A restoration-promoting integrated floating bed and its experimental performance in eutrophication remediation

Numerous studies on eutrophication remediation have mainly focused on purifying water first, then restoring submerged macrophytes. A restoration-promoting integrated floating bed （RPIFB） was designed to combine the processes of water purification and macrophyte restoration simultaneously. Two outdoor experiments were conducted to evaluate the ecological functions of the RP1FB. Trial 1 was conducted to compare the eutrophication purification among floating bed, gradual-submerging bed （GSB） and RPIFB technologies. The results illustrated that RPIFB has the best purification capacity. Removal efficiencies of RPIFB for TN, TP,NH4＋-N, NO3-N, CODcr, Chlorophyll-a and turbidity were 74.45%, 98.31%, 74.71%, 88.81%, 71.42%, 90.17% and 85%, respectively. In trial 2, influences of depth of GSB and photic area in RPIFB on biota were investigated. When the depth of GSB decreased and the photic area of RPIFB grew, the height of Potamogeton crispus Linn. increased, but the biomass of Canna indica Linn. was reduced. The mortalities of Misgurnus anguillicaudatus and Bellamya aeruginosa in each group were all less than 7%. All results indicated that when the RPIFB was embedded into the eutrophic water, the regime shift from phytoplankton-dominated to macrophyte-dominated state could be promoted. Thus, the RPIFB is a promising remediation technology for eutrophication and submerged macrophyte restoration.     

Effect of the allelochemicals from the macrophyte Egeria densa on the competitive interactions of pelagic and littoral cladocerans

Macrophytes release allelochemicals, which affect pelagic cladocerans such as Daphnia. Using population growth experiments, we analysed the effects of allelochemicals from the macrophyte Egeria densa on the interaction between Daphnia mendotae and three littoral cladocerans (Diaphanosoma birgei, Macrothrix triserialis and Simocephalus mixtus). We found that allelochemicals from E. densa increased the abundance of all the tested cladocerans in spite of the presence of a competitor. This effect was stronger (nearly three to four times higher than in controls) for D. birgei and M. triserialis in the absence of D. mendotae. Independent of the presence of allelochemicals, S. mixtus, but not D. birgei and M. triserialis, reduced the abundance of D. mendotae as compared to controls. The rate of population increase (r) per day was significantly elevated due to the presence of Egeria’s allelochemicals (from 0.07–0.16?d^?1 without allelochemicals against 0.12–0.24?d^?1 with allelochemicals). In our competition experiments, the rates of population increase of the cladocerans were lower than those in single-species cultures when cultured in the absence of allelochemicals. However, in the presence of allelochemicals this trend was not consistent. Thus, the positive effects of Egeria’s allelochemicals over the cladoceran populations may enhance the grazing pressure on phytoplankton.     

城市地区重建湿地的生态过程研究

研究了湿地重建过程中植物、土壤和水质的动态变化特征.湿地重建2 a后植物种类增加了11种,芦苇、菖蒲和香蒲3种植物的高度、生物量在第2个生长季明显高于第1个生长季节,植物生物量分别增加到原来的13、1.5和1.4倍.湿地种植区土壤有机质总体上是降低的,土壤全氮含量从1?500　mg/kg降低到850　mg/kg（p＜0.01）,土壤全磷在试验期间略有增加.对重建湿地12种水质指标分析表明,夏季湿地出口源水溶解氧高于进口源水,出口源水总氮、叶绿素a、藻类计数3种水质指标均低于进口源水,说明重建湿地水质在夏季出口源水优于进口源水,水质得到改善.研究表明,湿地植物群落重建成功,生物多样性增加,重建湿地在改善和保持源水水质方面发挥了一定的作用.     

改性龙须眼子菜吸附水溶液中Cu2+的性能

采用批式实验法对改性龙须眼子菜吸附溶液中Cu2+的吸附动力学过程及吸附平衡进行了研究,考察了溶液初始pH值、吸附剂用量、温度等对改性龙须眼子莱吸附Cu2+的影响.结果表明,吸附动力学过程可以用准二级动力学方程进行拟合,吸附等温线符合Langmuir模型而不符合Freundlich模型.吸附实验的优化条件为:溶液初始pH值为4.0～5.6,溶液初始Cu2+浓度与吸附剂用量比值为10～25 mg·g-1,吸附时间为30～45 min,吸附温度为20-30℃.龙须眼子菜经甲醇改性后对Cu2+的吸附性能有了很大程度的提高;在改性龙须眼子菜吸附Cu2+的过程中,存在离子交换作用,但不占主导地位;改性龙须眼子菜吸附Cu2+主要依靠醇、酚类中的O-H基团,酰胺类中的C=O、N-H与C-N基团,砜类中的S=O基团与Cu2+的配位作用.     

氨氮浓度对苦草上附植藻类定植的影响

为了认识水体富营养化过程中附植藻类群落定植演替规律,利用显微计数法,通过室内静态模拟实验,研究了水体中不同氨氮浓度对太湖常见沉水植物苦草上附植藻类的影响。结果表明:采集的样品在以硅藻门中脆杆藻属、直链藻属、桥弯藻属、舟行藻属以及蓝藻门的色球藻属为优势种的样品在放置到不同浓度氨氮的实验组后,最后群落演变成为在低浓度氨氮营养盐下以舟行藻和脆杆藻为优势属,中高浓度的氨氮营养盐下以绿藻门的毛枝藻和硅藻门的小环藻和舟行藻为优势属的附植藻类群落结构;生物量在低浓度范围内与氨氮营养盐呈正相关。表明氨氮营养盐对附植藻类群落结构影响非常明显。     

Lignoid chemical defenses in the freshwater macrophyte Saururus cernuus

Summary. Chemical defense against herbivores has rarely been investigated for freshwater plants, possibly due to the common misconception that herbivory on aquatic macrophytes is low and would not select for chemical defenses. In previous work, the freshwater angiosperm Saururus cernuus was shown to be a low preference food for omnivorous crayfish despite its high nutrient value and relatively soft texture. We used feeding by the crayfish Procambarus clarkii to guide fractionation of the deterrent lipid-soluble extract of this plant, leading to the identification of seven deterrent lignoid metabolites, (–)-licarin A, (+)-saucernetin, (–)-dihydroguaiaretic acid, (–)-sauriols A and B, (–)-saucerneol, and (–)-saucerneol methyl ether. Lignans have been implicated in terrestrial plant chemical defenses as insect growth inhibitors, insect toxins, nematocides, antibacterial, and antifungal agents. However, these activities have rarely been demonstrated using ecologically relevant methodologies in terrestrial systems, and never before in freshwater systems. The widespread nature of lignans amongst very distantly related plants, along with their rich diversity of molecular structure, suggests that they could play a large role in mediating plant-herbivore interactions. In addition to the lignoid compounds we identified, there were other compounds present in low concentration or unstable compounds that were deterrent, that did not appear to be lignans, but that we were unable to identify. This plant thus appears to be defended by a complex mixture of natural products. Received 6 June 2000; revised 23 August 2000; accepted 2 September 2000     

月湖底栖动物的空间格局及其对水草可恢复区的指示

底质适宜是富营养湖泊恢复沉水植物(水草)的重要前提。大型底栖动物可综合指示底质的污染程度，于2002~2003年在武汉月湖开展了底栖动物水平分布对水草可恢复区指示作用的研究。首先通过月湖底栖动物与环境的相关分析，选择颤蚓科寡毛类作为底质营养状况的指示类群，然后利用同类湖泊群颤蚓与水草数据分析阈值，初步确定颤蚓密度≤100 ind/m2的底质适合水草生长，最后绘制月湖颤蚓分布的水平等值线，显示水草恢复的合适区域。在此基础上构建了应用底栖动物空间格局指示水草恢复区的技术原理框架。     

植物配置与进水碳氮比对沉水植物塘水质净化效果的影响

将3种常见湖泊沉水植物苦草(Vallisneris spiralis)、轮叶黑藻(Hydrilla verticillata)、穗花狐尾藻(Myriophyllum spicatum)组合构建7种沉水植物稳定塘,分析植物组合对水体氮、磷、有机物去除效果;在此基础上,模拟不同碳氮比(C/N)条件下的沉水植物塘对污水的净化效果,进而探讨碳氮比对沉水植物去污效果的影响.结果表明:(1)7种沉水植物组合对氮、磷均具有一定的净化效果,其中苦草和轮叶黑藻组成的沉水植物塘净化效果最好.(2)3种C/N(1.89、5.93、12.09)条件下,苦草黑藻植物塘的去污效果有所差异,当C/N=5.93时,对污染物的综合去除效果最佳.因此对于沉水植物稳定塘而言,沉水植物组合能取得比单类植物更好的净水效果,并且通过添加适量碳源物质,调整污水的碳氮比,可以提升沉水植物塘的净水效果,研究结果对于实际工程构建稳定塘净化污水具有理论指导意义.     

Purification and reclamation of wastewater by an integrated biological pond system

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镉对沉水植物硝酸还原酶和超氧化物歧化酶活性的影响

研究了重金属污染物镉对４种沉水植物（红线草，金鱼藻，黑藻和菹草）硝酸还原酶和超氧化物歧化酶的分子毒理学效应。实验结果表明，一定浓度的镉能诱导沉水植物的硝酸还原酶活性，抑制沉水植物超氧化物歧化酶活性，从而破坏其抗氧化防御系统。镉对沉水植物的毒害存在明显的剂量／效应关系。建议以硝酸还原酶和超氧化物歧化酶的活性变化作为沉水植物受重金属污染的生态毒理学指标。