THE ECOLOGY OF SOUTH AFRICAN ESTUARIES

Abstract

The topography of Richard's Bay Estuary is described, and an account given of the physical and chemical factors. The estuary is tidal in the channel area, and saline water is present in the Umhlatuzi Lake. There is a normal salinity gradient ranging from 0·3%₀ in the rivers to 35·8%₀ in the mouth. On the basis of these factors the estuary is divided into four regions, namely the Rivers, the Umhlatuzi Lake, the Channel and the Mouth, and the fauna and vegetation of each are described. A total of 183 species was found and is listed in the appendix. It is concluded that Richard's Bay is an example of a normal sub-tropical estuary which has been little influenced by man. The faunistic divisions are discussed and are compared with those of Knysna Estuary on the south coast, and those postulated by Day (1951) for an ideal estuary.