This document describes a study of microbial eukaryotes in the Movile Cave ecosystem using metabarcoding of the 18S rRNA gene. The researchers used Illumina sequencing of the V4-V5 regions and bioinformatic analysis to characterize the protist diversity and compare communities across three samples: floating biofilm, live biofilm, and plankton. The analysis identified 30 operational taxonomic units (OTUs) shared among all three samples, representing the core protist community of the cave. Alveolata and Stramenopiles were the most abundant superphyla. Additionally, 197 OTUs found in only one sample indicate minor divergent species depending on the environment.