Study On Coupling Relationship Of Decomposition - Growth - Water Quality Of Aquatic Plants

During the quarterly alternation process of aqauatic plants, nutrients released from the decomposing plants residues promote the growth of aqauatic plants. Meanwhile, aqauatic plants would improve nutrients level of water which took advantage of their own ecological functions. As well as the alternation of decomposing and growth of aqauatic plants jointly promoted the elemental cycling and energy conversion in aquatic ecosystem. The "self-healing" capability was significant to maintain the balance and stability of the aqauatic ecosystem. By simulating the quarterly alternation of aqauatic plants, the coupled relationship among the decomposing-growth of aqauatic plants and water quality were discussed in the study. The resutls would provide theoretical support for the ecological restoration of aquatic ecosystem.In order to study the coupled relationship among the decomposing-growth of aqauatic plants and water quality, the Trapa quadrispinosa, Potamogeton crispus and Ceratophyllum demersum were selected to ensure the continuity of the cycle. And the simulating experiments of sping-summer-autum quarterly alternation were conducted. Main results were as follows:(1) With different quality of aqauatic plants residues, the concentrations of DTN, TN, DTP, TP, TOC and Chl-a in the water that added with aqauatic plants maintained in a relatively low level, and they were lower than the water without aqauatic plants added. All the concentrations kept stable at 20th days later.(2) The coupling effects between decomposing and growing of aqauatic plants can obviously improve the water quality. In the coupled system of decompoded Trapa quadrispinosa residues and growing Potamogeton crispus, the coupling action made better effects with 1.5 kg·m-3 residues in the system. The removal ratio of TN, TP, TOC and NH4+ reached to 24.52%,56.56%,41.58% and 31.26%, respectively. And in the coupled system of decompoded Potamogeton crispus residues and growing Ceratophyllum demersum, the coupling action made better effects at 2.0 kg·m-3 residues, with the removal ratio of 89.67%,52.51%,94.99%,55.59% and 98.55% respectively for TN, DTN, TP, TOC and Chl-a.(3) Nutrients released from decomposing Trapa quadrispinosa residues promoted the growth of Potamogeton crispus. The coupled system of decompoded Trapa quadrispinosa residues and growing Potamogeton crispu with the 0.5 kg·m-3 residues quantity showed a low level at the contents of total chlorophy Ⅱ and biomasses due to the weak effect on the plant growth. However, the coupled system of decompoded Trapa quadrispinosa residues and growing Potamogeton crispu with the residues quantity of 1.5 kg·m-3 displayed the higher contents of total chlorophy Ⅱ and biomasses, which suggested the coupling effects between decomposing and growing of aqauatic plants whit 1.5 kg·m-3 Trapa quadrispinosa residues quantity made significant influence on water quality improvement and Potamogeton crispu growth.(4) Nutrients released from decomposing Potamogeton crispus residues then promote the growth of’Ceratophyllum demersum. The imporving effets with the residues amount of 2.0 kg·m-3 were better than that of 1.0 kg·m-3 in the coupling system of decomposed Potamogeton crispus residues and growing Ceratophyllum demersum, and the contents of total chlorophy Ⅱ and soluble protein increased to the top from the lowest at 1.0 kg·m-3. The results indicated that the coupling effects between decomposing and growing of aqauatic plants with 2.0 kg·m-3 Potamogeton crispu residues quantity achieved the best effects on water quality improvement and Ceratophyllum demersum growth.