Attenuation of particulate organic carbon flux in the Scotia Sea, Southern Ocean, is controlled by zooplankton fecal pellets

E L Cavan,F A C Le Moigne,R J Sanders,C J Daniels,A J Poulton,G A Tarling,G M Fragoso,P Ward

doi:10.1002/2014gl062744

E L Cavan, F A C Le Moigne + Show 6 more

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https://doi.org/10.1002/2014gl062744

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Abstract

AbstractThe Southern Ocean (SO) is an important CO2 reservoir, some of which enters via the production, sinking, and remineralization of organic matter. Recent work suggests that the fraction of production that sinks is inversely related to production in the SO, a suggestion that we confirm from 20 stations in the Scotia Sea. The efficiency with which exported material is transferred to depth (transfer efficiency) is believed to be low in high‐latitude systems. However, our estimates of transfer efficiency are bimodal, with stations in the seasonal ice zone showing intense losses and others displaying increases in flux with depth. Zooplankton fecal pellets dominated the organic carbon flux and at stations with transfer efficiency >100% fecal pellets were brown, indicative of fresh phytodetritus. We suggest that active flux mediated by zooplankton vertical migration and the presence of sea ice regulates the transfer of organic carbon into the oceans interior in the Southern Ocean.

Highlights

The biological carbon pump (BCP) transfers carbon from the surface to the deep ocean [Eppley and Peterson, 1979] via the sinking of organic carbon produced in the surface
We suggest that active flux mediated by zooplankton vertical migration and the presence of sea ice regulates the transfer of organic carbon into the oceans interior in the Southern Ocean
Stations south of 60°S were in the seasonal ice zone (SIZ), and one station (12, >15% ice cover) was in the marginal ice zone (MIZ) [Tarling, 2013]

Summary

Introduction

The biological carbon pump (BCP) transfers carbon from the surface to the deep ocean [Eppley and Peterson, 1979] via the sinking of organic carbon produced in the surface. Remineralization of particulate organic carbon (POC) to CO2 by bacteria and zooplankton means that only a small fraction of this flux reaches the interior with the depth distribution of remineralization controlling atmospheric CO2 levels [Kwon et al, 2009]. The Southern Ocean (SO) accounts for ~20% of the global ocean CO2 uptake [Takahashi et al, 2002; Park et al, 2010], with biological processes being responsible for seasonal variations in air-sea flux of CO2. Iron from oceanic islands and melting sea ice can cause intense phytoplankton blooms, which may lead to high POC export [Pollard et al, 2009]

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