Evaluation of Agreement among Ecological Indices in Determining the Quality of Karaj River (Alborz Province)

Abstract

Introduction: The study of the structure of aquatic communities in aquatic ecosystems has a special place in the ecological studies of aquatic organisms. Among the important and common macrobenthic indices, we can mention uni- variate and multi-variate ecological indices, which having different advantages and disadvantages, are still used in various studies in riverian waters. In recent years, studies using biodiversity index and bioindices, especially the Helsinhof index, were used to assessment of the water quality of the Karaj River. Assuming that there is agreement between the ecological indices of the region, the present study evaluated the degree of agreement between the quality statuses results obtained from different ecological indices in the Karaj River. Materials and Methods: In this study, we sampled macrobenthic fauna using a sorber sampler in nine stations during 2017-2018, seasonally. After separating and identifying macrobenthos, Shannon's index, EPT, ASPT, BMWP and HFBI were calculated. Then the ecological status of the stations was classified based on these indices. The percentage of stations whose ecological status was acceptable or unacceptable, as well as the compatibility level between these five indices in the study area, were calculated. To determine the similar tendency of the different indices in the classification of stations, the degree of correlation between them was determined using a non-parametric test. SPSS23 and Excel software were used for statistical analysis and Primer6 was used to determine biodiversity index. Shapiro-Wilk test was used to check the normal distribution of the data. In order to determine the significant difference between the desired data, one-way ANOVA and Kruskal-Wallis tests were used at the significance level of p<0.05. ArcGIS 10.3 and Terrset 17.3 software were used to prepare maps using the IDW method. Results: In terms of abundance, the Shironomide family was dominant. Baetis, Tubifex, Micrasema, Rhithrogena, Eporus, Hydropsyche, Leptophlebiidae, and Simulium made up 83% of the samples. The values ​​of H', EPT, ASPT, BMWP and HFBI were calculated (12.2±0.65), (5.6±2.8), (3.9±1), (48.8±23.34) and (4.6±1), respectively. The relative agreement in the results obtained from the five studied indices was seen in 67% of the stations with unacceptable quality in the case that 22% of the river stations showed complete agreement and 11% of the stations showed disagreement. The statistical analysis shows that there is a significant agreement between the results of the ecological status obtained from EPT with ASPT, BMWP and Shannon, if they are different with HFBI index. Also, based on the results of the correlation between the classification of the ecological quality obtained from the bioindices (positive and strong correlation between the EPT and the Shannon and BMWP), it indicates the similar direction of these indices in the classification of the stations. Discussion: There are structural and population changes of macrobenthos in aquatic ecosystems due to natural factors and human activities. Due to the lack of complete agreement between the assessment results of the five indices in this study, in order to use biological indices in each region for environmental management, there is a need to simultaneously use indices. Also, it is important to check the agreement between different indices and choose the appropriate ecological index. As a result, using each of these indices alone and without considering the above considerations can lead to wrong results. Based on the results of the present study, the Helsinhof index (HFBI) can be introduced as a more suitable index than other studied indices to assess the ecological status of the Karaj River.

Keywords

• agreement
• ecological status
• karaj river
• macrobenthic index