SAMPLE COLLECTION FOR MICROBIOLOGY

The PARIS-Sud group collected two types of samples, seawater and sediment, in two main locations, the Ionian Sea and the Sea of Marmara.

Seawater samples were mainly obtained through CTD casting. 240 liters of seawater per CTD were collected for a total of 5 CTD castings (see Table ). Samples were taken at different depths, with the largest volumes collected at deep-sea waters (3000 to 3500 m in the Ionian Sea) or at the proximity of the observatory SN4 (154 m depth) in Marmara. Seawater was subsequently filtered through different pore-size filters (200, 20, 5 and 0.22 $\mu$m in diameter) to analyze various components of the microbial communities, from protists to prokaryotes and picoeukaryotes. Different fixation protocols were subsequently applied (see table). In addition, surface seawater samples (5l) were taken from the vessel in order to have a transect along the Italian Ionian Sea and the Sea of Marmara. Cells were concentrated for subsequent flow cytometry analyses.

Sediment samples (ca. 50 ml) were taken from the upper and lower part of cores taken from the Ionian Sea and the Marmara Sea (see attached table). Different sediment fractions were either frozen in liquid nitrogen or fixed using different protocols for subsequent analyses.