QUALITY OF WATER BY PHYSICOCHEMICAL FACTORS AND MACROINVERTEBRATES IN THE AGUAPEY STREAM (PARAGUAY).

This research presents the results of the water quality study of the Aguapey stream (Paraguay) by means of physicochemical parameters and the diversity of aquatic macroinvertebrates. Samples were performed between the season of September 2016 and July 2017, in four locations alongside the water course, three were performed in the main channel and one in the urban tributary of the Cai Puente stream. Simplified Index Water Quality (ISQA) was used. Biodiversity founded on communities was considered through the Dominance, Simpson, Berger-Parker and Shannon-Wiener indexes. It was found that the waters of the Aguapey stream felt into the turbid category (moderately polluted with organic matter), being stations one and two most affected due to agricultural activities, remarkably improving downstream. Conversely, the Cai Puente stream was the most affected (polluted) due to sewages from domestic service and industrial activities, with very excessive levels of total phosphorus and fecal coliforms. Results show that the wealth and species variety were influenced by organic pollution. Diversity of macroinvertebrates could represent adequate assessment instruments for the routine monitoring of the ecological status of the basins and streams of the region.


792
The use of the simplified water index (ISQA) to analyze the physicochemical parameters is of great importance, since it allows to find consistent results rapidly and in a low-cost, being a useful instrument to recognize water quality as well as to identify sources of contamination (Bustamante et al.,2002).
Nonetheless, to complement the information of the physical-chemical features it is appropriate to also include the biotic components whose sensitivity to changes in the physical environment allows a more precise environmental assessment. (Rodriguez Badillo, et al., 2016). With biological indicators, the response of living organisms that are exposed to contaminants or that can be helpful for predicting future damage is valued and can even present the dangerous effects by themselves.
Biological indexes have the advantages that their measurement is not restricted to the time of sampling, subsequently they allow discovering changes produced over time, because living organisms have evolutionary adaptations to certain environmental conditions and have limits of tolerance to the diverse alterations (Alvarez, 2007).
Benthic macroinvertebrates are one of the most appropriate groups for the purposes of assessing quality of aquatic ecosystems (Rodriguez Badillo et al., 2016), being one of the most used for their ability to detect the alteration ( The Aguapey stream is situated in the Paraná River basin, South America, being one of the most affected by anthropogenic actions in the last decades. Located in the Department of Itapúa, the Oriental Region of Paraguay ( Figure Nº 1), with a subtropical climate, ideal for agricultural activities; the cultivation of rice with irrigation is one of the most important farming activities in the Aguapey basin, increasing the area from 8750 hectares to 50,950 hectares in the last decade (Friedmann y Weil, 2010;CAN, 2015). The stream course was affected by the reservoir of the Yacyreta Hydroelectric and it was dammed, but it was diverted by a channel of about 12, 5 km, to lastly end in the Brazo Aña Cua in the Paraná river. The study derives from the necessity to provide ecological and scientific evidence concerning the water quality of the stream Aguapey using physicochemical factors and multiplicity of aquatic macroinvertebrates.

Material and Methods:-
The study was performed in three sampling stations of the Aguapey stream (Juguai E1 (-27. To collect data on the physicochemical parameters: pH, Temperature, conductivity, SST and dissolved oxygen, a HACH Q10 multiparameter was employed; for the analysis of the COD and nitrate one liter in plastic container; and for Total Phosphorus, one liter of water was collected and refrigerated in amber glass bottle, until reaching the Laboratory, based on the "Standard Methods for the Examination of Water and Wastewater" (APHA, 2012).
To apply the ISQA, this is obtained from a formulae that combines five physicochemical parameters (Colman y Bellagomba, 2006): ISQA = E · (A + B + C + D), where E stands for water temperature (T in Cº), A: organic chemical demand according to the oxidability to permanganate (COD-Mn in mg/l), B total suspended solids (SST in mg/l), C: dissolved oxygen (O2 in mg / l) and D: conductivity (CE in μS/cm at 18 ºC). To classify the water quality according to the numerical value of the ISQA, it was employed, considering the characteristics that the water resource must present according to the intended use (Colman y Bellagomba, 2006; Alonso, 2013): Very clear waters (85 to 100), clear (75 to 85), turbid (60 to 75), dirty (45 to 60), deteriorated (30 to 45), diluted residual (15 to 30), and residual (0 to fifteen). Later, the water quality in the stream was calculated taking into account the results acquired in the field and laboratory, considering the resolution 222/02 of SEAM (Secretaría del Ambiente Paraguay) (SEAM, 2002).

Macroinvertebrates:-
Macroinvertebrate sampling was performed according to the endorsements of Protocol sampling and analysis of benthic invertebrates (Alba-Tercedor et al., 2005). For the fordable sections for the standardization of the method, it was to sink the net bag (type D, 500 micron mesh) at the bottom of the stream in the opposite direction to the water flow, whereas ahead the operator proceeded to remove and hit the substrate dynamically with the feet, this technique was carried out in an interval of 10 seconds, in the different habitats present at the sampling point. The gathered material was emptied on white trays (0.60 x 0.40 x 0.12 m) to which water was added beforehand, then the macroinvertebrates were separated with tweezers placing them in airtight jars with ethanol at 70%.

Lab work:-
It was performed observation and identification of macroinvertebrates with optical microscope and stereoscope to account for the groups discovered. Taxonomic documentations were made through key level to families: Domínguez y Fernández (2009); Lehmkuhi (1979); y Rocabado y Goitia, (2011).

794
To create the graphs and calculations of physicochemical and biological variables, it was employed the statistical program PAST -Palaeontological STatistics, ver. 2.16 (Hammer et al. 2005) and Microsoft Excel 2010, such as wealth (number of families) found and estimated with Chao-1 dominance and diversity indices of Shannon-Weiner (H'), Berger-Parker y de Simpson (S) (Magurran, 2004). Table 1:-Physicochemical parameters in the different seasons and sampling periods.

Results and Discussions:-
During summer period the results of the physicochemical analysis, according to Table 1 revealed a striking difference in the dissolved oxygen concentration, being lower in stations 1 and 4, this is due to the high concentration of organic matter in the water, considering that COD level increased. According to the Generalitat de Valencia (2007), the COD allows measuring the number of organic compounds or oxidizable mineral salts found in water. The conditions improved in the following periods in most of the sampling points, but not in the E4. Citing Guerrero-Bolaño et al., (2003) and Yépez et al., (2017) the concentration of oxygen depends on the characteristics of the channel, the turbulence of the water, the chemical and biological processes as well as it influences the richness and dissemination patterns of the macroinvertebrate families. The values of pH, Nitrate and Turbidity are within the class 2 range of water quality according to Resolution Nº 222/02 of the SEAM. Being the range for the pH from 6 to 9, the E1 was with a pH close to the lowest minimum., during summer, autumn and winter times. Correspondingly, E4 was the one with the uppermost levels of dissolved solids, which in the summer grasped 244 mg/L and a conductivity of 375 uS/cm. The electrical conductivity provides an overview of the concentration of salts and ions (dissociated salts) present in water due to the urban and industrial discharges of the city (Generalitat de Valencia, 2007).
It is necessary to note that in spring and summer there was a superior agricultural activity, specifically rice crops in the upper area of the basin, where the planting and harvesting were carried out (Alonso, 2013), in alluvial plain soils, specifically Aquic Kandiudult, with low pH values (4.21 to 4.9 UpH), with a high organic matter content that directly affects water quality due to erosion effects. These soils are low in phosphorus and micronutrients, the reasons why fertilizer is usually incorporated in agriculture. The total concentration of phosphorus, remained close to the limit values established by standard maximum 0.05 mg / L for class 2, conversely at station 4, Cai Puente urban stream, it was significantly exceeded (  , that is excellent, clean, with low organic content, which may have different uses; in summer, the first station went down to "dirty waters"; and E2 and E3 to "muddy waters" having substantial mineral and organic content, it is recommended activities such as fishing, but not swimming; water quality improves again in autumn and winter in the E3 to "clear waters", still being clean and easy to make drinkable and it is also available for swimming. In Station 4, of the urban stream, water quality was considered as "dirty water", with unpleasant odors and flavors, this might have been due to death fish in periods of low temperatures according to Colman and Bellagomba (2006)   Lastly, when the Aguapey stream water chemical indicators were analyzed, applying the ISQA and macroinvertebrates as bioindicators, they fell into the turbid category (moderately contaminated with organic matter), with stations one and two being the most affected due to farming activities and considerably improving downstream. Nonetheless, the Cai Puente stream turned out to be the most contaminated due to effluents from domestic service and industrial activities, with very high level of total phosphorus and fecal coliforms. Macroinvertebrate biodiversity and ISQA may be a helpful instrument to monitor water quality of streams and rivers.

Acknowledgements:-
This research was possible through funding provided by to the National Council of Sciences and Technologies (CONACYT) of Paraguay.