title: Chaos in a long-term experiment with a plankton community.
abstract: Mathematical models predict that species interactions such as competition and predation can generate chaos. However, experimental demonstrations of chaos in ecology are scarce, and have been limited to simple laboratory systems with a short duration and artificial species combinations. Here, we present the first experimental demonstration of chaos in a long-term experiment with a complex food web. Our food web was isolated from the Baltic Sea, and consisted of bacteria, several phytoplankton species, herbivorous and predatory zooplankton species, and detritivores. The food web was cultured in a laboratory mesocosm, and sampled twice a week for more than 2,300 days. Despite constant external conditions, the species abundances showed striking fluctuations over several orders of magnitude. These fluctuations displayed a variety of different periodicities, which could be attributed to different species interactions in the food web. The population dynamics were characterized by positive Lyapunov exponents of similar magnitude for each species. Predictability was limited to a time horizon of 15-30 days, only slightly longer than the local weather forecast. Hence, our results demonstrate that species interactions in food webs can generate chaos. 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.
authors.affiliation: Aquatic Microbiology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Nieuwe Achtergracht 127, 1018 WS Amsterdam, The Netherlands.
authors.forename: Elisa
authors.initials: E
authors.lastname: Benincà
authors.forename: Jef
authors.initials: J
authors.lastname: Huisman
authors.forename: Reinhard
authors.initials: R
authors.lastname: Heerkloss
authors.forename: Klaus D
authors.initials: KD
authors.lastname: Jöhnk
authors.forename: Pedro
authors.initials: P
authors.lastname: Branco
authors.forename: Egbert H
authors.initials: EH
authors.lastname: Van Nes
authors.forename: Marten
authors.initials: M
authors.lastname: Scheffer
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Ellner
mesh_terms: D000818:Animals; D001419:Bacteria / Q000378:metabolism; D020387:Food Chain; D008954:Models, Biological; D017711:Nonlinear Dynamics; D009792:Oceans and Seas; D010933:Plankton / Q000378:metabolism*; D011157:Population Dynamics; D013045:Species Specificity; D013997:Time Factors