Copepod community structure (Crustacea: Copepoda) in a longitudinal environmental gradient in a tropical river-floodplain system, Brazi

Welinton Sausa Palhiarini, Fabio Amodeo Lansac Toha, Leilane Talita Fatoreto Schwind, Rodrigo Leite Arrieira, Luiz Felipe Machado Velho

Resumo


In this study, we analyzed the structure of the copepod community along a longitudinal axis of the last dam-free stretch of the river-floodplain system of the high Paraná River, downstream of the Porto Primavera dam. Our hypotheses were (i) there is an enhancement in diversity and abundance of the copepod community as distance from the dam increases; (ii) the attributes of the community are higher in tributaries and marginal lakes, located in the floodplain; and (iii) the composition pattern of copepod species is related to the environmental gradient. Method: Sampling was done quarterly in 2013 and 2014, at the subsurface of the limnetic region. Sampling points were located along the Paraná River, in seven of its tributaries, and in eight lakes located in its floodplain. Results: we identified 29 species belonging to two families: Cyclopidae (21 species) and Diaptomidae (eight species). On contrary to what we hypothesized, results from and ANOVA showed a significant decay in copepod abundance in the upstream-downstream direction in the Paraná River. In the same way, the tributaries showed higher values of community attributes in the upstream region. Results of a RDA showed that species composition answered to the environmental gradient so that Argyrodiaptomus azevedoi, Notodiaptomus iheringi, N. henseni, N. cf. spinuliferus and N. cearensis occurred specially were there was higher concentrations of phosphorous and turbidity. In addition, the first three species of Notodiaptomus correlated positively with electrical conductivity. On the other hand, Thermocyclops minutus and T. decipiens were registered in areas with higher values of pH and lower depth. Conclusion: We highlight the importance of the maintenance of the ecological integrity of the high Paraná River floodplain and especially of its tributaries, in order to support the high biodiversity registered in the last dam-free stretch of this important tropical river. Furthermore, we highlight the importance of the manipulation of the output of reservoirs located upstream of this stretch.

Palavras-chave


Zooplankton; Dam; Cascading Reservoir Continuum Concept; Flood pulse; Hydrological connectivity



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