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Aquatic Microbial Ecology

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AME 66:133-147 (2012)  -  DOI:

Aquatic protists modulate the microbial activity associated with mineral surfaces and leaf litter

Ute Risse-Buhl1,*, Martina Karsubke1,2, Jeanette Schlief1, Christiane Baschien3, Markus Weitere2,4, Michael Mutz1

1Department of Freshwater Conservation, Brandenburg University of Technology Cottbus, 15526 Bad Saarow, Germany
2Department of General Ecology and Limnology, University of Cologne, 50674 Cologne, Germany
3Department of Environmental Technology, University of Technology Berlin, 10587 Berlin, Germany
4Department of River Ecology, Helmholtz Centre for Environmental Research–UFZ, 39114 Magdeburg, Germany

ABSTRACT: Aquatic heterotrophic protists structure biofilm morphology and stimulate organic matter processing, but knowledge about their effects on the activity of surface-associated communities is still missing. Microcosm experiments revealed that the community respiration of young biofilms (7 d old) at mineral surfaces was not affected by co-cultivation with the raptorial feeder Chilodonella uncinata or the suspension feeder Tetrahymena pyriformis. However, grazing by both ciliates reduced the bacterial abundance and probably enhanced nutrient availability by recycling. Our data indicated an increased individual bacterial activity under grazing pressure, resulting in no net effect on the community respiration. In a second experiment, the respiration of leaf-associated microbial communities composed of the fungus Heliscus lugdunensis and a multispecies bacterial assemblage was significantly enhanced in the presence of T. pyriformis after 7 d of incubation. The stimulation was observed under both normoxic (turbulent) and hypoxic (turbulent and stagnant) conditions. After longer incubation, presumably matching an advanced phase of leaf degradation, T. pyriformis did not affect community respiration exposed to hypoxic stagnant conditions. In contrast to former studies, no impact of protists on leaf mass loss was observed. By stimulating leaf-associated community respiration, protists seem to affect processes involved in the initial phase of leaf processing.

KEY WORDS: Aquatic protists · Bacterial biofilms · Aquatic hyphomycete · Leaf litter decomposition · Respiration · Hypoxia

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Cite this article as: Risse-Buhl U, Karsubke M, Schlief J, Baschien C, Weitere M, Mutz M (2012) Aquatic protists modulate the microbial activity associated with mineral surfaces and leaf litter. Aquat Microb Ecol 66:133-147.

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