Assessment of the Tyhume river health status using macroinvertebrates as indicators

Ten sampling sites were selected along the Tyhume River corresponding to the upper, mid and lower reaches of the River. In total 48 families were collected during the study. The study observed different types of macroinvertebrate taxa; very low tolerant to pollution (e.g Heptageniidae; Notonemouridae; Perlidae), moderately pollution-tolerant (e.g. Caenidae; Chlorolestidae; Tricorythidae) and very tolerant of polluted conditions (e.g. Chironomidae; Muscidae; Oligochaetae). Both univariate and multivariate analyses were done using PRIMER V6. Above Confluence (ABCON, Site 10) had the highest number (37) of species while Mtloko (MTLOK, Site 2) had the lowest number (24) (Chi-square = 0.87; p 0.05) across sites. No significant difference was observed in the ASPT scores across the 10 sites (F = 0.75; df = 9.60; P > 0.05). Site 4 had the highest mean ASPT Scores with mean of 7.6), whereas the lowest. Three biotopes types, namely: stone, vegetation, gravel-sand-mud, stone and vegetation being the dominant biotopes at the 10 sites. The cluster analyses showed that macroinvertebrates were dependent on biotope preference while stone biotope showing greater macroinvertebrate densities. Euclidean distance of site classification with respect to physico-chemical parameters showed very low stress value (0.01) implying that physico-chemical parameters influenced species distribution within each sampling site. The results also showed that good health conditions existed at the most upstream sites than the lower reaches of the river, thus, indicating impacts of pollution within the river