Identifying the carbon that matters: chemical controls on organic matter aggregation (COMA)

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The Weddell Sea and the adjacent southern Antarctic Circumpolar Current are important contributors to the global primary production and carbon budget. The biological pump and its transport of particulate organic matter (POM) from the photic zone to the ocean floor and the formation and downward transfer of CO2 and recalcitrant dissolved organic matter (DOM) in the Southern Ocean are key regulators of the transfer of atmospheric CO2 to long-term storage of carbon. DOM undergoes aggregation and binds to particles (e.g., cells, faecal pellets and detritus), which contributes to deposition and sequestration of carbon and creates a major sink in the global carbon cycle. Despite of this significant role of aggregation, very little is known about the accumulation rates and binding of low molecular organic matter and colloidal matter. To study the transition between dissolved, colloidal and particulate organic matter, this SPP1158 proposal “Identifying the carbon that matters: chemical controls on organic matter aggregation (COMA)” focusses on organic matter from surface seawater. Samples will be taken on the Polarstern expeditions HAFOS (Hybrid Antarctic Float and Ocean Observatory) during the Austral summer / autumn of 2022 and "IslandImpact" during the Austral spring of 2022. Samples will be chemically characterized and tested for their aggregation behaviour and rates. These analytical data can then be integrated with environmental data and measured export fluxes from the expeditions in order to draw conclusions about the polar carbon cycle. The COMA project addresses central themes of the SPP1158 programme, namely to achieve a better understanding of biological carbon pump of the Southern Ocean and assessment of processes that contribute to the long term storage of atmospheric CO2.