Marine–estuarine connectivity, salinity and sedimentation in the St Lucia system, South Africa, following reconnection with the uMfolozi River

Abstract

This study reviews selected physical and biotic responses of the St Lucia estuarine system to the recently implemented management approach of re-establishing the connection between the uMfolozi River and the St Lucia Estuary. This connection was severed in the 1950s to reduce high sediment inputs into the estuary, depriving the estuarine system of freshwater, as the management approach was to keep the river and estuary separate. In 2012, after a prolonged period of drought, the uMfolozi River was reconnected with the estuary. This brought freshwater into the system and prevented desiccation of Lake St Lucia under prolonged drought conditions. However, the reconnection came at the cost of excessive sediment accumulation in the St Lucia Estuary and Narrows, as well as the compaction of that sediment due to the prolonged closure of the mouth for over a decade. As saline water has not penetrated Lake St Lucia following the resumption of marine connectivity through the St Lucia Estuary in January 2021, the estuarine lake may soon be prematurely transformed into a freshwater coastal floodplain wetland. Modifications of the current management approach are urgently required to postpone this scenario.