COMPUTER AIDE BIOMONITORING OF STREAMS IN THE NORTHEAST OF THE
STATE OF RIO GRANDE DO SUL, BRAZIL.
Rosane Lanzer1 , Alois Schäfer1
1
Departamento de Ciências Biológicas – Instituto de Biotecnologia – Universidade de Caxias do
Sul – Caixa Postal 1352 – CEP 95020-972 -Caxias do Sul – RS.
aschaefe1@ucs.br
rlanzer@ucs.br
Abstract: Computer Aided Biomonitoring of Streams in the Northeast of the Rio Grande do Sul,
Brazil.
Computer aided biomonitoring of river basins consists in generating and using bioindicator
information of benthonic macroinvertebrates, the physical and chemical characteristics of water
and the spatial characterization of the habitat, based on storage, representation and crossmatching of these data, enabled by Geographic Information Systems (GIS). In Brazil there is no
standard method for using bioindicators in surface waters. The computer aided biomonitoring of
stream water quality in the northeast of the state of Rio Grande do Sul began in 2001. The study
area belongs to the Taquari-Antas and Caí river basins. The biotic indexes used were Biological
Monitoring Working Party (BMWP) and Average Score Per Taxon (ASPT). The physical and
chemical characteristics and organic pollution levels were determined by the Chemical Index
(IC). The 1:50000 topographic maps of the study area were digitized and geocoded in UTM. One
of the objectives of the study was to detect processes of self purification. Along the Rio Leão, a
capacity for self-purification is detected, with increased richness of taxa and improved water
quality which, according to BMWP, reaches class II before flowing into the Antas River. The
other results presented refer to applying and comparing different water quality indexes. In the
streams of the study area, BMWP is very closely related to the richness of taxa. ASPT and
BMWP show the same tendency of indication, but few divergences are observed. The richness of
benthonic macroinvertebrate fauna is not significantly related to the chemical characteristics of the
streams. The
ASPT has proved better correlated to the stress gradient in streams than BMWP.
Therefore, in the present study, ASPT is the most appropriate biological index to indicate the
water quality of rivers and streams in the northeast of the state of Rio Grande do Sul.
Keywords: Biomonitoring, GIS, benthic macroinvertebrates, Biological Indexes, lotic waters.
Resumo: Biomonitoramento Informatizado de Arroios no Nordeste da Estado do Rio Grande do
Sul, Brasil.
O Biomonitoramento de bacias hidrográficas consiste na utilização da bioindicação de
macroinvertebrados bentônicos, das características físicas e químicas da água e caracterizações
espaciais do habitat, baseada no armazenamento, na representação e no cruzamento destes dados,
dentro de um Sistema de Informação Geográfica (SIG). No Brasil não existe um sistema
padronizado de utilização de bioindicadores em águas correntes. O biomonitoramento
informatizado da qualidade da água de águas correntes no nordeste do Estado do Rio Grande do
Sul começou em 2001. A área de estudo pertence às bacias hidrográficas Taquari-Antas e Caí. Os
índices biológicos aplicados foram o Biological Monitoring Working Party (BMWP) e Average
Score per Taxon (ASPT). As características físicas e químicas da água e os níveis da poluição
orgânica foram determinados pelo Índice Químico (IQ). Cartas topográficas, escala 1:50.000,
foram digitalizadas e georeferenciadas em UTM. Um dos objetivos do estudo foi a detecção de
processos de autodepuração. Ao longo do Rio Leão, a capacidade de autodepuração foi detectada
através do aumento da riqueza de táxons e o BMWP que alcança classe II antes da
desembocadura no Rio das Antas. Os outros resultados apresentados se referem à aplicação e
comparação de diferentes índices de qualidade da água. Nos arroios na área de estudo, o BMWP
está muito estreitamente relacionado com o número de táxons. ASPT e BMWP mostram a mesma
tendência de indicação, mas algumas divergências foram observadas. A riqueza da fauna de
macroinvertebrados bentônicos não está significativamente relacionada com a química da água
dos arroios. O ASPT apresenta uma melhor relação com o gradiente de estresse nas águas
correntes do que o BMWP. Nos rios e arroios no nordeste do Rio Grande do Sul, o ASPT
mostrou-se o índice biológico mais adequado para a avaliação biológica da qualidade da água.
Introduction
Computer aided biomonitoring of river basins consists in generating and using
bioindicator information of benthic macroinvertebrates, the physical and chemical characteristics
of water and the spatial characterization of the habitat, based on storage, representation and crossmatching of these data, enabled by Geographic Information Systems (GIS). These are computer
systems used to store, analyze and manipulate geocoded data, i.e., data that represent objects and
phenomena in which geographic location is an inherent characteristic of the information and
essential to analyze it (Aronoff, 1989). GIS have powerful visual representation and management
tools for descriptive data, both spatial and statistical, and can process and monitor different types
of resources in many different areas. They can be used in research that involves different fields (
Xavier da Silva & Zaidan, 2004).
In order to enable access, manipulation and updating of available data, a GIS must
basically include a digital cartographic set connected to a Managed Data Base System, allowing
statistical processing, advanced interpretation and visualization of geocoded data (Sell & Schäfer,
2002).
According to Buss et al. (2003), biomonitoring is the systematic use of the responses of
living organisms to evaluate changes in the environment, generally due to anthropic action.
Systems to evaluate water quality using bioindicators are widely used in Europe (AQEM) and in
USA (USEPA). In Brazil there is no standard method of using bioindicators to determine water
quality nor in water monitoring. Recently were developed research programs using
macroinvertebrates as bioindicators such as the Biological Monitoring Working Party (BMWP),
Average Score Per Taxon (ASPT), EPT (Ephemeroptera, Plecoptera e Trichoptera) and Trent
Biotic Index (TBI), which employ higher taxonomic levels and are useful in regions where
aquatic fauna is not yet well known (Oliveira et al., 1997; Junqueira & Campos, 1998; Silva et
al., 2005; Crisci-Bispo et al., 2007).
Computer aided biomonitoring of stream water quality in the northeast of the state of Rio
Grande do Sul began in 2001, performing an inventory of benthic macroinvertebrates, developing
a system to evaluate the ecological status of rivers and steams based on the bioindication of these
organisms, on physical and chemical analysis of water, and on the spatial characterization of the
habitat, associated with the implementation and maintenance of an environmental information
system, as a regional contribution to establish a standard methodology for ecological evaluation
of surface waters in Brazil. The current study presents some examples of applying this type of
biomonitoring, and it discusses the relationship between chemical and biological water quality
indexes.
Material and Method
Study area
The study area is located in the region called Nordeste Gaúcho (Northeast of Rio Grande
do Sul) (geocode IBGE 4302) and it belongs to the Taquari-Antas and Caí river basins, in the
Guaíba hydrographic region. The sample sites of the study are located in the following
municipalities: 1- Ipê; 2 - Antônio Prado; 3 - Caxias do Sul; 4 - São Francisco de Paula; 5 Cambará do Sul; 6 – Canela; 7 – Itati and 8 - Três Forquilhas (Tab. I and Fig. 1).
In Leão River, the purpose of the study was to evaluate the self-purification capacity of the
river after receiving the discharges of the municipalities of Ipê and Antônio Prado, using
biological indexes based on macroinvertebrates and Chemical Index of Bach (1986).
Collecting benthic macroinvertebrates and biotic indexes.
Macroinvertebrates samples were collected using manual capture with a 30
minute/collector effort and hand net with a 25cm X 25cm opening and 0.5 mm mesh. The
samples were fixed in 80% ethanol and preserved in 70% glycerinated ethanol. After identifying
and counting taxa, classification was performed according to the levels of abundance (Ludwig,
1989). The samples were included in the computer aided scientific collection of
macroinvertebrates (ZUCS – Macroinvertebrate Collection of the Limnology Sector at the
Biotecnology Institute, University of Caxias do Sul) linked to the Managed Data Base System.
The biotic indexes used were Biological Monitoring Working Party - BMWP and Average Score
Per Taxon – ASPT, based on family scores of sensitivity and resistance to pollution. BMWP
water quality classification follows the color scheme of water quality classes used in cartographic
representations, according to Alba-Tercedor & Sánchez-Ortega (1988) and Rico et al. (1992). The
ASPT varies from 0 (worse quality) to 10 (best quality).
Water analysis and habitat structure
The physical and chemical characteristics and organic pollution levels were determined
by the Chemical Index – CI (Bach, 1986) that includes eight parameters: oxygen saturation,
water temperature, pH, electric conductivity, biochemical oxygen demand (BOD5), soluble
reactive phosphate, ammoniac nitrogen and nitrate. The CI varies from 0 (worse quality, class
IV) to 100 (best quality, class I).
The habitat characteristics were described based on the type of substrate, presence of
aquatic vegetation, type of flux, width and depth of the area sampled and riparian vegetation.
Statistical analysis
The statistical methods used were linear simple regression analysis between the chemical
index and biological indexes. Data from rivers and streams in Cambará do Sul and São Francisco
de Paula were used for these calculations. Program SPSS 14.0 was employed.
Database
The Managed Database System was developed using Microsoft Access software (Fig. 2).
It provides automatic calculation of the biological indexes (BMWP and ASPT) and CI, as well as
information about each index. Furthermore, it includes the entire macroinvertebrates scientific
collection, organized in the form of geocoded lots of identified taxonomic units.
Geographic Information System
The 1:50,000 topographic maps of the study area were digitized and geocoded in the UTM
system. Positioning information was obtained in UTM coordinates (Universal Transverse
Mercator), SAD 69 datum, by using a GARMIM GPS receptor.
The hydraulic network and contour lines were digitized, and a Digital Elevation Model
was created through a TIN (Triangulated Irregular Network). The thematic maps were obtained
by geoprocessing the geocoded attributes, stored in the Managed Database System and related to
the Geographic Information System based on programs IDRISI 3.2 and ARCVIEW 3.2.
Results and Discussion
The Northeast Region of Rio Grande do Sul is ecologically very relevant, since it has a
large number of springs and small streams. Water reservoirs to supply the population basically
depend on these small watercourses. The preservation and monitoring of these ecosystems are
very important in this area which, according to the Ministry of Environment (MMA, 2000), is
highly relevant from the biological point of view.
The community of benthic macroinvertebrates is a major component of a river and creek
community, and it is essentially important for nutrient dynamics, transformation of organic matter
and energy flux (Rosenberg & Resh, 1993; Callisto & Esteves, 1995). The use of biodiversity as a
tool to monitor habitat quality is a very important approach for holistic evaluations, mainly
because many organisms are sensitive to anthropic impacts and may indicate not only the
momentary situation, but also the history of the environment (Hellawell, 1986; Callisto et al.,
2001).
Despite the importance of the biological indication to evaluate the ecological status of
surface waters in many countries, in Brazil its use is still very incipient. Indexes such as BMWP
have been applied, with regional adaptations (Junqueira et al., 2000) based on selection of
indicator taxa for organic pollution levels and other impacts, such as done in Spain (Solimini et
al., 2000) and in Thailand (Mustow, 2002). For this purpose, it is necessary to perform a broad
survey of several distinct environmental characteristics, i.e., of the different levels of organic
pollution, identified by chemical analyses or by applying a chemical quality index of water,
besides the general characteristics of the habitat, such as flux, presence of vegetation and
heterogeneity of the substrate, which are important factors to be considered, because they are
directly related to biodiversity (Stark et al., 2001; Moretti & Callisto, 2005; Bispo & Oliveira,
2007).
The quantity and heterogeneity of the generated data makes it necessary to implement a
database system and mechanisms that allow cross-matching and interpretation of them. The
structure of the information needed for research was conceived through a hierarchical diagram,
where all classes of data derived from biomonitoring are organized at the storage and baserelations level.
The data system is a unified base for all informative categories of collections and
analyses, enabling the cross-relating of information. The focal point of the system is the
geocoding of all the information in reference to the sampling sites (Fig. 2). The physical and
chemical measures are related directly to the biological ones. The tabulated information has a
one-to-one relationship (a collection for a set of physicochemical data, for instance) or one-tomany (a collection for several biological records, i.e., each different specimen identified).
The data base contains data from 155 samplings performed in the northeast region of Rio
Grande do Sul, from September 2001 to April 2007. Most of the sites studied are characterized by
environments that are not impacted. Therefore, these sites can be used as base line for
determining different degrees of ecological integrity. The ecological integrity of a water body is
defined by comparing the composition of the biological community to sites of reference which
present conditions similar to the natural state (Sandin & Hering, 2005).
The biodiversity found in the study area is high, and the most abundant taxa were aquatic
insects
represented
(Hydropsychidae,
by
Diptera
(Chironomidae,
Polycentropodidae,
Simullidae,
Calamoceratidae,
Tipulidae),
Limnephilidae),
Trichoptera
Ephemeroptera
(Caenidae, Baetidae, Leptophlebiidae), Odonata (Libellulidae, Aeshinidae) and Plecoptera
(Perlidae e Gripopterygidae).
One of the objectives of the study was to detect processes of self purification using
macroinvertebrate communities, chemical conditions of the water body and river morphology.
The Leão River has a longitudinal profile with a high slope (Fig. 3). Before passing through the
cities of Ipê and Antonio Prado, the water quality determined by Chemical Index was class II-III,
which reflects anthropic inferences, shown mainly by changes on the banks and riverbed. After
receiving the organic discharges from both cities, Leão River deteriorates to class III (Fig. 4 a,b).
According to the physical and chemical criteria, Leão River shows a high capacity of selfpurification, and before it flows into the Antas River it reaches class I. This phenomenon can be
explained by the high aeration rate due to the turbulence of the water body.
At the three points sampled in this river, 32 taxa were recorded, and 1580 individuals
were counted, with a higher number of Trichoptera families, but with a higher abundance of
Diptera. According to Roy et al. (2003), the richness of taxa and especially of Ephemeroptera,
Plecoptera and Trichoptera, generally known as EPT, is highly correlated with environmental
variables and has the advantage of being easily calculated and applied at all sites. Moretti &
Callisto (2005), studying the macroinvertebrates in the middle Doce River watershed, observed
no plecopterans in the studied reaches and suggests that these organisms are not tolerating these
conditions, moreover that the low diversity of habitats affect the distribution of this taxon.
Ephemeroptera, Plecoptera and Trichoptera form a rich community in low and medium order
cobble streams and occur mainly in clean and well-oxygenated waters (Bispo & Oliveria, 2007).
The absence of Plecoptera in the sample sites in Leão River indicates altered environmental
quality, where the most sensitive taxa tend to disappear.
On the other hand, the biological evaluation shows a lower quality than the Chemical
Index (Fig. 4b). The richness of taxa at the site closest to the spring was 19, and Baetidae,
Simulidae and Chironomidae were the most abundant families. The BMWP evaluated the stream
section as water quality class III, which is related to changes in the habitat structure. After
receiving the discharges, a reduction is found in the richness of taxa, with a predominance of
Glossiphoniidae, Physidae and Chironomidae, and a decline in the water quality to class IV.
Chironomid (mainly Chironomus), together with Oligochaeta and Hirudinea, predominate in
habitats with low dissolved oxygen and high inputs of organic sewage in the water (Fagundes &
Shimizu, 1997). The reduction of biodiversity due to organic enrichment leads to an increasing in
the abundance of organisms that are best adapted to these ecological conditions. The benthic
macroinvertebrates are different from each other, as their sensibility to organic pollution, ranging
from organisms typical of clean environments or good water quality (Plecoptera larvae and some
Ephemeroptera and Trichoptera larvae) to resistant organisms (Chironomidae larvae and
Oligochaeta). Along the river, a capacity for self-purification is detected; with increased richness
of taxa, and improved water quality which, according to BMWP reaches class II before flowing
into the Antas River (Fig 4b).
The congruencies and differences found between biological indication and chemistry may
help achieve a more accurate adaptation of biological methods to water quality evaluations.
The other results presented of this study refer to applying and comparing the different
indexes, as in the surveys performed in Cambará do Sul and São Francisco de Paula. Most sites,
according to BMWP, are in quality class I and II (Alba-Tercedor & Sanchez-Ortega, 1988) which
is confirmed by the CI that varies among I, I-II and II. The ASPT, at the same sites, varied from
5.8 to 7.5. Tio Juca stream presents a CI that classifies it as good water quality, but, according to
BMWP, it is class III. In this stream there is a reduction of number of taxa, but the values
obtained by ASPT (5.7 to 6.4) are similar to most other sites. The Santana River was included in
classes I and II at one of the sampling sites ( X – 593368 Y- 6796267). An extreme reduction in
taxa richness is observed at the site (X-591725 Y-6796540) due to effluents discharged from a
cellulose plant, causing the impoverishment of macroinvertebrate community. The reduced water
quality is shown both by the biotic indexes and by CI. The BMWP is low at naturally nutrientpoor sites and also at sites that are highly polluted by organic substances.
BMWP is closely related to the richness of taxa, which is expected, considering that the
index is calculated by the sum of scores of indicating families, and therefore increases with the
number of present indicator families’ (Tab II and Fig. 5). The use of high taxonomic levels are
useful in regions where aquatic fauna is not yet well known, represent a low-cost method to asses
water quality and adequate to monitoring water quality (Oliveira et al., 1997; Moretti & Callisto,
2005; Crisci-Bispo et al., 2007). In this study, the high correlation found between the taxa
richness and BMWP is even further accounted for by the occurrence of a large number of families
indicating good water quality, i.e., a homogeneous indication. Therefore, 83,1% of variance of
BMWP is explained by the taxa richness, the highest correlation between the indexes used in this
study (Fig. 5).
The same BMWP values may be composed by few families indicating good quality, or by
a high number of medium and low score families, which is corrected by ASPT, the mean value of
BMWP indication which is, therefore, independent of the number of indicating families. Since
this is an evaluation with the same criteria base, ASPT and BMWP show a tendency that
commonly occurs in the classification of highly polluted sites, but a few divergences are observed
in the indication (Fig. 6), expressed by the explanation of variance of only 56 % of ASPT by
BMWP (Table II). The richness of benthic macroinvertebrate fauna is not significantly related to
the chemical characteristics of the streams (only 16,1 % of variance of BMWP is explained by IC,
Table II).
The number of taxa depends rather on other environmental factors which are related to
spatial and morphological variables of the habitat, such as available substrate, flux, presence of
aquatic plants and size of the water body. The CI doesn’t explain the variance of the taxa richness
(r² = 0,045). Environmental heterogeneity has been mentioned as a determining factor of
organism diversity in lotic environments (Bispo et al., 2007).
The CI accounts for only 16,1% of BMWP variance, but for 43,7 % of the ASPT variance
(Table II). The ASPT has proved better correlated to the stress gradient in streams than BMWP, a
result with agree with the studies of Sandin & Hering (2004). Considering these relationship
between indexes, in the present study, ASPT is the most appropriate biological index to indicate
the water quality of rivers and streams in the Serra Gaúcha.
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