Responses of stream macroinvertebrates to hydrological disturbances in Dinki watershed, central highlands of Ethiopia

摘要

Understanding of stream resilience to anthropogenic pressure is vital for sound implementation of conservation efforts, as resilient streams quickly recover from disturbance. However, evidence on the extent of stream recovery is minimal in Ethiopia. This study assesses the temporal responses of macroinvertebrate assemblages to hydrological disturbance of headwater streams in Dinki watershed, in the central highlands of Ethiopia. A total of 86 composite samples were collected along the longitudinal gradient of Dinki stream. A repeated measure analysis of variance (rmANOVA) was computed to explore changes in environmental and macroinvertebrate assemblages between autumn (2016), winter, spring, and summer (2017). The mean differences in the pre-and post-disturbance events (low and high-flows) were computed using the paired t-test. Likewise, a Redundancy Analysis (RDA) was used to visualize patterns in macroinvertebrate distribution and their relationship with environmental variables. Furthermore, indicator taxa were identified using the indicator value (IndVal) method. On top of that, the Jaccard's index was calculated to examine similarities between pre-and post-disturbance events as well as resilience score was computed to quantify the rate of recovery to spate disturbance. The maximum and minimum mean values of macroinvertebrate structures (abundance, richness, diversity, and evenness) were recorded during the pre-and post-disturbance events, respectively. The IndVal of assemblages were highly variable between seasons, indicating variations in ecological preferences. The small Jaccard's index values (low-flow: 0.48; spate:0.35) revealed the severity of the hydrological disturbances. Despite its slow rate (37% recovery within 20 days), a tendency of recovery was evident, particularly due to the presence of stable refuges and assemblages with resistance and resilience traits. Therefore, promoting stream conservation is plausible to ensure habitat heterogeneity, lessen