Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
  • BCO-DMO Processing Description
• Data Files
• Related Publications
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

Field sampling:
Ice samples for primary production measurements were collected mid-morning from 6 stations along the western Antarctic Peninsula in November and December of 2019 on board the R/V Nathaniel B. Palmer along a north-south transect from 64.8°S to 67.8°S. For Stations (Stns) 2 and 3, the ice was "rotten" (sufficiently melted to be disintegrating structurally, present only in small pieces) and collected as an ice–seawater slurry so no profile was collected. Stns 4 and 7 were rafted floes with a flooded internal layer, with Stn 7 > square meters (m²) in size. Stns 5 and 6 were on landfast sea ice, where the algae were collected from the bottom 10 centimeters (cm) of the ice. At these 4 stations (Stns 4-7), ice cores were taken with a 7.5 cm Kovacs corer separated by at least 1 meter (m) horizontally. At Stns 5-7, "physical cores" were taken and temperature was measured with a digital thermometer with a probe at 5 cm intervals along physical cores, which were then cut into 5 cm sections and placed in separate Whirlpak bags for conductivity measurements measured with both a refractometer and conductivity probe after melting. Brine volumes and salinity were calculated from bulk salinity and temperature (Frankenstein and Garner 1967; Cox and Weeks 1986).

Measured temperature was used to calculate brine salinity according to Cox and Weeks (1986). Brine salinity and measured bulk salinity were used to calculate brine volume using Frankenstein and Garner (1967).

- Imported original file "Phys_cores_Temp_Sal.xlsx" into the BCO-DMO system.
- Flagged '*', 'NA', and '#VALUE!' as missing data values (missing data are blank/empty in the final CSV file).
- Concatenated data from separate sheets (one per core) into one dataset, creating columns for Station and Core.
- Renamed fields to comply with BCO-DMO naming conventions.
- Added columns for station Latitude, Longitude, and Date as provided in the metadata.
- Saved the final file as "913655_v1_physical_profiles.csv".

NSF Award Abstract
Rapid changes in the extent and thickness of sea ice during the austral spring subject microorganisms within or attached to the ice to large fluctuations in temperature, salinity, light and nutrients. This project aims to identify cellular responses in sea-ice algae to increasing temperature and decreasing salinity during the spring melt along the western Antarctic Peninsula and to determine how associated changes at the cellular level can potentially affect dynamic, biologically driven processes. Understanding how sea-ice algae cope with, and are adapted to, their environment will not only help predict how polar ecosystems may change as the extent and thickness of sea ice change, but will also provide a better understanding of the widespread success of photosynthetic life on Earth. The scientific context and resulting advances from the research will be communicated to the general public through outreach activities that includes work with Science Communication Fellows and the popular Polar Science Weekend at the Pacific Science Center in Seattle, Washington. The project will provide student training to college students as well as provide for educational experiences for K-12 school children.

There is currently a poor understanding of feedback relationships that exist between the rapidly changing environment in the western Antarctic Peninsula region and sea-ice algal production. The large shifts in temperature and salinity that algae experience during the spring melt affect critical cellular processes, including rates of enzyme-catalyzed reactions involved in photosynthesis and respiration, and the production of stress-protective compounds. These changes in cellular processes are poorly constrained but can be large and may have impacts on local ecosystem productivity and biogeochemical cycles. In particular, this study will focus on the thermal sensitivity of enzymes and the cycling of compatible solutes and exopolymers used for halo- and cryo-protection, and how they influence primary production and the biogeochemical cycling of carbon and nitrogen. Approaches will include field sampling during spring melt, incubation experiments of natural sea-ice communities under variable temperature and salinity conditions, and controlled manipulation of sea-ice algal species in laboratory culture. Employment of a range of techniques, from fast repetition rate fluorometry and gross and net photosynthetic measurements to metabolomics and enzyme kinetics, will tease apart the mechanistic effects of temperature and salinity on cell metabolism and primary production with the goal of quantifying how these changes will impact biogeochemical processes along the western Antarctic Peninsula.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.