EFFECTS OF HUMAN ACTIVITIES ON WATER QUALITY AND MACROINVERTEBRATES ALONG NYANGORES STREAM, MARA RIVER BASIN, KENYA

Abstract

The study investigated the effects of human activities on water quality and macroinvertebrates along the Nyangores stream in the upper catchment of Mara River Basin. Seven sampling sites were chosen to correspond to different human activities along the stream. Physico-chemical water quality parameters were measured in situ using measuring probes and nutrients determined calorimetrically using standard methods. Habitat quality was determined using the stream visual assessment protocol. Total coliforms and Escherichia coli were determined using the membrane filtration technique (MFT). Macroinvertebrate samples were collected from February 2012 to July 2012 using a kick net of 500μm mesh size. The relationship between community attributes and physicochemical parameters was determined using Pearson correlation. Canonical correspondence analysis (CCA) was used to describe the relationship between macroinvertebrate community assemblage and the physico-chemical parameters. ANOVA was used to test for variations in physico-chemical parameters and post hoc Duncan’s Multiple Test was used to compare means among stations and sampling period. Results indicated an increase of nutrients and coliform bacteria as human activities intensified. Significant (p<0.05) spatial variations in conductivity, pH, TSS, discharge, NH4, NO3 and NO2 and temporal variations in discharge and TSS were also recorded. There were significant relationships between nutrients, discharge and coliform bacteria. A total of 42 macroinvertebrate genera were encountered with EPT dominating the upstream stations Ephemeroptera taxa dominated followed by Diptera which increased downstream. Most physicochemical parameters determined the structure of macroinvertebrates in the stream. The variation of macroinvertebrates among sites was influenced by temperature, conductivity, nitrites and biological oxygen demand. This results show that water quality and structure of macroinvertebrates is influenced by human activities in the Mara River basin. The author recommends continuous monitoring using macroinvertebrates to assess water quality of the stream. The riparian land use should be controlled and buffer zones established so as to improve habitat quality of the stream.