16S rRNA amplicon sequencing of substrate biofilm communities in gravel- and sewage-sludge-biochar-based constructed wetlands under long-term polypropylene microplastic loading
This project provides bacterial 16S rRNA gene amplicon sequencing data from the substratebiofilms of laboratory-scale vertical subsurface-flow constructed wetlands (CWs) operated forapproximately 800 days under continuous polypropylene microplastic (PP-MP) loading. Theexperimental design combined two substrate types, gravel and sewage-sludge biochar, with fourinfluent PP-MP concentrations (0, 0.5, 5 and 50 mg/L), giving eight treatments. All reactors werecylindrical columns (33 cm high, 22 cm internal diameter) containing a 25-cm-deep substrate bed,planted with Sesuvium portulacastrum L., and operated in downward vertical-flow mode underidentical hydraulic and influent conditions; substrate type and PP-MP concentration were the onlyexperimental variables. At the stable operating stage, substrate was sampled separately from theupper and lower bed layers, with five spatial subsamples collected per treatment and depth,yielding 80 microbiome samples (eight treatments x two depths x five subsamples). The V3-V4region of the bacterial 16S rRNA gene was amplified with primers 341F (CCTACGGGNGGCWGCAG) and805R (GACTACHVGGGTATCTAATCC) and subjected to paired-end amplicon sequencing. These data weregenerated to resolve how substrate type, microplastic loading and bed depth shape the substratebiofilm community, and to link community composition and predicted extracellular polymericsubstance (EPS) biosynthetic potential to measured microplastic retention, EPS content andlong-term pore-space (porosity) evolution in these systems.