Mid-Late Holocene palynological development at Lake St Lucia, KwaZulu-Natal

Abstract

Palynological studies were done on lacustrine core sediments in the Indian Ocean Coastal Belt Biome of KwaZulu-Natal, eastern South Africa, that were deposited during the last ∼6300 cal yrs BP in the Mkuze River delta that drains into the northern-most part of Lake St Lucia. The aim was to reconstruct the past vegetation and to infer past climate fluctuations as well as human disturbances to complement growing evidence from other disciplines about these aspects in the area. Palynological results show a dominance of Poaceae (20–50%) suggesting the consistent presence of grassy woodland. Podocarpus pollen dominated the arboreal spectra from 6300 to 2600 cal yrs BP. Thereafter Spirostachys pollen dominated the arboreal pollen spectra for the last 2600 cal yrs BP indicating a change from a forested environment to a more open woodland environment caused by a drop in moisture content (humidity). The results also show that the mid Holocene was humid and warm with high precipitation (freshwater conditions) coinciding with raised sea levels. The late Holocene was warm and dry with some marine influence with more seawater flowing into the estuary and lake due to high evaporation and low fresh water supply caused by drought. Similar pollen fluctuations were observed in records from Lakes Eteza and Sibaya, also located within the Indian Ocean Coastal Belt Biome. The presence of Pinus pollen at the top of the profiles suggests the onset of European settlement when pines were introduced for timber production.