Browsing by Author "Mathooko, J. M."

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Benthic Macro-invertebrate Diversity and Biomass Distribution in Relation to Canopy Cover and Organic Matter in River Njoro, Kenya
(Egerton University, 2013-01-01) Mathooko, J. M.; M’Erimba, C. M.; Mbaka, J. G.
Field experiments to quantify benthic macroinvertebrate density, diversity and biomass and benthic organic matter (BOM) content in the River Njoro, Kenya, were conducted between January 2009 and April 2009 at four sites with varying canopy cover intensities: Njoro upstream with more than 90% canopy cover, Tree-tops with more than 60% canopy cover, Mugo with more than 50% canopy cover and Mill House with less than 1% plant cover. The sites were approximately more than one kilometre apart. Ten random samples for macroinvertebrate and benthic organic matter quantification were collected from every site using a Hess sampler during each sampling occasion. In the laboratory, all samples were washed through a series of sieves to separate extraneous materials from animals. Animals were sorted under a dissecting microscope, identified and enumerated. Collected litter was sorted into four categories: leaves, fruits, wood and plant fragments. There were significant positive linear correlations between plant particulate organic matter and macroinvertebrate density (Correlation analysis: r = 0.89, P < 0.05), diversity (r = 0.80, P < 0.05) and biomass (r = 0.79, P < 0.05). In conclusion, it can be said that plant particulate organic matter had a positive effect on the macroinvertebrate density, diversity and biomass. Removal of riparian vegetation from the banks of the River Njoro would alter the quantity of litter inputs to the river with attendant consequences to the energy budget of biocoenoses in the ecosystem.
Characterization of Microbial Health Risk at Water Abstraction Points along River Njoro, Kenya
(Egerton University, 2013-01-01) Yillia, P. T; Kreuzinger, N; Mathooko, J. M.; Ndomahina, E. T.
U.S. based models for recreational water quality were applied to characterize the potential health risk (PHR) of infection with gastroenteritis (GI) and highly credible gastroenteritis (HCGI) illnesses from single exposure at several water abstraction points (WAPs) along the River Njoro in rural Kenya. Ambient geometric mean densities of Escherichia coli (EC) and intestinal enterococci (IE) were generally high (2–4 log units of cfu/100ml) and risk levels were grossly in excess of acceptable health risk (AHR) levels for bathing and drinking. PHR was 2–3 times higher with the Cabelli (IE) model compared to the U.S. EPA (EC) model. Risk levels varied among WAPs in concomitance to the spatial and seasonal variability of ambient EC and IE densities. With the Cabelli (1983) IE model, PHR of HCGI illness on single exposure to the dry weather 95th percentile IE density for bathing was 2.5% of the exposed population at Logoman compared to 5.2% at Turkana Flats, 4.9% at Kenyatta or Nessuit and 4.6%, 4.5% and 4.2% at Treetop, Segotik and Njoro Bridge, respectively. PHR was ≥ 5% on exposure to the wet weather 95th percentile IE density at all WAPs, excepting Treetop with 4.3%. Relative risk levels increased by at least 30 and 70 times for GI and HCGI illnesses, respectively, from drinking (250ml) raw stream water, rising erratically in wet weather by > 80% of the dry weather risk at Logoman, > 30% at Njoro Bridge and Kenyatta and 10–15% at Segotik, Nessuit and Turkana Flats. By stipulating freshwater bathing water quality guidelines of 126 and 33 cfu/100ml for EC and IE, respectively, U.S. EPA upholds maximum AHR levels at 0.7% and 1.9% for EC and IE, respectively. Hence, reducing current PHR levels at the WAPs to the U.S. EPA bathing AHR levels would require at least 2–4 log reductions of IE and EC densities with even further log reductions to achieve the WHO recommended drinking water AHR level of 0.1%. This would necessitate specialized treatment, in particular point-of-use treatment at the household level, as well as the implementation of comprehensive catchment management measures to protect the stream and the WAPs.