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Omnivory does not prevent trophic cascades in pelagic food webs
Author(s) -
OKUN NILS,
BRASIL JANDESON,
ATTAYDE JOSÉ LUIZ,
COSTA IVANEIDE A. S.
Publication year - 2008
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1111/j.1365-2427.2007.01872.x
Subject(s) - trophic cascade , trophic level , pelagic zone , zooplankton , food web , plankton , ecology , biology , phytoplankton , abundance (ecology) , temperate climate , omnivore , biomass (ecology) , eutrophication , environmental science , fishery , nutrient , predation
Summary 1. Strong trophic cascades have been well documented in pelagic food webs of temperate lakes. In contrast, the limited available evidence suggests that strong cascades are less typical in tropical lakes. 2. To measure the effects of omnivorous tilapia on planktonic communities and water transparency of a small man‐made tropical lake, we performed a 5‐week in situ enclosure experiment with five densities of fish randomly allocated to 20 enclosures. Zooplankton and Phytoplankton biomasses as well as water transparency were measured weekly. 3. Results show that omnivorous tilapia significantly decreased the abundance of large Cladocerans, increased the abundance of small algae (greatest axial linear dimension <50 μ m) and decreased water transparency as predicted by trophic cascade theory. 4. Therefore, omnivory was not a sufficient factor to prevent a trophic cascade in this pelagic community, although the cascade effect was weaker than reported from many north temperate, nutrient‐rich lakes.