Document Detail

Uncoupling of omnivore-mediated positive and negative effects on periphyton mats.
MedLine Citation:
PMID:  12768404     Owner:  NLM     Status:  MEDLINE    
The riverine grass shrimp (Palaemonetes paludosus) and eastern mosquitofish (Gambusia holbrooki) consume periphyton and small invertebrates, potentially affecting periphyton through negative effects (i.e., consumption) and/or positive effects such as nutrient regeneration, physical stimulation, and trophic cascades. We performed field experiments in the Everglades in which omnivores and periphyton were maintained in cages, with a fraction of the periphyton held in omnivore-exclusion bags that allowed passage of nutrients but prevented its consumption or physical disturbance. In some instances, periphyton growth rate increased with increasing omnivore biomass. Omnivores probably stimulated periphyton growth through nutrient regeneration, possibly subsidizing periphyton with nutrients derived from ingested animal prey. The net balance of omnivore-mediated negative and positive effects varied among experiments because of seasonal and spatial differences in periphyton characteristics. Consumption of periphyton mats might have been reduced by the arrangement of palatable algae (green algae and diatoms) within a matrix of unpalatable ones (CaCO(3)-encrusting filamentous cyanobacteria). In a laboratory feeding experiment, mosquitofish consumed more green algae and diatoms in treatments with disrupted mat structure than in those with intact mats. No difference in diet was observed for shrimp. Our study underscores the complexity of consumer-periphyton interactions in which periphyton edibility affects herbivory and consumers influence periphyton through multiple routes that cannot be fully appreciated in experiments that only investigate net effects.
Pamela Geddes; Joel C Trexler
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.     Date:  2003-05-27
Journal Detail:
Title:  Oecologia     Volume:  136     ISSN:  0029-8549     ISO Abbreviation:  Oecologia     Publication Date:  2003 Aug 
Date Detail:
Created Date:  2003-08-18     Completed Date:  2004-01-06     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0150372     Medline TA:  Oecologia     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  585-95     Citation Subset:  IM    
Department of Biological Science, Florida International University, Miami, FL 33199, USA.
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MeSH Terms
Algae, Green*
Feeding Behavior
Food Chain*
Population Dynamics
Grant Support
CA5280-8-9002/CA/NCI NIH HHS

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