Phytoplankton responses to dust addition in the Fe–Mn co-limited eastern Pacific sub-Antarctic differ by source region

The seasonal availability of light and micronutrients strongly regulates productivity in the Southern Ocean, restricting biological utilization of macronutrients and CO(2) drawdown. Mineral dust flux is a key conduit for micronutrients to the Southern Ocean and a critical mediator of multimillennial...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences
Main Authors: Wyatt, Neil J., Birchill, Antony, Ussher, Simon, Milne, Angela, Bouman, Heather A., Shoenfelt Troein, Elizabeth, Pabortsava, Katsiaryna, Wright, Alan, Flanagan, Oliver, Bibby, Thomas S., Martin, Adrian, Moore, C. Mark
Format: Text
Language:English
Published: National Academy of Sciences 2023
Subjects:
Biological Sciences
Antarctic
Pacific
Southern Ocean
Antarc*
Online Access:http://www.ncbi.nlm.nih.gov/pmc/articles/PMC10334728/
http://www.ncbi.nlm.nih.gov/pubmed/37399381
https://doi.org/10.1073/pnas.2220111120
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Summary:The seasonal availability of light and micronutrients strongly regulates productivity in the Southern Ocean, restricting biological utilization of macronutrients and CO(2) drawdown. Mineral dust flux is a key conduit for micronutrients to the Southern Ocean and a critical mediator of multimillennial-scale atmospheric CO(2) oscillations. While the role of dust-borne iron (Fe) in Southern Ocean biogeochemistry has been examined in detail, manganese (Mn) availability is also emerging as a potential driver of past, present, and future Southern Ocean biogeochemistry. Here, we present results from fifteen bioassay experiments along a north–south transect in the undersampled eastern Pacific sub-Antarctic zone. In addition to widespread Fe limitation of phytoplankton photochemical efficiency, we found further responses following the addition of Mn at our southerly stations, supporting the importance of Fe–Mn co-limitation in the Southern Ocean. Moreover, addition of different Patagonian dusts resulted in enhanced photochemical efficiency with differential responses linked to source region dust characteristics in terms of relative Fe/Mn solubility. Changes in the relative magnitude of dust deposition, combined with source region mineralogy, could hence determine whether Fe or Mn limitation control Southern Ocean productivity under future as well as past climate states.

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