Zooplankton succession during extraordinary drought–flood cycles: A case study in a South American floodplain lake |
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| Authors: | Griselda Chaparro María Cristina Marinone Ruben J Lombardo María Romina Schiaffino Alice de Souza Guimarães Inés O’Farrell |
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| Institution: | aLaboratorio de Limnología, Departamento de Ecología Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, C1428EHA, Buenos Aires, Argentina;bANCyPT (Agencia Nacional de Promoción Científica y Tecnológica), Argentina;cLaboratorio de Artrópodos, Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, C1428EHA, Buenos Aires, Argentina;dCONICET (Consejo Nacional de Investigaciones Científicas y Técnicas), Argentina;eLaboratório de Ecologia do Zooplâncton, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, CEP 31270-901, Minas Gerais, Brazil |
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| Abstract: | We examined the zooplankton abundance and composition of Laguna Grande, a floodplain wetland of the Lower Paraná Basin (Argentina), during an extraordinary drought–flood cycle that affected both the environment and the biological conditions of the lake. Low waters were characterised by remarkably high conductivities and pH values, and high phytoplankton and bacterioplankton abundances with cyanobacterial blooms, while high waters showed opposite features. In relation to zooplankton, the mean abundances of all the taxonomic groups (rotifers, cladocerans, copepods, ciliates, and heterotrophic nanoflagellates) were slightly higher at low waters. Major changes were observed in the specific composition of metazooplankton: the euryhaline species assemblage that dominated in the dry warm period was replaced by several oligohaline littoral and planktonic species characteristic of the Paraná River Basin, when the water level rose. Mean species richness values at high waters doubled those of low waters and were directly correlated to water depth. Most of the rotifers of the genus Brachionus and the cladoceran Moina micrura switched from parthenogenetic to sexual reproduction during low waters, as a response to a harsh environment and crowding. We suggest that the main changes in the environmental conditions in this eutrophic floodplain lake are driven by the hydrology, which regulates the zooplankton succession. The herein described shifts in the zooplankton structure and dynamics of Laguna Grande over an extraordinary drought–flood cycle contribute to the understanding of the processes that might occur under the scenarios predicted by climate change models. |
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| Keywords: | Drought&ndash flood cycle Floodplain lakes Zooplankton Phytoplankton Community structure Extreme conditions |
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