USAP-DC

Phytoplankton, or microscopic marine algae, are an important part of the carbon cycle and can lower the rates of atmospheric carbon dioxide by transferring the atmospheric carbon into the oceans. The concentration of phytoplankton in the Southern Ocean is regularly limited by the availability of marine iron. This in turn influences the rate of carbon transfer from the atmosphere to the ocean. The primary source of iron in the Southern Ocean is eroded continental rock. Understanding the current and future sources of iron to the Southern Ocean as a result of increased melting of terrestrial glaciers is necessary for predicting future concentrations of Southern Ocean phytoplankton and the subsequent influence on the carbon cycle. A poorly understood source of iron to the Southern Ocean is stream input from ice-free regions such as the McMurdo Dry Valleys in Antarctica. This source of iron is likely to become larger if glaciers retreat. This study investigates the sources and amount of iron transported by McMurdo Dry Valley streams directly into the Southern Ocean. Because not all forms of iron can be used by phytoplankton, experiments will be performed to determine how available iron is to phytoplankton and how iron mixes with seawater. Immersive 360-degree video, infographics, and educational videos of findings from this project will be shared on social media, at schools and science events, and in an urban science center.

In the Southern Ocean (SO) there is an excess of macronutrients but regional primary production is limited or co-limited due to iron. An addition of iron to the ocean will affect biochemical cycles, increase primary production, and affect the structure and composition of phytoplankton communities in the SO. Iron flux to the SO is globally significant, as increased Fe fertilization leads to increased carbon sequestration which acts as a negative feedback to increased atmospheric pCO2. One source of potentially bioavailable iron to the coastal regions of the SO is from direct sub-aerial stream discharge in ice-free areas of Antarctica, a source that may become more important if terrestrial glaciers retreat. It is imperative to understand the source, nature, potential fate, and flux of iron to the SO if better predictive models for the carbon cycle and atmospheric chemistry are to be developed. This project will investigate in-stream processes and characteristics controlling dissolved iron draining into the Ross Sea including photoreduction, temperature, and complexation with organic matter. The novel study will quantify bioavailability of particulate iron and bioavailability of dissolved iron in Antarctic in streams draining into the SO. On-site speciation measurements will be performed on dissolved iron species, particulate iron speciation will be determined using high-resolution spectroscopy, mixing experiments will be performed with coastal marine water, and the bioavailability of Fe will be determined through marine bioassays. This project will provide two students with valuable Antarctic field experience and reach thousands of individuals through existing partnerships with K-12 schools, public STEM events, an urban science center, and a strong social media presence.

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.

Person	Role
Lyons, W. Berry	Investigator and contact
Gardner, Christopher B.	Co-Investigator

Antarctic Earth Sciences

Award # 1841228

USAP-1841228_1

Deployment	Type
New Harbour	field camp

None in the Database

Repository	Title (link)	Format(s)	Status
USAP-DC	Commonwealth Stream Diel Water Chemistry	Microsoft Excel (OpenXML)	exists
USAP-DC	Hyporheic zone geochemistry of Wales Stream, Taylor Valley, Antarctica	Microsoft Excel (OpenXML)	exists
USAP-DC	isotopic signature of massive buried ice, eastern Taylor Valley, Antarctica	Microsoft Excel (OpenXML)	exists

1. Gardner, C.B, Diaz, M.A., Smith, D.F., Fountain, A.G., Levy, J.S., and Lyons, W.B. (2022) Isotopic signature of massive, buried ice in Eastern Taylor Valley, Antarctica: Implications for its origin. Arctic, Antarctic, and Alpine Research, 54(1), 335-345. (doi:10.1080/15230430.2022.2102510)