Wu Juan

Establishing Submersed Macrophytes via Sinking and Colonization of Shoot Fragments Clipped off Manually

In this paper, sinking and growth of apexes and mid-stems of Myriophyllum spicatum L., Hydrilla verticillata (L.f.) Royle and Ceratophyllum demersum L. in concrete ponds containing eutrophic water and sediment were investigated. Sinking rates of apexes and mid-stems reached 34.8% and 4.4% at the 6 th day and 91.1% and 66.7% at the 22 nd day for M. spicatum, 57.8% and 55.6% at the 6 th day and 100% and 97.8% at the 22 nd day for H. verticillata, 18.9% and 86.7% at the 6 th day and 95.6% and 100% at the 22 nd day for C. demersum, respectively. Most sunken fragments established themselves successfully with significant growth. Total shoot length of plantlets developed from apexes and mid-stems increased by 399% and 61% for M. spicatum, 593% and 256% for H. verticillata and 114% and 104% for C. demersum, respectively. The results showed that it was feasible to establish submersed macrophytes via sinking and colonization of shoot fragments clipped off manually.

金鱼藻(Ceratophyllum demersum)调控浮游植物捕获磷与生长的策略

水体浮游植物具有捕获利用磷的能力以及沉水植物能够显著抑制水体中藻类生长已得到国内外广泛共识，但相应的潜在机制尚缺乏深入了解.本研究选取金鱼藻（Ceratophyllum demersum）为研究对象，基于室内模拟实验，探讨了沉水植物调控浮游植物捕获磷与过度生长的机制.结果显示，尽管未种植金鱼藻的对照组上覆水中总磷、总溶解态磷和可溶性活性磷的平均浓度均显著高于种植金鱼藻的实验组（约4倍），但是两个系统中这3种磷浓度随时间的变化趋势均符合S形的对数曲线.实验组藻类密度、有效光量子产量、总碱性磷酸酶活性（TAPA）以及细颗粒碱性磷酸酶活性（细颗粒APA）也远低于对照组.此外，对照组中粗颗粒碱性磷酸酶活性（粗颗粒APA）占TAPA的44.7%，显著高于细颗粒APA.结构方程模型结果表明，对照组水体藻类密度对TAPA具有直接的正向作用，而金鱼藻的生长显著弱化了不同形态磷与APA、藻类密度、细菌动力以及光量子产量之间的相互作用.这说明沉水植物对水体浮游植物生长的调控具有多种策略.

Effect of step feeding on the performance of multi-stage vertical flow constructed wetland for municipal wastewater treatment

To investigate the effect of step feeding on the performance of multi⁃stage vertical flow constructed wetland (MS⁃VFCW) for municipal wastewater treatment, raw wastewater with four step feeding ratios (0% , 10% , 20% and 30% ) were dosed to the second stage of the MS⁃VFCW plots at a total hydraulic load of 100 mm / d. The results showed no significant differences in removal of chemical oxygen demand (COD) and total phosphorus (TP) among the four step feeding ratios, and the highest removal rates of COD and TP reached up to 87.80% and 81.17% , respectively. Most COD was removed in the first stage, with an average contribu⁃ tion of 82.18% . While the most TP was removed in the third stage, with an average contribution of 54.37% . In contrast, the differ⁃ ences in total nitrogen (TN) removal rates among the four step feeding ratios were significant, with the highest TN removal rates (61.70% ±4.48% ) under the ratio of 20% , in which the average removal contribution of each stage was 36.52% , 42.11% and 21.37% , respectively. The step feeding ratio was recommended as 20% in application of the hybrid VFCWs so as to achieve sound pollutant removal performance.

Research progress of seed bank for restoration of wetland vegetation

Recently,restoration and reclamation of vegetation in degraded wetland ecosystem have become a hot subject.As a reservoir of past plants,seed bank has huge potential for natural re-generation of wetland vegetation.In this review,we provided an overview of the major researches and progresses in the wetland seed bank formation,size and spatial pattern,species composition and relationships between seed bank and standing vegetation at home and abroad.Some case studies of wetland restoration using soil seed bank are introduced here,especially focused on main factors affecting seedling emergence of soil seed bank,safe sites for establishment of seedling and restoration potential of soil seed bank.We further discussed the main problems presented in the wetland re-vegetation from soil seed bank at present research and its possible direction of future studies.This review is expected to be a key reference for the development in the theory and practical techniques of restoration of wetland vegetations from soil seed bank.

Effect of Hydrilla verticillata on characteristics of water and sediment and removals of nutrition.

The effects of Hydrilla verticillata on water and sediment in eutrophic lake were investigated by a microcosm experiment. The experiment was conducted with lake water, sediment and H. verticillata collected from Yuehu Lake in Wuhan, China, in 1m x 1m x 1 in outdoor aquaria. The apical shoots of this species were planted at 4 densities (0, 50, 100 and 150 shoots/m(2)). Dissolved oxygen (DO), pH, total nitrogen (TN), ammonia (NH4+) and total phosphorus (TP) in water column were measured at the 1st, 8th, 21st, 38th and 55th day after initiation of the experiment, respectively, Eh, pH, TN and TP of sediment were measured as well. At the end of the duration, the plants were harvested and the dry biomasses were measured. The experimental results showed that the dry biomasses were 52.9, 31.9 and 24.8 times higher at harvest than that at the initiation of the experiment respectively. DO in water column of the treatments with plants was 2.6 times higher than that of the control, pH values also significantly increased up to 9.85 in the density of 150/m(2) at the 38th day. However, the 3 planting densities did not show significant difference in these two parameters. The concentrations of TN and NH4+ in water column with plants deceased by 90.2% and 70.0% compared with the control respectively, whereas, the differences among the treatments were not significant. TP in water column decreased with planting densities by 38.9%-57.1%, and the differences among treatments were distinct. As a function of radial oxygen releases from root, the Eh values of sediment increased by 58.6-109.4mV with the planting density compared with the control. Whereas, the pH in the 3 treatments decreased sharply during the first 20 days, then increased up to 7.20-7.34, but still lower than that of the control, which could be explained by the releases of root exudates. In addition, the growth of H. verticillata can effectively reduce the TN and TP in the sediment. It is concluded that the existence of H. verticillata can remove nutrition and improve the quality of water column and sediment. However, plant density is a factor need to be considered in revegetation of degraded lakes, because excessive density may inhibit the growth of plants. So harvesting at appropriate time is a necessary measure to enhance the effect of the submerged macrophyte.