design: Biofilm samples and filters were subdivided into three subsamples to generate technical triplicates. DNA was extracted using the DNeasy PowerSoil Kit and quantified prior to sequencing. Microbial community composition was assessed by full-length 16S rRNA gene amplicon sequencing using Oxford Nanopore Technologies. The 16S rRNA gene was amplified with universal primers (27F/1492R), barcoded, pooled in equimolar proportions, and sequenced on a GridION Mk1 platform using R9.4.1 flow cells with high-accuracy basecalling.