USAP-DC

Intellectual Merit:
Sinking particles are a major element of the biological pump and they are commonly assigned to two fates: mineralization in the water column and accumulation at the seafloor. However, there is another fate of export hidden within the vertical decline of carbon, the transformation of sinking organic matter to fine suspended and/or dissolved organic fractions. This process has been suggested but has rarely been observed or quantified. As a result, it is presumed that the solubilized fraction is largely mineralized over short time scales. However, global ocean surveys of dissolved organic carbon are demonstrating a significant water column accumulation of organic matter under high productivity environments. This proposal will investigate the transformation of organic particles from sinking to solubilized phases of the export flux in the Ross Sea. The Ross Sea experiences high export particle production, low dissolved organic carbon export with overturning circulation, and the area has a predictable succession of production and export events. In addition, the basin is shallow (< 000 m) so the products the PIs will target are relatively concentrated. To address the proposed hypothesis, the PIs will use both well-established and novel biochemical and optical measures of export production and its fate. The outcomes of this work will help researchers close the carbon budget in the Ross Sea.

Broader impacts:
This research will support graduate and undergraduate students and will provide undergraduates and pre-college students with field-based research experience. Scientifically, this research will increase understanding of carbon sinks in the Ross Sea and will help develop new tools for identifying, quantifying, and tracking that carbon. The PIs will interface with K-12 students through daily reports from the field and through educational modules developed by several of the PIs in collaboration with science education specialists and college students. A K-12 educator will be included on the research cruises. Outreach will be through COSEE Florida and the Maritime Center in Norfolk, VA.

Person	Role
Bochdansky, Alexander	Investigator
Dunbar, Robert	Investigator
DiTullio, Giacomo	Investigator
Ditullio, Giacomo	Investigator
Harry, Dennis L.	Investigator
HANSELL, DENNIS	Investigator

Antarctic Ocean and Atmospheric Sciences	Award # 1142117
Antarctic Ocean and Atmospheric Sciences	Award # 1142097
Antarctic Ocean and Atmospheric Sciences	Award # 1142065
Antarctic Ocean and Atmospheric Sciences	Award # 1142044

NSF-ANT11-42117
NSF-ANT11-42065
NSF-ANT11-42044
NSF-ANT11-42097_1
Phaeocystis_colonies_DIHM_1
Video_particle_profiler_data_NBP1302_1

Deployment	Type
NBP1302	ship expedition

None in the Database

Repository	Title (link)	Format(s)	Status
USAP-DC	Video Particle Profiler (VPP) and Digital Inline Holographic Microscopy (DIHM) data from cruise NBP1302	None	exist
BCO-DMO	Carbon chemistry from CTD	None	exist
BCO-DMO	Deployment: NBP1302	None	exist
R2R	NBP1302 data	None	exist

1. Bochdansky, A. B., M. A. Clouse, D. A. Hansell (2016) Mesoscale and high-frequency variability of macroscopic particles (> 100 micrometer) in the Ross Sea and its relevance for late-season particulate carbon export. Journal of Marine Systems (Ross Sea Special Issue) 166: 120-131. (doi:10.1016/j.jmarsys.2016.08.010)
2. DeJong, H. B., Dunbar, R. B., Mucciarone, D., & Koweek, D. A. (2015). Carbonate saturation state of surface waters in the Ross Sea and Southern Ocean: controls and implications for the onset of aragonite undersaturation. Biogeosciences, 12(23), 6881–6896. (doi:10.5194/bg-12-6881-2015)
3. DeJong, H. B., Dunbar, R. B., Mucciarone, D. A., & Koweek, D. A. (2015). Carbonate saturation state of surface waters in the Ross Sea and Southern Ocean: controls and implications for the onset of aragonite undersaturation. Biogeosciences Discussions, 12(11), 8429–8465. (doi:10.5194/bgd-12-8429-2015)
4. Bercovici, S. K., McNichol, A. P., Xu, L., & Hansell, D. A. (2018). Radiocarbon Content of Dissolved Organic Carbon in the South Indian Ocean. Geophysical Research Letters, 45(2), 872–879. (doi:10.1002/2017gl076295)
5. DeJong, H. B., & Dunbar, R. B. (2017). Air‐Sea CO2 Exchange in the Ross Sea, Antarctica. Journal of Geophysical Research: Oceans, 122(10), 8167–8181. (doi:10.1002/2017jc012853)
6. DeJong, H. B., Dunbar, R. B., & Lyons, E. A. (2018). Late Summer Frazil Ice‐Associated Algal Blooms around Antarctica. Geophysical Research Letters, 45(2), 826–833. (doi:10.1002/2017gl075472)
7. St John Glew, K., Espinasse, B., Hunt, B. P. V., Pakhomov, E. A., Bury, S. J., Pinkerton, M., … Trueman, C. N. (2021). Isoscape Models of the Southern Ocean: Predicting Spatial and Temporal Variability in Carbon and Nitrogen Isotope Compositions of Particulate Organic Matter. Global Biogeochemical Cycles, 35(9). (doi:10.1029/2020gb006901)
8. DeJong, H. B., Dunbar, R. B., Koweek, D. A., Mucciarone, D. A., Bercovici, S. K., & Hansell, D. A. (2017). Net community production and carbon export during the late summer in the Ross Sea, Antarctica. Global Biogeochemical Cycles, 31(3), 473–491. (doi:10.1002/2016gb005417)