2001 Volume 62 Issue 1 Pages 11-21
The phosphorus flux from the sediment to the overlying water was measured at high temperature and low dissolved oxygen concentration conditions in an eutrophic estuarine lagoon, Lake Shinji, using a continuous flow incubator with filtered bottom water and intact sediments. A high flux of dissolved organic phosphorus (DOP) was observed; the flux was almost equal to the phosphate (PO4-P) flux at the beginning of our experiments. The ratio of DOP flux to phosphate flux gradually decreased with time. The release flux of phosphate which had been adsorbed onto the metal oxides (e. g. ferric oxide) in the sediment-water interface was increased due to the decrease in dissolved oxygen concentration in the overlying water. Field data of temporal changes in concentrations of phosphorus species showed that DOP released from the sediment had been decomposed to phosphate rapidly in the bottom water. Thus, the DOP released from the sediment will be reused by phytoplankton in the overlying water. It became evident that we had been underestimating the load of phosphorus from the sediment to the overlying water, because we had been only measuring an efflux of one phosphorus species (phosphate) from the sediment.
