Rift Valley Lakes Research Articles

Implications of Environmental Pollutions on Ethiopian Fisheries: Review Study

The objective of this review article was to summarize the current impacts and its implications of environmental pollution on the fisheries sector in Ethiopian fisheries. The materials for this review were kinds of literature (published and unpublished) including internet access and personal experiences were used for the source to obtain applicable data. Ethiopia has a potential source of water used for fisheries and irrigation-based agriculture. The Ethiopian Rift Valley is one of the potential sources used for fisheries purposes and it is also the most environmentally vulnerable water source in the country. Climate changes and environmental pollutions affect the fisheries and aquaculture sector directly by influencing the fish stocks and the comprehensive supply of fish for consumption. In Ethiopia, environmental pollutions are significantly affected the fisheries sector, especially in the Rift valley areas which come from different sources. 92.8% of the liquid sewages released from Addis Ababa city enter into rivers and rain-water channels having a chain with Lakes along with the downstream with above the maximum permissible levels of BOD and COD. And, applications of commercial agricultural fertilizers including pesticides and floriculture significantly affected the water qualities of Ethiopian water bodies especially the central Rift Valley lakes and, currently, the affluence and availabilities including the fish quality and the ecosystem services under the down streams are found at risk. The accumulation of nutrients affects biodiversity and fisheries. Under Rift valley lakes, 73% of the fish landing is sold nearby markets and the consumption of fish that are contaminated through different concentrations of heavy metals above permissible levels is going to be toxic for human beings. Therefore, the government and respective bodies should give more emphasis on the mitigations and management’s especially with agricultural, floriculture, and urbanization related waste entered into the water bodies; affects the ecosystem and the fishery sector in the country. Keywords: Environment, pollution, climate change, fisheries, water bodies, Ethiopia DOI: 10.7176/RHSS/11-17-02 Publication date: September 30 th 2021

Water quality assessment, multivariate analysis and human health risks of heavy metals in eight major lakes in Kenya

This study evaluates water quality, concentrations and health risks of heavy metals (HMs) in eight major lakes in Kenya namely Naivasha, Elementaita, Nakuru, Baringo, Bogoria, Turkana, Victoria and Magadi. Water quality was assessed using water quality index (WQI) and pollution evaluation index (PEI), while human health risk associated with ingestion and dermal contact of HMs was assessed using hazard quotients (HQ) and hazard index (HI). Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used to deduce the probable sources of the HMs. The average concentration of aluminium (Al), molybdenum (Mo), manganese (Mn), nickel (Ni), arsenic (As), zinc (Zn), selenium (Se), lead (Pb), chromium (Cr), mercury (Hg), cobalt (Co) and cadmium (Cd) in the eight lakes was 824.6, 66.1, 58.9, 16.2, 8.40, 7.84, 6.91, 4.65, 2.66, 0.86, 0.78 and 0.46, respectively, all in μg/L. Al, Mn, As, and Mo were relatively high in Rift Valley lakes and exceeded the maximum permissible levels for drinking water. Notably, high HM concentrations were recorded at the entry points of rivers and areas with high human activities. Lake Magadi had the highest average WQI of 158.8 followed by lake Elementaita (128.4), Bogoria (79.5), Nakuru (73.3), Turkana (57.6), Victoria (52.3), Baringo (42.6) and Naivasha (25.5). Lake Magadi also had the highest average PEI of 40.0 followed by Elementaita (30.1), Bogoria (16.2), Nakuru (15.7), Victoria (10.8), Baringo (9.57), Turkana (9.53) and Naivasha (5.12). Based on WQI, Lake Naivasha water was excellent for drinking, Lake Victoria, Turkana, Baringo, Nakuru, and Bogoria had good water, but water from Lake Elementaita and Magadi was of poor quality. PEI classified the lakes as minimally polluted except Lake Magadi. Multivariate analysis concluded that Pb, Cr, Ni and Se had anthropogenic sources, mainly agricultural and urban runoff, but other HMs had natural influence. Although the HMs did not pose any health risks through dermal contact, HQingestion was >1 for adults and children consuming water from Lake Elementaita, Nakuru, Bogoria and Magadi due to non-carcinogenic risks associated with As, Zn and Mo. These results are important for formulating the necessary remediation policies to improve water quality in the eight lakes.

Hydroclimatic analysis of rising water levels in the Great rift Valley Lakes of Kenya

Study RegionThe Great Rift Valley lakes of Kenya have recently experienced significant increases in their water levels, negatively impacting the local communities. This has provoked renewed concerns about the causations, with various geological, anthropogenic and hydro-climatic influences hypothesized as potential causes of the water level rises. Study FocusThis study analyses and documents water level fluctuations in Lakes Baringo, Bogoria, Nakuru, Solai, Elementaita and Naivasha. Hydrometeorological analyses are undertaken to understand potential causes and lake volume data is used to derive the “Integrated Catchment Response” (ICR), a magnitude which allows to relate changes in water balance components to signals observed in the lake volume changes. New Hydrological Insights for the RegionCompared to 1984−2009, the recent increases in lake areas range from 21 % for Lake Naivasha to an extraordinary 123 % for Lake Solai. Mean annual rainfall for 2010−2020 increased by up to 30 %. Actual evapotranspiration also increased, but to lesser extent compared to rainfall. The results illustrate that changes in catchment properties due to anthropogenic influences or changes in underground permeability are not necessary to explain the lake level rises. Based on the ICR only surprisingly minor changes in the water balance are necessary to explain the lake level rises, since an increase of only 0.4–2 % of mean annual effective rainfall leads to the observed phenomena.

Spatial-temporal variation, sources and driving factors of organic carbon burial in rift lakes on Yunnan-Guizhou plateau since 1850

Burial of organic carbon (OC) in rift lakes on plateau is an important part of the global cycle. It is affected by natural and anthropogenic factors. In this study, we selected the sediment records of 7 rift lakes on the Yunnan-Guizhou Plateau to study spatial-temporal variation, sources and driving factors of organic carbon burial since 1850. The analysis of the temporal and spatial trend of carbon burial shows that the TOC concentration, TOC flux, C: N and mass accumulate rate have increased significantly since 1850. Co-occurrence network analysis indicated that a strong correlation between the TOC concentration and silty. TOC concentration were identified as core genera due to their high concentration. Carbon isotope tracing results show that before 1950, endogenous OC input played a dominant role, and after 1950, the proportion of exogenous OC increased. Canonical correlation analysis indicated that after 1950, agriculture intensification and population increase become one of the factors affecting the carbon burial of lakes in this area. The result of this study indicate that anthropogenic factors have become the main factors promoting carbon burial in rift lakes on the plateau.

Assessment of morphometric changes in Lake Hawassa by using surface and bathymetric maps

Study regionLake Hawassa, Ethiopian Rift Valley, Southern Region, Ethiopia. Study focusLake Hawassa is one of the major Ethiopian Rift Valley Lakes with an endorheic basin system located near Hawassa town. The Lake water is vital to the surrounding communities for irrigation, domestic water supply, recreation, and fish harvesting. The morphological changes due to flood water from the surrounding agricultural areas were noticed and the water quality deteriorates which will be reflecting the agricultural productivity in the region and negatively impacted the socio-economic development. The lake morphometric changes were investigated by using cartographic ArcGIS mapping and bathymetric mapping and during the analysis, the thermal Infrared data of Landsat ™ was used in the digital elevation model (30 × 30 m) and Google Earth Engine (GEE) platform. The morphometric changes for a period of 46 years were considered in this study. The Secchi discs and echo-sounder were used to during the preparation of bathymetric maps and kriging interpolation was used for the water depth assessment of the lake. New hydrological insights for the LakeThe surface area of the Lake increased by 11.28 % from 1973 to 2019. The depth and volume decreased by 33.04 % and 25.32 %, respectively over the same period. The observed Secchi disc depth was 2.06 m. It was found that the increased surface area due to sedimentation and eutrophication in the Lake.

The stratigraphic evolution of the Lake Tanganyika Rift, East Africa: Facies distributions and paleo-environmental implications

Active continental rifts are ideal sites for understanding the break-up of continents, and long-lived rift lake environments are known as important reservoirs for endemic communities and biodiversity. The sedimentary fill of the Lake Tanganyika Rift records a long history of continental extension and variable tropical climate, that is unparalleled in its duration and fidelity. Recently acquired, state-of-the-art 2D seismic reflection data, together with reprocessed legacy data, are used to evaluate the evolution and distribution of sedimentary facies over the rift lake. Using seismic stratigraphic analysis, we reconstruct past depositional environments and the paleogeography of the lake and assess how tectonic-driven subsidence and hydroclimate variability modified the lake basin. We identify six syn-rift seismic units that overly the acoustic basement and identify depositional units beneath the syn-rift sequence that suggest episodes of pre-rift sedimentation. Based upon the seismic facies analysis, the earliest seismic stratigraphic unit is interpreted as deposited in an early-stage rift system of low-relief, that was dominated by alluvial, fluvial and shallow lacustrine conditions. Subsequent units exhibit attributes of a lacustrine environment of much greater water depth, enhanced catchment relief and accommodation, consistent with a more mature rift. In Seismic units 2–5, we observe extensive deltaic deposits and deep-water fans, and locally canyons, channels, channel-levee complexes, turbidites, slumps and other mass flow deposits. In the latter part of its history, erosional surfaces and abundant lowstand delta facies are observed, indicating the rift experienced dramatic hydroclimate cycles. We assess the relative timing of key features of the rift, including the emergence of major structures and rift segment boundaries, development of major drainages and linkages to upstream rift lakes. The evolving sedimentary facies of the rift illustrate a shallow- to-deep progression of rift valley environments and the more limited littoral habitats that influenced the evolution of its unique endemic organisms.

Streamflow variability and its linkage to ENSO events in the Ethiopian Rift Valley Lakes Basin

Study RegionThe Ethiopian Rift Valley Lakes basin is found in the main Ethiopian Rift Valley system. Study FocusUnderstanding the hydrological impact of El Niño-Southern Oscillation (ENSO) is of a paramount importance for society since it substantially affects the environmental and socio-economic conditions. The relation between ENSO indicators (SOI, MEI and Niño3.4) and streamflow magnitude was statistically evaluated with partial correlation, cross correlation, extreme streamflow indices and streamflow deficits to provide empirical evidence on how ENSO phases (La Niña and El Niño) affect streamflow variability. Trends of streamflow and ENSO indicators were tested using the non-parametric Mann-Kendall test. New Hydrological Insights for the RegionOur findings indicate that the partial correlation between the catchment area and ENSO effect on streamflow were not statistically significant at p < 0.05 after removing the south-north gradient. The direction of the ENSO effect is spatially inconsistent since El Niño (La Niña) causes positive deviation in some catchments and negative deviation for other catchments. Though statistically insignificant, reduced flow is detected for many catchments during El Niño years. For most catchment, the extreme high flow has a larger magnitude during La Niña than El Niño whereas the extreme low flow has a larger magnitude during El Niño than La Niña years. Overall, the relationship between ENSO and streamflow of the study area is found spatially inconsistent and statistically insignificant for most catchments.

Analysing Trends and Spatio-Temporal Variability of Precipitation in the Main Central Rift Valley Lakes Basin, Ethiopia

This study aims to investigate trends and spatiotemporal variability of precipitation during the period of 1980-2015 in the Main Central Ethiopian Rift Valley Lakes Basin. Mann-Kendall (MK) and Sen’s Slope (SS) estimation were used to detect the trends and magnitudes respectively. The Inverse Distance Weighting method was employed for spatial interpolations. The results revealed that the rainfalls had experienced less concentrated and highly variable in the central rift floor. The trend analysis showed that out of 21 stations, 4 stations (Koshe, Bulbula, Kofole and Shashamane) in annual; six stations (Koshe, Bulbula, Tora, Wulberg, Wondogenet, and Shashamane) in spring; and only one station (Shashamane) in summer showed significantly decreasing trends with -4.5 to -15.59 mm/year range. All stations in spring rainfall revealed no positive trends. Conversely, in both annual and summer rainfall statistically significant increasing trends exhibited for Ejersalelle and Adamitulu with 6.4 to 7.94mm/year range. In monthly time scales, the significant decreasing and increasing trends were also investigated for a few stations. Increasing trends could lead to an increase in potential for water resources whereas variability and decreasing trends could boost over-exploitation of water resources. This study would be provided useful information for management of water resources in the study area.

Evaluation of water quality and eutrophication status of Hawassa Lake based on different water quality indices

Lake Hawassa is one of the major Ethiopian Rift Valley Lakes having an endorheic basin system. The surrounding community makes use of the lake water for the multiple purposes of irrigation, domestic water supply, recreation and fish harvesting. The aim of the present study was to ascertain the water quality of the lake in terms of water quality indices (WQI) and its health over a period of three months covering both dry and wet seasons. Overall, the water quality of Lake was unfit and bad as per the weighted arithmetic method (120.06–228.29) and modified Bascarón water quality index (MBWQI) methods (26.81–33.89), respectively. However, the quality was indicated as marginal, as per the Canadian Council of Ministers of the Environment (CCME) water quality index method (44.2–51.1). On average, the lake was under the hypertrophic stage as per the standard based on the results of Secchi depth and nutrient concentration. The current study showed the lake being unfit for all-purposes as per WAWQI range (> 100). According to the physicochemical and biological parameters, of the lake, it requires mitigation measures to control Eutrophication and pollutants inflow.

Multi-source genesis of continental carbonate-rich fine-grained sedimentary rocks and hydrocarbon sweet spots

Abstract This paper systematically discusses the multiple source characteristics and formation mechanisms of carbonate-rich fine-grained sedimentary rocks through the analysis of material source and rock formation. The hydrocarbon accumulation characteristics of carbonate-rich fine-grained sedimentary rocks are also summarized. The results show that the main reason for the enrichment of fine-grained carbonate materials in rift lake basins was the supply of multiple material sources, including terrestrial material input, formation of intrabasinal authigenic carbonate, volcanic-hydrothermal material feeding and mixed source. The development of carbonate bedrock in the provenance area controlled the filling scale of carbonate materials in rift lake basins. The volcanic-hydrothermal activity might provide an alkaline fluid to the lake basins to strengthen the material supply for the formation of carbonate crystals. Authigenic carbonate crystals induced by biological processes were the main source of long-term accumulation of fine-grained carbonate materials in the lake basins. Carbonate-rich fine-grained sedimentary rocks with multiple features were formed through the interaction of physical, biochemical and chemical processes during the deposition and post-deposition stages. The source and sedimentary origin of the fine-grained carbonate rock controlled the hydrocarbon accumulation in it. In the multi-source system, the types of “sweet spots” of continental shale oil and gas include endogenous type, terrigenous type, volcanic-hydrothermal type and mixed source type.

Complete Genome Sequence of Strain SS-5, a Magnetotactic Gammaproteobacterium Isolated from the Salton Sea, a Shallow, Saline, Endorheic Rift Lake Located on the San Andreas Fault in California.

We report the 3.7-Mb genome sequence of strain SS-5, a magnetotactic, sulfur-oxidizing rod and member of the family Chromatiaceae of the class Gammaproteobacteria, which biomineralizes membrane-bound, elongated, prismatic octahedral, magnetite nanocrystals. This genome sequence brings further diversity for understanding the origin and evolution of magnetotaxis and magnetosome biomineralization.

Flooding of Lake Nakuru National Park and Its Effects on the Resident Wildlife

Lake Nakuru is one of Kenya’s Rift Valley Lakes and lies within the Lake Nakuru National Park. As a key habitat for flamingos and other water birds, the lake is a major tourist attraction. Lake Nakuru National Park covers an area of approximately 188 km2 and is fully enclosed with a perimeter fence. The park is home to about 56 different species of mammals, 550 plant species, and 450 species of terrestrial birds as well as flamingos and other water birds. In the last decade, the lake has experienced continuous flooding, increasing the lake area from 35 km2 in 2009 to 54 km2 in 2018. This impacted negatively on the available space for wildlife. The main objective of this study was to investigate the effects of this flooding on the wildlife and their habitats in Lake Nakuru National Park. The methodology used Land use Land cover (LULC) interpretation of Landsat Satellite imagery from two epochs, 2009 and 2018, and integration of the results with relevant wildlife data provided by Kenya Wildlife Service. The results, which include LULC change maps and wildlife distribution maps, have shown that the flooding impacted negatively on the available space for wildlife. In addition, the floods also compromised key park infrastructures such as roads and the main gate making it very difficult to maintain the normal park operations, and hence adversely affecting the local and national economies. The information provided by this study is useful for planning mitigation measures in respect of the current and potential future flooding.

Implications of Environmental Pollutions and Climate Changes on Ethiopian Fisheries: Review Study

The objective of this review article was to summarize the current impacts and its implications of environmental pollution on the fisheries sector in Ethiopian fisheries. The materials for this review were kinds of literature (published and unpublished) including internet access and personal experiences were used for the source to obtain applicable data. Ethiopia has a potential source of water used for fisheries and irrigation-based agriculture. The Ethiopian Rift Valley is one of the potential sources used for fisheries purposes and it is also the most environmentally vulnerable water source in the country. Climate changes and environmental pollutions affect the fisheries and aquaculture sector directly by influencing the fish stocks and the comprehensive supply of fish for consumption. In Ethiopia, environmental pollutions are significantly affected the fisheries sector, especially in the Rift valley areas which come from different sources. 92.8% of the liquid sewages released from Addis Ababa city enter into rivers and rain-water channels having a chain with Lakes along with the downstream with above the maximum permissible levels of BOD and COD. And, applications of commercial agricultural fertilizers including pesticides and floriculture significantly affected the water qualities of Ethiopian water bodies especially the central Rift Valley lakes and, currently, the affluence and availabilities including the fish quality and the ecosystem services under the down streams are found at risk. The accumulation of nutrients affects biodiversity and fisheries. Under Rift valley lakes, 73% of the fish landing is sold nearby markets and the consumption of fish that are contaminated through different concentrations of heavy metals above permissible levels is going to be toxic for human beings. Therefore, the government and respective bodies should give more emphasis on the mitigations and management’s especially with agricultural, floriculture, and urbanization related waste entered into the water bodies; affects the ecosystem and the fishery sector in the country.

Runoff and Sediment Yield Modeling of Meki River Watershed Using SWAT Model in Rift Valley Lakes Basin, Ethiopia

Loss of soil fertility in agricultural lands and sedimentation in lakes of central rift valley of Ethiopia are major watershed problem threatening the agro economy in the area. To develop effective erosion control plans through implementing appropriate soil conservation practices, runoff and sediment yield in Meki watershed was estimated and analyzed using the SWAT model. The model showed the simulated mean annual surface runoff was 114.03mm and the mean annual streamflow was 9.41m³/s. Similarly, mean annual sediment load of 13.12 t/ha enters to Lake Ziway. The model was calibrated and validated on daily and monthly time step for flow and on monthly time step for sediment yield. The results of Nash Sutcliff Efficiency of 0.71 on daily and 0.89 on monthly time steps for streamflow and its value of 0.80 on monthly time step for sediment yield during calibration showed that there is a good match between measured and simulated data for both variables on daily basis and very good match on monthly basis. The potential erosion source areas were identified. Likewise, 51.34% of the watershed area was found to be potential erosion sources and priorized for erosion control plans.

Differences in Phenotypic Characters of Nile Tilapia (Oreochromis niloticus L) in Three Ethiopian Rift Valley lakes; Screening Strains for Aquaculture

Nile tilapia (Oreochromis niloticus L.) is indigenous species to Ethiopia and constitutes major proportion in the country’s fish production. In an attempt to select better performing strains for aquaculture development, tilapia populations from different Ethiopian rift valley lakes showed different growth performances in pond culture. Investigation of desired culture characteristics of target tilapia populations is required to improve their productivity in aquaculture system. The current study was made to investigate phenotypic characters of the tilapia populations in three geographically isolated Ethiopian rift valley lakes (Chamo, Koka and Ziway). A total of 450 adult tilapias of commercial catches were sampled from the three lakes and their phenotypic characters were analyzed during May 2018 to March 2019. Twenty six morphometric character indices, eight meristic counts, total length, standard length, total weight, length-weight relationship and Fulton’s condition factor were considered in the analysis. The results revealed significant differences (p ≤ 0.05) in most of the morphometric character indices, meristic counts, mean length and weight and Fulton’s condition factor among the three tilapia populations. Chamo tilapia population were found to have highest mean values of total weight, total length and standard length while Koka population have highest mean value of Fulton’s condition factor and positive allometric growth as characters desired in aquaculture. Further research is required to investigate whether the fish populations could maintain those characters in pond cultures.

Variations in Reproductive Characteristics among Oreochromis niloticus Populations of Three Ethiopian Rift Valley Lakes

Variations in Reproductive Characteristics among Oreochromis niloticus Populations of Three Ethiopian Rift Valley Lakes

Depositional controls on lacustrine coquinas from an early cretaceous rift lake: Morro do Chaves Formation, Northeast Brazil

The Morro do Chaves Formation is a hybrid sedimentary succession composed of shell beds interbedded with mudstones and sandstones deposited during the rifting process of the Gondwana in a complex lake rift system, forming one of the thickest coquina deposits around the world. Despite being deeply investigated over the last decades in outcrops, the entire stratigraphic organization is not well understood yet, mainly because of the absence of continuous well core data, in addition to challenging geometries and facies distribution of the shell beds. This study focus on the characterization of facies and facies associations, and the development of a conceptual depositional model for the Morro do Chaves Formation, based on the analysis of four continuous well cores and the stratigraphic correlation among them. The described carbonate and carbonate-hybrid rocks are composed mainly of bivalves that form flat shell banks developed during dry periods with low tectonic activity. The siliciclastic rocks (mudstones, sandstones and hybrid rocks) occur interbedded with the carbonate rocks and indicates periods of active tectonic and/or climatic wet periods. The deposits are arranged in a hierarchical organization of 6 m-scale T-R cycles showing aggradation and progradation patterns. The system is controlled mainly by allocyclic (e.g., tectonics and climate) and the autocyclic (e.g., waves and currents) processes. The maximum regressive surface record an important change in the environment with a gradual increase of terrigenous input into the basin until the fast creation of accommodation space for the deposit of extensive shales that drowned and mark the end of the shell bank system. This study on facies, geometries and stratigraphic surfaces adds new and useful knowledge for helping in the understanding of complex coquina reservoirs and is applicable in the exploration of new areas with correlate lacustrine systems.

Mapping mean lake surface from satellite altimetry and GPS kinematic surveys

Lake water height is a key variable in water cycle and climate change studies, which is achievable using satellite altimetry constellation. A method based on data processing of altimetry from several satellites has been developed to interpolate mean lake surface (MLS) over a set of 22 big lakes distributed on the Earth. It has been applied on nadir radar altimeters in Low Resolution Mode (LRM: Jason-3, Saral/AltiKa, CryoSat-2) in Synthetic Aperture Radar (SAR) mode (Sentinel-3A), and in SAR interferometric (SARin) mode (CryoSat-2), and on laser altimetry (ICESat). Validation of the method has been performed using a set of kinematic GPS height profiles from 18 field campaigns over the lake Issykkul, by comparison of altimetry’s height at crossover points for the other lakes and using the laser altimetry on ICESat-2 mission. The precision reached ranges from 3 to 7 cm RMS (Root Mean Square) depending on the lakes. Currently, lake water level inferred from satellite altimetry is provided with respect to an ellipsoid. Ellipsoidal heights are converted into orthométric heights using geoid models interpolated along the satellite tracks. These global geoid models were inferred from geodetic satellite missions coupled with absolute and regional anomaly gravity data sets spread over the Earth. However, the spatial resolution of the current geoid models does not allow capturing short wavelength undulations that may reach decimeters in mountaineering regions or for rift lakes (Baikal, Issykkul, Malawi, Tanganika). We interpolate in this work the geoid height anomalies with three recent geoid models, the EGM2008, XGM2016 and EIGEN-6C4d, and compare them with the Mean Surface of 22 lakes calculated using satellite altimetry. Assuming that MLS mimics the local undulations of the geoid, our study shows that over a large set of lakes (in East Africa, Andean mountain and Central Asia), short wavelength undulations of the geoid in poorly sampled areas can be derived using satellite altimetry. The models used in this study present very similar geographical patterns when compared to MLS. The precision of the models largely depends on the location of the lakes and is about 18 cm, in average over the Earth. MLS can serve as a validation dataset for any future geoid model. It will also be useful for validation of the future mission SWOT (Surface Water and Ocean Topography) which will measure and map water heights over the lakes with a high horizontal resolution of 250 by 250 m.

A new assemblage of Cenozoic lungfishes (Dipnoi: Lepidosirenidae) from the late Oligocene Nsungwe Formation, Rukwa Rift Basin, southwestern Tanzania

Lungfish (Dipnoi) date back to the Devonian, and some fossil taxa as well as extant African lungfishes are known for their ability to aestivate, tolerating low-oxygen environments associated with seasonal drying. Extant lungfishes are separated into two families: Lepidosirenidae (Protopterus in Africa and Lepidosiren in South America) and Neoceratodontidae (Neocerotadus in Australia). African lungfishes were more geographically and phylogenetically diverse on the continent in the past than they are today, with only 5% of extinct taxa recorded from the sub-Saharan fossil record. Given the sparse record of Lepidosirenidae fossils from continental Africa, any new materials are important for understanding diversification of the clade. Here we describe new lungfish fossils cautiously referable to Protopterus annectens and Protopterus aethiopicus, which are strongly supported sister taxa based on the molecular phylogeny. Specimens were collected from the late Oligocene Nsungwe Formation in the Rukwa Rift Basin (RRB) of southwestern Tanzania. The late Oligocene Nsungwe Formation represents a sequence of continental rift-fill deposits of the Songwe sub-basin of the RRB and is subdivided into the lower Utengule and upper Songwe members. Recovery of such material from the Paleogene of Africa below the equator addresses a sizable gap in the lungfish fossil record. It also expands the Nsungwe Formation fauna that includes invertebrates, alestid fishes, ptychadenid anurans, snakes, and several clades of mammals, deepening paleoecological insights into the late Oligocene record of the continental African interior. At present, P. aethiopicus and P. dolloi have an extensive modern eastern African distribution associated with the rift lakes and a region where extant members of P. annectens are not presently known. Fossil specimens described herein document presence of the clade during Paleogene volcanic activity in the western branch of the Eastern African Rift System.

Seasonal effect on the accuracy of Land use/Land cover classification in the Bilate Sub-basin, Abaya-Chamo Basin, Rift valley Lakes Basin of Ethiopia.

A correct and timely land use/land cover (LULC) classification provides indispensable information for the effective management of environmental and natural resources. However, earlier studies mapped the LULC map of Bilate Sub-basin using remote sensing images that were acquired for a single season. Hence, these studies did not consider the seasonal effects on the accuracy of LULC classification. Therefore, the objective of this study was to evaluate changes inclassification accuracy for images acquired during wet and dry seasons in the Bilate Sub-basin. LULC of the study area was classified using the Landsat 8 satellite imageries. Based on field observations, we classified the LULC of the study area into 9 dominant classes. The classification for the two seasons resulted in a noticeable difference between the LULC composition of the study area because of seasonal differences in the classification accuracy. The overall accuracy of theLULC maps was 80%for the wet season and 90% for the dry season with Kappa coefficient values of 0.8 and 0.9 respectively. Therefore, the two seasons showed a significant difference in the overall accuracy of the classification. However, we discovered that when the classification accuracy was tested locally, that is for individual pixels, the results were not the same. In Bilate Sub-basin, several pixels (14.71%) were assigned to different LULC classes on the two seasonsmaps while 85.29% of the LULC classes remained unaltered in the two maps. According to the classification results, the season had a noticeable effect on the accuracy of LULC classification. This suggests that for LULC classification, multitemporal images should be used rather than a single remote sensing image.