沉水植物重建对富营养水体氮磷营养水平的影响

利用富营养浅水湖泊(武汉东湖)中所建立的大型实验围隔系统,研究了沉水植物对水体N、P营养水平的影响．结果表明,沉水植物重建后N、P营养水平显著降低．在研究期间,水生植物围隔总N和总P水平均显著低于对照围隔和大湖水体,而且水生植物围隔的总P含量一般维持在0．1mg·L^-1左右。季节性波动远低于对照围隔和大湖水体．水生植物围隔水体中氨态氮和亚硝态氮含量较低．而硝态氮含量与对照围隔和和大湖水体差别不大．由此可见。恢复以沉水植物为主的水生植被,可以有效地降低N、P营养循环速度,控制浮游植物过度增长,是重建富营养湖泊生态系统的重要措施．     

新疆开都河大型水生植物的氮磷化学计量特征及其影响因素

氮 (N)、磷(P)是最常见的限制植物生长的矿质元素。水生植物所需营养主要来源于水体和沉积物,植物体内的元素组成能够反映淡水生态系统的营养供应状况。开都河是新疆一条流经高山草甸和荒漠绿洲的重要内陆河。本研究采集了开都河大型水生植物和水、沉积物样品,分析了不同生活型和发育史的植物物种叶的氮磷化学计量特征,探讨了上下游、不同土地利用类型下植物、水体和沉积物化学计量特征的差异和关联。结果表明: 植物叶的N、P平均含量分别为24.9 mg·g^-1和2.49 mg·g^-1,氮磷质量比值(N/P)平均为12.6。不同生活型植物叶的N、P含量及N/P存在显著差异:沉水植物N、P含量均显著高于浮叶和挺水植物;浮叶植物N/P为19.2,显著高于其他两类植物,表明其生长可能受P的限制。上游水生植物叶的N、P含量均高于下游。同时,河流上游的沉积物和水体中的N含量均高于下游。与农耕区河段相比,草地区河段水生植物的叶N和P含量较高,可能与草地土壤有机质丰富和放牧产生的排泄物有关,说明放牧对开都河水生态系统化学计量特征的影响大于农耕。过度放牧可能使开都河上游水质变差,改变水生态系统的氮磷养分平衡,并最终影响特定区域的生物地球化学循环过程。     

洱海三种生活型水生植物叶片中碳、氮与总酚含量的比较研究

植物体内的C、N和总酚是影响其被牧食和凋落物降解的重要因素,从而影响C和N在食物链的传递和生物地化循环。本研究测定了云南洱海3种生活型（挺水、沉水和浮叶）26种水生植物叶片中C、N和总酚含量以及C/N比率,并分析了它们与总酚的关系。结果表明:挺水植物叶片的C、N和总酚平均含量为448.08、39.30和24.70 mg/g,浮叶植物叶片的C、N和总酚平均含量为433.32、35.16和28.05 mg/g,沉水植物叶片的C、N和总酚平均含量为378.36、27.31和10.28 mg/g;总体上看,植物叶片C和N含量:挺水植物 浮叶植物 沉水植物;挺水和浮叶植物叶片的总酚含量差异不显著,且均远高于沉水植物叶片的总酚含量;26种植物叶片中C和N与总酚含量均呈显著正相关。在富营养化条件下,3种生活型植物所处生境的光照和CO2供给均差异显著,会对这些植物叶片的C、N和总酚含量有一定影响,此外由于应对生境中的胁迫（草食性昆虫、病原体及紫外线辐射等）压力以及自身的生长策略的不同也可能导致C、N和酚在三者中形成差异;通过对13种沉水植物叶片总酚含量比较,推测光叶眼子菜和微齿眼子菜较为适合作为洱海耐牧食恢复先锋物种;N与总酚正相关的关系可能在富营养化进程中加速湖泊沼泽化。     

上海金泽水库典型挺水植物碳、氮、磷化学计量特征的季节变化

为探究不同水生植物碳(C)、氮(N)、磷(P)含量及其化学计量比随季节的变化特征,本研究以上海金泽水库库区四种典型挺水植物旱伞草(Cyperus alternifolius),芦苇(Phragmites australis),千屈菜(Lythrum salicaria),水葱(Scirpus validus)为例,开展了季节性取样及室内分析,结果显示:(1)四种植物碳氮磷含量的变化规律不同。其中,对于植物碳含量,旱伞草和芦苇均无显著差异,千屈菜和水葱仅在冬季显著降低。对于植物氮含量,除旱伞草外,其他植物均在春季生长初期显著降低,在夏季生长旺盛时期显著升高,而旱伞草四季无显著差异。对于植物磷含量,水葱在四季均无显著差异,芦苇和千屈菜在冬季植物休眠期显著降低,旱伞草和芦苇磷含量在夏季显著降低。(2)四种植物C/N/P的季节性变化特征不同。其中,旱伞草C/N四季间无显著差异,其他3种植物C/N在春季生长初期显著升高;在C/P方面,水葱四季间无显著差异,芦苇和千屈菜在春季显著降低,旱伞草和芦苇C/P在夏季显著升高;常绿植物旱伞草N/P在四季无显著差异,其他3种植物N/P均在冬季生物量低时显著升高,春季N/P显著降低,而夏季生物量增长时N/P显著升高。(3)季节变化对四种植物C、P、N/P的影响远大于物种差异的影响,而植物N、C/N、C/P受物种差异的影响程度略大于季节变化。(4)四种植物C/N和C/P分别与N和P呈显著负相关,表明植物C/N和C/P分别受N和P主导;植物C与N、P二者在夏、秋季均无显著相关性,表明起支撑作用的C元素在夏、秋季独立于起生化作用的N、P元素;而营养元素N、P二者含量仅在植物生长的春、夏季显著相关。综上所述,不同植物碳氮磷含量及其化学计量比的季节变化特征不尽相同。今后的研究,可结合相关的生境因子,更好地探究其变化的内在机理。     

水生植物腐烂分解对水质的影响

对6种水生植物进行64 d的腐烂分解试验,对比不同水生植物腐烂分解过程中水体营养盐浓度的变化.结果表明： 6种水生植物的腐烂分解速率差别较大,浮叶植物分解速度最快,沉水植物次之,挺水植物最慢.不同水生植物腐解过程对水质影响不同,并与植物生物量密度相关.挺水植物芦苇腐解过程中的水体化学需氧量、总氮和总磷浓度最低;在茭草分解后期,水体化学需氧量和总氮浓度上升,水质变差.浮叶植物荇菜和莲腐解过程中,水体化学需氧量和总氮浓度高于其他植物.沉水植物菹草和狐尾藻腐解过程中,水体铵态氮、硝态氮和总磷浓度最高.对于同一种植物,不同生物量密度处理下,主要水质指标变化趋势相似.适量的植物残体的存在可以有效促进水体氮、磷等营养元素的循环,一定程度上去除硝态氮,降低水体氮负荷.     

梁子湖湿地植物的氮磷积累特征

采用野外测定结合室内分析的方法,探讨了梁子湖湿地植物对氮磷的积累特征。结果表明,湿地不同植物种类对氮磷的积累特征明显不同。浮游植物积累各种营养物质量最多,其体内全氮量平均为29.07g.kg-1,全磷量平均为9.53g.kg-1。梁子湖湿地各类植物氮磷含量的大小依次为浮游植物>浮叶植物>沉水植物>水稻>挺水植物。各类植物中氮磷积累的大小依次为浮叶植物>挺水植物>沉水植物>沼泽植物>水稻。梁子湖湿地水生植物氮磷营养元素的吸收系数大于湿生植物,各类植物氮元素的吸收系数均大于磷。     

沉水植物生态化学计量学特征的区域差异以及生态修复的影响

为深入了解沉水植物生态化学计量学特征在西南高原地区和长江中下游平原地区湖泊中的差异, 以及生态修复的影响, 于2010年—2016年的夏季(6—9月)调查了36个湖泊的沉水植物。结果表明: (1)高原湖泊沉水植物群落的碳(C)含量显著高于平原湖泊, 氮(N)含量显著低于平原湖泊, 磷(P)含量高于平原湖泊但差异不显著; 高原湖泊沉水植物群落的C/N和C/P的比值显著高于平原湖泊, N/P显著低于平原湖泊; 在平原湖泊和高原湖泊共有的金鱼藻、苦草、穗花狐尾藻、微齿眼子菜和伊乐藻中, 仅有伊乐藻的N含量和金鱼藻的P含量与群落的差异性不一致。(2)在长江中下游平原地区生态修复后的水域中, 沉水植物群落的C和P含量显著高于未修复区, N含量低于未修复区但差异不显著; 修复区沉水植物群落的C/P和N/P显著低于未修复区, C/N显著高于未修复区; 修复区和未修复区共有的金鱼藻、苦草、穗花狐尾藻和竹叶眼子菜的C和P含量都跟群落的差异性一致。以上结果说明, 在清澈的水体中, 沉水植物的C和P含量高而N含量低; 湖泊富营养化会导致沉水植物N含量升高。因此, 在湖泊生态修复过程中, 应注重提高水体的透明度, 这将会提高沉水植物中C和P的含量, 从而有利于促进沉水植被区成为湖泊的C和P库。     

遥感数字图象处理技术在洪湖水生植物分布调查中的应用

本文介绍了遥感数字图像处理技术(影象比值变换、生物量指标变换、灰度值线性拉伸等)在洪湖水域水生植物计算机自动分类中的应用;并配合野外光谱测定和植物样品叶绿素含量测定数据,对挺水、浮叶和沉水植物作计算机自动分类的可能性和可信性进行了分析。文中展示了洪湖水生植物群丛的分类图并统计了各类群的面积。本试验结果为研究洪湖水体及水生植物的演替和湖泊管理提供了有意义的数据。     

富营养湖泊大型围隔和围栏中磷的动态

对武汉东湖大型围隔和围栏中的水生植被和不同形态的磷近2年的调查分析结果表明：在围隔中的水生维管束植物得到恢复、生物量明显大于对照区的情况下,水中的总磷（TP）、溶解活性磷（DRP）、颗粒性磷（PP）浓度明显低于对照区,水生维管束植物的良好生长是导致磷浓度降低的主要因素,总溶解磷（TDP）、溶解非活性磷（DNP）浓度则与对照区无显著差异;围隔（栏）及对照区中TP、PP的浓度秋高冬低,TDP浓度秋、冬季较高,春、夏季较低,DNP浓度春季较高,冬季较低;TP中PP含量约为TDP的4－6倍,DRP与DNP的含量相近或稍有差别。     

氮磷负荷比对浅水湖泊初级生产者的影响

为研究氮磷营养负荷比值(N︰P)的升高对浅水湖泊初级生产者的影响, 在种植刺苦草的模拟系统中, 保证磷(P)负荷不变, 不断增加氮(N)负荷, 设置三种N︰P 比(0︰1、20︰1 和40︰1), 比较不同N︰P 负荷条件下, 浮游植物、附着藻类和沉水植物的生长情况。研究结果表明: 三种不同的N︰P 负荷条件下, 上覆水中总氮(TN)和硝态氮(NO3 – -N)含量随着N︰P 的升高呈现增加的趋势, 总磷(TP)则下降。浮游植物和附着藻类生物量在N︰P 比为20︰1 时出现最大值,显著高于其它两个处理组; 刺苦草的生物量在实验结束时显著增加, 但各处理间没有显著差异。以上结果表明, N︰P 升高能够促进浮游植物与附着藻类的生长, 但超过20︰1 会抑制其生长, 而N︰P 的变化对沉水植物没有显著影响。     

江西省河流水生植被

江西省地处长江中下游交接处的南岸,境内有大小河流2400多条,总长约18400km。江西河流水生植被的组成植物隶属27科,36属,共61种,且可划分为14个主要群落类型,其中以苦草、黑藻、竹叶眼子菜、(艽木)和菹草、微齿眼子菜、金鱼藻等沉水植物群落分布较广,面积较大;而适应流水和水深变化能力较差的挺水、浮叶及漂浮植物仅零星分布在河流边岸、河湾水潭边缘或河滩低洼处等。     

Trends of Superoxide Dismutase and Soluble Protein of Aquatic Plants in Lakes of Different Trophic Levels in the Middle and Lower Reaches of the Yangtze River,China

A limnological study was carried out to determine the responses of superoxide dismutase (SOD) activities and soluble protein (SP) contents of 11 common aquatic plants to eutrophication stress.Field investigation in 12 lakes in the middle and lower reaches of the Yangtze River was carried out from March to September 2004.Our results indicated that nonsubmersed (emergent and floating-leafed) plants and submersed plants showed different responses to eutrophication stress.Both SOD activities of the non-submersed and submersed plants were negatively correlated with their SP contents (P < 0.000 1).SP contents of non-submersed plants were significantly correlated with all nitrogen variables in the water (P < 0.05),whereas SP contents of submersed plants were only significantly correlated with carbon variables as well as ammonium and Secchi depth (SD) in water (P<0.05).Only SOD activities of submersed plants were decreased with decline of SD in water (P < 0.001).Our results indicate that the decline of SOD activities of submersed plants were mainly caused by light limitation,this showed a coincidence with the decline of macrophytes in eutrophic lakes,which might imply that the antioxidant system of the submersed plants were impaired under eutrophication stress.     

几种水生植物腐解过程的比较研究

研究水生植物腐烂分解过程及其养分动态对认识水生态系统物质循环过程具有重要意义。通过室内植物分解模拟试验,对6种水生植物的腐解过程及腐解残余物成分的变化进行了比较研究。结果表明,在64 d的腐解过程中,浮叶植物的分解速率最快,沉水植物其次,挺水植物最慢;同种植物的分解速率及残余物成分变化在不同生物量密度组间存在一定差异,但总体趋势一致。分解过程中,植物残余物中P、纤维素、木质素含量的变化趋势种间差异较小,总体上P含量先迅速下降后缓慢上升,纤维素含量先下降后趋于稳定,木质素含量先上升后趋于稳定;植物残余物中C、N、半纤维素含量在分解初期种间的变化趋势不同,而分解后期则均为C含量上升,N、半纤维素含量趋于稳定。相关性分析结果表明,总体上,在整个分解周期中,初始N、P含量越大分解越快,初始纤维素、半纤维素、木质素含量、C/N、C/P、木质素/N等越大分解越慢;植物腐解不同阶段的质量指标对分解速率的影响有所不同,在分解前期,残余物中N含量越高分解越快,半纤维素含量、C/N、木质素/N越高,分解越慢,而后期木质素含量越高分解越慢,其它因子影响较小。     

Relations between trophic state indicators and plant biomass in Florida lakes

We collected quantitative data on macrophyte abundance and water quality in 319 mostly shallow, polymictic, Florida lakes to look for relationships between trophic state indicators and the biomasses of plankton algae, periphyton, and macrophytes. The lakes ranged from oligotrophic to hypereutrophic with total algal chlorophylls ranging from 1 to 241 mg m^–3. There were strong positive correlations between planktonic chlorophylls and total phosphorus and total nitrogen, but there were weak inverse relationships between the densities of periphyton and the trophic state indicators total phosphorus, total nitrogen and algal chlorophyll and a positive relationship with Secchi depth. There was no predictable relationship between the abundance of emergent, floating-leaved, and submersed aquatic vegetation and the trophic state indicators. It was only at the highest levels of nutrient concentrations that submersed macrophytes were predictably absent and the lakes were algal dominated. Below these levels, macrophyte abundance could be high or low. The phosphorus–chlorophyll and phosphorus–Secchi depth relationships were not influenced by the amounts of aquatic vegetation present indicating that the role of macrophytes in clearing lakes may be primarily to reduce nutrient concentrations for a given level of loading. Rather than nutrient concentrations controlling macrophyte abundance, it seems that macrophytes acted to modify nutrient concentrations.     

An assessment of the importance of emergent and floating-leaved macrophytes to trophic status in the Loosdrecht lakes (The Netherlands)

The potential importance of the six major emergent and floating-leaved macrophyte species in recycling of sediment phosphorus in the Loosdrecht lakes was studied. Representative plant samples were collected at the time of maximum biomass, and analysed for biomass and carbon, nitrogen and phosphorus contents. Species cover was determined by aerial photography.Total cover in the seven lakes studied ranged between 2 and 26 percent. For the four main species, biomass per unit area increased with lake trophic status. Consistent differences in C, N and P contents per unit biomass were not observed. Although cover values were small, significant amounts of C, N and P were contained in the macrophytes when compared with maximum sestonic content.Potential P loads from macrophyte decay were calculated. In Lake Loosdrecht, the P load represented 15 percent of current external P inputs. The potential importance of macrophyte decay to P recycling in the other lakes is greater.Decay of macrophyte species at the end of the growing season appears to affect autumnal nutrient and chlorophyll a levels in the water column of some lakes. The re-establishment of submerged species following lake restoration may increase the importance of this pathway in the lakes.     

The influence of flood duration on the surface soil properties and grazing management of karst wetlands (turloughs) in Ireland

This study tested the hypothesis that lake augmentation with well water impacts the distribution and abundance of aquatic plants in lakes. Water chemistry was measured from 14 wells, 14 augmented lakes, and 14 lakes without augmentation. Nine in-lake aquatic macrophyte abundance and species distribution metrics were measured in all lakes. Net photosynthetic rate (NPR) of nine submersed species was also measured in well and lake water. Augmentation increased alkalinity in receiving lakes, but total phosphorus was significantly lower, which resulted in lower chlorophyll and greater Secchi depths. Although measured NPR was higher for all plants incubated in well water, only one (emergent species richness) in-lake aquatic macrophyte metric was different in lakes with and without augmentation. Lake augmentation significantly changed water chemistry of receiving waters, but effects on aquatic macrophytes were minimal, suggesting that other environmental factors are limiting the distribution and abundance of macrophytes in the study lakes. The lower phosphorus levels in augmented lakes were unexpected because phosphorus concentrations in well water were significantly greater than in lakes with or without augmentation. Precipitation of calcium phosphate likely accounts for the reduced phosphorus levels in augmented lakes.     

Environmental factors influencing chlorophyll v. nutrient relationships in lakes

SUMMARY. 1. A model relating log chlorophyll a concentration to log epilimnetic total phosphorus (TP) concentration was re-examined based on: (a) comparative and temporal studies of four stratifying Wisconsin and other highly eutrophic temperate lakes; (b) comparative summer lake surveys from Iowa and Alberta.
2. Although P-limited, deeper lakes with long hydraulic residence times and low external and internal nutrient loading in summer had summer chlorophyll a yields below model predictions based on spring and summer epilimnetic TP concentrations.
3. For lakes with summer epilimnetic TP between 30 and 80 mg m⁻³, chlorophyll a concentrations exceeded model predictions based on summer TP. This relationship held even for Lake Delavan, Wisconsin, where the ratio of available N to P was unfavourably low during spring turnover, and where the trans-thermocline N:P flux ratio was sub-optimal for algal needs in early summer.
4. With increasing summer TP concentrations and/or increasing epilimnetic circulation depth (>5m), chlorophyll a concentrations fell below model predictions—independent of the potential for N-limitation. This plateauing in chlorophyll a response occurred at lower epilimnetic TP content (−2) in lakes with elevated non-algal light extinction coefficients. Using Tailing's algorithm for the'column compensation point' (algal photosynthesis = algal respiration over diel cycle), light limitation best explains this fall-off in chlorophyll a yield.
5. The failure of the Dillon & Rigler (1974) spring TP v . summer chlorophyll a model for these Wisconsin lakes is unrelated to N-limitation. Instead, it reflects internal adjustment in take TP in response to stratification and seasonal external P loading.     

泥沙埋深对苦草和微齿眼子菜及两物种混合分解的影响

为探讨泥沙淤积对水生植物分解的影响,研究了沉水植物苦草(Vallisneria natans)、微齿眼子菜(Pota-mogeton maackianus)及两物种混合在底泥中不同埋深(0 和5 cm)的分解速率和养分动态,实验周期为117d。结果显示:(1)在0和5 cm埋深处理下,苦草、微齿眼子菜及两物种混合的分解速率均表现为苦草最快,微齿眼子菜最慢,物种混合介于两单种之间。与0 cm处理相比,在5 cm埋深处理下苦草、微齿眼子菜及两物种混合的分解速率显著降低(P0.05)。苦草在0和5 cm埋深处理下分解35天后干重剩余率分别为0和43.51%、在5 cm处理下分解82d后干重剩余率为0。微齿眼子菜和两物种混合在5 cm埋深处理下分解117d后的干重剩余率分别提高了31.09%和37.44%。(2)与0 cm处理相比,5 cm埋深处理显著抑制苦草、微齿眼子菜及两物种混合的N、P释放。苦草在0和 5 cm埋深处理下分解35天后N剩余率分别为0和31.28%、P剩余率分别为0和24.45%。在5 cm埋深处理下分解117天后微齿眼子菜N和P剩余率分别提高了19.45%和14.73%、两物种混合N、P剩余率分别提高了41.57%和22.82%。(3)两物种混合在0和5 cm埋深处理下,其分解速率均表现为加和效应,但N、P元素释放在0 cm处理下分别表现为协同效应和加和效应,在5 cm埋深处理下均表现为拮抗效应。(4)随着分解的进行,5 cm埋深处理下的苦草和微齿眼子菜的微生物呼吸速率均显著降低,物种混合的微生物生物量始终低于0 cm处理。这些结果表明泥沙埋深显著降低了苦草、微齿眼子菜及两物种混合的分解速率和N、P元素释放,物种混合的N、P元素释放在分解后期均因沉积作用而产生了拮抗效应。此外,泥沙埋深对分解的抑制作用与微生物呼吸及生物量降低有密切的关系。研究结果可为认识水生植物分解对沉积作用的响应机制提供资料,并为了解水生植物分解对底质营养动态的影响提供参考。