CONICET | Buscador de Institutos y Recursos Humanos

This report describes the structure and seasonal dynamics of ciliated protozoa associated with variations in the physicochemical characteristics of the environment in a temporary pond in the Buenos Aires province, Argentina. Plankton samples were obtained and physicochemical variables measured monthly for two years. A total of 50 planktonic ciliates were recorded. The highest species richness occurred during the pond´s filling and stable-hydric phases. Upon the pond´s desiccation, the number of ciliate species decreased, with the lowest values being recorded in spring; while the highest abundance and biomass were observed before the droughts. Ciliate diversity tended to be higher after droughts but decreased with pond desiccation. Most of the ciliate species were rare and found during the filling periods. Vorticella convallaria, Pelagostrobilidium wilberti, and Coleps hirtus were dominant; Cyclidium glaucoma, Strobilidium caudatum, Pseudochilodonopsis piscatoris, Limnostrombidium viride, L. pelagicum, and Chilodonella sp. were common; and Pelagostrombidium mirabile along with Rhabdostyla sp.?an epibiont on cladocerans?were occasional. The first and the sum of all axes in canonical correspondence analysis explained a significant portion of the ciliate-data variance. The autumn and winter samples grouped together corresponding to the highest conductivities, high precipitations, and low temperatures?properties characterizing the filling and stable-hydric periods. The species were distributed mainly according to conductivity and temperature gradients along the first canonical axis. The structure and temporal dynamics of planktonic ciliates from this temporary pond varied with the changes in physicochemical characteristics of the environment determined by flooding and desiccation.