Vol. 53, 2014

Temporal structure of the peritrich ciliate assemblage in a large Neotropical lake

Lúcia SL Safi, Nelson F Fontoura, Henrique J Severo and Laura RP Utz*

Programa de Pós-Graduação em Zoologia, Faculdade de Biociências, Pontifícia Universidade Católica do Rio Grande do Sul, Av. Ipiranga 6681, Porto Alegre, RS 90619-900, Brazil

Abstract
Background: Periphytic communities are usually composed by prokaryotic and eukaryotic microbes and small metazoans and could be found in any submerged surface in aquatic environments. Ciliates generally are the dominant organisms in periphytic communities where they can form assemblages of complex taxonomic composition. Among these ciliate taxa, peritrichs are very common organisms found in periphyton; also, they are easy to collect, be easily recognized, and have been widely used to evaluate and monitor ecological and ecotoxicological investigations. Several studies have been focused on periphytic communities in freshwaters from the Northern Hemisphere, with very little data on similar environments in the South. In the present study, we analyzed the structure and temporal dynamics of the ciliate peritrich community in a Neotropical shallow lake,comparing the fluctuation of the peritrich community with environmental factors.
Results: Peritrichia comprised a total of 22 morphospecies throughout the year with genera Epistylis and Vorticella the most diverse and abundant genera. Peritrich density was considerably higher during fall and winter, demonstrating a clear seasonal cycle. Small, solitary species showed no pattern of dominance during any particular stage of succession, reaching abundance peak any time during the sampling period. On the other hand, large colonial species were abundant only in the last half of each successional cycle. Species abundance was correlated to temporal and environmental drivers.
Conclusions: Our results support the hypothesis of a temporal pattern of succession in the community of peritrich ciliates that composes the periphyton of the studied lake with different responses by individual species tosuccessional time, year, season, and environmental factors.

Key words: Periphyton; Biofilm; Community; Subtropical; Pollution.

*Correspondence: E-mail: laura.utz@pucrs.br