16S Amplicon sequence variants (ASVs) data of NEREA Augmented Observatory

Metabarcoding - 16S ASV generation and taxonomic assignment. Raw 16S paired-end sequences were subjected to a data quality control step and subsequently imported into the QIIME2 pipeline v.2022.2.0. Leftover primers and adapter sequences were removed through cutadapt. The amplicon sequence variants (ASV) table, which represent true biological sequences within each sample, was generated using the denoised-paired method including truncation, denoising, dereplication, merging, and chimera filtering of the DADA2 (Divisive Amplicon Denoising Algorithm 2) plugin inside QIIME2. Default parameters were used with the exception of the forward and reverse sequence length (--p-trunc-len-f and --p-trunc-len-r), that were set to 220 and 180, respectively. Processed reads that passed all these filters were used for taxonomy classification. The V4-V5 regions were extracted from the pre-formatted reference sequences and taxonomy file built on the SILVA 138 99% OTUs database and the vsearch v.2.6.2 global alignment implemented in QIIME2 was used.