the effects of urbanization on biodiversity and water quality ... ps001.pdfsituation for the rio das...
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11
American Fisheries Society Symposium 47:11–22, 2005© 2005 by the American Fisheries Society
The Effects of Urbanization on Biodiversity and Water Qualityin the Rio das Velhas Basin, Brazil
PAULO S. POMPEU* AND CARLOS BERNARDO M. ALVES
Projeto Manuelzão – Universidade Federal de Minas GeraisAvenida Alfredo Balena, 190 /10.012 Belo Horizonte (MG) Brazil 30130-100
MARCOS CALLISTO
Universidade Federal de Minas Gerais, ICB, Departamento de Biologia GeralLaboratório de Ecologia de Bentos, CP. 486 Belo Horizonte (MG) Brazil 30161-970
Abstract.—In Brazil, most urban sewage is discharged without treatment into rivers. This is thesituation for the Rio das Velhas, which receives in its upper course the sewage of the state capital ofMinas Gerais, Belo Horizonte, with more than 2.4 million inhabitants. Our study focuses on theeffects of basin urbanization on aquatic biodiversity and water quality in the Rio das Velhas. We usethe assemblage structure and taxonomic composition of fishes and benthic macroinvertebrates asbiological indicators of water quality. Effects of Belo Horizonte’s discharge included changes inwater quality and declines in fish and benthos richness and diversity. However, the absence of damsin the Rio das Velhas main course, associated with connectivity with the Rio São Francisco systemand tributaries in excellent condition, increase its rehabilitation potential.
* Corresponding author: [email protected]
Introduction
Rivers have an important role in the biosphere as con-duits for water, nutrients, sediments, woody debris,and biota from the continents to the sea. They areused by humans for transportation, fisheries, hydro-power, and domestic, industrial, and agricultural wa-ter supplies (Petts 1989). Rivers also support uniqueand complex ecological communities and often influ-ence the structure and functioning of the surround-ing terrestrial ecosystem. Because of this, and the criticalrole of freshwater as a human resource, ecologists areincreasingly asked to assess or monitor river “health,”“status,” or “condition” (Bailey et al. 2004).
Changes in environmental factors often initiatequalitative modifications in species composition andbiodiversity. For example, eutrophication may cause ashift in primary producers, which in turn may changefaunal species composition. Through time, a sequenceof modifications may give rise to a fundamentally al-tered trophic network structure and function (Marqueset al. 2002). Many rivers, streams, lakes, and reservoirshave been damaged as a consequence of the increasing
impact of human activities (McAllister et al. 1997).This situation is particularly noticeable in areas of densehuman population, especially in the urban environ-ment, where watercourses show highly degraded wa-ter quality, receiving not only a great amount ofdomestic and industrial wastewater, but also sedimentsand trash. Thus, urban rivers have been transformed,losing their natural characteristics, many of them pre-serving little of their original biological diversity (Sheppand Cummins 1997).
In Brazil, most urban sewage is discharged with-out treatment into rivers. In addition, in large cities,rivers and streams are canalized or placed below streetsin culverts. Intensive urbanization along Brazilian riv-ers has contaminated water bodies, thereby increasingwater-born diseases and altered catchment hydrogra-phy and hydrology, which in turn has increased flood-ing, land sliding, and siltation of navigation channels.These same physical and chemical changes in Brazil’surban rivers have also markedly altered their aquaticbiota (Tundisi 2003).
For more than a century, Brazilian water resourcemanagement has been dominated by outdated legaldoctrines, weak implementation of good laws, and afocus on water chemistry. Yet the most direct and ef-
12 POMPEU ET AL.
fective measure of water body condition is the statusof its living systems. These systems are the product ofmillennia of adaptation to climatic, geological, chemi-cal, and biological factors. Biota integrate everythingthat has happened where they live, as well as what hashappened upstream and upland. When somethingalters the landscape around rivers´ headwaters, life inlowland reaches is affected (Karr and Chu 1999). Al-though the neotropical biogeographic area is the world’srichest region for freshwater fish species (around 8,000species, Schaefer 1998), there are few published stud-ies regarding the effects of urbanization on neotropicalaquatic fauna. Our study focuses on the effects ofbasin urbanization on aquatic biodiversity and waterquality in the Rio das Velhas. We use the assemblagestructure and taxonomic composition of fishes andbenthic macroinvertebrates as biological indicators ofriver quality.
Methods
Study Area
The Rio São Francisco basin, with an area of 631,133km2, covers 7.4% of Brazil. It is situated between 21o
and 7°S latitudes and receives precipitation rangingfrom 350 to 1,900 mm in average years. The Rio SãoFrancisco has an average annual discharge of 100 ×109 m3 with an average flow of 3.150 m3/s at its mouth(PLANVASF 1986). The 2,900-km river crosses fiveBrazilian states and is the 31st longest river in theworld (Welcomme 1985). Its water is used for electric-ity generation, irrigation, urban and industrial sup-plies, navigation, and fisheries (Diegues 1994).
The Rio das Velhas is the longest tributary in theSão Francisco basin. It is oriented in a southwest tonortheast direction and extends 761 km from its head-waters, at an altitude of 1,520 m, to its confluencewith the São Francisco River, at an altitude of 478 m.The estimated average annual flow is 300 m3/s (Q95%= 103.69 m3/s) with a drainage area of 29,173 km2
and a mean width of 38.3 m (CETEC 1983).The headwaters of the Rio das Velhas are located
in a transition zone between the Atlantic rainforestand cerrado, which is a common savanna-like vegeta-tion of central Brazil. Both biomes are identified asworld biodiversity hotspots because they have excep-tional concentrations of endemic species undergoingrapid habitat loss (Myers et al. 2000). Below its head-waters to its mouth, it flows only through cerrado.Another vegetation formation occurs near high eleva-tion headwaters: the “campos rupestres,” or rocky
shrublands, such as seen in the Rio Cipó, one of itsmost important tributaries. This formation is very richin floral and faunal species, with high diversity andendemism (Costa et al. 1998).
The Rio das Velhas has significant social and eco-nomical importance. Belo Horizonte, the state capitalof Minas Gerais, with more than 2.4 million inhabit-ants (IBGE 2000), is located about 100 km from theRio das Velhas headwaters. The river provides most ofthe city’s water supply. The metropolitan region ofBelo Horizonte (MRBH) consists of 34 counties situ-ated around the capital. The total human populationof MRBH is approximately 4.5 million people. Thesewage from 3.2 million people is collected, but only27.5% of it receives secondary treatment. In addition,MRBH is the most industrialized region of the state.The combination of sewage and industrial waste hasmade the Rio das Velhas the most polluted large riverof Minas Gerias State.
The effect of native Americans on the region isunknown. But the settlement of Minas Gerais (trans-lates to General Mines) by Europeans initiated exten-sive mining and contributed to degradation thatcontinues to this day. Also, gold and gem explorationsin the early 16th century produced the towns of Sabaráand Ouro Preto. The changes caused by mining weregreatest in the gravel plains and on the riverbeds (Dean1996). Situated on the banks of the Rio Arrudas, BeloHorizonte is located about 100 km from the Rio dasVelhas headwaters, Belo Horizonte was built in 1897to be the capital of the state of Minas Gerais. Since1898, an industrial and urban center emerged andstarted a new cycle of mining activities, mainly charac-terized by iron mines and iron industries next to theRio das Velhas (FUNDO-FUNDEP 2000). Presently,the Rio das Velhas is severely damaged by urbaniza-tion and mining activities in its watershed. However,well-preserved tributaries with low human densitypersist in the basin. The most important source ofpollution is located on the river’s upper course, wheremining debris and most of the domestic and indus-trial wastewater from the MRBH are discharged.
The capital’s urban concept was oriented to therationalist philosophy of humans dominating nature(SUDECAP 2001). Therefore, the city was designedwith no concern for regional hydrography (Figure 1).Small and large streams were canalized to accommo-date roads, waste, and sewage. Until 2000, the floodcontrol policy of the MRBH was rapid water evacua-tion through canals and revetted streambeds. About200 km of watercourses have been canalized in thecity of Belo Horizonte, representing one-third of the
13THE EFFECTS OF URBANIZATION ON BIODIVERSITY AND WATER QUALITY
drainages in the MRBH (SUDECAP 2001). Onlyrecently, some streams have been chosen for environ-mental rehabilitation and sanitation in their naturalcourses.
Sampling Design
Water quality and benthos.—Water quality andbenthos sampling sites included six stations along theRio das Velhas main stem (Figure 2). In relation to theMRBH discharges, one site is located upstream (SãoBartolomeu – RV-01), two in the MRBH (Sabará –RV-02 and Lagoa Santa – RV-03), and three down-stream (Curvelo – RV-04, Corinto – RV-05 andLassance – RV-06). Mean distance between sites was59 km. For the analysis, these sites were grouped into
upper (RV-01 and RV-02), middle (RV-03 and RV-04), and lower (RV-05 and RV-06) courses.
We also sampled another 13 tributary sites in theMRBH, including one located upstream and anotherdownstream of each sewage treatment plant that is be-ing built in Onça and Arrudas tributaries. The siteswere chosen for geographic location above and belowdisturbances, common physical characteristics, and easeof access. Substrate types at most sites included sand,cobble, and vegetation in canalized third- to fifth-orderreaches. But there was no substantial difference in sitesubstrate (>90% sandy bottom), and common habitattypes (riffles in streams and mid-channel in rivers) weresampled at all sites. Site length was 5–10 times theaverage bank-full width of the stream (as suggested byNewbury 1984). Sites were located away from the influ-
FIGURE 1. Plan of Belo Horizonte downtown, indicating the original (top) and current (bottom) stream courses.
14 POMPEU ET AL.
FIGURE 2. Rio das Velhas basin, sampling stations and relative position in Minas Gerais State and Brazil.
15THE EFFECTS OF URBANIZATION ON BIODIVERSITY AND WATER QUALITY
ence of tributaries or other water bodies. When a streamwas sampled at more than one site, the sites were sepa-rated by a minimum of 120–150 stream widths or 10–15 pool-riffle sequences. Thus, in streams with an averagewidth of 10 m, sites were 50–100 m long and had aminimum of 1.2 km between adjacent sites on the samestream (as suggested by Bailey et al. 2004). We sampledin the rainy and dry seasons.
Temperature, dissolved oxygen, conductivity, tur-bidity, and pH were measured in situ using a Horiba U-10 multi-probe and portable YSI samplers. Depth andvelocity were measured with a Global Water flowmeter.We collected one water sample from each site with aVan Dorn sampler in the morning (0900–1100 hours),stored the bottles in an ice box for less than 4 h, andtook samples to the metropolitan laboratory of COPASA(Companhia de Sanea-mento de Minas Gerais) for de-termination of total and dissolved nutrients (total-P,total-N, nitrite, nitrate, organic-N, and NH
4+) and total
dissolved solids, according to Lenore et al. (2002). Forthe microbiologic analyses (thermotolerant coliforms,total coliforms, Escherichia coli and fecal streptococcus),two subsurface water samples were taken directly intosterile glass bottles and returned to the COPASA labo-ratory, where they were kept on ice and processed within8 h. Total and fecal coliforms were determined usingthe most probable number method (MPN; Lenore etal. 2002).
Five random sediment samples were collected ateach site with a Van Veen dredge (area of 0.045 m2),without focusing on a specific habitat. In the labora-tory, samples were washed through 1.00-, 0.50-, and0.25-mm sieves, sorted under a stereomicroscope, andidentified organisms were deposited in the ReferenceCollection of Benthic Macroinvertebrates of the Insti-tute of Biological Sciences, Federal University of MinasGerais, Brazil. Insects were identified to genus and oth-ers to family, according to Cranston (2000), Domínguezet al. (2001), Epler (2001), Pérez (1988), and Trivinho-Strixino and Strixino (1995). We determinedgranulometric composition of the sediments as proposedby Suguio (1973), and modified by Callisto and Esteves(1996). Organic matter content of sediment was deter-mined by ashing previously dried samples in an oven at550°C for 4 h.
Fish.—Fish sampling stations include the same sixbenthos and water quality sites along the Rio das Velhasmainstem and five well-preserved tributaries: Cipó (CP-01 and CP-O2), Bicudo, (BI-01), Curimataí (CU-01),Pardo Grande (PG-01), and da Onça (ON-01) rivers(Figure 2). These tributaries were included to comparemain-stem sites, affected by a huge urbanized area, with
water courses located in areas with low human density.Except for Rio Cipó, which was sampled five times,every sampling station was visited two or three timesfrom 1999 to 2002, including at least one dry and onewet season.
Fish were caught with gill nets (20 m long, with 3-to 16-cm stretch mesh), seines (5 m long and 1-mmmesh), cast nets (3-cm stretch mesh), and kick nets (1-mm mesh). Gillnets were fished in the water columnfor 14 h overnight. Seines were used in shallow areas orlittoral zones, kick nets were employed in nearshoreaquatic macrophytes and in riffles, and cast nets wereused in habitats too deep to wade. The three latter meth-ods were employed for 1–3 h and used only qualita-tively to maximize the number of species collected.Reaches 50–100 m were surveyed, depending on depthand water flow. All sampled fishes were identified tospecies and specimens were placed in the University ofSão Paulo Zoology Museum (MZUSP).
Results
Water Quality
The Rio das Velhas upper course waters were slightlyalkaline to slightly acidic, intermediate in conductivityand total suspended solids, well oxygenated, and rela-tively clear (Table 1). The sediment organic matter waslow. Total phosphorus and total nitrogen were also low.
The MRBH tributaries were slightly acidic to alka-line, with very low dissolved oxygen (Table 1). Com-paring the sampling stations upstream and downstreamof the two Belo Horizonte sewage treatment plants(STPs), substantial differences were found in pH (8.6upstream and 7.43 downstream for Onça and 7.13upstream and 5.8 downstream for Arrudas), with verylow oxygen levels in both streams (<0.5 mg/L). In bothtributaries, conductivities were relatively high (>350µS/cm), and the waters were very turbid (>100 NTU),with high TDS (244–428 mg/L). Sediments were sandywith 0.66–48.01% dry weight of organic matter. Nu-trient concentrations were high (total N = 16.66 ±4.83 mg/L, total P = 2.16 ± 1.28 mg/L).
Baleares, Onça, and Cardoso are the most impor-tant tributaries in MRBH and showed the highest con-centrations of microorganisms (>2.3 × 107 coliforms/mL, >2.4 × 105 E. coliform/mL), low oxygen levels (<2.0mg/L), high conductivity (219 ± 187 µS/cm) and nu-trient concentrations (total N = 14.3 + 6.9 mg/L, totalP = 0.97 ± 1.12 mg/L), moderate turbidity (30–143NTU), slightly acidic to slightly alkaline pH (6.8–7.7), and sandy sediments.
16 POMPEU ET AL.
TA
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17THE EFFECTS OF URBANIZATION ON BIODIVERSITY AND WATER QUALITY
The middle stretch of Rio das Velhas had slightlyalkaline to slightly acidic waters, intermediate con-ductivity, and was well oxygenated (Table 1). A con-siderable number of coliform and fecal streptococuswere seen, indicating contamination by directly dis-charged, domestic untreated sewage from the MRBHtributaries.
In the lower course of the Rio das Velhas, oxygenwas 6.2 ± 0.5 mg/L at Barra do Guaicuí and 8.0 ± 0.3mg/L, between Corinto and Augusto de Lima counties(Table 1). The sediments had low organic matter (1.15%at Corinto and Augusto de Lima, and 15.47% atLassance), but waters showed high conductivity (275µS/cm at Lassance) and high turbidity (143 NTU atBarra do Guaicuí).
Benthic Macroinvertebrates
Benthic macroinvertebrates were dominated by oli-gochaetes (87.9%), chironomids (mainly Chironomusand Polypedilum – 8.25%), and other dipterans, suchas Psychodidae (3.78%). In the upper reach (RV-01,RV-02), tolerant taxa were found in high densities,mainly dominated by chironomids (Ablabesmyia,Chironomus, Cryptochironomus, Fissimentum, Polyp-edilum), psychodids, empidids, elmids, odonates,Biomphalaria straminea, and oligochaetes. A total of13 taxa were found. Numerically dominant taxa in-cluded chironomids (up to 1,000 ± 250/m2), Physa(120,000 ± 45,000/m2), Biomphalaria straminea (250± 65/m2), and oligochaetes (4,300 ± 1,500/m2).
In the MRBH tributaries, we found 12 taxa, withnumerical dominance by oligochaetes (74,000 ±25,000/m2), chironomids (up to 13,000 ± 5,600/m2,mainly Chironomus and Polypedilum), and psychodids(up to 4,000 ± 2,500/m2).
In the middle Rio das Velhas (RV-03, RV-04), wecollected 21 taxa, with Sphaeriidae (1,926 ± 1,461/m2), chironomids (1,600 ± 1,300/m2), hirudineans(1,400 ± 1,800/m2), and oligochaetes (93,000 ±60,700/m2) most abundant.
In the lower reach (RV-05, RV-06), 23 taxa werefound and the introduced Asian snail Melanoidestuberculatus (607 ± 405/m2) was abundant, as well asSphaeriidae (415 ± 551/m2), Physa (919 ± 821/m2),and Elmidae (452 ± 538/m2).
Fish
Fish and macroinvertebrates had similar distributionpatterns along the Rio das Velhas main channel. Fishrichness and Shannon Diversity Index of benthic
macroinvertebrates decreased downstream of theMRBH streams, between sampling sites RV02 andRV03 (Figure 3). This effect was greatest during thedry season, but was moderated by water dilution inthe rainy season. The effects of urbanization on thefish fauna of the main stem were also marked in com-parison with tributaries. The 81 species recorded inthe tributaries represent almost 83% of the total fishspecies of the whole basin, including native and alienrecords. We found 37 species (34% of local fauna)exclusively in these tributaries. The sampling stationslocated in the main stem also had the larger number ofalien species, especially those sites located immediatelydownstream of Belo Horizonte (Table 2).
Discussion
According to Brazilian law, (regulation number 1469,29 December 2000), all of the studied reaches of Riodas Velhas are inappropriate for human consumptionwithout prior treatment and inappropriate for primarycontact, aquatic sports, and bathing. The Rio das Velhashas very low potential for recreational use without fur-ther treatment by the sanitary company (COPASA-MG). Most Brazilian cities have experienced uncon-trolled development and increased occupation of rivermargins and their floodplains. Many cities are trying tosolve problems of sanitation and flooding with rivercanalization. Canalization increases water velocities, re-ducing residence time and accelerating domestic efflu-ent and pollutant transport. Such changes also lowerrichness and diversity in the Rio das Velhas downstreamof MRBH, highlighting the effects of sewage dischargeon the main channel. However, urbanization costs areeven higher in the small water courses draining themetropolitan area. Besides the poor benthos assemblageand water quality, pollution and canalization of MRBHstreams have eliminated most native fish species. Only afew well-preserved headwater reaches, protected as natu-ral reserves or water supply sources, support typical head-water fishes, such as Trichomycterus and Astyanax.
Urbanization has also changed fish assemblages inthe natural lakes of the MRBH. Lagoa Santa is a shallowpermanent lake located north of Belo Horizonte, insidethe metropolitan region. Between 1850 and 1856,Reinhardt collected fish in Lagoa Santa (Lütken 2001).Comparisons between the historical and recent datashowed that at least 70% of the original fish fauna isnow extinct (Pompeu and Alves 2003). The reasonswere directly related to urbanization: the obstructionand canalization of the natural connection betweenLagoa Santa and the Rio das Velhas, the elimination of
18 POMPEU ET AL.
FIGURE 3. Richness and Shannon Diversity Index for fish and benthos along the Rio das Velhas main course, in the dryand wet seasons.
littoral (Cyperaceae) and submerged (Characeae) veg-etation, and the introduction of alien fish species.
Another important effect of urbanization on thebasin is regular fish kills, mainly in the beginning of therainy season (Alves et al. 2000). Heavy organic dis-charges from the MRBH accumulate in the river bot-tom during the dry season. At the beginning of thesummer/wet season, this material is suspended and wa-ter temperatures increase. Rapid decomposition of theorganic matter depletes dissolved oxygen, causing fre-quent fish kills. Recent radiotelemetry studies have shownthat Rio das Velhas is an important route for large mi-gratory species from São Francisco River (A. Godinho,Universidade Federal de Minas Gerais, personal com-munication). Annual kills of adults and burying of theeggs and larvae lead to annual decreases of resident fishpopulations and those that migrate from the Rio SãoFrancisco to spawn. However, our data indicate that themost severe effects of the MRBH urbanization on fishand benthos in the Rio das Velhas occur during thewinter/dry season. Some researchers (Bozzetti and Schulz
2004; B. C. T. Pinto and F. G. Araujo, UniversidadeFederal Rural do Rio de Janeiro, and R. M. Hughes,Oregon State University, unpublished data) concludedthe same for other rivers in southeastern Brazil, linkingthe effect to pollutant concentration and more efficientsampling during the dry season.
In aquatic environments, processes that determinestructural diversity are closely related to the fluvial re-gime, which determines depth, velocity, substrate types,and channel shape (Angermeier 1997). The fluvial re-gime also is linked to the seasonal flood cycle, whichaffects sediment, organic matter fluxes, and biomassproduction (Junk et al. 1989). In the tropics, many fishspecies use river floodplains for feeding, reproduction,and refuge (Agostinho and Zalewski 1996). Fragmen-tation and habitat simplification are broadly describedas the main threats to biodiversity conservation becausethey directly interfere with the rates of colonization andextinction (Kareiva et al. 1995) and are the main causesof fish species extinction in North America (Miller et al.1989). There are no dams in the Rio das Velhas main
19THE EFFECTS OF URBANIZATION ON BIODIVERSITY AND WATER QUALITY
TA
BL
E 2
. N
umbe
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ive
and
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20 POMPEU ET AL.
stem and no observed changes in its flow regime. Thisconnectivity with the Rio São Francisco system andtributaries in excellent condition, increase the rehabili-tation potential of the Rio das Velhas (Pompeu et al.2004).
In addition, there are 12 sewage treatment plantsalready installed within the MRBH and others are be-ing designed and built. The DRENURBS Project (En-vironmental Rehabilitation and Sanitation of Valleysand Natural Riverbeds of Belo Horizonte) is also beingimplemented. Its main goals are water course cleaning,sediment control, institutional reinforcement by BeloHorizonte City Hall, and integration of water resourceswith urban scenery.
An environmental monitoring program has be-gun for the Rio das Velhas as part of the ManuelzãoProject. Physical, chemical, and biological indicators arebeing used to: (1) determine the contribution of theRio das Velhas to the condition of the Rio São Fran-cisco; (2) identify point and diffuse pollution sourcesthroughout the basin; (3) assess aquatic ecosystem healthand environmental quality; and (4) monitor changes inwater quality due to sanitation interventions and sew-age treatment. The assessment and monitoring willemploy modified monitoring designs and indices ofbiotic integrity used by the USEPA’s EnvironmentalMonitoring and Assessment Program.
The objective of the Manuelzão Project is to re-turn the fishes to the Rio das Velhas. The project adoptsthe basin as a research, planning, and social mobiliza-tion unit. The basin perspective helps to integrate na-ture, history, environment and social relationships, andhuman health. Our data, collected as part of thisproject, contribute to the knowledge of freshwaterbiodiversity in the Rio das Velhas, which can be usefulfor Brazilian decision makers. We are using the Refer-ence Condition Approach (RCA, least disturbed sites)of Hughes (1995) and Bailey et al. (2004) for biologi-cal assessment in the Rio das Velhas basin. The RCAhas a number of key features that make it useful forour purposes: (1) It defines and quantifies ecosystemhealth; (2) it incorporates variation among healthyecosystems; and (3) it uses the deviation of a test sitefrom Reference Condition to measure the effect ofstressors on the ecosystem. We measure variability inbenthos and fishes among sites in “Reference Condi-tion” in four subbasins (Taquaraçú, Paraúna, Curi-mataí, and Itabirito). These reference subbasins areminimally exposed to human stressors such as effluentdischarges or land uses that often disturb ecosystems.We plan to elaborate, test, and validate an empiricalmodel to explain as much of the variability in the
reference site biota as possible, based on the environ-mental characteristics of the sites.
Acknowledgments
We are grateful to Bob Hughes, who invited us to writethis chapter and for his editorial suggestions. Also, wethank Sílvia Magalhães for her help on the map andproviding geographical information about the basin;Mark Bowen for suggestions on the manuscript; LuizFelipe Mascarenhas Horta for his help with the transla-tion; and Karina Moreyra, Juliana França, WanderFerreira, and Pablo Moreno for the water and benthossampling. We also thank Projeto Manuelzão paraRevitalização da Bacia do Rio das Velhas (UFMG),Fundo-Fundep de apoio acadêmico 1999, CNPq,FAPEMIG, CAPES, U.S. Fish & Wildlife Service, PadAward, Padi Foundation, and Fundação O Boticário deProteção à Natureza (grant No. 0472002) for the logis-tics and financial support.
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