Iron fertilization

An extreme iron fertilization scenario modeled by Sarmiento and Orr (1991) relies on the sustained depletion of phosphorus in Southern Ocean surface waters by continuous iron addition. The three-dimensional, multi-layered model predicts a global increase of export production and the possibility of anoxia in deep oceanic waters. Specifically, the results indicate a POC export increase of 6-30 GtCy-1, i.e., a doubling of export production, after 100 years of fertilization. In addition, anoxia is predicted for certain parts of the southwest Indian Ocean. Considering the enormous scale of this hypothesized fertilization operation (0.6Mt utilizable Fey-1 Sarmiento Orr, 1991) and the low spatial resolution of the model, the exercise provides limited insights into more realistic iron fertilization scenarios. 

Because of the potential magnitude and uncertainty of environmental impacts, proposals to fertilize the ocean to mitigate global warming (or to earn carbon credits) have been controversial (e.g. ASLO, 2001 Chisholm etal., 2001  

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The results of two successful iron-fertilization experiments in the eastern equatorial Pacific have clearly shown that phytoplankton growth rate is limited by iron at that location (Martin et al., 1994 Coale et al., 1996). The species composition and size distributions of the ecosystem are influenced by iron availability (Landry et al., 1997). In particular, large diatoms do not grow at optimum rates in the absence of sufficient iron. Loukos et al. (1997) used a simple... 

Coale, K. H., Johnson, K. S., Fitzwater, S. E. et al. (1996). A massive phytoplankton bloom induced by an ecosystem-scale iron fertilization experiment in the equatorial Pacific Ocean. Nature 383, 495-501. 

Coale, K. H., K. S. Johnson, S. E. Fitzwater, R. M. Gordon, S. Tanner, F. P. Chavez, L. Ferioli, C. Sakamoto, P. Rogers, F. Millero, P. Steinberg, P. Nightingale, D. Cooper, W. P. Cochlan, M. R. Landry, J. Constantinou, G. Rollwagen, A. Trasvina, and R. Kudela. 1996. A massive phytoplankton bloom induced by an ecosystem-scale iron fertilization experiment in the equatorial Pacific Ocean. Nature 383 495-501... 

Arrieta JM, Weinbauer MG, Lute C, Herndl GJ (2004) Response of bacterioplankton to iron fertilization in the Southern Ocean. Limnol Oceanogr 49(3) 799-808... 

Suzuki K, Hinuma A, Saito H, Kiyosawa H, Liu H, Saino T et al (2005) Response of phytoplankton and heterotrophic bacteria in the northwest subarctic Pacific to in situ iron fertilization as estimated by HPLC pigment analysis and flow cytometry. Prog Oceanogr. DOI 10.1016/j.po-cean.2005.02.007... 

Verity PG, Villareal TA, Smayda TJ (1988) Ecological investigations of blooms of colonial Phaeocystis pouchetti - 1. Abundance, biochemical composition, and metabolic rates. J Plankton Res 10(2) 219-248 Watson SW, Novitsky TJ, Quinby HL, Valois FW (1977) Determination of bacterial number and biomass in the marine environment. Appl Environ Microbiol 33 940-946 Weaver RS, Kirchman DL, Hutchins DA (2003) Utilization of iron/organic ligand complexes by marine bacterioplank-ton. Aquat Microb Ecol 31 227-239 Weinbauer MG, Arrieta JM, Hemdl GJ (2003) Stimulation of viral infection of bacterioplankton during a mesoscale iron fertilization experiment in the Southern ocean. Geo-phys Res abstracts 5 12280... 

Trull TS, Rintoul R, Hadfield M, Abraham ER (2001) Circulation and seasonal evolution of polar waters south of Australia implications for iron fertilization of the Southern Ocean. Deep-Sea Res II 48 2439-2466... 

Fig. 3.3. Uptake and translocation patterns of Fe in the presence or absence of arbuscular mycorrhizas (AM), and with or without iron fertilization of soil, to peanut or sorghum plants, (a) Experimental...

Jin, X., and Gruber, N. (2003). Offsetting the radiative benefit of ocean iron fertilization by enhancing N2O emission. Geophys. Res. Lett. 30(24), 2249, doi 10.1029/2003GL018458. 

Walter, S., Peeken, I., Lochte, K., Webb, A., and Bange, H. W. (2005). Nitrous oxide measurements during EIFEX, the European Iron Fertilization Experiment, in the subpolar South Atlantic Ocean. Geophys. Res. Lett. 32, L 23613, doi 10.1029/2005GL024619. 

Lenes, J., et al. (2001). Iron fertilization and the Trichodesmium response on the West Florida shelf. Limnol. Oceanogr. 46, 1261-1277. 

Hoffmann, L. J., Peeken, I., Lochte, K., Assmy, P., Veldhuis, M. (2006). Different reactions of Southern Ocean phytoplankton size classes to iron fertilization. Eimnol. Oceanogr. 51, 1217—1229. 

Watson, A. J., Liss, P., Duce, R. (1991). Design of a small-scale in situ iron fertilization experiment. Limnol. Oceanogr. 36, 1960-1965. 

Gervais, F., RiebeseU, U., and Gorbunov, M. (2002). Changes in primary productivity and chlorophyll a in response to iron fertilization in the Southern Polar Frontal Zone. Limnol. Oceanogr. 47, 1324—1335. 

Landry, M., Constantinou, J., Latasa, M., Brown, S., Bidigare, R., and Me, O. (2000). Biological response to iron fertilization in the eastern equatorial Pacific (IronEx II). III. Dynamics of phytoplankton growth and microzooplankton grazing. Mar. Ecol. Prog. Ser. 201, SI—12. 

Figure 38.6 Effects of Fe enrichment on N03 drawdown in the South Patch (66.45° S, 171.8° W) during the SOFeX Southern Ocean mesoscale iron addition experiment. Shown are N03 concentrations versus time in the iron-fertilized patch (closed circles) compared to nearby unfertilized control waters (open circles). Coale et al. (2004), Science 304 408—414.

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