3.4 Bottom water, pore water and sediment sampling
Pore water and bottom water samples for this study were collected from a multicore deployment near Station PS3 in the Tasman Sea (Figure 1, 3349 m water depth). Cores for pore water, bottom water, and sediment samples were processed in an N2 environment. A bottom water sample was extracted from the core tube approximately 10 cm above the sediment-water interface using an acid-cleaned rubber-free syringe and filtering through a 0.45 µm syringe filter into an acid-cleaned LDPE bottle. The bottom water was visibly clear and free from sediment resuspension, and the sediment surface appeared undisturbed.
Pore water samples were collected following procedures outlined in Abbott et al. (2015). In brief, 1 cm depth intervals were placed into acid-cleaned centrifuge tubes in a glove bag, sealed, then centrifuged at 4500 rpm for 20 minutes. The pore water (supernatant) was extracted from centrifuged samples and filtered as outlined for bottom water. The samples were acidified, stored and analyzed for [Cr] by isotope dilution as described in section 3.6. Centrifuged sediments were stored frozen until freeze-dried, then analyzed for bulk composition (CaCO3, organic matter, lithogenic material; supplemental material).