The Study On The Correlation Between The Biological Effects Of Submerged Macrophyte (Vallisneria Spiralis) And Aquatic Environmental Quality

Restoring aquatic ecosystem using submerged macrophyte has become one of the focuses of aquatic environmental research. As the important primary productivity of aquatic ecosystem, submerged macrophyte plays an key role in water ecological system. The aim of this paper is to elucidate the correlation between aquatic environmental quality and biological effects of submerged macrophyte. The results are as follows:(1) In summer, tape grass (Vallisneria Spiralis) was cultivated in cement pond with sediment at different planting densities (500g/m2,200g/m2, 100g/m2,50g/m2).The effect of different planting densities of tape grass(Vallisneria Spiralis) on water purification was studied. The results indicated that the remove rate of TN in the different densities of 500g/m2,200g/m2, 100g/m2,50g/m2 was 66.67%,70.95%,66.48%,70.48%. The remove rate of TN in the different densities was significantly higher than that in the control group. But no significant differences in the removal rate of TN, however, were observed among the different densities. The remove rate of TP in the different densities of 500g/m2,200 g/m2,100g/m2,50g/m2 was 56.11%,63.75%,61.13%,57.54%. No significantly differences in the removal rate of TP were observed between the control group and the different densities. And no significant differences in the removal rate of TP were observed among the different densities. The remove rate of nitrate nitrogen in the different densities of 500g/m2,200g/m2,100g/m2,50g/m2 was 83.33%,76.83%,70.87%,72.88%. No significantly differences in the removal rate of nitrate nitrogen were observed between the control group and the different densities. The remove rate of nitrite nitrogen in 500g/m2 was significantly higher than that in 100g/m2 and 50g/m2. The remove rate of nitrite nitrogen in the different densities of 500g/m2,200g/m2,100g/m2,50g/m2 was 56.11%, 63.75%,61.13%,57.54%. No significantly differences in the removal rate of nitrite nitrogen were observed between the control group and the different densities. And no significant differences in the removal rate of nitrite nitrogen were observed among the different densities. The remove rate of COD in the different densities of 500g/m2, 200g/m2,100g/m2,50g/m2 was 47.92%,57.92%,60.98%,71.93%. No significantly differences in the removal rate of COD were observed between the control group and the different densities. And no significant differences in the removal rate of COD were observed among the different densities. In addition, the daily change of pH and DO varied significantly. The value of DO in the control group achieve maximum at 13:30, but the value of DO in different densities achieve maximum at 15:30. The value of pH and DO had the same change.(2) With the litterbag method, the influence of the decomposition of submerged macrophyte (Vallisneria Spiralis) in winter on water quality and the law of nutritional release was studied under the laboratory and ditch conditions. The results indicated that the released phosphorus from the decayed Vallisneria Spiralis in winter was mainly absorbed by the sediment. At the same time, the release of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen from the decayed tape grass was very limited. Therefore, the decomposition of tape grass attributed little to the eutrophication of cultured ponds in winter. Analyses of the decomposition rate of submerged macrophytes(Vallisneria Spiralis) under the different environment showed that the decomposition rate of grass was the fastest in treatment C. Aquatic environment has highly significantly impacts on dry weight, residual TN and TP of tape grass. The existing of sediment slowed down the lost rate of dry weight, but speeded up the lost rate of TN and TP. The release of phosphorus was the fastest during the decay of Vallisneria Spiralis. The process of decay of Vallisneria Spiralis has been divided a few phase. The decomposition rate was very fast in the first 36 days, but the rate became slower from 36 d to 66 d.(3)The submerged macrophyte(Vallisneria Spiralis) was planted in the different plastic buckets containing pond water in which the different concentrations of ammonia nitrogen and pH were set. The influences of the different factors (ammonia and pH value) on the growth of Vallisneria Spiralis were studied. The results indicated that the nonionic ammonia had significant impact on grass growth as well as plant biomass. The co-effect of nonionic ammonia and pH resulted in the significant change in chlorophyll content of Vallisneria Spiralis. As pH value and ammonia nitrogen reached to a certain degree in water, the imbalance in the content of carbon and nitrogen in grass would occur. This eventually led to the growth depression of tape grass. The activity of SOD and the content of MDA increased significantly due to long term of the exposure to the water in which high pH value and high ammonia content were detected.