Intra-annual variation in ciliate species composition in distinct strata of a shallow floodplain lake

LUIZ FELIPE MACHADO VELHO, Gustavo Mayer Pauleto, Felipe Rafael de Oliveira, Bianca Trevizan Segovia, Bianca Ramos Meira, Fernando Miranda Lansac-Tôha, Paulo Roberto Bressan Buosi


Aim: We aimed to evaluate the variation in ciliate species composition throughout the year in different strata of Guaraná Lake, located at the Upper Paraná River floodplain. Methods: Samplings were performed monthly between March 2007 and February 2008, in three different depths: epilimnion, metalimnion and hypolimnion. Samples were concentrated using a plankton net (10µm) and organisms were identified in vivo using an optic microscope and specialized bibliography. Results: Of the 112 species identified, 13 were found exclusively during the high water periods and 39 during the low water period. Results of nonparametric extrapolation indices evidenced that the observed richness represented between 70% and 90% of the estimated richness. Regarding the variation in species composition, Beta1 index indicated that the alteration in composition between strata during the low water period was slightly greater than that registered during high waters and Cluster analysis evidenced a higher dissimilarity in ciliate species composition between periods than among the different strata. Moreover, the greatest variation in species composition was verified during the distinct hydrological periods, whereas no significant differences were observed for the different strata analysed. Conclusion: We found that in the planktonic compartment of this shallow lake ciliate species composition changed significantly between hydrological periods, whereas a higher similarity in species composition among strata was observed during the high water period. Therefore, alterations in the vertical distribution seem to be related to the homogenizing effect of the floods in the water column stability. 


Keywords: Protist, Plankton, Species richness, Diversity, Freshwater

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