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Pollution effects on diversity and content of the stable isotope N-15 in macroinvertebrates: a study of the impacts on the functional groups from the Maipo River basin

Maria Paz Briones-Alburquenque, Jorge Cortés-Miranda, Caren Vega Retter

Abstract

Context. Anthropogenic activities producing nitrogen have impacted freshwater ecosystems. The δ15N isotope is a key indicator of these impacts. Macroinvertebrates are vulnerable to pollution. Studying the macroinvertebrates functional feeding groups (FFGs) helps us understand the structure, function and balance of fluvial ecosystems, and how pollution alters ecosystem dynamics. The Maipo River basin is one of the most polluted in Chile. Aims. This study examines how pollution affects macroinvertebrate family diversity, FFGs, δ15N content, and trophic position. Methods. Using a Surber net five replicates were taken from two polluted and two non-polluted sites to analyze diversity at the family and FFGs levels. Differences in δ15N content and FFGs trophic position were assessed using a permutation t-test. Key results. Gathering-collectors inhabiting polluted sites showed less richness of taxa than the of the non-polluted sites. δ15N levels were higher in polluted sites, though gathering-collectors had a lower trophic position. Conclusion. Our results indicate that greater nitrogen input creates conditions which may affect the diet of studied organisms, potentially explaining the observed trophic position changes. Implications. Pollution alters the composition and structure of macroinvertebrates communities by affecting FFGs’ diversity. This should be considered in future management plans.

MF24234  Accepted 30 April 2025

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