The SNOWMAN: a new experimental device to study quantitatively the link between phytoplankton community structure, the dynamics of marine snow formation and export time lag.

Emmanuel Christian Laurenceau-Cornec1, Alan Henderson2, Chris Young3, Matthieu Bressac1, Robert F Strzepek4, Lennart Thomas Bach1, Brivaëla Moriceau5, Jordan Toullec6 and Philip W. Boyd7, (1)University of Tasmania, Institute for Marine and Antarctic Studies, Ecology and Biodiversity, Hobart, TAS, Australia, (2)University of Tasmania, TAS, Australia, (3)Australian Antarctic Division, TAS, Australia, (4)University of Tasmania, Antarctic Gateway Partnership, Institute for Marine and Antarctic Studies (IMAS), Hobart, TAS, Australia, (5)CNRS, LEMAR, IUEM Institut Universitaire Européen de la Mer, Plouzané, France, (6)University of Western Brittany, Plouzané, France, (7)Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS, Australia
Our difficulties to fully understand the in situ processes driving the efficiency of the Biological Carbon Pump (BCP) are in part due to our inability to simulate it experimentally under controlled conditions. Phytoplankton coagulation and the subsequent sinking of marine snow from the surface ocean governs the strength of the BCP by regulating the fraction of the biomass produced in the euphotic zone that will be efficiently exported to the mesopelagic. To date coagulation has been studied experimentally using cylindrical rolling tanks or Couette devices. However, their confinement of the particle assemblage restricts their use to non-quantitative studies because it forces large sinking aggregates, that would in nature be exported downward, to keep participating in coagulation processes.

The SNOWMAN (Simulator of Non-finite Open-Wheeled Marine Aggregation and siNking) has been developed to address these limitations, and explore quantitatively the links between plankton community structure, the kinetics of marine snow formation and export timing. The design of the SNOWMAN consists of an innovative double tank apparatus with an open-wheel system. It permits traditional marine particle aggregation by differential settling in the inner perforated tank but also enables the continuous export of the largest aggregates by sinking in a second compartment connected to a settling column. We present here for the first time quantitative experimental data of the influence of phytoplankton community, variations in aggregation kinetics and export timing and provide new insights into the relationship between community structure and the time lag of export flux. We demonstrate the potential of the SNOWMAN for marine snow studies (e.g. zooplankton interactions, microbial degradation, contaminant incorporation) and demonstrate how it can improve our understanding of the complex lever that ecosystem structure exerts on the spatio-temporal variations of the BCP.