Patterns and adaptive differences of aquatic macroinvertebrates in protected and non-protected aquatic systems of Rwanda.

Abstract

Freshwater macroinvertebrates play a crucial role in maintaining ecosystem functions and represent a rich tapestry of global biodiversity. Their use as biological indicators due to their sensitivity to pollution guides decision-making for the management and conservation of freshwater systems. However, there is a paucity of data on their diversity and distribution in Rwanda. This study provides a baseline of taxonomic diversity, community composition, and structural adaptations across protected and non-protected areas in both lotic and lentic systems. Macroinvertebrates were sampled at 120 sampling points across 24 localities from November 2023 to August 2025 using a kick net (mesh size, 500 µm). Specimens were identified to order and family levels. Further, sensitivity to water quality and condition was estimated using the Tanzania River Scoring System (TARISS). The study identified 88 families, 81 from protected areas and 48 from non-protected areas. Most pollution-sensitive families, namely Perlidae (stoneflies), Pisuliidae (caddisflies), and Polymitarcyidae (mayflies), were limited to protected areas. Based on the TARISS scores, protected areas also harbor more sensitive macroinvertebrate communities than non-protected areas. Additionally, there was a significant difference in macroinvertebrate diversity and taxonomic richness between lotic and lentic areas. The findings underscore the importance of maintaining pristine freshwater conditions and improving conditions in non-protected areas to conserve sensitive macroinvertebrate diversity. Since this study used the presence-absence index, there is a need for regular monitoring and assessment to track changes and facilitate ecosystem management.