1-mL samples of suspended biomass from the mix tank and PBR effluent were collected in triplicate and stored in 5-mL polypropylene transport tubes filled with 3 mL Zymo DNA/RNA Shield. Samples were kept at -20°C until they were shipped overnight on ice to the University at Buffalo (UB) SUNY. DNA extraction was performed using the DNeasy Powersoil Pro Kit (Qiagen), and extracts were stored at -20°C. PCR amplification of the eukaryotic 18S rRNA genes targeted the V8-V9 region (details in Bradley et al., 2016). Gel electrophoresis was conducted post PCR, and bands of expected size and quality were purified using the QIAquick gel purification kit (Qiagen). The purified amplicons from each sample were pooled into a DNA library at equimolar proportions (10 ng). Sequencing was performed on the Illumina MiSeq platform with v3 chemistry (300-cycle paired-end reads) at the UB Genomics and Bioinformatics Core. Raw sequencing data are available on NCBI under BioProject accession number PRJNA1045645. The sequencing read processing (i.e., quality filtering and trimming, taxonomic assignment) and statistical analyses (including alpha and beta diversity) were conducted following the established protocol (MiSeq SOP) provided by mothur v1.48.0. 40