About
South African rivers are threatened by flow and nutrient-related changes due to increasing human pressures and factors such as increased sewage effluent return flows, increasing agricultural runoff and the drier conditions predicted by global climate change, which may decrease dilution potential. Besides threats to biodiversity, unmanaged exploitation of rivers reduces their resource value and consequently both social and economic development. Periphyton, or benthic algae found on riverbeds plays a key role in rivers by converting nutrients into food for invertebrates, which are themselves food for predators, including fish and birds. Periphyton therefore provides a considerable portion of the energy required for the maintenance of the rest of the ecosystem. The biomass and community structure of periphyton in rivers is maintained by an intricate balance between key drivers, particularly nutrient availability and hydrological disturbance. Consequently, periphyton is particularly responsive to both flow and nutrient alterations in rivers and therefore provides an ideal tool for predicting the flow and nutrient characteristics necessary to maintain ecosystem health or integrity. Furthermore, the rapid response of periphyton communities to flow and nutrient alterations makes it an ideal component of the ecosystem for monitoring ecosystem health and consequently applying adaptive management interventions where resource objectives are not being met.

This project will develop and test cost effective and user-friendly tools that are particularly sensitive to flow and nutrient alterations in rivers and are therefore ideal for setting resource quality objectives, monitoring compliance and then informing adaptive management solutions. This research will therefore improve our ability to manage rivers more effectively and thus maintain their resource value such that goods and services provided by these systems can be sustained. This outcome has a direct positive effect on both society and the economy. Also, understanding the role of periphyton communities in the maintenance of river ecosystem integrity will positively impact on the biodiversity value and protection of river ecosystems. The tools and protocols developed will be directly applicable to aquatic ecosystem health monitoring, including providing a potential direct input to the Ecological Reserve process.

Status
Complete

Outputs

• Ewart-Smith J and King J. 2012. The relationship between periphyton, flow and nutrient status in South-Western Cape foothill rivers and the implications for management. Water Research Comission Report 1676/1/12
• Ewart-Smith J, Graham M, Pillay P and Singh S. 2017. The application and development of periphyton as indicators of flow and nutrient alterations and the establishment of trophic status thresholds for water quality monitoring and management of rivers in South Africa. Water Research Commission Report K5/2351
• Grainger, C.V. (2017) Patterns in periphyton biomass and community structure in foothill rivers: A comparison between winter and summer rainfall regions. MSc thesis. AgriSciences, Stellenbosch University
• Ewart-Smith J, Ross-Gillespie V, Grainger C. 2019. Towards the use of periphyton as indicators of flow and nutrient alterations for the management of water resources in South Africa. Water Research Comission Report TT 784/18