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Alpine Biology Center (CBA)

Research activity

During the past decades much scientific research in the Piora region has been achieved, mainly emanating from the Centre of Alpine Biology CBA. Many projects were financed by the Swiss National Science Foundation, especially the work of the microbiology groups of the Universities of Geneva and Zurich and the cantonal microbiology Institute Ticino.


The group for microbial ecology of the University of Geneva together with the cantonal microbiology Institute of the Ticino offers every year courses in microbial ecology and applied alpine microbiology for the master curriculum in natural and environmental sciences (MUSE). Similar courses are organized by the University of Zürich (Institutes of Plant Biology and Evolutionary Biology & Environmental Studies).


Microbial ecology and molecular characterization of microorganisms in water systems stratified


A central topic is the microbial ecology and the molecular characterization of the microorganisms in the stratified water and the sediments of Lake Cadagno and of the microbial mats in the Cadagno wetlands. It is a main focus of the cantonal microbiology Institute of the Ticino (ICM) in teaching and research, concentrating on the ecology of bacterial populations in the different layers in the water column and the sediments in the lake. The main goal is to analyze and characterize the enormous diversity of the bacterial populations and their distribution in space and time. This will be combined with the measurement of the physiological activities in the different compartments of the lake.

24-25 July 2010

On the national days of biodiversity, July 24th and 25th 2010, more than 50 scientists studied all aspects of biodiversity in the Piora Valley. The meeting was organized in cooperation with the Museum for Natural History (MCSN) and the Natural Science Society, both of the Canton Ticino.

 Present projects of the group for microbial ecology of the University of Geneva and the Institute for microbiology of the Canton Tessin


Interdisciplinary research with anoxic sediments of Lake Cadagno

This research will shine light into the history of the lake with previous landslides within the lake and the evolution of its microbial populations during time. DNA is extracted from subfossil samples from different layers of the anoxic sediments, quantified and partially sequenced. Different populations of phototrophic sulfur bacteria were detected all over the 10 m long sediment core equivalent of 10’000 years of lake history. Strong variation in the concentrations of different bacterial key species indicates important environmental changes during this time span.


The role of the phototrophic bacteria for the primary production of Lake Cadagno

The large mass of phototrophic bacteria at the chemocline increases the primary production in the lake and has a great impact on the food chain. With the strain Thiodictyon sp. Cad16, isolated from the chemocline of the lake, the ecological significance of the bacteria and its metabolism is studied


Formation of symbiotic bacterial aggregates

In the chemocline of the lake, at depths between 11 and 14 m, bacterial aggregates were observed consisting of two different species, red sulfur bacteria form the family of the Chromatiaceae (Thiodictyon sp.) and sulfur-reducing bacteria of the family of the Desulfovibrionaceae (Desulfocapsa thiozymogenes). This combination is species specific, but not mandatory; it stimulates growth for both species. Research will elucidate the chemical and physical environmental factors leading to aggregation and explain the 3-D structure of the aggregates and their physiological role.

Biogeochemical cycles in the lake

The knowledge gained on the different organisms in Lake Cadagno is broadened with studies on the biogeochemical cycles of the main elements, especially with sulfur and its species dominating the energy metabolism of the phototrophic bacteria. This allows a holistic approach to the complex processes in the aquatic system.

The band of dolomite present in the Piora Valley is well known from the media due to the technical problems expected during the construction of the transalpine tunnel NEAT. During the weathering process of dolomite different minerals become enriched in some waterbodies of the valley, especially carbonate, sulfate, calcium and magnesium. Mineral rich water is discharged from subsurface springs at the bottom of Lake Cadagno as well as in the wetlands nearby. For this reason two layers of different chemical composition and density are formed, the upper one between the surface and 11 m depth containing water of low salinity and high in oxygen, the from 11 m to the bottom (maximum depth 21 m) with water of high salinity and lacking oxygen.

At the boundary between oxic and anoxic conditions, the chemocline and moving between 10 and 13 m, the phototrophic sulfur bacteria find ideal conditions for growth: sufficient light, no oxygen but sulfide. These bacterial communities drive part of the sulfur cycle and boost the primary production in the lake. The chemocline stabilizes the stratification of the water and offers ideal growth conditions for phototrophic and chemoorganotrophic organisms.

This natural phenomenon of two rugged water layers is called krenogenic meromixis. In such a system the processes of biomass production and their mineralization take place in two different compartments. They can be studied in the lake independently. In the transition zone of up to 2 m width steep gradients of light, oxygen and sulfide are formed. The different bacterial populations with their activities are stacked; thus it became possible to sample the zone with high spatial resolution. In most other lakes we find the transition zone at the sediment surface and usually of only few mm in size which makes in situ experiments much more difficult.

Crenogenic meromixis in Lake Cadagno is a unique phenomenon in the Alps and worldwide rare. It is a natural environment of high biodiversity and may serve as model to investigate the role of microorganisms in the global element cycles. It is only since a few decades that the diversity of microorganisms can be studied on an ecological level by specific molecular methods.

Good scientific education is strongly coupled to research, as a consequence the ICM decided 1992 to recommence and stimulate microbiological research besides specific technical courses by focusing on ecology at Lake Cadagno. Besides the classical methods important for a comparison with earlier investigations, the new molecular and biophysical techniques allow a characterization of microbial communities with high specifity and resolution in space and time.

The amount of bacteria from environmental samples which can be cultivated in the lab is around 0.1%, thus fluorescence microscopy substituted classical enumeration already in the 1980ies. In cooperation with the Institute for Aquatic Ecosystems at Pallanza the bacteria were quantified and characterized according to morphotypes after staining of the nucleic acids (Dissertation Bensadoun). In 1994 in situ hybridization of whole cells was started in cooperation with the Institute for Terrestric Ecology of the ETH Zürich (D. Hahn) and the Technical University in Münich and the Max-Planck-Institute at Bremen (R. Amann).

From 1995 on molecular methods such as nucleic acid amplification (PCR) and sequencing of selected gene fragments (16S ribosomal DNA) allowed to characterize non cultivable bacteria. This facilitated to describe the microorganisms in Lake Cadagno in space and time. With specifically developed DNA probes new species of phototrophic and sulfate reducing bacteria were found in the oxic-anoxic transition zone. Temperature-gradient-.gel-electrophoresis (TGGE) and denaturing-gradient-gel-electrophoresis (DGGE) expanded the knowledge on the bacterial distribution in the different layers of the lake (Dissertations Bottinelli und Shahn).


In the mean time classical cultivation combined with metabolic studies gave important results on in situ metabolic activities and future developments for biotechnology, as the use of phototrophs for waste water purification or the degradation of pollutants such as by the halogen-organic organisms of the genus Desulfomonile. Several phototrophic bacteria (e.g. Lamprocystis) and sulfate reducing bacteria (e.g. Desulfocapsa) are presently available as pure cultures for physiological studies.

Besides phylogenetic aspects, the physiological interactions between and among different organisms and the environment gained special interest (syntrophy and symbiosis, dissertation S. Peduzzi). 

The key enzyme of the photosynthetic CO2 fixation, RubisCO, could be shown by Real Time PCR, opening new relations between the Sulfur and the carbon cycle.

The expert knowledge in microbial ecology gained in the studies on Lake Cadagno opened the way for similar work in other ecosystems, such as the limnologic description of Lake Muzzano combined with the isolation of the bloom forming cyanobacterium Microcystis wesenbergii and the characterization of the gene responsible for the synthesis of the toxin mycrocystin (Thesis at the University of Pavia).


In a PhD thesis at the University of Geneva the ecological and genetic impacts of the biological control of the undesirable mosquito Aedes vexans by the bacterium Bacillus thuringiensis sv. israelensis was studied in cooperation with the foundation of Bolle di Magadino and financed by the Federal Office for Environment, Forest and Landscape and the Canton Ticino.

Ecological projects of the University of Zürich (Institutes for Plant Biology, Systematic Botany, and Evolutionary Biology and Environmental Studies).


Field work in the Piora Valley started in 1983 with student courses by Kurt Hanselmann. At that time the scientific and the living infrastructures in the upper floor of the barn (building C) were marginal, sleeping on pallets, a latrine and running water at the fountain on the fore court. The cooperation „Zurich-Ticino“ in ecological field work started with two students from the Ticino, Claudio Del Don and Mauro Tonolla. Claudio created in his diploma thesis the first limnologic description of the lake (1986) and Mauro studied the vertical movements of the phototrophic bacteria in the transition layer (1987). This work formed the basis of many other investigations on the chemistry and biology of the lake and of the challenging analysis of the movements of the bacterial biomass in situ. It was further studied in the diploma thesis of Johanna Loch (1989) and of René Israng (1992) using electronic sensors and finalized in the diploma thesis of Konrad Egli (1997). Konstanze Mez (1992) and Barbara Känel (1992) enlarged in a collective thesis, unique for our University, the physiologic basis of the sulfur cycle. Franziska Gassmann (1988), Michaela Waldburger-Schlapp (1990) and Adriano Joss (1993) studied the fluorescence properties of the phototrophic bacterial community from the transition layer in the lab and in situ using a home made detection system. Markus Fritz (PhD thesis 1999) expanded the lake chemistry with analyses of volatile organic sulphur compounds. Lucas Lüthy (1999) succeeded for the first time to measure in situ the rates of oxidation and reduction of the essential compounds in the sulfur cycle within the bacterial layer in the transition zone.

Microbial processes in the sediments of Lake Cadagno were first studied by Helmut Brandl (1984) and Patrick Höhener (1986), and René Hutter (1989) explained the relations between the sulfur cycle and the iron cycle in the sediments. Christine Lehmann (PhD thesis 1999) used new approaches to quantify the reduction of sulphate in the sediments and Linda Birch (PhD thesis 1993) traced the input of pollutants from the atmosphere into the remote alpine lake by studying profiles of heavy metals in sediment cores.

Yvonne Weggler (1981) searched for different sulfureta ecosystems in Switzerland and came up with the bacterial mats in the wetlands of Cadagno (Bolle di fuori). Maja Ulmer Lazzaretti (1988) characterized these mats while Markus Wiggli (PhD thesis 1997) enlarged these studies by spectroscopic measurements. Barbara Rutishauser (1997) analyzed the reductive formation of phosphine in the wetlands and Thomas Horath (1998) isolated and characterized members of the phototrophic population in the bacterial mats. Astrid Schenk succeeded fort he first time to demonstrate bacterial signal compounds (homoserine lactones) in natural bacterial communities in the mats West of Cadagno (1998).


Guided by Ferdinand Schanz the diploma students Carmen Fischer-Romero (1989), Claudia Friedl (1987), Piero Pasini (1999) and Susanne Stalder (1990) investigated the photosynthetic production of the phototrophic bacterial layer and its specific light clima ithe lake.


Rolf Stettler, trained at the ETH, introduced the molecular techniques to analyze microbial ecosystems into the group; the diploma theses of Yves Santini (1998), Dominique Grüter (1999) and the PhD thesis of Philipp Bosshard (2000) illustrate well the microbial diversity in the different layers of Lake Cadagno.


Besides the work discussed on aquatic research, some studies covered terrestrial ecosystems. The PhD theses of Andreas Schürmann (1999) and of Joachim Mohn (1999) on the liberation of nitrous oxide from alpine soils gave evidence that soil releases much more N2O when covered with snow in winter than in summer. The PhD thesis of Thomas Horath (2010) illustrates a so far less regarded extreme ecosystem using physiological and molecular tools the endolithic microbes in the Dolomite in the Piora Valley.


A few diploma theses were accomplished at the Institute for Systematic Botany of the University of Zürich guided by Jakob Schneller on the topics biodiversity, population and reproduction biology of Polygonum viviparum (Martin Bauert, 1991), Anthyllis vulneraria (Karoline Haessig, 1993), Pulsatilla apiifolia (Evelyn Pelascini, 1993) und Euphrasia minima (Waldburga Liebst, 1999), furthermore the PhD theses von Martin Bauert (1994), Waldburga Liebst (2006) and Urs Landergott (2007).  In the group of Edwin Urmi the students Silvia Stofer (1995) and Ariel Bergamini (1995) completed the diploma work on the moss flora in relation to environmental factors in alpine regions.


At the Institute for Evolutionary Biology and Environmental Studies Sabine Ragot (2011) studied in the group of Helmut Brandl in an interdisciplinary approach with botanists and geologists die microbial populations on apatite and the solubilization of phosphate from rock material from the apatite band in the region of the Piatto della Miniera above Lake di Dentro.


From time to time also students from other universities carried out their research at the Centre of Alpine Biology, from the University of Konstanz Stefan Wagener (PhD thesis 1989) worked on protozoa in the lower anoxic water layer and Markus Fritz (1995) started his investigations on volatile sulfur compounds in the bottom water. Martine Uhde (1991) from the ETHZ/EAWAG and the University of Freiburg i.Br. examined the mixing processes in the lake using sulfur hexafluoride as tracer. Alexis Walter (2006) from the University of Neuenburg explored with new methods extensively the bacterial mats in the wetland of Bolle di fuori.

Centro Biologia Alpina, Piora

Via Mirasole 22a
CH-6500 Bellinzona


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Repubblica e Cantone Ticino Università di Zurigo Università di Ginevra Università della Svizzera Italiana



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