A carbon budget for a naturally iron fertilized bloom in the Southern Ocean

Paul J. Morris*, Richard Sanders

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

9 Citations (Scopus)

Abstract

Subantarctic islands in the high-nutrient, low-chlorophyll (HNLC) Southern Ocean are natural sources of iron and stimulate blooms in their proximity, such as the one observed close to the Crozet Islands (52 degrees E, 46 degrees S). During 2004/2005, particulate organic carbon (POC) export was measured using the Th-234 technique in the Crozet bloom and compared with an HNLC control region. Initial results showed that iron release had no effect on daily POC export rates, thus any iron-driven enhancement in POC export was due to a longer export phase in the bloom region when compared to the control region. The duration of the export event was empirically estimated by closing the silicon budget, thus allowing seasonal POC export to be calculated by applying the export duration to the daily rates of POC export. This yields a seasonal estimate of POC export that is 3.6 times larger (range 1.9-7.1) in the iron-fertilized region than in the HNLC control region. These estimates of POC export were then compared to independent estimates of organic matter storage in the upper ocean, which are significant in both the HNLC and control regions. Overall, integrated POC export was significantly (approximately 50%) lower than estimated seasonal new production, the fraction of production that is supported by inputs of new nutrients. Finally, the sequestration efficiency, the numerical relationship between the supply of the limiting nutrient, iron, and the key ecosystem function of POC export at 100 m, is estimated to be 16,790 mol:mol.

Original languageEnglish
Article numberARTN GB3004
Number of pages14
JournalGlobal Biogeochemical Cycles
Volume25
DOIs
Publication statusPublished - 8 Jul 2011

Keywords

  • EXPORT EXPERIMENT CROZEX
  • PRIMARY PRODUCTIVITY
  • MARINE-SEDIMENTS
  • BIOGENIC-SILICA
  • PARTICULATE ORGANIC-MATTER
  • LIGHT INTERACTIONS
  • PHYTOPLANKTON BLOOM
  • ROSS SEA
  • SEA ICE EDGE
  • SEASONAL-CHANGES

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