Diversity and Ecological Role of Aquatic Insects as Bioindicators of Water Quality in Tropical Streams

Abstract

This study assessed the diversity and ecological role of aquatic insects as bioindicators of water quality in tropical streams in Sulawesi, Indonesia, across contrasting land-use types: forest, agricultural, and urban. Standardized kick-net sampling was conducted at nine stations (three per stream) during the dry season of 2024, yielding 312 individuals from 28 families and six orders. The forest stream exhibited the highest diversity (22 families; Shannon H’ = 2.62) and richness of sensitive Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa (14 families), whereas the agricultural and urban streams displayed reduced diversity (16 and 12 families, respectively) and were dominated by tolerant Diptera, such as Chironomidae. Water quality parameters were significantly correlated with community composition: EPT richness showed a positive correlation with dissolved oxygen (r= 0.79, P< 0.05) and a negative correlation with biochemical oxygen demand (r = –0.73, P< 0.05). These findings align with recent tropical studies, indicating that riparian vegetation promotes higher insect diversity, whereas agricultural and urban land use simplifies communities and reduces functional diversity. These results emphasize the diagnostic power of insect metrics, particularly EPT taxa, as cost-effective bioindicators in tropical Asia. From a conservation perspective, maintaining riparian buffers is crucial for sustaining aquatic biodiversity and ensuring ecological integrity. This study provides novel baseline data for Sulawesi and highlights the potential of developing an EPT-based biotic index to strengthen freshwater biomonitoring and watershed management in Indonesia.

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