Comparative Study on the Limnological Status of Five Ethiopian Soda Lakes and Land Use Land Cover Changes in their Catchments
| dc.contributor.advisor | Habte Jebessa | |
| dc.contributor.author | Hana Melese | |
| dc.date.accessioned | 2025-08-31T20:28:43Z | |
| dc.date.available | 2025-08-31T20:28:43Z | |
| dc.date.issued | 2024-05 | |
| dc.description.abstract | Soda lakes are productive natural ecosystems with considerable biological and socio-economic importance presently facing threats due to anthropogenic and natural activities. The research was conducted in five soda lakes of Ethiopia: Abijata, Arenguade, Beseka, Chittu, and Shala. The objective of this study was to investigate comparative spatio-temporal variations of physico-chemical properties, biological and Land Use Land Cover (LULC) changes in comparison with their historical data. Physico-chemical and biological data were collected from central (open-water) sampling sites of each lake from January to December 2020, four times in different seasons (Dry, Pre-rainy, Rainy, Post-rainy). All physico-chemical factors exhibited significant differences between seasons (ANOVA, P < 0.05), except the salinity in Lake Shala. The concentrations of physicochemical parameters were generally high during the dry seasons in the studied lakes due to the low incidence of rainfall, caused by recurrent drought, resulting in higher evapotranspiration rates as they are characterized by a long dry season. Lakes Arenguade and Beseka showed considerable decrease in conductivity, alkalinity and salinity, compared to data from the 1960s and 1990s, which might be attributed to dilution effect. The same parameters showed slightly increasing trend in Lake Arenguade which might be due to high evaporation rate. In general, the physicochemical parameters of the study lakes showed temporal variations, which could be attributed to the dilution effect, evaporation, and hydrological characteristics of the Ethiopian Rift Valley. Lake Chittu had the highest chlorophyll-a concentration, followed by Lake Arenguade, Beseka and Shala. Chlorophyll-a concentrations generally increased during the post rainy and dry seasons. The results of multiple linear regression (LR) models were high for lakes Arengude, Beseka and Chittu. Lakes Shala and Beseka had the highest number of phytoplankton taxa, with both taxa composition and abundance dominated by Bacillariophyceae. Cyanoprokaryota, particularly Limnospira fusiformis, predominated in the abundance of lakes Arenguade and Chittu. Water temperature, Secchi depth, turbidity, electrical conductivity, soluble reactive phosphorus, nitrate and silica significantly influenced the phytoplankton community structure. Long-term trend analysis revealed changes in phytoplankton biomass and lake taxonomic composition. The alteration in phytoplankton biomass and species composition of the lakes could be attributed to three factors: frequent high-velocity explosions conducted for seismological studies in the past. This impact may have caused a dramatic increase in lake level in the case of Lake Beseka leading to a drop in nutrient concentration; climate change and salt content. Our findings suggest that phytoplankton composition, biomass, and abundance varied according to seasonal fluctuations, emphasizing the possible effects of anthropogenic and natural causes on their community structure. The greatest numbers of zooplankton were noted for Lake Shala followed by Beseka, Chittu and Arenguade. Rotifers dominated all four lakes in terms of species richness whereas, cladocerans occurred rarely. The abundance of zooplankton in Lake Arenguade and Chittu was high during the wet season (July), while in Lakes Beseka and Shala it was high during the post-rainy (November) and dry seasons (January), respectively. The variations in the abundances of the zooplankton community were significantly explained by water temperature, DO, EC, nitrate, SRP, and turbidity according to Redundancy Analysis (RDA). Land use and land cover (LULC) changes around the catchment of lakes Abijata, Beseka, Chittu and Shala have been significant over the last 40 years, reflecting broader environmental and socio-economic trends. Lake Beseka, agricultural land, and settlement areas have shown a consistent increase in the land use classes within the Lake Beseka catchment. Conversely, there has been a decline in the extent of dry land. Although the natural vegetation in the catchment area has displayed a tendency to grow, it experiences constant fluctuations due to alterations in land use and the expansion of water bodies. There has been an increase in agricultural land and settlements in the region, while dry land in the vicinity of the three lakes (Abijata, Chittu, and Shala) has been decreasing. The sizes of lakes Chittu and Shala have remained fairly consistent with minor fluctuations. Lake Abijata experienced a notable decrease in size between 1984 and 2004, but has since returned to its initial size. These changes were primarily driven by agricultural expansion, deforestation, and the demands for a growing population. This study is the first to record the spatio-temporal variability of physico-chemical properties, plankton and Land Use- Land Cover (LULC) changes in five separate Ethiopian soda lakes. However, there is a need for more comprehensive research that integrates multiple ecological and environmental factors for the sustainable management and conservation strategies. | |
| dc.identifier.uri | https://etd.aau.edu.et/handle/123456789/7206 | |
| dc.language.iso | en_US | |
| dc.publisher | Addis Ababa University | |
| dc.subject | Alkaline | |
| dc.subject | Chlorphyll-A | |
| dc.subject | Abundance | |
| dc.subject | RDA Analysis | |
| dc.subject | Remote Sensing | |
| dc.title | Comparative Study on the Limnological Status of Five Ethiopian Soda Lakes and Land Use Land Cover Changes in their Catchments | |
| dc.type | Thesis |