Effect of Bahir Dar municipal effluents on water quality of the head of Blue Nile River

The study was conducted with the main objective of determining the effect of Bahir Dar municipal effluents on water quality of the head of Blue Nile River. Physico-chemical parameters were measured at seven points, whereas aquatic macro invertebrates were sampled at six sites. A total of 6813 aquatic macro-invertebrate individuals belonging to 30 families were collected. The Shannon–Wiener diversity Index, the Hilsenhoff family-level biotic index, Family richness and percent dipterans were calculated and differed significantly among sampling sites (p < 0.05). Physico-chemical parameter mean values differed significantly among sampling sites (p < 0.05), dissolved oxygen mean value being higher at sampling site (A) and BOD5, TDS and conductivity values being higher at (C5). BOD5, conductivity and total alkalinity mean values were above permissible levels set for municipal effluents to be discharged to surface water. DO, BOD5 and total alkalinity mean values at head of Blue Nile River were lower than WHO recommended values for drinking water. The study concludes that the Bahir Dar municipal effluents severely affected the water quality of the head of the Blue Nile River.  Therefore, a municipal waste water treatment system is urgently recommended.Keywords: Bio-monitoring, macro invertebrates, physico-chemical parameters

Effects of Bahir Dar Textile Factory Effluents on the Water Quality of the Head Waters of Blue Nile River, Ethiopia

The study was conducted in 2013/14 with the objective of determining the effects of Bahir Dar textile factory effluents on the head of Blue Nile River water quality. Dissolve oxygen was higher at the upstream site of the river, whereas BOD5, TDS, and total alkalinity values were higher at wastewater outlet of the factory site. The mean values of dissolved oxygen, BOD5, and total alkalinity were above maximum permissible limits set by WHO for drinking water at head of Blue Nile River. The mean value of BOD5 was above permissible limit of IFC for textile effluents to be discharged to surface water. A total of 836 aquatic macroinvertebrate individuals belonging to 21 families were collected. The Shannon-Wiener Diversity Index, the Hilsenhoff family-level biotic index, family richness, and percent dipterans were calculated. Hilsenhoff family-level biotic index and percent dipterans metrics differed significantly among sampling sites (P<0.05). Hilsenhoff family-level biotic index was higher at the most downstream site but percent dipterans were higher at site of discharge of effluent to the head of Blue Nile River. Therefore, there is indication that effluent demands frequent control and proper treatment before being discharged to the environment

Plankton diversity in tropical wetlands under different hydrological conditions (Lake Tana, Ethiopia)

Plankton is an integral part of wetland biodiversity and plays a vital role in the functioning of wetlands. Diversity patterns of plankton in wetlands and factors structuring its community composition are poorly understood, albeit important for identifying areas for restoration and conservation. Here we investigate patterns in local and regional plankton richness and taxonomic and functional community composition in riverine papyrus swamps, river mouth wetlands, and lacustrine wetlands in the Lake Tana sub-basin, Ethiopia. Data on phytoplankton, zooplankton, and environmental variables were collected from 12 wetlands during the dry and wet seasons of 2018. Redundancy analysis, and linear mixed effect models, were used to investigate differences in local environmental conditions and variation in plankton community richness and composition between wetland types. We also assessed the ecological uniqueness of the plankton community by calculating the contribution of a single wetland: local contributions to overall beta diversity (LCBD) and contributions of individual species (SCBD) to overall beta diversity (BDTotal). Beta regression models were used to investigate the relationships of LCBD and SCBD to environmental variables, wetland, and taxa characteristics. A total of 85 phytoplankton taxa, distributed among 18 Reynolds functional groups, and 57 zooplankton taxa were observed over the entire set of samples. Local plankton taxon richness was significantly higher in riverine papyrus swamps (mean taxa of 30 phytoplankton and 21 zooplankton) compared to river mouth wetlands (mean taxa of 27 phytoplankton and 13 zooplankton). Several local environmental variables and the composition of the plankton community differed significantly between the three wetland types. The highest phytoplankton ecological uniqueness (LCBD) was detected in lacustrine wetlands, whereas the riverine papyrus swamps had the highest zooplankton ecological uniqueness. Based on our analyses, we recommend protecting the wetlands with high LCBD values and stress the importance of various wetland types for preserving the diverse plankton communities of Lake Tana wetlands