AlpWISE : ALPine Water, Ice, Sediment and Ecology

Deltas are important coastal sediment accumulation zones in both marine and lacustrine settings. However, currents derived from tides, waves or rivers can transfer that sediment into distal, deep environments, connecting terrestrial and deep marine depozones. The sediment transfer system of the Rhone River in Lake Geneva is composed of a sublacustrine delta, a deeply incised canyon and a distal lobe, which resembles, at a smaller scale, deep?sea fan systems fed by high discharge rivers. From the comparison of two bathymetric datasets, collected in 1891 and 2014, a sediment budget was calculated for eastern Lake Geneva, based on which sediment distribution patterns were defined. During the past 125 years, sediment deposition occurred mostly in three high sedimentation rate areas: the proximal delta front, the canyon?levée system and the distal lobe. Mean sedimentation rates in these areas vary from 0·0246 m year?1 (distal lobe) to 0·0737 m year?1 (delta front). Although the delta front–levées–distal lobe complex only comprises 17·0% of the analysed area, it stored 74·9% of the total deposited sediment. Results show that 52·5% of the total sediment stored in this complex was transported toward distal locations through the sublacustrine canyon. Namely, the canyon–levée complex stored 15·9% of the total sediment, while 36·6% was deposited in the distal lobe. The results thus show that in deltaic systems where density currents can occur regularly, a significant proportion of riverine sediment input may be transferred to the canyon?lobe systems leading to important distal sediment accumulation zones.

The paper has been published in Sedimentology and can be accessed here.

In Alpine streams, humans have strongly modified the interactions between hydraulic processes, geomorphology and aquatic life through dams, flow abstraction at water intakes and river channel engineering. To mitigate these impacts, research has addressed both minimum flows and flow variability to sustain aquatic ecosystems. Whilst such environmental flows might work downstream of dams, this may not be the case for water intakes. Intakes, generally much smaller than dams, are designed to abstract water and to leave sediment behind. Sediment accumulation then results in the need to flush intakes periodically, often more frequently than daily in some highly glaciated basins. Sediment delivery downstream is then maintained through short duration floods with very high sediment loads. Here we tested the hypothesis that sediment flushing, and the associated high frequency of bed disturbance, controls in-stream habitat and macroinvertebrate assemblages. We collected macroinvertebrates over a 17-month period from an Alpine stream as well as a set of lateral unperturbed tributaries that served as controls. In contrast to established conceptual models, our results showed that the stream is largely void of life during summer, but that populations recover rapidly as the frequency of intake flushing falls in early autumn, producing richer and larger populations in winter and early spring. The recovery in autumn may be due to the recruitment of individuals from tributaries. We conclude that intake flushing in summer inverts expected summer-winter macroinvertebrate abundances, and questions the extent to which environmental flows in intake-impacted Alpine streams will lead to improvements in instream macrofauna unless sediment also is managed.

The paper can be accessed here (or email stuart.lane@unil.ch for a copy): https://www.sciencedirect.com/science/article/pii/S0048969718336246

Stuart Lane will serve on the Swiss National Science Foundation Research Council from the 1st January 2019, representing environmental science in the Division 4 (programmes)

Congratulations to Annegret Larsen who has been appointed to a Lectureship in Catchment Science at the University of Manchester, UK, from the 1st September 2018.

Congratulations to Chrystelle Gabbud who has been appointed environmental manager with Alpiq SA from 1 August 2018.

The group is part of a consortium led by Tom Battin at EPFL who has received four years of funding to study microbial biofilms and their implications for habitability and ecosystem evolution in glacial floodplain streams. Abbreviated to “ENSEMBLE” the focus of the project is how, in the presence of rapidly retreating glaciers, microbial biofilms respond and in turn impact the ecosystem evolution of glacial-floodplain systems. We will work at the interface of microbial ecology, vegetation ecology, hydrology and geomorphology to address the following questions:

(i) What are the ecological strategies and genomic underpinnings of biofilms that make them successful in colonizers in GFSs that emanate from glacier shrinkage?

(ii) Do microbial biofilms change, through ecosystem engineering, the geomorphodynamics of GFSs thereby increasing their habitability?

(iii) Does the interaction between microbial and geomorphic processes affect ecosystem heterogeneity in glacier floodplains?

We will be working primarily at the Otemma glacier in the Val de Bagnes (VS), but also the Rosengletscher (GR) and Zinal glacier, Val d’Anniviers (VS).

A new book, the Handbook of Critical Physical Geography, has been published by Stuart Lane, with colleagues Rebecca Lave and Christine Bierman.

Congratulations to Maarten Bakker who has been awarded an SNSF Early Post Doc Mobility grant to work at Grenoble Alpes University, France.

Welcome to our new AlpWISE web- site. It is not finished yet with more projects to come, as well as publications and presentations.

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