Structure and dynamic of planktonic ciliate community in a large Neotropical river: the relevance of the pluviosity and tributaries in the biodiversity maintenance

Fabio Amodeo Lansac-Toha, Heloisa Santos Silva, Orlando Pelissari Negreiros, Bianca Trevizan Segovia, Fernando Miranda Lansac-Toha, Bianca Ramos Meira, Paulo Roberto Bressan Buosi, Adalgisa Fernanda Cabral, Luiz Felipe Machado Velho


Abstract: Aim: We investigated the spatial and temporal patterns of abundance and diversity of planktonic ciliate community, in the last undammed stretch of the Upper Paraná River, Brazil. Methods: In order to reach this result, seven field campaigns were performed over two years. Plankton samples  were  collected  from  10  transects  through  this  stretch  of  the  river  (230  Km), near the banks and on the center, as well on  seven of its tributaries. Results: 95 ciliates species were identified, among which the peritrichs were the most abundant while the order  Hymenostomatida  was   the   most  specious   group.  We  recorded  a  remarkable increase  in  abundance  and  species  richness  along  the  river,  especially  in  the  rainy period. Moreover, in this period we found an increase in the beta-diversity along the river, which consists in a remarkable distinction among the low, middle and high stretch of the river. In this way, continuous changes in the community structure of planktonic ciliates were evidenced, highlighting the importance of the precipitation and tributaries in the maintenance of the highest regional diversity in the studied area. Conclusion: Our results strongly suggest the requirement for conservation actions with the purpose to maintain those tributaries   undammed, in order to avoid biotic homogenization processes and the consequent reduction of aquatic biodiversity in this important tropical ecosystem.


Protist; Ciliophora; abundance; species richness; lotic environments

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