USAP-DC

Phytoplankton blooms in the coastal waters of the Ross Sea, Antarctica are typically dominated by either diatoms or Phaeocystis Antarctica (a flagellated algae that often can form large colonies in a gelatinous matrix). The project seeks to determine if an association of bacterial populations with Phaeocystis antarctica colonies can directly supply Phaeocystis with Vitamin B12, which can be an important co-limiting micronutrient in the Ross Sea. The supply of an essential vitamin coupled with the ability to grow at lower iron concentrations may put Phaeocystis at a competitive advantage over diatoms. Because Phaeocystis cells can fix more carbon than diatoms and Phaeocystis are not grazed as efficiently as diatoms, the project will help in refining understanding of carbon dynamics in the region as well as the basis of the food web webs. Such understanding also has the potential to help refine predictive ecological models for the region. The project will conduct public outreach activities and will contribute to undergraduate and graduate research. Engagement of underrepresented students will occur during summer student internships. A collaboration with Italian Antarctic researchers, who have been studying the Terra Nova Bay ecosystem since the 1980s, aims to enhance the project and promote international scientific collaborations.

The study will test whether a mutualistic symbioses between attached bacteria and Phaeocystis provides colonial cells a mechanism for alleviating chronic Vitamin B12 co-limitation effects thereby conferring them with a competitive advantage over diatom communities. The use of drifters in a time series study will provide the opportunity to track in both space and time a developing algal bloom in Terra Nova Bay and to determine community structure and the physiological nutrient status of microbial populations. A combination of flow cytometry, proteomics, metatranscriptomics, radioisotopic and stable isotopic labeling experiments will determine carbon and nutrient uptake rates and the role of bacteria in mitigating potential vitamin B12 and iron limitation. Membrane inlet and proton transfer reaction mass spectrometry will also be used to estimate net community production and release of volatile organic carbon compounds that are climatically active. Understanding how environmental parameters can influence microbial community dynamics in Antarctic coastal waters will advance an understanding of how changes in ocean stratification and chemistry could impact the biogeochemistry and food web dynamics of Southern Ocean ecosystems.

Person	Role
DiTullio, Giacomo	Investigator and contact
Lee, Peter	Co-Investigator

Antarctic Organisms and Ecosystems	Award # 1644073
Antarctic Integrated System Science	Award # 1643684
Antarctic Organisms and Ecosystems	Award # 1643684

USAP-1644073_1

Deployment	Type
NBP1801	ship expedition

CICLOPS_DMP.docx

Repository	Title (link)	Format(s)	Status
R2R	NBP1801 Expedition data	Not Provided	exists
USAP-DC	Algal pigment concentrations from the Ross Sea	Not Provided	exists
USAP-DC	Biogenic silica concentrations from the Ross Sea	Not Provided	exists
USAP-DC	Nutrients from NBP18-01 CICLOPS	Not Provided	exists

1. Oldham, V. E., Chmiel, R., Hansel, C. M., DiTullio, G. R., Rao, D., & Saito, M. (2021). Inhibited Manganese Oxide Formation Hinders Cobalt Scavenging in the Ross Sea. Global Biogeochemical Cycles, 35(5). (doi:10.1029/2020gb006706)
2. DiTullio, G., & Lee, P. (2019). Biogenic silica concentrations collected from CTD casts during RVIB Nathaniel B. Palmer cruise in the Ross Sea, Southern Ocean from 2017-2018. Biological and Chemical Oceanography Data Management Office. (doi:10.1575/1912/bco-dmo.780191.1)
3. DiTullio, G., & Lee, P. (2019). Algal pigment concentrations measured by HPLC from RVIB Nathaniel B. Palmer cruise in the Ross Sea, Southern Ocean from 2017-2018. Biological and Chemical Oceanography Data Management Office. (doi:10.1575/1912/bco-dmo.778881.1)
4. DiTullio, G., & Lee, P. (2020). Hydrographic data collected by CTD during RVIB Nathaniel B. Palmer cruise in the Ross Sea, Southern Ocean from 2017-2018. Biological and Chemical Oceanography Data Management Office. (doi:10.1575/1912/bco-dmo.783911.1)
5. DiTullio, G., & Lee, P. (2019). Algal pigment concentrations measured by HPLC from RVIB Nathaniel B. Palmer cruise in the Ross Sea, Southern Ocean from 2017-2018. Biological and Chemical Oceanography Data Management Office. (doi:10.1575/1912/bco-dmo.778881.2)
6. Kellogg, R. M., Moran, D. M., McIlvin, M. R., Subhas, A. V., Allen, A. E., & Saito, M. A. (2022). Lack of a Zn/Co substitution ability in the polar diatom Chaetoceros neogracile <scp>RS19</scp>. Limnology and Oceanography, 67(10), 2265–2280. Portico. (doi:10.1002/lno.12201)
7. Rao, D., Füssy, Z., Brisbin, M. M., McIlvin, M. R., Moran, D. M., Allen, A. E., Follows, M. J., & Saito, M. A. (2024). Flexible B12 ecophysiology of Phaeocystis antarctica due to a fusion B12–independent methionine synthase with widespread homologues. Proceedings of the National Academy of Sciences, 121(6). (doi:10.1073/pnas.2204075121)