Study on Biotic and abiotic parameters to determine water quality of Rajaei Dam (Mazandaran province- Sari)

The The Shahid Rajaei Reservoir- Sari is an important and large reservoir in Iran. The major objectives of dam instruction are flood control, irrigation purposes, and electricity power. However the dam is going to supply drinking water for the people. In order to prevent threats of unsuitable water to human health risks and economic losses, it is necessary to monitor the water quality before offering it to people. In this study, some of the physicochemical parameters and Chlorophyl- a, phytoplankton,microb and fungi of Shahid Rajaei reservoir were measured at 4 stations (Shirin Roud branch, Sefid Roud branch, the crossing point of branches, near the tower) during six sampling months (June, July, August, September, November and February) in 2012-2013. In order to water quality classification, the water quality index, trophic status, Shanoon and saproby indices of reservoir calculated and the results compared to different criteria and standards. The results showed that the mean (±Standard Error) of temperature, dissolved oxygen, pH, phosohate, amonium and nitrate concentrations and Chlorophyl a were 21.35 (±1.30) ºC, 10.48 (±0.37), 8.54 (±0.04), 0.050 (±0.004), 0.036 (±0.004), 0.75 (±0.03) mg/l and 18.00 (±7.23) mg/m3, respectively. In the present study, temperature between surface and deep layer was stratified in June and July, which the stratification was registerd 0.47 and 0.69 °C decreases with increasing of each meter depth in 15 to 30 meter culumn. But, these changes for each increasing meter of water depth were 0.2 to 0.26 °C in August and September, respectively, and finally was close to zero in November. In the warm months (July, August and September) with the formation of thermal stratification in the reservoir was formed oxygen stratification, but in the cold season (November and February), with vertical mixing of water oxygen and percent saturation of the reservoir was nearly homogeneous. TSI showed the maximum and minimum values at stations 4 (oligotrophic condition) and 2 (mesotrophic condition), respectively. The maximum and minimum monthly values of TSI obtained in July, August (eutrophic level) and September, February (oligotrophic level) respectively. Based on the Water Quality Index (WQI), the reservoir was in the “good” quality in whole months, .This class shows that the reservoir is suitable as source of drinking water through routine treatment of drinking water and the quality of water is rarely is low. Meanwhile the water is suitable for swimming and water recreation and survives of .sensitive fish and other aquatic species. Based on the results, 107 phytoplankton species were identified during the period of study. The species were classified in 8 divisions. Maximum and minimum values of mean (SE) abundance observed in July and January, 661 (±286) and 10 (±2) million cells/m3 respectively at the surface layer. The One way analysis of abundance and biomass data showed temporal significant variances (P< 0/05), however the spatial variances of data were not significant (P> 0/05). Bacillariophyta and Pyrrophyta formed more than 95% of phytoplankton. 3 dominant species namely, Cyclotella meneghiniana, Goniaulax polyedra and Ceratium hirundinella formed about 70% of phytoplankton aboundance. Comparison of diversity indices (Shannon and Evenness) showed higher values in May and January; however the indices reached its lowest level (0.58 and 0.16) in August. Water quality assessment using Shannon index showed the lowest quality of water (moderately to high polluted) in July and August. This index demonstrated the highest water quality (slightly polluted) at station 1 and 4 respectively. The results of the water quality assessment using Saproby index (based on the resistant phytoplankton species to organic pollution) also indicated to organic pollution of water in the months of summer. The saproby assessment in stations categorized most of the stations in “moderately polluted” class of organic pollution except at station 4 which was in "slightly polluted" class. In conclusion, the removal (transfer) place and time of water to the water treatment plants.are impratnt because of temporal and spatial variation of water quality due to changes of phytoplankton structure in Shahid Rajaee Reservoir. Meanwhile, the survey showed that physico-chemical parameters alone did not reflect the actual conditions of aquatic water bodies. Monitoring of aquatic ecosystems must be complemented by biological monitoring. Microbial survey showed that the maximum and minimum geometric mean of the total number of bacteria, in September (6101559 CFU/100ml) and February (3310 CFU/100ml) respectively. However in stations, the maximum and minimum count of this parameter obtained at stations 2 (455316 CFU/100ml) and 3 (40964 CFU/100ml) respectively. There were no viable count of total coliform in the months of May and June. However it’s counting reach to the maximum value in September. Clostridium perfrigens showed viable count in water sample during September. The results also showed no proportion of fecal streptococci in microbe account in the Shahid Rajaei Reservoir. It might be good sign of suitable water quality in term of no-contamination by old and resistant fecal microbes. Base on the total coliform count, water quality was suitable for swimming and source of drinking water in most stations and months. The coliform count increased in August and September in stations 3 and 4. In these 2 months the probability of new fecal contamination increased by warm blood animals in the reservoir. It seems that the environment in September is suitable for accession of old and resistant microbes such as Clostridium perfrigens. The results of sample analysis revealed that the fungal colony counts in the station 4 and 5 were significantly higher than those the other stations. Moreover, the minimum and maximum of the fungal colony counts wereobserved in August and February, respectively. The most commonly isolated genera were Aspergillus, yeasts (especially candida) Penicillium, Cladosporium, Mucor, Fusarium, Althernariya, sterile hyafe and Paecilomyces respectively. Finally, in order to prevent of occurrence of eutrophication, algal bloom, and control of microbial activities and organic phosphorus loading it is necessary to control the activities of the human societies around the dam or the rivers tributary.

Iranian Fisheries Science Research Institute

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