andean influences on the biogeochemistry and ecology of the amazon river 2008

7232019 Andean Influences on the Biogeochemistry and Ecology of the Amazon River 2008

httpslidepdfcomreaderfullandean-influences-on-the-biogeochemistry-and-ecology-of-the-amazon-river-2008 114

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The Amazon River exits the Andes mountains more

than 4000 kilometers (km) from its estuary but along itsessentially flat and serpentine path through the lowlands of northern Brazil it maintains the character of an Andean river(figure 1) The indelible imprint of this distant mountain rangeon the main-stem channel of the worldrsquos largest river has beennoted by naturalists and researchers for more than a centurybut the multifaceted nature of Andean influences on the hy-drology biogeochemistry and ecology of theriver system haveonly come to light during the past two decades Other fun-

damental but still obscure linkages remain to be discoveredLong before scientists took interest in the study of Ama-

zon environmentsmdashin fact long before Europeans ldquodiscov-eredrdquo the rivermdashnative peoples of the lowland Amazonrecognized the unique characteristics of Andean tributariesAgriculture thrived on the fertile floodplains of these muddy rivers and gaverise to some of the regionrsquos first and most suc-cessful chiefdoms (Meggars 1984) Native Amazonians alsocapitalized on the rich fish stocks of Andean tributariesAlfred Russel Wallace (1853) was perhaps the first naturalistto write about the white-waterclear-water and black-water

river types of the Amazon basin and to relate the color of tributaries to the nature of their drainage basins (figure 2)Wallace astutely linked the sediment load of white-watertributaries to erosion in their steep Andean headwaters andidentified clear-water rivers with the crystalline ldquomountains

of Brazilrdquo (the Guyana and Brazilian shields) He knew thatblack-water rivers emerged from lowland sources and hecorrectly attributed their darkcoloring to leaching of ldquodecayingleaves roots and other vegetable matterrdquo (Wallace 1853)Another naturalist of that timeHenry Bates (1863) marveledat the transport of volcanic pumice in the main-stem Ama-zon River and correctly assigned its origin to volcanic rangesthousands of kilometers away in the Ecuadorian Andes Heimagined these porous stones as vehicles transporting seedsand insect eggsdownstreamandthereby dispersing organisms

far beyond their original ranges Over the last 50 yearssystematic investigations have further advanced scientistsrsquounderstanding of the environment and distinct aquatic eco-systems of the lowland Amazon River (summarized in Sioli[1984] Junk [1997] and McClain et al [2001])

Steep terrain and young lithologies make the Andes animportant source of sediments and solutes to the lowerreaches of theAmazon River The most visible characteristicsof the main-stem Amazon and its Andean tributaries arehigh discharge and heavy loads of suspended and bedload

Michael E McClain (e-mail mcclainmfiuedu) is with the Department of Environmental Studies at Florida International University in Miami and

Robert J Naiman (e-mail naimanuwashingtonedu) is with the School of

Aquatic andFishery Sciences at theUniversity of Washington in Seattle copy 2008

American Institute of Biological Sciences

Andean Influences on the

Biogeochemistry and Ecology

of the Amazon River

MICHAEL E MCCLAIN AND ROBERT J NAIMAN

Although mountains often constitute only a small fraction of river basin area they can supply the bulk of transported materials and exert strong regulatory controls on the ecological characteristics of river reaches and floodplains downstream The Amazon River exemplifies this phenomenonIts muddy waters and its expansive and highly productive white-water floodplains are largely the products of forces originating in distant Andean mountain ranges The Amazonrsquos character has been shaped by these influences for more than 10 million years and its present form and host of diverse organisms are adapted to the annual and interannual cycles of Andean inputs Although the Andes constitute only 13 of the Amazon River basin they are the predominant source of sediments and mineral nutrients to the riverrsquos main stem and Andean tributaries form productive corridors extending across the vast Amazonian lowlands Many of the Amazonrsquos most important fish species rely on the productivity of Andean tributaries and main-stem floodplains and annual fish migrations distribute Andean-dependent energy and nutrient resources to adjacent lower- productivity aquatic systems Mountain-lowland linkages are threatened however by expanding human activities in the Andean Amazon with consequences that are eventually felt thousands of kilometers away

Keywords Amazon Andes nutrient subsidies land use fisheries

wwwbiosciencemagorg April 2008 Vol 58 No 4 bull BioScience 325





lowland tributary inputs (Devol and Hedges 2001)Even though we are beginning to understand thedynamics of Andean-derived materials in themain-stem Amazon River corridor and the degree towhich lowland ecosystems depend on upstreaminputs we still know little about the nature andvariability of processes that mobilize these materi-als from the Andes and modify them during down-stream transport and storage in the extensivefloodplains

In this article we briefly introduce the geo-morphology and ecological zones of Andean head-water regions of the Amazon as these are poorly known even among scientists specializing in Ama-zon ecology We then examine the multifacetedways in which the main-stem Amazon River isinfluenced bymdashand depends onmdashAndean inputsWe conclude by exploring frontiers in research link-ingAndean and lowland parts of theAmazon con-sidering the possible impacts of increasinghuman-related development and climate change inthe Andean Amazon

The Andean AmazonTheAndes mountains rise steeply alongthe westernmargin of theAmazon basin and stand3000 metersabove sea level (masl) in elevation over much of their length(figure 1)Approximately half of theAn-dean Amazon lies at elevations between 500 and

2000 masl while most of the remainder is between2000 and 4000 masl about 16 is above 4000 masl(table 1)The highest point in the Amazon basin isthe Nevado de Huascaran in the Cordillera Blancaof Peru at 6768 maslbut several otherpeaks extendabove 6000 masl Active volcanoes are prominentfeatures of theEcuadorian andBolivian Andes Theeastern cordillera of theAltiplanoa high-elevationendorheic basin containing Lake Titicacaforms onone of the widest sections of the Andes spanningnearly 300 km near the lake

Characterization of the precipitation soils andvegetation of theAndeanAmazon is fundamental tounderstanding Andean influences on the lowerAmazon River (figure 3)Precipitation is greatest onthe lower and mid slopes of the cordillera (500 to3000 masl) because of orographic controls on airmasses coming from the east The wettest parts of the basin lie in the eastern cordillera of Colombiaand near the PerundashBolivia border where annual

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Figure 2 The main rivers of the Amazon have long been classified according to the color of their waters which also reflects

their source (a) The Iccedila (Putumayo) River is a characteristic white-water river colored by the high loads of sediments transported from the Andes (b) The Negro River is the largest of the black-water rivers tinted by high levels of dissolved organic matter leached from low-lying areas of sandy soils (c) The Rio Tapajos is the most notable of the clear-water rivers carrying low levels of sediments and organic matter from the crystalline Guyana and Brazilian shields Photographs Margi Moss ( httpbrasildasaguascombr)



precipitation may exceed 4 meters (figure 3a) The mostabundant soil order in the Andean Amazon is inceptisol(61) a young mineral-rich soil that occurs at midelevationsMore developed but less fertile ultisols occupy 16 of there-gion and occur mostly at lower elevations in Peru Mollisolsor grassland soils are the third most abundant soil order cov-ering 6 of the region primarily near the PerundashEcuadorborder and at higher elevations in southernPeru Exposed rock is common at very high elevations (greater than 4000 masl)in southern Peru

The major vegetative cover types in the Andean Ama-zonmdashmapped using Advanced Very High Resolution Ra-diometersatellite imagery (Eva et al1998)mdashare submontane(700 to 2000 masl) and montane (2000 to 3700 masl) forestswhich together constitute approximately 42 of the region(figure 3b table 2) Montane herbaceous vegetation inter-spersed withshrubland andagriculture is also widespreadcov-ering nearly a quarter of the region As of 2000 at least 40of the region had been converted to human uses or frag-mented by these uses (JRC 2000) The most intense humanalteration has historically been at high elevations (gt 3000masl) where high levels of alteration continue today butchange is increasingly concentrated at mid and lower eleva-tions as colonization continues and roads spread across theregion (Mena et al 2006)

The modern Amazon River is born in numerous Andeansprings but cartographers locate the most distant source of the river at 5300 masl on the northern slope of NevadoMismiFrom this stream the Carhuasanta the main stem of the Amazon changes names at least nine times from Car-huasanta to Lloqueta Hornillos Apurimac Ene TamboUcayaliAmazonas Solimotildees and finally Amazon below theconfluence of the Solimotildees and Negro rivers The entirenorth-south length of the Andean Amazon basin is drained

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328 BioScience bull April 2008 Vol 58 No 4 wwwbiosciencemagorg

Table 1 Elevation ranges of the Andean Amazon

Elevation (meters Area Areaabove sea level) (square kilometers) (percentage)

500ndash1000 111804 18

1001ndash2000 170514 27

2001ndash3000 117018 19

3001ndash4000 120671 194001ndash5000 100766 16

gt 5000 2444 lt 1

Total 623217 100

Source Compiled from Shuttle Radar Topography Mission90-meter data

Figure 3 (a) Areas of higher precipitation are focused on the lower slopes of the Andes with maximal registered precipitation in the headwaters of the Madre de Dios River in southwest Peru and the Napo River of central Ecuador (b) Montane forests dominate the land cover between 500 and 3000 meters above sea level and transition into natural high-elevation grasslands above Compiled from Shuttle Radar Topography Mission 90-meter data and Global Land Cover 2000 data (CJRC 2000)



by eight major riversmdashthe Caquetaacute Putumayo NapoMarantildeonUcayali Madre de DiosBeni and Mamoreacute (figure1)

Andean influences on the loadof the Amazon main stemThe main-stem Amazon River integrates the flow of sub-basins containing distinct combinations of geology soilsand vegetation There are four major Andean tributaries tothe main-stem Amazon River the Solimotildees IccedilaJapuraacuteand Madeira (figure 1) (Andean tributaries

to the main stem are defined as those with head-waters above 500 masl in the Andes mountainsas-suming that the western limit of the main-stemAmazon River is setas theBrazilndashColombia border)Where they intersect with the main stem the com-bined mean annual flow of these white-water trib-utaries is approximately 90000 cubic meters persecond roughly half of the main-stem AmazonRiverrsquos mean annual discharge or five times theflow of the Mississippi River (Dunne et al 1998)

TheAndes cover only about 13 of theAmazon

basin upstream of Oacutebidos and Andean tributariesmay flow through hundreds to thousands of kilo-meters of lowlands (below 500 masl) before con-necting withthemain stemYet most measurementsof ldquoAndeanrdquo contributions to the main-stemAma-zon have been made at the main-stem confluencesof the four Andean tributaries Clearly these rivershave accumulated water particulates and solutesfrom the lowlands before reaching the main stemand therefore one must be careful to consider whatpart of these loads actually derived from the Andes

rather than from the lowlands In the case of waterwenoted thatthe combined flow of the Andeantrib-utaries amounts to approximately half of main-stem flow but the volume of water actually originating in the Andes is probably roughly pro-

portional to the areal coverage of the Andes Although annualprecipitation on the lower slopes of the Andes exceeds theAmazon average higher valleys of the Andes are more aridand thus the average precipitation for the entire range is notlikely to be greatly different from precipitation for the basinas a whole But while Andean contributions of water to themain-stem Amazon may be proportional to area contri-butions of sediments and solutes are disproportionately greater Moreover energy and nutrients carried from theAndes by the river appear to largely drive main-stem pro-ductivity both directly and indirectly through biophysicalfeedbacks with the massive lowland floodplain

Inorganic sediments and solutesFour decades ago Ronald J Gibbs wrote that ldquothe Andeanmountainous environment controls the geochemistry of theAmazon Riverrdquo (Gibbs 1967) He had sampled the Amazonmain stem and 16 of its major tributaries and had comparedtotal particulate and solute concentration data for the wet anddry seasons against nine environmental parameters On thebasis of strong correlations with the environmental param-eter ldquomean reliefrdquo Gibbs concluded that the Andes were thesource of 82 of the total suspended solids exported by theAmazon River The importance of Andean sources of sus-pended sediment to the main-stem Amazon River was re-affirmed bythe subsequent work of Robert Meade and otherswho concluded that between 90 and 95 of thesuspended

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Table 2 Land cover of the Andean Amazon basin

Area AreaLand-cover class (square kilometers) (percentage)

Forest (includes areas 329574 53of fragmented forest)

Grassland and shrubland 215755 34(includes pasture)

Wetland 231 lt 1

Cropland 71216 11

Dryland 6375 1

Water 1832 lt 1

Ice 1031 lt 1

Urban 394 lt 1

Totals 626408 100

Note The difference in the total area reported in tables 1 and 2 isdue to grid size differences of the initial raster data sets

Source Compiled from Global Land Cover 2000 data (JRC 2000)

Figure 4 The disproportionate loads of sediments carried by the main Andean tributaries are evident when comparing the inflows of (a) water and (b) sediments to the main-stem Amazon river from its major tributaries Inputs at the top of each diagram represent the contributions of the AmazonasSolimotildees River flowing from Peru Data were compiled by R H Meade from water-discharge data listed by Carvalho and da Cunha (1998) and from the sediment-discharge data of Dunne and colleagues (1998)



sediment load of the main stem derived from the Andean trib-utaries (figure 4 Meade 1984 Meade et al 1985)

Returning to the question of how much of the water andsuspended particles carried by the Amazon River originatefrom the Andes mountains we speculated that less than aquarter of the water originates in the Andes but that mostsuspended sediments could originate in mountain areasLoads of suspended and bed sediments measured along theentire lengthof the Madeira River from itsAndean headwatersto its confluence with the main stem show a sharp decreasein sediment load (as much as 60) at the base of the Andesa decrease in the mean diameter of suspended particles in thepiedmont region and a progressive decrease in the meandiameter of bed sediments (Guyot et al1999)mdashall indicatorsof a declining energetic capacity to transport materialsThesecharacteristics indicate that Andean rivers supply more thanenough sediment to account for the total load of sedimentsin the lowland sections of theAndean tributariesConclusiveevidence of an Andean source is found in the mineralogicaland isotopic composition of the suspended sediments Themineral composition of sediments in the main-stemAmazoncorrelates well with that of the Ucayali and Marantildeon riversin the Andes (Gibbs 1967) Measurements of neodymiumstrontium and lead isotopic ratios reaffirm that Andeansources account for an overwhelming proportion of themain-stem sediment load (Allegre et al 1996)

Andean-derived suspended sediments bring a large flux of minerals into the main-stemAmazon River butthey also bringother elements and materials Andean tributaries deliver an

order of magnitude more particulate nitrogen (1170 mega-grams [Mg] per year) and phosphorus (806 Mg per year) tothe main stem than their lowland counterparts (119 and 43Mg peryear respectivelyRicheyand Victoria 1993)Most par-ticulate nitrogen is likely to be organic whereas phosphorusis mainly phosphate strongly adsorbed to iron and aluminumoxide surfaces (Berner and Rao 1994) The availability of this phosphorus to main-stem organisms is not known butsignificant amounts of phosphorus are released from Ama-zon sediments upon entering the estuary and may be avail-able to organisms on the floodplains (Melack and Forsberg

2001) The question of whether particulate nitrogen andphosphorus actually derive from the Andes or from someintermediate river section is tied to theorigin of thefractionswith which they are associated The tendency of phosphatetoadsorb to mineral surfaces links this nutrient to the Andeansources of the mineral sediment but the organic associationof nitrogen is tied to that of the particulate organic fractionwhich is less well understood

Two features of the Andes enhance their importance tothe solute geochemistry of the Amazon River and to its eco-logical characteristics First the Andes contain the only sig-

nificant deposits of evaporites and carbonates in theAmazonbasin (Stallard and Edmond 1983)High fluxes of Ca2+ (cal-cium) Mg2+ (magnesium)HCO3

ndash (bicarbonate) and SO42ndash

(sulfate) ions occur in rivers draining carbonate depositsand high fluxes of Na+ (sodium) and Clndash (chloride) ions

occur in rivers draining evaporite deposits Rivers drainingbasins containing carbonates generally have total cationcharges of 450 to 3000 microequivalents (microeq) per liter (L)and rivers draining basins containing evaporites may havetotal cation charges of greater than 70000 microeq per L near thesalt sources (Stallard and Edmond 1983) The rich mineralcontent of Andean tributaries underpins the ecologicalproductivity of downstream reachesBlack-water and clear-water tributaries draining lowland portions of the basin by contrast have total cation charges below 300 microeq per L andare characteristically considered to have low ecosystem-scaleproductivity The second distinguishing feature of theAndesis the intensity of its weathering regime which increases theconcentration of ions in solution Among the Amazon trib-utaries that drain basins dominated by less-weatherablesilicate rocks Andean rivers have consistently higher totalcation concentrations (Stallard and Edmond 1983)

Few data exist that would allow us to estimate the pro-portional contribution of major ion fluxes to the main stemfrom the Andes Robert Stallardrsquos work demonstrates thatsolute concentrations are elevatedin Andean riversbutwith-out measurements of discharge it is not possible to calculatefluxes Furthermore one-time flux measurements are notrepresentative of annual or interannual contributions to themain stem Unfortunately no suitable data exist for Colom-bian Ecuadorian or Peruvian Andean tributaries and thusno estimation can be made regarding the Andean contribu-tion of major ions to flow in the Solimotildees River from thesecountriesWe may speculatehowever on thebasis of the high

ion concentrations in Andean rivers that the Andean con-tribution to the main-stemsolute loadis dominantespecially for certain elements found preferentially in Andean litholo-gies For the headwaters of the Madeira River in BoliviaAn-dean fluxes can be estimated with some confidence thanksto a 10-year data set (Guyot et al 1992) Over the period of these data the specific flux of total dissolved solids from An-deanbasinswas 80 Mgper km2 per year while thespecific flux from lowland Bolivian basins was 7 Mg per km2 per year Theheadwaters of the Madeira River contain few carbonate andevaporite deposits in comparison with the headwaters of the

Solimotildees River in PeruThus it is likely that the Peruvian An-descontribute an even larger percentage of the major ions de-livered to the main stem

Organic matter Andean-derived suspended sediments carry a significantamount of organic matter 90 of which is made up of par-ticles less than 63 micrometers (microm) in diameter (Richey etal 1990) Variations in the fluxes of fine particulate organiccarbon (FPOC particles lt 63 microm) along the main stem cor-relate closely with variations in suspended sediment fluxes

suggesting a close physical association In fact the vast majority of FPOC (gt 90) cannot be physically separated frommineral material and is therefore probably physically boundto it (Keil et al 1997) This physical association has beenshown to reduce therate of organic matter decomposition and

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enhance its preservation Total organic carbon is approximately 1 by mass of suspended sediment in the main stem con-stituting a flux of 5 to 14 teragrams (Tg) of carbon per yearto the Atlantic Ocean (Richey et al 1990)

Measurements show that more than 90 of particulateor-ganic carbon (POC gt 05 microm) in the main-stem AmazonRiver comes fromAndean tributaries buthow much actually originates in the Andes Mountains POC behaves moreor lessconservatively in the main stem suggesting that it resistsdecay and is derived from distant sources (Richey et al 1990)Just how refractory and how distant the sources are can be es-timated from a suite of molecular elementaland isotopictech-niques used to characterize the organic matter and to trace itback to its sources (Hedges et al 1986 2000 Aufdenkampeet al 2007) Concentrations of total lignin-derived phenolscarbon-to-nitrogen ratios and stable carbon isotope ratiospoint to terrestrial plants and more specifically the leaves of terrestrial plants as the main source of main-stem organicmatterAlgae and aquatic plants so abundant on the exten-sive Amazonian floodplain are important sources of labileorganic matter fueling microbial metabolism in the mainstem but do not persist in the system (Richey et al 1990)Thedepletion of carbohydrates and the increasing abundancesof nonprotein amino acids and diagnostic lignin-derivedphenols confirm that the organic matter is highly degradedespecially the FPOC fraction Moreover these characteristicsignatures extendup theMadeira andSolimotildees riversand intothe Andean foothills (Hedges et al 2000 Aufdenkampe etal 2007) Richey and colleagues (2002) estimated that the

main-stem Amazon River transports only 7 of the organicmatter supplied to the river basinwide supporting the find-ing that it also transports the most degraded and recalcitrantmaterials

The isotopic data however provide the most definitiveinformation on theageandgeneral source area of particulateorganic matter in the main stem and its Andean tributariesFor main-stem FPOC to have a true Andean source much of it would have to be hundreds to thousands of years old Thisis because little main-stem FPOC (and little of the fine sed-iment with which it is associated) is transported directly

from the Andes most is stored for varying periods of time inpoint-bar and floodplain sediments (Dunne et al 1998)FPOC does in fact have the lowest levels of bomb carbon-14 (14C) of any organic matter fraction in the main-stemAmazon (+19 ∆14C per thousand [permil]) suggesting an aver-age turnover time of hundreds of years (Hedges et al 1986)Allowing for the dilution of the bomb 14C signal by youngerorganic matter this implies that a significant portion of main-stem FPOM may be Andean

The actual proportion of FPOC of Andean origin has beenapproximated using delta carbon-13 (δ13C) stable isotopic

ratios as a ldquofingerprintrdquoof its origin Theδ13

C of plant leavesis positively correlated with elevation and ratios in thePeruvian Andes have been found to range from about ndash30permilat 1000 to 2000 masl to ndash26permil at 4000 masl (Townsend-Small et al2005 2007)Thevalues of leaves from prominent

floodplain and upland forest trees along the main-stemriveralso average ndash30permil indicating that there is no clear isotopicseparation of leaf δ13C between lowland forests and Andeanforests below 2000 masl of elevation (approximately 50 of the Andean Amazon area table 1) Unlike plant leaveshow-ever there is a clear separation of FPOCδ13C between Andeanand lowland rivers and this separation can be used toestimatethe relative proportion of each in the main stem FPOC inpurely lowlandrivers hasδ13C values consistently near ndash285permil(Quay et al 1992) The δ13C of FPOC discharged in themain-stem Amazon River at Oacutebidos is ndash274permil and thusindicates a mixture of theAndean and lowland sourcesIf thePeruvian value forδ13C of FPOC exiting the Andes (approx-imately ndash265permil) is taken as the Andean end member andndash285permil is taken as the lowland end member FPOC at Oacutebidosis a mixture of 50Andean FPOC and 50 lowland FPOCAlternatively if the Bolivian end member of ndash255permil is usedFPOC at Oacutebidos is a mixture of 33 Andean and 67lowland FPOC (Quay et al 1992 Hedges et al 2000)

Interestingly the δ13C of FPOC in each of the majorAndean tributaries (the Solimotildees and Madeira rivers) wherethey meet the main stem is ndash268permil This suggests that theserivers carry FPOC that is largely of Andean origin and accountfor 82 of the FPOC input to the main stem If only 30 to50 of FPOC entering the Atlantic Ocean is of Andean ori-gin then there is a 50 to 70 reduction in Andean-derivedFPOC in the main-stem section of the river This reductionprobably occurs through sediment exchange with the flood-plain and gradual decomposition of Andean organic matter

while in storage Recentresearch using a dual-isotope approach(14C and 13C) estimated the degree of mineralization of Andean-derived FPOC with transport downstream andconcluded that nearly all Andean FPOC was mineralized inthe river and floodplain system (Mayorga et al 2005) Takentogether the Andes largely regulate the particulate load tothe main-stem Amazon River not simply with respect to itsparticulate mineral load but also with respect to associatednutrients and organic matter

The four major Andean tributaries contribute approxi-mately 50 of the dissolved organic matter (DOM) input to

the main stem (Richey et al 1990) but unlike particulateorganic matter this DOM appears to derive largely fromlowland sources Neither mass-balance nor chemical-tracerapproaches support important Andean contributions of DOM to the lowland or main-stem Amazon DOM accu-mulates in swampy environments that arecommon through-out the lowland Amazon and in rivers and streams that drainareas of spodosol soils (McClain and Richey 1996) In thecentral Brazilian Amazon fluxes of DOM to groundwater inthe spodosols characteristic of the Rio Negro subbasin areapproximately 20 times greater than those in the oxisols

characteristic of much of the rest of the lowland Amazon(McClain et al 1997) In the Rio Negro basin high ground-waterDOM concentrations (approximately 3000 micromolesof carbon) also appear in surface water draining spodosolswhereas in oxisol terrains fringing wetlands appear to be

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important sources of DOM DOM concentrations are uni-formly low in the few studies on Andean rivers (Guyot andWasson 1994 Hedges et al 2000 Saunders et al 2006) In theMadeira subbasin there is a distinct increase in DOC con-centrations in rivers below 500 masl and this additionalDOC appears to derive from floodplains and wetlands suchas those of the Bolivian Llanos de Mojos (Guyot and Wasson1994)

Andean influences on the productivity of the main-stem AmazonThe productivity of the main-stem Amazon is tied to theproductivity of its floodplain a system built of Andean-derived materials and fueled by mineral nutrients from theAndes (Melack andForsberg 2001)Over a 2010-km reach of the Amazon main stem the mean lateral flux of sediments(1570 to 2070 Tg per year) between the channel and adjoin-ing floodplain exceeds the downstream flux (1200 Tg per

year) andapproximately 500 Tg per year of upstream-derivedsediment and associated nutrients accumulate on the flood-plain and in channel bars (Dunne et al 1998) This processbuilds thefertile floodplain soils alongAndeantributaries andthe main stem By contrast floodplains along non-Andeanlowland tributaries are farmore depleted in mineral nutrientsThe Amazon River maintains year-round lateral exchangeswith its floodplain and especially with its abundant lakesThe floodplain is a highly productive system with an estimatedregional net production of 113 Tg of carbon per year occur-ringoveranareaof 67900km2 from theBrazilianndashColombian

border to near the riverrsquos mouth (figure 5 Melack and Fors-berg 2001) This translates to 17 Mg carbon per hectare per

year which exceeds the productivity of upland Amazonforests by a factor of five in fact the Amazonian floodplainis among the most productive ecosystems on Earth The

majority of primary productivity is attributed to macrophyte(65) and floodplain forest (28) communities Subtract-ing estimates of carbon loss to respiration and burial about90 Tg carbon per year are available for export to the main-stem river where the additional carbon fuels respiration(Melack and Forsberg 2001 Mayorga et al 2005)

A portion of the supply of Andean nutrients to the flood-plain can eventually be traced back into the main stem not only as labile organic matter but as part of myriad organisms thatmove between thefloodplain and channelLarge numbers of fish move onto the floodplain annually to exploit its pro-ductivity and utilize its habitats (Goulding 1993) In factannual movements onto the floodplains of Andean-influencedwhite-water rivers are the most common form of migrationamong Amazon fishes and are critical to maintaining theregionrsquos fisheries (Goulding et al 1997) Of the 24 species intheBrazilian Amazon that are most important to humans (innutritional and economicterms) most migrate as part of theirlife cycle and most rely to some extent on the resourcesdelivered from the Andes (Araujo-Lima and Ruffino 2004)One of the most sought-after fish is the tambaqui(Colossoma

macropomum) This omnivorousfrugivorous fish occursover the length of white-water rivers but only in the lowerreaches of black-water rivers It feeds in flooded forestsduring high water and migrates back into the channelduring low water Tambaqui like many other species spawnsalong the margin of white-water rivers and the larvae arewashed onto floodplains by the rising waters There they feed and seek shelter beneath the ubiquitous macrophyte

beds (Araujo-Lima and Goulding 1997)A number of othercharacids important to Amazon fisheries (Brycon sppMylossoma spp Myleus spp) also follow this migrationpattern (Araujo-Lima andRuffino 2004)using thefloodplainfor feeding and nursery habitats and for transporting

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Figure 5 Nutrients and mineral substrates carried by Andean tributaries and deposited on floodplains fuel the highest

primary productivity rates per hectare in the Amazon basin This schematic illustrates the balance of organic carbon on the main-stem Amazon floodplain between 705degW (west) and 525degW (refer to figure 1 for extent) This balance indicates that large quantities (approximately 90 teragrams) of organic matter are returned to the river channel annually to fuel in-channel respiration All quantities are for total organic carbon unless otherwise noted Source Melack and Forsberg (2001) and Richey and colleagues (1990) Abbreviations DOC dissolved organic carbon POC particulate organic carbon



resources back to the river as they migrate Isotopic tracershave shown that C3 macrophytes floodplain trees andphytoplankton account for 82 to 97 of the carbon in 35species of adult fishes examined (Forsberg et al 1993)Phytoplankton while accounting for a small proportion of the total primary productivity on floodplains represents theprimary source of carbon to characiform fishes (Araujo-Lima et al 1986)

Migrations are also important in distributing theenhancedproductivityof Andean-influenced white-water riversandtheirfloodplains to less productive black-water and clear-waterenvironments ManyAmazon fish migrate from black-waterand clear-water rivers to the main stem and other white-water rivers to spawn In fact all commercially importantspecies appear to spawn only in white waters (Goulding et al1997) During times of the year other than the spawningseason some move back into black-water and clear-waterenvironmentsandin the event of predation or deaththeor-ganic matter and nutrients of their bodies serve as subsidiesto these less productive ecosystems Jaraqui (Semaprochilodus

spp) is an example of a fish that migrates from black-waterrivers into white-water rivers to spawn (figure 6a) Thesepredictable migration routes are stalked by larger predatorsthat congregate at the confluences of black-water and white-water rivers such as the Amazon River dolphinor boto (Inia

geoffrensis )Many other fish use the main stem and its Andean tribu-

tariesas migrationcorridorsmost notably largepredatory cat-fish (Pimelodidae) moving upriver to Andean spawning

areas Catfish making long-distance migrations are quanti-tatively the most important predators in the river systemandthey are also the most important species to fisheries alongtheriverrsquos length (Barthem and Goulding 1997) The most re-markable of thesemigrations is that of the doradoor douradacatfish (Brachyplatystoma spp figure 6b) which travels as faras 5000 km in one direction (Goulding et al 2003) Statisti-cal data on size classes along the entire length of theAmazonRiver reveal that dorado spawn in headwater regions (in-cluding Andean foothills) and that the young are washeddownstreamto nurseryareasin theAmazon estuary(Barthem

and Goulding 1997) Preadult dorado move upriver againcompleting the approximately 8000-km migration over sev-eral years Dorado and a number of other migrating catfishare heavily fished along the river so their numbers are sig-nificantly reduced by the time they reach the rivers of the pied-mont and Andean foothills

In Andean piedmont regions characins emerge as themost important fishery species in biomass the most im-portant among these is Prochilodus nigricans known asboquichico in PeruBoquichico is a fine-particle feeder that in-gests detritus and algaeand has a maximum length of lessthan

40 centimetersDuringthe low-water season it lives in flood-plain lakes and channels of the Amazon piedmont but at theinitiation of rising water it leaves thefloodplain and migratesen masse upAndean tributaries to spawn (Diaz-Sarmiento andAlvarez-Leoacuten 2004) Collectively thefishmigrations illustrate

the critical connections between theAndes and downstreambiotic communities andecologicalprocessesas well as theim-portance of maintaining both lateral and longitudinal con-nectivity throughout the Amazon

Enormous sediment loads fluxes of nutrients and refrac-tory organic matter and ultimately the fertility of the ex-pansive floodplains reflect the many influences of distantAndean mountain ranges on the main-stem Amazon andother white-water tributaries (figure 7)The riverrsquos characterhas been shaped by these materials for more than 10 million

years and its present form and host of diverse organismsare adapted to the annual and interannual cycles of Andeaninputs It is safe to say that the ecology of the modern Ama-zon main stem has been built on substrates and nutrients de-

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Figure 6 Migrations of many Amazon fish are strongly influenced by the pursuit of resources and habitats tied to Andean tributaries (a) The jaraqui ( Semaprochilodus

insignis) is an example of species that as adults live mostly in black-water rivers or lakes but migrate to white-water rivers to spawn Juvenile jaraqui also use white-water floodplains as their nurseries (b) The dourada (Portuguese) or dorado (Spanish) catfish ( Brachyplatystoma spp B rousseauxii in photo) are the farthest-migrating species known in the Amazon They hatch in the Andean foothills use the Amazon estuary as their nursery and then migrate thousands of kilometers up Andean tributaries to spawn Photographs Michael Goulding



rived from the Andes and that the decoupling of the main-stem Amazon from its mountain headwaters would lead todramatic changes in therivermdasha pattern reflected in many of the worldrsquos other great rivers

Andean processes regulating fluxes to lowlands A research frontier TheAndes exert strong influences on themain-stemAmazonand these influences strengthen as onetravels upstream alongthe major Andean tributaries But what processes regulate thefluxes of Andean derived materials and how do theseprocessesvary spatially and temporally in the Andean Amazon Un-fortunately little research to date addresses these questionsand obtaining regional numbers is exceedingly difficultNevertheless current rates of land-use change in the An-dean Amazon are among the highest in the Amazon basin40 or more of the region already has been significantly fragmented and otherwise affected by human alterations(Eva et al 1998)How will land-use change and possible flow regulation alter fluxes of particulates and solutes to the low-land Amazonandwhat other forms of contamination mightbe emitted by growing mountain populations Research

addressing these human-related questions is still relatively re-stricted spatially in theAndeanAmazon but such research isessential forthecoming decadeif effective regionalagreementsare to be forged about the future of the Amazon basin

Concerning sediment fluxes it is important to note that in-stantaneous loads in lowland rivers are largely decoupledfrom those in mountain rivers Where lowland Andean trib-utaries remain ldquowhiterdquo with high sediment loads year-roundmountain rivers are generally clear during the dry seasonand white only during storm-runoff events (Townsend-Smallet al 2008) Their sediment fluxes may fluctuate greatly ondaily or weekly timescales in response to individual storm andlandslide events (Guyot et al 1999) whereas lowland riverfluxes like their hydrographs fluctuate according to damp-enedseasonal cyclesMeandering lowland riversmaintaintheirsediment loads by continually resuspending and depositingmaterials within their channels (Meade et al 1985Dunne etal 1998) effectively mining sediments accumulated in thepiedmont over long timescales through discretedepositionalevents (Aalto et al2003) To understand mountain-lowlandlinkages one therefore needs to consider erosional processesover a broad range of timescales

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Figure 7 Andean influences on the ecology and biogeochemistry of the Amazon may be grouped into three interacting sets of processes Andean exports of water sediment nutrients and organic and biological material exert fundamental control and

produce the white-water characteristics of Andean tributaries and the mainsteam Amazon itself Floodplain building by these Andean-derived materials provides the substrate and nutrition fueling productive flooplain forests macrophyte bedsand lakes Fish migrate throughout these systems and along tributaries capitalizing on the productivity of white-water river systems and transferring a small quantity of Andean-derived energy and nutrients to nutrient-poor black-water and clear-water systems



At timescales stretching into millions of years and at thespatial scale of the entire mountain range climate seems toexert a fundamental control on erosion processes in theAndeanAmazon Montgomery andcolleagues (2001) analyzedthe topographic climatic and tectonic variability of the en-tire Andes cordillera and concluded that morphologyis more

closely related to climate than to tectonic processesErosion from the mountain range over the past 25 million years has come predominantly from the northern AmazonAndes (north of 15deg south) where historical rates of erosionare up totwice as high as in the drier southern portion of theAmazon Andes (southern Peru and Bolivia) Linked to thislong-term erosional history a striking and relevant geomor-phological characteristic of the high Andes is a shift fromsteep-sided V-shaped valleys to gently sloped U-shapedvalleys between 3000 and 3500 masl Although much re-duced in size today glaciers have been important in shaping

highAndean valleys Moreover the gentle valley slopes exposedby glacial retreat result in reduced physical erosion in thehighest portions of the Andes

At subregional spatial scales and shorter timescales vege-tation may assume a first-order control of erosion ratesErosion rates in the Beni and Mamoreacute river basins of Boliviarange from521 to6000metric tons per km2 per year and from310 to 2600 metric tons per km2 per year respectively (Guyotet al1988) Topography lithology rainfall and vegetation allplay roles in explaining differences in erosion between basinsbut vegetation plays the dominant role Rates of erosion are

greatest in the southernmost basins where vegetation issparse In the north where rainfall is greater but subbasinsareheavily forested erosion rates are considerably lower

The controlling influence of vegetation on erosion at bothsubregional andhillslope scales is significantbecause land-usechangeis themost prolific form of anthropogenic disturbancein the Amazon (figure 8) Erosion is less intense in densely veg-etated parts of the Andes despite high rainfall on erosion-prone slopesThe stabilizing effects of natural vegetation arelosthowever followingdeforestationand land managementpractices become important variables in explaining fluxes of

sedimentsorganic matter and nutrients from newly createdagricultural fields and pastures Studies conducted in mid-elevation (2000 to 2500 masl) valleys of the Peruvian Ama-zon find increased fluxes of sediments organic matter andnutrients in rivers draining valleys with greater proportionsof agriculture and pastures (Waggoner 2006) Similar trendshave been observed in the Napo River basin of Ecuadorwhere clear correlations were found between overall riverhealth andthe level of anthropogenic alterations (Celi 2005)Continued investigations of land-use impacts on stream andriver sediment loads are one of the most pressing research

needs in the Andean Amazon today Studies of land-useimpacts on rivers and streams should emphasize riparianzonesboth because they are control points for land-to-rivermaterial transfers (Naiman and Deacutecamps 1997Naiman et al2005) and because they are favored for agriculture in the

Andean Amazon as a result of the relative fertility of their soils(McClain and Cossio 2003)

It was recognized earlyon that concentrations of major ionsand trace elements in Andean Amazon rivers were linked tothe lithologies of the major subbasins and subsequent work has supported this link (Sobieraj et al 2002)Themost focusedimpacts that humans have on major ions and trace-elementfluxes from the Andes is through mining which is wide-spread at higher elevations Contamination of soils and veg-etation by heavy metals has been documented near mines anddownstream of mining operations (Hudson-Edwards et al2001)Accumulationsof metals in river invertebrateshave evenbeen measured downstream of the point at which contami-nation of bottom sedimentsis no longer detectable (Bervoetset al1998)Mercury contamination from placer gold-miningoperations is a significant concern in manyAmazonian areasand mercury accumulations in fish and in the hair of river-ine people have been linked to gold-mining operations as faras 150 km upstream in the upper Beni subbasin of Bolivia(Maurice-Bourgain et al 1999) Although of considerablelocal concern the current impacts from mining appear to belimited to river reaches immediately downstream of miningsites Expansion of mining activities however may eventually lead to significant changes in the fluxes of heavy and tracemetals to adjoining Amazon lowlands Quantifying thecomposition magnitude and ecological consequences of increased heavy metal fluxes is an important need in the An-dean Amazon

The dependence of lowland river corridors on sediments

and nutrients derived from theAndes requires unobstructedconnectivity between the two regions No major Andeantributary to the Amazon is currently dammed althoughBrazil is pursuing plans to build two major dams on theMadeira River Hydroelectric installations arecommonhow-ever on streams and small rivers close to major mining op-erations to urban areas or to other significant humansettlements Peru has five significant hydroelectric projectsunder way in its Amazon region and the Peruvian Ministry of Energy and Mineshas identified dozens more potentialdamsites some on prominent rivers such as the Marantildeon Hual-

laga TamboandUrubamba Dams trap large volumes of sed-iment and could cause major readjustments over the longterm in the geomorphology of downstream river sectionsand the eventual sediment starvation of some downstreamreachesTheill effects of dams on river organisms and riparianenvironments are well known (eg Dudgeon et al 2006)and could be especially destructive in the Andean Amazonwhere biodiversity is high and many fish species migrate an-nually between mountains and the lowland rivers and flood-plains Far too little is known at this point about the extentto which riverine organisms and riparian environments rely

on open linkages between mountains and adjacent lowlandsin the western Amazon It is therefore impossible to predictwhat the short- and long-term consequences of widespreaddam building would beWe suspecton the basis of evidencepresented here and evidence from other regions with

Articles




numerous dams that eventually the consequences would besevere as they have been for other rivers (eg the ColumbiaRiver in the United States)

A wild card in all discussions of future scenarios in theAndean Amazon is theeffect of climate changeincludingthefeedbacks between land use and climate There is already strong spatial variability in todayrsquos Andean climate dueto the

arearsquos topographic complexity Even though the response of Andean environments to El NintildeoLa Nintildea events is compli-cated thetrend is toward heavier than normal rainfall (Kane2000) resulting in increased landslide intensity This may not be the casehowever in the futureRainfall in theAndeanAmazon is sensitive to the water balance of the lowlandAma-zon and this balance is expected to change in predictablewaysBecause rain in the Andean Amazon is ultimately derived fromthe Atlantic Ocean it must be transported across the lowlandAmazon basin in westward-moving air masses During thiswestward movement moisture cycles between the atmos-

phere and land surface and estimations are that roughly 55 of the rain falling in the Amazon basin is derived fromevapotranspiration within the basin (Marengo and Nobre2001) For the eastern slopes of the Andes the percentage of rainfall derived from evapotranspiration is probably higher

Consequently continued deforestation should lead to re-duced levelsof precipitationin theAndean Amazon (Chagnonand Bras 2005)

Both elevated carbon dioxide (CO2) and the conversion of forest to managed uses are predicted to reduce evapo-transpiration andthus theamount of water moving westwardtoward the AndesElevated CO2 alone is predicted to reduce

evapotranspiration in the Amazon by about 4 through re-ductions in stomatal conductanceandthis should also reducerainfall Conversion of forest to pasture across the entireAmazon basin is predicted to reduce evapotranspiration by as much as 20 (Lean et al 1996) These changes in theregional water balance will certainly affect terrestrial andaquatic ecosystems of theAndean Amazon and thereby fun-damentally alter the mountain-to-lowland fluxes discussedhere As investigations of these questions proceed at a basinscale and as confidence in predicted changes increases An-dean policymakers should carefully examine local impacts

The Amazon River system is unique in many waysbecause of its size and orientation along the equator but thecontrols by its Andean headwaters are not unique In factmany of the mountain-lowland linkages we have discussedshould be relevant to other major river systems Similar

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Figure 8 The Oxapampa Valley in central Peru illustrates a number of the forces threatening the ecological health of Andean and downstream river reaches including the deforestation and cultivation of steep slopes and the urban development of narrow valley bottoms Future damming of valleys such as this could significantly affect downstream fluxes of sediments and nutrients Photograph courtesy of Thomas Saunders



controls are certainly observed in the adjoining OrinocoRiver system (Edmond et al 1996 Jepson and Winemiller2007) and are likely to be important in the major riversdraining the Himalayas namely the Indus Ganges Brahma-putra and MekongThe fundamental ecological importanceof these linkages stresses the need to manage even theworldrsquos

largest rivers in a basin contextAlthough our knowledge of the nature and magnitude of mountain-lowland linkages in the Amazon basin can serve toinform research and management in the Amazon and inbasins around the world much remains to be learnedResearch in recent decades has illuminated the nature andmagnitude of mountain-lowland linkages along the main-stem Amazon river but investigations in the Andes lag farbehind Researchers still know little about the fluxes of sed-iments and associated nutrients from the Andes on a re-gional scale and even less about the spatial and temporalvariability in those fluxes We know equally little about the de-gree to which river organisms depend on habitat and otherresources of Andean rivers during annual and multiyear mi-grations In themidst of our incomplete ecological knowledgethe Andes are being rapidly transformed into a managedlandscape where rivers are modified and where montaneforests and high-altitude grasslands are converted to pas-tures and agricultural fields Filling these knowledge gaps isan immediate scientific challenge with important ramifica-tions for the sustainability of the Amazon River basin as awhole Brazil the downstream beneficiary of Andean inputsfrom its upstream neighbors should take special interest inthese issues Over the long term the most productive com-ponents of the Brazilian Amazon River system are also themost vulnerable to poor management decisions in the AndesBrazilrsquos own plans for large-scale hydroelectric developmentnew road buildingandagricultural intensification should pay similar consideration to theimportant hydrological and eco-logical linkages uniting the larger basin

AcknowledgmentsWe wish to acknowledge our colleagues and collaborators intheAndeanAmazon who have informed andinfluenced ourunderstanding of Andean-Amazon linkages especially Jay Brandes Remigio Galarraga Michael Goulding Jean LoupGuyot Carlos Llerena Joseacute Efrain RuizRichard Chase Smithand Amy Townsend-Small We thank the Inter-AmericanInstitutefor Global Change ResearchtheUS National ScienceFoundationand theAndrew W Mellon Foundation for sup-porting our research in the Amazon basin Daniel Gann andAnna Boyette providedcritical support with graphicsMichaelGoulding Margi Moss and Thomas Saunders contributedphotos This manuscript was improved by the comments of John Melack and three anonymous reviewers

References citedAalto R Maurice-Bourgoin L Dunne T Montgomery DR Nittrouer CA

Guyot JL 2003 Episodic sediment accumulation on Amazonian floodplains influenced by El NintildeoSouthern OscillationNature 425493ndash497

Allegre CJ Dupre B Negrel P Gaillardet J 1996 Sr-Nd-Pb isotope system-atics in Amazon and Congo river systems Constraints about erosionprocesses Chemical Geology 131 93ndash112

Araujo-Lima CARM Goulding M 1997 So Fruitful a Fish EcologyConservation and Aquaculture of the Amazonrsquos Tabaqui New YorkColumbia University Press

Araujo-Lima CARM Ruffino ML 2004 Migratory fish of the BrazilianAmazon Pages 233ndash302 in Carolsfield J Harvey B Ross C Baer A eds

MigratoryFishes of South America Biology Fisheriesand ConservationStatus Victoria (Canada) World Fisheries Trust World Bank Inter-national Development Research Centre

Araujo-Lima CARM Forsberg BRVictoria RLMartinelli LA1986Energy sources for detritivorous fishes in theAmazonScience 2341256ndash1258

Aufdenkampe AK Mayorga E Hedges JI Llerenac C Quay PD GudemanJKrusche AV Richey JE2007Organic matter in thePeruvian headwatersof theAmazonCompositional evolution from theAndes to thelowlandAmazon mainstem Organic Geochemistry 38 337ndash364

Barthem R Goulding M1997The Catfish ConnectionEcology Migrationand Conservation of Amazon Predators New York Columbia Univer-sity Press

Bates HW 1863 The Naturalist on the River Amazon London John

MurrayBerner RARao JL1994Phosphorus in sediments of theAmazon river andestuary Implications for the global flux of phosphorus to the seaGeochimica et Cosmochimica Acta 58 2333ndash2339

Bervoets LSolis D Romero AMVan Damme PAOllevier F 1998Trace metallevels in chironomid larvae and sediments from a Bolivian river Impactof mining activitiesEcotoxicologyand Environmental Safety41 275ndash283

Carvalho NO da Cunha SB 1998 Estimativa da carga soacutelida do rioAmazonas e seus principais tributaacuterios para a foz e oceano Uma retro-spectiva A Agua em Revista 6 44ndash58

CeliJE 2005 The vulnerability of aquatic systems of the Upper Napo RiverBasin (Ecuadorian Amazon) to humanactivitiesMasterrsquos thesis FloridaInternational University Miami

Chagnon FJF Bras RL2005Contemporary climate changein theAmazon

Geophysical Research Letters 32 L13703 doi1010292005GL022722Devol AH Hedges JI2001 Organic matter and nutrients in the mainstem

Amazon River Pages 275ndash306 in McClain ME Victoria RL Richey JEeds The Biogeochemistry of the Amazon Basin New York OxfordUniversity Press

Diaz-Sarmiento JAAlvarez-Leoacuten R 2004Migratory fish of the ColombianAmazon Pages 303ndash334 in Carolsfield J Harvey B Ross C Baer A edsMigratoryFishes of South America Biology Fisheriesand ConservationStatus Victoria (Canada) World Fisheries Trust World Bank Inter-national Development Research Centre

Dudgeon D et al 2006 Freshwater biodiversity Importance status andconservation challenges Biological Reviews 81 163ndash182

Dunne T Mertes LA Meade RH Richey JE Forsberg BR 1998 Exchanges

of sediment between the flood plain and channel of the Amazon Riverin Brazil Geological Society of America Bulletin 110 450ndash467

Edmond JM Palmer MR Measures CI Brown ET Huh Y 1996 Fluvialgeochemistry of the eastern slope of the northeastern Andes and itsforedeep in the drainage of the Orinoco in Colombia and VenezuelaGeochimica et Cosmochimica Acta 60 2949ndash2976

Eva HD Glinni A Janvier P Blair-Myers C 1998 Vegetation Map of SouthAmerica at 15000000 Luxembourg (Luxembourg) European Com-mission TREES Publications Series D2 EUR 18658 EN

Forsberg BR Araujo-Lima CARM Martinelli LA Victoria RL Bonassi JA1993Autotrophic carbon sources for fishof the CentralAmazon Ecol-ogy 74 643ndash652

Gibbs RJ 1967 The geochemistry of the Amazon river system part 1 Thefactors thatcontrol the salinityand the composition and concentrationof suspendedsolids Geological Society of America Bulletin 781203ndash1232

Goulding M1993 Flooded forests of the Amazon ScientificAmerican 266114ndash120

Goulding M Smith NJH Mahar D 1997 Floods of Fortune Ecology andEconomy along the Amazon New York Columbia University Press

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Goulding M Cantildeas C Barthem R Forsberg B Ortega H 2003 AmazonHeadwatersmdashRivers Wildlife and Conservation in Southeastern PeruLima (Peru) Eco News and Graacutefica Biblos

Guyot JL Wasson JG 1994 Regional pattern of riverine dissolved organiccarbon in the Bolivian Amazonian drainage basin Limnology andOceanography 39 452ndash458

Guyot JLBourges J Hoorelbecke R Roche MA Calle H Cortes J GuzmanMCB 1988 Exportation de matiegraveres en suspension des Andes vers

lrsquoAmazonis par le Rio Beni BoliviePages 443ndash452 in Bordas MPWallingDEedsSediment BudgetsmdashProceedings of the Porto Alegre SymposiumWallington (CT) IAHS Press IAHS publication no 174

Guyot JLQuintanillaJCallidonde M Calle H 1992 Distribucioacutenregionalde la hidroquiacutemica en la cuenca Amazonica de Bolivia Pages 135ndash144in Roche MA Bourges J Salas E Diaz C eds Seminario sobre elPHICAB La Paz (Bolivia)ProgrammeHydrologiqueet Climatologiquede Bolivie

Guyot JL JouanneauJMWassonJG 1999Characterisation of river bed andsuspended sediments in the Rio Madeira drainage basin (BolivianAmazonia) Journal of South American Earth Sciences 12 401ndash410

Hedges JIErtel JRQuayPDGrootesPM Richey JEDevol AHFarwellGWSchmidt FW Salati E 1986 Organic carbon-14 in the Amazon River

system Science 231 1129ndash1131Hedges JIet al2000 Organic matter in Bolivian tributaries of theAmazon

River A comparison to the lower mainstem Limnology and Ocean-ography 45 1449ndash1466

Hudson-Edwards KA Macklin MG Miller JR Lechler PJ 2001 Sourcesdistribution and storage of heavy metals in the Rio Pilcomayo BoliviaJournal of Geochemical Exploration 72 229ndash250

Jepson DBWinemiller KO 2007 Basin geochemistry and isotopic ratios of fishes and basal production sources in four neotropical rivers Ecology of Freshwater Fish 16 267ndash281

[JRC] Joint Research Centre European Commission 2000 Global LandCover 2000 (26 February 2008 www-gvmjrcitglc2000 )

Junk WJ ed 1997 The Central Amazon Floodplain Ecology of a Pulsing

System Berlin SpringerKane RP 2000 El NintildeoLa Nintildea relationship with rainfall at Huancayo inthe Peruvian Andes International Journal of Climatology 20 63ndash72

Keil RG Mayer LM Quay PD Richey JE Hedges JI 1997 Loss of organicmatter from riverine particles in deltas Geochemica et CosmochimicaActa 61 1507ndash1511

Lean J Bunton CB Nobre CA Rowntree PR 1996 The simulated impactof Amazonian deforestation on climate using measured ABRACOSvegetation characteristics Pages 549ndash576 in Gash JHC Nobre CARoberts JM Victoria RL eds Amazonian Deforestation and ClimateNew York Wiley

Marengo JA Nobre CA 2001 General characteristics and variability of climate in the Amazon basin and its links to the global climate systemPages 17ndash41 in McClain ME Victoria RL Richey JE eds The Bio-geochemistry of the AmazonBasinNewYork OxfordUniversity Press

Maurice-Bourgoin L Quiroga I Guyot JL Malm O 1999 Mercury pollu-tion in the upper Beni river Amazonian basin Bolivia Ambio 28302ndash306

Mayorga EAufdenkampeAK Masiello CAKrusche AV Hedges JIQuay PDRichey JEBrown TA 2005 Young organic matter as a sourceof carbondioxide outgassing from Amazonian rivers Nature 436 538ndash541

McClain ME Cossio RE 2003 The use and conservation of riparian zonesin therural Peruvian AmazonEnvironmental Conservation 30242ndash248

McClain ME Richey JE 1996 Regional-scale linkages of terrestrial andlotic ecosystems in the Amazon basin A conceptual model for organicmatter Archiv fuumlr Hydrobiologie (suppl) 113 111ndash125

McClain ME Richey JE Brandes JA Pimentel TP 1997 Dissolved organic

matter and terrestrial-lotic linkages in the central Amazon basin of Brazil Global Biogeochemical Cycles 11 295ndash311

McClain MEVictoria RLRicheyJEeds2001The Biogeochemistry of theAmazon Basin New York Oxford University Press

Meade RH1994Suspended sedimentsof themodern Amazon and Orinocorivers Quaternary International 21 29ndash39

Meade RH Dunne T Richey JE Santos UdM Salati E 1985 Storage andremobilizationof sediment in the lowerAmazon River of Brazil Science228 488ndash490

Meggars BJ 1984 The indigenous peoples of Amazonia their culturesland usepatterns andeffects on the landscape and biota Pages627ndash648in Sioli H ed The Amazon Limnology and Landscape Ecology of aMighty Tropical River and Its BasinHingham (MA) KluwerAcademic

Melack JM Forsberg BR 2001 Biogeochemistry of Amazon floodplain

lakes and associated wetlands Pages 235ndash274 in McClain ME VictoriaRLRicheyJEedsThe Biogeochemistry of theAmazon Basin New YorkOxford University Press

Mena CA Bilsborrow R McClain ME 2006 Socioeconomic drivers of deforestation in the Napo River Basin of Ecuador EnvironmentalManagement 37 802ndash815

Montgomery DR Balco G Willett SD 2001 Climate tectonics and themorphology of the Andes Geological Society of America Bulletin 29579ndash582

Naiman RJ Deacutecamps H 1997 The ecology of interfaces Riparian zonesAnnual Review of Ecology and Systematics 28 621ndash658

Naiman RJDeacutecamps H McClainME2005RipariaEcology Conservationand Management of Streamside Communities New York Elsevier

Quay PD Wilbur DO Richey JEHedges JIDevol AHMartinelli LA1992Carbon cycling in the Amazon River Implications from the 13Ccomposition of particulate and dissolved carbon Limnology andOceanography 37 857ndash871

Richey JE Victoria RL 1993 C N and P export dynamics in the AmazonRiver Pages 123ndash140in Wollast R Mackenzie FT ChouLedsInteractionsof C N P and S Biogeochemical Cycles and Global Change BerlinSpringer

Richey JEHedgesJI Devol AHQuay PD 1990 Biogeochemistry of carbonin the Amazon RiverLimnology and Oceanography 35 352ndash371

Richey JE Melack JM Aufdenkampe AK Ballester VM Hess L 2002Outgassing from Amazonian rivers and wetlands as a large tropicalsource of atmospheric CO2 Nature 416 617ndash620

Saunders TJ McClain ME Llerena CA 2006 The biogeochemistry of dissolved nitrogen phosphorus and organic carbon along terrestrial-aquatic flowpaths of a montane headwater catchment in the PeruvianAmazon Hydrological Processes 20 2549ndash2562

Sioli H ed 1984 The Amazon Limnology and Landscape Ecology of aMighty Tropical River and ItsBasinDordrecht (Netherlands) W Junk

Sobieraj JAElsenbeer H McClain M 2002 The cation and silica chemistry of a Subandean river basin in western Amazonia Hydrological Processes16 1353ndash1372

Stallard RF Edmond JM 1983 Geochemistry of the Amazon 2 The influ-ence of geology and weathering environment on the dissolved loadJournal of Geophysical Research 88 9671ndash9688

Townsend-Small A McClain ME Brandes JA 2005 Contributions of

carbon and nitrogen from the Andes Mountains to the Amazon RiverEvidence from an elevational gradient of soils plants and river mater-ial Limnology and Oceanography 50 672ndash685

Townsend-Small A Noguera JL McClain ME Brandes JA 2007 Radio-carbon and stable isotope geochemistry of organic matter in the Ama-zon headwaters Peruvian Andes Global Biogeochemical Cycles 21GB2029 doi1010292006GB002835

Townsend-Small A McClain ME Hall B Llerena CA Noguera JL BrandesJA 2008 Contributions of suspended organic matter from mountainheadwaters to the Amazon River A one-year time series study in thecentral PeruvianAndesGeochimica et CosmochimicaActa 72 732ndash740

Waggoner LA 2006 Land use controls on water quality and aquatic eco-systems in the Andean Amazon Peru Masterrsquos thesis Florida Inter-

national University MiamiWallaceAR 1853A Narrative of Travels on the Amazon andRioNegrowith

an Account of the Native Tribes and Observations on the ClimateGeology and Natural History of the Amazon Valley London Reeve

doi101641B580408Include this information when citing this material

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500ndash1000 111804 18

1001ndash2000 170514 27

2001ndash3000 117018 19

3001ndash4000 120671 194001ndash5000 100766 16

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1001ndash2000 170514 27

2001ndash3000 117018 19

3001ndash4000 120671 194001ndash5000 100766 16

gt 5000 2444 lt 1

Total 623217 100













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Wetland 231 lt 1

Cropland 71216 11

Dryland 6375 1

Water 1832 lt 1

Ice 1031 lt 1

Urban 394 lt 1

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Water 1832 lt 1

Ice 1031 lt 1

Urban 394 lt 1

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andean influences on the biogeochemistry and ecology of the amazon river 2008

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