Distribution and composition of macroinvertebrates in wala hot Spring, southwestern ethiopia

Abstract

Background: Macroinvertebrates can be used to indicate ecological status and effect of many stressors on water body. Hot spring water quality is getting affected by anthropogenic activities. Studying bio-indicators and physico-chemical parameters is important to predict the status and effect of stressors on hot springs water quality and use the information to maintain their ecosystem services Objective: This study aimed to study the distribution and composition of macroinvertebrates across different sites of Wala hot spring, south western Ethiopia. Method and material: This study was conducted in November, 11-17, 2021. A laboratory and field based cross-sectional study design was conducted. The macroinvertebrate sample was collected with physico-chemical parameters and human disturbance from 20 sampling sites of Wala hot spring. Beta diversity was used to investigate the distribution of macroinvertebrates across the sampling sites. Principal Component Analysis biplot was used to show the relation of sites with physico-chemical water quality. Canonical Correspondence Analysis was used to show correlation of macroinvertebrates with physico-chemical water quality. Analysis of variance was used to indicate the variation of macroinvertebrates richness and abundance between different sites and disturbance gradients. Pearson correlation was used to show the relation of macroinvertebrates with the water temperature variations. Result and discussion: A total of 1027 macroinvertebrate individuals belonging to 7 orders and 21 families were collected. The total beta diversity (β-sor) of sampled macroinvertebrates was 0.857. The contribution of species turnover (β-nes) was 0.783 while, the contribution of species nestedness (β-nes) was only 0.074. Significant difference was found in richness (P = 0.015) and abundance (P =0.0183) of macroinvertebrates along disturbance gradients. CCA revealed that macroinvertebrates were significantly correlated with Dissolved Oxygen, pH, nitrate-nitrogen, total hardness, and Chemical Oxygen Demand. The findings of this study revealed that there is a strong negative correlation (r = -0.83) between macroinvertebrates richness and water temperature. Similarly, a significant negative correlation (r = -0.75) was found between macroinvertebrates abundance and water temperature in different sites of Wala hot spring. Conclusion and recommendation: Distribution of macroinvertebrates in Wala hot spring was structured by species replacement rather than difference in richness. Macroinvertebrates richness and abundance has changed along human disturbance gradients. The change in physico-chemical water quality in different sites has affected macroinvertebrates. Temperature variation in the water has strongly negatively affected macroinvertebrates abundance and richness. It was recommended to study physico-chemical parameters and bio-indicators of the water not used in this study and to reduce disturbance affecting the water quality.