Response of aquatic macroinvertebrates to water quality and seasonal variations in the lower basin of the Cañete River, Peru

Macroinvertebrates are bioindicators sensitive to seasonal changes and water quality. This study evaluated how its community responds to physicochemical and seasonal variations at five stations of the river: Catapalla, San Jerónimo, Socsi, Puente Clarita, and Boca del Río, during rainy and dry seasons. Parameters such as pH, dissolved oxygen, conductivity, total dissolved solids, temperature, as well as NO₃^-, NH₄⁺, and phosphorus were measured. Macroinvertebrates were identified at the family level and indices of richness, dominance, density, and similarity were analyzed. Univariate and multivariate analyses, such as ANOVA and PCA, showed significant differences between stations and seasons, especially in Catapalla and Boca del Río. Two groups of stations were identified based on the similarity in their biological composition: one consisting of Catapalla, San Jerónimo, and Socsi, and another of Puente Clarita and Boca del Río. Dissolved oxygen and temperature positively influence abundance and richness, while high levels of dissolved solids, ammonium, and phosphorus have negative effects. Furthermore, some families, such as Tricorythidae, appeared only in the rainy season, demonstrating the effect of seasonality on aquatic biodiversity.