Benthic macroinvertebrates as bioindicators of water quality in Billings Reservoir fishing sites ( SP , Brazil )

1Instituto de Pesca do Estado de São Paulo – IP, Secretaria da Agricultura e Abastecimento do Estado de São Paulo – SAA, Agência Paulista de Tecnologia do Agronegócio – APTA, Avenida Francisco Matarazzo, 455, Barra Funda, CEP 05001-900, São Paulo, SP, Brazil 2Departamento de Ecologia, Instituto de Biociências, Universidade de São Paulo – USP, Rua do Matão, 321, travessa 14, Cidade Universitária, CEP 05508-090, São Paulo, SP, Brazil *e-mail: ricardogargiulo@gmail.com

Palavras-chave: zoobentos; impacto ambiental; eutrofização; pesca artesanal.and abundant animals, most have well-known ecological characteristics, they are sessile or have limited mobility and therefore are representative of local conditions, and they have the advantage of characterizing the water quality not only at the moment of sampling but also by reflecting their position over a longer period of time (Moreno & Callisto, 2005).The analysis of the structure and distribution of the benthic community is an important ecological tool for describing spatial and temporal changes (Callisto et al., 1998;Leal & Esteves, 1999).According to CETESB (2013), by inhabiting the sediment and being sensitive to disturbance in the aquatic environment, the benthic community is considered a good indicator of the ecological quality of water bodies.Some studies (Pamplin et al., 2006;Carew et al., 2007;Jorcin & Nogueira, 2008;Buss & Vitorino, 2010;Cortelezzi et al., 2011;Miserendino et al., 2011) have improved the knowledge of the bio-indicator potential of benthic macroinvertebrates.
The main objective of this study was to use the benthic macroinvertebrate community as a tool in the assessment of the water quality at fishing sites in Billings Reservoir (SP).

Study area
The Billings Reservoir has an area of approximately 120 km 2 and has a complex and dendritic format, with a long and narrow central body with eight branches.It has a maximum depth of approximately 18 meters, an average volume of 646,841×10 6 m 3 , an average flow of 8.75 m 3 •s -1 and an approximate water retention time of 720 days (CETESB, 2012(CETESB, , 2013)).
The sampling sites (Figure 1) were selected in the areas with the highest intensity of fishing activity.Information about these areas was obtained from the community of traditional fishermen through reports obtained during meetings at Capatazia Z1, São Bernardo do Campo, and data collected by Alves da Silva et al. (2009).According to the Brazilian legislation of São Paulo State (ALESP, 1977 decree #10775) these sites are classified as freshwater of class of use 2, which indicates they are used for fishing or the growing of organisms for intensive consumption purposes.
-Sampling site 1 -P1 (S 23°49'54.0";W 46°38'26.9") is located in the Taquacetuba branch close to the central body of the reservoir, which is an area with good preservation of the Atlantic Forest in its surroundings along with some agricultural areas because the forming region of the Taquacetuba River occurs in a location with several protected areas.Water collection for transposition into the Guarapiranga Reservoir for public supply purposes occurs in the Taquacetuba branch.
-Sampling site 2 -P2 (S 23°46'01.0";W 46°37'37.7") is located in the Alvarenga region, an area with the total removal of the Atlantic Forest and great urbanization in its surroundings.This area was chosen because, according to the fishermen, the fish obtained there had unpleasant odor and taste.Thus, it would be possible to infer the effects of the interference of water quality on fish quality.Among the sampling sites, P2 is the closest to the pumping area of the water from the Pinheiros River.
-Sampling site 3 -P3 (S 23°48'53.2";W 46°32'94.7") is located close to Biguás Island, which is located in the central body of the reservoir close to the fishing colony and the João Basso ferryboat and is an area with Atlantic Forest and low urbanization in its surroundings

Sampling and data analysis
From April 2012 to March 2013, water and sediment (zoobenthos) samples were collected monthly from three sampling sites located at least 10 meters from the banks.The water was collected 0.5 meters from the bottom using Van Dorn bottles for the analysis of total nitrogen (TN) and total phosphorus (TP) following the methods described by Valderrama (1981), Mackereth et al. (1978) and Strickland & Parsons (1960).In the field, the abiotic variables pH, water temperature (Temp), electrical conductivity (Cond), turbidity (Turb), total dissolved solids (TDS) and dissolved oxygen (DO) were measured with a Horiba U-22 multi-probe at 0.5 meters from the bottom.
A principal component analysis (PCA) was used to verify the ordering of the sampling sites in relation to the intensity of the association among the abiotic variables.To assess the water quality related to nutrient enrichment, the Lamparelli's trophic state index (TSI) for the total phosphorus concentration was used according CETESB (2015).
The results of the analyses of the abiotic and biotic variables are presented with box-and-whiskers plots, in which the lower and upper limits of the box correspond to the 25th and 75th percentiles, respectively, the whiskers correspond to the minimum and the maximum values, and the center line of the distribution corresponds to the median.The non-parametric Kruskal-Wallis test (H) followed by a Student-Newman-Keuls (SNK) test were used to investigate the existence of significant differences in the abiotic and biotic variables among the sites.A canonical correspondence analysis (CCA) was used to verify the ordering of the sampling sites in relation to the intensity of the association among the abiotic variables.were carried out using the routines of the PAST 3.x and BioEstat 5.1 programs.

Spatial variation in abiotic variables
The box-and-whiskers plots of the abiotic variables (Figure 2) demonstrate that the pH values were nearly acidic, with variation among the sampling sites of min: 4.9 and max: 6.7.The medians of the pH values were under the CONAMA (2005) #357 limit (between 6.0 and 9.0) at all sites (P1: 5.61, P2: 5.59 and P3: 5.59).The highest values of electrical conductivity (343 µS•cm -1 ), turbidity (72.7 NTU), total dissolved solids (223 mg•L -1 ), total nitrogen (15.37 mg•L -1 ) and total phosphorus (0.24 mg•L -1 ) were observed at P2.The total nitrogen and total phosphorus at all sites were above the limits according to the CONAMA (2005) #357 resolution (TN lower than 1.27 mg•L -1 and TP lower than 0.03 mg•L -1 ).Regarding the dissolved oxygen, the lowest values were observed at P2 (3.2 mg•L -1 ), which was the only site with values below the limit of the mentioned resolution (DO not lower than 5 mg•L -1 ).The Kruskal-Wallis test (H) and a posteriori multiple comparisons using the Student-Newman-Keuls test (Table 1) showed significant differences (p<0.05) in electrical conductivity, total phosphorus and dissolved oxygen between P1 and P2 and between P2 and P3, demonstrating that P2 significantly differed from the other sites.

Principal Component Analysis (PCA)
Regarding the PCA (Figure 3), the first two components explain 61.47% of the total variability in the analyzed data.Table 2 shows the correlation of the variables with the axes.The PCA showed the worst conditions in relation to the water quality at P2.The data cloud for this site was separated from those of the other sites (convex hull), having greater association with electrical conductivity, total nitrogen, total phosphorus and total dissolved solids.On the other hand, sites P1 and P3 showed greater association with DO.Acta Limnologica Brasiliensia, 2016, vol.28, e17

Benthic macroinvertebrates community and biotic indices
The analysis of relative abundance (Figure 4) that was conducted by adding up all samples by site showed a greater presence of Oligochaeta at P2 compared to P1 and P3.Chaoborus sp.showed a great abundance at all sites.Chironomini was also observed at all sites and showed higher abundances at P3 and P1.Polymitarcyidae showed a higher abundance at P1. CETESB (2013) classifies some taxa of the zoobenthos by their tolerance/sensitivity to different environmental impacts.According to this classification, the sensitive group (Polymitarcyidae) was more abundant at P1 (23.27%) compared to the other sites, where it was almost absent (<2.5%); the semi-tolerant group (Chironomini, Tanypodinae, Ceratopogonidae and Helobdella stagnalis, Linnaeus, 1758) was more abundant at P3 (88.51%) and P1 (64.43%) compared to P2 (38.44%); and the tolerant group (Oligochaeta) was more abundant at P2 (59.86%) compared to P1 (12.30%) and P3 (9.20%).
The distribution of the biotic index values by site (Figure 5) shows a tendency for higher values of total density, Shannon-Weaver diversity, taxa richness and uniformity at P1 and higher values of Simpson's dominance at P2 and P3.In general, all the samples showed low values of total density (lower than 2000 org•m -2 ), Shannon-Weaver diversity (lower than 0.56), and taxa richness (lower than 6).The medians of the uniformity values were lower than 0.5 at P2 and P3, and the medians of the dominance values were higher than 0.5 at P2 and P3.The Kruskal-Wallis test (H) and a posteriori multiple comparisons using the Student-Newman-Keuls test (Table 4) show significant differences (p<0.05) for  the total densities between P1 and P3, the Shannon-Weaver diversity between P1 and P2 and between P1 and P3, and the taxa richness between P1 and P3.This analysis therefore demonstrates that P1 significantly differs from the other sites.
The multimetric benthic community index, BCI (CETESB, 2013), which is calculated using the Shannon-Weaver diversity and taxa richness values, classified P1 as regular and the other sites as bad (Table 5).

Canonical Correspondence Analysis (CCA)
The results of the CCA are shown in Figure 6.The first two axes explain 88.82% of the total variability in the analyzed data.The substantial overlap of the dispersion of the data clouds (convex hull) of the three sites indicates that they have similar conditions in relation to water quality and the composition of the zoobenthos.However, P1 showed better water quality, indicated by its greater association with dissolved oxygen and Polymitarcyidae.

Discussion
All of the sites sampled in this study are in a high degree of eutrophication and an accelerated process of degradation.The benthic community showed relative abundance values of organisms that are tolerant or semi-tolerant to environmental impacts of higher than 76% at P1 and higher than 97% at the other sites, indicating environmental stress and a high degree of eutrophication.The high values of TN and TP, which were in non-compliance with CONAMA (2005) Resolution #357, also indicated a high degree of eutrophication.
The sensitive taxa of the order Ephemeroptera and family Polymitarcyidae were fifteen times more abundant at P1 than P2 and ten times more abundant at P1 than P3, indicating that P1 has better environmental conditions, which was corroborated by higher DO values.Most species of Ephemeroptera show a preference for apparently clean water with high concentrations of oxygen (Wetzel, 1993).
Better environmental conditions at P1 were also indicated by the benthic community indices,  study, demonstrating that the Billings Reservoir has a high degree of degradation with accelerated eutrophication conditions in addition to being contaminated by metals in sediment.Alvarenga proved to be the site with the highest degree of eutrophication and higher metal contamination in sediment, which directly reflects the quality of the water and fish.Hortellani et al. (2012) mention that Alvarenga is a critical area for the accumulation of metals in sediment and also that a slight increase in mercury at Taquacetuba and Biguás Island occurs during the rainy period.
The abiotic assessment differentiated Alvarenga (P2) from the other sites, showing that this site had the highest degradation of water quality compared to the other sampled sites.On the other hand, the macroinvertebrate analyses improved the assessment of the water quality, setting apart the sites with higher values of dissolved oxygen, especially Taquacetuba (P1), where sensitive taxa occurred.Therefore, in conclusion, the benthic community in association with abiotic metrics proved to be a useful tool as an indicator of environmental conditions.The results indicated that the fishing activity at Billings Reservoir must be done with caution at the three sampling sites, but fishing is especially not recommended at Alvarenga due to the worst water quality occurring at this site, as shown by the values of the abiotic variables, the TSI, and the higher abundance of tolerant organisms.

Figure 2 .
Figure 2. Abiotic variables measured at sampling sites P1 -Taquacetuba, P2 -Alvarenga and P3 -Biguás Island at Billings Reservoir (Brazil, São Paulo State) represented by box-and-whiskers plots where the lower and upper limits of the box correspond to the 25th and 75th percentiles, respectively, the whiskers correspond to the minimum and maximum, and the center line of the distribution corresponds to the median.

Figure 5 .
Figure 5. Biotic indices by sampling site (P1 -Taquacetuba, P2 -Alvarenga and P3 -Biguás Island) in Billings Reservoir (Brazil, São Paulo State), represented by box-and-whiskers plots, where the lower and upper limits of the box correspond to the 25th and 75th percentiles, respectively, the whiskers correspond to the minimum and maximum, and the center line of distribution corresponds to the median.

Table 1 .
Results of Kruskal-Wallis test (H) and subsequent Student-Newman-Keuls (SNK) test for abiotic variables among the sampling sites.

Table 2 .
Correlation of abiotic variables with the axes (components) of principal component analysis (PCA) for the variables analyzed for the sampling sites at Billings Reservoir (Brazil, São Paulo State).

Table 5 .
Results of the benthic community index (BCI) based on the diversity and richness (average among samples by site).