title: Non-linear analysis indicates chaotic dynamics and reduced resilience in model-based Daphnia populations exposed to environmental stress.
abstract: In this study we present evidence that anthropogenic stressors can reduce the resilience of age-structured populations. Enhancement of disturbance in a model-based Daphnia population lead to a repression of chaotic population dynamics at the same time increasing the degree of synchrony between the population's age classes. Based on the theory of chaos-mediated survival an increased risk of extinction was revealed for this population exposed to high concentrations of a chemical stressor. The Lyapunov coefficient was supposed to be a useful indicator to detect disturbance thresholds leading to alterations in population dynamics. One possible explanation could be a discrete change in attractor orientation due to external disturbance. The statistical analysis of Lyapunov coefficient distribution is proposed as a methodology to test for significant non-linear effects of general disturbance on populations. Although many new questions arose, this study forms a theoretical basis for a dynamical definition of population recovery.
authors.affiliation: Institute for Environmental Research, RWTH Aachen University, Aachen, Germany.
authors.forename: Richard
authors.initials: R
authors.lastname: Ottermanns
authors.affiliation: Institute for Environmental Research, RWTH Aachen University, Aachen, Germany.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Szonn
authors.affiliation: Institute for Environmental Research, RWTH Aachen University, Aachen, Germany.
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Preuβ
authors.affiliation: Institute for Environmental Research, RWTH Aachen University, Aachen, Germany.
authors.forename: Martina
authors.initials: M
authors.lastname: Roβ-Nickoll
mesh_terms: D000818:Animals; D003198:Computer Simulation; D003621:Daphnia / Q000502:physiology*; D017753:Ecosystem; D008962:Models, Theoretical; D017711:Nonlinear Dynamics; D011157:Population Dynamics; D013312:Stress, Physiological / Q000502:physiology*