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).