Nutritional quality of biofilms with respect to light regime in Lake Saint-Pierre (Québec, Canada)

1. In situ experiments were conducted using specialised incubation devices to grow biofilms under varying light regimes and grazing intensities (by excluding fish and large‐sized zooplankton, >2 mm) both within and between two sites in Lake Saint‐Pierre. 2. Biofilms growing under greater in situ UVR and light exposures found in the south water mass were characterised by a greater biomass and nutrient content, but their total fatty acid (FA) contents and ratios of elemental nutrients were not significantly different from the north. There was a relatively greater abundance of chlorophytes and cyanobacteria in the south water mass, along with a greater proportion of low nutritional quality saturated fatty acids (SAFA). Conversely, biofilms growing in the north had a greater relative abundance of diatoms, as well as greater eicosapentaneoic acid (20:5ω3) and docosahexaneoic acid (22:6ω3) concentrations (two FAs implicated in the physiological competency of grazers). 3. The prevailing community structures created differences in terms of nutritional status of the biofilms for benthic grazers and their predators at the two sites. The biofilms from the southern site were characterised by greater food quantity at the expense of quality, while biofilms from the northern site contained less food of a better quality. Despite this, the nutritional regime in the south supported a greater productivity at higher trophic levels. The secondary treatments (light and grazing by fish and macro‐invertebrates) had lesser effects on food quality.     

千岛湖浮游动物的群落结构

研究了贫－中营养型的大型,深水湖泊－－浙江千岛湖浮游动物的群落结构,包括种类组成,种群动态,现存量及群落多样性指数。在1a的研究中,共发现139种浮游动物（27种原生动物,70种轮虫,26种枝角类和16种桡足类）。根据年平均密度,各类浮游动物的优势种分别为褶累枝(Epistylis plicatilie),螺形龟甲轮虫9Keratella cochlearis),透明蚤（Daphnia hyalina)和一种中剑水蚤（Mesocyclops notius)。轮虫和枝角类群落多样性指数随着水体透明度的增大呈下降的趋势;采样站变异下,枝角类群落多样性指数与其种类数和密度呈显著的正相关关系;月份变异下,桡足类群落多样性指数与其密度呈显著的正相关关系。     

The Phototrophic Community Found in Lake Khilganta (an Alkaline Saline Lake Located in the Southeastern Transbaikal Region)

The structure of the phototrophic community found in Lake Khilganta (the Agin-Buryat Autonomous Area), a shallow saline soda lake (depth, 35–45 cm; water mineralization, 45 g/l; alkalinity, 30 mg-equiv/l; pH 9.5) has been studied. The bottom of the lake is covered with a 10- to 15-mm microbial mat, whose basis is formed by the filamentous cyanobacterium Microcoleus chthonoplastes. The mat exhibits pronounced layering and contains a significant amount of minerals. Six zones, which have characteristic colors and consistencies and are composed of intermittent layers, have been identified along the vertical profile. Live phototrophic bacteria have been found in the three upper zones. The bulk of the cyanobacteria is concentrated in the upper zone. In the lower zones, the development of purple bacteria has been observed. The diurnal dynamics of the vertical distribution of phototrophic microorganisms, which results from variations in the physicochemical environmental parameters, is described. Ectothiorhodospira sp. are dominant among the anoxyphotobacteria present. Their number, determined according to the inoculation method, is 10⁶–10⁷ cells/ml. The purple bacteria of the genera Allochromatium, Thiocapsa, and Rhodovulum are also present. Experiments with isolated pure cultures have shown that the anoxygenic photosynthetic bacteria of Lake Khilganta are halotolerant and alkalitolerant or alkaliphilic. In liquid enrichment cultures, at pH 9.5, the ratio of anoxyphotobacteria species is close to that observed in the lake. When the pH is increased to 10.4, it is Ectothiorhodospira, which is the most adapted to life under increased mineralization and alkalinity, that predominantly develops. Photosynthetic activity has been observed in the three upper mat zones and constitutes, on average, 1.5 g C/(m²h); the share of anoxygenic photosynthesis accounts for 75–95% of the total productivity. The main role in sulfide oxidation belongs to the phototrophic anoxyphotobacteria and cyanobacteria. In terms of the physicochemical conditions and structure of the phototrophic community, Lake Khilganta is similar to shallow saline water bodies of marine origin. The main differences consist in the increased alkalinity and in the consequent prevalence of alkaliphilic and alkalitolerant microorganisms and in the absence of representatives of the neutrophilic group of green sulfur bacteria.__________Translated from Mikrobiologiya, Vol. 74, No. 3, 2005, pp. 410–419.Original Russian Text Copyright © 2005 by Kompantseva, Sorokin, Gorlenko, Namsaraev.     

运城盐湖细菌群落结构及生态多样性分析

运城盐湖作为一个人类活动深入参与的高盐环境,其中的细菌群落结构及生态多样性既有盐湖环境的共性,又有自身的特殊性。【目的】运城盐湖湖水颜色丰富,蕴含着大量嗜盐及耐盐微生物资源。为了深入探究运城盐湖细菌资源分布规律,对不同水域中细菌多样性和群落结构进行研究,探讨运城盐湖不同水域中细菌群落结构的变化规律。【方法】基于16S rRNA基因的扩增子高通量测序,对运城盐湖不同水域的细菌群落结构进行分析,同时对微生物的潜在代谢功能进行预测。【结果】运城盐湖不同水域中的优势细菌类群有所差异,在盐湖中部,假单胞菌门(Pseudomonadota)、放线菌门(Actinobacteriota)和拟杆菌门(Bacteroidota)是优势类群;而在运城盐湖东部,芽孢杆菌门(Bacillota)则是主要类群;在运城盐湖西部,髌骨菌门(Patescibacteria)类群较为丰富。对运城盐湖不同区域的细菌多样性进行分析,数据显示盐湖中部浅黄色湖水中微生物多样性显著高于盐湖东部和西部区域,但盐湖中部红色湖水区域的微生物多样性较低。另外,在盐湖中部,湖水颜色不同的区域细菌物种分布也具有较大的差异。对运城盐湖细菌代谢功能进行预测分析发现,在盐湖不同区域的微生物参与的代谢通路活性各不相同,表现出较强的区域分布性,盐湖东部和西部的微生物代谢比盐湖中部更具有活性。【结论】运城盐湖微生物多样性丰富,不同水域的细菌多样性具有显著差异,盐湖不同水域的环境对细菌群落结构具有一定影响。本研究为运城盐湖细菌资源多样性的保育及开发利用提供了重要的理论基础。     

青海湖与中国内陆盐湖古菌群落组成的比较

【目的】本研究旨在全面揭示中国最大的内陆咸水湖——青海湖的古菌群落结构,并对青海湖与盐湖的古菌多样性及群落结构进行比较。【方法】随机选取了青海省的茶卡盐湖、陕西省的花马池盐湖和苟池盐湖以及山西省的运城盐湖作为盐湖组。青海湖与盐湖组每个湖泊各采取5个样品,采用针对16S rRNA基因的高通量测序技术分析5个湖泊中的古菌群落组成。【结果】研究发现,青海湖的优势菌群为DHVEG-6_norank、Methanomicrobia_unclassified、Methanobacterium(甲烷细菌属)、Methanolobus(甲烷叶菌属)、Candidatus_Methanomethylophilus、Miscellaneous_Euryarchaeotic_Group(MEG)_norank、AMOS1A-4113-D04_norank、Methanosarcina(甲烷八叠球菌属)、Miscellaneous_Crenarchaeotic_Group_norank。其中,DHVEG-6_norank(70.46%)占绝对优势,但该类群在盐湖中含量极少。4个盐湖的共有优势属为Halonotius、Halorubrum(盐红菌属)、Natronomonas(嗜盐碱单孢菌属)、Halobellus和Haloarcula(盐盒菌属)。对于青海湖与盐湖之间的古菌群落多样性,影响最大的因素为湖水的矿化度,矿化度与5个湖泊的古菌多样性呈负相关,矿化度较低的青海湖群落组成与其他4个盐湖差异显著,无共同优势菌;其次为pH,pH与湖泊中古菌群落多样性呈微弱正相关,小幅度影响到某些菌属的丰度;而本文研究范围内的海拔与其群落结构及多样性没有明显相关性。【结论】青海湖与其他4个盐湖之间的群落结构及多样性有显著差异,矿化度对古菌群落多样性具有显著影响。另,本次测序发现5个湖泊中均有大量未分类的古菌,应为潜在的新种。     

上海崇明岛明珠湖轮虫群落结构

根据2008年1-12月上海市崇明岛明珠湖的综合调查资料,分析了明珠湖轮虫的数量分布、群落特征、种类组成、优势种及物种多样性.结果表明：本次调查共鉴定出轮虫27种,隶属于8科11属,优势种包括刺簇多肢轮虫、暗小异尾轮虫、萼花臂尾轮虫、未定名的旋轮属1种和剪形臂尾轮虫;轮虫生物密度的年均值为（1505.42±1304.63） ind·L^-1,生物量年均值为（2.012±2.146） mg·L^-1;明珠湖轮虫的Shannon-Wiener多样性指数、丰富度指数和均匀度指数均较低,优势种的优势度指数较大,反映出明珠湖轮虫群落结构不稳定;其富营养种数/贫营养种数（E/O）的比值为1.61±1.46,臂尾轮虫属（B）种数和异尾轮虫属（T）种数的比值（Q_B/T）为1.23±0.84.影响明珠湖轮虫生态特征分布的主要因子是水温;目前明珠湖水质呈轻度富营养化.     

新疆两盐湖可培养极端嗜盐菌组成及功能多样性研究

【目的】通过分析不同成盐类型盐湖中的极端嗜盐菌群落组成差异,探究可培养极端嗜盐菌的功能特性。【方法】采集新疆硫酸盐型盐湖七角井和碳酸盐型盐湖南湖的土壤样品,通过平板稀释涂布法分离极端嗜盐菌,经过形态学观察、特征分析获取代表菌株,通过耐盐性测定和16S rRNA基因序列测序等对代表菌株进行鉴定,并对极端嗜盐菌的蛋白酶、淀粉酶、纤维素酶和酯酶活性进行筛选,同时检测苯酚降解能力。【结果】本研究共获得1 679株极端嗜盐菌,代表菌株45株,隶属于5门14个属,古菌数量(70.58%)明显多于细菌,最优盐浓度生长范围为18.4%–20.0%。在属水平上,盐湖中优势类群为古菌的Haloterrigena属(32.94%)和Natrialba属(26.03%),以及细菌的Aquisalimonas属(9.85%)和Aliifodinibius属(8.10%)。两盐湖中,盐度较低的南湖物种丰富度高于七角井盐湖,古菌物种组成相似,均以Haloterrigena属为主;细菌群落组成有差异,南湖以Aquisalimonas属为主,而七角井以Aliifodinibius属为主。功能筛选表明,盐湖中80%的嗜盐...     

人工滩涂湖泊滴水湖浮游藻类群落特征

于2009年3月—2010年2月逐月对中国最大人工滩涂湖泊——滴水湖的浮游藻类群落特征进行研究。利用CANOCO4.5软件对浮游藻类数据和环境因子数据进行典范对应分析(CCA),以揭示浮游藻类对生态环境的响应。结果表明:全年共检测到浮游藻类186种及变种,隶属于8门92属,其中绿藻门种类最多,其次是蓝藻门和硅藻门;主要优势种为小席藻、微小平裂藻、银灰平裂藻、不定微囊藻、弱细颤藻、啮蚀隐藻、四尾栅藻、扁圆卵形藻;藻类的年均丰度和年均生物量分别为(4552.29±4591.33)×104cells·L-1和8.15±6.63mg·L-1,藻类现存量各月份间差异极显著(P<0.01),但站点间差异不显著;多样性分析显示,藻类物种多样性较好;典范对应分析表明,水温、总氮等是影响滴水湖藻类群落结构的主要因素。     

A comparative study of the zoobenthos of eight land-water interfaces (Lake of Geneva)

The macrozoobenthos of eight types of land-water interfaces of Lake Geneva was sampled three times between October 1988 and July 1989. Three artificial interfaces (concrete walls, cracked walls, embankments) and five natural interfaces (stony shores, stony shores below a riparian forest, reed-belts, clayey banks and sandy shores) were chosen, according to their qualitative or quantitative importance in Swiss lakes.Macroinvertebrate density, diversity, richness and occurence frequency were calculated for each interface. Correspondence analysis was used to show the differences between the interfaces and between the stations.In the artificial interfaces taxonomic richness, diversity and density were low. They were characterized by the most frequent taxa in the interfaces studied and by taxa associated with hard substrate interfaces. The natural interfaces, besides the sandy shore, showed high taxonomic richness, diversity and density values and were characterized by less frequent taxa in the studied interfaces or taxa specific for one type of interface.

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Résumé Entre october 1988 et juillet 1989, trois campagnes de prélèvements de macroinvertébrés ont été effectuées dans huit types d'interfaces eau-terre du lac Léman (Suisse). Trois interfaces artificielles (mur de béton, mur avec anfractuosités, enrochements) et cinq interfaces naturelles (grève caillouteuse, grève caillouteuse sous ripisylve, roselière, talus terreux et grève sablonneuse) ont été choisies en fonction de leur importance qualitative et quantitative dans les lacs suisses.Les différentes interfaces ont été caractérisées àl aide de ladensité, de la richesse faunistique et de la fréquence des taxons. Les différences entre interfaces et entre stations ont été mises en évidence par analyses de correspondance.La richesse faunistique, la diversité et la densité des interfaces artificielles sont faibles. Elles sont caractérisées par des taxons fréquent dans l'ensemble des interfaces prospectées et par quelques taxons fréquents dans les interfaces à substrat dur. Les peuplements des interfaces naturelles, àl'exception des grèves sablonneuses, ont des valeurs de richesse faunistique, de diversité et de densité plus élevées et peuvent être caractérisés par la présence de taxons peu communs dans les interfaces ou de taxons spécifiques à un type d interface.

     

锦鸡儿植物对盐碱地土壤理化性质和细菌群落的影响

锦鸡儿属的多种植物在干旱/半干旱区域水土保持等方面具有显著的作用效果,该研究以柠条锦鸡儿、中间锦鸡儿和小叶锦鸡儿为材料,选择宁夏银北西大滩核心试验站的盐渍化荒地为研究对象,分析了3种锦鸡儿建植1年对盐碱地土壤理化性质及土壤细菌群落的影响,以了解该类植物在盐碱地改良中的作用及生态效应。结果显示:(1)种植锦鸡儿1年能够显著降低盐碱地土壤全盐含量和pH,提高土壤全氮和全磷含量。(2)种植锦鸡儿不影响其非根际土壤细菌群落的α多样性,但小叶锦鸡儿非根际土壤细菌群落的香浓指数最低。(3)不同种锦鸡儿对盐碱地细菌群落结构的影响有所不同,小叶锦鸡儿根际/非根际细菌群落的结构分别与对照土壤以及柠条、中间锦鸡儿根际土壤存在明显差异;在属水平,包括假黄色单胞菌属、新鞘氨醇菌属及根瘤菌属在内的12个优势细菌属的相对丰度在小叶锦鸡儿非根际土壤中显著增加。(4)db-RDA分析表明,盐碱地土壤全盐、全氮及全磷含量分别解释了锦鸡儿非根际细菌群落结构变异信息的23.5%、25.4%和22.2%,3种因子累计共解释48.5%的细菌群落变异(P0.05),但这些因子对锦鸡儿根际细菌群落的变化无显著影响。研究表明,短期种植锦鸡儿属植物对盐碱地土壤理化性质具有一定改良效果,且不影响非根际土壤细菌群落的α多样性,但不同种锦鸡儿对土壤细菌群落结构的影响存在差异。     

An Analysis of the Biotic Community in a Kumaun Himalayan Lake,Nainital (U. P.), India

A comprehensive study of phyto- and zooplankton and macrozoobenthic components in Lake Nainital showed that species richness was high for plankton and low for macrozoobenthos. The algal biomass was dominated by greens (54 %) and blue-greens (31 %), the zooplankton population by copepods (84 %), and the macrozoobenthic community by a Tubifex-Chironomus association constituting≥95 % of the annual number of the macrobenthic invertebrates. Respiration (807.5g C m⁻² year⁻¹) surpassed gross production (630.5 g C m⁻² year⁻¹). The mean annual ratio between phyto- and zooplankton biomass is 3.3 and between phytoplankton and herbivores it is 4.6. If biomass is treated as a measure of crude production, the relationship among the three trophic levels suggests that herbivory is inefficient while carnivory is efficient, because part of the primary production remains unutilized by dominant herbivorous zooplankters, whereas Mesocyclops leuckarti, the sole carnivore, feeds efficiently on rotifers and juveniles of other copepods. The low diversity of different biotic components and the P/R ratio of less than 1 perhaps suggest that the lake is passing through the stage of heterotrophic succession.     

Spatial heterogeneity of macrophytes in Lake Gallocanta (Aragón,NE Spain)

The spatial distribution of macrophytes (Ruppia drepanensis) Tineo and Lamprothamnium papulosum (Wallr.) J. Gr. was studied along transects perpendicular to the shoreline in Lake Gallocanta (Aragón, NE Spain) in 1988 and 1990. In the shallow zone, a gradient from the shoreline to offshore waters was clear: Small R. drepanensis plants were the only colonizers of nearshore waters affected by wave action and desiccation. R. drepanensis and L. papulosum coexisted at intermediate depths in the shallow zone. L. papulosum reached higher biomasses than R. drepanensis in the deepest parts of the shallow zone. In the deepest zone of the lake, stands of the two species did not overlap. Individual plants of R. drepanensis occured patchily within a sparse prairie of L. papulosum.This spatial pattern was observed at different lake levels, suggesting that macrophytes are adapted to fluctuations of environmental conditions. In very shallow water the macrophytes decay as indicated by negative net production and low chlorophyll a/chlorophyll b and plant K⁺ concentration/water K⁺ concentration ratios.     

New alluroidids (Annelida,Clitellata) from Guyana

A total of 30 microbialites at two sites in Lake Clifton, Yalgorup National Park, Western Australia, were sampled by coring to quantify the associated fauna with these organo-sedimentary structures. Twenty five species of aquatic fauna were recorded from the cores, comprising 20 species of metazoan, predominantly Crustacea (including Melita kauerti (Amphipoda), Exosphaeroma cf. serventii (Isopoda); and Cyprideis australiensis(Ostracoda); Polychaeta (Capitella cf. capitata); nematodes; and five species of Foraminifera (Protista). Multivariate analysis of the five numerically most abundant taxa (amphipods, isopods, ostracods, polychaetes, nematodes) separated microbialites by season and submergence. Numbers of all taxa, particularly polychaetes and amphipods, were much higher in spring than in autumn, and in permanently-inundated than in seasonally-inundated microbialites. The exception was higher numbers of juvenile polychaetes in seasonally-inundated microbialites at the northern site in spring. This study showed that modern thrombolitic microbialites can co-exist with a diverse invertebrate fauna and serves as a baseline for future studies of interactions between microbialites and fauna.     

The Structure of a Macroinvertebrate Community in a Northern German Lake Outlet (Lake Belau,Schleswig-Holstein) with Special Emphasis on Abundance,Biomass and Secondary Production

The structure of macroinvertebrate communities was studied at I I sampling sites of the outlet of Lake Belau in the lowlands of northern Germany. To describe the structures of macrobenthic animal communities three different units were examined: abundance, biomass, and secondary production. 112 taxa were collected from the entire stream. The numbers of species ranged from 31 (fine sand) to 70 (submerged macrophytes). For the stream, average macroinvertebrate density was 18.400 ind. M⁻¹. Density was highest at the macrophytes amounting to 35,630 individuals per m², and lowest in the pure sand with only 3,900 ind. M⁻². Average biomass (dry mass) was 194 g DM m⁻² varying from 9.8 (peat) to 381 g DM m⁻² (gravel with mollusk shells near the upstream lake). For the stream, average annual production was 129 g DM m⁻² varying from 15 (peat) to 286 g DM m⁻² (macrophytes). The highest values for each unit were found in stream sections with gravel and submerged macrophytes. Lower values occured in sections that contained peat and sand. Usually, a single structure of the macroinvertebrate community was dominated by less than ten taxa, which varied at each sampling site depending on the units observed.     

毛竹扩张对常绿阔叶林土壤微生物群落的影响

毛竹具有独特的生理生态学特征,会不断地向邻近的生态系统扩张。这一现象会造成生态系统退化、土壤理化性质和微生物群落结构改变等问题,引起了人们的高度关注。然而,目前关于毛竹扩张对微生物群落结构的影响研究甚少。以安吉灵峰寺林场的长期定位试验为平台,在4条毛竹扩张样带上依次设置常绿阔叶林(BLF)、竹-阔混交林(MEF)和毛竹林(PEF)样地,测定不同林型的土壤理化性质以及微生物群落特征。结果表明: 随着毛竹的扩张,土壤pH值显著上升,毛竹林土壤pH值分别比竹-阔混交林和常绿阔叶林高0.37和0.32,而有机碳、铵态氮、硝态氮含量显著降低;除丛枝菌根真菌外,其他主要微生物类群都有下降的趋势,且微生物多样性和丰富度显著降低。毛竹扩张对土壤碳输入及养分的改变是影响地下微生物群落生物量及结构的重要因素,其中土壤有机碳、铵态氮含量是影响土壤微生物群落变化的主要因子。     

四川南充城区鼠形小兽群落结构

2003年9月～2004年8月对南充城区的鼠形小兽群落进行研究,应用聚类分析将其划分为3种群落：C1以微尾鼩（Anourosorex squamipes）＋褐家鼠（Rattus norvegicus）为主的居民区附近的垃圾地带鼠形小兽群落;C2以微尾鼩＋大足鼠（Rattus nitidus）为主的河谷-风景区鼠形小兽群落;C3以微尾鼩＋褐家鼠＋黑线姬鼠（Apodernus agrarius）为主的校园鼠形小兽群落.其群落多样性指数和均匀性指数均以C3最高,C2次之,C1最低,导致其原因可能与生境和食物丰富度有关.     

Deep Subsurface Microbial Biomass and Community Structure in Witwatersrand Basin Mines

The extreme environments of South Africa mines were investigated to determine microbial community structure and biomass in the deep subsurface. These community parameters were determined using phospholipid fatty acid (PLFA) technique. Air, water and rock samples were collected from several levels and shafts in eight different mines. Biomass estimates ranged over nine orders of magnitude. Biofilm samples exhibited the highest biomass with quantities ranging from 10 ³ to 10 ⁷ pmol PLFA g ^?1 . Rock samples had biomass ranging from 10 ³ to 10 ⁶ pmol PLFA g ^?1 . Mine service waters and rock fracture waters had biomass estimates ranging from 10 ⁰ to 10 ⁶ pmol PLFA L ^?1 . Air samples biomass values ranged from 10 ^?2 to 10 ⁰ pmol PLFA L ^?1 . The biomass estimates were similar to those estimates for other deep subsurface sites. Redundancy analysis of the PLFA profiles distinguished between the sample types, where signature lipid biomarkers for aerobic and anaerobic prokaryotes, sulfate-and metal-reducing bacteria were associated with biofilms. Rock samples were enriched in 18:1 ω 9 c , 18:2 ω 6, br17:1s and br18:1s, which are indicative of microeukaryotes and metal- reducing bacteria. Air samples were enriched with 22:0, 17:1, 18:1, and a polyunsaturated fatty acid. Service waters had monounsaturated fatty acids. Fracture waters contained i17:0 and 10Me18:0 which indicated gram-positive and other anaerobic bacteria. When the fracture and service water sample PLFA responses to changes in environmental parameters of temperature, pH, and anion concentrations were analyzed, service waters correlated with higher nitrate and sulfate concentrations and the PLFAs 18:1 ω 7 c and 16:1 ω 7 c . Dreifontein shaft 5 samples correlated with chloride concentrations and terminally branched saturated fatty acids and branched monounsaturated fatty acids. Kloof, Tau Tona, and Merriespruit fracture waters aligned with temperature and pH vectors and 18:0, 20:0 and 22:6 ω 3. The redundancy analysis provided a robust method to understand the PLFA responses to changes in environmental parameters.     

Nearly a decade‐long repeatable seasonal diversity patterns of bacterioplankton communities in the eutrophic Lake Donghu (Wuhan,China)

Uncovering which environmental factors govern community diversity patterns and how ecological processes drive community turnover are key questions related to understand the community assembly. However, the ecological mechanisms regulating long‐term variations of bacterioplankton communities in lake ecosystems remain poorly understood. Here we present nearly a decade‐long study of bacterioplankton communities from the eutrophic Lake Donghu (Wuhan, China) using 16S rRNA gene amplicon sequencing with MiSeq platform. We found strong repeatable seasonal diversity patterns in terms of both common (detected in more than 50% samples) and dominant (relative abundance >1%) bacterial taxa turnover. Moreover, community composition tracked the seasonal temperature gradient, indicating that temperature is a key environmental factor controlling observed diversity patterns. Total phosphorus also contributed significantly to the seasonal shifts in bacterioplankton composition. However, any spatial pattern of bacterioplankton communities across the main lake areas within season was overwhelmed by their temporal variabilities. Phylogenetic analysis further indicated that 75%–82% of community turnover was governed by homogeneous selection due to consistent environmental conditions within seasons, suggesting that the microbial communities in Lake Donghu are mainly controlled by niche‐based processes. Therefore, dominant niches available within seasons might be occupied by similar combinations of bacterial taxa with modest dispersal rates throughout different lake areas.     

南四湖浮游动物群落结构特征及其与环境因子的关系

为探讨南四湖浮游动物多样性特征及其与水质的相关性,于2012年夏季(7月)和冬季(12月)对南四湖浮游动物的群落结构进行了系统研究,结合历史数据,分析了南四湖浮游动物群落的多样性特征和时间变化。共采集到浮游动物163种,其中,轮虫78种,原生动物65种,枝角类17种,桡足类3种。夏季记录浮游动物种类数(141种)高于冬季(105种)。从四个湖区来看,微山湖浮游动物种数最多(102种),其次是南阳湖(95种)和昭阳湖(80种),独山湖(73种)较少。南四湖浮游动物全年平均密度为2 192 ind/L,平均生物量为2.27 mg/L。除原生动物外,其他三类浮游动物夏季的平均密度和生物量都高于冬季。采用丰富度指数、Shannon-Wiener指数和均匀度指数对浮游动物多样性进行了评价,结果均显示,南四湖浮游动物多样性夏季高于冬季。通过回归分析发现,总氮是影响浮游动物密度的主要因素,总氮和水温是影响浮游动物生物量的主要因素,p H和电导率是影响浮游动物多样性的主要因素。     

Community structure of Archaea and Bacteria in a profundal lake sediment Lake Kinneret (Israel)

The microbial community structure of an anoxic profundal lake sediment, i.e., subtropical Lake Kinneret, was analysed with respect to its composition by culture-independent molecular methods including terminal restriction fragment length polymorphism (T-RFLP) analysis, comparative sequence analysis, and quantitative real-time PCR. In particular we were interested in the structure, species composition, and relative abundance of the overall microbial community in the methanogenic sediment layer (0-10 cm depth). Pairwise comparison of archaeal and bacterial 16S rRNA gene T-RFLP profiles obtained from three independent samplings indicated stability of the microbial community. The numbers of Archaea and Bacteria, quantified by real-time PCR, amounted to about 10(8) and 10(10) 16S rRNA gene copies cm(-3) sediment, respectively, suggesting that Archaea may account for only a minor fraction (approximately 1%) of the total prokaryotic community. Hydrogenotrophic Methanomicrobiales and acetoclastic Methanosaeta spp. dominated T-RFLP profiles of the archaeal community. T-RFLP profiles of the bacterial community were dominated by Deltaproteobacteria, sulphate reducers and syntrophs in particular. The second most abundant group was assigned to the Bacteroidetes-Chlorobi-group. Only one bacterial group, which was affiliated with halorespiring bacteria of subphylum II of the Chloroflexi, showed variation in abundance within the sediment samples investigated. Our study gives a comprehensive insight into the structure of the bacterial and archaeal community of a profundal lake sediment, indicating that sulphate reducers, syntrophs, bacteroidetes, halorespirers and methanogens are of particular importance in Lake Kinneret sediment.