Contributions of Anthropogenic Activities to Leaf Litter Decomposition in River Kapingazi, Embu County, Kenya

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.