Is the periphytic structure of Testaceans (Protozoa: Rhizopoda) related to water quality: A case study in the Cuiabá River, Brazil

Abstract

Presented study describes the periphytic community of Testaceans of the Cuiabá River, Central Brazil and evaluates its relationships to physical, chemical and biological water characteristics. Three sampling stations were established along an urban reach passing Cuiabá city, realizing four campaigns at the right and left river margins. Canonical Correspondence Analysis was conducted to study relationships of chemical and physical water characteristics with the colonization of the periphytic community of Testaceans on artificial substrata. Assemblage composition varies according to seasonal hydrological cycles and water quality, as well as spatially along the pollution gradient reflected by sampling sites along the river reach. Species richness and abundance showed highest values during the dry season, being Cochlyopodium, Centropyxis and Cyclopyxis the most common genera. The genus Centropyxis was frequent at all sampling stations throughout the year, being dominant at the highest impacted station. 27 of the 28 Difflugia species were only observed in the dry season under low flow velocities and discharge and have little potential as indicator of water quality parameters. On the other hand, species such as Cyclopyxis plana microstoma and Euglypha acanthophora only occured at impacted sampling stations, independently of the season, indicating a potential for bioindication.