Physico-chemical characteristics of water and sediment of pans in the western Free State and the bioaccumulation of toxicants

M.Sc. (Aquatic Health)Wetlands play an extremely important role in the hydrological cycle as well as biodiversity. Until recently, however, wetlands in South Africa have been neglected both in terms of research and monitoring. The lack of knowledge is even greater for the inward draining wetlands, which is better known as pans. Pans are isolated aquatic systems, which are quite shallow and do not have an outlet. Pans receive water from precipitation and surface runoff, and lose water mainly through evaporation. Some pans can be ephemeral (dry up often) and other perennial (dry up only during drought). The little ecological knowledge available is mainly focused on these ephemeral pans. In this present study conducted in the Western Free-State province, study was only focused on the perennial pans in this area. Due to the fact that this province are one of the biggest areas for gold mining in the country, the pans suffer under the impacts, and this results in the alteration of community structures in and around the pan, simplifying food chains which can lead to the collapse of an ecosystem. The aim of the study was to assess the water quality, bioaccumulation of toxicants (metals and pesticides) in sediment and aquatic invertebrate community of perennial pans in the Western Free State Province, mainly because of the lack of literature on pans in these areas. Seventeen pans were selected for the study of which eight were classified as saline eutrophic and nine as alkaline dystrophic. Various physico-chemical and sediment characteristics were assessed in addition to the characterization of the aquatic invertebrate communities. It became clear that there is great difference in the physical-chemical characteristics of the selected pans. The difference in the trophic state was the most clear, with differences in water colour, nutrient concentration and vegetation growth, classifying pans as either saline eutrophic or alkaline dystrophic. These trophic states influence the distribution and richness of aquatic invertebrates in certain pans. Mining activity, urbanization, agricultural activities and sewage runoff into the pan, all affects the pans negatively, there is sighs of water quality degradation as well as changes in the community structure of invertebrates when compared to the reference pans