Composition of aquatic macroinvertebrate communities and adaptation of tolerance scores for the ABI index in the lower Quilca-Chili River basin, Arequipa, Peru

Aquatic macroinvertebrates are essential as accurate bioindicators of water quality but their behavior may change according to regional characteristics. The Quilca–Chili basin is one of the most important basins in southern Arequipa, Peru, yet lacks inventories that allow for the adaptation of family-level scores in biotic indices. This study aimed to analyze the structure of macroinvertebrate communities and to adapt the scores of bioindicator families for their application in the ABI index. Sampling was conducted in June and October 2022 at 16 stations using Surber nets, D-nets, and screen samplers (500 μm). The community structure and its relationship with physicochemical and biological variables were characterized. To adapt the scores of bioindicator families, Bray–Curtis similarity dendrograms and mean comparisons among grouped families were used. A total of 70 genera were identified, with the most abundant being Aedokritus, Camelobaetidius, Cricotopus, Cryptonympha, Metrichia, Microcylloepus, Onconeura, Polypedilum, and Simulium. The highest and lowest true diversity values were recorded in the Quilca and Vítor rivers, respectively. A trend of increasing percentage of EPT values and decreasing the percentage of Chironomidae was observed toward upstream stations. Score adjustments were made for 24 families, and four additional families were incorporated into the ABI index. Thirteen stations within the sub-basin corresponded to the “good” and “very good” water quality categories. The aquatic macroinvertebrate communities of the lower Quilca–Chili River basin showed no major alterations in their structure and diversity. The variation of the individual ABI scores of bioindicator families may be applied to arid ecosystems across South America.