Diversity of protist genera in periphyton of tufa-depositing karstic river

PurposeIn aquatic ecosystems, protists play a crucial role and cover numerous ecological functions. The karstic Krka River (Croatia) is a unique hotspot for high diversity of aquatic organisms, especially protists. The main objective of the present study was to obtain a detailed overview of the protist community structure in the periphyton of the Krka River and to determine the differences in protist diversity along the river.MethodsProtist diversity was detected by amplicon sequencing of the hypervariable region V9 of the 18S rRNA gene, using the universal eukaryotic primer pair.ResultsThe three main groups of protists were as follows: Ciliophora, Cercozoa, and Bacillariophyta. In terms of abundance of protist OTUs, the shade plot revealed an evident difference from the upstream to downstream river section, which increased between locations from Krka spring to Skradinski buk. Diversity was explored using measures of alpha and beta diversity. Alpha diversity showed an increasing trend in the downstream direction of the river. The location effect, or clustering/grouping of samples by location, was confirmed by the PERMANOVA permutation test of beta diversity.ConclusionThe combination of alpha and beta diversity can help provide deeper insight into the study of diversity patterns, but also point out to decline in species diversity and allow for effective ways to protect aquatic karst habitats in future management.

Automated summary

The purpose of this study was to obtain a detailed overview of the protist community structure in the periphyton of the Krka River and determine the differences in protist diversity along the river. The results showed that the main groups of protists were Ciliophora, Cercozoa, and Bacillariophyta. Protist diversity increased in the downstream direction of the river. The findings can provide effective ways to protect aquatic karst habitats in future management.