Monday, August 4, 2008 - 1:30 PM

COS 6-1: Chaos in a long term experiment with a plankton community

Elisa BenincÓ1, Jef Huisman1, Reinhard Heerkloss2, Klaus D. J÷hnk1, Pedro Branco1, Egbert H. Van Nes3, Marten Scheffer3, and Stephen P. Ellner4. (1) University of Amsterdam, (2) University of Rostock, (3) University of Wageningen, (4) Cornell University


Mathematical models predict that plankton communities may generate chaos. However, these mathematical predictions have never been demonstrated empirically. Here, we present the first demonstration of chaos in a complex planktonic food web (Benincà et al. 2008. Nature 451: 822-825). Our food web was isolated from a coastal ecosystem in the Baltic Sea, and consisted of phytoplankton, zooplankton, heterotrophic bacteria, and detritivores.  The food web was cultured in a laboratory mesocosm experiment for more than 2300 days, and sampled twice a week.


Despite constant external conditions, the species abundances showed striking fluctuations over several orders of magnitude.  The population dynamics were characterized by significantly positive Lyapunov exponents. Predictability was limited to a time horizon of 15–30 days, only slightly longer than the local weather forecast. Hence, our results provide the first experimental demonstration of chaos in a complex food web. This implies that stability is not required for the persistence of complex food webs, and that the long-term prediction of species abundances can be fundamentally impossible.