A study to determine the levels of nitrogen fixation in the aquatic system of Lake Kariba.There is very little information about nitrogen fixation in tropical lakes in general and even less in tropical man-made lakes (Thornton 1986. Wetzel 1983) The literature reveals that apart from the processes of nitrification and denitrification there is a dearth of information on nitrogen cycling in African aquatic ecosystems (Thornton 1986). There is no information on the relative contribution of cyanobacterial N, fixation to the nitrogen budget of Lake Kariba. Such information can be of vital importance as this input of nitrogen might be one important source of nitrogen. This is particularly important for Lake Kariba as it is located in a basin which is not only highly leached but has inflows that are low in nutrients (Begg 1970, Coche 1974).
The main objectives of the current study were therefore to determine (1) the rates of BNF in the lake (2) the spatial and temporal variations and (3) the importance of BNF to the nitrogen economy of Lake Kariba.The present investigations were sponsored for many years by the University of Zimbabwe Research Board and by the Swedish Agency for Research Cooperation with Developing Countries (SAREC)
