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  Cascading predation effects of Daphnia and copepods on microbial food web components

Zöllner, E., Santer, B., Boersma, M., Hoppe, H.-G., & Jürgens, K. (2003). Cascading predation effects of Daphnia and copepods on microbial food web components. Freshwater Biology, 48(12), 2174-2193.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-000F-DB7B-3 Version Permalink: http://hdl.handle.net/11858/00-001M-0000-000F-DB7C-1
Genre: Journal Article

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zoellner_2003.pdf (Publisher version), 304KB
 
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 Creators:
Zöllner, Eckart1, Author              
Santer, Barbara1, Author              
Boersma, Maarten1, Author              
Hoppe, Hans-Georg, Author
Jürgens, Klaus1, Author              
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1Department Ecophysiology, Max Planck Institute for Limnology, Max Planck Institute for Evolutionary Biology, Max Planck Society, ou_976547              

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Free keywords: bacteria; mesozooplankton; protists; trophic cascade
 Abstract: 1. We performed a mesocosm experiment to investigate the structuring and cascading effects of two predominant crustacean mesozooplankton groups on microbial food web components. The natural summer plankton community of a mesotrophic lake was exposed to density gradients of Daphnia and copepods. Regression analysis was used to reveal top-down impacts of mesozooplankton on protists and bacteria after days 9 and 15. 2. Selective grazing by copepods caused a clear trophic cascade via ciliates to nanoplankton. Medium-sized (20-40 mum) ciliates (mainly Oligotrichida) were particularly negatively affected by copepods whereas nanociliates (mainly Prostomatida) became more abundant. Phototrophic and heterotrophic nanoflagellates increased significantly with increasing copepod biomass, which we interpret as an indirect response to reduced grazing pressure from the medium-sized ciliates. 3. In Daphnia-treatments, ciliates of all size classes as well as nanoflagellates were reduced directly but the overall predation effect became most strongly visible after 15 days at higher Daphnia biomass. 4. The response of bacterioplankton involved only modest changes in bacterial biomass and cell-size distribution along the zooplankton gradients. Increasing zooplankton biomass resulted either in a reduction (with Daphnia) or in an increase (with copepods) of bacterial biovolume, activity and production. Patterns of bacterial diversity, as measured by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), showed no distinct grouping after 9 days, whereas a clear treatment-coupled similarity clustering occurred after 15 days. 5. The experiment demonstrated that zooplankton-mediated predatory interactions cascade down to the bacterial level, but also revealed that changes occurred rather slowly in this summer plankton community and were most pronounced with respect to bacterial activity and composition.

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Language(s): eng - English
 Dates: 2003-12
 Publication Status: Published in print
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 Rev. Method: Peer
 Identifiers: eDoc: 61126
Other: 2246/S 38070
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Title: Freshwater Biology
Source Genre: Journal
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Pages: - Volume / Issue: 48 (12) Sequence Number: - Start / End Page: 2174 - 2193 Identifier: ISSN: 0046-5070