Re‐introduction of structurally complex wood jams promotes channel and habitat recovery from overwidening: Implications for river conservation

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Are River Styles ecologically meaningful? A test of the ecological significance of a geomorphic river characterization scheme

• 1. Classification is a useful tool for researchers and managers wishing to group functionally similar sites or to identify unique or threatened habitats. A process‐based river classification scheme that successfully integrates physical and biological aspects of lotic form and function would enhance conservation and restoration efforts by allowing more meaningful comparisons among sites, and improving functional understanding of lotic ecosystems.
• 2. The River Styles framework provides a geomorphological river characterization scheme in which assemblages of geomorphic units vary for differing River Styles, presenting differing arrays of aquatic habitat diversity for each style.
• 3. The ecological significance of the River Styles framework is tested by comparing the macroinvertebrate assemblages and habitat characteristics of pool and run geomorphic units for three different River Styles on the north coast of New South Wales, Australia.
• 4. Multivariate ordinations and analysis of similarity (ANOSIM) revealed that macroinvertebrate community structure differed between Bedrock‐Controlled Discontinuous Floodplain rivers and Gorge rivers, and between Bedrock‐Controlled Discontinuous Floodplain and Meandering Gravel Bed rivers, especially in pools. Differences between Gorge and Meandering Gravel Bed rivers were less apparent, largely due to variations within the Meandering Gravel Bed rivers group.
• 5. The variability in macroinvertebrate assemblage structure among geomorphic units was most strongly related to variability in substrate and hydraulic variables. Substrate composition differed significantly among all River Styles and geomorphic units, but other habitat variables showed few consistent differences among River Style groups.
• 6. These results suggest that the ecological similarity of macroinvertebrate communities within River Styles may presently be limited because some important large‐scale drivers of local habitat conditions are not included in River Styles designations. Integrating River Styles classification with other large‐scale variables reflecting stream size, temperature and hydrological regime may produce a process‐based physical classification capable of identifying river reaches with similar ecological structure and function.

Copyright © 2003 John Wiley & Sons, Ltd.     

Habitat use by a freshwater dolphin in the low‐water season

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Hydromorphological rehabilitation improves channel morphology,instream biotopes,and macroinvertebrate communities,and thus enhances the conservation of an urban river

1. Many river rehabilitation projects have been criticized for failing to meet their goals or for being insufficiently monitored. There is, therefore, an urgent need to develop robust approaches for assessing treatment efficacy and thus guide the increasing investment in rehabilitation.
2. Instream biotopes (formerly called ‘functional habitats’ or ‘mesohabitats’ by different authors) and their macroinvertebrate assemblages were used to assess the effectiveness of entire-channel hydromorphological rehabilitation of a 1.8-km stretch of a lowland stream through the town of Market Harborough, Leicestershire, UK.
3. The project successfully enhanced the physical diversity, measured in the rehabilitated reach as the coefficients of variability for channel water depth and width, wet surface area, number of instream biotopes, and biotope diversity.
4. The project also enhanced the biodiversity conservation value, measured as macroinvertebrate total density, total biomass, richness, diversity, Ephemeroptera, Plecoptera, and Trichoptera (EPT) richness, EPT diversity, EPT count%, and EPT biomass%, all of which significantly increased following rehabilitation. Chironomidae count% and biomass% significantly decreased following rehabilitation. Rehabilitation was also successful in significantly increasing macroinvertebrate shredder, scraper, and filter-feeder group density.
5. Changes in the macroinvertebrate community metrics in the rehabilitated reach were related significantly to changes in the percentages of cover of instream biotopes and increases in biotope diversity in the rehabilitated reach.
6. Macroinvertebrate structural and functional metrics can provide quantitative data for assessing reach-level rehabilitation outcomes, if samples are collected in a pre-defined sampling protocol stratified at the instream biotope level.
7. The practical implications of this work are that the design of rehabilitation projects, if based upon the recreation of biotope heterogeneity, will succeed in improving biological value and restoring the area to near naturalness if a suitable upstream source of macroinvertebrates for natural recolonization is available. The study shows that the concept of biotopes has an important role to play in river conservation management.

     

River dolphin distribution in regulated river systems: implications for dry‐season flow regimes in the Gangetic basin

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Mayflies (Ephemeroptera) as indicators of environmental changes in the past five decades: a case study from the Morava and Odra River Basins (Czech Republic)

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Hierarchical spatial patterns and drivers of change in benthic macroinvertebrate communities in an intermittent Mediterranean river

• 1. The imminent damming of the Odelouca River, an intermittent Mediterranean river situated in the south‐west Algarve region of Portugal with valuable stands of riparian vegetation, has called for the compulsory implementation of compensatory measures.
• 2. In order to assess the primary environmental and human factors that drive change in the benthic macroinvertebrate assemblages of the Odelouca, and the spatial scale at which they occur, 30 sites were sampled for benthic macroinvertebrates and extensively surveyed using River Habitat Survey (RHS) in spring 2005.
• 3. A hierarchical cluster analysis of selected physical and RHS variables clearly indicated gradients of habitat quality (instream and riparian corridor) along both main channel and tributaries. Analysis of macroinvertebrate metrics by parametric and non‐parametric ANOVA showed the derived clusters of groups to be biologically distinct.
• 4. From a total of 64 variables, divided into two explanatory variable groups (environmental or pressure) over three spatial scales (habitat, reach and basin), just 20, predominantly environmental, variables were retained for subsequent analyses.
• 5. Partial canonical correspondence analyses of the selected environmental and pressure variables over the defined spatial scales showed that environmental variables contributed most significantly over all of the spatial scales and that pressure variables related to land‐use only contributed significantly at the level of the river basin.
• 6. Variables recorded by RHS contribute successfully to the detection of habitat quality gradients in a Mediterranean river system and the strongest drivers of macroinvertebrate change are primarily, but not exclusively, environmental factors occurring at middle and higher spatial scales.
• 7. Compensatory measures must therefore be implemented across a range of spatial scales, taking into account abiotic and biotic processes characteristic of disturbance‐driven Mediterranean systems that contribute to habitat heterogeneity and quality and confer functional and trophic diversity to the macroinvertebrate assemblages.

Copyright © 2007 John Wiley & Sons, Ltd.     

Modelling functional fish habitat connectivity in rivers: A case study for prioritizing restoration actions targeting brown trout

1. Throughout the world, decreased connectivity of fluvial habitats caused by artificial river channel alterations such as culverts, weirs and dykes is seen as an important threat to the long‐term survival of many aquatic species. In addition to assessing habitat quality and abundance, wildlife managers are becoming increasingly aware of the importance of taking into account habitat connectivity when setting priorities for restoration. In this paper, a new approach of spatial analysis adapted to rivers and streams is proposed for modelling 2D functional habitat connectivity, integrating distance, costs and risk of travelling between habitat patches (e.g. daily use, spawning, refuge) for particular fish species, size classes and life stages.
2. This approach was applied to a case study in which brown trout (Salmo trutta) habitat accessibility was examined and compared under various scenarios of stream restoration in a highly fragmented stream in Ile‐de‐France. Probabilities of reaching spawning habitats were estimated from a trout‐populated area located downstream of the barriers and from potential daily‐use habitat patches across the stream segment.
3. The approach successfully helped prioritize restoration actions by identifying options that yield the greatest increase in accessible spawning habitat areas and connectivity between spawning habitat and daily‐use habitat patches. This case study illustrates the practical use of the approach and the software in the context of river habitat management.

     

Physical habitat,eco‐hydraulics and river design: a review and re‐evaluation of some popular concepts and methods

• 1. Improved linkage between physical characteristics of rivers and biological performance or potential is a recurrent theme in contemporary river survey, management and design. This paper examines the degree to which flow biotopes and functional habitats may be differentiated with respect to physical habitat delimiters, i.e. flow depth, velocity and Froude number.
• 2. Re‐examination of published data demonstrates only very broad associations between biotopes, functional habitats and ‘low’, ‘medium’ and ‘high’ bands in the chosen physical habitat delimiter. The associations are also not consistent between different delimiters.
• 3. Re‐analysis is complicated by considerations of research design and methodology. Further studies are required with greater control on the circumstances of observation (particularly flow stage and seasonality), which explicitly control for variance within and between different river cases, and which adopt more consistent terminology.
• 4. Field data for a single river reach at low and high flows indicate that use of the Froude number, in particular, requires careful interpretation. Very different velocity and depth combinations can exhibit similar Froude numbers. This may obscure important contrasts, such as those between channel margin and channel centreline environments.
• 5. Field data also reveal that the flow characteristics of even basic (riffle or pool) units of channel morphology exhibit strong stage‐dependence. There are also significant variations when channel margins are isolated from the definitions of the bedforms or analysis of the data. Current practice which seeks to simplify field survey to channel cross‐section transects is therefore likely to be misleading.
• 6. Given these difficulties, attempts to link biotopes with ecological response appear premature. Further research might, however, be directed to identifying possible associations between combinations of flow types and bedforms or functional habitats. In this sense, the biotope concept may be more profitably employed as one of several surrogate measures for potential biodiversity.

Copyright © 2006 John Wiley & Sons, Ltd.     

Linking form and function: towards an eco‐hydromorphic approach to sustainable river restoration

• 1. River restoration is now widely undertaken and may be considered an increasingly important aspect of river management. Recent developments in European legislation (Habitats Directive and the Water Framework Directive) should give further impetus to river restoration across EU member states, as this legislation places greater emphasis on the processes that support river ecology.
• 2. Traditional river restoration approaches have been reach‐focused and opportunistic, capitalizing on flood defence works and the cooperation of sympathetic landowners.
• 3. Furthermore, many schemes have been species‐ or habitat‐driven and, thus, have sought to recreate channel forms believed to be favoured by particular species or associated with particular habitats. Such approaches have not always given due attention to the underlying geomorphological processes that create channel form and, consequently, the schemes have not been self‐sustaining, requiring continued management input.
• 4. Consistent with the ethos of the Water Framework Directive, an eco‐hydromorphic approach to river restoration is proposed here. This approach views spatial and temporal heterogeneity as fundamental characteristics of fluvial systems and advocates recreating a framework within which natural processes, such as sediment transport and nutrient dynamics, can occur.
• 5. Mesoscale habitat approaches are considered as one possible way to plan and achieve this framework, providing the potential to link the wide range of spatial and temporal scales that characterize river systems.
• 6. It is argued that river restoration will only be sustainable if it is undertaken within a process‐driven and strategic framework with inputs from a wide range of specialists. Such an approach needs to be reviewed constantly in light of appraisal and monitoring of previous river restoration schemes.

Copyright © 2003 John Wiley & Sons, Ltd.     

Distribution and environmental requirements of stream habitat with Ranunculion fluitantis and Callitricho‐Batrachion vegetation in lower Belgium (Flanders)

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Shining a light on the loss of rheophilic fish habitat in lowland rivers as a forgotten consequence of barriers,and its implications for management

1. The majority of rivers around Europe have been modified in one way or another, and no longer have an original, continuous flow from source to outlet. The presence of weirs and dams has altered habitats, thus affecting the wildlife that lives within them. This is especially true for migrating rheophilic fish species, which, in addition to safe passage, depend on gradient and fast‐flowing waters for reproductive success and early development.
2. Thus far, research has focused on investigating the impacts of weirs and dams on fish passage, with less attention paid to the loss of habitat entrained by such infrastructure. The loss of rheophilic habitat is particularly important in lowland streams, where gradient is limited, and dams and weirs can be constructed with less effort.
3. Denmark is considered a typical lowland country, where the landscape around streams and rivers has been modified by agriculture and other human activities for centuries, leaving management practitioners wondering how much change is acceptable to maintain sustainable fish populations and fisheries practices.
4. With examples from Denmark, this paper attempts to conceptualize the loss in habitat as a result of barriers in lowland streams and rivers, and the repercussions that such alterations may have on rheophilic fish populations. Furthermore, the need for management to address habitat loss and its related consequences concurrently with the improvement of fish passage is emphasized.

     

Fish diversity assessment in the headwaters of the Volga River using environmental DNA metabarcoding

1. The headwaters of the Volga River exhibit large reaches with near‐pristine conditions, and therefore long‐term biodiversity monitoring of this catchment can provide rare and valuable information on a European lowland river. More specifically, freshwater fish species assemblages are a good indicator of ecosystem status, as they are particularly sensitive to environmental changes and hydromorphological alterations. Historical records show that the fish fauna of the Upper Volga has changed over time, both in species composition and in abundance. The construction of the Volga–Kama cascade (a series of large dams) has specifically affected the migration of diadromous species.
2. Environmental DNA metabarcoding offers a non‐invasive approach to determine the number of species in an aquatic ecosystem, as well as their identity and distribution. This approach is especially useful for fish fauna surveys along large rivers and long‐term biomonitoring, with the advantage of having no impact on the species and their habitats.
3. To infer the current fish species diversity and the spatial distribution of each species in the free‐flowing section of the Upper Volga River, as well as in selected tributaries, an environmental DNA metabarcoding approach was applied, using three mitochondrial DNA markers. This method allowed the positive identification of 23 fish species and their respective distributions in the headwaters of the Volga.
4. This assessment provides a valuable example of the application of environmental DNA metabarcoding in a large river system, and constitutes a starting point for future investigations and long‐term biomonitoring in the Upper Volga system. In addition, the results can also serve as a reference for fish diversity assessments of other large European lowland rivers, and can guide future conservation and management measures in the headwaters of the Volga.

     

Adding large woody material into a headwater stream has immediate benefits for macroinvertebrate community structure and function

1. Hydromorphological rehabilitation through installing large woody material (LWM) is increasingly being used to reverse degradation of stream ecosystems. There have been many criticisms of stream rehabilitation projects, because many have not met their goals and many others have not been monitored well enough to assess whether their goals were met.
2. In a before–after–control design (with samples collected 1 year before and two successive years after LWM installation), instream biotopes and their macroinvertebrate assemblages were used as structural and functional units to assess the effectiveness of LWM installed at the Rolleston Brook, a headwater tributary of the River Welland in Leicestershire, UK.
3. The project was successful in enhancing the coefficient of variation of channel water depth and width, wetted surface area, number of instream biotopes, and the biotope diversity in the rehabilitated reach.
4. LWM installation led to significant increases in macroinvertebrate total density, total biomass, and taxon richness. Macroinvertebrate community composition was also enhanced, so that it became more similar to that of the control reach.
5. Small increases in the number of instream biotopes (appearance of gravel and leaf litter) and changes in biotope proportions (decreasing percentage of silt) were significantly related to changes in the macroinvertebrate community metrics in the rehabilitated reach.
6. The results show that using macroinvertebrate community composition is more effective than only using taxon richness and/or diversity metrics for understanding the relationship between LWM installation and macroinvertebrate community responses. To be effective, samples must also be collected in a predefined sampling protocol stratified at the instream biotope level. This approach would be of great benefit in evaluating biodiversity conservation value, and could be incorporated into the advice provided by Natural England concerning restoration and protection of English rivers that are designated as Sites of Special Scientific Interest under UK legislation or Special Areas of Conservation under European legislation.

     

An assessment of the use of remote sensing to map habitat features important to sustaining lamprey populations

• 1. This study describes the use of colour aerial photography and Airborne Thematic Mapper (ATM) multispectral imagery (420–1050 nm) to map gravel‐bed river habitats important to sustaining river lamprey (Lampetra fluviatilis) — an aquatic species with high conservation interest in Europe. The accuracy of the remote sensing approach was assessed by comparing the output from automated mapping of physical habitat features using image analysis and GIS and habitat maps derived from field survey.
• 2. Unsupervised classification of the aerial photography and ATM imagery mapped hydraulic habitat such as pools and riffles with overall accuracies of 57% and 65.5% respectively. Submerged sand and silt deposits, which are important to river lamprey ammocoetes could not be identified on the imagery by simple unsupervised or supervised classification. They could be mapped indirectly, however, by association between their presence and morphological attributes such as backwaters and embayments in the bank profile detectable on the imagery. Remotely determining the likely presence and location of lamprey ammocoete habitat can be useful in planning detailed electrofishing campaigns to estimate lamprey densities, to assess conservation status and any change over time, and to determine the need for restoration strategies.
• 3. The results suggest that on rivers wider than 20 m without a continuous wooded riparian fringe, and where there is good quality imagery, it is possible to automate mapping of physical habitat features important to many river species with high nature conservation interest. As a result organizations charged with monitoring and conserving river species should consider investing in airborne imagery covering river systems of high conservation value.

Copyright © 2007 John Wiley & Sons, Ltd.     

Approaches to the selection of a network of freshwater ecosystems within New Zealand for conservation

1. Although the freshwater environments of New Zealand once comprised an extensive interconnected network of rivers, lakes, and wetlands, their extent, condition, and connectivity have been reduced since human settlement, with consequent impacts on ecosystem functioning and the species that reside within them. An imbalance in the protection of freshwater ecosystems, with significant under‐representation of lowland freshwater ecosystems, makes these the most threatened ecosystems in New Zealand.
2. Recent policy initiatives are attempting to take a whole‐catchment view, i.e. ‘from the mountains to the sea’. There is also an increased focus on the restoration of vulnerable water bodies that still support moderate values, in preference to previous long‐term restoration programmes for the most degraded freshwater sites. The outcomes of these programmes have been less certain, with opportunities lost for systems that are declining in condition but have not yet reached the threshold of degradation for investment.
3. This work demonstrates the gains that can be made through the use of spatial conservation prioritization software to identify priority catchments for freshwater restoration, emphasizing the representation of a full range of ecosystems and species, while also taking account of longitudinal‐connectivity constraints within catchments.
4. Third‐order subcatchments were the most suitable scale for this prioritization, to capture the most important components within the largest river catchments. Populations of important native fish populations and the locations of major terrestrial conservation projects were also considered when assessing priorities; iteratively chosen weightings were applied to control the balance of representation across these different features.
5. Consideration was also given to existing patterns of protection, in order to assess the biodiversity representation within areas currently protected and to identify sites that would provide maximum additional benefits if restored or protected.
6. The resulting subcatchment prioritizations have contributed strongly to regional collaborative restoration processes.

     

Hydromorphological parameters indicating differences between single‐ and multiple‐channel mountain rivers in Germany,in relation to their modification and recovery

• 1. Despite a growing number of river restoration projects in Central Europe targeting hydromorphological improvements, it is still uncommon to evaluate the effects of restoration. Hydromorphological diversity in straightened, single‐channel sections was compared with restored or naturally developed multiple‐channel sections in German mountain rivers to identify parameters suitable for judging conservation value or restoration success.
• 2. Seven multiple‐channel sections were compared with nearby straightened single‐channel sections. Six hydromorphological parameters at macro‐, meso‐ and micro‐scales were recorded with transect point protocols, including aquatic, terrestrial and transient areas and width of channel features (main and secondary channels, sidearms, standing water bodies, bars, banks, floodplains and embankments). Depth, velocity and substrate type were measured at 400 points per river section. With these data 12 metrics were calculated, to provide comparison between the sections.
• 3. All macro‐ and meso‐scale parameters were well differentiated between single‐channel and multiple‐channel sections: mean channel width and shoreline length increased by factors of 2.1 and 2.4, respectively; the average number of channel feature types increased from two to 10 per section.
• 4. Micro‐scale parameters, such as velocity and depth variance, were significantly different between single‐channel sections and most multiple‐channel sections. Substrate composition was more diverse in the restored sections; the share of the major substrate was on average reduced from 75% to 62%. The Spatial Diversity Index described differences in substrate patterns best. The individual parameters correlated only within scales, but rarely between them.
• 5. Rapid assessment of restoration success or judgement of conservation value is made possible by combining simple macro‐ and meso‐scale parameters, e.g. increase of overall width or of transient areas, and presence of bars and islands. Increase in aquatic area and diversity of habitats are the most appropriate micro‐scale parameters required to evaluate habitat suitability for aquatic organisms. For depth and velocity data, variance should be analysed.

Copyright © 2008 John Wiley & Sons, Ltd.     

Improving estimates of richness,habitat associations,and assemblage characteristics of freshwater gastropods

1. Freshwater gastropods are imperilled globally and are among North America's most vulnerable major animal groups. Habitat loss, invasive species, and inadequate information about species distributions and assemblages all impair efforts to conserve freshwater gastropods. Conservation efforts are also impaired by difficulty obtaining and using distributional data for snails and other inconspicuous organisms, which are required to assess habitat associations.
2. A gastropod‐specific sampling protocol was developed and used to survey 110 sites from 24 sub‐basins in two major river basins of the Intermountain West, USA. Habitat associations of individual taxa and groups of taxa that co‐occurred together more frequently than expected by chance were also examined.
3. Using the gastropod‐specific sampling protocol, snails were found at most sites, even in regions where general macroinvertebrate sampling did not detect snails. Thus, these results show that general macroinvertebrate surveys do not accurately reflect the diversity of freshwater gastropods. Although snails of the same family are typically expected to live in the same habitats, this study found that in most cases, within a gastropod family, taxa exhibited unique habitat associations because they co‐occurred more frequently with taxa from different gastropod families. Five genera or sub‐genera were associated with specific mesohabitat or substrate types while two groups of co‐occurring taxa were associated with specific land classes or landform types.
4. For diverse, inconspicuous taxa such as freshwater gastropods, qualitative, class‐specific sampling methods, and analyses of habitat associations based on co‐occurring taxa, rather than relatedness, should facilitate conservation efforts.

     

Restoration effort,habitat mosaics,and macroinvertebrates — does channel form determine community composition?

• 1. In certain lower mountainous regions of Germany multiple‐channel streams constitute the reference condition for stream restoration and conservation efforts. An increasing number of restoration projects re‐establish such stream sections, but their impact on macroinvertebrate communities remains vague and needs further elaboration.
• 2. Seven pairs of single‐ and multiple‐channel sections of mountain rivers were compared in terms of hydromorphology and macroinvertebrate communities. The stream sections were characterized by 16 hydromorphological metrics at various scales, e.g. shore length, channel feature or substrate diversity, flow variability and substrate coverage. Macroinvertebrate data were obtained from 140 substrate‐specific samples, which were combined to form representative communities for each section. Community data were subject to similarity and cluster analyses. Thirty‐five metrics were calculated with the taxa lists, including number of taxa, abundance, feeding type, habitat and current preferences.
• 3. Bray–Curtis similarity was very high (69–77%) between communities of single‐ and multiple‐channel sections. Biological metrics were correlated with hydromorphological parameters. Mean Spearman rank r was 0.59 (absolute values). The biological metrics percentage of the community preferring submerged vegetation, being grazers and scrapers or active filter feeders, percentage of epipotamal preference and the percentage of current preference (rheo‐ to limnophil and rheobiont) were significantly correlated with hydromorphological parameters.
• 4. Differences between stream sections can be attributed to single taxa occurring only in either the single‐ or multiple‐channel sections. These exclusive taxa were mainly found on organic substrates such as living parts of terrestrial plants, large wood, coarse particulate organic matter (CPOM) and mud. Reasons for high similarity of macroinvertebrate communities from single‐ or multiple‐channel sections are discussed, including the influence of large‐scale catchment pressures, length of restored sections and lack of potential re‐colonizers.

Copyright © 2008 John Wiley & Sons, Ltd.     

黄河源区典型弯曲河流底栖动物的生态格局

通过探究黄河源区典型弯曲河流河岸带不同水体(干流、支流和牛轭湖)的底栖动物生态格局,可为黄河生态保护提供基础数据。于2012年7月和2013年6月对兰木错曲12个样点的底栖动物进行采样,同时对样点环境参数进行调查监测,对河流水质、底栖动物组成、多样性及其格局进行分析。结果表明,研究河段基本处于自然状态,水质为I-III类。调查期间共采集底栖动物23科、36属、39种;以水生昆虫为主,占物种总数的76.9%;其次为寡毛纲、腹足纲、甲壳纲,分别占5.1%;线虫纲、双壳纲和蛛形纲最少,仅各占2.6%。除趋势对应分析(DCA)表明,干流、支流和牛轭湖的底栖动物群落存在差异,水文连通性是引起这种差异的主要原因,对群落变化的解释率为37.0%。干流、支流和牛轭湖的底栖动物多样性也存在差异,干流的底栖动物多样性最高,其次是支流和牛轭湖。昆虫纲是干流和牛轭湖中的主要类群,密度组成分别大于53%和85%,甲壳纲是支流中的主要类群,密度组成大于70%;干流的底栖动物功能摄食类群组成最均匀,其中撕食者、直接收集者和刮食者占优势,其密度之和超过90%,支流和牛轭湖的均匀性相对较差,支流中直接收集者的密度比例最大,超过78%,牛轭湖中撕食者的密度比例最大,超过82%。