Dormant ciliate community from the dry sediment of a temporary lake in a Neotropical floodplain

Abstract

Floodplains have a high diversity of aquatic environments, including temporary lakes that constantly suffer from drought events. To survive in these conditions, several groups of organisms, among them ciliate protists, have developed strategies to avoid dehydration, such as resistance cysts. Sediment samples were collected from the central region of the lake during a drought event. The sediments were dried in an oven and stored. For the experiment, the sediment was rehydrated with water and kept in an incubation chamber. Samples from 6 microcosms were taken every seven days for 9 weeks. The frequency of each ciliate species hatching from resting structures was calculated using the constancy index, with morphospecies classified as constant, accessory, or rare. A total of 82 ciliates morphospecies were recorded, of which four were constant, three accessory, and 75 rare. The Oxytrichidae and Euplotidae families showed the highest morphospecies richness, among which only 16 morphospecies were already recorded in the literature as producing cysts. Although no significant temporal difference was observed for the difference in the hatching of morphospecies over time. The morphospecies increment curve showed an increasing trend during the experiment. Finally, based on predicted climate change projections, temporary environments may experience longer and more frequent periods of drought, thus ciliate morphospecies that are able to remain in a form of resistance for a long period will outperform those that are more sensitive or lack this type of functional trait.