A Study of Ciliate Protozoa from a Small Polluted Stream in East-Central Illinois

Abstract

The role of species of ciliate Protozoa in trickling filter waste treatment processes awaits redefinition. Using the small fresh-water Salt Fork stream for our study, a stream which receives all of the discharge from the Champaign-Urbana Waste Treatment Plant in east-central Illinois, analyses of samples of carefully identified ciliates taken from selected sites over a three-year period yielded some interesting results. Four specific situations were noted: (1) free-swimming microphagous forms feeding selectively on primarily attached bacteria, and, in turn, being fed on by carnivorous ciliates; (2) sessile ciliates (peritrichs) feeding on non-attached bacterial species, but with high selectivity; (3) free-swimming carnivorous gymnostomes feeding on the sessile peritrichs but, again in turn, serving as prey themselves to stalked suctorian species attached to the peduncles of the peritrichs; (4) attached peritrichs and suctorians both serving as food for several groups of small invertebrates frequenting the stream. With respect to numbers and diversity of ciliates found, some 155 different species, belonging to 93 genera, were identified (including several to be described elsewhere as new species) in the stream and/or the trickling filter settling basin. The highest populations and greatest diversity were found at sites closest to the waste water influx; such protozoan populations might thus be considered as a form of tertiary treatment in the drainage basin.