Abstract: Processes of nutrients (nutrient salts,N and P)releasing from decaying submerged macrophytes(Vallisneria natans)at the temperature of an early spring were simulated in laboratory to strdy laws of the nutrient release.Results show that the rapidly decaying plant released a lot of nutrients(C,N and P)into the water at the temperature of an early spring.With the time going by,most of the phosphorus released from the plant setteled down into the sediment,whereas only part of the nitrogen went down and part escaped out of the water as gas.The anaerobic condition resulting from decomposition of the plant and the supply of large amounts of organic carbon promoted denitrification in the waterbody,thus accelerating escape of N out of the water.A large amount of plant residues resulted in oxygen deficiency of the water and relaese of large amounts of nutrients,thus leading to deterioration of water quality.It is,therefore,advisable to harvest the aquatic plant to reduce residue biomass in the waterbody.

Key words: submerged macrophyte, Vallisneria natans, decay, nutrition, early spring