Scientific Publications

This section gives the overview of scientific publications. Publications are listed in reversed chronological order, i.e. new ones appear on top.
For each publication you will find title, abstract, full reference and DOI.
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Information for this can be found through the DOI.

Habitat rehabilitation in urban waterways: the ecological potential of bank protection structures for benthic invertebrates (Weber et al. 2017)

Compensating for the adverse ecological impacts of waterway development and improving their ecological functioning to achieve good ecological potential (GEP) have become mandatory within the European Union (EU). The technical rehabilitation measures presented here aim to functionally minimize the hydraulic impacts of navigation on aquatic biota in highly urbanized waterways. Their ecological functioning and potential to enhance biodiversity locally was assessed by comparing their macro-invertebrate community composition with nearby non-restored sites. 

Response of fish communities in rivers subjected to a high sediment load (Valero et al. 2016)

Erosion and sediment yield are a significant problem in the Guadalquivir River basin. Such phenomena are largely driven by a land use devoted to intensive cultivation of olive trees, with a large socioeconomic influence in Andalusia. This sediment overload in rivers causes serious impacts on all fluvial ecosystem components. In this study we assess the chronic effect of sediment yield on fish communities at 104 river sites located in two different sub-catchments – the Bembézar and Guadajoz rivers – both with different lithological composition and erosion rates. Sediment yield was estimated using a semi-quantitative Factorial Score Model (FSM), developed specifically for Spanish rivers. The fish populations of both basins were evaluated in composition and abundances by the study of Fernández-Delgado et al., 2014. The influence of sediment yield on the fish community was analyzed using General Additive Models.

Responses of fish and invertebrates to floods and droughts in Europe (Piniewski et al. 2016)

Floods and droughts, two opposite natural components of streamflow regimes, are known to regulate population size and species diversity. Quantifiable measures of these disturbances and their subsequent ecological responses are needed to synthesize the knowledge on flow–ecosystem relationships. This study for the first time combines the systematic review approach used to collect evidence on the ecological responses to floods and droughts in Europe with the statistical methods used to quantify the extreme events severity. 

Environmental and spatial controls of taxonomic versus trait composition of stream biota (Göthe et al. 2016)

The spatial organisation of biotic communities derives from factors operating at a wide range of spatial and temporal scales. Despite strong scientific evidence of prevalent spatial control of community composition in freshwater ecosystems, local environmental factors are often considered as the main drivers of community change. Furthermore, taxonomic approaches are most frequently used, and few studies have compared the relative importance of local and regional control of trait versus the taxonomic composition in stream ecosystems.

Using a spatially dense data set covering all stream sizes in a lowland European region of c. 42 000 km2 and three organism groups (macrophytes, macroinvertebrates and fishes), we compared the relative importance of spatial and environmental determinants of species and trait composition in the study streams, classified into headwaters (stream order 1–2) and downstream sites (stream order >2).

Linking environmental flows to sediment dynamics (García de Jalón et al 2016)

This is a policy discussion paper aimed at addressing possible alternative approaches for environmental flows (e-Flows) assessment and identification within the context of best strategies for fluvial restoration. We focus on dammed rivers in Mediterranean regions. Fluvial species and their ecological integrity are the result of their evolutionary adaptation to river habitats. Flowing water is the main driver for development and maintenance of these habitats, which is why e-Flows are needed where societal demands are depleting water resources. Fluvial habitats are also shaped by the combined interaction of water, sediments, woody/organic material, and riparian vegetation. 

Effective restoration of aquatic ecosystems: scaling the barriers (Friberg et al 2016)

The focus of ecosystem restoration has recently shifted from pure rehabilitation objectives to both improving ecological functioning and the delivery of ecosystem services. However, these different targets need to be integrated to create a unified, synergistic, and balanced restoration approach. This should be done by combining state-of-the-art knowledge from natural and social sciences to create manageable units of restoration that consider both the temporal and multiple spatial scales of ecosystems, legislative units, and policy agendas. 

A new paradigm for biomonitoring: an example building on the Danish Stream Plant Index (Baattrup-Pedersen et al 2016)

Despite intensive efforts for more than a decade to develop Water Framework-compliant assessment systems, shortcomings continue to appear. In particular, the lack of reference conditions has hindered the development of assessment systems capturing the heart of the Water Framework Directive (WFD) – that ecological status should be set as the deviation from the natural, undisturbed condition. Recently, the Danish Stream Plant Index (DSPI) was developed. This system contrasts existing systems in that it builds on an expert interpretation of the normative definitions of ecological status classes in the WFD without taking pressure–impact relationships into account.

Effective River Restoration in the 21st Century: From Trial and Error to Novel Evidence-Based Approaches (Friberg et al. 2016)

This paper is a comprehensive and updated overview of river restoration and covers all relevant aspects from drivers of restoration, linkages between hydromorphology and biota, the current restoration paradigm, effects of restorations to future directions and ways forward in the way we conduct river restoration. A large part of this paper is based on the outcomes of the REFORM (REstoring rivers FOR effective catchment Management, http://reformrivers.eu/) project that was funded by EU's 7th Framework Programme (2011–15). REFORM included the most comprehensive comparison, to date, of existing river restorations across Europe and their effect on biota, both in relation to preintervention state and project size in terms of river length restored. The REFORM project outcomes are supplemented by an extensive literature review and two case studies to illustrate key points. 

Evaluating good-practice cases for river restoration across Europe: context, methodological framework, selected results and recommendations (Muhar et al. 2016)

This introductory paper presents 20 river restoration cases throughout Europe that were investigated in the EU-funded research project REFORM. In the following, this special issue provides seven specific papers that highlight and discuss the effects of restoration on the investigated river–floodplain systems. Additionally, restoration success was estimated from a socio-economic perspective. 

Preface: Effects of hydromorphological river restoration—a comprehensive field investigation of 20 European projects (Kail et al. 2016)

All over Europe, river stretches are being restored to achieve “good ecological status” or “good ecological potential,” the targets of the EU Water Framework Directive. Hydromorphological restoration is one of the most frequently applied methods, including re-meandering, widening, and the re-connection of river and floodplain. Within the EU-funded project Restoring rivers FOR effective catchment Management (REFORM), an international team of scientists has addressed this question, by studying twenty restored river stretches in ten European catchments, always in comparison to a nearby non-restored stretch of the same river. Ten of the restored river sections represented a major restoration effort and a comparatively long restored river stretch, while the other ten restored sections were shorter. The special issue gives insight in the details of the study.

Time is no healer: increasing restoration age does not lead to improved benthic invertebrate communities in restored river reaches (Leps et al. 2016)

Evidence for successful restoration of riverine communities is scarce, particularly for benthic invertebrates. Among the multitude of reasons discussed so far for the lack of observed effects is too short of a time span between implementation and monitoring. Yet, studies that explicitly focus on the importance of restoration age are rare.

We present a comprehensive study based on 44 river restoration projects in Germany, focusing on standardized benthic invertebrate sampling. A broad gradient ranging from 1 to 25 years in restoration age was available. In contrast to clear improvements in habitat heterogeneity, benthic community responses to restoration were inconsistent when compared to control sections. 

The Hydromorphological Evaluation Tool (HYMET) (Klösch & Habersack 2016)

River engineering structures, such as bank protection or bed sills, act as constraints on the hydromorphology of rivers and limit morphodynamic processes. Accordingly, the deviations of a river's morphology from a natural reference condition have been attributed to the degree of artificiality in the observed river section and river restoration works mainly aimed at reducing artificial constraints within the river reach.

Long-term response of salmonid populations to habitat restoration in a boreal forest stream (Van Zyll de Jong & Cowx 2016)

Assessing the sustainability of restoration measures for salmonid populations and their habitat is limited due to a lack of long-term evaluations. In this paper we report on a study to assess the effect of boulder clusters, V-dams and half-log covers on stream habitat and population abundance of Atlantic salmon and brook trout two decades after installation. Structures were installed in Joe Farrell’s Brook, Newfoundland Canada in 1993 and fish population and habitat parameters were initially measured annually from 1993 to 1995. All stream sites were re-sampled in 2014. 

Quantifying the relative importance of natural variables, human disturbance and spatial processes in ecological status indicators of boreal lakes (Alahuhta & Aroviita 2016)

Spatial processes are increasingly associated with species distributions in freshwaters. However, these processes are usually neglected in bioassessment techniques, which may introduce uncontrolled variation in ecological indicators used to express human disturbance. We used partial linear regression to quantify the relative importance of natural variables, human disturbance and spatial variables in structuring variation in boreal lake status indicators based on six biological indicator groups (phytoplankton, macrophytes, diatoms, littoral and profundal macroinvertebrates and fish). 

Macrophytes in boreal streams: Characterizing and predicting native occurrence and abundance to assess human impact (Rääpysjärvi et al. 2016)

Macrophytes are a structurally and functionally essential element of stream ecosystems and therefore indispensable in assessment, protection and restoration of streams. Modelling based on continuous environmental gradients offers a potential approach to predict natural variability of communities and thereby improve detection of anthropogenic community change. Using data from minimally disturbed streams, we described natural macrophyte assemblages in pool and riffle habitats separately and in combination, and explored their variation across large scale environmental gradients. 

Meander reconnection method determines restoration success for macroinvertebrate communities in a German lowland river (Lorenz et al. 2016)

Re-meandering of degraded rivers is a frequently implemented measure in river restoration. A simple solution is reconnection of old meanders; however, its success likely depends on the reconnection method. We conducted a field study to analyze the benefits of a fully reconnected (fully opened meander, blocked main channel) and a partially reconnected meander (opened downstream, pipe bypass from main channel upstream, still open main channel) for macroinvertebrate communities in a German lowland river. 

Disentangling the responses of boreal stream assemblages to low stressor levels of diffuse pollution and altered channel morphology (Turunen et al. 2016)

Non-point diffuse pollution from land use and alteration of hydromorphology are among the most detrimental stressors to stream ecosystems. We explored the independent and interactive effects of morphological channel alteration (channelization for water transport of timber) and diffuse pollution on species richness and community structure of four organism groups in boreal streams: diatoms, macrophytes, macroinvertebrates, and fish. Furthermore, the effect of these stressors on stream condition was evaluated by Ecological Quality Ratios (EQR) from the national Water Framework Directive (WFD) assessment system.

Incorporating catchment to reach scale processes into hydromorphological assessment in the UK (England & Gurnell 2016)

Hydromorphological pressures and the measures undertaken to address them are an important element of the delivery of the WFD within the United Kingdom. While assessment procedures currently employed gather useful morphological information for river reaches and their immediate margins and some process information, crucial information on key processes is missing and information gathered on the riparian zone and floodplain is limited. This article presents a newly developed framework that enables existing data to be placed within a multiscale, process-based context. 

Integrating and extending ecological river assessment: concept and test with two restoration projects (Paillex et al. 2017)

While the number of river restoration projects is increasing, studies on their success or failure relative to expectations are still rare. Only a few decision support methodologies and integrative methods for evaluating the ecological status of rivers are used in river restoration projects, thereby limiting informed management decisions in restoration planning as well as success control. Moreover, studies quantifying river restoration effects are often based on the assessment of a single organism group, and the effects on terrestrial communities are often neglected. In addition, potential effects of water quality or hydrological degradation are often not considered for the evaluation of restoration projects.

We used multi-attribute value theory to re-formulate an existing river assessment protocol and extend it to a more comprehensive, integrated ecological assessment program. We considered habitat conditions, water quality regarding nutrients, micropollutants and heavy metals, and five instream and terrestrial organism groups (fish, benthic invertebrates, aquatic vegetation, ground beetles and riparian vegetation). The physical, chemical and biological states of the rivers were assessed separately and combined to value the overall ecological state.

Fluvial Corridor Changes Over Time in Regulated and Non‐Regulated Rivers (Upper Esla River, NW Spain) (Martínez‐Fernández et al. 2016)

Over the last decades, rivers and fluvial corridors have been noticeably modified from their natural conditions. In general, damming and other in-channel human interventions have been traditionally considered as the main drivers of change. However, recent studies highlight the influence of climate, hillslope and floodplain cover changes over fluvial corridor dynamics. The present study illustrates the channel morphology and riparian vegetation responses observed in three gravel bed rivers located in the Upper Esla River, north-west of Spain. 

The effect of weirs on nutrient concentrations (Cisowska & Hutchins 2016)

The removal of a weir in 1999 from the River Nidd in Yorkshire, UK, was assessed in terms of its impact on in-stream nitrate removal along a 15.8 km long stretch of river. Models of channel hydraulics and denitrification quantified the impact on an annual basis, using, as inputs, river flow, water temperature, water quality data and cross-section geometry collected both before and after the weir was removed. 

Functional trait composition of aquatic plants can serve to disentangle multiple interacting stressors in lowland streams (Baattrup-Pedersen et al. 2016)

Historically, close attention has been paid to negative impacts associated with nutrient loads to streams and rivers, but today hydromorphological alterations are considered increasingly implicated when lowland streams do not achieve good ecological status. Here, we explore if trait-abundance patterns of aquatic plants change along gradients in hydromorphological degradation and eutrophication in lowland stream sites located in Denmark. 

Distinct patterns of interaction between vegetation and morphodynamics (van Oorschot et al. 2016)

Dynamic interaction between river morphodynamics and vegetation affects river channel patterns and populations of riparian species. A range of numerical models exists to investigate the interaction between vegetation and morphodynamics. However, many of these models oversimplify either the morphodynamics or the vegetation dynamics, which hampers the development of predictive models for river management.

River restoration and the trophic structure of benthic invertebrate communities across 16 European restoration projects (Kupilas et al 2015)

River restoration enhances not only habitat diversity in the stream channel and riparian zone, but also retention of organic matter, which together are expected to enhance aquatic-terrestrial linkages, and the range of autochthonous and allochthonous resources. Consequently, alterations of food-web structure and trophic relationships can be expected. We applied stable isotope analysis (δ13C, δ15N) to characterize changes in the trophic structure of benthic invertebrate communities between paired restored and unrestored river reaches across 16 European catchments.

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