Abstract
We investigated the effect of interannual variation of hydrosedimentological regime and connectivity on the zooplankton biodiversity in the Upper Paraná River floodplain. Zooplankton samplings were undertaken between 2000 and 2007, in different environments of the floodplain, including connected and isolated floodplain lakes, backwaters, rivers and channels. The zooplankton included 541 species. Rotifers showed the highest species richness and abundance. Among the zooplankton species, 71 represent new occurrence records for the floodplain. The species accumulation curve showed a continuous increase in gamma diversity, demonstrating the importance of long-term research for accurate knowledge of biodiversity in heterogeneous and dynamic ecosystems, such as the floodplains. Interannual beta diversity among studied years indicated a lesser alteration in community composition in 2001, when a long limnophase period was observed. In most of the environments, the highest species richness values were related to the greatest flooding amplitudes. Flooding amplitude, which is associated with connectivity, favors faunal exchange amongst the environments and between the pelagic and littoral zones. This explains the occurrence of both planktonic and non-planktonic species within the community. On the other hand, mean zooplankton abundance values were higher when a long isolation period occurred. Differences between the potamophase and limnophase amplitude associated with connectivity among the environments were the most important factors for the structure and dynamics of the zooplankton community in the Upper Paraná River floodplain.
Highlights
Biodiversidade de comunidades de zooplâncton na planície de inundação do Alto Rio Paraná: variações interanuais em estudos de longa duração
The goal of the present study was to investigate the effect of the interannual variation of hydrosedimentological regime and connectivity on the zooplankton biodiversity in the Upper Paraná River floodplain
The index of connectivity amongst the lentic and lotic environments in each system was greater in 2005-2007 for the environments linked to the Paraná and Baía rivers, and was greater in 2001 and 2007 for those associated with the Ivinheima River (Table 1)
Summary
Biodiversidade de comunidades de zooplâncton na planície de inundação do Alto Rio Paraná: variações interanuais em estudos de longa duração. Diferenças entre a amplitude de potamofase e a limnofase associada à conectividade entre os ambientes foram fatores preponderantes para estruturação e dinâmica da comunidade zooplanctônica na planície de Inundação do Alto Rio Paraná. Studies have shown remarkable interannual alterations influenced by climatic oscillations such as El Niño and La Niña (Bovo-Scomparin and Train, 2008), which determine anomalous periods in the hydrological dynamics of floodplain systems (Zalocar de Domitrovic et al, 2007) These climatic oscillations affect the frequency, intensity, tension, recurrence, amplitude and seasonality (FITRAS) of the water pulse (Neiff, 1990; 2001), and the degree of connectivity among floodplain biotopes. Several studies have investigated the effects of one annual cycle on the structure and dynamics of the aquatic community in the Paraná River floodplain (Lansac-Tôha et al, 2004a, b; Rodrigues and Bicudo, 2004; Train et al, 2004; Agostinho et al, 2004a); few have shown the effect of interannual variation on the community’s abundance and diversity (Zalocar de Domitrovic et al, 2007; Agostinho et al, 2004b; Bovo-Scomparin and Train, 2008; Rodrigues et al, 2009)
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