JPR Advance Access originally published online on August 7, 2007
Journal of Plankton Research 2007 29(10):827-838; doi:10.1093/plankt/fbm062
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Grazing of two toxic Planktothrix species by Daphnia pulicaria: potential for bloom control and transfer of microcystins
1 Équipe de Microbiologie Aquatique, INRA-UMR CARRTEL, 75 av. de Corzent, BP 511, 74203 Thonon-les-bains Cedex, France 2 Centre d’Enseignement et de Recherche Eau, Ville, Environnement (Cereve), ENPC, 6–8 av. Blaise Pascal, 77455 Marne-la-Vallée Cedex 2, France 3 GRIL, Département de Sciences Biologiques, Université de Montréal, C.P. 6128 Succ. Centre ville, Montréal, Québec, Canada H3C 3J7 4 Aquatic Ecology and Ecosystem Studies, School of Environmental Systems Engineering, The University of Western Australia, 35 Stirling Highway, M015, Crawley, Western Australia 6009, Australia 5 Institut Pasteur-CNRS URA2172, Unité des Cyanobactéries, 25–28 rue du Dr Roux, 75724 Paris Cedex 15, France
* Corresponding Author: bernadette.pinel-alloul{at}umontreal.ca
Received on February 26, 2007; accepted on July 30, 2007
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Abstract |
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The role of zooplankton in the control of cyanobacterial blooms and the transfer of cyanotoxins to higher trophic levels are of great importance to the management of water resources. Many studies have focused on the cyanobacterium Microcystis, but few have examined the interactions between zooplankton and filamentous cyanobacteria. In this study, we provide experimental evidence for the potential grazing of two toxic strains of filamentous cyanobacteria, Planktothrix rubescens and P. agardhii, by Daphnia pulicaria, and for transfer of toxins in the planktonic food chain. We determined clearance rates (CRs) by adult and juvenile D. pulicaria of the two Planktothrix strains, Scenedesmus acutus and a mixture of S. acutus cells with P. rubescens culture filtrate. Filament lengths were analyzed, and microcystin (MCY) presence in Daphnia was assessed using the Protein Phosphatase-2A (PP-2A) Inhibition Assay. The two Planktothrix strains were equally grazed by D. pulicaria, but at lower CRs than S. acutus. Potential anti-grazer toxins in P. rubescens filtrate did not inhibit Daphnia grazing. Small P. rubescens (<100 µm) filaments were preferentially grazed by adult D. pulicaria, suggesting their limited ability to control a Planktothrix population during a bloom. Large quantities of MCYs were found in unstarved Daphnia previously exposed to Planktothrix, whereas quantities were significantly smaller in individuals starved for 24 h before preservation. This indicated a potential for transfer of toxins in the food chain by Daphnia, especially immediately after ingestion of toxic cyanobacteria.
Communicating editor: K.J. Flynn
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