Leopold Füreder

Benthic Algae in High Altitude Streams of the Alps – a Neglected Component of the Aquatic Biota

This is a review on benthic algae from streams situated above the tree line in the Alps. It integrates published and unpublished data from alpine streams in Austria and in the Trento Province (Northern Italy). The main focus is on the structural and taxonomic composition of benthic algae including macro- and micro-algae and their contribution to the epilithic biofilm and the stream food-web. The environmental conditions relevant to algae within the two major stream types, the glacial (glacier-fed) and non-glacial krenal (spring-fed) stream are discussed. The paper considers both the maximum possible structural complexity of transverse algae zonation in cascading alpine/subalpine stream segments, and the effects of glacial water on species richness in the Central Alps in Austria. Autecological data are given for 46 common diatoms from 42 sites in the Central Eastern and Southern Central Alps and for 30 algae in addition to diatoms for 22 streams in the Central Eastern Alps. Since data on responses of benthic algae to the harsh conditions in high altitude Alpine streams are very scarce, results from literature and the author’s experiences from these and other mountain stream types are synthesized to formulate major objectives for future research in benthic high altitude Alpine stream ecology.

SPECIES OF BRANCHIOBDELLIDAE (ANNELIDA) ON FRESHWATER CRAYFISH IN SOUTH TYROL (NORTHERN ITALY)

Twenty-eight freshwater crayfish were collected from 8 streams and one small lake in the province of South Tyrol (North Italy) from autumn 1999 to spring 2001, in order to investigate the presence of branchiobdellidans. At 6 of the streams the white clawed crayfish (Austropotamobius pallipes italicus) was collected, while the noble crayfish (Astacus astacus), the exotic species: signal crayfish (Pacifastacus leniusculus) and spiny-cheek crayfish (Orconectes limosus) were respectively caught at the other 2 streams and at the lake. Except for O. limosus, branchiobdellidans were observed on all crayfish examined. On noble crayfish, specimens of Branchiobdella italica and Branchiobdella hexodonta were found on the same host. Branchiobdella italica was largely recovered from all white clawed crayfish. The specimens of signal crayfish were found to carry only Xironogiton victoriensis.

Alpine river ecosystem response to glacial and anthropogenic flow pulses

Alpine glacier-fed river hydrology, chemistry, and biology can vary significantly in space and over diurnal to interannual time scales as a function of dynamic inputs of water from snow, ice, and ground water. The sensitivity of biota to these water-source dynamics potentially makes them susceptible to hydrological changes induced by anthropogenic activities, such as flow regulation, but most alpine studies have been focused on intact rivers during summer only. We examined the spatiotemporal dynamics of physicochemical habitat and macroinvertebrate assemblages in a high-altitude (>2000 m) floodplain in the European Alps over an 18-mo period. We present a novel insight into the river system and macroinvertebrate assemblage responses to natural glacier-melt-driven expansion–contraction of unregulated river sites and to intermittent flow pulses caused by hydropower regulation. Mainstem glacier-fed sites had cyclical seasonal dynamics in macroinvertebrate assemblage composition that shifted to be partly reminiscent of groundwater tributaries in winter then back to melt water in the following spring. Significant unimodal relationships were found between glacial influence and macroinvertebrate assemblage density, richness, Simpson’s diversity, evenness, and β diversity. These relationships suggest that glacial influence can positively affect biodiversity where glacier melt water mixes with nonglacial water and habitat diversity is maximized. Regulation-induced flow pulses led to inconsistent responses among macroinvertebrates, with no significant effects in summer 2008 but increased density and decreased taxonomic richness in 2009. Assemblage composition was unaffected by reservoir releases despite significant increases in water temperature and discharge at these times. The effects of alpine river management for hydropower production on macroinvertebrate assemblages in this river system appear to be relatively minor, but further studies should be undertaken in other alpine locations to assess the generality of this finding.

Glacier shrinkage driving global changes in downstream systems

Glaciers cover ∼10% of the Earth’s land surface, but they are shrinking rapidly across most parts of the world, leading to cascading impacts on downstream systems. Glaciers impart unique footprints on river flow at times when other water sources are low. Changes in river hydrology and morphology caused by climate-induced glacier loss are projected to be the greatest of any hydrological system, with major implications for riverine and near-shore marine environments. Here, we synthesize current evidence of how glacier shrinkage will alter hydrological regimes, sediment transport, and biogeochemical and contaminant fluxes from rivers to oceans. This will profoundly influence the natural environment, including many facets of biodiversity, and the ecosystem services that glacier-fed rivers provide to humans, particularly provision of water for agriculture, hydropower, and consumption. We conclude that human society must plan adaptation and mitigation measures for the full breadth of impacts in all affected regions caused by glacier shrinkage.

The 50 most important questions relating to the maintenance and restoration of an ecological continuum in the European Alps.

The European Alps harbour a unique and species-rich biodiversity, which is increasingly impacted by habitat fragmentation through land-use changes, urbanization and expanding transport infrastructure. In this study, we identified the 50 most important questions relating to the maintenance and restoration of an ecological continuum – the connectedness of ecological processes across many scales including trophic relationship and disturbance processes and hydro-ecological flows in the European Alps. We initiated and implemented a trans-national priority setting exercise, inviting 48 institutions including researchers, conservation practitioners, NGOs, policymakers and administrators from the Alpine region. The exercise was composed of an initial call for pertinent questions, a first online evaluation of the received questions and a final discussion and selection process during a joint workshop. The participating institutions generated 484 initial questions, which were condensed to the 50 most important questions by 16 workshop participants. We suggest new approaches in tackling the issue of an ecological continuum in the Alps by analysing and classifying the characteristics of the resulting questions in a non-prioritized form as well as in a visual conceptualisation of the inter-dependencies among these questions. This priority setting exercise will support research and funding institutions in channelling their capacities and resources towards questions that need to be urgently addressed in order to facilitate significant progress in biodiversity conservation in the European Alps.

Associations between stream habitat characteristics and native and alien crayfish occurrence

Human mediated introductions of non-indigenous crayfish species (NICS) are responsible for their rapid colonisation of European freshwaters. The introduction of North American crayfish is furthermore linked to the spread of crayfish plague and the decline of indigenous crayfish species (ICS). As the management of ICS and NICS have become necessary, a detailed knowledge on their distribution and ecological requirements is needed. We studied the current range of native noble crayfish Astacus astacus and stone crayfish Austropotamobius torrentium, as well as alien signal crayfish Pacifastacus leniusculus in Carinthia (Austria) and evaluated environmental and physical habitat features in streams with and without crayfish. Meanwhile, the loss of many ICS populations was recorded and alien P. leniusculus was found to be widespread in this region. Most of the habitat features of streams having crayfish differed significantly from sites lacking crayfish for at least one investigated native or alien species. Furthermore, multivariate and regression analyses showed specific differences in the habitat use of the investigated crayfish. Our results showed that the presence of alien P. leniusculus was associated with larger and smoother sloped lowland rivers, while the occurrence of the two native species was confined to smaller streams either at higher altitudes and with distinct physical habitat conditions (A. torrentium) or with moderate water temperatures (A. astacus). This study helps to identify potential refuge areas for the endangered native species and to predict the further spread of the most common non-native crayfish species in European streams.

Towards a definition of environmental niches in alpine streams by employing chironomid species preferences

Macroinvertebrates are widely used as indicators to detect and assess anthropogenic impacts on freshwater ecosystems. However, despite being considered useful in indicating effects of environmental change in alpine catchments, little is known about species preferences for local conditions in such environments. In exploring the occurrence of 59 taxa within the dipteran family Chironomidae in relation to key-environmental variables in alpine and sub-alpine streams, we showed that sediment load, water temperature, periphyton density, and fine particulate organic matter mostly explain assemblage structures. Two-way-cluster analyses identified stream-type specific assemblages, indicator value analysis defined indicator species for glacial and non-glacial streams, and weighted averaging regression models confined preferences for local environmental conditions by summing their optima and tolerance widths regarding environmental key factors. The definition of habitat requirements identified stenoecious taxa with preferences for high and low values of respective variables thus identified most suitable indicators for future studies. Our work reveals manifold preferences within the dominant benthic invertebrate family, underlines their enormous potential for monitoring purposes, and is a step forward in better understanding ecosystem properties and biodiversity. Fundamental requirements for these kinds of indicative traits, essential to understand cause–effect relationships in environmental change issues, are a robust taxonomy and a comprehensive set of physical and chemical data.

Seasonal abundance and community structure of Chironomidae in two contrasting high alpine streams

In high alpine areas, locared between the tree !ine and rhe permanent snow !ine, three types of streams can generally be distinguished: glacier-fed (kryal), spring-fed streams (krenal) and rainor snow-melt dominated (rhithral) streams (WARD 1994, MrLNER & PErrs 1994). Each of rhese stream types has a different ser of abiotic conditions, which affect the inverrebrate fauna in different ways (TocKNER et al. I 997, FüREDER 1999). The invertebrates of high alpine streams consist of members of specific orders some of which are able to survive the most unfavorable conditions. Within the insect orders, chironomids usually are dominant in high alpine streams. Especially in glacial streams, chironomids of the genus Diamesa are the predominant benthic animals within the aquatic insect community (BRETSCHKO 1969, STEFFAN 1974, KoWNACKA & KoWNACKr 1975). WARD (1994) and Mn.NER & PErrs (1994) have summarized the abiotic and biotic features of al p ine streams and MrLNER & PErrs (1994) presented a conceptual model where glacial rivers and their communities can be explained given the influence of temperature, channel form and stability. However, many aspects in high alpine stream ecology still remain incomplete. Although the summer dominance of Diamesinae is the common feature of high alpine streams, rhe winter situation has nor been described in detail. The aim of this srudy is to compare the chironomid community from two high alpine streams located above the tree !ine and to describe the seasonal and longitudinal parrerns.

Functional diversity and community assembly of river invertebrates show globally consistent responses to decreasing glacier cover

Global change threatens invertebrate biodiversity and its central role in numerous ecosystem functions and services. Functional trait analyses have been advocated to uncover global mechanisms behind biodiversity responses to environmental change, but the application of this approach for invertebrates is underdeveloped relative to other organism groups. From an evaluation of 363 records comprising >1.23 million invertebrates collected from rivers across nine biogeographic regions on three continents, consistent responses of community trait composition and diversity to replicated gradients of reduced glacier cover are demonstrated. After accounting for a systematic regional effect of latitude, the processes shaping river invertebrate functional diversity are globally consistent. Analyses nested within individual regions identified an increase in functional diversity as glacier cover decreases. Community assembly models demonstrated that dispersal limitation was the dominant process underlying these patterns, although environmental filtering was also evident in highly glacierized basins. These findings indicate that predictable mechanisms govern river invertebrate community responses to decreasing glacier cover globally.Analysing >1 million river invertebrates from nine biogeographic regions, the authors show that functional trait diversity increases consistently as glacier cover decreases.

The River Volga headwaters: Inventory, biodiversity and conservation

River headwaters in the East European lowlands, such as the Upper Volga River, still contain large reaches exhibiting natural conditions and unaltered type-specific fauna. This article focuses on macroinvertebrate assemblages of this intact lowland river system. The presented inventory on aquatic biodiversity and habitat-specific invertebrate assemblages provides a basis to test general ecological theories in large European rivers and to define future management. A total of 204 taxa in seven phyla were identified in the headwaters of the Volga River, i.e. along 446 river kilometres, and its main tributaries. Arthropods were the most diverse group, followed by Annelida and Mollusca. Many species (up to 41 %) of the lake littoral were also common in the slow flowing (lentic) section of the river. Diversity, abundance and biomass increased along the river course. The number of reference taxa, defined in a previous paper, also increased downstream from 15 to 21. From the 30 tributaries 120 taxa were identified; 19 of which were from 24 reference taxa. Analysis of beta-diversity showed that 50 % of species were common to the main river and its tributaries. The Upper Volga lakes can be characterised as Chironomus plumosus lakes. The natural free flowing section and its tributaries comprise a diverse epipotamal fauna. Downstream from the Upper Volga Lakes, the functional feeding groups followed the predictions of the River Continuum Concept: in the upper reaches the community is composed of filter feeders, followed by grazers, predators, detritivores and shredders while further downstream detritivores became slightly dominant.