Spatial Pattern of Phytoplankton Based on the Morphology‐Based Functional Approach along a River–Floodplain Gradient

Current efforts to yield an appropriate method that would simplify the use of phytoplankton in the ecological evaluation of freshwaters resulted in different approaches based on clustering phytoplankton organisms. In this study, we applied the morphology‐based functional group (MBFG) concept to determine the spatial changes of phytoplankton in the natural riverine floodplain of the alluvial reaches of the Danube River along the horizontal gradient from the river towards the floodplain habitats. The obtained results showed that the magnitude of environmental changes depended on alternations in hydrological variables (hydropattern and water level) that influenced changes in the physical and chemical conditions. High‐intensity flood pulses caused environmental homogenizations and nitrate enrichment of the floodplain habitats. Phytoplankton dynamics were strongly associated with the environmental changes, and using the MBFG approach, two basic hydrological conditions were identified: inundation phase dominated by diatoms (GVI) and isolation phase dominated by filamentous cyanobacteria (GIII). Total diatom biomass decreased along the floodplain gradient with a diminishing of physical constraints, and site‐specific variables became more important in favouring diatom assemblages. The different response of cyanobacterial species to mixing regime was of particular significance for species successions during bloom period. Altogether, classifying very diverse diatoms (centrics and pennates and planktonic and benthic) and cyanobacterial taxa into single groups represents a weakness of the MBFG approach, which might make it impossible to reflect all the ecological differences governed by environmental constraints along river–floodplain gradients. Copyright © 2014 John Wiley & Sons, Ltd.     

Variable niche breadth in benthic diatoms: Implications of ecological specialization and generalization for community structure

The mechanisms that regulate the composition and structure of biological communities remain poorly understood. Diatom communities have traditionally been assumed to be a collection of r-selected, ecologically redundant generalist taxa with distributions constrained largely by dispersal limitation. Here, we challenge this notion by presenting a novel model that uses distributional data to estimate ecological specialization for groups of diatom taxa. We further develop this model to evaluate relationships among ecological specialization, taxonomic richness, and species’ abundance using field data collected from ancient Lake Matano and the broader Malili Lakes system (Sulawesi, Indonesia), as well as Mazinaw Lake (Ontario, Canada). We demonstrated that diatom niche breadth is highly variable both at the assemblage scale and among genera within assemblages. Ecologically-specialized genera exhibited higher taxonomic richness than their generalist counterparts, suggesting that ecological specialization serves to support the sympatric coexistence of multiple species by limiting competitive interactions among congeneric taxa. This assertion is further supported by species’ abundance patterns, which suggested that resources are evenly partitioned among taxa within specialist genera, while less-specialized genera are composed of taxa with either exceptionally high or exceptionally low abundances reflective of their relative success in competitive interactions with one another. Our findings indicate that the often-overlooked complement of rare taxa within diatom assemblages are in fact the entities that respond most sensitively to environmental conditions and are worthy of far greater consideration in environmental assessment and paleolimnological studies.     

河流综合分类及其生态特征分析：应用

河流纪、系、统、类、型、境、群的分析深刻地反映了河流发育地质历史、地理气候条件、河水补给来源、地貌过程、平面形态、生境特征及生物群落等对于特定级别的河流在特定河段上的类型归属及其生态表现。河流综合分类层次结构中各空间尺度环境因子决定了不同的生态效应，其中地理气候和地质地貌是决定淡水生物群落结构组成的主要方面，而河水补给形式和河流平面形态则对个别物种的丰富度和分布具有一定影响。结合已有国内外研究资料，可以按照河流综合分类方法的层次递进分析对各类河流进行合理的划分，同时对其生态特征，如水生生物群落（大型水生植被、藻类、底栖动物和鱼类）组成和分布状况进行系统说明。本文通过对生物群落中部分广适种、气候种和典型地方种的辨识，将生态特征至少在“属”的水平上详细刻画，从而为河流的快速分类和生态修复提供“生物基准”。     

硅藻指数筛选及水质多指标评价体系构建

为了更科学地监测水质,解决水质理化分析的片面性,在柳江的不同水功能区设置实验点,以构建河水质的多指标评价体系。通过不同水功能区及不同水质等级的实验点的对应分析,认定AMIN,GOLI,DDEL,AMSA,ACLI,NAAN,NRHY等是柳江河流清洁种,菱形藻和端泥生藻是柳江耐污种。典型对应分析表明,河流水质参数是影响硅藻群落分布的主要因素,硝酸盐、氯化物、粪大肠杆菌群和总磷等是主要的变量,因子分析的结果亦表明理化参数是主要变量。研究结果表明,理化变量与硅藻指数IPS,IBD,TID,IDG,SLA的关系紧密,依据水功能区长期水质级别并参考水质参数聚类与硅藻种群聚类,划出3组水质不同的类别,IPS,IBD,CEE硅藻指数对该3组水质状况判别效果较好,而硅藻生物多样性指数不适宜评价柳江河流水质。河流水质及生态质量利用IBD和IPS生物指数、VAN类群划分富营养种百分比及理化参数多指标共同评价,可以提高评价结果的可靠度。     

Macroinvertebrate responses along a complex regulated stream environmental gradient

Samples were collected year-round over a one-year period at sites located downstream from a hypolimnetic-release reservoir on the Blue River, Colorado, to examine macroinvertebrate responses along a complex environmental gradient induced by river regulation. Six sampling sites were established in riffles downstream of the dam using approximately a geometric progression starting at 0.25 km. Ordination techniques were used to elucidate macroinvertebrate distributional patterns along the complex environmental gradient. The detrended correspondence analysis (DCA) showed a sequential faunal gradient with the most rapid change occurring within the first 2.0 km below the impoundment. Detrended canonical correspondence analysis (DCCA) was used to relate faunal distributions to downstream changes in environmental variables. Downstream decreases in periphyton standing crop and minimum temperatures, and downstream increases in food resources and maximum temperatures, were identified as the major variables structuring faunal assemblages. The combined use of different gradient analysis techniques proved useful for identifying distinct macroinvertebrate distributional patterns and the environmental variables that may be responsible for these patterns.     

River widening: an approach to restoring riparian habitats and plant species

‘River widenings’ are commonly used in river restoration to allow channel movement within a spatially limited area. Restoration seeks to restore fluvial processes and to re‐establish a more natural riparian community. This study investigates the performance of five river widenings in Switzerland, focusing on the re‐establishment of riparian (semi‐)terrestrial habitats and species, and highlights some factors that seem to influence their performance. The restoration projects are compared with pre‐restoration conditions and near‐natural conditions, which are assumed to represent the worst‐ and best‐case conditions along a gradient of naturalness. Fuzzy ordination of vegetation data and calculation of landscape metrics based on habitat maps revealed marked differences between the degree of naturalness achieved by each individual restoration project. However, in general river widenings were found to increase the in‐stream habitat heterogeneity and enhanced the establishment of pioneer habitats and riparian plants. Analyses of species pools based on a hierarchic list of indicator species and correspondence analysis showed that the ability of river widenings to host typical riparian species and to increase local plant diversity strongly depends on the distance to near‐natural stretches. Species dispersal and establishment might be hampered by decisions taken outside the scope of the restoration project. Therefore we conclude that action on the catchment scale is needed to maximize the benefits of local management. Copyright © 2005 John Wiley & Sons, Ltd.     

Role of discharge and temperature variation in determining invertebrate community structure in a regulated river

This paper quantifies patterns of discharge and temperature variation in the regulated river Lyon and the adjacent, unregulated river Lochay (Scotland) and assesses the importance of these patterns for benthic invertebrate community structure. Invertebrates were sampled at sites in each catchment in autumn, winter and spring during the 2002–2003 hydrological year. Metrics were used to characterize the discharge and temperature regimes in the period immediately preceding invertebrate sample collection. Metric values were then used in a canonical correspondence analysis (CCA) of the invertebrate sample data, in order to assess the significance of individual metrics and the overall importance of flow and temperature variability for community structure. The variance in the invertebrate data explained by this CCA was compared to that from a CCA using a range of environmental data from the sites (stream‐bed algal cover, channel hydraulic, sedimentary and water quality characteristics). This comparison allowed assessment of the relative importance of environmental variables versus hydrologic and thermal regimes. Invertebrate communities in the Lyon were relatively poor and uneven, with Ephemeroptera, Plecoptera and Coleoptera poorly represented. Distinct site and seasonal clusters were evident in the CCA ordination biplots, with Lyon and Lochay sites separated in dimensions represented by geometric mean sediment size, water temperature and algal cover. The cumulative variance values from ordinations using the discharge and temperature metrics were consistently highest, suggesting that differences in invertebrate communities showed a stronger relation to patterns of discharge and temperature variability than to the broader suite of environmental conditions. Although there were marked thermal differences between sites, temperature metrics appeared no more important than discharge metrics in explaining differences in invertebrate community structure. A number of the temperature and discharge metrics appeared similarly important, suggesting that no one aspect of the hydrothermal regime was any more important than others in helping to understand differences in invertebrate community between the study sites. Copyright © 2007 John Wiley & Sons, Ltd.     

The use of coleoptera (arthropoda:insecta) for floodplain characterization on the River Trent,U.K.

Following a long history of floodplain degradation, directly or indirectly as a result of river regulation, international attention is turning to the restoration of these ecologically important ecotones. One immediate problem is to assess the ecological value of different floodplain habitats. With reference to two floodplain sectors—one non-regulated and one regulated—on the River Trent, U.K., this paper characterizes the dominant floodplain units using two families of beetles (Coleoptera: Carabidae and Staphylinidae). Five dominant habitat units, riparian, wetland, woodland, pasture, and arable, are clearly differentiated by both families using ordination analyses. Although the faunal assemblages of specific units within the two sectors have many similarities, the units within the regulated sector are more clearly differentiated, having larger assemblages of ‘describer’ species. It is suggested that the enhanced environmental gradients between units within this sector may be responsible for stronger faunal contrasts.     

Effects of habitat restoration on the macroinvertebrate fauna in a foreland along the river waal,the main distributary in the Rhine delta

River engineering in the Rhine delta and water pollution have been major threats for the ecological functioning of the river in The Netherlands. To mitigate effects of river engineering, secondary channel construction in the forelands along the existing distributaries is considered to be an important measure for river restoration. These areas are the remnants of the former Rhine floodplain and the only area where habitat restoration is possible due to the river functions assigned. Secondary channel construction in the area called ‘Gamerensche Waarden’ was taken as an example to show effects of habitat restoration on the macroinvertebrate fauna. Totally 322 macroinvertebrate taxa were found during the monitoring period. During the first 3 years species richness in the area increased rapidly due to colonization processes in the channels following habitat development. After that period total number of taxa found in the channels stabilized at around 170. A clear positive relationship was demonstrated between habitat quality and species richness. Furthermore, the density of exotic species in the secondary channels was less than in the groyne fields of the main channel. The relatively low number of taxa in polluted habitats could be explained by the presence of the PCB 28 congener. Copyright © 2007 John Wiley & Sons, Ltd.     

A Community‐Level,Mesoscale Analysis of Fish Assemblage Structure in Shoreline Habitats of a Large River Using Multivariate Regression Trees

The mesoscale (10⁰–10² m) of river habitats has been identified as the scale that simultaneously offers insights into ecological structure and falls within the practical bounds of river management. Mesoscale habitat (mesohabitat) classifications for relatively large rivers, however, are underdeveloped compared with those produced for smaller streams. Approaches to habitat modelling have traditionally focused on individual species or proceeded on a species‐by‐species basis. This is particularly problematic in larger rivers where the effects of biological interactions are more complex and intense. Community‐level approaches can rapidly model many species simultaneously, thereby integrating the effects of biological interactions while providing information on the relative importance of environmental variables in structuring the community. One such community‐level approach, multivariate regression trees, was applied in order to determine the relative influences of abiotic factors on fish assemblages within shoreline mesohabitats of San Pedro River, Chile, and to define reference communities prior to the planned construction of a hydroelectric power plant. Flow depth, bank materials and the availability of riparian and instream cover, including woody debris, were the main variables driving differences between the assemblages. Species strongly indicative of distinctive mesohabitat types included the endemic Galaxias platei. Among other outcomes, the results provide information on the impact of non‐native salmonids on river‐dwelling Galaxias platei, suggesting a degree of habitat segregation between these taxa based on flow depth. The results support the use of the mesohabitat concept in large, relatively pristine river systems, and they represent a basis for assessing the impact of any future hydroelectric power plant construction and operation. By combing community classifications with simple sets of environmental rules, the multivariate regression trees produced can be used to predict the community structure of any mesohabitat along the reach. Copyright © 2015 John Wiley & Sons, Ltd.     

河流综合分类及其生态特征分析Ⅱ：应用

基于作者提出的河流纪、系、统、类、型、境、群的综合分类方法,在该体系的层次结构中,各空间尺度的环境因子共同决定了河流生态特征,其中地理气候和地貌条件是决定淡水生物群落结构组成的主要方面,而河水补给形式和河流平面形态则对个别物种的丰富度和分布具有一定影响。结合已有国内外研究资料,可以按照河流综合分类方法的层次递进分析对各类河流进行合理的划分,同时对不同类型河流特征河段的生境条件及其水生生物群落（如大型水生植物、浮游藻类、底栖动物和鱼类）组成和分布状况进行系统说明。本文通过对生物群落中部分广适种、气候种和典型地方种的辨识,将河流生态特征多数在“属”的水平上详细刻画,从而为河流生境的快速识别、分类和生态修复提供“生物基准”。     

Environmental Factors Influencing Macrophytes Assemblages in a Middle‐Sized Mediterranean Stream

The occurrence of aquatic plants was analysed in a medium‐sized river in Greece. There were three objectives. The first was to examine the macrophyte assemblage structure along the river. The identification and hierarchical structure of aquatic plant assemblages were analyzed using Bray–Curtis analysis. Taxa primarily responsible for the differences among the assemblages were identified using similarity percentage analysis. The second objective was to investigate whether habitat features have greater impact on aquatic plant assemblages than chemical parameters. Partial canonical correspondence analysis was used for partitioning the total variation of the biological response. The third objective was to further explore the relationships between hydrophytes (water‐supported plants) richness and water quality using linear regression model. The results showed that from the 86 macrophyte taxa recorded, the 25 were found to be primarily responsible for the differences among the macrophytic assemblages. Both geomorphological and physicochemical variables proved to be significant in the Monte Carlo permutation test. The 14 out of 19 geomorphological variables were statistically significant (p<0.004) and included in the final canonical correspondence analysis model. From physicochemical variables, temperature, conductivity and water velocity were significant predictors of species distribution. Total macrophyte variation was divided into portions: (i) explained exclusively by geomorphological variables (34%); (ii) explained exclusively by physicochemical variables (3%); (iii) explained by both variables (52%); and (iv) unexplained (4%). Partitioning clearly revealed that macrophyte assemblage structure was strongly associated with geomorphological features. Τhe results indicated that hardness, DO and chl‐a play a more prominent role in hydrophyte species richness at community level. Copyright © 2015 John Wiley & Sons, Ltd.     

Responses of Chironomid larvae (insecta,Diptera) to ecological quality in Mediterranean river mesohabitats (South Italy)

Chironomid larvae and pupae were studied in selected Mediterranean rivers with the aim of identifying pool and riffle taxa assemblages and of analysing their response to ecological quality gradients. Macroinvertebrate samples were collected in six Italian rivers along a pool‐riffle sequence in three seasons following a multihabitat sampling technique. Chironomids were identified as genus/species, other macroinvertebrates as family/genus. The main physico‐chemical, hydromorphological and geographical data were collected. Samples were ascribed to five quality classes according to the STAR_ICM index. Based on Chironomid taxa, principal component analysis (PCA) axis 1 represented an organic pollution gradient, axis 2 represented seasonality. Pool and riffle samples were significantly different according to taxa assemblages. Similar results were obtained with PCA based on the whole macrobenthic community. Indicator value (IndVal) analysis facilitated the detection of the Chironomid indicators of high/good quality pools (e.g. Conchapelopia pallidula, Rheopelopia ornata, Epoicocladius ephemerae) and riffles (Tvetenia calvescens, Eukiefferiella gracei). The Berger–Parker dominance index based on Chironomid assemblages in pools was correlated to PCA axis 1 and performed well in discriminating between quality classes. In riffles, no correlations to PCA axes were detected and a wide overlap between quality classes was present. Thus, assessment in the analysed river type may focus on pool mesohabitat as this seems to represent best the ecological gradient of sites. Copyright © 2009 John Wiley & Sons, Ltd.     

Combined effects of environmental factors and regulation on macrophyte vegetation along three rivers in western France

The longitudinal changes of richness and composition of aquatic plants have been studied from headwaters to the fifth stream order in three rivers in western Brittany (France), the Orne, Sélune and Rance. All rivers are regulated by dams along their lower reaches. The total macrophyte richness differed between the rivers (61 to 150 taxa); it was lowest in the Sélune, which flows over a granite substratum throughout its basin. Absolute richness per site varied greatly between rivers, and between groups of sites either upstream or downstream of the dams, though consistently higher values were observed downstream. In contrast, the relative richness at the river basin scale was similar for the group of upstream (average 20 taxa) and downstream sites (average 28) of all rivers. At the site level, richness increased along all there rivers. Several sites below the dams had the highest richness per site, with more than 40 taxa. A shifting evolution of the macrophyte richness was revealed along the river axis, related to habitat heterogeneity and geological changes. Of the 27 abiotic variables initially considered for canonical correspondence analysis, only five to six per river were retained by a forward selection procedure. The eigenvalues of the first two canonical axes explained 16.1 to 22.4% of the total biological variability and 53.9 to 67.7% of the species–environment relationships. The macrophyte distribution was mainly determined by the stream hierarchy, expressed by the distance to source and slope, and showed also the influence of regulation, i.e. the position of the site in relation to the dam. Other physical variables significantly contributed to plant distribution, namely particular habitat types, depth and geological substratum. Nutrient enrichment and organic pollution influences were the main secondary gradients for the Orne and Rance rivers. Copyright © 2003 John Wiley & Sons, Ltd.     

白洋淀底栖动物群落影响因子研究

基于2016年春、夏、秋3季的调查采样,采用典范对应分析(canonical correspondence analysis,CCA)研究底栖动物群落结构和分布对水环境因子和底泥环境因子的响应,识别影响底栖动物群落分布的关键环境因子。CCA结果显示,水环境因子中透明度、叶绿素a、水深、水温、溶解氧、氨氮、硝氮和氧化还原电位是影响底栖动物分布的主要因子;底泥环境因子中底质中值粒径、沉水植物生物量和氨氮含量是影响底栖群落分布的主要因子。优势物种摇蚊科和颤蚓科对高污染物浓度环境适应性更好。水体中氮、磷对底栖动物影响显著,而底泥中氮、磷的影响较小,可以通过氮磷的吸附转移降低水体污染对底栖动物的胁迫。     

1998-2001年长江口近海鱼类群聚结构及其与环境因子的关系

根据1998-2001年长江口近海4个航次鱼类拖网调查数据,运用群落生态学分类和排序方法,分析了长江口近海鱼类群聚结构特征及其与环境因子的关系。筛选后的64个站次的48种长江口近海鱼类分属10目28科,鲈形目种类最多,灯笼鱼目,鲈形目和鲱形目鱼类丰度共占总丰度的 99.81% 。龙头鱼、七星底灯鱼和黄鲫为秋季优势种,银鲳和皮氏叫姑鱼为春季优势种。相同季节年度间的鱼类群聚差异不显著,春季(5月)和秋季(11月)鱼类群聚有明显的季节分化。CCA分析显示：1998-2001年长江口近海鱼类群聚的主要影响因素是水深、底层温度、底层溶解氧、表层总磷和pH值。     

生态需水及其计算方法探讨

在我国经济发展过程中,水资源的不合理配置引发了一系列生态环境问题,研究生态需水对保护各区域的生态环境系统有着重要意义。笔者从生态需水的概念出发,将生态需水量化过程划分为河道内和河道外两部分,并介绍了相应的计算方法。     

Predicting phytoplankton composition in the River Thames,England

Phytoplankton were sampled fortnightly in summer and monthly in winter for 33 months to determine temporal and spatial variations in taxonomic structure and relate these to the physical and chemical environment. Using canonical correspondence analysis, environmental variables selected by stepwise regression were found to be correlated with the major variable(s) determining phytoplankton composition. An improved proportion of explained variance was achieved by classifying data into three seasonal subsets. The highest percentage of explained variance in phytoplankton composition was achieved for the months March to May (36·5%), the lowest variance explained was for the period June to September (28·6%). Within each season, general linear modelling was used to predict taxa responses to variations in particular environmental variables. Taxa responses to discharge are presented as examples for determining river management policies. The rationale of conceptual models and the empirical models used for this study are discussed. © 1997 John Wiley & Sons, Ltd.