UNEXPECTED GROWTH OF PISTIA STRATIOTES IN SANYATI GORGE, LAKE KARIBA

Abstract

During early 1984, the floating plant Pistia stratiotes grew unexpectedly and very rapidly in the Sanyati Gorge of Lake Kariba. Measurements of phosphorus and nitrogen in the surface waters revealed a pattern of nutrient concentrations along the gorge that could be related to the growth and decay of the plants. A set of unusual hydro-logical circumstances pertained in the Sanyati Gorge during this period, probably caused by the prevailing drought in the region. This is thought to have resulted in a reduced flushing effect of floods and abnormally high nutrient levels in the surface waters, so that P. stratiotes was able to grow until the seasonal flow of the Sanyati River declined further and a consequent insufficiency of nutrients inhibited further growth.