Browsing by Author "Njiru Murithi James"

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  • Publication
    Publication
    Spatial and temporal distribution and diversity of zooplankton along a salinity gradient between the Lake Naivasha and the Lake Oloiden
    (Journal of Technology & Socio-Economic Development, 2023-07-07) Carolyne, Guto Kerubo; Njiru Murithi James; Getabu Albert; Gichana Moraa Zipporah
    There has been an increase in the water level in the Lake Naivasha (fresh water) which led to its merging with Lake Oloiden (saline). This was due to the increase in rainfall: associated with climate change. This may have an impact on the zooplankton community (biodiversity) due to the salinity gradient that resulted. A study was conducted to investigate the spatial and temporal distribution and diversity of zooplankton along a salinity gradient between the Lake Naivasha and the Lake Oloiden. The salinity was measured insitu using a YSI Multiparameter meter and zooplankton were sampled twice by towing a zooplankton net with a flow meter for 10 minutes (monthly, per site for one year). The zooplankton were identified and analyzed under a compound microscope (×100). The species diversity, evenness and species richness index were computed. The salinity was higher in Oloiden ST1 and ST2 as compared to the rest of the sites while the correlation showed a slight positive association between salinity and zooplankton numbers. A total of 17 species were identified and they belonged to the following families: Branchionidae, Lecanidae, Trichocercidae, Sisidae, Daphnidae and Cyclopoidae. The density (Ind/l) was highest for daphnidae, cyclopoidae and sisidae; however, Lake Oloiden had a lower density as compared to the rest of the sites. The diversity index was low; H’= 0.87 for Oloiden ST2 and H’=0.64 for Crescent. Species richness (d) was highest (2.84) for Oloiden ST2 and lowest in Crescent (1.24). Species evenness was highest in Crescent (0.83) and lowest in Oseria (0.71). The diversity index, evenness and Margalef’s index was higher in Lake Oloiden as compared to Lake Naivasha. The salinity gradient had an impact on the distribution and diversity of zooplankton; species diversity, evenness and species richness increased with increase in salinity.
  • Publication
    Publication
    Spatial and temporal variation in water quality between the Lakes Naivasha and Oloiden in the Kenyan Rift Valley
    (Journal of Technology & Socio-Economic Development, 2023-07-06) Carolyne, Guto Kerubo; Njiru Murithi James; Getabu Albert; Gichana Moraa Zipporah
    Lakes Naivasha and Oloiden merged due to the rise in the water level in the former. A study was conducted for one year in an endeavor to investigate spatial temporal variation of select physical and chemical parameters between the Lakes Naivasha and Oloiden. The water quality was sampled monthly in each site in Lake Oloiden and Lake Naivasha by measuring some water quality variables insitu and collection of water samples for laboratory analysis. The water depth and the secchi depth were measured in each site while some physicalchemical parameters were measured insitu using a YSI Multiparameter probe. Nutrients (phosphates and nitrates), total suspended solids, chlorophyll-a analysis was done in the laboratory using the standard methods. The lakes depth and the secchi depth have increased in both lakes. The phosphates varied site-wise and chlorophyll-a concentration has decreased post water level rise. Lake Oloiden’s temperature, pH, conductivity and salinity were higher as compared to the Lake Naivasha’s. The principal component analysis showed 4 principal components (PCA-1 to PCA-4) which accounted for 94.7% of the variation. PCA-1 and PCA-2 biplots suggested: a link between chlorophyll-a to orthophosphates, nitrates, phosphates (Oloiden ST1 and ST2). Oseria and Korongo sites were closely associated with the secchi depth, lake depth, pH and salinity. 4 distinct clusters were noted: Crescent, Malewa, midsection (Midlake, Korongo, Oseria) and Lake Oloiden (Oloiden ST1 and ST2). The increase in the water level and the merging of saline and fresh water ecosystem led to the creation of a salinity gradient; an area where abiotic and biotic processes are non-linear. There was spatial temporal variation in water quality among the sites. Analysis of variance in water quality in the Lake Naivasha and Lake Oloiden provided an insight about water quality status: associations between water quality variables and sites may aid in effective management decisions.