Abstract

Data on biodiversity loss in freshwater and aquatic ecosystems in Africa is lacking, and riverine biodiversity remains undocumented. This study provides a baseline assessment of aquatic macroinvertebrates in Tungu stream, a tributary of the Nithi River in Kenya. Sampling was conducted over a nine month period across the upper, middle, and lower courses of the stream using a Surber sampler, with a total of 27 samples collected. In total, 38 benthic macroinvertebrate genera from 29 families were identified. The stream upper course had the highest richness (36 genera; mean abundance = 53), while the lower course had (16 genera and mean abundance = 16). Macroinvertebrate abundance was significantly higher in the upper course compared to the middle and lower courses (p < 0.05). Diversity was highest in the stream upper course (H′ = 3.30) and lowest in the lower course (H′ = 2.60). Pollution sensitive genera such as Habrophlebia were largely confined to the upper course, while Epeorus appeared in all three zones, suggesting healthy riverine vegetation and environment. These findings indicate that Tungu Stream supports healthy riparian vegetation and aquatic habitat, highlighting the importance of conserving and protecting its riparian zone.

Key words: Riverine biodiversity, aquatic macroinvertebrates, Tungu stream, baseline assessment, Tharaka Nithi.