Strong contribution of diatom resting spores to deep-sea carbon transfer in naturally iron-fertilized waters downstream of South Georgia

Biogeochemical and diatom export fluxes are presented from two bathypelagic sediment trap deployments in the Antarctic Zone of the Southern Ocean. One of the sediment traps was deployed in very productive, naturally iron-fertilized waters downstream of South Georgia (P3, 2000m) and compared to a dep...

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Bibliographic Details
Published in:Deep-sea research. Part I, Oceanographic research papers Oceanographic research papers, 2016-09, Vol.115, p.22-35
Main Authors: Rembauville, M., Manno, C., Tarling, G.A., Blain, S., Salter, I.
Format: Article
Language:English
Subjects:
Algae
Antarctica
Biogeochemistry
Biological oceanography
Biomass
Carbon
Carbon export
Chaetoceros
Deep sea
Diatom resting spores
Earth Sciences
Exports
Fluxes
Fragilariopsis kerguelensis
International trade
Marine
Natural iron fertilization
Oceanography
Plankton
Sciences of the Universe
Sediment transport
Sediments
Southern Ocean
Spores
Thalassiosira antarctica
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Summary:Biogeochemical and diatom export fluxes are presented from two bathypelagic sediment trap deployments in the Antarctic Zone of the Southern Ocean. One of the sediment traps was deployed in very productive, naturally iron-fertilized waters downstream of South Georgia (P3, 2000m) and compared to a deployment in moderately productive waters upstream of the island system (P2, 1500m). At both sites significant diatom export events occurred in spring (November) and contained mostly empty cells that were associated with low particulate organic carbon (POC) fluxes. A summer export pulse occurred one month later at P2 (end February/March) compared to P3 (end January). Diatom fluxes at P3 were one order of magnitude higher than at P2, a difference mainly attributed to the short and intense export of resting spores from Chaetoceros Hyalochaete and Thalassiosira antarctica species. Aside from these resting spores, diatom export assemblages at both sites were dominated by empty Fragilariopsis kerguelensis frustules. The fraction of diatoms exported as empty frustules was considerably lower at P3 (52%) than P2 (91%). This difference was related to the flux of intact diatom resting spores at P3 and may partially explain the lower Si:C export stoichiometry observed at P3 (1.1) compared to P2 (1.5). Through the enumeration of full diatom frustules and subsequent biomass calculations we estimate that diatom resting spores account for 42% of annual POC flux in the productive waters downstream of South Georgia. At both sites the contribution of diatom vegetative stages to POC fluxes was considerably lower (
ISSN:0967-0637
1879-0119
DOI:10.1016/j.dsr.2016.05.002