Developing a taxa‐related physical habitat score based on the response of macroinvertebrate community structure to fine bed sediment composition in the Tsitsa River, Eastern Cape, South Africa

Abstract

AbstractBiomonitoring techniques such as the South African Scoring System version 5 (SASSv5) is widely used in South Africa to rapidly assess river water quality, but there are currently no equivalent rapid monitoring tools for fine sediment assessments. This article presents a tool that monitors the effects of fine sediment on macroinvertebrates that can be used alongside the SASSv5 assessment. Sampling was carried out in the Tsitsa River in the Eastern Cape province of South Africa. Five sampling surveys were conducted over one hydrological year to capture a range of flow conditions resulting in a total of 90 sampling points across five sampling sites. Using an adaption of the SASSv5 methods, sampling was undertaken at a quadrat scale, rather than at a site scale, to identify macroinvertebrate families in different habitat types and degrees of sediment deposition. Fine sediment sampling using a disturbance technique was undertaken immediately upstream of 78 of the biological sampling points. A taxa‐related sediment deposition score was created in which taxa were scored in terms of their sensitivity to fine sediment accumulation. The index was tested as a monitoring tool at 11 monitoring sites along the Tsitsa River in different seasons and flow conditions in 2019 and 2020.