Southern Ocean Iron Enrichment Experiment: Carbon Cycling in High- and Low-Si Waters

Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Science (Impact Factor: 33.61). 05/2004; 304(5669):408-14. DOI: 10.1126/science.1089778
Source: PubMed


The availability of iron is known to exert a controlling influence on biological productivity in surface waters over large areas of the ocean and may have been an important factor in the variation of the concentration of atmospheric carbon dioxide over glacial cycles. The effect of iron in the Southern Ocean is particularly important because of its large area and abundant nitrate, yet iron-enhanced growth of phytoplankton may be differentially expressed between waters with high silicic acid in the south and low silicic acid in the north, where diatom growth may be limited by both silicic acid and iron. Two mesoscale experiments, designed to investigate the effects of iron enrichment in regions with high and low concentrations of silicic acid, were performed in the Southern Ocean. These experiments demonstrate iron's pivotal role in controlling carbon uptake and regulating atmospheric partial pressure of carbon dioxide.

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Available from: Michal Koblizek, Dec 27, 2013
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    • "If the entire Southern Ocean was fertilized (one event), the resulting increase in C fixation would be 585 million tonnes (t). Approximately 30 % of the Southern Ocean contains Si concentrations high enough to Fig. 1 Oceanic concentrations of nitrate in lmol/L (Garcia et al. 2010) Mine Water Environ (2015) 34:105–111 107 support a diatom bloom (Coale et al. 2004). If half of the C fixed in the diatom blooms sank to the ocean floor, the total C sequestration would be 88 million t. "
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    ABSTRACT: Approximately 30 % of the Earth's oceans support low rates of primary production because of low Fe concentrations. The fertilization of these waters with Fe has been proposed as a tool for creating phytoplankton blooms, increasing carbon fixation, and sequestering carbon in deep ocean waters. This paper reviews the status of the ocean iron fertilization (OIF) concept and assesses the opportunity it may provide to mining companies and mine water professionals who regularly deal with large quantities of Fe. Using data produced by large OIF experiments, calculations are provided regarding the efficiency of Fe additions for carbon fixation and the quantities of Fe that would be needed if OIF became an accepted practice. The gross value of Fe used in OIF projects is calculated from the current value of carbon credits and salmon and tuna fisheries. If the OIF concept advances, the huge demand for Fe that will be created may justify reconsideration of mine water treatment practices that produce more pure Fe solids than is the case with conventional treatment technologies.
    Mine Water and the Environment 03/2014; 34(1):105-111. DOI:10.1007/s10230-014-0305-5 · 1.21 Impact Factor
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    • "The continuous release was performed to create a quasi-stationary tracer field in the ocean. Wannikhof et al. [68] notes this application adds to the utility of the tracer, which had only previously been used as a tracer of gas exchange processes in the ocean [70]-[72], lakes [73] [74], and in rivers [75]; as a surface water dispersion tracer [76], as a tag for surface water in Lagrangian studies ([77]-[79]; and to determine mixing in the deep ocean [80] [81]. Because Wannikhof et al. [68] noted success with the Hollywood tracer in June 2004, a second tracer study of the Boynton outfall was conducted in 2007. "
    Journal of Environmental Protection 01/2014; 05(11):1037-1052. DOI:10.4236/jep.2014.511103
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    • "The low abundances of F. cylindrus in Fe-depleted treatments probably reflect the rather high sensitivity of this species towards Fe limitation [43], which could be due to low Fe uptake capacities observed for this species [21]. In contrast, Pseudo-nitzschia has been shown to be an efficient user of Fe under limiting concentrations [58] and sporadic Fe input events [59]. Interestingly, the final proportion of Pseudo-nitzschia declined strongly with increasing pCO2, irrespectively of the Fe status (Table 3), suggesting that its growth rates must have been significantly lower than those of the dominant species (F. "
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    ABSTRACT: The potential interactive effects of iron (Fe) limitation and Ocean Acidification in the Southern Ocean (SO) are largely unknown. Here we present results of a long-term incubation experiment investigating the combined effects of CO2 and Fe availability on natural phytoplankton assemblages from the Weddell Sea, Antarctica. Active Chl a fluorescence measurements revealed that we successfully cultured phytoplankton under both Fe-depleted and Fe-enriched conditions. Fe treatments had significant effects on photosynthetic efficiency (Fv/Fm; 0.3 for Fe-depleted and 0.5 for Fe-enriched conditions), non-photochemical quenching (NPQ), and relative electron transport rates (rETR). pCO2 treatments significantly affected NPQ and rETR, but had no effect on Fv/Fm. Under Fe limitation, increased pCO2 had no influence on C fixation whereas under Fe enrichment, primary production increased with increasing pCO2 levels. These CO2-dependent changes in productivity under Fe-enriched conditions were accompanied by a pronounced taxonomic shift from weakly to heavily silicified diatoms (i.e. from Pseudo-nitzschia sp. to Fragilariopsis sp.). Under Fe-depleted conditions, this functional shift was absent and thinly silicified species dominated all pCO2 treatments (Pseudo-nitzschia sp. and Synedropsis sp. for low and high pCO2, respectively). Our results suggest that Ocean Acidification could increase primary productivity and the abundance of heavily silicified, fast sinking diatoms in Fe-enriched areas, both potentially leading to a stimulation of the biological pump. Over much of the SO, however, Fe limitation could restrict this possible CO2 fertilization effect.
    PLoS ONE 12/2013; 8(11):e79890. DOI:10.1371/journal.pone.0079890 · 3.23 Impact Factor
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