沉水植物中挥发性物质对铜绿微囊藻的化感作用

比较了两种淡水沉水植物金鱼藻和苦草中挥发性物质对铜绿微囊藻的化感抑制作用,在100mg／L浓度下,新鲜植物挥发油的抑藻作用非常显著,两种植物抑藻活性相近,但是在干粉材料中金鱼藻挥发油的抑藻活性明显强于苦草,且挥发油浓度与抑藻活性呈正相关。不同植物之间以及新鲜植物和植物干粉之间挥发油的成分和相对含量差别较大,新鲜植物挥发油中含有40％的邻苯二甲酸酯,而在于粉挥发油中70％为脂肪族化合物和萜类物质。在新鲜植物挥发油中约占20％的是不稳定的未知物,其化学结构和生物活性有待进一步研究。     

Increasing canopy shading reduces growth but not establishment of Elodea nuttallii and Myriophyllum spicatum in stream channels

In aquatic environments around the globe, rooted macrophytes have been replaced by filamentous macroalgae. The consequences of such shifts in vegetative habitat for fauna are poorly understood. Given differences in morphology and life history characteristics of rooted macrophytes and filamentous macroalgae, we hypothesized that these habitat types were not functionally redundant for small-bodied fishes and macroinvertebrates. We examined this hypothesis in spring-fed Florida rivers characterized by decreases in native rooted macrophytes and concomitant increases in filamentous macroalgae. Although faunal densities were generally greater in filamentous macroalgae than in rooted macrophytes, differences in the community assemblage structure suggest that the two types of vegetative habitat do not function interchangeably. Accordingly, continued replacement of rooted macrophytes with filamentous macroalgae is expected to affect the small fish and macroinvertebrate community, as well as higher trophic levels that depend on it.     

Biological control of phytoplankton by the subtropical submerged macrophytes Egeria densa and Potamogeton illinoensis: a mesocosm study

1. In temperate regions, submerged macrophytes can hamper phytoplankton blooms. Such an effect could arise directly, for instance via allelopathy, or indirectly, via competition for nutrients or the positive interaction between submerged macrophytes and zooplankton grazing. However, there is some evidence that the positive interaction between submerged macrophytes and zooplankton grazing is less marked in warmer regions, where the interaction is less well studied, and that negative effects of higher water plants on phytoplankton biomass are weaker. 2. We carried out two consecutive mesocosm experiments in Uruguay (subtropical South America) to study the effects of two common submerged macrophytes from this region (Egeria densa and Potamogeton illinoensis) on phytoplankton biomass, in the absence of zooplankton grazing. We compared phytoplankton development between different macrophyte treatments (no macrophytes, artificial macrophytes, real Egeria and real Potamogeton). We used artificial macrophytes to differentiate between physical effects (i.e. shading, sedimentation and competition with periphyton) and biological effects (i.e. nutrient competition and allelopathy). 3. In Experiment 1, we found no evidence for physical effects of macrophytes on phytoplankton biomass, but both macrophyte species seemed to exert strong biological effects on phytoplankton biomass. Only Egeria affected phytoplankton community structure, particularly tempering the dominance of Scenedesmus. Nutrient addition assays revealed that only Egeria suppressed phytoplankton through nutrient competition. 4. We performed a second mesocosm experiment with the same design, but applying saturating nutrient conditions as a way of excluding the effects of competition for nutrients. This experiment showed that both macrophytes were still able to suppress phytoplankton through biological mechanisms, providing evidence for allelopathic effects. Our results indicate that both common macrophytes are able to keep phytoplankton biomass low, even in the absence of zooplankton grazing.     

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。     

基于化感物质释放特性的沉水植物抑藻作用模式研究进展

沉水植物对藻类的化感抑制作用,是沉水植物获取竞争优势和维持清水稳态的重要机制之一。化感物质是由植物产生并释放到水环境中的次生代谢产物,化感物质的有效释放和作用是实现沉水植物化感抑藻作用的关键环节。因此,在化感物质释放水平阐明沉水植物化感抑藻的作用模式、过程和机制具有重要意义。通过比较沉水植物化感物质释放到水环境中的种类、含量和常规急性毒性测试中化感物质的抑藻效果,发现沉水植物化感物质在释放水平上的作用模式不同于常规急性毒性试验中的单次作用。为了回答沉水植物化感物质在释放水平如何高效抑藻的问题,结合化感物质的释放特性,重点从化感物质的联合作用和持续作用等角度探讨沉水植物化感抑藻的作用模式,提出沉水植物可能通过多种化感物质低剂量持续释放的方式,实现对目标藻类的持续协同控制。今后有必要进一步结合沉水植物与目标藻类的共存系统与原位实验,借助分析化学、植物化学、细胞和分子生物学的技术手段,从生态学水平加强沉水植物化感抑藻作用机制研究。     

Role of macrophytes in the variability of zooplankton community structure in the littoral zone of shallow lakes

Distribution, diurnal variability, aggregation of zooplankton in the littoral zone of lakes and effect of various macrophyte species on the structure of its community are considered. It is shown that the horizontal migrations of zooplankton, both direct and reverse ones, are caused mainly by the pressure of fish. The effect of predacious zooplankton is less important and is directed mainly at small-sized species. The intensity of horizontal migrations of zooplankton decreases with depth, while the effect of shore avoidance is observed for the large-sized zooplankton species and is caused not only by the pressure of fish but also by other factors, most likely abiotic. The problem of interaction between macrophytes and zooplankton cannot be reduced to the role of macrophytes as a refuge. Allelopathic properties of macrophytes, competitive relations between separate zooplankton species in macrophyte thickets, as well as the effect of predacious invertebrates associated with macrophytes on zooplankton remain unclear. The role of macrophytes as a factor causing changes in hydrodynamic processes in the littoral regions of lakes is also unknown.     

Effects of phytoplankton on the distribution of submerged macrophytes in a small canal

Submerged macrophytes have been disappearing from the Kanto Plain, Japan since the 1960s. This disappearance is usually attributable to the interaction between macrophytes and phytoplankton. Phytoplankton contributes to shading of the available light and changes the availability of inorganic carbon from free CO₂ to HCO ₃ ^? for use in photosynthesis. However, limited information is available about the interaction between carbon fraction and submerged macrophytes through phytoplankton abundance. In this short note, we observe the distribution of submerged macrophytes and phytoplankton in a small canal. We found that, despite high photosynthetically active radiation (PAR) in the downstream region, low free CO₂ concentration through phytoplankton abundance can deplete free CO₂ for submerged macrophytes. In contrast, the upstream region exhibited macrophytes in an environment with high free CO₂ concentration. The stable carbon isotope ratio of submerged macrophytes follows this pattern, with more positive values occurring in the downstream region and more negative values in the upstream region. It has been reported that phytoplankton limits light availability for submerged macrophytes, but carbon availability could also be a factor in the distribution of submerged macrophytes. Because the source of water for submerged macrophytes is groundwater, its preservation possibly plays a key role for the restoration of submerged macrophytes.     

不同初始螺类密度对沉水植物刺苦草Vallisneria spinulosa Yan及其附着藻类的影响

大型水生植物及其附着藻类是浅水湖泊中的重要初级生产者。淡水螺类作为重要的初级消费者,其密度对沉水植物及其附着藻类的影响存在争议。本研究设置4种初始螺类密度（0、40、80、240 ind·m^-2）,研究淡水螺类（椭圆萝卜螺Radix swinhoei H.Adams）对刺苦草（Vallisneria spinulosa Yan）及其附着藻类的直接牧食作用和螺类种群的变化。结果显示,在添加螺处理中,刺苦草和人工基质表面附着藻类的生物量显著降低,同时沉水植物的生长显著增加,在较高初始密度螺类处理中刺苦草产生更多的分株。到实验结束时,螺类的死亡率较高,但3个有螺处理间螺类鲜重无显著差异,而高初始密度螺类条件下的最终密度仍较高,同时个体重量（均重）也较小。在中富营养条件下淡水螺类可以直接牧食沉水植物叶片,但对植物生长的抑制作用不显著,有可能是因为沉水植物并不能作为唯一的食物来源维持螺类种群,同时螺类的种群结构受到水体营养水平等因素的制约。     

New paradigms in tropical limnology: the importance of the microbial food web

Biological invasions of aquatic plants (i.e., macrophytes) are a worldwide phenomenon, and within the last 15 years researchers have started to focus on the influence of these species on aquatic communities and ecosystem dynamics. We reviewed current literature to identify how invasive macrophyte species impact fishes and macroinvertebrates, explore how these mechanisms deviate (or not) from the accepted model of plant–fish interactions, and assess how traits that enable macrophytes to invade are linked to effects on fish and macroinvertebrate communities. We found that in certain instances, invasive macrophytes increased habitat complexity, hypoxia, allelopathic chemicals, facilitation of other exotic species, and inferior food quality leading to a decrease in abundance of native fish and macroinvertebrate species. However, mechanisms underlying invasive macrophyte impacts on fish and macroinvertebrate communities (i.e., biomass production, photosynthesis, decomposition, and substrate stabilization) were not fundamentally different than those of native macrophytes. We identified three invasive traits largely responsible for negative effects on fish and macroinvertebrate communities: increased growth rate, allelopathic chemical production, and phenotypic plasticity allowing for greater adaptation to environmental conditions than native species. We suggest that information on invasive macrophytes (including invasive traits) along with environmental data could be used to create models to better predict impacts of macrophyte invasion. However, effects of invasive macrophytes on trophic dynamics are less well-known and more research is essential to define system level processes.     

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.     

Effects of macrophytes on lake‐water quality across latitudes: a meta‐analysis

Macrophytes are widely recognized for improving water quality and stabilizing the desirable clear‐water state in lakes. The positive effects of macrophytes on water quality have been noted to be weaker in the (sub)tropics compared to those of temperate regions. We conducted a global meta‐analysis using 47 studies that met our set criteria to assess the overall effects of macrophytes on water quality (measured by phytoplankton chlorophyll a concentration, total nitrogen concentration, total phosphorus concentration, Secchi depth and the trophic state index) and to investigate how these effects correlate with latitude using meta‐regressions. We also examined if the effects of macrophytes on lake‐water quality differ with growth form and study design in (sub)tropical and temperate areas by grouping the data and then comparing the effect sizes. We found that macrophytes significantly reduced phytoplankton chlorophyll a concentration, total nitrogen concentration, total phosphorus concentration, as well as the trophic state index, but they did not have a significant overall effect on Secchi depth. The effects of macrophytes on reducing phytoplankton chlorophyll a concentration, total nitrogen concentration and the trophic state index did not differ with latitude. However, the reduction of total phosphorus concentration was greater at lower latitudes. We showed that at lower latitudes, the positive effects of macrophytes on water quality are similar to or greater than those at higher latitudes, thus challenging the prevailing paradigm of macrophytes being less effective at enhancing lake‐water quality in the (sub)tropics. Furthermore, our data showed that the macrophyte effects vary by growth forms, and the growth forms that positively affect water quality differ between the (sub)tropical and temperate areas. We showed a lack of significant macrophyte effects in surveys within and outside macrophyte stands, suggesting difference in the sensitivities of study designs or possibly weaker effects of macrophytes in lakes compared to experimental settings.     

沉水植物功能性状研究的思考

植物的功能性状是指植物体具有的与生长、存活和繁殖紧密相关的一系列核心植物属性,这些性状通常有非常重要的生态学意义。目前,基于植物功能性状的研究已经快速扩展到生态学研究的众多领域。沉水植物是一类与水环境关系密切的生态类群,对浅水湖泊生态系统的结构和功能有重要的意义。之前对功能性状研究主要集中在陆生木本植物,尚无对沉水植物（沉水草本）功能性状的综述。本研究根据沉水草本与陆生植物功能性状的差异,基于陆生植物功能性状研究中的几个重要问题对现有沉水草本植物功能性状的研究进行归纳和梳理。最后对未来沉水植物功能性状的研究方向进行了展望,提出在当前全球气候变化背景下,功能性状研究也可用于指导淡水生态系统的修复。     

螺类与着生藻类的相互作用及其对沉水植物的影响

浅水湖泊的富营养化常导致水生植被的退化与浮游藻类的爆发［１０,１８,２９］。可利用光通常是决定沉水植物分布、生物量和生产力的最重要因子,因此,伴随高营养负荷的浮游藻类繁殖,极大地削弱了沉水植物的光合能力［２０］。然而,Ｐｈｉｌｉｐｓ等人［２８］认为,...     

Transport and deposition of macrophytes to the dysphotic bottom of coastal waters

Some macrophytes are transported to the deep-sea bottom and are utilized by heterotrophs in the deep-sea as a food source. We inferred the transport route of macrophytes toward the deep-sea based on similarity in the species compositions of macrophyte pieces collected from the dysphotic bottom off the Izu Peninsula and the drifting macroalgae reported for the study area. We also examined whether or not the macrophytes are buried in the sediment, based on stable isotope distributions of organisms. Macrophytes collected by dredging at a depth of 100-300 m included 93 species, whereas 43 species were found by trawling at depths from 200 to 400 m. Only 15 of 76 dredged species (19.7%) that were identified to the species level were identical to the drifting macroalgal species reported for this area, whereas 15 of the 29 trawled species (51.7%) that were identified to the species level were identical to the reported drifting species. It was thus inferred that macrophytes were mainly transported through sliding along the sea bottom for the macrophytes collected by dredging and through sinking from the surface water for the macrophytes collected by trawling. The δ¹³C of sedimentary organic matter (SOM) from the 200-300 m zone was similar to the δ¹³C distribution of particulate organic matter in the surface water reported for the study area. The SOM in the zone likely originated from almost exclusively phytoplankton. In contrast, the ¹³C of SOM was significantly more enriched in shallow areas ≤100 m deep. We infer that not only phytoplankton but also macrophytes could supply organic matter to heterotrophs on the shallow bottom.     

The influence of plant-associated filter feeders on phytoplankton biomass: a mesocosm study

Low phytoplankton biomass usually occurs in the presence of submerged macrophytes, possibly because submerged macrophytes enhance top-down control of phytoplankton by offering a refuge for efficient grazers like Daphnia against fish predation. However, other field studies also suggest that submerged macrophytes suppress phytoplankton in the absence of Daphnia. In order to investigate these mechanisms further, we conducted an outdoor mesocosm experiment to study the effect of submerged macrophytes (Elodea nuttallii) on phytoplankton and zooplankton biomass. The experiment combined four nutrient addition levels (0, 10, 100, and 1000 μg P l⁻¹; N/P ratio: 16) with three macrophyte levels (no macrophytes, artificial macrophytes, and real macrophytes). We inoculated the tanks with species-rich inocula of phytoplankton and zooplankton but excluded fish or macro-invertebrates. Probably due to the lack of predators in the mesocosms, potential grazing rates of pelagic zooplankton (estimated from zooplankton biomass) did not differ between the macrophyte treatment combinations. Compared to the treatment combinations without macrophytes, lower phytoplankton biomass occurred in the treatment combinations with real macrophytes at all the nutrient addition levels and in those with artificial macrophytes at all the nutrient levels except the highest. Significantly, higher abundances of plant-associated filter feeders (Simocephalus vetulus and Ceriodaphnia spp.) occurred in the treatment combinations with real and artificial macrophytes. The estimated potential grazing rate of these plant-associated filter feeders indicated that these filter feeders could be responsible for the lower phytoplankton biomass in the presence of real and artificial macrophytes. Our results suggest that the plant-associated filter feeders may be significant grazers in vegetated shallow lakes.     

基于水下光照条件和种子库分布指示沉水植物恢复区: 以金湖为例

研究以湖北枝江金湖(由东湖和刘家湖组成)为例, 综合水下光照条件和沉水植物种子库分析, 探讨沉水植物可恢复区的判别方法。研究分别于2018年6月和12月对金湖开展了综合调查, 并在6月开展了种子库调查。结果表明, 金湖富营养化问题较严重, 6月各位点水深-透明度比值均低于沉水植物生长的阈值需求, 范围为0.13—0.25, 平均为0.17; 12月部分位点的水深-透明度比值达到了沉水植物生长的阈值需求, 范围为0.18—0.95, 平均为0.44。各位点沉水植物种子库密度范围为0—200 ind./m2, 平均为24 ind./m2。根据金湖的水下光照条件和沉水植物种子库分布情况, 结合湖底地形, 建议在冬春季透明度较高的时期降低水位, 进行沉水植物恢复工作。通过水下地形、光照条件和种子库的综合分析, 对金湖的沉水植物恢复区进行了划分, 结果显示东湖的东南部、东湖的西岸、刘家湖的西部和东岸作为沉水植物恢复区较为合适。该研究有望为湖泊沉水植物的恢复提供定量化的参考建议, 提高生态修复工程效果和降低管理成本。     

Allelopathic activity of volatile substance from submerged macrophytes on Microcystin aeruginosa

Considerable attention has been paid on the allelopathic potential of aquatic macrophytes against blue-green algae. This study compared inhibitory activity of volatile compounds that were contained in two submerged macrophytes, Ceratophyllum demersum and Vallisneria spiralis, on Microcystin aeruginosa. When the concentration of essential oils was 100 mg/L, the antialgal activities for fresh macrophytes were similar between C. demersum and V. spiralis but stronger than those for dry macrophytes. Essential oils from C. demersum in dry macrophytes showed stronger antialgal activity than those from V. spiralis. There exists a positive correlation between the concentration of the essential oils and the inhibitory activity. The essential oils were composed of fatty compounds, terpenoids, phenolic compounds, phthalates, and some unknown compounds. More than 40% of the essential oils from fresh macrophytes were composed of phthalates, whereas approximately 70% of those from dry macrophytes were composed of lipid compounds and terpenoids. However, approximately 20% of the essential oils from fresh macrophytes were composed of unknown compounds, which were unstable and undetectable in dry macrophytes. Therefore, their chemical structures and bioactivities need further study.     

沉水植物光合作用的特点与研究进展

沉水植物属于高等植物,由陆生被子植物演化而来,它们在形态、光合生态生理方面对水下生活环境发生了一系列适应性变化。沉水植物的光合作用受水体中光、温度、pH和无机碳等影响,本文对此进行了综述。水中低CO2扩散率以及细胞外较厚的扩散层阻碍了沉水植物净碳的吸收,因此,沉水植物光合作用速率受到无机碳供应的限制。为获得无机碳,沉水植物在形态结构和生理生化上表现一定的特性,包括薄的叶片层并含有叶绿体以及对HCO3-利用的能力,拟C4型和CAM型光合代谢途径的选择。这些是沉水植物碳浓缩机制的具体体现。     

Food choice in Siganus fuscescens: influence of macrophyte nutrient content and availability

Using multiple‐choice feeding experiments, the selection of six species of macrophytes by the herbivorous rabbitfish Siganus fuscescens was examined. The rabbitfish showed distinct food choice in the laboratory; however, selection of macrophytes by S. fuscescens was not related to their absolute nutrient content (nitrogen, carbon, energy and ash free dry mass). Nutrient assimilation estimates showed that the macrophytes which were most preferred were those that S. fuscescens assimilated best. In S. fuscescens , the macrophytes that were preferred passed through the gut significantly faster than the less preferred species. Gut transit time had a significant effect on the absolute value of a food item in terms of net nutrient gain per unit time. This study showed that food value could be inferred from the absolute nutrient content of the macrophytes. Thus both the ability to assimilate nutrients as well as the absolute nutrient content of macrophytes must be quantified when assessing food value.     

沉水植物茎叶微界面特性研究进展

沉水植物茎叶-水界面是浅水湖泊的重要界面之一,对湖泊生物地球化学循环和水环境质量具有重要影响。富营养化水体中,大量的附着物常富集在沉水植物茎叶表面,形成了特殊的生物-水微界面。对该微界面特性进行深入研究,有助于揭示沉水植物在微环境层面对富营养化水体中物质循环的调控过程和机制。沉水植物茎叶微界面具有促进水体养分转化、改变环境因子及可溶性物质的空间分布,增加物质运输的阻力和距离、降低植物光合作用、调控重金属等生态功能;微界面结构及环境因子受水体营养盐浓度、沉水植物种类及生长阶段等因素的影响。对微界面结构功能的主要研究方法进行了分析总结,并对沉水植物茎叶微界面的研究前沿进行了展望。