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Iron Availability for Oceanic Organisms in Many Locations Can Vary Dramatically Over Time — Even Up to a Factor of Five

Iron availability in the ocean fluctuates dramatically across various timescales and locations. Factors such as atmospheric conditions, ocean currents, and biological activity drive these changes. Researchers have extensively studied iron variability in different oceanic regions, providing critical insights into how iron levels change daily, seasonally, and interannually. This article will explore the mechanisms behind these fluctuations and their implications for marine ecosystems.

Studies and Estimates​

Iron in the Southern Ocean​

In the Southern Ocean, iron concentrations can vary markedly due to dust deposition, biological uptake, and ocean currents. A study by Tagliabue et al. (2014) documented how iron levels could fluctuate by factors of 2 to 5 over seasonal cycles. The deep winter mixing plays a crucial role in sustaining surface-water iron supplies, highlighting how seasonal dynamics govern regional iron availability1.

North Atlantic Ocean​

Research by Bowie et al. (2002) in the North Atlantic Ocean revealed seasonal iron concentration variances ranging from 10% to 50%. These fluctuations are significantly influenced by atmospheric dust inputs and the biological uptake during phytoplankton blooms, making it evident that biological and atmospheric processes contribute heavily to iron availability in this region23.

Pacific Ocean​

The El Niño-Southern Oscillation (ENSO) events play a substantial role in the Pacific Ocean's iron variability. During El Niño events, iron availability can decrease by more than 50% due to reduced upwelling, whereas La Niña events can significantly enhance iron levels. This interannual variability underscores the influence of large-scale climatic phenomena on oceanic iron dynamics45.

Sources:​

Footnotes​

  1. Tagliabue, A., Sallée, J.-B., Bowie, A. R., Lévy, M., Swart, S., & Boyd, P. W. (2014). Surface-water iron supplies in the Southern Ocean sustained by deep winter mixing. Nature Geoscience, 7(4), 314-320. https://doi.org/10.1038/ngeo2101 ↩

  2. Bowie, A. R., Whitworth, D. J., Achterberg, E. P., Mantoura, R. F. C., & Worsfold, P. J. (2002). Biogeochemistry of Fe and other trace elements (Al, Co, Ni) in the upper Atlantic Ocean. Deep Sea Research Part I: Oceanographic Research Papers, 49(4), 605-636. https://doi.org/10.1016/s0967-0637(01)00061-9 ↩

  3. Sarthou, G., Baker, A. R., Blain, S., Achterberg, E., Bakker, D. C. E., Boyé, M., Bowie, A. R., Chuck, A. L., Croot, P., Laan, P., de Baar, H. J. W., & Jickells, T. (2002). Sea-surface dissolved iron distribution and atmospheric iron inputs in the East Atlantic. Journal Name. http://ecite.utas.edu.au/26286 [Note: The journal name is missing, please replace it if available.] ↩

  4. Johnson, K. S., Chávez, F. P., Elrod, V. A., Fitzwater, S. E., Pennington, J. T., Buck, K. R., & Walz, P. M. (2001). The annual cycle of iron and the biological response in central California coastal waters. Geophysical Research Letters, 28(7), 1247-1250. https://doi.org/10.1029/2000gl012433 ↩

  5. Rapp, I., Schlösser, C., Browning, T. J., Wolf, F., Le Moigne, F. A. C., Gledhill, M., & Achterberg, E. P. (2020). El Niño‐driven oxygenation impacts Peruvian shelf iron supply to the South Pacific Ocean. Geophysical Research Letters, 47(7). https://doi.org/10.1029/2019gl086631 ↩