Supplementary Data of Chapter 8 of the PhD thesis entitled "Novel insights into the Ecology of the Microbial Rare Biosphere in the Arctic Ocean through the combination of Microbiome DNA sequencing and Machine Learning Approaches", by Francisco Pascoal, under the supervision of Professor Catarina Magalhães, Professor Rodrigo Costa, and Professor Paula Branco. This PhD thesis was carried out in the Biology PhD program of the Faculty of Sciences of the University of Porto. The Supplementary Data made available in here refers to: Supplementary Data 8.1. Metadata of the samples from the Environmental Monitoring of Svalbard and Jan Mayen (MOSJ) program, with data ranging from 2016 to 2020, focusing specifically on the Kongsfjorden transect. This metadata was based both on Pascoal et al., (2025) and Wold et al., (2024). File name: "Metadata_MOSJ2016_2020_Pascoal_et_al_2025.xlsx" Supplementary Data 8.2. Association rules obtained from the association rule mining algorithm. File name: "Dependent_rules_Pascoal_et_al_2025.xlsx" References: Pascoal, F. et al. (2025) “Definition of the microbial rare biosphere through unsupervised machine learning,” Communications Biology (in peer-review) [Preprint]. Wold, A., Assmy, P. and Duarte, P. (2024) “ Biogeochemistry data from Kongsfjorden and Rijpfjorden 2011 to 2020 [Data set].” Norwegian Polar Institute.