Dataset: Niskin bottle metadata and environmental measurements associated with bacterial DNA samples collected from January to February 2022 during RVIB Nathaniel B. Palmer cruise NBP 22-02 in the Amundsen Sea Embayment

Water samples were collected aboard R/V Nathaniel B. Palmer during NBP 22-02 (January to March 2022) in the Amundsen Sea, Antarctica. Water sampling was conducted with a profiling rosette of 24 12-liter (L) Niskin bottles equipped with an SBE 911CTD (conductivity-temperature-depth recorder; Sea-Bird Scientific, Bellevue, WA, USA) with additional chlorophyll a (Chl-a) fluorescence (ECO FLRTD-1482; WETLabs, Philomath, OR, USA) and dual dissolved oxygen sensors (SBE43 Sea-Bird Scientific, Bellevue, WA, USA). At each of 21 stations (January 15 - February 25, 2022), seawater samples were collected by Niskin bottle from 3 to 6 depths (2 to 1271 meters (m)), including Antarctic Surface Water (AASW) within the surface mixed layer, intermediate Winter Water (WW), and near-bottom Circumpolar Deep Water (CDW; Randall-Goodwin et al., 2015).

Nutrient samples for nitrate, nitrite, ammonia, and phosphate were collected at the same stations and depths from the profiling rosette/CTD used to collect DNA samples, filtered (0.45-micrometer (µm)), frozen (-80 degrees Celsius), and analyzed at the Oceanographic Data Facility (ODF) Chemistry Laboratory at Scripps Institution of Oceanography, University of California San Diego (Becker et al., 2019). Water column Chl a samples were filtered onto 45-millimeter (mm) GFF filters, dried, and flash frozen (-80 degrees Celsius), and transported back to Georgia where the concentration was measured using acetone extraction and a spectrofluorometer (Knap et al., 1994). Meltwater fraction was determined using oxygen isotope ratios of seawater samples collected and measured (British Antarctic Survey; Meredith et al., 2008) in combination with temperature, salinity, and dissolved oxygen (Randall-Goodwin et al., 2015). Dissolved iron (dFe) samples were also collected at similar stations and depths (using a Trace-Metal Clean CTD that was deployed immediately after the conventional CTD) and analyzed by the Sherrell lab at Rutgers University using standard protocols (Sherrell et al., 2015; Chinni et al., 2026).