Partner und Internationale Organisationen
(Englisch)
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Uni.Oslo (N), Uni. Birmingham (UK), Uni. of
Iceland, Uni. GenËve (CH), museo Tridentino di Scienza Naturali
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Abstract
(Englisch)
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General objectives of the project:
- to model the sensitivity of arctic, alpine and montane stream ecrosystems
across Europe to environmental change
- to isolate the primary physical variables that determine aquatic
macroinvertebrate distributions in such ecosystems
- to develop the use of aquatic macroinvertebrates as a predictive tool for sustainable management of arctic and alpine ecosystems.
Objective of the Swiss pa rtner: to implement the protocoles set up for all partners (landscape,
physico-chemical and biological protocoles) on the Swiss site: the Mutt
catchment (Valais).
Main results of the project: Most aspects of the AASER physico-chemical and biological protocols were carried out in 1996 and 1997 during three field seasons (end of June, beginning of August and mid-September). Relatively high levels of winter snowfall preceded the beginning of the two June field
seasons. This restricted fieldwork, especially in the uppermost sites. This two-year field study of the glacier-fed River revealed an abundant and diversified macroinvertebrate fauna. Among the 72 taxa recorded, some insect groups proved to be especially diversified (28 Diptera Chironomidae, 13 Plecoptera, 12 Trichoptera). For some of them (Chironomidae, Trichoptera Limnephilidae), some taxa could not be identified to species level, due tothe absence of larval descriptions, and to the general low level of knowledge of these faunas. The uppermost sites, near the glacier snout, were clearly dominated by chironomids. Their density and specific richness decreased downstream. Close to the snout, only the genus Diamesa was found in very low number (23 ind/10 kicks in 1996, 5 in 1997). From site 2 onwards, they were joined by other Diamesinae, Orthocladiinae, other Diptera, Ephemeroptera, Plecoptera and Trichoptera.
The total density of invertebrates was generally higher in 1996 and for the two years in September, except for the uppermost sites on the glacial stream. The highest value was found at site 4 in 1996 with approximately 9'900 ind/m2. Multivariate statistical methods were used i) to describe patterns of between-site variations in macroinvertebrate composition, ii) to explore relationships between environmental parameters describing geomorphology, stability and hydrology at the sites, iii) to relate patterns of faunal variation to selected environmental variables. The taxonomic composition of the macrobenthic assemblages appeared relatively well explained (as perceived by CANOCO analysis) by
environmental variables describing site stability (Pfankuch index, slope, water depth), supplemented by water temperature, velocity and electrical conductivity. In this respect, the results substantiate Milner & Petts' model of community succession.
Departures from Milner & Pettsí model appeared in the form of i) richer communities developing 'earlier' than expected, i.e. closer from the glacier snout, especially with Plecoptera (Taeniopterygidae), and Trichoptera (Drusinae), and ii) few taxa, like Simuliidae, developing 'later' than expected.
Although limited to short time slots during two consecutive years, the study provided evidences for slight local inter-annual faunal fluctuations. They were manifested in the form of longitudinal shifts in the distribution of some taxa between comparable seasons of the two years. These shifts resulted in noticeable local differences in taxonomic richness for a site. This preliminary observation could be interpreted as a sign of the 'sensitivity' of such ecosystems and as a call for a longer term monitoring
of selected sites along glacial streams.
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