St Lucia Drought Macrobenthos

The St Lucia estuarine lake complex is the largest of its type in Africa and is characterised by large scale natural physico-chemical spatial and temporal fluctuations. Ecologically, this estuarine complex functions as an important nursery area for fish species and invertebrates too, making use of a number of different habitat types and associated environmental conditions. The system has been subject to a number of natural episodic events such as cyclonic flooding and cyclical droughts, the most current has persisted since 2001 and has resulted in mouth closure for extended periods. Furthermore, high levels of evaporation have reduced lake levels and resulted in compartmentalisation of the system for up to several years at a time. St Lucia is sensitive to evaporation and therefore is also subject to vast salinity fluctuations and hypersaline conditions. The upper reaches in North Lake are particularly sensitive to drying out and extended hypersaline events (up to 250 ppt in recent years). The macrobenthos has been well studied, but no studies have concentrated on the system as a whole for such an extent of time. The numbers and types of macrobenthic species present are an indication of the health and functioning of the system. Macrobenthic samples were initially collected in 2004, again in 2005 and biannually from 2006 to 2008. Given the importance of this estuary to South Africa and the gravity of the conditions within the estuary, in 2009 the project was extended for an additional three years to continue monitoring the ecological responses to prolonged drought.