Browsing by Author "Omondi, R."
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Publication Effects of some abiotic and biotic factors on the zooplankton community in Lake Baringo, Kenya(Semantic Scholar, 2014-10-01) Omondi, R.Lake Baringo is a turbid lake that lies in a closed drainage basin of the Kenyan East African Rift Valley. The lake’s water qualit sedimentation from its catchment arising from poor agricultural practices, deforestation and overgrazing. Its fishery has also declined since the 1980s and frequent lake closures to fishing activities have not alleviated the problem. This shows that there may be other critical ecological and environmental factors affecting the ecosystem. To understand problems facing the lake, there is need for well-coordinated and comprehensive ecological investigations considering the complexity of the ecosystem. Zooplankton is important in energy transfer from primary producers and constitute a significant component of the diets of the juveniles and some adults of many fish species. The objective of the present study was to determine the effect of some physical, chemical and biological factors on the spatial and temporal distribution, abundance and biomass of zooplankton in Lake Baringo. Stratified random design was used to allow for statistical comparison between zooplankton abundance and biomass at different stations and months with environmental factors using Analysis of Variance (ANOVA). The relatively stable environmental factors across the sampling stations in the lake were attributed to its small size, shallowness and the daily mixing by wind action. A total of 39 species of zooplankton belonging to Rotifera, Cladocera and Copepoda groups were recorded. The results indicate that distribution, diversity, abundance and biomass of zooplankton were influenced by environmental factors especially depth, conductivity and turbidity. Diel vertical distribution of zooplankton was the reverse of what is reported from clear lakes with organisms congregating to the surface during the day and descending to the bottom at night. Investigations into the diet of three main fish species in the lake showed that Oreochromis niloticus baringoensis mostly depended on algae, Clarias gariepinus depended on fish while Protopterus aethiopicus thrives on molluscs as their dominant food. The growth performance of the once dominant endemic fish, O. niloticus baringoensis could be affected by the high turbidity, which reduces primary production. Moreover, reduced clarity hampers the feeding success of this visual feeding fish and has decreased macrophytes to near extinction. There is urgent need for rehabilitation of Lake Baringo and the study recommend afforestation and reduction of livestock numbers in the catchment as some of the ways of reducing soil erosion and sediment input in the lake. The results of the study may be used as an important tool for the detection of stability and trophic levels of the ecosystem and to provide data for models on maximal resource production of the lake.Publication Effects of some abiotic and biotic factors on the zooplankton community in Lake Baringo, Kenya(Academic Journals, 2014-05-01) Omondi, R.Lake Baringo is a turbid lake that lies in a closed drainage basin of the Kenyan East African Rift Valley. The lake’s water qualit sedimentation from its catchment arising from poor agricultural practices, deforestation and overgrazing. Its fishery has also declined since the 1980s and frequent lake closures to fishing activities have not alleviated the problem. This shows that there may be other critical ecological and environmental factors affecting the ecosystem. To understand problems facing the lake, there is need for well-coordinated and comprehensive ecological investigations considering the complexity of the ecosystem. Zooplankton is important in energy transfer from primary producers and constitute a significant component of the diets of the juveniles and some adults of many fish species. The objective of the present study was to determine the effect of some physical, chemical and biological factors on the spatial and temporal distribution, abundance and biomass of zooplankton in Lake Baringo. Stratified random design was used to allow for statistical comparison between zooplankton abundance and biomass at different stations and months with environmental factors using Analysis of Variance (ANOVA). The relatively stable environmental factors across the sampling stations in the lake were attributed to its small size, shallowness and the daily mixing by wind action. A total of 39 species of zooplankton belonging to Rotifera, Cladocera and Copepoda groups were recorded. The results indicate that distribution, diversity, abundance and biomass of zooplankton were influenced by environmental factors especially depth, conductivity and turbidity. Diel vertical distribution of zooplankton was the reverse of what is reported from clear lakes with organisms congregating to the surface during the day and descending to the bottom at night. Investigations into the diet of three main fish species in the lake showed that Oreochromis niloticus baringoensis mostly depended on algae, Clarias gariepinus depended on fish while Protopterus aethiopicus thrives on molluscs as their dominant food. The growth performance of the once dominant endemic fish, O. niloticus baringoensis could be affected by the high turbidity, which reduces primary production. Moreover, reduced clarity hampers the feeding success of this visual feeding fish and has decreased macrophytes to near extinction. There is urgent need for rehabilitation of Lake Baringo and the study recommend afforestation and reduction of livestock numbers in the catchment as some of the ways of reducing soil erosion and sediment input in the lake. The results of the study may be used as an important tool for the detection of stability and trophic levels of the ecosystem and to provide data for models on maximal resource production of the lake.Publication Lake Turkana: World’s Largest Permanent Desert Lake (Kenya)(Springer Nature, 2016-08-25) Ojwang, W. O.; Obiero, K. O.; Donde, O. O.; Gownaris, N.; Pikitch, E. K.; Omondi, R.; Agembe, S.; Malala, J.; Avery, S. T.Located in the “cradle of mankind” of the East African Rift Valley, Lake Turkana is distinguished as both the world’s largest permanent desert lake and alkaline water body. With a surface area of about 7,560 km2, Lake Turkana is a highly pulsed, variable system as a result of its closed-basin nature, arid surroundings, and its strong dependence on River Omo for the majority of its inflow, which originates as rainfall over the Ethiopian highlands. In this article we describe the lake’s unique ecosystem and associated vicissitudes, diverse habitats and incredible biodiversity, and ecosystem services. Although parts of the lake and lower Omo Delta have been zoned as an international biosphere reserve, Lake Turkana and the region are facing immense threat from anthropogenic activities. A combination of external factors (hydropower dams, irrigation schemes, climate anomalies) and internal drivers (demography, economic growth) will strongly impact the Lake Turkana basin over the next decade. In turn, this will have significant negative consequences on resource productivity and the wellbeing of local communities.Publication Lake Turkana: World’s Largest Permanent Desert Lake (Kenya)(Springer, Dordrecht, 2016-08-22) Ojwang, W. O.; Obiero, K. O.; Donde, O. O.; Gownaris, N.; Pikitch, E. K.; Omondi, R.; Agembe, S.; Malala, J.; Avery, S. T.Located in the “cradle of mankind” of the East African Rift Valley, Lake Turkana is distinguished as both the world’s largest permanent desert lake and alkaline water body. With a surface area of about 7,560 km2, Lake Turkana is a highly pulsed, variable system as a result of its closed-basin nature, arid surroundings, and its strong dependence on River Omo for the majority of its inflow, which originates as rainfall over the Ethiopian highlands. In this article we describe the lake’s unique ecosystem and associated vicissitudes, diverse habitats and incredible biodiversity, and ecosystem services. Although parts of the lake and lower Omo Delta have been zoned as an international biosphere reserve, Lake Turkana and the region are facing immense threat from anthropogenic activities. A combination of external factors (hydropower dams, irrigation schemes, climate anomalies) and internal drivers (demography, economic growth) will strongly impact the Lake Turkana basin over the next decade. In turn, this will have significant negative consequences on resource productivity and the wellbeing of local communities.Publication Soda Lakes of the Rift Valley (Kenya)(Springer, 2017) Agembe, S.; Ojwang, W.; Olilo, C.; Omondi, R.; Ongore, C.Soda lakes are alkaline with pH values ranging from 8 to 12 and characterized by high concentrations of principal ions such as Na+, HCO−, CO32− and Cl−. Kenya is endowed with many soda lakes forming part of the East African Rift Valley system and includes lakes Bogoria, Nakuru, Elementeita, and Magadi. In addition, Lake Turkana is located on the Kenya-Ethiopian border further north and is described in a separate chapter in this volume. These lakes are characterized by steep fault escarpments, deep gorges, canyons, and craters on the rift floor, some of which have gushing geysers and hot springs. Historically, the lakes were thought to have been one continuous system called Lake Kamatian. Reconstruction of the history of the four lakes based on dated sedimentary time-series data reveal unique hydrological, ecological, and species richness trends that have fluctuated through time between alkaline and freshwater conditions.Publication Spatial and Temporal Variations of Zooplankton in Relation to Some Environmental Factors in Lake Baringo, Kenya(Pan Africa Journal of Sciences, 2015-09-11) Omondi, R.; Yasindi, A.; Am, MaganaThe zooplankton community of Lake Baringo, a shallow and turbid lake in the eastern arm of the Great Rift Valley in Kenya, was studied between April 2008 and November 2009. This study focused on the spatial and temporal distribution, composition and abundance of zooplankton in the lake. Physicochemical variables measurements and triplicate zooplankton samples were taken monthly from five stations. The zooplankton community comprised 31 species. Only two Copepod species, Thermocyclops consimilis and Thermodiaptomus galebi were recorded in the orders Cyclopoida and Calanoida respectively. Cladocera was represented by 8 species, with Diaphanosoma excisum being the most common in all sampling stations. Rotifera, with five families, had a total of 21 species. Spatially, species diversity ranged from 0.649 in C2 to 0.695 in C1 while temporally these were 0.36 to 0.87 in September 2009 and June 2008 respectively. The mean zooplankton abundance per station varied from 27.46±4.16 individuals l-1 in December, 2008 to 120.13±17.50 individuals l-1 in November 2009. Among sampling sites, C3 had the highest abundance (79.09±7.95 individuals l-1) and the lowest abundance was recorded at C1 (56.37±6.58 individuals l-1). There was significant difference between the sampling stations (P<0.001) and among the sampling months (P<0.001). A number of environmental parameters were correlated with the abundance of different species of zooplankton. Key words: Lake Baringo, Zooplankton, Distribution, Abundance, Environmental factors