DOCSLIB.ORG

Phytoplankton Configuration in Six Deep Lakes in the Peri-Alpine Region: Are the Key Drivers Related to Eutrophication and Climate?

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Phytoplankton Configuration in Six Deep Lakes in the Peri-Alpine Region: Are the Key Drivers Related to Eutrophication and Climate? Phytoplankton configuration in six deep lakes in the peri-Alpine region: are the key drivers related to eutrophication and climate? Nicole Gallina, Nico Salmaso, Giuseppe Morabito & Martin Beniston Aquatic Ecology A Multidisciplinary Journal Relating to Processes and Structures at Different Organizational Levels ISSN 1386-2588 Aquat Ecol DOI 10.1007/s10452-013-9433-4 1 23 Your article is protected by copyright and all rights are held exclusively by Springer Science +Business Media Dordrecht. This e-offprint is for personal use only and shall not be self- archived in electronic repositories. If you wish to self-archive your work, please use the accepted author’s version for posting to your own website or your institution’s repository. You may further deposit the accepted author’s version on a funder’s repository at a funder’s request, provided it is not made publicly available until 12 months after publication. 1 23 Author's personal copy Aquat Ecol DOI 10.1007/s10452-013-9433-4 Phytoplankton configuration in six deep lakes in the peri-Alpine region: are the key drivers related to eutrophication and climate? Nicole Gallina • Nico Salmaso • Giuseppe Morabito • Martin Beniston Received: 26 May 2012 / Accepted: 2 March 2013 Ó Springer Science+Business Media Dordrecht 2013 Abstract The aim of this study was to draw a water temperatures, variables that are strongly influ- general picture of the phytoplankton community in enced by climate change and eutrophication. Though peri-Alpine lakes, including for the first time a broad different phytoplankton configurations among lakes data set of six deep peri-Alpine lakes, belonging to the were partly due to their geographical (altitude) same geographical region. The objective was to define position, assemblages were mostly linked to temper- the main key drivers that influence the phytoplankton ature and nutrients. Furthermore, the results confirmed community composition in this particular vulnerable the significant role of the spring fertilization on the region, for which the impacts of climate change have seasonal phytoplankton development. Cyanobacteria been demonstrated to be stronger than on a global were related to the increasing annual average of air average. The phytoplankton was investigated with a and water temperature gradient and therefore might particular focus on cyanobacteria and using a classi- become more important under future warming sce- fication approach based on morpho-functional groups. nario. Air temperatures have a significant impact on We hypothesized that phytoplankton in peri-Alpine water temperature in the uppermost meters of the lakes is mainly driven by nutrient loads as well as by water column, with a stronger influence on warmer lakes. Handling Editor: Piet Spaak. Keywords Cyanobacteria Á Lake effect Á N. Gallina (&) Á M. Beniston Temperature Á Morpho-functional groups Á Climate Change and Climate Impacts, Institute of Phosphorus loads Á Global warming Environmental Science, University of Geneva, Campus Battelle, Building D, 7 Rte de Drize, 1227 Carouge, Switzerland e-mail: [email protected] Introduction N. Salmaso Physical, hydrodynamical, and ecological changes are Sustainable Agro-ecosystems and Bioresources occurring in lake ecosystems; these changes are Department, IASMA Research and Innovation Centre, Istituto Agrario di S. Michele all’Adige, Fondazione E. forecasted to become greater in the future as global Mach, Via E. Mach 1, 38010 S. Michele all’Adige, temperatures are increasing partly as a result of human Trento, Italy activities (IPCC 2007; Williamson et al. 2009; George 2010;). In the course of the twentieth century, the G. Morabito CNR, Istituto Studio Ecossistemi, Largo Tonolli 50, Alpine region has been shown to be particularly 28922 Verbania-Pallanza, VB, Italy vulnerable and sensitive to climate change (Beniston 123 Author's personal copy Aquat Ecol et al. 1997; Beniston 2006), with higher rate of their behavior, which is summarized by the broadly warming, at least double of the observed global accepted Plankton Ecology Group (PEG) model average. (Sommer et al. 1986). The PEG model identifies the The question of particular interest is to assess how main influencing factors of the seasonal behavior, such global warming may affect the phytoplankton com- as climate, weather, grazing, and water chemistry. munity composition, which plays an important role as Several studies debate the duality and the interaction it is the basis of nearly all aquatic ecosystems’ food between nutrients (mainly phosphorus) and tempera- supply (Arrigo 2005). Changes in the phytoplankton ture (reflecting climatological and meteorological community exert an effect on the higher food chain forcing) in affecting phytoplankton communities and can potentially disrupt the ecological equilibrium (Moss et al. 2003; Elliot et al. 2006; Stich and Brinker of lakes. Moreover, particular attention is paid to the 2011). Both these factors have been shown to consid- group of cyanobacteria, the only freshwater phyto- erably influence the seasonal phytoplankton commu- plankton group that not only forms blooms, but is also nity (Gallina et al. 2011; Salmaso et al. 2012). able to produce a variety of toxic compounds (Sivonen As several lakes are implicated, it is noteworthy and Jones 1999). Cyanobacteria thus can potentially that every lake is a mirror of its environment, and harm lake ecosystems through food web disturbance therefore, the phytoplankton community growth can and anoxia due to massive bloom events, affect human be presumed to differ in between lakes, as does the health (water supply, food contamination), the econ- water chemistry and environmental factors (Reynolds omy (fishing industry), and finally, social activities, as, and Walsby 1975; Lung and Paerl 1988; Ryding and for example, the recreational use of lakes. As the Rast 1989; Bleckner 2005). This phenomenon implies world’s oldest known organisms (Schopf 2000), that the hydro-morphometrical features, the surround- cyanobacteria have always been capable of adapting ing landscape, origin, and history of a lake may play an to environmental change (Huisman et al. 2005; Paul important role (Ryding and Rast 1989; Bleckner 2008). They have relatively high temperature optima 2005). Recent studies demonstrate different response for growth (Reynolds 2006) and are able to migrate of lakes to climate change (Bleckner 2005; George vertically in the water column to better compete for 2010). light and nutrients (Ibelings et al. 1991; Walsby et al. The underlying assumption is that phytoplankton 1997; Reynolds 2006). A number of studies have compositions among peri-Alpine lakes mainly repre- predicted that cyanobacteria are likely to become more sent different responses to nutrient concentrations and abundant in the future as climate continues warming temperature. These factors are strongly affected by the (Paerl and Huisman 2008; Paul 2008; Gallina et al. influence of climate change and eutrophication. In 2011; Paerl and Paul 2012). deep lakes, a further element to take into account is the The common phylogenetic classification of phyto- spring replenishment of nutrients from the deeper to plankton is based on taxonomy. However, since a the surface layer. We hypothesize that this pool could traditional taxonomy does only partially reflect the represent an important source of nutrients for phyto- ecological function of phytoplankton (Webb et al. plankton throughout the year. 2002; Litchman and Klausmeier 2008), other classi- After previous research based on a smaller number fications were proposed to aggregate species/genera of northern peri-Alpine lakes (cf. Anneville et al. having similar traits, for example, functional-based 2004, 2005), this study reports a synoptic assessment classifications (Reynolds et al. 2002), the morpho- of phytoplankton assemblages and their main driving functional-based classification (Salmaso and Padisa`k factors across six peri-Alpine lakes situated north and 2007), and the morphological-based classification south of the alpine chain. The main key drivers of (Kruk et al. 2010). These aggregations have the phytoplankton composition changes will be evaluated advantages to better interpret environmental mecha- on yearly and seasonal timescales (summer–autumn). nisms and conditions and are easier to deduce as they A matrix including eight different data sets generated enclose common affinities and considerably reduce from six lakes (two of the lakes were sampled at two the numbers of interpreting components. different locations) was compiled. For reasons of In deep lakes under a continental climate, phyto- comparability, the six lakes are all deep and warm plankton communities exhibit strong seasonality in monomictic lakes, situated in the same geographical 123 Author's personal copy Aquat Ecol region. Additionally, these lakes have the interesting namely Lake Constance, Lake Zu¨rich, Lake Walen, features to cover a large trophic gradient and to be Lake Geneva, Lake Maggiore, and Lake Garda. Data located along an altitudinal gradient. from Lake Geneva and Lake Zu¨rich were collected at two sampling points, named as ‘‘Small Lake Geneva’’ and ‘‘Big Lake Geneva,’’ as well as ‘‘Upper Lake Materials and methods Zu¨rich’’ and ‘‘Lower Lake Zu¨rich,’’ respectively. Consequently, eight data sets were derived from the Lake characteristics and data sources six lakes. The six lakes have a number of features in common: Figure 1 a shows the locations of the lakes. The matrix They are all deep, warm monomictic lakes (Hutch- includes
Load more

Recommended publications
  • Around the Lake Constance in One Week Arrival
    Around the Lake Constance in one week Individual tour Category: bike tour Duration: 7 days Offer: 2021 Meals: breakfasts Accommodation: hotels and pensions, rooms with bathrooms Difficulty: easy Distance by bike: 230 - 250 km The tour around Lake Constance is one of cycling classics. It is among the biggest lakes of Central Europe, along the Balaton and Lake Geneva. It is located at the border of Switzerland, Germany and Austria. At the same time, it is a very interestingly located one, surrounded by the Alpine mountains, allowing to observe many peaks, and numerous castles if the weather allows. The lake is encircled by a cycling route, making the trip a safe and comfortable one. Due to minor elevations we recommend the tour even for beginners and families with children. Arrival: By plane – the easiest way is coming by plane to Friedrichshafen, Stuttgart or Zurich. Most flights can be booked to Zurich, often at a reasonable price. From there, one should take a train to Constance. Places to see: Constance Over 600 years ago, the ecumenical council ending the Western schism took place in Constande. During the council, pope Martin V was elected, and the Czech reformer Jan Hus was burned at the stake at the same time. The statue of Imperia by Peter Lenk commemorates these events. Erected in 1993, weighing over 18 tons and 9 meters tall is one of the city’s symbols. It resembles a courtesan with her hands risen up, holding two naked men. One of them is wearing a crown and holds a sphere – the symbol of Holy Roman Empire.
    [Show full text]
  • The Periodicity of Phytoplankton in Lake Constance (Bodensee) in Comparison to Other Deep Lakes of Central Europe
    Hydrobiologia 138: 1-7, (1986). 1 © Dr W. Junk Publishers, Dordrecht - Printed in the Netherlands. The periodicity of phytoplankton in Lake Constance (Bodensee) in comparison to other deep lakes of central Europe Ulrich Sommer University of Constance, Institute of Limnology, PO. Box 5560, D-7750 Constance, FRG New address: Max Planck Institute of Limnology, PO. Box 165, D-2320 Plon, FRG Keywords: phytoplankton succession, inter-lake comparison, oligotrophic-eutrophic gradient, central Eu- ropean lakes Abstract Phytoplankton periodicity has been fairly regular during the years 1979 to 1982 in Lake Constance. Algal mass growth starts with the vernal onset of stratification; Cryptophyceae and small centric diatoms are the dominant algae of the spring bloom. In June grazing by zooplankton leads to a 'clear-water phase' dominated by Cryptophyceae. Algal summer growth starts under nutrient-saturated conditions with a dominance of Cryptomonas spp. and Pandorinamorum. Depletion of soluble reactive phosphorus is followed by a domi- nance of pennate and filamentous centric diatoms, which are replaced by Ceratium hirundinella when dis- solved silicate becomes depleted. Under calm conditions there is a diverse late-summer plankton dominated by Cyanophyceae and Dinobryon spp.; more turbulent conditions and silicon resupply enable a second sum- mer diatom growth phase in August. The autumnal development leads from a Mougeotia - desmid assem- blage to a diatom plankton in late autumn and winter. Inter-lake comparison of algal seasonality includes in ascending order of P-richness K6nigsee, Attersee, Walensee, Lake Lucerne, Lago Maggiore, Ammersee, Lake Ziirich, Lake Geneva, Lake Constance. The oligo- trophic lakes have one or two annual maxima of biomass; after the vernal maximum there is a slowly develop- ing summer depression and sometimes a second maximum in autumn.
    [Show full text]
  • Subaqueous Morphology of Lake Lucerne (Central Switzerland): Implications for Mass Movements and Glacial History
    Swiss J Geosci (2011) 104:425–443 DOI 10.1007/s00015-011-0083-z Subaqueous morphology of Lake Lucerne (Central Switzerland): implications for mass movements and glacial history Michael Hilbe • Flavio S. Anselmetti • Raymond S. Eilertsen • Louise Hansen • Walter Wildi Received: 1 October 2010 / Accepted: 3 August 2011 / Published online: 25 November 2011 Ó Swiss Geological Society 2011 Abstract Bathymetric data available for Swiss lakes have document mass-movement activity on steep slopes above typically only low to moderate resolution and variable the lake. Six transverse moraines, visible as subaqueous quality, making them insufficient for detailed underwater ridges, as lake-floor lineaments, or only imaged on reflec- geomorphological studies. This article presents results of a tion seismic profiles, indicate a complex glacial-inherited new bathymetric survey in perialpine Lake Lucerne using morphology. As many of the documented features result modern hydrographic equipment. A digital terrain model from potentially catastrophic events, high-resolution (DTM) of the lake floor (raster dataset with 1 m cell size) bathymetry can significantly improve natural hazard covering the Chru¨ztrichter and Vitznau basins documents assessment for lakeshore communities by extending clas- signatures of major Holocene mass movements and relics sical hazard maps to the subaqueous domain. from the glacial history of the lake. Combining the bathymetry data with reflection seismic profiles and an Keywords Swath bathymetry Á Perialpine lakes Á existing event chronology allows investigating the mor- Natural hazards Á Subaqueous moraines Á phology in its geological context. Subaqueous sediment Soft-sediment deformation slide scars with sharp headwalls cover large areas on moderately inclined slopes. The particularly large Weggis slide complex, correlated with an historical earthquake (AD 1 Introduction 1601), features a *9 km long and 4–7 m high headwall and covers an area of several square kilometers.
    [Show full text]
  • Mediators of Synchrony in Phytoplankton Changes Among European Peri-Alpine Lakes
    Freshwater Biology (2005) 50, 1731–1746 doi:10.1111/j.1365-2427.2005.01429.x Phosphorus decrease and climate variability: mediators of synchrony in phytoplankton changes among European peri-alpine lakes ORLANE ANNEVILLE,*,† SONJA GAMMETER‡ AND DIETMAR STRAILE† *INRA, Station d’hydrobiologie lacustre, Thonon les Bains, Cedex, France †Limnologisches Institut, Universita¨t Konstanz, Konstanz, Germany ‡Zurich Water Supply, Postfach, Zu¨rich, Switzerland SUMMARY 1. In an attempt to discern long-term regional patterns in phytoplankton community composition we analysed data from five deep peri-alpine lake basins that have been included in long-term monitoring programmes since the beginning of the 1970s. Local management measures have led to synchronous declines in phosphorus concentrations by more than 50% in all four lakes. Their trophic state now ranges from mesotrophic to oligotrophic. 2. No coherence in phytoplankton biomass was observed among lakes, or any significant decrease in response to phosphorus (P)-reduction (oligotrophication), except in Lakes Constance and Walen. 3. Multivariate analyses identified long-term changes in phytoplankton composition, which occurred coherently in all lakes despite the differing absolute phosphorus concentrations. 4. In all lakes, the phytoplankton species benefiting from oligotrophication included mixotrophic species and/or species indicative of oligo-mesotrophic conditions. 5. A major change in community composition occurred in all lakes at the end of the 1980s. During this period there was also a major shift in climatic conditions during winter and early spring, suggesting an impact of climatic factors. 6. Our results provide evidence that synchronous long-term changes in geographically separated phytoplankton communities may occur even when overall biomass changes are not synchronous.
    [Show full text]
  • P4.14 Validation of Lake Surface Water Temperatures Derived from Noaa Avhrr and Modis Data
    P4.14 VALIDATION OF LAKE SURFACE WATER TEMPERATURES DERIVED FROM NOAA AVHRR AND MODIS DATA D. Oesch *, A. Hauser and S. Wunderle Remote Sensing Research Group, University of Bern, Switzerland 1. INTRODUCTION* Approximately 4000 HRPT AVHRR data sets from Numerous lakes in the European Alps contain a AVHRR/2 (N12) and AVHRR/3 (N15, N16, and N17) have sufficient large volume and areal extent of water to been read out at the receiving station of the University of influence significantly local weather patterns with their Bern during 2002 and 2003. The level1b data were radi- surface temperature (Livingstone et al., 2001). ometrically corrected and calibrated in physical units, ac- Monitoring of climatological temperature conditions counting for sensor nonlinearity of the AVHRR/2 as sug- and temporal and spatial distribution of the lake gested by Rao et al., 1993. To derive LSWT from lakes surface water temperature (LSWT) can be valuable with a size of a few square kilometers, a georeferencing for many applications (Alsdorf et al., 2003). with sub pixel accuracy is necessary. This was achieved Up to now, there is no area wide consistent through an automated feature matching algorithm. An or- temperature data set for the alpine lakes available. thorectification based on the terrain model GTOPO30 of The in situ measurements at points of opportunity can the imagery is essential in a mountainous area to over- not take into account the high spatial variability of come the displacement introduced by the topography. The water in near shore zones and their limited spatial resulting data set was subset to a latitude – longitude grid coverage is not adequate for resolving the spatial on the WGS84 ellipsoid, covering the alpine region from distribution of temperature in lakes.
    [Show full text]
  • Article (Published Version)
    Article Local to regional scale industrial heavy metal pollution recorded in sediments of large freshwater lakes in central Europe (lakes Geneva and Lucerne) over the last centuries THEVENON, Florian, et al. Reference THEVENON, Florian, et al. Local to regional scale industrial heavy metal pollution recorded in sediments of large freshwater lakes in central Europe (lakes Geneva and Lucerne) over the last centuries. Science of the Total Environment, 2011, vol. 412-413, p. 239-247 DOI : 10.1016/j.scitotenv.2011.09.025 Available at: http://archive-ouverte.unige.ch/unige:17728 Disclaimer: layout of this document may differ from the published version. 1 / 1 This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier’s archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright Author's personal copy Science of the Total Environment 412-413 (2011) 239–247 Contents lists available at SciVerse ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv Local to regional scale industrial heavy metal pollution recorded in sediments of large freshwater lakes in central Europe (lakes Geneva and Lucerne) over the last centuries Florian Thevenon a,⁎, Neil D.
    [Show full text]
  • ESPON ACTAREA Swiss Spatial Strategy and Action Areas
    This targeted analysis is conducted within the framework of the ESPON 2020 Cooperation Programme, partly financed by the European Regional Development Fund. The ESPON EGTC is the Single Beneficiary of the ESPON 2020 Cooperation Programme. The Single Operation within the programme is implemented by the ESPON EGTC and co-financed by the European Regional Development Fund, the EU Member States and the Partner States, Iceland, Liechtenstein, Norway and Switzerland. This delivery does not necessarily reflect the opinion of the members of the ESPON 2020 Monitoring Committee. Authors Erik Gløersen, Nathalie Wergles, Clément Corbineau and Sebastian Hans, Spatial Foresight (Luxembourg) Tobias Chilla and Franziska Sielker, Friedrich-Alexander University of Erlangen-Nuremberg (Germany) Jacques Félix Michelet and Lauranne Jacob, University of Geneva, Hub of Environmental Governance and Territorial Development (GEDT) (Switzerland)) Advisory Group Project Support Team: ESPON EGTC: Sandra di Biaggio Acknowledgements The authors would like to thank to Steering group composed of the Swiss Federal Office for Spatial Development (ARE), the German Federal Ministry of Transport and Digital Infrastructure and the International Spatial Development Commission "Bodensee” (Lake Constance) for the stimulating dialogue throughout the duration of the project. Stakeholders of case study areas and survey respondents have also provided precious inputs, without which the present report could not have been produced. Information on ESPON and its projects can be found on www.espon.eu. The web site provides the possibility to download and examine the most recent documents produced by finalised and ongoing ESPON projects. This delivery exists only in an electronic version. © ESPON, 2017 Printing, reproduction or quotation is authorised provided the source is acknowledged and a copy is forwarded to the ESPON EGTC in Luxembourg.
    [Show full text]
  • Morphology and Recent History of the Rhone River Delta in Lake Geneva (Switzerland)
    Swiss J Geosci (2010) 103:33–42 DOI 10.1007/s00015-010-0006-4 Morphology and recent history of the Rhone River Delta in Lake Geneva (Switzerland) Vincent Sastre • Jean-Luc Loizeau • Jens Greinert • Lieven Naudts • Philippe Arpagaus • Flavio Anselmetti • Walter Wildi Received: 12 January 2009 / Accepted: 29 January 2010 / Published online: 28 May 2010 Ó Swiss Geological Society 2010 Abstract The current topographic maps of the Rhone shoulders. Ripples or dune-like morphologies wrinkle the Delta—and of Lake Geneva in general—are mainly based canyon bottoms and some slope areas. Subaquatic mass on hydrographic data that were acquired during the time of movements are apparently missing on the delta and are of F.-A. Forel at the end of the nineteenth century. In this minor importance on the lateral lake slopes. Morphologies paper we present results of a new bathymetric survey, of the underlying bedrock and small local river deltas are based on single- and multi-beam echosounder data. The located along the lateral slopes of Lake Geneva. Based on new data, presented as a digital terrain model, show a well- historical maps, the recent history of the Rhone River structured lake bottom morphology, reflecting depositional connection to the sub-aquatic delta and the canyons is and erosional processes that shape the lake floor. As a reconstructed. The transition from three to two river major geomorphologic element, the sub-aquatic Rhone branches dates to 1830–1840, when the river branch to the Delta extends from the coastal platform to the depositional Le Bouveret lake bay was cut. The transition from two to fans of the central plain of the lake at 310 m depth.
    [Show full text]
  • The Best Location Surrounded by the Borders
    The best location surrounded by the borders Austria, Germany, Switzerland and Liechtenstein Water and mountains are the borders. To the north, Lake Constance. In the west, towards Switzerland and Liechtenstein. In the south and east are the Alps. It is an open minded, modern region. A very lively business and culture area. With an eye for beauty and aesthetic. Once where the inhabitants earned their living mainly by designing and producing embroideries and material. The magnificent villas of the "Textile barons" in Dornbirn are witnesses to that time of prosperity. Today´s designers, like Wolford, who produce exclusive body wear or innovative lighting systems like that from “Zumtobel Staff”, and the European centre for modern architecture have all made the area their home base. The landscape on the lake inspires poets and thinkers, artists and athletes, inhabitants and guests. A treat for both the eyes and ears: The Bregenz Festival with their spectacular productions on the largest water stage in the world. The art Bodensee in Dornbirn is the largest art fair in the area. The traditional bon fires which chase away the winter and bring carnival to an end. Jazz concerts, cabaret, small theatres - they are all here. Museums, exhibitions. There are many indoor and outdoor activities to keep you busy. The best location surrounded by the borders Bregenz Bregenz is Austria's culture and relaxation capital at Lake Constance, the capital of Vorarlberg, seat of the regional government, 27,000 inhabitants. Situated in the border region between Germany, Austria, Switzerland and Liechtenstein Bregenz has to offer a lot, in every season of the year.
    [Show full text]
  • Summertime Winds and Direct Cyclonic Circulation: Observations from Lake Geneva
    Ann. Geophysicae 14, 1207Ð1220 (1996) ( EGS Ð Springer-Verlag 1996 Summertime winds and direct cyclonic circulation: observations from Lake Geneva U. Lemmin, N. D’Adamo1 Laboratoire de recherches hydrauliques, Ecole Polytechnique Fe«de«rale de Lausanne, CH-1015 Lausanne, Switzerland Received: 11 March 1996/Revised 7 June 1996/Accepted: 14 June 1996 Abstract. Records of wind, air temperature and air pres- been the subject of many limnological studies since, both sure from nine stations, situated along the shoreline of in the field (Mortimer, 1974; Fischer et al., 1979; Imberger Lake Geneva, Switzerland, were analyzed for the summer and Hamblin, 1982) and in the laboratory (Monismith, period May to September. At all stations the consistent 1983). Accurate knowledge of the strength and the spatial appearance of significant spectral peaks and changes and temporal distribution of winds is needed as input into in wind direction at the diurnal frequency indicates the numerical lake models. The assumption of a constant importance of lake-land breezes. It is shown that the wind stress is only rarely justified (Simons, 1980). As surrounding topography has a strong modifying e¤ect Mortimer (1979, p. 214) pointed out, ‘‘Wind stress and its (temporal and spatial) on the lake-land breeze. Superim- horizontal distribution over the whole water surface is the posed on this cyclic wind pattern, short episodes of strong critical variable and is usually the least well defined.’’ winds with long fetch over parts of Lake Geneva are It is recognized that the kinetic energy introduced at regularly observed. Both of these winds exert a spatially the water surface by way of wind shear stress is of prime variable wind stress over the lake surface on the same time importance in mixing the water vertically, accelerating the scale.
    [Show full text]
  • Lake Shore Deterioration, Reed Management and Bank Restoration in Some Central European Lakes *
    ECOLOGICAL ENGINEERING ELSEVIER Ecological Engineering 5 (1995) 51-75 Lake shore deterioration, reed management and bank restoration in some Central European lakes * Wolfgang Ostendorp a,., Christoph Iseli b, Manfred Krauss c, Priska Krumscheid-Plankert d, Jean-Louis Moret e, Maurice Rollier , Ferdinand Schanz g a Limnologisches fnstitut der Universitiit Konstanz, Postfach 5560, D-78434 Konstanz, Germany b Th. Kocher Str. 7, CH-2502 Biel / Bienne, Switzerland c Schlof3strafJe 22, D-14059 Berlin 19, Germany d Limnologisches fnstitut der Universitiit Konstanz, Postfach 5560, D-78434 Konstanz, Germany C Musee et Jardins Votaniques Cantonaus, Avenue de Cour 14bis, CH-f007 Lausanne, Switzerland f Groupe d'etude et de gestion, Champ Pittet, CH-1400 Cheseaux-Noreaz, Switzerland g Hydrobiologisch-Limnologische Station der Universitiit Zurich, Seestraf3e 187, CH-8802 Kilchberg, Switzerland Abstract The causes of lakeshore deterioration and reed decline are concisely summarised, and demonstrated with examples of seven Central European lakes (Germany: Havellakes, Lake Constance-Untersee, Lake Constance-Obersee; Switzerland: Lake Zurich, Lake Biel, Lake Neuchiitel, Lake Geneva). The main causes are assumed to be bank erosion, lake eutrophi­ cation, mechanical damage to the reeds, and recreational activities. Countermeasures can be grouped into: reed protection against mechanical load (fences), wave dissipative con­ structions (refilling of substrate, brushwood fascine), nutrient export from the reeds (winter mowing), and supplementary measures (reed plantations, prohibition of access for the public). Favourable issues and undesired results are discussed. It is stated that there is a need for fundamental research and scientific surveillance of the restoration measures to avoid ill effects in the future. Keywords: Phragmites australis; Bank erosion; Reed die-back; Winter mowing of reeds; Reedswamp; Restoration ~ Parts of this paper have been presented at the IV International INTECOL Wetlands Conference, Columbus, Ohio, USA, 13-18 September, 1992.
    [Show full text]
  • Multinational Companies in Geneva and Vaud Growth Engine at Risk! —
    Multinational Companies in Geneva and Vaud — Growth Engine at Risk! Joint Study of The Swiss-American Chamber of Commerce and The Boston Consulting Group June 2012 · Geneva, Switzerland NOTE TO THE READER This study picks up from where we left off three years ago, when we examined (in the course of three studies) the relationship between multinational companies (MNCs) and Switzerland. Our first study, Foreign Companies in Switzerland: The Forgotten Sector (2006), introduced foreign companies as a small but fast-growing sector within the Swiss economy. Our second study, Multinational Companies on the Move: How Switzerland Will Win the Battle! (2007), explained Switzerland's success in attracting MNCs while illustrating the vulnerability of the Swiss economy to MNCs should they relocate elsewhere. Our third study, Creative Switzerland? Fostering an Innovation Powerhouse! (2009), investigated how Switzerland could increase its attractiveness to MNCs by sustaining its position as the best place for innovation. In this study, we focus on Geneva and Vaud, cantons that have two of the strongest economies in Switzerland, in order to illustrate the mutually beneficial relation- ship between MNCs and Switzerland and the high stakes involved in this relation- ship. Geneva and Vaud (and the surrounding area, known as the "Lake Geneva region") have provided an advantageous environment for MNCs, thanks to, among other things, their good quality of life, highly skilled workforce and focus on innovation. MNCs represent a vital part of these cantons' economies, contributing over 40 percent of GDP in 2010 (more than the 36 percent MNCs contributed to total Swiss GDP). MNCs are not only the growth engine of wealth and employment, they also contribute significantly to the local knowledge economy and their communities.
    [Show full text]