The Temporal Asynchrony of Planktonic Cladocerans Population at Different Environments of the Upper Paraná River Floodplain

The aim of this study was to investigate the existence of synchronic fluctuation patterns in cladoceran populations of the Upper Paraná River floodplain. The following hypothesis were tested: (i) the populations of a given species present the same fluctuation pattern in abundance for different environments and (ii) synchrony is higher when we consider subsets of neighboring environments or those belonging to the same category (e.g., lagoons, rivers). Samplings were performed every three months from February 2000 to November 2002 at 11 sites. To evaluate spatial synchrony, the intraclass correlation coefficient was used. The results showed no significant correlation for the most abundant species, meaning that fluctuation patterns of planktonic cladocerans were asynchronous. Asynchrony indicated that the influence of floods and regional climatic factors was not strong enough to synchronize the populations, suggesting that local factors were more important than regional effects in determining zooplankton abundance patterns. The implications of these results are that the observations from a single environment cannot be extrapolated to other environments in a manner that would allow its use as a sentinel site. This means that a monitoring program for floodplain systems, or at least for the Paraná River floodplain, has to comprise greater spatial extents. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)