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PARDINHO RIVER, RS, BRAZIL, USING EPILITHIC
DIATOM ASSEMBLAGES AND FAECAL
COLIFORMS AS BIOLOGICAL INDICATORS
E Lobo, D Bes, L Tudesque, L Ector
To cite this version:
E Lobo, D Bes, L Tudesque, L Ector. WATER QUALITY ASSESSMENT OF THE PARDINHO
RIVER, RS, BRAZIL, USING EPILITHIC DIATOM ASSEMBLAGES AND FAECAL COLIFORMS
AS BIOLOGICAL INDICATORS. Vie et Milieu / Life & Environment, Observatoire Océanologique
- Laboratoire Arago, 2004, pp.115-125. �hal-03218089�
WATER QUALITY ASSESSMENT OF THE PARDINHO RIVER, RS,
BRAZIL, USING EPILITHIC DIATOM ASSEMBLAGES
AND FAECAL COLIFORMS AS BIOLOGICAL INDICATORS
E. A. LOBO
a*, D. BES
a, L. TUDESQUE
b, L. ECTOR
ba
University of Santa Cruz do Sul, Laboratory of Limnology. P.P. O. Box 96.815-900, Santa Cruz do Sul, RS, Brazil
b
Centre de Recherche Public – Gabriel Lippmann, CREBS, 162a Avenue de la Faïencerie, L – 1511 Luxembourg
*
Author to whom correspondence should be addressed: lobo@unisc.br
WATER QUALITY ASSESSMENT BIOINDICATORS EPILITHIC DIATOMS FAECAL COLIFORMS ORGANIC POLLUTION PARDINHO RIVER, RS BRAZIL
ABSTRACT. – The aim of this study was to monitor water quality of Pardinho Ri-ver, located within the Pardinho River Hydrographical Basin, RS (State of Rio Grande do Sul), Brazil, measuring chemical and biological variables, particularly diatoms and faecal coliforms. From August 2001 to July 2002, seasonal water sam-ples for determination of chemical variables such as dissolved oxygen, biochemical oxygen demand (BOD5) and total phosphate were collected from five stations along
Pardinho River, and analysed following American Public Health Association (1992). The stations were located between the upper and the lower reaches of the ri-ver. Water quality assessment based on chemical variables was made according to the resolution nº 20 of CONAMA (National Environment Council) for the classifi-cation of Brazilian continental freshwaters. Diatom samples were collected at the same sampling sites, cleaned with sulphuric and hydrochloric acid and mounted in Naphrax. All specimens found in a number of transects across the prepared slides were identified and counted until a minimum of 400 valves was scored. The evalua-tion of water quality in terms of organic polluevalua-tion was made using the Saprobic Index (SI) of Pantle & Buck (1955), following the southern Brazilian diatom classi-fication proposed by Lobo et al. (2002). Water samples for determination of most probable number of faecal coliforms were taken at the same time and sampling sta-tions as benthic diatom, following American Public Health Association (1992). The bacteriological assessment of water samples was done again according to the reso-lution nº 20 of CONAMA. The results indicated that the water quality levels of the Pardinho River ranged from oligo/β-saprobic (slightly polluted) on station 1 (spring 2001 and autumn 2002) and station 2 (summer 2002), toα/polysaprobic (very hea-vily polluted) on station 5 (autumn 2002). In this station, Nitzschia palea and Sella-phora pupula were highly abundant in all samples. These species are recognised worldwide as very tolerant to organic pollution, and this was also confirmed for southern Brazilian running waters. It is important to point out that the system used in this study is the first developed for Brazilian rivers, that classified epilithic dia-toms based on their distribution patterns along an organic pollution gradient.The microbiological water quality of the Pardinho River does not meet minimum requi-rements for the safe use of water, such as bathing and fishing, according to the stan-dards for water uses established by CONAMA and by the Brazilian Ministry of Agriculture classification. EVALUATION DE LA QUALITÉ DE L’EAU BIOINDICATEURS DIATOMÉES ÉPILITHIQUES COLIFORMES FÉCAUX POLLUTION ORGANIQUE RIVIÈRE PARDINHO, RS BRÉSIL
RÉSUMÉ. – Le but de cette étude était de surveiller la qualité de l’eau de la rivière Pardinho, RS (Etat de Rio Grande do Sul), Brésil, en mesurant des variables chimi-ques et biologichimi-ques, en particulier les Diatomées et les coliformes fécaux. D’août 2001 à juillet 2002, des échantillons d’eau saisonniers pour la détermination de va-riables chimiques telles que l’oxygène dissous, la demande biochimique en oxy-gène (BOD5) et le phosphate total ont été récoltés dans 5 stations, réparties le long
de la Rivière Pardinho, et ont été analysés selon l’American Public Health Associa-tion (1992). Les staAssocia-tions étaient localisées entre les tronçons supérieurs et infé-rieurs de la rivière. L’évaluation de la qualité de l’eau basée sur des variables chimiques a été faite selon la résolution nº 20 du CONAMA (Conseil National de l’Environnement) pour la classification des eaux douces continentales brésiliennes. Des échantillons de Diatomées ont été récoltés aux mêmes stations, nettoyées avec de l’acide sulfurique et de l’acide chlorhydrique et montées au naphrax. Tous les spécimens trouvés dans un certain nombre de sections sur la préparation ont été
identifiés et comptés jusqu’à ce qu’un minimum de 400 valves ait été atteint. L’éva-luation de la qualité de l’eau en termes de pollution organique a été faite en utilisant l’Indice Saprobique (SI) de Pantle & Buck (1955), selon la classification proposée par Lobo et al. (2002) pour les Diatomées du Sud du Brésil. Des échantillons d’eau pour la détermination des coliformes fécaux ont été prélevés en même temps dans les mêmes stations que pour les Diatomées, selon l’American Public Health Asso-ciation (1992). L’évaluation bactériologique des échantillons d’eau a été faite en accord avec la résolution no20 du CONAMA. Les résultats ont montré que les ni-veaux de qualité de l’eau de la rivière Pardinho sont répartis depuis le niveau oli-go/β-saprobe (légèrement pollué) à la station 1 (printemps 2001 et automne 2002) et la station 2 (été 2002) jusqu’au niveauα/polysaprobe (très fortement pollué) à la station 5 (automne 2002). Dans cette station, Nitzschia palea et Sellaphora pupula étaient fortement abondants dans tous les échantillons. Ces espèces sont reconnues dans le monde entier comme étant très tolérantes à la pollution organique, ce qui a été aussi confirmé pour les eaux courantes du Sud du Brésil. Il est important de pré-ciser que le système utilisé dans cette étude est le premier développé pour les cours d’eau du Brésil, en classant les Diatomées épilithiques sur la base de leurs modèles de distribution le long d’un gradient organique de pollution. La qualité microbiolo-gique de l’eau du Pardinho ne répond pas aux exigences minimums pour un usage sans danger de l’eau, comme la baignade et la pêche, selon les normes standards pour les usages de l’eau établies par le CONAMA et le Ministère brésilien de la classification de l’Agriculture.
INTRODUCTION
Biological monitoring is considered to be one of the approaches for water quality evaluation, basi-cally due to two major arguments. Firstly, organ-isms exhibit integrated responses to their environ-ment, thus continual fluctuations of water quality, which might not be identified by intermittent phys-ical and chemphys-ical analyses, can be detected. Sec-ondly, if the aim is to maintain the diversity and health of biological communities, it is appropriate to monitor aquatic communities themselves rather than only abiotic factors. Furthermore, according to Round (1993), physical and chemical analytic methods complement biological ones, and together they comprise a base for correctly assessing the quality of running waters.
Among the aquatic communities, diatoms have been extensively used as indicator organisms, be-cause they do not need special treatment for preser-vation, the records are permanent, and the group shows a complete pollution spectrum, from taxa sensitive to pollution, indicating oligosaprobic conditions – clean waters, to most pollution toler-ant ones, indicating polysaprobic conditions – strongly polluted waters (Round 1993, Schoeman & Haworth 1986).
In Brazil, little attention has been paid to the use of diatoms for assessing water pollution. Only a few related studies have been carried out, mainly in the southern region (e.g., Lobo & Ben Da Costa 1997, Lobo & Bender 1998, Rodrigues & Lobo 2000, Lobo et al. 1995, 2002, Oliveira et al. 2001). With respect to environmental research in the
Pardinho River, Lobo & Ben Da Costa (1997) stud-ied 17 sampling stations along this river, applying physical, chemical and biological methods. Diatom community analysis was carried out in one station, where the organic pollution level varied from α -mesosaprobic (strongly polluted) to polysaprobic (excessively polluted). Lobo & Bender (1998) studied the suitability of saprobic systems used for the evaluation of river water quality, two devel-oped in Japan (Watanabe et al. 1988, Kobayasi & Mayama 1989) and one in Germany (Lange-Bertalot 1979), applied to strongly polluted waters in the Pardinho River.
Taking the above into account, the aim of this study was to monitor water quality of the Pardinho River, RS, from an integrated approach including both chemical (dissolved oxygen, biochemical oxy-gen demand and total phosphate) and biological variables (diatoms and faecal coliforms).
MATERIALS AND METHODS
The Pardinho River Hydrographical Basin is located roughly at the center of the State of Rio Grande do Sul. Part of the basin is in the denominated Depressão Cen-tral and part is in the Planalto Area, between coordinates 52o40’30’’ to 52o40’30’’ W and 29o14’30’’ to 29o52’30’’ S, occupying an approximate area of 1.075 Km2. The main watercourse, named the Pardinho River, with an extension of 105 km, has its highest alti-tude at 718 m, in the municipal district of Gramado Xa-vier, and its lowest altitude at 17 m, in the municipal district of Rio Pardo. The main water demand in this ba-sin is for irrigated rice, adding up 90% of the hydric
re-sources between December and February, exactly the period of river lowest discharge. Tobacco production is also an important agriculture activity, causing great en-vironmental impact due to the use of agrotoxics (Lobo & Putzke 2000). Around the lower reach of the Pardinho River, is situated the main municipal district of the re-gion, Santa Cruz do Sul. With a population of 107.632 inhabitants, a great part of their domestic waste enters the river without treatment therefore increasing its organic load. Noticeable, 93.5 % of the water consumed in Santa Cruz do Sul comes from the Pardinho River.
From August 2001 to July 2002, four seasonal field trips were carried out to collect samples of epilithic dia-toms from five stations along the Pardinho River (Fig. 1). The geographical coordinates are indicated in Table I. Also, water samples for determination of chemi-cal variables such as dissolved oxygen, biochemichemi-cal oxygen demand (BOD5) and total phosphate were
colle-cted and analysed following the American Public Health Association (1992).
Water quality assessment based on chemical variables was made according to Hamm’s (1969) classification of water quality, Branco & Rocha (1977) and the resolu-tion nº 20 of CONAMA (Naresolu-tional Environment Coun-cil) for Brazilian continental freshwater classification (CONAMA 1986) (Table II).
For qualitative and quantitative analyses of epilithic diatoms, the upper surface of 5 submerged stones of 10-15 cm in diameter were scrubbed off using a toothbrush and fixed with formalin, following the method of Ko-bayasi & Mayama (1982). Water depth at sampling loca-tions was of less than 30 cm. Diatom samples were cleaned with sulphuric and hydrochloric acid and moun-ted in Naphrax. All specimens found in a number of transects across the prepared slides were identified and counted until a minimum of 400 valves was scored (Pry-giel & Coste 2000). For microscopical evaluation a Zeiss Axioplan and a Leica DM-RB light microscopes were used. The taxonomic sources used were Krammer & Lange-Bertalot (1986, 1988, 1991a, b), Lange-Bertalot Fig. 1. Map of the study area showing the
location of the Pardinho River hydrogra-phical Basin (A), State of Rio Grande do Sul (B), Brazil (C).
(1993, 2000, 2001) and Simonsen (1987). To differen-tiate the abundant species, the criterion proposed by Lobo & Leigthon (1986) was used. The samples are sto-red in the Herbarium DIAT-UNISC, at the University of Santa Cruz do Sul, RS.
Based on biological analyses, the evaluation of water quality in terms of organic pollution was made using the Saprobic Index of Pantle & Buck (1955), following the Southern Brazilian diatom classification proposed by Lobo et al. (2002). The relationship between Pantle and Buck’s Saprobic Index (SI) and the water quality is gi-ven in Table III.
In order to evaluate water quality based on microbio-logical indicators, water samples for determination of most probable number of faecal coliforms were taken at the same time and sampling stations as diatom sampling. Sampling techniques followed those given by American Public Health Association (1992). The bacteriological assessment of water samples was done according to CONAMA no20 resolution and the classification no101 of 11 August 1993, by the Brazilian Ministry of Agricul-ture. This classification established the maximum num-ber of coliforms for drinking water, as less than one organism for 100 mL. For bathing waters the limit num-ber of coliforms is of 1000 organisms/100 mL, whereas for supply waters before treatment the limit is of 4000 organisms/100 mL.
RESULTS AND DISCUSSION
Chemical environment
Table IV shows seasonal results of chemical analyses at each sampling station, from winter 2001 to autumn 2002. The rating of water quality in the Pardinho River, using the CONAMA resolu-tion, is given in figure 2A, B. These use values of BOD5 and total phosphate concentration, respec-tively.
Regarding BOD5, the five sampling stations in all periods of the year could be fitted in Class 1, ac-cording to CONAMA (Fig. 2A), corresponding to a good water quality class. The exceptions were sta-tion 3 in winter, stasta-tion 4 in summer and stasta-tion 5 in winter and summer.
However, values of total phosphate in all the sampling stations and periods of the year were above the recommended limit levels for waters free of contamination, 0.03 mg L–1 (P), according to
Branco & Rocha (1997). According to the classifi-cation of CONAMA, the recorded values of total
Table I. (top). Geographical coordinates from five sampling stations distributed along the Pardinho River, RS, Brazil. Table II (bottom). Abstract of the continental Brazilian freshwaters classification, according to the resolution number 20 of 18 June 1986, by CONAMA (Brazilian National Environment Council).
phosphate were, in all sampling sites and periods of the year, above 0.025 mg L–1 (P), which
corre-sponds to standards established by CONAMA for waters of Class 1 (Fig. 2B). In this context, the sampling stations along the Pardinho River could be fitted in Classes 2 to 4, since there is not a limit differentiating these classes established by
CONAMA. These results indicated that the
Pardinho River is undergoing an eutrophication process, supporting the results obtained in the same watercourse by Lobo & Ben Da Costa (1997).
It should be noted that the phosphate standards established by CONAMA for classification of
wa-Table III (top). Relationships between the Saprobic Index (SI) of Pantle & Buck (1955) and water quality levels, accor-ding to the classification proposed by Hamm (1969).
Table IV (bottom). Dissolved oxygen (DO), biochemical oxygen demand (BDO5), total phosphate (P) and faecal
coli-forms (Faec. Col.) on five sampling stations located along Pardinho River, RS, Brazil.
Fig. 2. Water quality assessment of Pardinho River, RS, Brazil, following the water quality classification esta-blished by CONAMA 20/86. A. Biochemical oxygen de-mand. B. Total phosphate.
ter quality has been put into question. For example, Leite et al. (1994) mentioned that for water bodies in Rio Grande do Sul State, Brazil, background le-vels of phosphate are generally as high as the CONAMA standards for waters of class 1. Moni-toring studies carried out by FEPAM (State Pro-tecting Environmental Issues Foundation) in rivers of the Guaíba hydrographical basin and in coastal lagoons of Rio Grande do Sul State, revealed that
phosphate background levels in these systems were also above the limits recommended by CONAMA. That was so even where anthropogenic influence was not significant. These results indicate that the CONAMA standards are not adequate and highly restrictive.
According to Train (1979), the greatest danger of the presence of high levels of phosphate in the
Table V. Relative abundance (%) of diatom species identified in five sampling stations distributed along the Pardinho River, RS, during Winter (WI), Spring (SP), Summer (SU) and Autumn (AU). The saprobic values (s) as well as the Saprobic Index (SI), following Lobo et al. (2002), are given. The abundant species are highlighted.
water is not its toxicity but its potential to originate and speed up the eutrophication process. Moreover, in order to prevent the eutrophication process from starting, phosphate concentrations should not ex-ceed 0.025 mg L–1 (P) in lakes and reservoirs, 0.050 mg L–1(P) in streams that flow into a lentic system and 0.100 mg L–1(P) in running waters not flowing directly into lakes and reservoirs, as it is the case for the Pardinho River.
Thus, considering a phosphate concentration of 0.100 mg L–1(P) as an upper limit in order to avoid
the eutrophication problem, all values found in the Pardinho River in the present study are equal to or above the mentioned limit value. These results con-firmed the eutrophication process detected. Biological composition
With regards to the epilithic diatom community, 126 taxa were identified in five sampling stations along the Pardinho River, RS, down to specific and infra-specific level. Table V shows the relative abundances (%) of diatom species identified during the whole study period, including the species saprobic value (s) according to Lobo et al. (2002). 49 taxa were considered abundant, according to the criterion proposed by Lobo & Leigthon (1986).
The water quality assessment of the Pardinho River using Pantle & Buck’s Saprobic Index (Pantle & Buck 1955), following the Southern
Bra-zilian diatom classification proposed by Lobo et al. (2002), is shown in figure 3.
The results indicated that water quality levels at the sampling stations varied from oligo/β-saprobic (lightly polluted) in spring and autumn, on station 1, located in the upper reach of the Pardinho River, and station 2, in summer, up to α/polysaprobic (very heavily polluted), in summer on station 5, lo-cated in the lower reach. Indeed, figure 3 shows a gradual decrease in water quality, from good qual-ity levels towards the upper reach (station 1) to very heavily polluted ones towards the lower reach (station 5).
Station 1 presented the lowest organic pollution indices, varying from oligo/β-saprobic (lightly pol-luted) in spring and autumn to β/α-mesosaprobic (critically polluted) in winter. The index obtained in spring and autumn was mainly a result of the great abundance of the species Nupela sp. and
Brachysira brebissonii, both belonging to group C,
species sensitive to organic pollution. Summer and winter were characterised by the high predomi-nance of species typical of group B, species toler-ant to organic pollution.
Station 2 presented evident seasonal differences, since the indices varied from α-mesosaprobic (strongly polluted), in winter and spring, to oligo/β-saprobic, in summer andβ/α-mesosaprobic in autumn. In this sampling station, the most abun-dant species were Amphora montana (group B) in winter, Nitzschia palea (group A) in winter and
Fig. 3. Top, water quality assessment of Par-dinho River, RS, using Pantle & Buck’s Sapro-bic Index (1955), based on the diatom classification for southern Brazilian rivers pro-posed by Lobo et al. (2002). Bottom, water quality assessment of Pardinho River, RS, Brazil, using faecal coliforms, following the water quality classification established by CONAMA 20/86.
spring, Nupela sp. (group C) in summer and
Cocconeis placentula var. placentula (group B), Geissleria aikenensis (group B), and Gomphonema parvulum (group B) in autumn.
On station 3, the indices varied from β -mesosaprobic (moderately polluted) in spring and summer to α-mesosaprobic in winter, registered β/α-mesosaprobic in autumn. In winter, the index was higher since all abundant species belonged to
group A and B, such as Navicula gregaria (group B, with 19.8%) and Gomphonema pseudoaugur (group A, 5.5%). In spring, the abundance of
Nupela sp. (64.4%) from group C, caused the index
to decrease. In summer, the index remained low be-cause the abundances of species from group C (37.2%), such as Placoneis disparilis, Planothidium
frequentissimum and Pleurosira laevis. In autumn,
the index increased due to the abundance of groups
Fig. 4. Some abundant diatoms species in Pardinho River, RS, Brazil: 1. Cocconeis placentula var. euglypta; 2. Cocco-neis placentula var. placentula; 3. PlacoCocco-neis disparilis; 4-5. Sellaphora pupula; 6. Nitzschia palea; 7-8. Brachysira brebissonii; 9-10. Gomphonema parvulum; 11-12. Amphora montana; 13. Geissleria aikenensis; 14. Navicula rostella-ta; 15-16. Nupela sp.; 17-18. Achnanthes exigua var. constricrostella-ta; 19. Nitzschia amphibia.
A and B species (49%), such as Navicula rostellata (8.2%) and Nitzschia amphibia (5.8%).
The organic pollution levels at station 4 varied fromβ/α-mesosaprobic, in spring, summer and au-tumn to α-mesosaprobic in winter. Cocconeis
placentula var. placentula, which belongs to group
B, was highly abundant in spring (24.5%) and in
summer (11%). Cocconeis placentula var.
euglypta, also belonging to group B, was abundant
in autumn with 10.0%, along with Navicula
rostellata (8.7%) and Nitzschia amphibia (9.6%).
In winter 93.8% of the abundant species were fitted in groups A and B, such as Gomphonema parvulum (28.2%), Nitzschia palea (9.2%) and Geissleria
aikenensis (8.5%).
Station 5 showed the highest organic pollution indices, varied fromβ/α-mesosaprobic in winter to polysaprobic (very heavily polluted) in summer (α -mesosaprobic in spring and autumn). This was due to the fact that in all samples from this station the species Nitzschia palea and Sellaphora pupula were highly abundant, from 12% in winter to 65.2% in summer and 3.5% in winter to 9.5% in spring, respectively. These species are recognised worldwide as species very tolerant to organic pol-lution, according to Lange-Bertalot (1979), Kobayasi & Mayama (1989) and Watanabe et al. (1988). This was also confirmed for southern Bra-zilian running waters by Lobo et al. (2002).
Ligth microscopy photographs for all the taxa mentioned in the above biological composition dis-cussion are shown in Fig. 4.
The biological analyses indicated that the major-ity of diatom species belonged to differential groups A and B of the system proposed by Lobo et
al. (2002). Species included in these groups are
characteristic of waters where BOD5 values are higher than 13 mg L–1 for group A and range
be-tween 4 and 13 mg L–1 for group B, indicating
α/polysaprobic and α-mesosaprobic levels, respec-tively. This classification, however, does not agree with BOD5 values found in the present work that ranged from 1.0 to 5.7 mg L–1. These values
indi-cated conditions from oligosaprobic (very low pol-lution) up to β/α-mesosaprobic, according to the classification of Hamm (1969).
In this context, it is important to point out that the saprobic system proposed by Lobo et al. (2002) was developed for the assessment of organic pollu-tion, and uses BOD5 as a base, not considering the effects of eutrophication on biological communi-ties. The high phosphate concentrations found in the Pardinho River, do indeed, confirm the eutrophication process found for this lotic system. Thus, these results confirmed the hypothesis of Rodrigues & Lobo (2000) which postulated that the response of the diatom community to water pollu-tion in lotic systems of Southern Brazil is due to the interaction of factors characterising processes
of eutrophication and organic pollution. This hy-pothesis was confirmed later by Oliveira et al. (2001), for lotic systems of Sampaio Stream, Rio Grande do Sul State.
Results of the most probable numbers of faecal coliforms are shown in Table IV and in Fig. 3. With the exception of sampling station 1, all the re-maining sampling stations were, for at least one pe-riod of the year, included in class 4 by CONAMA. Sampling station 5, for instance, was included in CONAMA class 4 in winter, spring and summer.
The most probable number of faecal coliforms showed a significant seasonal variation of mean values. These ranged from 1.406 ± 1.143 NMP 100mL–1(C.V. 81,3%) in autumn 2002, class 3 by
CONAMA to 17.994±29.440 NMP 100mL–1(C.V.
163,6%) in winter 2001, class 4 by CONAMA. In fact, 50% of the samples could be included in classes 3 (20%) and 4 (30%) by CONAMA, signifi-cantly reducing the uses of Pardinho River waters, particularly for human consumption. Waters of class 4 should be used only for navigation, land-scape improvement, and for less demanding uses. This is, indeed, a public health issue, since in Santa Cruz do Sul 95% of the supply water is originated from the Pardinho River. Moreover, potential for tourism in the region, particularly leisure activities involving direct contact with water, such as bath-ing and fishbath-ing, can be heavily compromised, since microbiological water quality does not meet mini-mum requirements for the safe use of the water sys-tems, according to the standards for water uses es-tablished by CONAMA, resolution number 20, and by the Brazilian Ministry of Agriculture classifica-tion.
ACKNOWLEDGEMENTS. – We thank the Public Re-search Center-Gabriel Lippmann for providing a training course on diatom taxonomy; Brazilian National Council for Research and Development (CNPq) for an undergra-duate studentship. Special thanks go to M A Oliveira, G Hermany and C E Wetzel for valuable contributions.
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Reçu le 10 septembre 2003; received September 10, 2003 Accepté le 7 avril 2004; accepted April 7, 2004
