Comparative analysis of bacterioplankton assemblages from maritime Antarctic freshwater lakes with contrasting trophic status

The bacterioplankton assemblages of eight maritime Antarctic lakes with a wide range of trophic status and geographic span (six lakes from Hope Bay, Antarctic Peninsula and two from Potter Peninsula, King George Island) were described using denaturing gradient gel electrophoresis and band sequencing during two consecutive austral summers (2003–2004). Analyses of the gels identified a total of 230 bands spread across 57 different positions. Among those bands, 14 were shared between lakes from Hope Bay and Potter Peninsula, 17 were observed only in particular lakes, and 17 were registered both years in the same lake. We successfully reamplified and sequenced 43 bands located in 36 different positions belonging to Bacteroidetes, Actinobacteria, Betaproteobacteria and Cyanobacteria. The closest matches for 63% of the sequenced bands were from Antarctic or from other cold environment clones and sequences already in the databases, suggesting the widespread dominance of microbial communities adapted to cold habitats. The results of the multivariate analyses (Cluster Analysis and CCA) indicated that the nutrient status of the lake influences the bacterioplankton assemblages. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Determination of the trophic state by qualitative and quantitative phytoplankton analysis in two gravel pit lakes

The phytoplankton of two gravel pits with comparable nutrient concentrations but different chlorophyll-a concentrations and phytoplankton biovolume was investigated qualitatively and quantitatively over a period of two years. This study deals with the phytoplankton-rich ‘Rotter See’ and the phytoplankton-poor ‘Paulsmaar’, both South of Cologne. The trophic state of both lakes was determined comparatively according to Ryding &; Rast (1989) and the categories used by Brettum (1989). The results were compared with each other. The trophic lake index according to Hörnström (1981) was modified slightly and subsequently determined for both lakes. A combination of qualitative and quantitative phytoplankton analysis made a proposal of a rehabilitation for the Rotter See possible.     

Rotifer occurrence in relation to age,depth and trophic state of quarry lakes

An effect of age of quarry lakes on rotifer abundance and species composition has been evaluated. Rotifers occurred in all lakes under study. They were even found in the youngest (2 years of age) one, Rogonica 4, but both rotifer density and species richness were low there. Rotifer communities of much higher density and species diversity were noted in lakes only 4–6 years older. Lakes of over 30 years of age were strongly differentiated in rotifer numbers and species structure. In general, age of quarry lakes has an impact on rotifer communities only at the very beginning of the process of colonization. Several years later other factors become more important, e.g., depth or trophic state of the lakes.     

2005年夏季长江口水域浮游植物群集特征及其与环境因子的关系

根据2005年9月8—15日在长江口及其邻近水域(30.5°32.5°N,121.0°123.5°E)进行的多学科外业航次调查所获资料,对调查区浮游植物的群集特征及其与环境因子之间的关系进行了研究。结果表明:鉴定浮游植物98种(含变种和变型),硅藻是浮游植物中的主要类群;浮游植物生态类型多为温带近岸种,少数为暖水种和大洋种;优势种主要为多尼骨条藻、尖刺伪菱形藻、柔弱几内亚藻、翼鼻状藻细长变型和柔弱伪菱形藻;细胞丰度平均为256.4个·mL-1,高值出现在调查区的中部偏南及东北部海域;Margalef物种丰富度指数、Shannon-Wiener物种多样性指数、Pielou'均匀度指数的分布显示:调查区东南部海域浮游植物多样性程度较高,物种均一性较好。物种与环境的典范对应分析显示:甲藻与环境因子中溶解氧的关系较为密切;多尼骨条藻与海水中硅酸盐和硝酸盐的关系较为密切,与海水盐度有很大的负相关性;各物种在排序图中的位置反映了其对不同环境资源的生态需求。     

Changes in bacterial and ciliate densities with trophic status in Mediterranean shallow lakes

Ciliate and bacterial densities and their link with eutrophication were studied in fourteen shallow lakes in northwest Spain. Total phosphorus (TP) in these lakes varied between 30 μg l⁻¹ and 925 μg l⁻¹ and chlorophyll a concentration (chla) between 0.5 μg l⁻¹ and 107 μg l⁻¹. Bacterial abundance ranged from 1 × 10⁶ to 14 × 10⁶ cells ml⁻¹, while ciliate abundance ranged from 0.6 cells ml⁻¹ to 229 cells ml⁻¹. Lakes were classified into three trophic types from their TP and chla concentrations. Bacterial abundance was significantly correlated with trophic type, as well as with TP and with chla separately, whereas ciliate abundance was only correlated with chla. No significant relationship could be established between bacterial and ciliate abundance across the trophic gradient. A general pattern was observed in the ratios of bacterial abundance to TP and chla concentrations, of decreasing ratios with increases in the nutrient loading. This pattern was not found for ciliates. The dominant zooplankton group in 13 of the 14 lakes studied was Rotifera, which accounted for a mean of 71% of total zooplankton abundance (41% of zooplankton biomass). The positive correlation between bacteria and ciliates with this group, and the absence of any relationship with Cladocera suggest that top down control by cladocerans was weaker in our lakes than previously shown in northern European shallow lakes. Rotifers could be important predators of bacteria in the high-nutrient lakes of our study. Higher slopes of regressions on bacterial abundance towards the hypertrophic range indicate that top-down control was weaker in our lakes than in northern European shallow lakes.     

拉萨河流域浮游植物群落结构特征及与环境因子的关系

于2017年8月对拉萨河浮游植物群落组成、丰度、功能群以及多样性指数进行调查,利用典范对应分析法(CCA)分析浮游植物物种与水环境因子的关系。结果表明:流域种类组成以硅藻门(60.4%)为主,其次是绿藻门(20.8%),其余种类18.8%;物种平均丰度为3857cells/L,硅藻门94.6%,蓝藻门3.1%,绿藻门2.3%;种类少、丰度低是拉萨河流域浮游植物群落结构的主要特征;研究区优势种以菱形藻为主; MP、D和P是划分出来的15类功能群中的优势功能群,合计占总丰度的93%,剩余12类仅占7%; Margalef指数、Shannon-Wiener指数及Pielou's evenness指数平均值分别为1.41、1.77和0.5,单因素方差分析(ANOVA)表明三类多样性指数在各支流之间、干流与各支流之间无显著差异; CCA排序结果表明:p H、化学需氧量(CODCr)、总氮(TN)、总磷(TP)是影响拉萨河流域浮游植物群落结构的主要环境因子;同时,pH、TN、TP也是影响浮游植物功能群分布格局的主要因子。     

Development of diatom-based salinity models for paleoclimatic research from lakes in British Columbia (Canada)

Diatoms were identified and enumerated from the surface sediments of 65 lakes located on the Cariboo and Chilcotin Plateaux (British Columbia, Canada). These lakes span a large gradient in lakewater ionic concentration (fresh through hypersaline) and composition, as well as other physical/chemical variables. Almost all of the study lakes had higher salinities in the late-summer than in the spring. The lakes with spring salinities >8 g l^–1 showed the largest seasonal increases in salinity. Ionic composition was similar in the spring and late-summer for most lakes. Both ionic concentration (i.e. salinity) and composition were important environmental variables that could account for the different diatom floras in the lakes. Diatom assemblages characteristic of carbonate-dominated and sulfate-dominated waters were identified. Other variables such as water depth and phosphorus concentration were also important.The majority (87%) of diatom taxa had estimated salinity optima < 3 g l^–1 Halophilic diatom taxa had broader tolerances to salinity when compared to the fresh water taxa, however taxa with narrow and broad tolerances could be identified across the salinity gradient. Species diversity was weakly but significantly correlated to lakewater salinity (r ² = 0.18 to 0.3, P < 0.05).Salinity inference models were developed based on the relationship between the diatom assemblages and the spring, late-summer and average salinity. The correlations between the measured and diatominferred salinity, based on the spring (r = 0.95), late-summer (r = 0.94) and average (r = 0.95) salinity data, are high because there was an extremely strong correlation (r = 0.98) between the log transformed spring and late-summer measured salinities. These salinity reconstruction models provide a tool that can be used to infer past climatic changes as part of paleolimnological studies from appropriate closed-basin lakes in British Columbia.     

Using DNA taxonomy to investigate the ecological determinants of plankton diversity: explaining the occurrence of Synchaeta spp. (Rotifera,Monogononta) in mountain lakes

1. The occurrence of unresolved complexes of cryptic species may hinder the identification of the main ecological drivers of biodiversity when different cryptic taxa have different ecological requirements. 2. We assessed factors influencing the occurrence of Synchaeta species (monogonont rotifers) in 17 waterbodies of the Trentino‐South Tyrol region in the Eastern Alps. To do so, we compared the results of using unresolved complexes of cryptic species, as is common practice in limnological studies based on morphological taxonomy, and having resolved cryptic complexes, made possible by DNA taxonomy. 3. To identify cryptic species, we used the generalised mixed Yule coalescent (GMYC) model. We investigated the relationship between the environment and the occurrence of Synchaeta spp. by multivariate ordination using two definitions of the units of diversity, namely (i) unresolved species complexes (morphospecies) and (ii) putative cryptic species (GMYC entities). Our expectation was that resolving complexes of cryptic species could provide more information than using morphospecies. 4. As expected, DNA taxonomy provided greater taxonomic resolution than morphological taxonomy. Further, environmental‐based multivariate ordination on cryptic species explained a significantly higher proportion of variance than that based on morphospecies. Occurrence of GMYC entities was related to total phosphorus (TP), whereas no relationship could be found between morphospecies and the environment. Moreover, different cryptic species within the same morphospecies showed different, and even opposite, preferences for TP. In addition, the wide geographical distribution of haplotypes and cryptic species indicated the absence of barriers to dispersal in Synchaeta.     

钦州湾春、夏季浮游植物群落特征及其与环境因子的关系

为了探究人类活动对钦州湾浮游植物群落的影响,分别于2013年3月和7月进行了两航次综合调查。采用聚类和典型对应分析法,分别对浮游植物群落及其与环境因子的关系进行了研究。结果表明春夏两季浮游植物共有3门45属115种,其中硅藻100种、甲藻14种、蓝藻1种。两季浮游植物生态类群分别以暖温带广布种和暖温带近岸种为主,季节性差异明显。典型对应分析表明,影响浮游植物分布的主要环境因子是悬浮物、pH、盐度和营养盐。受入海径流和外来水团等因子影响,钦州湾浮游植物群落在夏季更易聚为相似性群落,春季则呈斑块化分布。     

Diatom (Bacillariophyceae) assemblages in salt marshes of south‐central Chile: Relations with tidal inundation time and salinity

To reconstruct sea‐level history from changes in tidal environments using diatom assemblages, we need to better understand the relations among brackish diatom assemblages and changing environments along elevational gradients from diverse coastal sites. Our statistical analysis reveals relations between environmental variables and brackish benthic diatom assemblages in the little studied region of south‐central Chile. Along four transects across salt marshes at two sites, we identified 224 diatom taxa in 112 samples. Detrended canonical correspondence analysis showed that tidal exposure time index and salinity were appropriately regressed against the abundance of diatom species using unimodal‐based methods. Our tests of classical and inverse regressions of weighted average and weighted averaging partial least squares (WA‐PLS) showed that WA‐PLS resulted in the highest coefficient of determination and the lowest root‐mean square of the error of prediction. Our regression will be useful in reconstructing environmental variables from fossil diatom assemblages in Chile.     

莱州湾金城海域网采浮游植物年际变化及与环境因子的关系

为了解莱州湾金城海域浮游植物群落年际变化特征,在该海域设置了15个监测站位,于2009年和2010年采用浅水Ⅲ型浮游生物网逐月连续进行24个航次浮游植物调查,同步监测其他环境因子。浮游植物样品经鲁格氏溶液固定后在OLYMPUS BX_(51)显微镜下进行分类、鉴定、计数,共鉴定出浮游植物81种,隶属于硅藻门、甲藻门、黄藻门和金藻门4门25科43属。其中硅藻16科33属67种,占种类数的82.7%;甲藻6科7属11种,占种类数的13.6%;黄藻2科2属2种,占种类数的2.5%;金藻1科1属1种,占种类数的1.2%。2009年和2010年金城海域浮游植物种类组成和比例基本一致,浮游植物丰度年际变化和种类数年际变化均呈现明显的双峰模型,每年2月和9月为高峰期,5月为全年最低值。2009年和2010年细胞丰度均值分别为465×10~4(38.4×10~4—1351×10~4)个/m~3和457×10~4(41.8×10~4—1380×10~4)个/m~3,均低于1982—1983年平均水平。浮游植物群落年际相似性在60%水平聚类分为四个类群,其中Ⅰ类为5月份样品,优势种为夜光藻和洛氏角毛藻;Ⅱ类为11—4月份样品,优势种有中肋骨条藻、旋链角毛藻和夜光藻;Ⅲ类为8、9、10月份样品,优势种为洛氏角毛藻和丹麦细柱藻;Ⅳ类为6、7月份样品,优势种为洛氏角毛藻和尖刺拟菱形藻。浮游植物群落Shannon-Winner多样性指数平均2.715 (1.446—3.807),Margalef丰富度指数平均2.418 (1.545—3.153),Pielou均匀度指数平均0.523 (0.263—0.706)。2009年和2010年多样性指数和均匀度高峰值出现在3月和10月,低值出现在7月和9月;均匀度指数年际变化低值出现在6—9月。浮游植物群落结构主要受水温和盐度环境因素的影响,其中水温与洛氏角毛藻丰度呈极显著正相关(R=0.613,P0.01),与旋链角毛藻、中肋骨条藻和夜光藻丰度呈极显著负相关(R=-0.662,-0.649,-0.649,P0.01);化学需氧量与旋链角毛藻和中肋骨条藻均呈显著负相关(R=-0.589,-0.480,P0.05);盐度与中肋骨条藻呈极显著负相关(R=-0.585,P0.01);其他环境因子与各优势种丰度相关性不明显。     

Diatom assemblages and their relationship to environmental variables in lakes from the boreal forest-tundra ecotone near Yellowknife,Northwest Territories,Canada

The relationship between diatom (Bacillariophyceae) taxa preserved in surface lake sediments and measured limnological and environmental variables in 22 lakes near Yellowknife (N.W.T.) was explored using multivariate statistical methods. The study sites are distributed along a latitudinal gradient that includes a strong vegetational gradient of boreal forests in the south to arctic tundra conditions in the north. Canonical correspondence analysis (CCA) revealed that lakewater concentrations of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) each accounted for independent and statistically significant proportions of variation in the distribution of diatom taxa. Weighted-averaging (WA) models were developed to infer DIC and DOC from the relative abundances of the 76 most common diatom taxa. These models can now be used to infer past DIC and DOC concentrations from diatom assemblages preserved in sediment cores of lakes in the Yellowknife area, which may provide quantitative estimates of changes in lakewater chemistry related to past vegetational shifts at treeline.     

Midge (Chironomidae,Chaoboridae, Ceratopogonidae) assemblages and their relationship with biological and physicochemical variables in shallow,polymictic lakes

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Relative importance of nutrients and mortality factors on prokaryotic community composition in two lakes of different trophic status: microcosm experiments

The effect of nutrient resources (N and P enrichment) and of different grazing communities on the prokaryotic community composition (PCC) was investigated in two freshwater ecosystems: Sep reservoir (oligomesotrophic) and lake Aydat (eutrophic). An experimental approach using microcosms was chosen, that allowed control of both predation levels, by size fractionation of predators, and resources, by nutrient amendments. Changes in PCC were monitored by fluorescent in situ hybridization (FISH) and terminal-restriction fragment length polymorphism (T-RFLP). The main mortality agents were (i) heterotrophic nanoflagellates and virus-like particles in Aydat and (ii) cladocerans in Sep. All the nutritional elements assayed (N-NO3, P-PO4 and N-NH4) together with prokaryotic production (PP) always accounted for a significant part of the variations in PCC. Overall, prokaryotic diversity was mainly explained by resources in Sep, by a comparable contribution of resources and mortality factors in lake Aydat and, to a lesser extent, by the combined action of both.