AME 70:141-155 (2013)  -  DOI: https://doi.org/10.3354/ame01649

ABSTRACT: The intermediate disturbance hypothesis (IDH) predicts that disturbances of moderate frequency or intensity result in maximum diversity, while the dynamic equilibrium hypothesis (DEH) proposes that disturbance and productivity interact in their effects on diversity. These hypotheses were tested with a marine ciliate community in a mesocosm study conducted in a Norwegian fjord. Two nutrient regimes, 6 disturbance frequencies (undisturbed to daily disturbed) and 2 replicates for each treatment were used. To disturb the system, we repeatedly lowered and raised a disk to mix the water column. The experiment lasted 3 wk, with samples (7 including the initial sample) taken for nutrients and physical parameters, chl a, ciliates and mesozooplankton. The system reacted more strongly to nutrient addition than to our chosen range of disturbance frequencies. Nutrient addition resulted in higher chl a levels and ciliate abundance but reduced ciliate diversity without changing the mean ciliate species richness. The reduction in diversity was due to the very strong, positive response to nutrient addition by the mixotrophic Mesodinium rubrum. In contrast, metazoan predators on ciliates (primarily copepods) did not respond to any of the experimental manipulations, at least partially due to the duration of the experiment relative to their generation times. While disturbance had varied and at times marked effects on the mesocosm communities, the expected unimodal response to disturbance frequency was not seen, nor was the expected interaction between disturbance and productivity. While the IDH and DEH have intuitive appeal, they appear to have limited power to predict natural ciliate community patterns.

KEY WORDS: Disturbance · Dynamic equilibrium · Nutrients · Ciliates · Mesodinium rubrum

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Cite this article as: Hingsamer P, Striebel M, Stockenreiter M, Ptacnikova R, Ptacnik R, Wickham SA (2013) Interaction of productivity and disturbance in a marine ciliate community: a mesocosm study. Aquat Microb Ecol 70:141-155. https://doi.org/10.3354/ame01649 Export citation Share:    Facebook - - linkedIn