Distribution of macroinvertebrates in Ceyhan River Basin (Turkey) and determination of environmental quality by Multimetric Index

In the present study, the distribution of macroinvertebrates among 44 sites in the Ceyhan River Basin and the determination of the ecological status of these sites using the macroinvertebrate multimetric index were investigated. Samples were taken between April 2021 and August 2022, covering the spring, summer, and autumn seasons. A total of 14,839 individuals belonging to 166 taxa were collected. According to the Shannon Diversity Index values, the highest and lowest values were calculated at site 27 (2.45) and 22 (0.22) in spring, site 39 (2.24) and 8 (0.1) in summer, and site 17 (2.28) and 8 (0.17) in autumn, respectively. The highest Shannon all-sample index value was found in the spring season (3.00). Analysis of similarity results (ANOSIM) showed that there were low but significant differences between the spring-summer (p = 0.001; R = 0.236) and spring-autumn (p = 0.001; R = 0.232) seasons in terms of species compositions. The first two axes of the canonical correspondence analysis elucidated 51.4% of the relationships between species and environmental variables, along with the significant effects of altitude, temperature, and pH on the distribution of macroinvertebrates. The ecological quality ratios of the sites were calculated with the Ceyhan Basin Multimetric Index (MMI-C). The ecological status of sites was evaluated over three seasons and divided into the following categories: 19 good, 16 moderate, 3 poor, and 4 bad. The results suggest that sites in residential areas have mostly bad ecological conditions, whereas the ecological status of sites situated farther away from residential areas, at high-altitude sites, tends to improve.