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- Title
Omnivory, vertical food-web structure and system productivity: stable isotope analysis of freshwater planktonic food webs.
- Authors
FRANCE, ROBERT L.
- Abstract
Summary 1. The energetic hypothesis proposes that the vertical structure of food webs should increase in height with increasing system productivity. I measured the trophic positions and extent of trophic separation between the invertebrate planktivores Mysis relicta and Chaoborus spp. and their putative zooplankton prey along a gradient of lake productivity with the use of stable nitrogen isotopes. 2. In lakes of low productivity, these planktivores were found to be herbivorous, becoming omnivorous at intermediate lake productivities, and only able to be truly zooplanktivorous as lakes approached mesotrophy. A subsequent secondary analysis of literature data revealed that the strength of top-down trophic cascades among these organisms increased with lake productivity as reflected by relationships between the abundance of planktivores and that of phytoplankton. 3. Increased omnivory under conditions of low productivity, effectively shortening the vertical structure of food webs as predicted by the energetic hypothesis, may produce increased community stability.
- Subjects
OMNIVORES; CHAOBORUS; PLANKTON; RADIOACTIVE pollution of water; ZOOPLANKTON
- Publication
Freshwater Biology, 2012, Vol 57, Issue 4, p787
- ISSN
0046-5070
- Publication type
Article
- DOI
10.1111/j.1365-2427.2012.02744.x