Background:

Although protists are important components of aquatic ecosystems and microhabitats, their knowledge in Mexico is scarce, making it relevant to contribute with studies of their diversity in the country.

Objective:

In this study, protist diversity and its spatial and temporal variation are documented in an urban dam in Querétaro, México.

Methods:

Superficial samplings were performed each week from August 2015 to July 2016 in two points of the dam: one towards its middle part and another in its posterior part. Richness and composition of taxa, both spatially and temporally, as well as the relationship of the communities with precipitation and atmospheric temperature, were compared using species richness comparison analyses at the same sample coverage and multivariate techniques.

Results:

17 taxa were determined, belonging to phyla Amoebozoa, Euglenozoa, Ciliophora and Heliozoa. 11 new records are provided for Querétaro, which is part of the semi-arid areas in the center of the country. The most frequent species in the sampling were Coleps hirtus, Paramecium caudatum, and Stentor coeruleus. The taxon composition between the sampling points was different and showed two richness peaks and two different communities in the year, which corresponded to wet and dry seasons.

Conclusions:

Seasonality plays an important role in the establishment and development of protist communities in the El Cajón dam.