A long-term ecological research data set from the marine genetic monitoring programme ARMS-MBON 2020-2021

Continuing the international efforts of the ARMS Marine Biodiversity Observation Network (ARMS-MBON), we present data from the second sampling campaign, coming from 56 Autonomous Reef Monitoring Structures (ARMS) deployed in 2020 and 2021 along European coasts under the European Marine Omics Biodiversity Observation Network (EMO BON). The dataset includes information on sampling locations and conditions, sample archiving and quality reports of collected samples. Data and metadata are openly accessible and can be downloaded from the associated GitHub repository. Sequence data can be accessed via the European Nucleotide Archive (ENA) through the corresponding accession numbers. Images of ARMS plates are stored on PlutoF and can be downloaded through links provided in this paper. Sequence data were processed and explored with the PEMA pipeline, resulting in 17,194, 7,235 and 5,261 unique ASVs/OTUs for COI, 18S and ITS, respectively. In this dataset, ARMS revealed the presence of over 61 eukaryotic phyla, aligning with our previous sampling campaign. Amongst these phyla, 35 had sequences identified to the species level. With this dataset and its associated paper, we provide a standardised resource for marine biodiversity monitoring and scientific analyses of benthic biodiversity. The presented data product supports future studies on the status and changes in species composition, distribution and genetic diversity