Waterfowl, macrophytes, and the clear water state of shallow lakes
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The importance of lake ecosystems for waterfowl remains a topic of debate. In order to assess how temporal variations in lake features, specifically shifts between alternative stable states, may interact with the waterfowl fauna, we performed a long-term (22 years) study of the shallow Lake Krankesjön, southern Sweden. Lower total numbers of waterfowl occurred during periods with low macrophyte cover and turbid water, than when submersed macrophytes flourished and the water was clear. Some specific functional groups of waterfowl, such as herbivores, invertebrate, and fish feeders, showed a positive relation to clear water and high macrophyte cover. Hence, our data suggest that some migratory waterfowl may select lakes based on water quality, thereby adjusting their large-scale migratory routes. On the other hand, omnivorous waterfowl exhibited their highest abundances during turbid conditions. Furthermore, waterfowl not primarily relying on food from the lake showed no response to fluctuations in turbidity or macrophyte cover, but followed regional trends in population dynamics. In our study lake, L. Krankesjön, we estimated that waterfowl remove less than 3% of the macrophyte biomass during a stable clear-water state with lush macrophyte beds. However, during transition periods between alternative stable states, when macrophyte biomass is lower and the plants already stressed, the consumption rate of waterfowl may have a stronger effect on lake ecosystem functioning.
KeywordsWaterfowl Bird Alternative stable state Lake Macrophyte Herbivory Grazing
This study was partly funded by grants from the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (FORMAS), the Swedish Research Council (VR), and the Linné Grant on animal migration (“CAnMove”; VR). The Swedish Bird Survey is supported by grants from the Monitoring Programme of the Swedish Environmental Protection Board. We are most grateful to the hundreds of volunteers who performed the census of the birds within The Swedish Bird Survey. We also thank Irmgard Blindow and Hans Källander for providing valuable input to this study, and Romi Burks for thorough editing of the manuscript.
- Berglund, B., K. Curry-Lindahl, H. Luther, V. Olsson, W. Rodhe & G. Sellerberg, 1963. Ecological studies on the Mute swan (Cygnus olor) in southern Sweden. Acta vertebratica 2: 167–188.Google Scholar
- Brönmark C., J. Brodersen, B. Chapman, A. Nicolle, A. P. Nilsson, C. Skov & L.-A. Hansson, 2009. The importance of seasonal fish migration for the dynamics of shallow lake ecosystems. Hydrobiologia. doi: 10.1007/s10750-010-0165-3.
- Chaichana, R., B. Moss & R. T. Leah, 2009. Effects of water birds on aquatic vegetation in a shallow lake. Verhandlungen der Internationalen Vereinigung fur Theoretische und Angewandte Limnologie 30: 741–744.Google Scholar
- Hansson, L.-A., H. Annadotter, E. Bergman, S. F. Hamrin, E. Jeppesen, T. Kairesalo, E. Luokkanen, P.-Å. Nilsson, M. Søndergaard & J. A. Strand, 1998. Biomanipulation as an application of food chain theory: constraints, synthesis and recommendations for temperate lakes. Ecosystems 1: 558–574.CrossRefGoogle Scholar
- Hansson, L.-A., A. Nicolle, J. Brodersen, P. Romare, C. Skov, P. A. Nilsson & C. Brönmark, 2007. Consequences of fish predation, migration and juvenile ontogeny on zooplankton spring dynamics. Limnology and Oceanography 52: 696–706.Google Scholar
- Källander, H., L.-A. Hansson, C. Brönmark & A. Nicolle, 2009. Waterfowl in Lake Krankesjön. Ornis Svecica 19: 65–87.Google Scholar
- Lindström Å., M. Green, R. Ottvall & S. Svensson, 2009. Övervakning av fåglarnas populationsutveckling. Yearly report 2008. Institute of Ecology, Lund: 80 pp.Google Scholar
- Lodge D. M., G. Cronin, E. van Donk & A. Froelich, 1998. Impact of herbivory on plant standing crop: comparisons among biomes, between vascular and non-vascular plants, and among freshwater herbivore taxa. In Jeppesen, E., M. Søndergaard, M. Søndergaard & K. Christoffersen (eds), The Structuring Role of Submerged Macrophytes in Lakes. Ecological Studies 131. Springer Verlag, New York: 149–174.Google Scholar
- Milberg, P., L. Gezelius, I. Blindow, L. Nilsson & T. Tyrberg, 2002. Submerged vegetation and the variation in the autumn waterfowl community at Lake Takern, southern Sweden. Ornis Fennica 79: 72–81.Google Scholar
- Moss, B., D. Stephen, D. J. Balayla, E. Bécares, S. E. Collings, C. Fernández-Aláez, M. Fernández-Aláez, C. Ferriol, P. García, J. Gomá, M. Gyllström, L.-A. Hansson, J. Hietala, T. Kairesalo, M. R. Miracle, S. Romo, J. Rueda, V. Russell, A. Ståhl-Delbanco, M. Svensson, K. Vakkilainen, M. Valentín, W. J. Van De Bund, E. van Donk, E. Vicente & M. J. Villena, 2004. Continental-scale patterns of nutrient and fish effects on shallow lakes: synthesis of a pan-European mesocosm experiment. Freshwater Biology 49: 1633–1649.CrossRefGoogle Scholar
- Nienhuis, P., 1978. An ecosystem study in Lake Grevelingen, a former estuary in the S.W. Netherlands. Kieler Meersforschungen 4: 247–255.Google Scholar
- Pannekoek, J. & A. J. van Strien, 2001. TRIM 3 Manual. TRends and Indices for Monitoring Data. Statistics Netherlands Voorburg Research paper no 0102.Google Scholar
- Reichholf, J., 1973. Die Bestandsutwicklung des Höcherschwans Cygnus olor und seine einordnung in das ökosystem der inn stau seen. Anzeiger der Ornitologischen Gesellschaft in Bayern 12: 237–247.Google Scholar
- Søndergaard, M., T. Lauridsen, E. Jeppesen & L. Bruun, 1998. Macrophyte-waterfowl interactions: tracking a variable resource and the impact of herbivory on plant growth. In Jeppesen, E., M. Søndergaard, M. Søndergaard & K. Christoffersen (eds), The Structuring Role of Submerged Macrophytes in Lakes. Ecological Studies 131. Springer Verlag, New York: 298–306.Google Scholar