Assessment of ecological quality of the Tajan River in Iran using a multimetric macroinvertebrate index and species traits

Abstract

The objectives of this study were to assess the biological water of the Iranian Tajan River using different metrics, i.e., a Multimetric Macroinvertebrate Index (MMI) and a traits-based method. Twenty-eight physico-chemical parameters, 10 habitat factors, and abundance of macroinvertebrates were obtained for 17 sites. The Shahid-Rajaie dam divides the Tajan River into an up- and downstream part, with different land uses. Eighteen metrics were used to represent four components of ecosystem quality, including tolerance (Hilsenhoff, SIGNAL), diversity (Margalef, Shannon-Wiener, Simpson, and Evenness), abundance (total number of taxa, individuals, Ephemeroptera, Plecoptera, Trichoptera, EPT, and Insects), and composition of assemblages (% Ephemeroptera, % Plecoptera, % Trichoptera, and % EPT Taxa). The integrated MMI was calculated by averaging the obtained scores of all indices. In the next step, we gathered information on 22 biological traits of macroinvertebrates to evaluate whether (group of) traits could be identified that are indicative for specific or general stress. Result showed a decrease in MMI from upstream (very good water quality) to downstream (bad) due to human activities. Industrial activities like pulping and papermaking operations or sand mining in the downstream part had more effects than agriculture and fish ponds in the upstream part. A redundancy analysis biplot showed the variation between the modalities of trait of macroinvertebrates and their correlation with physico-chemical parameters in Tajan River. The findings show that traits can be indicative for different kind of stress but that more effort has to be put in gathering data sets to disentangle the effect of habitat quality, pollution, and the physico-chemical properties of high- versus lowland rivers.

Fig. 1

Map of Tajan River and sites in the north of Iran

Fig. 2

Changes of DO, BOD, and nutrients in sites of Tajan River (for the exact placement of the sites is referred to Fig. 1)

Fig. 3

Redundancy analysis (or PCA, since the explanatory variables explain all variance) biplot showing the variation between the modalities of trait characteristics of macroinvertebrates and the correlation with physico-chemical parameters in Tajan River. Of all variance, 26 % is displayed on the horizontal axis and another 20 % on the vertical one. Only the 30 traits which had the strongest correlations with the physico-chemical parameters are shown. See Table 2 for trait abbreviations. Group 1 constitutes the habitat parameters bank vegetative protection, epifaunal substrate/available cover, embeddedness, channel flow status, channel alteration, frequency of riffles, bank stability, and riparian vegetative zone width as well as the sum of all habitat parameters