Diatom-based reconstruction of salinity in Lake St. Lucia, South Africa: A Holocene climate history

Coastal water bodies on the east coast of South Africa contain sedimentary deposits that provide potential archives of long-term, high-resolution climate change. Lake St. Lucia, on the north coast of KwaZulu-Natal, is the largest coastal lagoon system in South Africa and has international recognition as a UNESCO World Heritage Site. The St. Lucia system evolved from fluvial origins and today is underlain by a intricate network of buried river channels that reflect almost continual deposition since the start of the Holocene. Recorded data for the last 50 years show that St. Lucia has been subject to extreme salinity fluctuations driven by drought and flood events. Hence, the environmental sensitivity of St. Lucia to climate-driven water balances makes it an ideal site to investigate changes in salinity associated with palaeoclimate variability. Two 15.9 m cores have been extracted from the Lake St. Lucia in order to provide a detailed account of the hydrological cycle during the Holocene. One core was obtained from False Bay and the other from North Lake and provided a basal age of ca. 8300 cal yrs BP, and ca. 7000 cal yrs BP, respectively. The main focus of this study is to present a high-resolution reconstruction of the salinity history of Lake St. Lucia using diatoms, in order to understand the hydrological evolution of this system. Findings from this research will contribute to a larger multiproxy study that aims to provide a more detailed understanding of the characteristics and timing of palaeoenvironmental change in the summer rainfall zone of South Africa.