High predation is of key importance for dominance of small-bodied zooplankton in warm shallow lakes: evidence from lakes, fish exclosures and surface sediments |
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Authors: | Carlos Iglesias N??stor Mazzeo Mariana Meerhoff Gissell Lacerot Juan M Clemente Flavio Scasso Carla Kruk Guillermo Goyenola Javier Garc??a-Alonso Susanne L Amsinck Juan C Paggi Susana Jos?? de Paggi Erik Jeppesen |
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Institution: | 1. National Environmental Research Institute, Aarhus University, Vejls?vej 25, 8600, Silkeborg, Denmark 2. Department of Biological Sciences, Aarhus University, Ole Worms All??, Building 1135, 8000, Aarhus C, Denmark 3. Grupo de Ecolog??a y Rehabilitaci??n de Sistemas Acu??ticos, Centro Universitario Regional Este-Facultad de Ciencias, Universidad de la Rep??blica, Maldonado, Uruguay 4. Secci??n Limnolog??a, Facultad de Ciencias, Universidad de la Rep??blica, Igu?? 4225, CP 11400, Montevideo, Uruguay 5. Laboratorio Tecnol??gico del Uruguay, Av. Italia 6201, CP 11500, Montevideo, Uruguay 6. Zoology Department, Natural History Museum, London, SW7 5BD, UK 7. Instituto Nacional de Limnolog??a-CONICET, Universidad Nacional del Litoral. Ciudad Universitaria. Paraje ??El Pozo??, CP 3000, Santa F??, Argentina 8. Greenland Climate Research Centre (GCRC), Greenland Institute of Natural Resources, Kivioq 2, P.O. Box 570 3900, Nuuk, Greenland 9. Sino-Danish Centre for Education and Research (SDC), Beijing, China
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Abstract: | The mean body size of limnetic cladocerans decreases from cold temperate to tropical regions, in both the northern and the southern hemisphere. This size shift has been attributed to both direct (e.g. physiological) or indirect (especially increased predation) impacts. To provide further information on the role of predation, we compiled results from several studies of subtropical Uruguayan lakes using three different approaches: (i) field observations from two lakes with contrasting fish abundance, Lakes Rivera and Rodó, (ii) fish exclusion experiments conducted in in-lake mesocosms in three lakes, and (iii) analyses of the Daphnia egg bank in the surface sediment of eighteen lakes. When fish predation pressure was low due to fish kills in Lake Rivera, large-bodied Daphnia appeared. In contrast, small-sized cladocerans were abundant in Lake Rodó, which exhibited a typical high abundance of fish. Likewise, relatively large cladocerans (e.g. Daphnia and Simocephalus) appeared in fishless mesocosms after only 2 weeks, most likely hatched from resting egg banks stored in the surface sediment, but their abundance declined again after fish stocking. Moreover, field studies showed that 9 out of 18 Uruguayan shallow lakes had resting eggs of Daphnia in their surface sediment despite that this genus was only recorded in three of the lakes in summer water samples, indicating that Daphnia might be able to build up populations at low risk of predation. Our results show that medium and large-sized zooplankton can occur in subtropical lakes when fish predation is removed. The evidence provided here collectively confirms the hypothesis that predation, rather than high-temperature induced physiological constraints, is the key factor determining the dominance of small-sized zooplankton in warm lakes. |
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