Distribution of aquatic macroinvertebrate communities in the arid ecosystems of the Jequetepeque Basin, Peru

This study evaluated the influence of altitudinal gradients and anthropogenic pressures on the composition and distribution of aquatic macroinvertebrate communities in arid ecosystems of the Jequetepeque River basin, northern Peru. Ten sampling stations were established along the middle and lower reaches of the river, covering an altitudinal range between 1,009 and 29 m a.s.l., and sampling campaigns were conducted during the 2022 and 2023 dry seasons. Macroinvertebrates were collected using standard methods, while physicochemical water variables, including pH, temperature, dissolved oxygen, and electrical conductivity, were measured in situ . Organisms were identified to the genus level, and the data were analyzed using multivariate approaches (PCA and CCA). A total of 33 genera belonging to 24 families and 11 orders were identified, comprising 1,182 individuals, with Diptera and Ephemeroptera being the most representative orders. A clear ecological pattern was observed along the longitudinal river gradient, characterized by the dominance of sensitive taxa such as Atopophlebia, Baetodes , and Leptonema in the upper and middle reaches, associated with well-oxygenated conditions and moderate electrical conductivity. In contrast, downstream reaches showed a progressive replacement by more tolerant taxa, including Melanoides, Biomphalaria , and Corbicula , correlated with increased electrical conductivity and a stronger influence of anthropogenic activities, particularly agriculture and hydrological regulation associated with the Gallito Ciego dam. Multivariate analyses confirmed that altitude, electrical conductivity, and dissolved oxygen were the most influential variables structuring macroinvertebrate communities. Overall, these findings demonstrate that the studied biological assemblages can detect subtle and progressive changes in river environmental quality, even when physicochemical variables do not show statistically significant differences between sampling stations, highlighting the value of aquatic macroinvertebrates as bioindicators for environmental monitoring in arid and semi-arid fluvial ecosystems with limited technical infrastructure.