不同特性底质对沉水植物恢复生长的影响

通过室内模拟实验,研究了3种土壤基质（沙土、粘土和腐殖土）分别与河岸边土壤按5个质量分数（5%、10%、30%、50%和80%）掺混形成的不同成分底质分别对菹草（Potamogeton crispus）、轮叶黑藻（Hydrilla verticillata）和微齿眼子菜（Potamogeton maackianus）顶枝断枝恢复生长的影响。结果表明：（1）在3种基质与岸边土壤掺混的底质上,实验结束时菹草的平均最高植株分别出现在5%SA（沙土与岸边土掺混）底质、50%NA（粘土与岸边土掺混）底质和10%FA（腐殖土与岸边土掺混）底质,株高分别达到30、48和45 cm;轮叶黑藻的平均最高植株分别出现在10%SA底质、50%NA底质和30%FA底质,株高分别达到47、82和59 cm;微齿眼子菜在3种基质掺混的底质上植株株高几乎没有增高;（2）生长于同种底质的植株,单位高度上菹草的生物量大于轮叶黑藻,微齿眼子菜的生物量几乎没有增加。因此,适宜菹草和轮叶黑藻恢复生长的基质顺序为粘土〉腐殖土〉沙土,微齿眼子菜在3种基质掺混的底质上几乎没有生长;植株对于特性底质适应性强弱的顺序依次为轮叶黑藻〉菹草〉微齿眼子菜。     

太湖沉水和浮叶植被及其水环境效应研究

运用GPS定位技术和常规采样方法,于2004年5月和9月对太湖沉水植物与浮叶植物的种类、群落类型、生物量及其水质状况进行了调查。结果表明:沉水植物与浮叶植物是太湖水生植被的主要类型,沉水植物群落类型主要有6个:微齿眼子菜群落;马来眼子菜群落;伊乐藻群落,穗花狐尾藻群落,金鱼藻群落,苦草群落;浮叶植物群落类型主要有3个:莕菜群落,金银莲花群落,菱群落。在春季,沉水植物占绝对优势,在夏秋季,浮叶植物则逐渐发展,尤其以莕菜生长最快。通过对有草区和无草区水质的比较,发现水生植被能显著提高水体的透明度、降低营养盐浓度和叶绿素含量,改善水质。     

不同水质对沉水植物马来眼子菜主要生理指标的影响研究

沉水植物生理指标能反映其生长的环境条件变化,建立二者的关系对认识沉水植物衰退机理以及湖泊生态系统修复具有重要的意义。采用原位试验,分析了太湖不同营养状态条件下马来眼子菜(Potamogeton wrightii Morong)叶片内叶绿素含量、过氧化物酶(POD)活性以及游离脯氨酸(PRO)含量的差异,初步探讨了马来眼子菜叶片内主要生理指标对水质的响应机理。结果表明:(1)马来眼子菜分布的不同湖区间水质理化因子、综合营养状态指数(TLI)存在显著的空间差异,马来眼子菜主要生长于中营养水质或富营养状态下;(2)太湖马来眼子菜叶片内主要生理指标存在显著空间差异,其叶绿素、POD与TLI呈显著二次多项式回归关系,中营养水平下,除游离脯氨酸外,其他生理指标均与TLI呈显著相关;(3)中营养水平下,马来眼子菜叶片内各生理指标与水质理化因子之间表现为显著相关性,且与TN、TP及COD_Mn关系最为密切。本试验表明,马来眼子菜比较适合中营养水质条件,水体氮磷浓度、高锰酸盐指数对马来眼子菜的生理影响较大。     

水位抬升对4种沉水植物生长及光合特性的影响

通过滆湖现场实验的方法模拟水位抬升,研究其对4种沉水植物的生长和光合荧光特性的影响。实验前30 d相应水位为2.6 m(控制水深为1 m),之后2 d内迅速抬升水位,32 d时各实验组相应水位为2.6、3.0、3.4和3.8 m,分别模拟水位不变、低水位抬升、中水位抬升和高水位抬升,各组水位一直保持到第70天实验结束。结果表明:随着水位抬升幅度增加,4种植物的株高显著增加(P0.05)。冠层型植物狐尾藻(Myriophyllum spicatum)、马来眼子菜(Potamogeton malaianus)生物量相应增加,高水位抬升下直立型黑藻(Hydrilla verticillata)生物量显著减小(P0.05),莲座型植物密刺苦草(Vallisneria denseserrulata)生物量随水位抬升幅度的增加而减小。在一定范围内,水位抬升减弱了狐尾藻、马来眼子菜和黑藻的定植能力,增强了密刺苦草的定植能力。冠层型植物在光合作用方面的表现同样优于直立型和莲座型植物,这说明不同的沉水植物对水位抬升的响应具有不同的生理生化特征。水位抬升促进了以狐尾藻、马来眼子菜为代表的冠层型植物的生长,高水位抬升不利于直立型植物黑藻的生长,抑制了莲座型植物密刺苦草的生长。以狐尾藻、马来眼子菜为代表的冠层型植物从形态学响应和光合作用能力上更适合水位抬升。该研究可为湖泊河流中沉水植物的恢复提供参考。     

4种沉水植物对白洋淀富营养化水体净化效果的研究

利用白洋淀富营养化的湖水和底泥与蓖齿眼子菜、马来眼子菜、金鱼藻和黑藻4种沉水植物分别组成室内静态模拟的生长体系,研究4种沉水植物在白洋淀富营养化环境下的生长状况,以及不同沉水植物生长体系对水体磷、氮及有机物的净化效果。结果表明：试验所用沉水植物对富营养化湖水、底泥具有一定的耐受能力,在试验条件中生长良好,长度与生物量都明显增加,并能有效地降低水体中的总磷、氨氮及总氮浓度。试验21 d后,蓖齿眼子菜、马来眼子菜、金鱼藻和黑藻所在的生长体系对水体中总磷的去除能力分别为：4.68、4.72、4.92和5.03μg·d-1·g-1,去除率分别为：83.59%、84.35%、87.84%和89.88%;对水体中氨氮的去除能力分别为：11.42、10.75、12.02和11.90μg·d-1·g-1,去除率分别为：74.98%、70.58%、78.96%和78.11%;对总氮的去除能力分别为：37.69、39.79、42.02和41.65μg.d-1.g-1,去除率分别为：79.40%、83.82%、88.51%和87.73%。沉水植物生长体系对CODcr的降解有所反复,但整体呈现下降趋势。不同沉水植物生长体系总磷、总氮含量随时间降解的拟合方程表明,水体总磷、总氮浓度随时间的变化呈负指数形式衰减。沉水植物对水体营养盐浓度的影响通过多种途径实现,底泥在营养盐的归趋中起着重要的作用。     

浮叶植物重建对富营养化湖泊氮磷营养水平的影响

利用太湖五里湖污染底泥，在不破坏表层沉积物形态和结构的情况下，利用大口径的采样器采集沉积物柱状样，研究浮叶植物荇菜（Limnanthemun nymphoides）在此底泥上适应性生长情况及其对水体以及沉积物中氮磷的影响。结果表明，在培养实验过程中，荇菜生长使上覆水体中的氮、磷营养水平逐渐降低，藻类的生长明显受到克制，水体透明度增加，水质逐渐改善。通过植物根系对沉积物和问隙水中营养盐的直接吸收，使表层（0～5cm）沉积物与问隙水中氮磷营养盐的水平在实验结束后有明皿下降，对于控制沉积物内源营养盐释放有重要的作用。因此，恢复以水生植物为丰的水生生态系统足重建富营养湖泊生态系统和控制湖泊内源负荷的重要措施。     

太湖表层沉积物中多磷酸盐检出的环境意义

在氮限制型富营养化湖泊中,沉积多磷酸盐(Poly-P)可以用来示踪营养盐磷的输入和湖泊的富营养化过程。太湖是一个典型的磷限制型富营养化湖泊,通过对太湖表层沉积物中总有机碳(TOC)、总氮(TN)、总磷(TP)、氢氧化钠可提取磷(NaOH-P)以及Poly-P的提取分析,初步探讨了太湖营养盐磷输入的历史记录,并揭示了该湖Poly-P的主要来源和保存机制。太湖Poly-P的质量浓度较低,变化范围为0.004~0.065mg·g-1。NaOH-P占TP组成的22%,是太湖沉积物总磷的主要组成部分之一。结果显示,在湖泊水体藻类生物量较大和NaOH-P是沉积物TP重要组成部分的磷限制型湖泊中,Poly-P也是沉积物磷汇组成的一个重要部分,同时还是一个可以反映由人为磷输入增大导致湖泊富营养化程度加剧的敏感指标。     

东太湖3种沉水植物群落区底泥种子库与幼苗库

底泥种子库在沉水植物恢复中具有重要作用.研究了东太湖3种优势沉水植物苦草(Vallisneria natanus L.)、马来眼子菜(Potamogeton malaianus Miq)和微齿眼子菜(Potamogeton maackianus)群落区的广义种子库和种子库采样区的幼苗库.2005年1月,在3种植物的优势群落区各随机采取泥样样方9个,25 ℃的培养箱内,光照周期L∶D＝12∶12条件下,采用种子萌发法鉴定土壤种子库.研究结果显示,实验室内种子库在5个月内全部萌发完毕.3种沉水植物群落区的广义种子库大小分别为1003.33粒·m-2,1446.67粒·m-2和910粒·m-2,优势种植物的种子占相应区域种子库总量的97%以上.从种子库结构上看,苦草主要以无性繁殖为主,微齿眼子菜以有性繁殖为主,马来眼子菜则无性繁殖和有性繁殖同等重要.对比研究采样点区域植物群落当年植物幼苗的萌发情况,结果表明,幼苗库在数量上要远小于其相应的种子库的规模,幼苗库植物种类要多于相应的种子库,生物多样性也较种子库高,幼苗库与种子库的相似系数在0.330.67.     

不同沉水植物对沉积物磷迁移转化的影响

选择了微齿眼子菜(Potamogeton maackianus A.Benn .)、穗花狐尾藻(Myriophyllum spicatum L .)和金鱼藻(Ceratophyllum demerswn L .)3种沉水植物,在温室模拟研究了不同沉水植物对湖泊沉积物磷迁移转化的影响.研究结果表明,随着培养时间的延续微齿眼子菜和穗花狐尾藻对沉积物NaOH-P有明显的吸收和转化作用,分别吸收和转化了36.9%和33.2%,而金鱼藻对沉积物NaOH-P的影响不显著;各处理随着植物的生长,由于根系的吸收作用,沉积物中Olsell-P发生了从非根际→根际→沉水植物的迁移过程,其中微齿眼子菜和穗花狐尾藻更为明显.因此,微齿眼子菜和穗花狐尾藻对沉积物磷释放的控制作用更为明显.     

中国三个不同富营养化湖泊沉积物中Cu、Zn赋存特征及其与营养盐的相关性分析

对太湖、南四湖、白洋淀三个不同富营养化湖泊沉积物进行采样,采用Tessier连续提取法,测定了3个湖泊表层沉积物中Cu、Zn两种重金属的赋存形态,并初步探讨了重金属各形态与沉积物及上覆水中营养盐的相关关系。结果表明,沉积物中重金属总量以白洋淀最高,太湖最低,但重金属污染程度为太湖＆gt;南四湖＆gt;白洋淀,太湖Cu污染指数为1.34~1.6,白洋淀Cu污染指数仅为0.79~1.17。沉积物中重金属赋存形态Cu主要以残渣态和有机质结合态为主（二者之和占73%以上）, Zn则以残渣态和Fe-Mn氧化态占优（二者之和比例达83%以上）,含量最少的均为可交换态。不同湖泊沉积物重金属赋存形态差异较大,太湖残渣态重金属占总量的比例最小（Cu为43%~56%,Zn为49%~63%）,南四湖残渣态占的比例最大（Cu为59%~82%、Zn为64%~77%）;可交换态比重在太湖中最高（Cu占3.2%~5.6%,Zn为1.3%~1.5%）,在南四湖中最低（Cu为1.1%~2.9%,Zn未检出）。从“非稳定态”重金属（除残渣态外的四种形态之和）所占比例看,相较其它两个湖泊,太湖沉积物中重金属污染人为输入的活性态占较大比重,具有较高的二次释放风险。相关性分析得出,重金属Cu的可交换态与上覆水中总氮及总磷之间存在着极显著的正相关关系,碳酸盐结合态Cu与沉积物中营养盐呈现出显著的负相关性,说明水体的富营养化程度加剧可能会增强沉积物中Cu向水体释放的风险。     

Quantitative characterization of Cu binding potential of dissolved organic matter （DOM） in sediment from Taihu Lake using multiple techniques

Dissolved organic matter （DOM） plays an important role in heavy metal speciation and distribution in the aquatic environment especially for eutrophic lakes which have higher DOM concentration. Taihu Lake is the third largest freshwater and a high eutrophic lake in the downstream of the Yangtze River, China. In the lake, frequent breakout of algae blooms greatly increased the concentration of different organic matters in the lake sediment. In this study, sediment samples were collected from various part of Taihu Lake to explore the spatial difference in the binding potential of DOM with Cu. The titration experiment was adopted to quantitatively characterize the interaction between Cu（II） and DOM extracted from Taihu Lake sediments using ion selective electrode （ISE） and fluorescence quenching technology. The ISE results showed that the exogenous DOM had higher binding ability than endogenous DOM, and DOM derived from aquatic macrophytes had a higher binding ability than that derived from algae. The fluorescence quenching results indicated that humic substances played a key role in the complexation between DOM and Cu（II） in the lake. However, because of the frequent breakout of algae blooms, protein-like matters are also main component like hnmic matters in Taihu Lake. Therefore, the metals bound by protein-like substances should be caused concern as protein-like substances in DOM were unstable and they will release bound metal when decomposed.     

A system-dynamic model on the competitive growth between Potamogeton malaianus Miq. and Spirogyra sp.

A system-dynamic model has been built to evaluate the competition between submerged macrophytes Potamogeton malaianus Miq. (PM) and filamentous green algae Spirogyra sp. (SP). The data background is based on a spring–summer and an autumn–winter experiment carried out in artificial field ponds. The experiments had the aim to acquire a knowledge base necessary to a successful restoration of submerged macrophyte vegetation in Lake Taihu, China by use of P. malaianus Miq. The model mainly focuses on variations in water volume; biomass dynamics of P. malaianus Miq., Spirogyra sp. and zoobenthos; nutrients cycling between water column, P. malaianus Miq., Spirogyra sp., zoobenthos, detritus and sediment. Sixteen state variables are included in the model: biomass of P. malaianus Miq., Spirogyra sp. and zoobenthos; nitrogen in sediments, detritus, in P. malaianus Miq., in Spirogyra sp. and zoobenthos; total dissolved nitrogen; phosphorus in sediments, detritus, in P. malaianus Miq., in Spirogyra sp. and in zoobenthos; total dissolved phosphorus, and water volume of the experiment pond. The calibration and validation of the model show a good accordance with the results of the spring–summer experiment and the autumn–winter experiment.     

应用物种敏感性分布法分析太湖及天目湖水体的生态风险

采用物种敏感性分布法(SSDs法),应用水生生物急性和慢性毒性数据计算了31种污染物在水中和其中疏水物质在沉积物中的预测无效应浓度(PNECwater和PNECsed),通过收集以往报道的16种污染物在太湖和天目湖的环境浓度,用商值法求得物质的风险商并进行排序.结果发现:蒽、菲、萘、荧蒽、阿特拉津和马拉硫磷在太湖的梅梁湾和五里湖具有很大的生态风险;毒死蜱、三丁基锡氧化物和环己锡虽无环境浓度报道但很有可能具有风险.     

Phosphorus speciation and effects of environmental factors on release of phosphorus from sediments obtained from Taihu Lake,Tien Lake,and East Lake

Phosphorus is considered the primary nutrient limiting eutrophication. The release of phosphorus from sediments not only provides hydrophytes with essential nutrients, but can also produce entrophication in lakes. In this study, the sediment characteristics, phosphorus speciation, and environmental factors affecting phosphorus release from sediments from Taihu Lake, Tien Lake, and East Lake were investigated. The results indicated that phosphorus levels of sediments ranged from 647 ± 67 to 2343 ± 122 mg/kg. Inorganic phosphorus comprised the majority of total phosphorus. The main phosphorus speciation of sediments obtained from Taihu Lake and Tien Lake was Residual-P, and the main phosphorus speciation of sediment obtained from East Lake was NaOH-P. Phosphorus release occurred in acidic and alkaline conditions but more frequently under alkaline conditions. The amount of phosphorus released from the sediments increased as the disturbing intensity rose. In addition, less phosphorus was released in natural than anaerobic conditions. The amount of phosphorus released was elevated as temperature increased.     

Evaluation of biological water purification functions of inland lakes using an aquatic ecosystem model

An effective measure to cope with eutrophication of lakes is to remove nutrients that can cause algal blooming by taking advantage of natural water purification processes. Here the term “purification” is defined, in a wide sense, as the potential role of a water body to contribute to the reduction of pollutants and thus controlling eutrophication. Also regarded as a kind of ecological regulating services, biological purification involves various processes concerning seasonal nutrient fixation, such as uptake by aquatic macrophytes, biofouling onto foliage substrates, feeding by organisms in higher trophic level, and eternal loss or removal of substance from the water. In order to evaluate the water purification ability, a numerical lake ecosystem model highlighting the role of macrophyte colonies in the shore zone was developed and applied to Lakes Suwa, Kasumi and Biwa, as well as five small lakes attached to Lake Biwa.     

Effects of previous drying of sediment on root functional traits and rhizoperformance of emerged macrophytes

• Sediment desiccation alters morphological characteristics of aquatic sediment. • Alternation in morphological properties of sediment limiting root characteristics. • Fibrous-rooted macrophytes root properties extra favor nutrients removal. • Thick-rooted macrophytes exhibit higher life-span in two sediment types. Purpose of the current study was to investigate the effects of constantly wet and dried-rewetted sediments on root functional traits of emerged macrophytes and their nutrients removal abilities. It is based on the hypothesis that root characteristics and nutrients removal abilities of plants will be altered in the course of sediment desiccation. Four emerged macrophytes including two fibrous-root plants (Canna indica and Acorus calamus) and two thick-root plants (Alocasia cucullata and Aglaonema commutatum) were investigated for their root functional traits and rhizoperformance in both wet and dried-rewetted sediments. Results showed that sediment desiccation followed by rewetting substantially altered the root functional traits (root surface area, radial oxygen loss, and root activity) of plants due to adverse changes in morphological characteristics (porosity, bulk density, particle density) of dried-rewetted sediments than by wet sediments. Consequently, limited plants growth and removal of nitrogen (N), phosphorus (P) and dissolved organic carbon (DOC) were recorded in dried-rewetted sediments and their pore water than in wet sediments. Radial oxygen loss from plant roots correlated positively with root functional traits, plants growth, and removal of N, P and DOC from pore water and sediment in both sediment types. Among the macrophyte species, the fibrous-root plants having advantages root functional traits, greatly influenced the rhizospheric conditions (pH, dissolved oxygen and redox potential), and demonstrated higher N, P and DOC reduction from both sediment types. While, the thick-rooted plants with thick diameter roots (D > 1 mm) and higher rhizome exhibited longer life-span in both sediment types.     

Relating effect and response traits in submersed aquatic macrophytes.

Reliably predicting the consequences of short- or long-term changes in the environment is important as anthropogenic pressures are increasingly stressing the world's ecosystems. One approach is to examine the manner in which biota respond to changes in the environment ("response traits") and how biota, in turn, affect ecosystem processes ("effect traits"). I compared the response and effect traits of four submersed aquatic macrophytes to understand how water level management may affect wetland plant populations and ecosystem processes. I measured resource properties (nutrients in sediment and water), non-resource properties (pH, alkalinity, sediment temperature, oxygen production), and biotic properties (periphyton biomass) in replicated outdoor monocultures of Stuckenia pectinata, Potamogeton nodosus, P. crispus, and Zannichellia palustris. After seven weeks, three of eight replicates of each species treatment were subjected to a temporary water draw-down that desiccated aboveground plant parts. The four species differed in their effects on ecosystem properties associated with nutrient uptake and photosynthetic activity. Shoot growth rate was negatively correlated with light transmittance to the sediment surface whereas root growth rate and root:shoot ratio were correlated with a species' ability to deplete nutrients in sediment interstitial water. Occupation of space in the water column was correlated with water alkalinity and pH and with sediment temperature. Root growth rate was related simultaneously to species effects on sediment nutrient dynamics and recovery of ecosystem properties after water draw-down. This suggests that this morphological trait may be used to predict the effects of environmental change on ecosystem functioning within the context of water level management. Expanding these analyses to more species, different environmental stressors, and across aquatic and terrestrial ecosystems should enhance predictions of the complex effects of global environmental change on ecosystem functioning.     

Responses of decomposition rate and nutrient release of floating-leaved and submerged aquatic macrophytes to vertical locations in an urban lake (Nanhu Lake,China)

A leaf-bag field experiment was conducted to investigate the decomposition and release of nutrients from leaves of two aquatic macrophytes (floating-leaved Trapa bispinosa and submerged Vallisneria natans) deposited in the four vertical locations (i.e. air-water interface, AW; sediment-water interface, SW; buried at a depth of 10?cm, B10; buried at a depth of 20?cm, B20) of littoral zone in Nanhu Lake, China, for 60 days from July to August 2015. Leaf initial quality significantly influenced mass loss and nutrient release except TN (total nitrogen) remaining. Compared to V. natans, T. bispinosa leaves decomposed faster under the same treatments. The decomposition was greatly affected by both leaf chemical quality and the location of deposition. With the increasing depth of vertical locations, leaf biomass loss and nutrient release of both T. bispinosa and V. natans decreased. In addition, initial N:P ratio and cellulose were the major determinants for decomposition in AW and SW treatments while total phenol in B10 and B20. Our results suggest that the combined effect of leaf chemical quality and burial could mediate macrophyte mass loss and release of nutrients and carbon, which in turn can influence organic matter accumulation and nutrient cycling in shallow freshwater lakes.