Spatial and Temporal Variations in the Distribution of Benthic Macroinvertebrates Along the Vuvu River, South Africa

Abstract

Benthic macroinvertebrates are widely known as important organisms for biomonitoring of water quality due to their visibility to the naked eye, ease of identification, rapid life cycles and sedentary habits. The aim of the study was to assess the condition or health of the Vuvu River using the South African Scoring System (SASS) Version 5 Biomonitoring Method for Rivers. This was achieved by determining the abundance and diversity of benthic macroinvertebrates, and also assessing the influence of water quality parameters on the distribution of benthic macroinvertebrates along the Vuvu River. Samples were collected and identified at the Vuvu River, Elundini Area in the Mount Fletcher district over a period of three months. Water quality parameters, which included dissolved oxygen, temperature, pH and electrical conductivity, were also measured in situ. The three-way analysis of variance (ANOVA) showed that benthic macroinvertebrates were more diverse upstream than at the downstream sites. Results on biotope level revealed that Stones-In-Current (SIC) had significantly higher macroinvertebrate diversity than Gravel Sand and Mud (GSM) with the former being twice the number of benthic macroinvertebrates than the latter. Electrical conductivity showed no significant differences among sites and throughout the sampling period. Although there was a significant increase in mean temperature from July to October which also increased downstream, there was no noticeable relationship between macroinvertebrate distribution and temperature changes. pH values increased downstream and varied from 8.22 to 9.35, indicating alkaline condition. These results serve as baseline information about the condition of the Vuvu River and that benthic macroinvertebrates can be used as monitors of the river ecosystem.