EAWAG news 54e (July 2002)
Alpine Streams (Entire volume)
Editorial (
en54e_editorial_s.pdf,
screen version 80 KB; en54e_editorial_p.pdf,
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Alexander J.B. Zehnder
Lead Article
The Ecology of Alpine Streams
(en54e_ward_s.pdf,
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James V. Ward
The raw beauty of the alpine life zone, present on all continents, has
long held the fascination of geographers and naturalists. Scientific work
in alpine tundra has focused on glaciology, hydrology, terrestrial ecology
and climatology, with surprisingly little previous research on stream ecology.
We initiated a comprehensive study of alpine stream ecology involving a year-round
sampling program. Our findings demonstrate much greater levels of environmental
heterogeneity than previously reported and document the major roles of floodplain
dynamics and groundwater aquifers in structuring habitat conditions. In glacial
streams, optimal conditions for biological activity occur during late autumn/early
winter.
Research Reports
Glacial Streams in Switzerland: A Dominant
Feature of Alpine Landscapes
(en54e_robinson_1_s.pdf,
screen version 340 KB; en54e_robinson_1_p.pdf,
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Christopher T. Robinson
Glacial streams are a predominant feature in Swiss Alpine landscapes.
Of the relatively few ecological investigations of glacial streams, most have
been conducted during summer and usually on only one system. As such, we wanted
to know how temporally and spatially variable glacial streams are by examining
a number of glacial streams in the Swiss Alps over an annual cycle. An important
finding was that glacial streams are more biologically dynamic in autumn/winter
than in summer.
Alpine Lake Outlets: Distinctive Alpine Stream
Types?
(en54e_hieber_s.pdf,
screen version 300 KB; en54e_hieber_p.pdf,
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Mäggi Hieber
Streams flowing from lakes represent unique aquatic environments inhabited
by both lake and stream organisms. In alpine areas, lake outlets can be of
either rhithral (snow-fed) or kryal (glacier-fed) origin. Although a prominent
feature of alpine environments, surprisingly little information exists on
the ecology of alpine lake outlets. We have found these distinctive freshwater
environments to differ substantially from lowland lake outlets and also from
other alpine streams.
Val Roseg: A Glacial Flood Plain in the Swiss
Alps
(en54e_uehlinger_s.pdf,
screen version 145 KB; en54e_uehlinger_p.pdf,
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Urs Uehlinger
The upper Val Roseg valley in the eastern Swiss Alps hosts a hydro-morphologically
diverse stream ecosystem that is strongly influenced by glacial runoff. The
distinctive geomorphic feature of the Roseg River corridor is a large glacial
flood plain that was subject to a comprehensive ecosystem study.
Habitat Dynamics in the Val Roseg Flood Plain
(en54e_tockner_s.pdf,
screen version 205 KB; en54e_tockner_p.pdf,
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Klement Tockner
Flood plains are among the most complex and dynamic but also one of the most
endangered ecosystems worldwide. They are characterized by a high level of
habitat heterogeneity and diverse biota adapted to this heterogeneity. In
the proglacial Val Roseg flood plain heterogeneity results from a diversity
of channel types and a pronounced expansion and contraction cycle of the entire
channel network.
Biodiversity in a Glacial Hyporheic Corridor
(en54e_malard_s.pdf,
screen version 110 KB; en54e_malard_p.pdf,
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Florian Malard
Despite the recognition of the hyporheic zone as a key component of stream
ecosystems, studies on the diversity and distribution of glacial stream invertebrates
have focused on the ecology of surface benthos. Due to the harsh environmental
conditions prevailing in the benthic layer, we expected the hyporheic zone
to contribute significantly to the diversity of invertebrate assemblages in
glacial streams. Recent investigations carried out in the hyporheic zone of
the Roseg River revealed the presence of a number of permanent aquatic taxa.
Our data suggest that the hyporheic zone acts as the main upstream migration
pathway and as a source area from which benthic habitats can be colonized.
Organic Matter Dynamics in Alpine Streams
(en54e_uehlinger_2_s.pdf,
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Urs Uehlinger
Benthic algae and organic matter of terrestrial origin provide the energy
base for consumers and microbial decomposers in streams. Both energy sources
are limited in the Val Roseg catchment, but studies on leaf litter decomposition
suggest that the streams' capacity to process organic matter is much greater
than currently realized.
Ecological Windows in Glacial Stream Ecosystems
(en54e_uehlinger_3_s.pdf,
screen version 165 KB; en54e_uehlinger_3_p.pdf,
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Urs Uehlinger
Alpine streams and in particular glacial streams are subject to harsh environmental
conditions during most of the year. However nutrient supply, light availability,
discharge, and temperature favor ecological processes and biota, during two
short periods at the beginning and end of the annual flow pulse.
Biodiversity of Zoobenthos in Alpine Streams:
The Val Roseg
(en54e_burgherr_s.pdf,
screen version 120 KB; en54e_burgherr_p.pdf,
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Peter Burgherr
Alpine glacial streams are common although highly sensitive features of high
mountain landscapes. We gaze at their raw and untamed nature in wonder, but
are little aware of the diverse and characteristic biota inhabiting these
harsh environments. However, the biodiversity of alpine streams is in danger
because of their particular sensitivity to climate change and the ever increasing
pressure stemming from human activities.
Habitat Fragmentation and Genetic Diversity
(en54e_monaghan_s.pdf,
screen version 310 KB; en54e_monaghan_p.pdf,
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Michael T. Monaghan
The fragmentation of natural habitats has important implications for the distribution
of organisms and the genetic structure of populations. For the past four years,
we have studied how fragmentation of alpine streams by lakes and reservoirs
affects the dispersal ability and the genetic structure of stream insects.
One of two mayfly species studied, Baetis alpinus, showed genetic differences
between fragmented populations. Adults are poor flyers and generally fly upstream
along the water course to lay eggs. The second mayfly, Rhithrogena loyolaea,
is a better flyer and disperses in all directions, suggesting it can cross
the unsuitable habitat between fragments. Interestingly, genetic differences
in B. alpinus were only detected across geologically old lakes suggesting
that human-caused habitat fragmentation may be too recent to detect genetic
effects.
Stream Response to Experimental Floods
(en54e_robinson_2_s.pdf,
screen version 280 KB; en54e_robinson_2_p.pdf,
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Christopher T. Robinson
Can artificial flooding restore the ecological integrity of rivers downstream
of reservoirs? Experimental flood releases from a large reservoir just outside
the Swiss National Park markedly altered the ecology of the receiving river.
The response of aquatic flora and fauna to flood disturbance reflected species-specific
life histories and the cumulative effects of earlier floods. Results indicate
that artificial flooding has great potential as a restoration strategy for
regulated rivers.
Forum
Limnological Research in the Swiss
National Park
(en54e_forum_s.pdf,
screen version 280 KB; en54e_forum_p.pdf,
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Thomas
Scheurer
Research has
been conducted in the Swiss National Park for over 80 years. Botanists and
zoologists have been particularly interested in this area because of minimal
human impact. It was not until the construction of hydroelectric power plants
on the Spöl, creating the Lago di Livigno, that limnologists appeared
on the scene. The current project is a "first" worldwide, where
artificial flood events are being used in an attempt to revitalize the Spöl.
The goal is to optimize the rest water regime and to restore the Spöl
to its original condition as closely as possible.
In brief
(en54e_inbrief_s.pdf,
screen version 120 KB; en54e_inbrief_p.pdf,
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Publications
Please feel free to submit questions or suggestions any time to the editor Martina Bauchrowitz.