利用人工围隔研究沉水植被恢复的生态效应

近几十年来,随着水体富营养化加剧和其它人类活动影响,一些湖泊,尤其是我国长江中下游地区浅水湖泊中,沉水植被锐减甚至消失。如武汉东湖,６０年代十分繁茂的沉水植被现已濒临灭绝。沉水植被作为主要初级生产者,在水生态系统中起着一定的作用。在退化湖泊生态系统重建与恢复中,重建沉水植被是关键性的步骤。本研究利用人工围隔,在富营养化水体中重建沉水植被,通过与近旁无沉水植被的湖区对照,从水体理化性质、浮游植物叶绿素ａ含量以及原生动物群落结构与多样性几个方面,研究沉水植被恢复的生态效应,以期为退化湖泊生态系统的重…     

梁子湖、牛山湖和保安湖沉水植被资源现状

在长江中下游浅水湖泊的水生植被中,沉水植被是最重要的植被类型。研究沉水植被资源量对湖泊生态系统及渔业管理都具有重要意义。本工作调查梁子湖、牛山湖和保安湖沉水植被的种类、生物量及覆盖度,并与以前研究相比较,以了解三个湖泊沉水植被资源现状以及变动趋势。       

武汉东湖后湖区浮游甲壳动物群落结构的研究

武汉东湖后湖湖区浮游甲壳动物群落结构从60年代至90年代发生了十分显的变化。浮游甲壳动物的物种丰度下降非常明显,枝角类的种类数从60年代的47种下降至90年代的17种,桡足类的种类数由60年代的14种下降为90年代的9种。60年代枝角类的优势种隆线Sou一亚种在90年代被短尾秀体Sou所取代,60年代的两种优势哲水蚤－长江新镖水蚤与特异荡镖水蚤的优势在90年代消失,而60年代很少的一种剑水蚤－台湾温剑水蚤在90年代跃升为优势种。随着滤食性鱼类密度的上升,枝角类的密度从60年代至90年代显下降。哲水蚤1997及1998年的密度明显低于60年代的密度。研究表明,浮游甲壳动物群落物种丰度的下降与后湖湖区沉水植被的退化有关,而优势种的演替主要受滤食性鱼类密度的影响。     

武汉月湖水生植被重建的实践与启示

通过生物操纵、浮水植物和植物浮岛原位净化、岸边人工湿地净化和科学种植等措施,2－3年内,在长江中游地区、面积为0.66km2、水质为劣Ⅴ类的重富营养湖泊武汉月湖重建了以菹草和伊乐藻为优势种的沉水植物先锋群落,2005年春季的沉水植物盖度达到45％,提高了透明度。利用水位低、透明度相对高的冬季种植伊乐藻、菹草等适合冬春季生长的沉水植物是建立沉水植物先锋群落的一个有效途径。重污染水体过低的透明度是重建沉水植被的主要限制因子,在低水位或较高透明度时期,水生植物可以耐受相对较高的污染负荷,并且在有条件降低水位时,会大大提高重建沉水植被的成功率。重建并保持长期稳定的水生植被必须截污,并把营养盐浓度削减到一定范围内。水生植被重建初期是最脆弱的时期,水位、污染负荷等生态因子的较大波动很容易破坏植物群落,在这一时期要尽量保持关键因子的稳定,注意控制浮萍的扩张,使形成的生态系统逐步走向成熟。清除鱼类对提高水的透明度有重要作用,但必须伴随着水生植被的恢复或重建才能维持长久的良好效果。     

伊乐藻、苦草和菹草对磷急性胁迫的响应

水生植被,特别是沉水植被的衰退和消失是水体富营养化过程中的普遍现象[1,2],其原因是多方面的,但较高的水柱氮、磷浓度显然是重要原因之一.     

长江洞庭湖口原生动物的生态学研究

对长江洞庭湖口原生动物群落为期三年的研究结果:种类组成、季节分布、优势种类、丰度的季节变化等,同时还依据食性分析了各种类的功能营养类群,并对河流中原生动物的来源、长江中上游地区原生动物种类组成规律、原生动物功能营养类群和优势种类在河流污染监测中的指示作用等进行了讨论.       

长江洞庭湖口原生动物的生态研究

对长江洞庭湖口原生动物群落为期三年的研究结果,种类组成,季节分布、优势种类、丰度的变化等,同时还依据食性分析了各种类的功能营养类群,并对河流中原生动物地来源、长江中上游地区原生动物种类组成规律,原生动物功能营养类群和优势在在河流污染监测中的指示作用等进行了讨论。     

三北地区内陆盐水的原生动物

1990-1991年在三北地区盐度0.57-214‰的28个内陆水体,采集了162号浮游动物水样.共见到原生动物58种,其中肉足虫13种,纤毛虫45种.结果表明,原生动物,特别是纤毛虫类是内陆盐水浮游动物群落结构的重要组成部分,在一些超盐水体往往密度较大,有时成为优势种.随着盐度升高,原生动物总种数和多样性指数均趋于减小,而其密度和生物量却显着增大.文中讨论了内陆盐水原生动物区系的种类组成和分布及其与环境因子的关系.       

对虾养殖池塘底质修复技术对原生动物群落结构的影响

在对虾养殖池塘水体中共检测到原生动物86种,其中纤毛虫48种;鞭毛虫25种,肉足虫13种.原生动物优势种主要由一些运动能力相对较弱或固着生长的种类组成,如褐砂壳虫(Difflugia avellana)、瓜形膜袋虫(Cyclidium citrullus)、透明鞘居虫(Vaginicola crystalline)、多态喇叭虫(Stentor polymorphrus)和钟虫(Vorticella sp.)等,这些原生动物有以腐质和藻类为食、耐污性较强的特点.结果表明:在养殖初期,使用底质修复技术的试验池塘原生动物群落结构恢复比对照塘快,PFU群集的原生动物种类数和密度比对照塘多,水质比对照塘好,嗜污性相对较强的一些纤毛虫如尾草履虫(Paramecium caudaium)、拟瘦尾虫(Paruroleptus spp.)等比对照塘出现晚.在随后的养殖过程中,使用底质修复技术的试验塘原生动物群落结构比对照塘稳定,原生动物种类数和密度起伏小,pH值、透明度变化幅度也小于对照池塘,没有发生病害,水质较对照塘好.     

淀山湖浮游动物的群落结构及动态

为帮助利用生物操纵技术进行淀山湖水体富营养化治理,2004年1月至2005年12月对淀山湖浮游动物群落结构,包括种类组成、种群动态、现存量进行了2周年的系统调查.淀山湖浮游动物有128种,其中浮游原生动物23属29种、轮虫23属51种、枝角类15属33种、桡足类15种.年均密度6 965ind/L,原生动物和轮虫分别占62.19%和36.77%,密度高峰出现在春季;生物量年均为6.00mg/L,以轮虫和枝角类占优势,分别占51.65%和38.38%,生物量高峰出现在夏季.4个类群浮游动物多样性指数H'与其均匀度指数J呈显著正相关,原生动物群落多样性指数H'与其密度呈显著负相关.根据浮游动物密度及优势种组成特征判断,淀山湖水质为富营养型.原生动物多样性指数具有较好的水质指示作用.     

Invasive Crayfish Threaten the Development of Submerged Macrophytes in Lake Restoration

Submerged macrophytes enhance water transparency and aquatic biodiversity in shallow water ecosystems. Therefore, the return of submerged macrophytes is the target of many lake restoration projects. However, at present, north-western European aquatic ecosystems are increasingly invaded by omnivorous exotic crayfish. We hypothesize that invasive crayfish pose a novel constraint on the regeneration of submerged macrophytes in restored lakes and may jeopardize restoration efforts. We experimentally investigated whether the invasive crayfish (Procambarus clarkii Girard) affects submerged macrophyte development in a Dutch peat lake where these crayfish are expanding rapidly. Seemingly favourable abiotic conditions for macrophyte growth existed in two 0.5 ha lake enclosures, which provided shelter and reduced turbidity, and in one lake enclosure iron was added to reduce internal nutrient loading, but macrophytes did not emerge. We transplanted three submerged macrophyte species in a full factorial exclosure experiment, where we separated the effect of crayfish from large vertebrates using different mesh sizes combined with a caging treatment stocked with crayfish only. The three transplanted macrophytes grew rapidly when protected from grazing in both lake enclosures, demonstrating that abiotic conditions for growth were suitable. Crayfish strongly reduced biomass and survival of all three macrophyte species while waterfowl and fish had no additive effects. Gut contents showed that crayfish were mostly carnivorous, but also consumed macrophytes. We show that P. clarkii strongly inhibit macrophyte development once favourable abiotic conditions for macrophyte growth are restored. Therefore, expansion of invasive crayfish poses a novel threat to the restoration of shallow water bodies in north-western Europe. Prevention of introduction and spread of crayfish is urgent, as management of invasive crayfish populations is very difficult.     

不同生活型大型植物对浮游植物群落的影响

湖泊加速富营养化是世界范围内的普遍现象,由此造成水质恶化,藻类大量增生,水生植被特别是沉水植物衰退乃至消失,生物多样性降低,严重影响湖泊主要功能的发挥。大型植物与浮游植物都是浅水湖泊的初级生产者,其间存在复杂的相互关系,如除竞争作用外,还可能存在相生...     

Fish community assemblages changed but biomass remained similar after lake restoration by biomanipulation in a Chinese tropical eutrophic lake

While the effects of lake restoration by fish manipulation are well-studied in the temperate zone, comparatively little information is available on this issue from tropical lakes. It may be expected that fish removal leads to faster recovery of the fish stock here than in temperate lakes due to more frequent and earlier reproduction, which may, in turn, delay positive effects of the restoration. We studied the community composition, feeding type and abundance of fish in three basins of a tropical shallow lake: one unrestored basin (UR) and two basins restored by fish manipulation and transplantation of submerged macrophytes. While omni-benthivorous fish dominated the biomass in the restored basins 3 and 5 years after restoration, planktivores were most abundant in the UR, although total fish biomass remained similar. One-way analyses of similarities based on fish species presence/absence, abundance and biomass data revealed significant differences in fish community composition among the restored basins and UR, and redundancy analyses further indicated that submerged macrophytes were a key driver behind this difference. Our results indicate that active implantation of submerged macrophytes to stabilise the fish community is a tool to consider when planning lake restoration by biomanipulation in the tropics.     

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．     

Effects of vegetation state on biodiversity and nitrogen retention in created wetlands: a test of the biodiversity–ecosystem functioning hypothesis

1. Nitrogen retention in wetlands provides an example of an ecosystem function that is desired by human society, and is a rationale for the creation of wetlands to decrease nitrogen fluxes from nitrate‐loaded river catchments to coastal waters. 2. Here, we tested the impact of different vegetation states on species diversity and nitrogen retention during 4 years in surface‐flow wetlands receiving nitrate‐rich water. Tall emergent vegetation or submerged vegetation was introduced to six experimental wetlands each and six wetlands were left as unplanted controls for free development of vegetation. This resulted in three vegetation states dominated by emergent vegetation, by a mixture of submerged vegetation and filamentous green algae or by filamentous green algae. 3. Species diversity (species richness and Shannon diversity) of plants was initially lowest in free development wetlands, but during the study became lower in the emergent vegetation wetlands than in the other wetlands. Diversity of macroinvertebrates was initially lower in the submerged vegetation wetlands than in the other wetlands, but this difference disappeared during the study. Nitrogen retention was consistently higher in emergent vegetation wetlands than in the other wetlands throughout the study. 4. We conclude that plant diversity in wetlands dominated by tall emergent vegetation gradually became lower than in other wetlands, due to dominant species competitively excluding other plants. However, these wetlands were more efficient at removing nitrogen than those dominated by filamentous algae or submerged macrophytes. 5. Management of wetlands often aims to decrease the dominance of tall emergent vegetation for the benefit of plant species diversity and habitat heterogeneity. Our results demonstrate a biodiversity benefit, but also show that this strategy may decrease the ability of wetlands to remove nitrogen. In this case, there is no support for the hypothesis that biodiversity enhances ecosystem function.     

Climate warming and heat waves affect reproductive strategies and interactions between submerged macrophytes

Extreme climatic events, such as heat waves, are predicted to increase in frequency and intensity during the next hundred years, which may accelerate shifts in hydrological regimes and submerged macrophyte composition in freshwater ecosystems. Since macrophytes are profound components of aquatic systems, predicting their response to extreme climatic events is crucial for implementation of climate change adaptation strategies. We therefore performed an experiment in 24 outdoor enclosures (400 L) separating the impact of a 4 °C increase in mean temperature with the same increase, that is the same total amount of energy input, but resembling a climate scenario with extreme variability, oscillating between 0 °C and 8 °C above present conditions. We show that at the moderate nutrient conditions provided in our study, neither an increase in mean temperature nor heat waves lead to a shift from a plant‐dominated to an algal‐dominated system. Instead, we show that species‐specific responses to climate change among submerged macrophytes may critically influence species composition and thereby ecosystem functioning. Our results also imply that more fluctuating temperatures affect the number of flowers produced per plant leading to less sexual reproduction. Our findings therefore suggest that predicted alterations in climate regimes may influence both plant interactions and reproductive strategies, which have the potential to inflict changes in biodiversity, community structure and ecosystem functioning.     

西太湖水生植物时空变化

水生植物在浅水湖泊生态系统中具有十分重要的作用。根据中国科学院太湖湖泊生态系统研究站1989年以来的常规监测资料,将西太湖（除东太湖以外的湖区）划分为9个区,采用点截法（point intercept method）,于2002～2005年对各区水生植物的种类、生物量和空间分布情况进行了6次调查。结果表明：西太湖现有水生植物16种,分属于11科12属;水生植物总面积约10220hm^2,其中沉水植物分布面积约占64．58％;挺水植物约占0．29％;漂浮植物约占38．16％。各个种之间生物量差异显著,马来眼子菜、荇菜、芦苇的生物量在所有水生植物中居前3位。多样性分析表明,水生植物种类4a来未发生明显变化,但种类和生物量季节性差异较大。水生植物呈环状分布在距湖岸5km以内的水域和部分岛屿周围,东岸和南岸为水生植物的主要集中分布区域,分布区连续性好,且水草种类齐全。挺水植物种类单一,仅有芦苇（Phragmites communis）一种,分布区域多限于水深小于1．6m的湖岸;沉水植物共有8种,为水生植物的主要组成部分,马来眼子菜（Potamogeton malaianus）的分布频度最高,在西山岛周围水域逐年扩张,成为该区域的先锋种;漂浮植物3种,主要以荇菜（Nymphoides peltata）为主,在七都水域有逐渐扩张的趋势。马来眼子菜、芦苇、荇菜表现出对水环境较强的适应能力,目前为西太湖的3个优势种。20世纪50年代以来,西太湖水生植物种类减少了50种,其中水质下降是导致水生植物种类不断减少甚至消失的一个重要原因。围网养殖和不合理的捕捞方式也对局部水域的植物造成极大的破坏。水生植物生存环境日益严峻,种群单一化趋势日益明显。     

Recovery of the fish community and changes in the lower trophic levels in a eutrophic lake after a winter kill of fish

A severe oxygen deficit induced a fish kill in the eutrophicated two-basin Lake Äimäjärvi in southern Finland during winter 2002–2003, resulting in cascading effects on the lower trophic levels of the lake. Pikeperch disappeared from the lake and bleak and white bream decreased to low numbers. The recovery of the populations of other species started immediately when strong year-classes of roach and perch appeared in summer 2003 and onwards. A sharp increase in the growth of perch and roach was recorded, and perch became the dominant fish species during 2004–2006. Consequent responses after the fish kill included increased Secchi depth, expansion of submerged macrophytes, decreased nutrient concentrations and reduction of Cyanophyta from the more eutrophic northern basin of the lake, and a temporary increase in the size of Daphnia in the early summer 2003. However, the ecosystem of the lake returned gradually to the earlier structure and level of eutrophication. Bluegreen algae have returned since 2005, the water has become more turbid, macrophytes declined in 2007 and the fish community was again dominated by small cyprinid fishes in 2008.     

水生植物对富营养水体水质净化作用研究

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,对沉水植物的水质净化作用作了现场实验研究。重建后的沉水植物可以显著改善水质,水体透明度显著提高,水色降低。在研究期间,水生植物围隔CODcr和BOD5一般分别为20和5mg/L左右;对照围隔和大湖水体则分别约为40和10mg/L。水生植物围隔水体中检出的有机污染种类也较对照围和大湖水体柢。实验结果表明恢复以沉水植物为主的水生植被是改善营养湖泊水质和重建生态系统的有效措施。