Diatom community structure and relationship with water quality in Lake Sibaya, KwaZulu-Natal, South Africa

Abstract Monitoring of wetland ecosystems is crucial as these ecosystems provide numerous services and resources to both humans and the biota found therein. Wetlands are characterised by variations in inundation time and depth and therefore it is often difficult to make use of invertebrates and fish as biological indicators. Diatoms may be used for monitoring of wetland ecosystems as they are widely distributed, are microscopic with few habitat restrictions, communities are species rich and they respond rapidly to environmental changes. Very little information is available on wetland diatom communities in South Africa. Wetland ecosystems include Ramsar sites such as Lake Sibaya which faces increased forestry and rural development within the lake's catchment area. Therefore, this study aimed to determine the diatom community structure of Lake Sibaya and its response to changes in water quality. Water and diatom samples were collected from four sites in Lake Sibaya during August 2015, December 2015 and February 2016. All samples were collected and analysed according to standard methodologies. From the results it was clear that the lake had a lower diatom diversity than that described in a previous study in 1966, with Cocconeis placentula, Gomphonema sp., Epithemia adnata and Nitzschia sp. being the dominant taxa. Both the diatom community structure and measured water quality parameters showed the lake to be nutrient enriched. However, as nutrients accumulate in wetlands it is unknown whether the increased nutrients arise from anthropogenic disturbances or natural sources.