Gastropod grazing on a benthic alga leads to liberation of food‐finding infochemicals

Chemical information transfer is a major agent in the regulation of interspecific and intraspecific interactions in natural ecosystems. One important group of such infochemicals both in terrestrial and aquatic ecosystems are so‐called volatile organic compounds (VOCs) that can evoke behavioral or physiological responses like predator avoidance and mate or host location. In previous work, we have demonstrated that freshwater gastropods utilize VOCs released from benthic algae as food finding cues, although the specific nature of the VOC release and perception were not yet clear. Therefore we tested whether gastropod grazing on biofilms leads to algal cell damage and a subsequent liberation of wounding‐associated VOCs. In bioassays we investigated the algal VOC bouquet level which is necessary to elicit a behavioural response of freshwater gastropods. The results of the liberation experiment showed that gastropod grazing leads to VOCs release. We also found that a certain threshold level of volatiles is necessary for snails to recognise the volatile infochemicals and subsequently respond with a directed foraging behaviour towards the odour. Finally, a calculated mass balance model demonstrated that the grazer mediated VOC release produced a signal concentration that is sufficient to be recognized by conspecifics and utilized as foraging infochemicals. The emission of ecologically relevant volatiles through snail grazing with subsequent attraction of other gastropod grazers to algal biofilms indicates an important but so far understudied chemical signaling mechanism of ecological importance.     

藻类挥发性有机化合物研究进展

在水域生态系统中, 藻类释放的挥发性有机化合物(VOCs)种类众多, 主要有萜烯类、醛类、醇类、酯类、酮类、脂肪族烃、芳香族、硫化物和卤化物。这些VOCs通过不同的次生代谢途径形成, 可为多种环境因素所诱导产生。在逆境胁迫下, VOCs具有提高藻细胞抗逆性的作用。当VOCs释放到水体中后, 可为同种藻细胞传递胁迫信息, 使感受细胞做好防御准备。对于异种藻细胞, VOCs通过化感作用抑制其生长, 从而保证VOCs释放者的竞争优势。此外, VOCs还可驱避捕食者, 保护藻细胞免受伤害。未被感受者利用的VOCs经挥发进入大气层后, 会参与水域上空二次有机气溶胶的形成。通过对藻类VOCs的种类、形成途径、诱导释放因素及其生态作用进行综述, 以期对藻类VOCs的研究有所帮助。     

浮游动物诱发藻类群体的形成

从研究蓝藻水华形成机理的需要出发,综述了浮游动物的牧食压力对藻类群体形成的诱发作用。指出诱发藻类群体形成的化合物来自牧食性浮游动物对藻类的有效牧食,是藻类群体形成的重要原因之一,而这些诱发性的化合物并不是有关生物体的组成成分,是种间相互作用的结果。藻类群体的形成方式有源于一个母细胞的分裂和业已存在的单细胞的聚合两种方式,栅藻的诱发性群体可能是来自一个母细胞的分裂,而在其它藻类的诱发性群体形成如铜绿微囊藻则可能是业已存在的单细胞的聚合。由于藻类形成群体后能显著降低浮游动物对其牧食速率,因此,这种诱发性群体形成的现象,可以解释为藻类对变化的牧食压力的一种有效的反牧食防御策略,也是两者协同进化的结果。浮游动物对藻类群体形成的重要作用,在研究模拟蓝藻群体及水华形成值得借鉴应用。作者还提出推测,水华蓝藻的群体形成,可能就是在富营养化条件下藻类快速生长,加上浮游动物的牧食压力共同作用下联合驱动的结果,而这种群体形成很可能在积累到一定程度后,结合特定的气象水文等理化因子,就会聚集于水表“爆发”出肉眼可见的水华。因此,开展浮游动物牧食作用对水华蓝藻早期群体形成诱发效应的研究不仅能加深对水华形成的全面认识,而且对于进一步认识藻类的诱发性反牧食防御适应机制、揭示生态系统中生物之间的复杂关系也具有重要的理论意义。     

An ecological perspective of allelochemical interference in land–water interface communities

Allelochemical interactions among aquatic macrophytes and between macrophytes and attached microbial assemblages (epiphyton) influence a number of ecological processes. The ecological importance of these interactions, however, is poorly understood; we hypothesize that paucity has resulted, in part, from (1) a narrow focus on exploration for herbicidal plant products from aquatic macrophytes, (2) the difficulties in distinguishing resource competition from allelopathic interference, and (3) a predominance of approaching aquatic allelopathy from a terrestrial perspective. Based upon recent thorough investigations of allelopathy among aquatic vascular plants, chemical compounds that influence competitive interactions among littoral organisms are amphiphilic compounds that tend to remain near the producing organism (e.g., polyphenolic compounds and volatile fatty acids). Production of these compounds may be influenced by relative availability of nutrients (particularly phosphorus and nitrogen), inorganic carbon, and light. Macrophyte strategies of clonal reproduction, in an effort to persist in these highly productive and competitive habitats, have contributed to reduced reliance upon sexual reproduction that is correlated with allelopathic autotoxicity among several dominant wetland plant species. Although few studies document the importance of allelochemical interactions in the wetland and littoral zones of aquatic ecosystems, abundant evidence supports the potential for significant effects on competition and community structure; effects of altered nutrient ratios and availability on plant chemical composition; and resultant effects on trophic interactions, particularly suppression of herbivory, competitive attached algae and cyanobacteria, and heterotrophic utilization of organic matter by bacteria and fungi.     

Cyanobacterial Blue Color Formation during Lysis under Natural Conditions

Cyanobacteria produce numerous volatile organic compounds (VOCs), such as β-cyclocitral, geosmin, and 2-methylisoborneol, which show lytic activity against cyanobacteria. Among these compounds, only β-cyclocitral causes a characteristic color change from green to blue (blue color formation) in the culture broth during the lysis process. In August 2008 and September 2010, the lysis of cyanobacteria involving blue color formation was observed at Lake Tsukui in northern Kanagawa Prefecture, Japan. We collected lake water containing the cyanobacteria and investigated the VOCs, such as β-cyclocitral, β-ionone, 1-propanol, 3-methyl-1-butanol, and 2-phenylethanol, as well as the number of cyanobacterial cells and their damage and pH changes. As a result, the following results were confirmed: the detection of several VOCs, including β-cyclocitral and its oxidation product, 2,2,6-trimethylcyclohexene-1-carboxylic acid; the identification of phycocyanin based on its visible spectrum; the lower pH (6.7 and 5.4) of the lysed samples; and characteristic morphological change in the damaged cyanobacterial cells. We also encountered the same phenomenon on 6 September 2013 in Lake Sagami in northern Kanagawa Prefecture and obtained almost the same results, such as blue color formation, decreasing pH, damaged cells, and detection of VOCs, including the oxidation products of β-cyclocitral. β-Cyclocitral derived from Microcystis has lytic activity against Microcystis itself but has stronger inhibitory activity against other cyanobacteria and algae, suggesting that the VOCs play an important role in the ecology of aquatic environments.     

Low-molecular-weight metabolites of aquatic macrophytes growing on the territory of Russia and their role in hydroecosystems

This article deals with the issues of studying low-molecular-weight volatile organic compounds (VOCs) of aquatic macrophytes growing in Russia under different environmental conditions and geographic regions. It is shown that the composition of VOCs and their content depend on the abiotic (geographical location of habitats, hydrological regime, and light conditions) and biotic factors (season and vegetation phase, distribution in different vegetative organs). Special attention has been paid to the functions performed by VOCs in aquatic ecosystems and their possible use for controlling phytoplankton development and algal “blooms” in inland water bodies.     

长白山二道白河森林流域溪流倒木调查研究

溪流倒木是森林生态系统对水生态系统最重要、最直观的输入和干扰之一,也是两系统之间的主要联结,对于溪流生态系统的稳定、水生生物多样性、河槽形态及其变化过程有着重要的作用。重点对长白山北坡溪流倒木现存量进行了调查和研究,在调查的红松阔叶林植被带内４５００ｍ长河道内,共发现溪流倒木４２５株．分属于１７个树种;其中ｌ、ｗ级腐烂占相当大的比重,与林地倒木Ｉ、ｌ级腐烂占忧有所不同,其原因可能与分解环境的不同有关。所有溪流倒木的总材积为７７．９８ｍ＾２,故溪流倒木的现存量为１．７３３ｍ＾３／１００ｍ和１０．８３ｍ＾３／ｈｍ＾２。溪流倒木的树种组成和不同树种的材积与河岸带植被密切相关,但存在差异。研究表明林分形成倒木并进入河流在时间上可能是均匀或随机的,但不同树种间,其形成倒木并进入河流时的树木材积或生长年龄存在较大差异。溪流倒木和林地活立木的个体数量的径级分布基本上为反Ｊ型,而它们材积的径级分布均为典型的Ｊ型。     

Three mammal species distinction through the analysis of scats chemical composition provided by comprehensive two-dimensional gas chromatography

In the last years, new approaches use scats analysis in ecological studies, like gas chromatographic techniques, has been developed. The aim of this study is to use VOCs (volatile organic compounds) released from scats to distinguish three mammal species: the ungulates red and fallow deer and the carnivore Eurasian otter through the application of SPME/GC × GC–ToFMS. This chromatographic technique has never been used in ecological studies. Chromatogram contour plot was effective in distinguishing between the carnivore Eurasian otter and the two ungulates. Additionally, a subset of 21 selected compounds, including hydrocarbons, ketones, aldehydes, alcohols and terpenes, allowed a distinction between Eurasian otter, red deer and fallow deer. Eurasian otter scats were characterized mainly by the presence of aldehydes that may arise from oxidative degradation of unsaturated fatty acids present in fish species, included in their diet. Red deer volatile profile is characterized by terpenes compounds, presumably related with diet, while fallow deer achieved also chemical communication markers: 2-propanone and hexane. The scat volatile profiles provide information that explains their odour and also the type of diet (herbivorous or carnivorous) and intra-specific communication through chemical signals. Being able to distinguish species using the proposed methodology is an asset to wildlife ecology and management studies.     

溪流粗木质残体的生态学研究进展

粗木质残体（CWD）是森林或溪流生态系统中残存的超过一定直径大小的站杆、倒木、枝桠及根系等死木质物的总称,溪流CWD对于溪流生态系统的稳定,水生生物多样性,河槽形态及其变化过程有着重要的作用。对溪流CWD的产生和分类,溪流CWD对于溪流生态系统的稳定,水生生物多样性,河槽形态及其变化过程有着重要的作用。对溪流CWD的产生和分类,溪流CWD贮量,分布和动态,以及溪流CWD的功能和管理分别进行了总结,并指出应尽快在国内开展溪流CWD的研究和管理。     

Photosynthetic Units of Phototrophic Organisms

Photoautotrophic organisms play a key role in the biosphere of the Earth, converting solar energy of the 350-1000 nm range into biochemically available form. In contemporary aquatic and terrestrial ecosystems, the dominating groups are the oxygen evolving cyanobacteria, algae, and higher plants. Anoxygenic phototrophic microorganisms occupy mainly ecological niches with extreme environmental conditions. Despite diverse evolution of all these taxonomic groups, their photosynthetic apparatus has a similar molecular design and identical principles of operation. This review covers recent data about features of the structural and functional organization of pigment-protein complexes of the basic types of photosynthetic units in prokaryotes and eukaryotes. A correspondence between the optical properties of various photosynthetic units and the natural light conditions is discussed.     

Riverine landscapes: taking landscape ecology into the water

1. Landscape ecology deals with the influence of spatial pattern on ecological processes. It considers the ecological consequences of where things are located in space, where they are relative to other things, and how these relationships and their consequences are contingent on the characteristics of the surrounding landscape mosaic at multiple scales in time and space. Traditionally, landscape ecologists have focused their attention on terrestrial ecosystems, and rivers and streams have been considered either as elements of landscape mosaics or as units that are linked to the terrestrial landscape by flows across boundaries or ecotones. Less often, the heterogeneity that exists within a river or stream has been viewed as a `riverscape' in its own right.
2. Landscape ecology can be unified about six central themes: (1) patches differ in quality (2) patch boundaries affect flows, (3) patch context matters, (4) connectivity is critical, (5) organisms are important, and (6) the importance of scale. Although riverine systems differ from terrestrial systems by virtue of the strong physical force of hydrology and the inherent connectivity provided by water flow, all of these themes apply equally to aquatic and terrestrial ecosystems, and to the linkages between the two.
3. Landscape ecology therefore has important insights to offer to the study of riverine ecosystems, but these systems may also provide excellent opportunities for developing and testing landscape ecological theory. The principles and approaches of landscape ecology should be extended to include freshwater systems; it is time to take the `land' out of landscape ecology.     

Pharmaceutical Compounds and Ecosystem Function: An Emerging Research Challenge for Aquatic Ecologists

The number of anthropogenic compounds that occur in aquatic ecosystems today is in the thousands, many at trace concentrations. One group of compounds that has captured the interest of both the scientific community and the general public is pharmaceutical and personal care products (PPCPs), for example, hormones, chemotherapy drugs, antihistamines, stimulants, antimicrobials and various cosmetic additives. Toxicology of some PPCPs is currently understood, but their effect on ecological structure and function of aquatic ecosystems is largely unknown. We review sources and fates of these compounds in aquatic ecosystems and discuss how methods developed to study aquatic ecosystem ecology can contribute to our understanding of the influence of PPCPs on aquatic ecosystems. We argue that aquatic ecology has a well-developed tool kit for measuring the transformation, fate, and transport of solutes using assays and experiments and that these methods could be employed to investigate how PPCPs impact ecological function. We discuss the details of these approaches and conclude that application of existing ecological methods to the study of this issue could substantially improve our understanding of the effect of these compounds in aquatic ecosystems.     

An Ecological Risk Assessment of Ammonia in the Aquatic Environment

Ammonia is released in the environment by many industries and other human activities. The major quantifiable sources of ammonia released to aquatic ecosystems across Canada are municipal wastewater treatment plants, at an estimated total quantity of 62,000 tonnes per year. Given the sources of ammonia releases in the environment and the properties of the substance, terrestrial plants and aquatic organisms are potential risk targets. A tiered assessment approach has been used to determine the ecological risk in the aquatic environment from ammonia released in municipal wastewater effluents. The results obtained for two case studies with the probabilistic risk analysis used in the highest tier support the conclusion that the conditions encountered in these two locations can lead to ammonia concentrations capable of producing an adverse ecological impact.     

淡水生态系统中几种大DNA病毒研究概述

淡水生态系统中的大DNA病毒指存在于淡水系统中、基因组大小接近或超过100 kb 的DNA病毒, 它们通常是感染鱼类、虾类及藻类等水生生物以及两栖类的病原体, 影响水产养殖动物的健康及淡水生态平衡。文章以虹彩病毒科(Iridoviridae) 的沼泽绿牛蛙病毒(Rana grylio virus, RGV)和大鲵蛙病毒(Andrias davidianus ranavirus, ADRV)、鱼蛙疱疹病毒科(Alloherpesviridae)的鲫疱疹病毒(Crucian carp herpesvirus, CaHV)、线头病毒科(Nimaviridae)的克氏原螯虾病毒(Procambarus clarkii nimavirus, PCV)及肌尾病毒科(Myoviridae)的铜绿微囊藻肌尾噬藻体-滇池株(Microcystis aeruginosa myovirus isolated from Lake Dianchi, MaMV-DC)为主线, 对淡水生态系统中几种大DNA病毒代表株的研究现状与文献进行概述, 并提出和讨论淡水水生大DNA病毒研究及水生病毒学科发展愿景, 以期为相关科研人员提供参考。     

Differences in volatile emissions between healthy and gall-induced branches of Haplopappus foliosus (Asteraceae)

Changes in plant secondary metabolism due to insect galls are one of the frontiers in knowledge of plant-insect interactions, especially concerning volatile organic compounds (VOCs). Here we studied the in vivo VOCs released from healthy apical branches of Haplopappus foliosus DC. (Asteraceae) and compared these volatiles to the VOCs obtained from apical bud galls produced in this host plant when attacked by the gall midge Haplopappusmyiia gregaria (Cecidomyiidae). We field-collected VOCs by dynamic headspace and identified them by gas chromatography coupled to mass spectrometry. We found changes in the relative proportions of different classes of VOC in apical branches vs. apical bud galls. H. foliosus VOCs had mainly monoterpene hydrocarbons such as p-cymene, a recognized herbivore deterrent. We also found oxygenated monoterpenes and sesquiterpenes in the H. foliosus volatile mixture. H. foliosus modifies its fragrance composition when parasitized by gall midges, showing an increased proportion of some monoterpene hydrocarbons, e.g. limonene and camphene, while others such as α-thujene, p-cymene and γ-terpinene were down-expressed in apical bud gall VOCs. We discuss these results considering gall signaling and chemical ecology hypotheses, including the potential role of plant defenses as well as gall midge-derived modification for host plant VOCs, and comment on the ecological relevance of our findings.     

Can ecological theory be used to improve water quality?

The role of ecology in environmental management has been more to warn of the dangers of pollution than to propose technical solutions for environmental problems, this being mostly left to chemists and engineers. Only limited aspects of the broad and diverse theory of ecology have been applied in the present bottom-up-control approach to water management (nutrient reduction). Another aspect of ecological theory which has recently become applicable is the top-down-control approach known as biomanipulation (promoting efficient herbivores). Both approaches are likely to be reinforced in the future by further application of ecological theory to water management. Of the multiple possibilities of applying ecological theory to environmental problems, one is the use of our knowledge on chemical communication in aquatic habitats, the phenomena by which prey detect the presence of their predators. I postulate that the phytoplankton standing crop might be reduced by chemical regulation of the physiology and life cycles of algae and cyanobacteria, as well as by chemical regulation of the behaviour and life histories of planktonic herbivores and their predators. At present planktivorous fish seem to be the most logical target for such chemical manipulation. A desirable effect, i.e. a reduction in algal standing crop, could be achieved by scaring fish from the lake pelagial thus releasing predation pressure on the offshore herbivorous zooplankton.     

Highly unsaturated fatty acids in nature: what we know and what we need to learn

The supply and demand of omega‐3 highly unsaturated fatty acids (ω‐3 HUFA) in natural ecosystems may lead to resource limitation in a diverse array of animal taxa. Here, we review why food quality in terms of ω‐3 HUFAs is important, particularly for neural tissue, across a diversity of animal taxa ranging from invertebrate zooplankton to vertebrates (including humans). Our review is focused on ω‐3 HUFAs rather than other unsaturated fatty acids because these compounds are especially important biochemically, but scarce in nature. We discuss the dichotomy between ω‐3 HUFA availability between aquatic primary producers, which are often rich in these compounds, and terrestrial primary producers, which are contain little to none of them. We describe the use of fatty acids as qualitative and quantitative tracers for reconstructing animal diets in natural ecosystems. Next, we discuss both direct and indirect ecological implications of ω‐3 HUFA limitation at the individual, population, food web, and ecosystem scales, which include: changes in behavior, species composition, secondary production rates, trophic transfer efficiency and cross‐ecosystem subsidies. We finish by highlighting future research priorities including a need for more research on ω‐3 HUFAs in terrestrial systems, more research their importance for higher order consumers, and more research on the food web and ecosystem‐scale effects of ω‐3 HUFA limitation. Synthesis Mismatches between the supply of and demand for omega‐3 highly unsaturated fatty acids (ω‐3 HUFA) in natural ecosystems have the potential to result in resource limitation across a diverse array of ecosystems. We combined perspectives from ecology and nutritional science to develop a unified synthesis of ω‐3 HUFA ecology. We reviewed the importance of ω‐3 HUFAs for animals, the striking differences in ω‐3 HUFA availability at the base of terrestrial versus aquatic food webs, and the implications of ω‐3 HUFA limitation for food webs. We finished by highlighting research priorities in the field including more research on ω‐3 HUFAs in terrestrial systems, on higher order consumers, and at the food web and ecosystem‐scales.     

Cyanophage and algal virus

<正>Cyanobacteria and eukaryotic algae are abundant in freshwater and marine environments,and are fundamentally important in global biogeochemical cycles and for primary productivity.Under certain conditions,such as an excess of nutrients due to human activities through fertilizers or sewage,