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A seasonal alternation of coherent and compensatory dynamics occurs in phytoplankton

Authors

  • David A. Vasseur,

  • Ursula Gaedke,

  • Kevin S. McCann


D. A. Vasseur, Biology Dept, McGill Univ., 1205 Ave. Docteur Penfield, Montréal, Québec, Canada, H3A 1B1. – U. Gaedke, Universität Potsdam, Institut für Biochemie und Biologie, Maulbeerallee 2, DE-14469 Potsdam, Germany. – K. S. McCann and present address for DAV, Dept of Zoology, Univ. of Guelph, Guelph, Ontario, Canada, N1G 2W1 (david.vasseur@mail.mcgill.ca).

Abstract

Functional groups with diverse responses to environmental factors sum to produce communities with less temporal variability in their biomass than those lacking this diversity. The detection of these compensatory dynamics can be complicated by a spatio-temporal alternation in the environmental factors limiting growth (both abiotic and biotic), which restricts the occurrence of compensatory dynamics to certain periods or locations. Hence, resolving the spatio-temporal scale may uncover important spatial and/or temporal components in community variability. Using long-term data from Lake Constance (Bodensee), we find that a reduction in grazing pressure and relaxed competition for nutrients during winter and spring generates coherent dynamics among edible and less edible phytoplankton. During summer and fall, when both grazing pressure and nutrient limitation are present, edible and less edible phytoplankton exhibit compensatory dynamics. This study supports recent work suggesting that both abiotic and biotic interactions promote compensatory dynamics and to our knowledge, this is the first example of a system where compensatory and coherent dynamics seasonally alternate.

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