Diversity of benthic macroinvertebrates as an indicator of water quality and ecological status of an Aegean river (Türkiye)

Bakırçay, one of the important rivers of Western Anatolia, has a length of 129 km and its basin covers approximately 3160 km 2 area. In addition to the existence of settlements, industrial and intensive agriculture-livestock activities are carried out, especially in the lower parts of the river. The objectives of this study are; a) to determine the diversity of benthic invertebrates distributed in Bakırçay, b) to evaluate the obtained data using various biological indices, c) to determine the interactions of species with environmental variables, and d) to estimate the water quality level of the river using BMWP and ASPT analyzes. Samplings were carried out at 15 stations between October 2017 and July 2018, seasonally. 11897 specimens belonging to 136 benthic invertebrate taxa were determined. Diptera and Oligochaeta were the dominant groups with 32 and 25 taxa, respectively. Station 4 has the highest species richness with 49 taxa. The highest individual number (3421) was at the 14th station. Tubifex tubifex and Physella acuta have the highest dominancy (25.76%) and frequency (51.67) values, respectively. Diversity (H’) values of the stations fluctuated between 1.367 (st. 13) and 3.154 (st.12). Similarity analysis showed that the 3rd and 11th stations have the highest similarity (> 90%), while the 14th station was an outgroup and has 28% similarity ratio. According to BMWP and ASPT scores, there was no 1st class water quality in the river, but the results of the TR-BMWP score suggested that the 1st, 4th and 6th stations had 1st class water quality.