Submerged Plant The Decline And Fall Of Redistribution Between Overlying Water And Sediment Phosphorus Content

Phosphorus is indispensable to plant growth,and is the key factor of alga bloom in eutrophic lakes. In shallow lakes, the course of phosphorus transferring between water and sediment has important effect to water phosphorus load. Submerged macrophytes inhabit between water and sediment, has control function of phosphorus cycling between water and sediment. The course of phosphorus between water and sediment was short of study in the decomposition period.In order to study the effect of submerged macrophyte on phosphorus transferring between water and sediment, big canopy submerged macrophyte Hydrilla verticillata and root development submerged macrophyte Vallisneria natans were selected. The system of "water-submerged macrophyte-sediment" was built, the concentrations of all phosphorus fractions in water and sediment was measured, in the decomposition period, to study the effect of submerged macrophyte on phosphorus reallocation between water and sediment in the decomposition period. The results indicated that, the concentration of phosphorus in water and sediment was improved obviously, in the decomposition period of H. verticillata and V. natans. H. verticillata increased phosphorus concentration of pore water, but V. natans has no significant effect.(1) Submerged macrophyte H. verticillata and V. natans releasd phosphorus to water and increased the concentrations of all phosphorus fractions in overlaying water in the decomposition period. The results indicated that the concentrations of all phosphorus in overlaying water were significant higher (P<0.05) than the contol groups in the decomposition period of H. verticillata. The concentrations of phosphorus showed single peak curve in the decomposition period of H. verticillata. The concentration of phosphorus reached the maxvalue (TP,0.63mg/L) at the40d. All phosphorus concentrations have no significant difference between V. natans and the control groups, and the concentrations have relative gentle changes (TP:0.04～0.06mg/L)(2) Submerged macrophyte H. verticillata and V. natans has significant effect on phosphorus concentrations of pore water. The concentrations of dissolved total phosphorus (DTP)and soluble reactive phosphorus (SRP) were significant higher than that of the control groups, dissolved organic phosphorus (DOP) has no significant between H. verticillata and the control groups.The concentrations of all phosphorus fractions of V. natans were significant lower than that of the control groups,the concentrations of DTP, SRP and DOP were0.23mg/L.0.12mg/Land0.10mg/L, at the end of the experiment.(3) H. verticillata and V. natans increased phosphorus concentrations in sediment in the decomposition period. H. verticillata and V. natans increased phosphorus concentrations in sediment, but has no significant difference compare with the control groups (P>0.05). H. verticillata decomposed almost compoletely in the40days, but V. natans decomposed slowly in all the experiment course. The concentrations of total phosphorus (TP), inorganic phosphorus (IP), organic phosphorus (OP),NaOH extracted phosphorus (NaOH-P) and HCl extracted phosphorus(HCl-P) increased4.61%、6.17%、2.02%、5.33%and4.89%in H. verticillata;2.08%、2.67%、1.05%、3.03%and1.47%in V. natans.