Determination of the abundance of ciliates in highly turbid running waters - an improved method tested for the River Rhine

The enumeration of ciliates from riverine samples is often confounded by the problems of relatively low ciliate abundances combined with high turbidity. We successfully tested a method to determine abundance and taxonomic composition of planktonic ciliates in highly turbid running waters. The concentration of samples by sedimentation in Utermohl-chambers was combined with density gradient centrifugation (to exclude inorganic particles) and quantitative protargol staining (for taxonomic determination of species). The newly developed technique was compared with established methods (live counting, counting in Utermohl chambers and quantitative protargol staining without prior exclusion of inorganic particles). We could demonstrate that the newly developed technique gave, in addition to the quantification of ciliates, a detailed overview of taxonomic composition in the investigated samples.