Benthic macroinvertebrates as indicators of anthropogenic pressure on coastal river water quality

Introduction Coastal river systems are among the aquatic ecosystems most vulnerable to anthropogenic pressure due to the convergence of agricultural, urban, and extractive activities that progressively degrade ecological integrity. In this context, biomonitoring using benthic macroinvertebrates has emerged as an effective approach for assessing water quality, as it integrates the cumulative effects of environmental disturbances over time. Therefore, this study aimed to evaluate benthic macroinvertebrates as indicators of anthropogenic pressure on water quality in the Chancay–Huaral River basin, identifying ecological gradients associated with tolerant and sensitive taxa. Methods The study followed a quantitative approach with a non-experimental, descriptive–explanatory design. Six monitoring points were established along the basin’s altitudinal gradient. Benthic macroinvertebrates were collected using a Surber net and identified at the family level. Biological water quality was assessed using the nPeBMWP index, while multivariate ordination analyses were applied to examine spatial patterns in community structure. Results The findings revealed a consistent dominance of tolerant taxa, particularly Chironomidae and Orthocladiinae, across all sampling sites. The nPeBMWP index values classified water quality as polluted in all evaluated periods. Multivariate analyses showed clear spatial patterns associated with anthropogenic disturbance, evidencing reduced ecological heterogeneity and the displacement of sensitive taxa. Discussion These results indicate persistent biological degradation linked to chronic anthropogenic pressures within the basin. The dominance of tolerant families and the absence or low representation of sensitive taxa confirm the alteration of ecological conditions. Overall, the study supports the effectiveness of benthic macroinvertebrates as integrative indicators of ecological quality and underscores the urgent need to strengthen environmental management and restoration strategies in coastal river systems exposed to sustained human impact.