Structure and distribution of ciliate epibiont communities in a tropical floodplain

Our objective was to investigate the possible factors driving the relationship between ciliates and copepods in a floodplain; for this purpose, we collected samples from the upper Paraná River floodplain in Brazil, in lotic and lentic habitats (rivers, channels, and lakes), which amounted to 36 sampling sites during two hydrological periods. Our results presented a significant difference regarding bacterial density, host abundance, and prevalence of infestation between the samples performed during limnophase and potamophase. The nutrient pool alteration of the aquatic systems during the flood changes the abiotic characteristics of the water such as temperature, turbidity, ammonium ion, total nitrogen, total phosphorus and chlorophyll concentrations, and accordingly food availability (bacterial density) and host abundance, thus influencing the prevalence of epibiont ciliates. Our results indicate that both extrinsic (e.g., physical and chemical), and intrinsic (e.g., food availability and host abundance) factors are regulating the populations of epibiont ciliates in the floodplain.