Short-term and seasonal dynamics of planktonic protist community (Alveolata, Ciliophora) in a neotropical urban lake, Maringá - Paraná, Brazil

Abstract

The aim of this study was to investigate the temporal dynamics of planktonic ciliate communities, based on daily fluctuations between different hydrological periods in a eutrophic urban lake located in the city of Maringá, Paraná, Brazil. We hypothesized that abundance would vary more between collection days than between hydrological periods, whereas richness and selection would vary more between hydrological periods than collection days. Ciliated protists were sampled during two distinct hydrological periods: a dry period in September 2018 and a rainy period in January 2019. Sampling was conducted 10 times during each period, with collections every 3 days over 30 days. Throughout the study, 84 morphospecies were recorded. The Prostomatida group dominated in both periods, contributing to 37.1 % of the total abundance in the dry season and 74 % in the rainy season. Other representative groups included Peritrichia (35.7 % in the dry season) and less abundant taxa such as Nassulida, Colpodea, and Cyrtophorida (8.5 % in the rainy season). Abundance varied significantly in the short term (i.e. between sampling days) and between hydrological periods (dry and rainy), with higher values during the rainy season (mean ± SE: 1250 ± 150 Ind.L⁻¹) compared to the dry season (mean ± SE: 850 ± 120 Ind.L⁻¹). Differences in richness were not significant between the hydrological periods. However, there was significant daily variation during the rainy season. Species composition differed only between hydrological periods, as predicted. This study shows that the hydrological regime significantly influences ciliate communities, with variations in richness, abundance, and composition occurring over short periods. Therefore, it is recommended that these organisms be analyzed continuously, across short intervals, and seasonally. This approach is necessary because their responses to environmental monitoring may vary depending on the sampling period, given their high sensitivity to environmental changes.