Diversity and abundance of planktonic ciliated protists: How the analyzer’s eye can affect the results

Planktonic freshwater organisms, such as ciliates, play an important role in the transfer of matter and energy and, therefore, in the functioning of aquatic ecosystems. Due to their small size, the analysis of these communities is usually carried out using optical microscopy and various techniques. However, there are many challenges regarding this group, such as the difficulty in identifying them and the lack of experienced personnel for counting these organisms. Therefore, the aim of this study was to compare possible discrepancies in the results of organism counts, taking into account that these results may be influenced by the individual carrying out the sampling. To this end, the differences in the analyses of richness and abundance performed by four (4) analyzers and their respective ratings of the fixed samples were compared. The hypothesis was that more experienced analyzers would record higher values of species richness and density scores than those with less experience. The results obtained were consistent with the initial hypotheses and showed that two of the more experienced analyzers were associated with higher values for the attributes analyzed.