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Study on bacterial population dynamic changes of Maroon Dam Lake water to assess the feasibility of cage aquaculture
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Mina Ahangarzadeh *1   , Hossein Houshmand1 , Mahmood Hafezieh2 , Issa Sharifpour2 , Shapour Kakoolaki2 , Fatemeh Hekmatpour1 , Lefteh Mohseninejad1 , Farahnaz Kianersi1 , Samira Nazemroaya1 |
1- South of Iran Aquaculture Research Institute, Iranian Fisheries Science Research Institute, Agricultural Research Education and Extension Organization (AREEO), Ahvaz, Iran.
2- Iranian Fisheries Science Research Institute, Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran |
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Abstract: (11 Views) |
Introduction
Reservoir ecosystems are strongly influenced by both natural processes and anthropogenic activities, including agricultural runoff, livestock operations, domestic wastewater discharge, and land-use changes. These pressures can markedly affect microbial water quality and compromise ecosystem stability (Azzellino et al., 2006; Lu et al., 2010). Microbial contamination, particularly fecal pollution, represents one of the most critical threats to public health and aquaculture sustainability, as pathogenic microorganisms may be transmitted through contaminated water (Naderi et al., 2003). Indicator bacteria such as total coliforms and fecal coliforms are widely used to evaluate microbial contamination in surface waters because of their strong association with fecal pollution (Maghrebi and Jamshidi, 2008). The Maroon Dam reservoir is a strategic multipurpose water resource supporting irrigation, domestic use, and fisheries. Given increasing upstream anthropogenic activities, evaluating microbial dynamics is essential to determine water suitability for cage aquaculture and other uses. Therefore, this study aimed to assess spatial and seasonal variations in bacterial indicators and compare results with national and international standards.
Methodology
Five sampling stations—at the river inflow, three within the reservoir, and the outflow—were chosen based on hydrological characteristics. Sampling was conducted monthly for one-year to encompass all seasons. Water samples were collected following Iranian Standard No. 4208 for microbiological examination. The total bacterial count (TBC) was determined using the plate count method (APHA, 2017; Buller, 2004). Total coliforms (TC) and fecal coliforms (FC) were analyzed using the multiple-tube fermentation (MPN) technique in accordance with Iranian Standards No. 3759 and 7225. Fecal streptococci were determined based on Standard No. 3620. Anaerobic bacteria and Clostridium perfringens were examined in sediment samples using standard culture techniques (APHA, 2017). Statistical analysis was conducted using two-way ANOVA followed by Duncan’s multiple range test at a 95% confidence level (p<0.05). Seasonal and spatial differences were evaluated.
Results
Significant spatial differences were observed among stations (p<0.05). The highest concentrations of total coliforms, fecal coliforms, and total bacterial counts were recorded at the outflow and inflow stations, while the lowest values were measured at stations within the reservoir body. This distribution pattern suggests the presence of natural self-purification processes within the lake, including sedimentation, dilution, sunlight exposure, and biological interactions. Similar findings have been reported in other reservoirs where microbial loads decreased from inflow zones toward central lake areas (Alobaidy et al., 2010; Houshmand et al., 2020). The reduction of microbial contamination within reservoirs has also been attributed to settling and die-off processes (Ehramposh et al., 2013). Microbial indicators exhibited significant seasonal variation (p<0.05), with the highest values observed during summer and the lowest during winter. Elevated summer concentrations may be associated with higher water temperature, enhanced bacterial metabolism, reduced flow velocity, and increased anthropogenic inputs. Temperature is known to strongly influence microbial growth and survival in aquatic environments (Patil et al., 2012). Several studies have similarly reported increased bacterial indicators during warmer months (Yaqub Zadeh and Safari, 2014; Islam et al., 2021; Rather et al., 2023). Conversely, reduced microbial counts during colder seasons may be due to decreased metabolic activity and increased dilution from rainfall (Shahsavari Pour et al., 2010). Although some studies have linked higher bacterial contamination to wet seasons due to runoff transport (Kim et al., 2005), the present findings indicate that temperature was the dominant controlling factor in this reservoir system. Average range of total coliforms counts from 0.48 × 10² to 5.06 × 10² MPN/100 ml and average range of fecal coliform counts from 0.17 × 10² to 1.56 × 10² MPN/100 ml. Total bacterial counts ranged from 0.105 × 10³ to 18.7 × 10³ CFU/ml. Fecal streptococci were negligible (<0.01 CFU/100 mL). Anaerobic bacteria and Clostridium perfringens were below detectable limits. The low abundance of fecal streptococci may be attributed to sunlight inactivation and UV-induced DNA damage, as previously reported (Byappanahalli et al., 2015).
Discussion and conclusion
According to Iranian drinking water Standard No. 1053, potable water must be free of coliform bacteria. Therefore, untreated water from the reservoir is unsuitable for direct consumption. However, measured values did not exceed permissible limits established for surface water discharge and agricultural irrigation (Environmental Protection Organization of Iran, 1992). Furthermore, microbial concentrations were below acceptable limits for fish farming (Shahryari et al., 2008), confirming the reservoir’s suitability for cage aquaculture. Comparable studies in Iranian reservoirs have reported similar conclusions regarding microbial acceptability for aquaculture despite non-compliance for direct drinking purposes (Nekouei Fard et al., 2019; Houshmand et al., 2020).In general, according to the results, the water of the Maroon Dam lake in this sampling period is permissible for fishing and fish farming in all seasons according to Iranian standards, but adopting a preventive and participatory approach in the management of the dam's water resources is essential. In this context, continuous monitoring of the microbial quality of water resources using advanced indicators should be prioritized (Byappanahalli et al., 2015). It is also important to identify and control pollutant sources, especially during the rainy seasons when the probability of pollutants entering water resources increases (Hashemi et al., 2011). In addition, improving and developing rural and agricultural wastewater treatment infrastructure, increasing awareness of local communities about the role of human activities in the pollution of water resources, and creating a vegetation protection belt on the banks of rivers and dam reservoir inlets to enhance natural self-purification processes are considered key measures in reducing microbial pollution. Accordingly, it can be concluded that comprehensive and periodic assessment of water quality indicators is a key step in protecting water resources and the sustainability of related ecosystems ((Dagher et al., 2021).
Conflict of interest
The authors declare that they have no conflict of interest.
Acknowledgement
This study was conducted with the financial support of the Innovation and Technology Development Center, Technology and Applied Research Department of Khuzestan water and power Authority. |
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| Keywords: Bacterial water quality, Total coliforms, Fecal coliforms, Maroon Dam |
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Full-Text [PDF 929 kb]
(4 Downloads)
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Type of Study: Research |
Subject:
آلودگي محيطهاي آبي
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