An experimental study of habitat choice by Daphnia: plants signal danger more than refuge in subtropical lakes

Summary 1. In shallow temperate lakes, submerged plants often provide refuge for pelagic zooplankton against fish predation, a mechanism with potential strong cascading effects on water transparency and on the entire ecosystem. In (sub)tropical lakes, however, the interaction between aquatic plants...

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Bibliographic Details
Published in:	Freshwater biology Vol. 51; no. 7; pp. 1320 - 1330
Main Authors:	MEERHOFF, MARIANA, FOSALBA, CLAUDIA, BRUZZONE, CARLA, MAZZEO, NÉSTOR, NOORDOVEN, WILLEMIJN, JEPPESEN, ERIK
Format:	Journal Article
Language:	English
Published:	Oxford, UK Blackwell Publishing Ltd 01-07-2006 Blackwell Science
Subjects:	alarm signal alarm signals Animal and plant ecology Animal, plant and microbial ecology Biological and medical sciences Ceratophyllum demersum chemical communication chemical cue Cnesterodon decemmaculatus Daphnia obtusa diel vertical migration Eichhornia crassipes Fresh water ecosystems Freshwater Fundamental and applied biological sciences. Psychology horizontal distribution kairomone life-history traits littoral-zone pelagic prey phototactic behavior Pistia stratiotes predator-avoidance refuge effect Salvinia auriculata shallow lake submerged macrophytes Synecology chemical cue alarm signal Cladocera Habitat selection Experimental study Refuge Kairomone Crustacea Freshwater environment Plant Signal Hydrobiology Arthropoda Alarm Daphnia Lakes Predator Invertebrata Branchiopoda refuge effect Avoidance Chemical stimulus predator-avoidance
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Summary:	Summary 1. In shallow temperate lakes, submerged plants often provide refuge for pelagic zooplankton against fish predation, a mechanism with potential strong cascading effects on water transparency and on the entire ecosystem. In (sub)tropical lakes, however, the interaction between aquatic plants and predation may be more complex, particularly because fish density is high within the plant beds in such systems. 2. Using laboratory ‘habitat choice’ experiments, we determined the effects of three (sub)tropical free‐floating plants, Eichhornia crassipes, Pistia stratiotes and Salvinia auriculata and the cosmopolitan submerged Ceratophyllum demersum, on horizontal movement by the water flea Daphnia obtusa. We tested for avoidance of plants in the absence and presence of alarm signals from crushed conspecifics and chemical cues from the fish Cnesterodon decemmaculatus, the fish have been subjected to different feeding regimes. 3. In the absence of other stimuli, D. obtusa strongly avoided the plants and the crushed conspecifics, as expected. However, the response to fish was insignificant regardless of their previous feeding regime. The avoidance of free‐floating plants was more pronounced than that of the submerged plant. Contrary to predictions based on research in temperate lakes, Daphnia did not take refuge among the plants but rather swam away from them when exposed simultaneously to plants and alarm signals. 4. We hypothesise that the avoidance of plants by D. obtusa may ultimately be attributable to an expectedly higher predation risk within the plants than in the pelagic, because of a high density of associated zooplanktivorous fish in the former. In the (sub)tropics, therefore, aquatic plants and particularly the free‐floating ones, may not promote cascading effects via Daphnia grazing on phytoplankton as seen in temperate eutrophic lakes.
Bibliography:	ark:/67375/WNG-36GWGW78-S istex:9C9C00EBABF16C9C049DA1F4FBCE45C08AFBC982 ArticleID:FWB1574 ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2
ISSN:	0046-5070 1365-2427
DOI:	10.1111/j.1365-2427.2006.01574.x