Macroinvertebrates Assemblages as Bioindicators of Ecological Health in Lake Arekit: Response to Physicochemical Stressors in a Tropical Highland Lake

Abstract

Freshwater lakes in tropical highlands face growing threats from human activities, but their ecological responses are poorly understood. This study examines the spatial distribution of benthic macroinvertebrates in Lake Arekit, Ethiopia, and their relationship with water quality to assess ecological health under agricultural and urban pressures. Water quality and macroinvertebrate communities were analyzed at three sites from February to May 2023. Results showed significant spatial differences in water quality (p < 0.05), with higher turbidity (110.11 NTU), nitrate (36.37 μg L⁻¹), and ammonium (83.95 μg L⁻¹) at disturbed sites. Macroinvertebrate communities included six taxa, dominated by pollution-tolerant Chironomidae (22.4%), Odonata (31.5%), and Hemiptera (29.6%), with low diversity (Shannon index: 1.3–1.5) indicating moderate pollution. Redundancy Analysis (RDA) linked ammonium (NH₃-N), turbidity, and total dissolved solids to community structure, explaining 93.2% of species-environment variance. The shoreline site, affeced by waste and runoff, had fewer taxa (5) and more tolerant species, while the macrophyte site had higher diversity (6 taxa). These findings reveal Lake Arekit’s ecological decline and highlight macroinvertebrates as effective bioindicators. Recommendations include reducing fertilizer use and improving wastewater treatment to combat eutrophication and protect biodiversity. This study offers a monitoring framework for freshwater ecosystems in developing regions facing similar human-induced threats.