We use the outstanding long-term time series on Lake Constance physics, chemistry and plankton established by the Limnological Institute, University of Konstanz and by the Institute for Lake Research, Langenargen / IGKB for exemplary studies on the influence of climate variability on lake ecosystems. Using these data we have shown that during the last decades Lake Constance was strongly influenced by the North Atlantic Oscillation and experienced significant warming. Variability in the North Atlantic Oscillation had a strong influence on the hydrodynamics of the lake, which in turn influenced the chemistry, plankton and fish. In addition to statistical analysis of the long-term data we use simulation models to increase our mechanistic understanding of the climate influence.
Our analyses have shown
1) That there is not one but there are a multitude of climatic influences on the dynamics of a specific ecosystem. Climate changes will influence species directly via temperature-dependence of growth and developmental rates (Straile 2000, Seebens et al. 2007, Straile et al. 2007), but also indirectly via mixing processes which alter the light environment (Peeters et al. 2007a) and nutrient availability (Straile et al. 2003) for phytoplankton and thus for primary production. Finally indirect climate influences will occur also via food web interactions (Straile 2000, 2002).
2) There is not only an immediate ecosystem response to climate variability, but the climate signal may show striking memory effects, which might last at least for one year. Such memory effects are based on different mechanisms ranging from hydrodynamics (Straile et al. 2003, 2007) to cohort dynamics (Seebens et al. 2007) and food web interactions (Straile 2000).
3) There are strong species specific responses to climate variability depending on e.g. the life histories and seasonal phenology of species occurrences and reproduction (Seebens et al. 2007, 2009, Straile et al. 2007).
4) That despite the species-specifity, biological responses, e.g. food web interactions to climate variability can be highly coherent across large spatial scales. For example, we have shown that the NAO influence on the timing of the clear-water phase which was first documented in Lake Constance (Straile 2000), can be observed also in Müggelsee, a hypertrophic shallow lake 700 km apart from Lake Constance (Straile & Adrian 2000), in a suite of shallow Dutch lakes (Scheffer et al. 2001) and in central-European lakes of different morphology and lake trophy (Straile 2002).
5) with future warming epi- but also hypolimnetic water temperatures will increase, the duration of winter mixing will decrease and the onset of the phytoplankton spring bloom will significantly advance (Peeters et al. 2007b). Likwise the timing of the Daphnia peak and the timing of whitefish hatching will advance (Straile et al. 2015). Simulation results suggest that with seasonally homogenous warming the risk of mismatch between these players will be small whereas the consequences of seasonally heterogenous warming for the disruption of feeding interactions may be more important.
Detailed accounts on how the influence of climate can be found throughout the ecosystem and food web of Lake Constance can be found in the following publications:
- Lake physics: Straile et al. 2003, 2010, Peeters et al. 2007a, 2007b
- Nutrient and oxygen distributions: Straile et al. 2003
- Phytoplankton: Anneville et al. 2005, Peeters et al. 2007a, 2007b, Straile et al. 2010, 2015
- Bosmina: Straile & Müller 2010
- Daphnia Straile 2000, Schalau et al. 2008, Straile et al. 2015
- Eudiaptomus gracilis: Seebens et al. 2007
- Cyclops vicinus: Seebens et al. 2009
- whitefish (Coregonus lavaretus): Straile et al. 2007, Straile et al. 2015