gram-negative pathogens, including Lactococcus garvieae, Photobacteria damsella, Vibrio alginolyticus and Vibrio parahemolyticus especially in prawn pathogen of L. garvieae strain, which were carried out by a disk diffusion method. Prawn received BPE via injection administration at 1-6 ?g (g prawn)(-1) significantly increased total haemocyte count (THC), hyaline cell (HC), granular cell (GC), phenoloxidase (PO) activity and phagocytic activity against L. garvieae from 3 to 6 days, and significantly increased clearance efficiency against L. garvieae and a significantly decreased coagulation time of prawn from 1 to 6 days. Prawn injected with BPE at 6.0 ?g (g prawn)(-1) for 6 days showed significantly increased superoxide dismutase (SOD) activity, but significantly decreased respiratory bursts (RBs) of per haemocyte. Survival rates of M. rosenbergii injected with BPE at concentrations of 1, 3 and 6 ?g (g prawn)(-1) were significantly higher than those injected with saline control after challenge with L. garvieae for 4-6 days, and the respective relative survival percentages of prawn were 28.6%, 38.1%, and 47.8%, respectively at 6 days. The sublethal time of prawns that had received saline and BPE at 1, 3 and 6 ?g (g prawn)(-1) for 6 days and then were transferred from 28 °C to 14 °C were 69.4, 79.8, 83.6, and 90.2 h, respectively. It was concluded that the BPE can be used as the bacteriostat, and immunostimulant and physiological regulator for prawn through injection administration to enhance immunity, physiological responses, and resistance against L. garvieae. PMID:24906123

Rattanavichai, Wutti; Cheng, Winton

2014-08-01

381

Diatoms from the Colombian and Peruvian Amazon: the Genera Encyonema, Encyonopsis and Gomphonema (Cymbellales: Bacillariophyceae).  

PubMed

The diatom flora of the Colombian and Peruvian Amazon is far less studied than the flora of the Brazilian sector of the basin. Here we present results related to the genera Encyonema, Encyonopsis and Gomphonema. Plankton and periphyton samples were collected in lotic and lentic waterbodies from the Amazonian-Andean region, the Amazon River, Japurá River and Porvenir River basins during 1993, 1994, 2001 and 2003. At each sampling station pH, temperature, water transparency and conductivity were registered. Samples were analyzed with phase contrast microscope (LM) and scanning electron microscope (SEM). Ten taxa are new records for the area; Encyonema for the Peruvian and Colombian Amazon and Encyonopsis for the Colombian Sector. Encyonema neogracile var. tenuipunctatum, E. vulgare, Encyonopsis frequentis, Gomphonema augur var. sphaerophorum and G. contraturris are recorded for the first time in Colombia; Encyonema venezolanum and G. neoapiculatum in Colombia and Peru and the latter also for Amazonia. E. angustecapitatum was mentioned in Colombia before at a pond located at 3000 m asl. We describe a new species from Porvenir River, Amazonas, Colombia: Encyonema amazonianum. PMID:20411706

Vouilloud, Amelia A; Sala, Silvia E; Avellaneda, Marcela Núñez; Duque, Santiago R

2010-03-01

382

A Conceptual model of Ecophysiological Function across the Amazon Basin using a Synthesis of Observed and Model Data  

Microsoft Academic Search

Observations of the seasonal cycle of Net Ecosystem Exchange of Carbon (NEE) are variable across the Amazon Basin. NEE has been observed to be nearly uniform through the year at sites such as Cueiras Reserve in Amazonas. A pattern of efflux during the wet season and uptake during seasonal drought has been observed at multiple sites in the Tapajos River

I. T. Baker; A. S. Denning; A. B. Harper

2008-01-01

383

Palynological evaluation of the Famennian Protosalvinia (Foerstia) Zone in the Amazon Basin, northern Brazil: a preliminary study  

Microsoft Academic Search

Miospore assemblages recovered from a shallow borehole (Caima PH-2) and outcrops near the Tapajós River (Itaituba area), on the southern margin of the Amazon Basin, permit the correlation of the Protosalvinia Zone in this region with the equivalent of the uppermost part of the VCo miospore Zone in the eastern USA. Therefore it is dated as late (not latest) Famennian

Stanislas Loboziak; JoséHenrique G. Melo; Luiz P. Quadros; Maurice Streel

1997-01-01

384

Forecasting terrestrial water storage changes in the Amazon Basin using Atlantic and Pacific sea surface temperatures  

NASA Astrophysics Data System (ADS)

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.

de Linage, C.; Famiglietti, J. S.; Randerson, J. T.

2013-10-01

385

Amazon Rainforest Phenology Observed From Space  

Microsoft Academic Search

The rainforests of the Amazon basin form the largest contiguous, undisturbed forest on our planet, influencing global climate, water, and carbon dynamics, and housing the largest reservoir of biological diversity. Yet Amazon rainforest phenology remains poorly understood due to complex patterns of moisture, sunlight, and biological constraints on productivity. Here we show increases in photosynthetic activity at the start of

A. R. Huete; K. Didan; Y. Shimabukuro; P. Ratana; W. Yang; R. Nemani; R. Myneni

2005-01-01

386

Sediment transport and sedimentation along the Amazon floodplain  

SciTech Connect

As the Amazon River leaves the Andean foothills and crosses the structural trough in its Brazilian segment, it receives a large increment of discharge, but a small increase in sediment load from the bounding cratons. The gradient of the river declines gradually from Iquitos, Peru, downstream to Coari, Brazil, before increasing downstream to the vicinity of Manaus as the river crosses a structural arch. Between Manaus and Obidos, the river slope declines sharply. The interplay of the variable gradient and increasing discharge creates a pattern of boundary shear stress and sediment transport which the authors have defined by measurement and calculation. The downstream divergence of suspended and bed load transport is responsible for the patterns of aggradation, channel behavior and floodplain morphology. Aggradation has been computed on the basis of three years of sediment transport measurements; floodplain morphology was documented from radar photography and navigation charts; and channel migration from these charts and from aerial and satellite photography. In the reach between the Peruvian border and Coari, the river deposits sand bars within and alongside the channel and shifts laterally at a relatively rapid rate, forming a scroll-bar floodplain topography with long, narrow lakes. In the middle, steeper reach no net aggradation was measured, sand-bar development and channel shifting are limited. Below Manaus, the rapid decline in gradient and the large influx of Andean sediment from the Rio Madeira result in deposition of almost the entire sand load and a portion of the silt.

Dunne, T.; Mertes, A.K.L.; Meade, R.H.

1985-01-01

387

Use of ethanol production by-products for producing microalgae, tilapia, and freshwater prawns  

SciTech Connect

By-products from fermentation of grains to alcohol are highly valued as feed supplements for beef and dairy cattle, swine, and poultry. The quantity of wet distillers by-products (stillage) from fuel alcohol production is expected to increase greatly. Unlike dried distillers by-products, wet distillers by-products have generally been abandoned as feed supplements for livestock because of high water content, cost of handling, and storage problems. Using wet distillers by-products as a fertilizer or feed supplement in aquatic production systems appears promising. Two experiments were conducted to determine relationships between stillage application rates and production of microalgae and yields of tilapia (fish) and freshwater prawns (shrimp). Dissolved oxygen concentrations and several other water quality parameters were also monitored. 19 refs., 3 figs., 17 tabs.

Behrends, L.L.; Kingsley, J.B.; Price, A.H. III

1983-01-01

388

Phospholipid fatty acid composition of hepatopancreatic brush-border membrane vesicles from the prawn Penaeus japonicus.  

PubMed

Brush-border membrane vesicles (BBMV) were isolated from prawn hepatopancreas as we previously described (Muriana et al (1993) J Biochem 113, 625-629). The characterization of hepatopancreatic BBMV (hBBMV) by monitoring the activity of marker enzymes indicated a relatively pure apical membrane preparation reduced in basolateral contamination. Phospholipid composition of hBBMV was examined by the Iatroscan TLC/FID technique, whereas the fatty acid profile of phospholipids was examined by capillary gas chromatography. Phosphatidylcholine and phosphatidylethanolamine are the principal phospholipids of these membranes. The major fatty acids of phospholipids are palmitic (16:0), palmitoleic (16:1n-7), stearic (18:0), oleic (18:1n-9), eicosapentaenoic (20:5n-3) and docosapentaenoic (22:5n-3) acids. Individual phospholipids are characterized by distinct fatty acid compositions, but display a similar ratio of unsaturated-to-saturated fatty acids and a similar unsaturation index. PMID:7647111

Muriana, F J; Ruiz-Gutierrez, V; Blaya, J A; Bolufer, J

1995-01-01

389

Gamma irradiation-aided chitin/chitosan extraction from prawn shells  

NASA Astrophysics Data System (ADS)

Chitin and chitosan were extracted from prawn shells. The influence of a 25 kGy irradiation dose on the deproteination process was investigated. The deproteination degree was followed by Lowry-Folin method. The demineralisation degree versus reaction time with 1 N hydrochloric acid solution was followed by atomic absorption spectrometry. Chitin and chitosan obtained were characterised by FTIR spectrometry. The influence of some parameters, such as reaction time, alkaline concentration and temperature on the deacetylation degree was also investigated. The deacetylation degree was evaluated by FTIR spectrometry using the bands at 1320 cm -1 and 1420 cm -1. It was found that the irradiation of the shells at a dose of 25 kGy reduces the time of the deproteination reaction by a factor of three, comparatively to the non-irradiated samples.

Mahlous, M.; Tahtat, D.; Benamer, S.; Nacer Khodja, A.

2007-12-01

390

Follow-up of mercury levels in fish, human hair and urine in the Madeira and Tapajós basins, Amazon, Brazil  

Microsoft Academic Search

Informal economy of gold mining has contaminated some important river basins in Amazon. Follow-up studies on critical compartments\\u000a showed some areas with high Hg levels in fish as well as in human hair samples. Average Hg in piscivorous fish in the Madeira\\u000a river itself was 846 ppb (N=284) with a maximum of 3921 ppb. Mercury in fish from non polluted

O. Malm; J. R. D. Guimarães; M. B. Castro; W. R. Bastos; J. P. Viana; F. J. P. Branches; E. G. Silveira; W. C. Pfeiffer

1997-01-01

391

Molecular cloning of Clock cDNA from the prawn, Macrobrachium rosenbergii.  

PubMed

CLOCK, which belongs to the basic helix-loop-helix (bHLH)/PER-ARNT-SIM (PAS) superfamily of transcription factors, is one of the most essential proteins involved in circadian systems of animals. Clock genes have been cloned from several species, including mammals, insects, birds, fish, and amphibians. In the present study, we successfully isolated a Clock homolog (termed Mar-Clock) from the giant prawn, Macrobrachium rosenbergii. The 2949-bp cDNA contained a 2115 bp open reading frame that encoded a putative CLOCK protein of 704 amino acids (termed Mar-CLOCK) exhibiting high identities with CLOCK homologs in other species (30-35%). This is the first report of a circadian clock gene from crustaceans. Mar-CLOCK possessed an exceptionally long glutamine-rich domain (140 amino acids) in its C-terminus, which usually ranges from 14 to 57 amino acids in other known CLOCKs and is supposed to function in transcriptional activation. Using RT-PCR, we observed that Mar-Clock was expressed in all tested tissues. Semiquantitative RT-PCR was performed to investigate the gene expression profile during the light-dark cycle. The results indicated that the expression of the Mar-Clock gene had no significant rhythmicity in central nervous tissues (thoracic ganglia and eyestalk) or peripheral tissues (gill, ovary, hepatopancreas, and muscle). Furthermore, gene expression tended to increase in the central nervous system (brain, thoracic, and abdominal ganglia) of eyestalk-ablated or constant dark (DD) prawns, and in the eyestalk-ablated gill. No expression change was found under constant light (LL) or in heart and muscle. PMID:16271708

Yang, Jin-Shu; Dai, Zhong-Min; Yang, Fan; Yang, Wei-Jun

2006-01-01

392

Post-Embryonic Transcriptomes of the Prawn Macrobrachium rosenbergii: Multigenic Succession through Metamorphosis  

PubMed Central

Like many metazoans, the freshwater prawn Macrobrachium rosenbergii begins its post-embryonic life with a set of morphologically distinct planktonic larval stages, followed by a benthic post-larval stage during which the maturing organism differs from the larvae both ecologically and physiologically. Understanding of the molecular basis underlying morphogenesis in crustaceans is limited to the observation that methyl farnesoate, the non-epoxidated form of the insect juvenile hormone, acts as the active crustacean juvenoid. Molt steroids were also linked to morphogenesis and several other molecular pathways, such as Hedgehog and Wnt, are known to underlie morphogenesis in all metazoans examined and, as such, are thought to do the same in crustaceans. Using next generation sequencing, we deep-sequenced the transcriptomes of several larval and post-larval stages. De novo assembly, followed by bioinformatics analysis, revealed that many novel transcripts are over-expressed in either larvae- or post-larvae-stage prawn, shedding light on the molecular basis underlying M. rosenbergii metamorphosis. Fast larval molting rates and periodic morphological changes were reflected in over-expression of transcripts annotated to the cell cycle, DNA replication and morphogenic pathways (i.e., Hedgehog and Wnt). Further characterization of transcripts assigned to morphogenic pathways by real-time RT-PCR reconfirmed their over-expression in larvae, albeit with a more complex expression pattern when examined in the individual developmental stages. The expression level of an orthologue of cytochrome P450, 15A1, known to epoxidize methyl farnesoate in insects, was increased in the late larval and early post-larval stages, in accordance with the role of methyl farnesoate in crustacean metamorphosis. This study exemplifies the applicability of a high-throughput sequencing approach for studying complex traits, including metamorphosis, providing new insight into this unexplored area of crustacean research.

Ventura, Tomer; Manor, Rivka; Aflalo, Eliahu D.; Chalifa-Caspi, Vered; Weil, Simy; Sharabi, Omri; Sagi, Amir

2013-01-01

393

Transcriptomics of a Giant Freshwater Prawn (Macrobrachium rosenbergii): De Novo Assembly, Annotation and Marker Discovery  

PubMed Central

Background Giant freshwater prawn (Macrobrachium rosenbergii or GFP), is the most economically important freshwater crustacean species. However, as little is known about its genome, 454 pyrosequencing of cDNA was undertaken to characterise its transcriptome and identify genes important for growth. Methodology and Principal Findings A collection of 787,731 sequence reads (244.37 Mb) obtained from 454 pyrosequencing analysis of cDNA prepared from muscle, ovary and testis tissues taken from 18 adult prawns was assembled into 123,534 expressed sequence tags (ESTs). Of these, 46% of the 8,411 contigs and 19% of 115,123 singletons possessed high similarity to sequences in the GenBank non-redundant database, with most significant (E value < 1e–5) contig (80%) and singleton (84%) matches occurring with crustacean and insect sequences. KEGG analysis of the contig open reading frames identified putative members of several biological pathways potentially important for growth. The top InterProScan domains detected included RNA recognition motifs, serine/threonine-protein kinase-like domains, actin-like families, and zinc finger domains. Transcripts derived from genes such as actin, myosin heavy and light chain, tropomyosin and troponin with fundamental roles in muscle development and construction were abundant. Amongst the contigs, 834 single nucleotide polymorphisms, 1198 indels and 658 simple sequence repeats motifs were also identified. Conclusions The M. rosenbergii transcriptome data reported here should provide an invaluable resource for improving our understanding of this species' genome structure and biology. The data will also instruct future functional studies to manipulate or select for genes influencing growth that should find practical applications in aquaculture breeding programs.

Jung, Hyungtaek; Lyons, Russell E.; Dinh, Hung; Hurwood, David A.; McWilliam, Sean; Mather, Peter B.

2011-01-01

394

Methylmercury in a predatory fish ( Cichla spp.) inhabiting the Brazilian Amazon  

Microsoft Academic Search

This research tested whether limnological conditions, biological characteristics of fish and anthropogenic impacts influenced the assimilation of methylmercury into the muscle of a sedentary piscivorous fish, Cichla spp., from three rivers (Negro, Madeira, Tapajós) and two hydroelectric reservoirs (Balbina, Tucuruí) within the Brazilian Amazon. Methylmercury in this fish ranged from 0.04 to 1.43?gg?1 w.w. across sites. No significant differences were

Helena do A. Kehrig; Bruce M. Howard; Olaf Malm

2008-01-01

395

Recent advances in wavelet analyses: Part 2—Amazon, Parana, Orinoco and Congo discharges time scale variability  

Microsoft Academic Search

This paper is devoted to illustrating new wavelet analysis methods in the field of hydrology. New wavelet indicators are applied to long-term hydrological and climatologic proxies. They are first applied to four Atlantic large river monthly discharges (Amazon, Parana, Orinoco and Congo) and then applied to two well-known long-term climatologic indexes: the Southern Oscillation and the North Atlantic Oscillation. This

David Labat; Josyane Ronchail; Jean Loup Guyot

2005-01-01

396

An atypical microfilaria in blood samples from inhabitants of Brazilian Amazon  

Microsoft Academic Search

An unindentified microfilaria sharing characteristics with Mansonella ozzardi and Onchocerca volvulus was detected in blood samples from seven human volunteers, inhabitants of a community in the border of Amazonas and Acre\\u000a State. They were detected during epidemiological studies carried out in some communities along Antimary, Acre, and Purus Rivers\\u000a in the Brazilian Amazon. The most striking difference was presented in

Y. L. Adami; M. A. P. Moraes; R. M. Lanfredi; M. Maia-Herzog

2008-01-01

397

Seasonal dynamics and Organic Carbon Flux in the Congo River  

Microsoft Academic Search

The Congo (Zaire) River, the second world river in terms of discharges and drainage area (Q=40600 m3\\/s; A=3.5 106 km2) after the Amazon River, is -up to now- in near-pristine state. For up to two years , the mainstream near river mouth (Kinshasa\\/Brazzaville station) and some major and minor tributaries (Oubangui, Mpoko and Ngoko-Sangha) were surveyed every month, for total

P. Seyler; A. Coynel; H. Etcheber; M. Meybeck

2006-01-01

398

Assessing the Amazon Basin Circulation with Stable Water Isotopes  

NASA Astrophysics Data System (ADS)

The isotopic abundances of Oxygen-18 (? 18O) and Deuterium (? D) over the Amazon are used to constrain simulations of the water cycle in this, the largest river basin in the world. Tracking the two stable but rare isotopes of water (1HD16O and 1H218O) makes it possible to trace Amazonian regional evaporative and condensation processes. This offers isotopic constraints on regional to global-scale atmospheric moisture budgets. Based on data in the Global Network on Isotopes in Precipitation (GNIP) database, we analyse the simulation of the land surface hydrology and water cycling. Temporal changes between 1965 and 2000 in stable water isotopic signatures in the Amazon have been used to evaluate global climate model (GCM) predictions revealing notable anomalies. For example, the differences in the wet season deuterium excess between Belem and Manaus are consistent with recent GCM simulations only if there has been a relative increase in evaporation from non-fractionating water sources over this period. Despite earlier predictions that land-use change signals would be found, late twentieth century data reveal no significant change in dry season isotopic characteristics. On the other hand, more recent isotopic data do show trends at stations in the Andes, where as much as 88% of the rainfall is thought to be derived from recycled moisture. At Izobamba the wet season depletions are enhanced (greater depletion) and the dry season ones decreased (less depletion). At Bogota only the wet months show statistically significant changes - also an enhancement. More depletion in the wet months is consistent with reductions in non-fractioning recycling such as through transpiration and in full re-evaporation of canopy-intercepted rainfall. These data might be linked to deforestation impacts. Results of GCM and simpler model simulations of the Amazon suggest that the recent stable isotope record is consistent with the predicted effects of forest removal, perhaps combined with greenhouse warming. At a minimum, large-scale simulations of South American climate ought to be tested against these isotopic data in any validation effort. Specific caveats our conclusions include: (i)monthly isotope data only are available in GNIP and hence analysed; (ii) the statistically significant seasonal changes reported might be related to, or even exaggerated by, El Niño-Southern Oscillation (ENSO) events or other climatic variations that modify the Walker circulation and Inter-Tropical Convergence Zone (ITCZ) position and hence affect the moisture climatology of the Amazon; (iii)no information on fluxes from simulated open water as a surface type in the Amazon GCM experiments has been considered; (iv)the selected models are failing to correctly simulate the relative components of transpiration and re-evaporated canopy interception in the Amazon dry season; and (v) no isotope tracking in the Amazon deforestation simulations was reviewed, because none is yet available. These shortcomings deserve further work.

McGuffie, K.; Henderson-Sellers, A.

2004-05-01

399

Amazon deforestation and climate change  

SciTech Connect

A coupled numerical model of the global atmosphere and biosphere has been used to assess the effects of Amazon deforestation on the regional and global climate. When the tropical forests in the model were replaced by degraded grass (pasture), there was a significant increase in surface temperature and a decrease in evapotranspiration and precipitation over Amazonia. In the simulation, the length of the dry season also increased; such an increase could make reestablishment of the tropical forests after massive deforestation particularly difficult. 31 refs., 3 figs., 2 tabs.

Shukla, J.; Nobre, C.; Sellers, P. (Univ. of Maryland, College Park (USA))

1990-03-16

400

Effects of an organophosphorus insecticide, trichlorfon, on hematological parameters of the giant freshwater prawn, Macrobrachium rosenbergii (de Man)  

Microsoft Academic Search

Hemolymph osmolality, ion concentration, acid–base balance, and immune parameters in Macrobrachium rosenbergii (15–20 g) were measured after 8 days of exposure to 0–0.3 mg l?1 trichlorfon. A significant depression in hemolymph osmolality and Cl?1 contents were observed with exposure to 0.3 mg l?1 trichlorfon. Similarly, hemolymph pH, HCO3?, and TCO2 decreased significantly when prawns were exposed to concentration of greater

Shinn-Pyng Yeh; Tzeng-Gan Sung; Chin-Chyuan Chang; Winton Cheng; Ching-Ming Kuo

2005-01-01

401

Prophenoloxidase activating enzyme-III from giant freshwater prawn Macrobrachium rosenbergii : characterization, expression and specific enzyme activity  

Microsoft Academic Search

The prophenoloxidase activating system is an important innate immune response against microbial infections in invertebrates.\\u000a The major enzyme, phenoloxidase, is synthesized as an inactive precursor and its activation to an active enzyme is mediated\\u000a by a cascade of clip domain serine protei