Spatial and Temporal Progression of Phytoplankton-derived Organic Carbon in the Amundsen Sea Polynya, West Antarctica

The Amundsen Sea Polynya (ASP) is one of the largest and most productive polynyas in coastal Antarctica, acting as a sink of atmospheric CO₂. Changes in water circulation are causing rapid thinning of ice shelves and basal melting, which could potentially influence primary production and the carbon cycle in this region. Here, we investigated particulate (POC) and dissolved organic carbon (DOC) distribution using bulk concentrations and δ¹³C-POC to better understand organic carbon (OC) dynamics in the ASP ecosystem. Depth-profile samples (2 m – 732 m) were collected across the polynya (from near to off shelf), and repeatedly at same station after 20 and 30 days during the austral summer of 2022. Our initial results showed that POC and DOC concentrations were generally higher at surface and subsurface waters (235 μg L^-1 and 64.2 μM, respectively) compared to deeper depths (32.5 μg L^-1 and 44.1 μM, respectively). Surface δ¹³C-POC values measured in the polynya (-28.1‰) were more enriched than at deeper depths (-29.3‰), but more depleted than at oceanic stations (-27.8‰), likely due to algal blooms. Over time, depth-profile samples revealed a slight increase in OC concentrations (POC: 20.2 to 44.8 μg L^-1 and DOC: 42.0 to 46.0 μM) and an enriched δ¹³C-POC signature (from -26.6 to -23.8‰), suggesting changes in OC cycling, presumably due to bacterial responses associated with bloom progression and sediment resuspension. Our findings provide new insights into OC dynamics in the ASP, helping us better understand the contributions of coastal polynyas to the global carbon cycle.

Presentation Preference: Poster

Primary Presenter: Giovanna Utsumi, University of Georgia (giovanna.azariasutsumi@uga.edu)

Authors:

Giovanna Utsumi, University of Georgia  (giovanna.azariasutsumi@uga.edu)

Patricia Medeiros, University of Georgia  (medeiros@uga.edu)