Some lakes in the Rift Valley of East Africa are among the most productive in the world, while others are dystrophic, possessing a stable, opaque suspension of fine silt or clay. Understanding the causes of flocculation and sedimentation of this material could provide insight into why these lakes are so turbid. We collected samples of suspended clay from three turbid lakes (Langano and Abaya in Ethiopia, and Baringo in Kenya), measured the size-distribution and organic content of their suspended sediment, and performed laboratory studies of sedimentation rate as a function of pH and salinity. Most of the turbidity in the two Ethiopian lakes was due to particles between 0.5 and 1.5 μm, and the suspended material had a low organic content and C/N ratio in all the three lakes. Sedimentation velocity of the material increased with both salinity and pH, with velocities varying from near 0 at neutral pH and low salinity, to 3 cm h-1 as pH approached 12 or salinity approached 25 ppt in the case of Lake Abaya. These results may explain why it is only freshwater lakes that demonstrate these turbid clay suspensions, and suggest mechanisms through which their turbidity might be altered.
This study examined the actions and involvement of stakeholders in the management of wetland resources in the Central Rift Valley of Ethiopia. Data were generated through interview conducted with 78 key informants selected from different stakeholders using snowball sampling technique. Thematic analysis was used to analyze the data using NVivo 8 qualitative data analysis software. The result revealed that wetland management is in the dominion of many stakeholders that are categorized into local community, government institutions, private sectors, research institutions and civic societies. The stakeholder arena was characterized by weak coordination, conflicting and/or overlapping roles, responsibilities, and influence power asymmetry. Stakeholders’ collaboration and engagement in wetland management is challenged by weak institutional frameworks typified by inconsistency, vague provisions on wetlands, and weak enforcement. The common property notion and the lack of clear property rights regime for wetland resources exacerbated the challenge for proper management of wetland resources. All these factors have contributed to the lag in the management of wetland resources of the area which probably may lead to unsustainable resources outcomes. Hence, there is a need to integrate institutions to avoid conflicting or contradictory issues, enact wetlandspecific institutional frameworks, and design multi- stakeholder platforms at various levels via public-private partnership for effective, proactive and synergetic involvement of stakeholders. Key words/phrases: Central Rift Valley, Ethiopia, Institutions, Stakeholders, Wetlands.
This study aimed to assess changes in spatial cover of Lake Abijata and impacts of land use/land cover changes on the floristic composition and herbaceous biomass in and surrounding Abijata Shalla National Park. Data were collected using systematic sampling method from 64 quadrats of 400 m2 established along eight line transects. Land use/land cover changes over time (from 1978 to 2018) were determined from satellite images of the study area using ArcGIS 10.5 and ENVI 5.0 software. Data were analyzed using both descriptive and inferential statistics. A total of 60 plant species belonging to 49 genera and 27 families were documented. Most species had mean Diameter at Breast Height (DBH)/Diameter at Stamp Height (DSH) less than 10 cm, few species (four) were in higher diameter classes (27.6–32.5) and only one species (Acacia tortilis) was in the 32.6– 37.5 and 37.5–42.5 diameter classes. Most species (77%) had low importance value index which imply the need for conservation attention in the area. Spatial cover of Lake Abijata decreased by 58.6% as its cover decreased from 20,676.51 ha in 1978 to 8,558.1 ha in 2018. Similarly, grassland, wetland and forest/shrub land decreased by 87.6%, 48.9% and 40.9%, respectively. Human settlements, crop land and bare land increased by 517.7%, 105.1% and 81.1%, respectively. Protected area had higher mean biomass (289 g/m2 ) than the open access sites (71 g/m2). Coordinated and multidisciplinary interventions are recommended to restore the degraded terrestrial and aquatic ecosystems and conserve the diverse biodiversity in the study area. Key words/phrases: Ecosystem restoration, Herbaceous biomass, Land use/land cover change, Species richness
Although the most direct impact of cities on biodiversity is the change in land cover associated with urban growth, large number of species have been recorded to live, and even thrive, within urban centers. The present study was conducted from August 2018 to March 2019 and aimed to investigate the seasonal diversity and habitat association of birds in Bahir Dar city. Semi-forest, wetland, waste dumping site and residential area were habitats identified based on topographic map and ground truthing survey. A total of 100 point count stations within 10 plots of the semi-forest habitat and 550 line transects within 55 blocks of open habitats were used to collect data. Diversity indices, chi-square and ANOVA were employed for data analyses. A total of 186 bird species belonging to 21 orders and 59 families were recorded. The highest diversity of bird species was observed in the residential area during the wet season (H’ = 3.78) and the lowest was in waste dumping site during the dry season (H’ = 2.11). Test of association between season and habitat types as a function of birds’ abundance also confirmed the presence of strong association between season and birds abundance. Availability of food, water and nesting sites were the main players to determine the diversity and abundance of birds within Bahir Dar city. The study area supports large number of bird species that confirms the area’s potential for bird watching tourism. Therefore, there must be a collaborative work with the city administration for protecting the urban ecosystem to conserve the biodiversity therein.
Lake bioassessment is routinely done using one biological community such as macro-invertebrates, diatoms, macrophytes or fish. Theuse of at least two assemblages has been suggested as they are believed to be more robust indicators, because each community responds differently to potential stressors in waters. This study aimed to use macroinvertebrate and diatom assemblages to identify metrics and temperate indices that could discriminate between reference and impacted sites of the littoral zone of Lake Ziway, Ethiopia. The Lake Habitat Quality Assessment (LHQA) method was used to categorize the sites in the littoral zone of the lake. Lake water, macroinvertebrate, and diatom samples were collected from 3 reference and 6 impacted sites between September 2015 and April 2016 with standard methods and following the Ontario Benthos Biomonitoring Protocol. A total of 34 macroinvertebrate taxa and 39 diatom species were recorded. 32 macroinvertebrate and 18 diatom indices were tested for their ability to discriminate between the reference, intermediate and multiple-stressed sites using correlations between metrics, similarity values with SIMPER and boxplots overlaps. Further, correlation of the metrics with physico-chemical parameters extracted metrics and indices with high discrimination efficiency(≥3). The indices remaining were 5 macroinvertebrate (NT, PTI, PETI, PDT and CLI) and 4 diatom (CEE, PTV, TDI, and IBD) indicators which clearly discriminated between the impacted (intermediate and multiple stressors) and reference sites, but not within the impacted sites, in the lake. These data can also possibly serve as core metrics for multi-assemblage index development for this shallow, tropical lake. Key words/phrases: Diatom, Discriminatory efficiency, Lake bioassessment, Macroinvertebrate, Multi-assemblage, Omnidia, SIMPER
