Abstract:
Human activities have potential adverse effects on freshwater ecosystems, which sustain
a wide range of ecosystem services such as the provision of potable water, nutrient
cycling, and a habitat for organisms such as decomposer macro-invertebrates. The effect
of these activities with regard to water quality and invertebrates has been established and
well documented. However, information on the effect of human activities on leaf litter
breakdown as an indicator of river ecosystem integrity is still limited in Kenya. The
objectives of the study were: To determine effect of anthropogenic activity on litter
decomposition rates of Lantana camara, Eucalyptus grandis and Psidium guajava; to
compare leaf litter decomposition rates of the three species and To examine relationships
between leaf litter decomposition rates, macro invertebrate shredders and water quality
parameters. The study employed the litterbag method where dry leaves enclosed in mesh
bags were incubated in the river to measure mass loss decomposition and associated
macro invertebrates. Data was collected from September to December 2018.iThe Physicochemical
characteristics
of
water
measured
in-situ
included
electrical
conductivity
(EC),
pH,
total
dissolved
solids,
dissolved
oxygen
(DO)
concentration
and
temperature.
Further,
water
discharge, velocity, depth and width were determined. Laboratory analyses were
conducted to determine concentration of nitrates, nitrites, total phosphorus and
phosphates. Daily mass loss of the collected bags was determined to assess litter
decomposition rates. Macro invertebrates identified were classified up to family level and
grouped into functional feeding groups. Data was analyzed using R statistical packages.
Findings show that site and plant species had a significant effect (p=0.05) on leaf litter
decomposition rates. Of the three species, Lantana camara had the fastest decomposition
irate while Psidium guajava had the slowest irate of decomposition. Water physicochemical
parameters had both positive and negative correlation with leaf litter
decomposition rates and no macro invertebrate shredders were observed. It is
recommended that future studies should evaluate other human activities (for example,
mining and waste water effluents) and effects of leaf litter mixtures on the decomposition
process.
