Wednesday, August 8, 2007

PS 51-162: Stage structure and synchronization cause single-species oscillations in phytoplankton chemostat populations

Thomas M. Massie1, Bernd Blasius2, Guntram Weithoff1, Ursula Gaedke1, and Gregor F. Fussmann3. (1) University of Potsdam, (2) University of Oldenburg, (3) McGill University

We show experimentally that the physiological structure of phytoplankton populations can crucially affect single-species population dynamics. In our chemostat experiments, synchronization of the individuals’ cell division cycle led to oscillatory dynamics in separate cultures of three different unicellular species of phytoplankton. A stage-structured model by Pascual & Caswell (1997) suggests that nutrient dependence of certain phases of the cell cycle may ultimately cause single-population oscillations. In line with this work, we propose that nitrogen-dependence in the G1-phase and the fact that the individual development  temporarily ceases when this essential nutrient is deficient provided a mechanism by which the cell cycles within algal populations became synchronized. Synchronized experimental populations exhibited moderate-amplitude oscillations around a steady-state. The period lengths of the oscillations ranged from 25 h (Chlamydomonas reinhardtii) to 33 h (Monoraphidium minutum) and 44 h (Chlorella vulgaris). Hence, the oscillations cannot be explained by circadian rhythms, at least in the two latter cases. Our study provides strong experimental evidence for intrinsic oscillations in single-species algal populations, i.e. oscillatory dynamics that occur in the absence of multi-species interaction or external forcing.

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See more of The ESA/SER Joint Meeting (August 5 -- August 10, 2007)