PHOSPHORUS DYNAMICS IN THE MONIMOLIMNION OF SWARTVLEI

Abstract

The exchange of phosphorus between the bottom sediment and monimolimnion of Swartvlei, a meromictic, humic lake, was investigated during the last three months of 1980. The concentrations of oxygen, dissolved salts, phosphorus and Fe⁺⁺ in the water column were monitored, and electrode potentials in the bottom mud were measured, at approximately weekly intervals. At the same time laboratory experiments were performed, using Jenkin core samples, to observe the effect of changing oxygen concentration and salinity on phosphate exchange between sediment and water, and on electrode potentials at the sediment-water interface. Phosphorus was released under unaerobic conditions at a rate of 2,5 mg P m⁻² d⁻¹ and was taken up again under aerobic conditions at 1,6 mg P m⁻² d⁻¹ These values were in agreement with existing observed data on changes in phosphate concentration.