Downward particulate organic carbon export at high temporal resolution in the eastern Fram Strait: Influence of Atlantic Water on flux composition

Abstract

A sediment trap was deployed at 340 m from April to July 2003 to monitor the downward export of particulate organic carbon (POC) at high temporal resolution in the marginal ice zone of the eastern Fram Strait. Although POC fluxes remained <15 mg m-2 d-1, variations in the magnitude and composition of the exported POC were observed during deployment. A first period of elevated POC export associated with an increase in diatom fluxes and low zooplankton fecal pellet fluxes was recorded at the beginning of May, suggesting a mismatch between phytoplankton production and zooplankton grazing. A second period of elevated POC export composed of coccolithophores, diatom resting spores and empty diatom frustules was observed in June. This transition in the composition of the export fluxes reflected a shift in water masses caused by the onset of an ice-edge eddy bringing warm Atlantic Water into the region at the beginning of June. The cyclonic eddy also contributed to the rapid export of Phaeocystis pouchetii, a microalga that does not significantly contribute to carbon export in stratified waters. The main contributors to the zooplankton fecal pellet flux also varied according to the prevailing water mass, with copepod fecal pellets dominating throughout the deployment, except at the beginning of June, when the fecal pellet flux in Atlantic Water was dominated by appendicularian fecal pellets. These results indicate that a prevalence of Atlantic Water may have a large impact on the magnitude and composition of POC export in the eastern Fram Strait. © 2011 Inter-Research.