Stefan Schmutz

Managing aquatic ecosystems and water resources under multiple stress--an introduction to the MARS project.

Water resources globally are affected by a complex mixture of stressors resulting from a range of drivers, including urban and agricultural land use, hydropower generation and climate change. Understanding how stressors interfere and impact upon ecological status and ecosystem services is essential for developing effective River Basin Management Plans and shaping future environmental policy. This paper details the nature of these problems for Europes water resources and the need to find solutions at a range of spatial scales. In terms of the latter, we describe the aims and approaches of the EU-funded project MARS (Managing Aquatic ecosystems and water Resources under multiple Stress) and the conceptual and analytical framework that it is adopting to provide this knowledge, understanding and tools needed to address multiple stressors. MARS is operating at three scales: At the water body scale, the mechanistic understanding of stressor interactions and their impact upon water resources, ecological status and ecosystem services will be examined through multi-factorial experiments and the analysis of long time-series. At the river basin scale, modelling and empirical approaches will be adopted to characterise relationships between multiple stressors and ecological responses, functions, services and water resources. The effects of future land use and mitigation scenarios in 16 European river basins will be assessed. At the European scale, large-scale spatial analysis will be carried out to identify the relationships amongst stress intensity, ecological status and service provision, with a special focus on large transboundary rivers, lakes and fish. The project will support managers and policy makers in the practical implementation of the Water Framework Directive (WFD), of related legislation and of the Blueprint to Safeguard Europes Water Resources by advising the 3rd River Basin Management Planning cycle, the revision of the WFD and by developing new tools for diagnosing and predicting multiple stressors.

A Predictive Index of Biotic Integrity Model for Aquatic-Vertebrate Assemblages of Western U.S. Streams

Abstract Because of natural environmental and faunal differences and scientific perspectives, numerous indices of biological integrity (IBIs) have been developed at local, state, and regional scales in the USA. These multiple IBIs, plus different criteria for judging impairment, hinder rigorous national and multistate assessments. Many IBI metrics are calibrated for water body size, but none are calibrated explicitly for other equally important natural variables such as air temperature, channel gradient, or geology. We developed a predictive aquatic-vertebrate IBI model using a total of 871 stream sites (including 162 least-disturbed and 163 most-disturbed sites) sampled as part of the U.S. Environmental Protection Agencys Environmental Monitoring and Assessment Program survey of 12 conterminous western U.S. states. The selected IBI metrics (calculated from both fish and aquatic amphibians) were vertebrate species richness, benthic native species richness, assemblage tolerance index, proportion of invert...

Multiple human pressures and their spatial patterns in European running waters

Abstract Running water ecosystems of Europe are affected by various human pressures. However, little is known about the prevalence, spatial patterns, interactions with natural environment and co-occurrence of pressures. This study represents the first high-resolution data analysis of human pressures at the European scale, where important pressure criteria for 9330 sampling sites in 14 European countries were analysed. We identified 15 criteria describing major anthropogenic degradation and combined these into a global pressure index by taking additive effects of multiple pressures into account. Rivers are affected by alterations of water quality (59%), hydrology (41%) and morphology (38%). Connectivity is disrupted at the catchment level in 85% and 35% at the river segment level. Approximately 31% of all sites are affected by one, 29% by two, 28% by three and 12% by four pressure groups; only 21% are unaffected. In total, 47% of the sites are multi-impacted. Approximately 90% of lowland rivers are impacted by a combination of all four pressure groups.

A multi-level concept for fish-based, river-type-specific assessment of ecological integrity

We propose a multi-level concept for fish-based assessment (MuLFA) of the ecological integrity of running waters. This concept is designed for large-scale monitoring programmes such as required for the proposed Water Framework Directive of the EU. Out of five different biological organisation levels (fauna, community, guild, population and individual), we propose seven criteria: River-type-specific species, species with self-sustaining populations, fish region, number of guilds, guild composition, population size and population age structure. The principle of the MuLFA is based on assessing the deviation from undisturbed reference conditions. Reference conditions have to be compiled for every distinct river type using historical fish and abiotic data, present river-type-specific reference sites and reference models. The final assessment procedure is done by comparing the assessment reach with the reference conditions using a 5-tiered normative scheme and assigning that reach to the level of highest coincidence. The benefit of the MuLFA is its potential for consistent sensitivity to low- and high-dose human alterations, and due to its general character, its adaptability to all river types.

The effects of recreated instream and ecotone structures on the fish fauna of an epipotamal river

Investigations of fifteen sections of seven Austrian epipotamal (barbel region) streams between 1981 and 1984 demonstrate the impact of instream river bed structures on fish communities. Reduced spatial heterogeneity due to river straightening resulted in decreasing species number, diversity, stock density and biomass. Reincreased variability of the river bed in the frame of a subsequent restructuring project improved all community-specific values significantly within a 3-year investigation period (1988–1990). Besides the regained habitat variability in form of riffle pool sequences and other instream structures, the newly created riparian zones obviously provided important niches, e.g. as refuge areas during flooding and as nursery grounds for fish fry. The positive effects of the recreated land/water ecotone are discussed with respect to river restoration projects.

Fundamentals of fish ecological integrity and their relation to the extended serial discontinuity concept

Current ecological theories and concepts describe running waters as four-dimensional systems, their longitudinal, lateral and vertical linkages, interactions and exchange processes varying over time and over different scales. According to Ward & Stanford’s (1983) extended serial discontinuity concept (ESDC), along a three-reach river, model the relative strength of the longitudinal pathways is highest in the constrained headwaters, vertical interactions reach their maximum in the braided middle course and lateral connectivity plays the major role in alluvial floodplain rivers. The present paper examines the general tenets of the ESDC from a fundamental fish ecology perspective. Specifically, it focuses on the degree to which the spatial/temporal connectivity requirements of fish communities or key fish species along a schematic longitudinal river course are compatible with the underlying principles of the ESDC and whether these requirements provide basic criteria for assessing the ecological integrity of running waters. From the fish ecological perspective, the examples provided here demonstrate a principle agreement with the concept of the four-dimensional nature of running waters, whose key functional and structural elements are spatial/temporal fluvial dynamics, disturbances, connectivity, succession and ecotones. Fish are particularly useful indicators of the temporally variable connectivities on the full range of scales at the three spatial dimensions. As far as the habitat requirements of typical species/developmental stages are concerned, two major modifications of the ESDC are needed. In constrained headwaters, in addition to longitudinal connectivity, the crucial importance of the vertical pathway river/bed sediments for reproduction must be emphasized. Also, in addition to lateral connectivity, longitudinal connectivity remains a vital basis for potamal fish communities in alluvial braided and meandering zones.

River restoration concepts — goals and perspectives

An analysis of restoration projects carried out both in Austria and abroad shows that most projects are limited to design measures within the river bed with the general intention to increase habitat diversity. The various measures are not based on the type-specific characteristics of the river and thus there is a danger of creating uniform restoration stretches, independent of the specific landscape area, river morphology, discharge regime or site specific biocoenoses. Such proceeding lacks in considering a comprehensive improvement of ecological functioning of the whole river-system. To meet those demands a type-specific guiding view (‘Leitbild’) has to be developed based on the pristine river conditions.The comparison of the river pattern including the characteristic features of its unmodified state with the actual situation leads to a comprehensive set of measures. The essential goals of such management-concepts are the integrity of the river habitat, self-regulation and self-regeneration, the preservation of intact resources, as well as the possibility to experience the uniqueness, diversity and beauty of natural river landscapes.

Performance of Hatchery-Reared Brown Trout and Their Effects on Wild Fish in Two Small Austrian Streams

Abstract Two small streams of contrasting physicochemical character, one crystalline and one limestone, were experimentally stocked with brown trout Salmo trutta. The study design involved doubling (three sites) or tripling (three sites) the number of large-sized resident fish (>179 or >199 mm total length, dependant on the stream) with an equal mixture of two hatchery strains; three additional sites were left unstocked as controls. In the limestone stream, short-term survival (3 months) of hatchery fish (both strains) was 80%, compared with 90% for wild fish. In the crystalline stream, survival of hatchery fish was 48% and 62% (dependant on strain), compared with 49% for wild fish. After 12 months, the survival of hatchery strains declined precipitously (range: 1–19%), compared with wild fish (range: 13–52%), dependant on stream and strain. After 3 months, about half of the recaptured hatchery fish were caught outside the 200-m-long sites in which they were stocked. Percent movement of wild fish was affe...

Identification of rivers with high and good habitat quality: methodological approach and applications in Austria

The investigation of the 52 largest Austrian rivers with catchment areas >500 km2 (Danube River excluded) provides a national estimate of the ecological status of Austria’s rivers and an example of the current status of European alpine rivers. Emphasis is placed on evaluation criteria, such as morphological character, instream structures, longitudinal river corridor, lateral connectivity and hydrological regime compared with original conditions. This assessment and evaluation of nearly 5000 river kilometers identifies the remaining river stretches with high habitat quality as well as those stretches that have been altered by systematic channelisation or hydropower development. Altogether, about 80% (3900 km) of the stretches in Austria’s ‘larger’ rivers are moderately to heavily impacted by human activity and thus no longer correspond to their original channel form and dynamics. Impoundment, water diversion and hydropeaking each impact the hydrology of approximately 20% of the above stretches. Only about 20% of all investigated river stretches can still be classified as having high or good habitat quality and as retaining essentially natural functions. Using natural conditions as a reference, the most severe losses have occurred in reaches that were originally braided or meandering. Analysing the amount of unaltered river stretches according to biocoenotic regions, 37% (523 km) of the originally rhithral (trout) region (1416 km) and 18% (480 km) of the originally hyporhithral (grayling) region (2739 km) remain today in high or good habitat quality. Only a few intact river stretches (totaling 43 km) can be found along formerly potamal river reaches (731 km). These data underline the rarity and, therefore, national importance of the remaining unspoiled aquatic habitats. The results presented here form a basis for water resource management and nature conservation strategies, as well as for restoration programs. In particular, these investigations help to fulfill the requirements of the EU-Water Framework Directive by assisting to delineate and characterise reference sites of different river types.

Contrasting the roles of section length and instream habitat enhancement for river restoration success: a field study of 20 European restoration projects

Restoration of river hydromorphology often has limited detected effects on river biota. One frequently discussed reason is that the restored river length is insufficient to allow populations to develop and give the room for geomorphological processes to occur. We investigated ten pairs of restored river sections of which one was a large project involving a long, intensively restored river section and one represented a smaller restoration effort. The restoration effect was quantified by comparing each restored river section to an upstream non-restored section. We sampled the following response variables: habitat composition in the river and its floodplain, three aquatic organism groups (aquatic macrophytes, benthic invertebrates and fish), two floodplain-inhabiting organism groups (floodplain vegetation, ground beetles), as well as food web composition and land-water interactions reflected by stable isotopes. For each response variable, we compared the difference in dissimilarity of the restored and nearby non-restored section between the larger and the smaller restoration projects. In a second step, we regrouped the pairs and compared restored sections with large changes in substrate composition to those with small changes. When comparing all restored to all non-restored sections, ground beetles were most strongly responding to restoration, followed by fish, floodplain vegetation, benthic invertebrates and aquatic macrophytes. Aquatic habitats and stable isotope signatures responded less strongly. When grouping the restored sections by project size, there was no difference in the response to restoration between the projects targeting long and short river sections with regard to any of the measured response variables except nitrogen isotopic composition. In contrast, when grouping the restored sections by substrate composition, the responses of fish, benthic invertebrates, aquatic macrophytes, floodplain vegetation and nitrogen isotopic composition were greater in sections with larger changes in substrate composition as compared to those with smaller changes. Synthesis and applications. The effects of hydromorphological restoration measures on aquatic and floodplain biota strongly depend on the creation of habitat for aquatic organisms, which were limited or not present prior to restoration. These positive effects on habitats are not necessarily related to the restored river length. Therefore, we recommend a focus on habitat enhancement in river restoration projects. The effects of hydromorphological restoration measures on aquatic and floodplain biota strongly depend on the creation of habitat for aquatic organisms, which were limited or not present prior to restoration. These positive effects on habitats are not necessarily related to the restored river length. Therefore, we recommend a focus on habitat enhancement in river restoration projects.