2.1. Samples
The study included ten sediment samples from different deep-sea areas (Appendix 1, Table 1), totaling five stations: four in the Atlantic Ocean and one in the Mediterranean Sea (see Fig. 1, Table 1). Standardized sampling was performed using a Multicorer or Pushcorer (both with cores of 20 cm2) and slicing under sterile conditions. For this study, only the first two layers of sediment (0-1 cm and 1-3 cm) were used for each station. Samples were frozen at -80°C immediately after recovery and slicing for later extraction. DNA extraction was performed using ~10 g of substrate with the DNeasy PowerSoil Kit (Qiagen, Hilden, Germany) following the manufacturer’s protocols. Extraction controls were included (empty sampling bags conditioned onboard and rinsed with water and manufacturer tubes initially filled with sterile water instead of sediment). Final extracts were concentrated three times with 70% ethanol for precipitation reaction and diluted in molecular grade water.