Ocean Micro Nutrient Replenishment

Also known as the “Iron Hypothesis”1 , this process is more accurately called Ocean Micro Nutrient Replenishment and was first proposed by oceanographer John Martin2 in 1993. It is based on the concept that iron is a critical nutrient for primary ocean productivity, and oceanic iron deposition has been in decline for decades3.  Hence, natural or man-made iron replenishment in the ocean may restore primary ocean productivity which in turn may reduce oceanic fish mortality and lead to improvements in fisheries.

Our Oceans contain phytoplankton4, a single cellular microscopic plant that uses photosynthesis to convert light, carbon dioxide and nutrients into oxygen and food source.  The primary consumers of phytoplankton are zooplankton5, which are small creatures that are visible to the naked eye.  Zooplankton in turn are the main food source for most of the ocean biomass.  Fish and marine cetaceans consume vast amounts of zooplankton as their primary food source. In fact the world’s largest animal, the great blue whale, is a zooplankton consumer6.

Iron is normally present in our oceans, however over the last century we have seen a significant decline in phytoplankton biomass, an average of 1% of the global median per year.7 Ocean waters near shore do not show depleted iron levels due to the interaction of the ocean with land, and water runoff that contains iron.  However, the far ocean (also known as the Pelagic Zone) is generally deficient in iron. These areas are known as “High Nutrient, Low Chlorophyll” (HNLC) zones.8

Surprisingly, the source of pelagic iron is primarily dust from deserts and volcanos.9 For millions of years, great global winds known as Aeolian winds have transported sand and dust from land, across thousands of miles of Ocean.  This dust contains iron.

However, studies of sediment cores have shown that natural dust deposition has been in decline.10  For example, the North Pacific has seen a decline in dust from northern Asia, notably the Gobi and Taklimakan deserts.11  Climate change may be responsible.  Because of the precipitous rise of global carbon dioxide levels, photosynthesizing grasses have an improved food source.  This has resulted in dramatic spread of global grasslands, which trap dust and limit aeolian transport of iron into the pelagic ocean12.

We also know that phytoplankton, the base of the oceanic food chain, significantly effects atmospheric oxygen and carbon dioxide levels, despite their decline.13

One might expect that phytoplankton, which also photosynthesize, would manifest a positive response to the abundance of carbon dioxide in the atmosphere and multiply in the ocean.  However it has been shown that oceanic iron deficiency limits phytoplankton growth despite the availability of large concentrations of atmospheric carbon dioxide.14

This indicates that replacing missing iron back into the ocean could stimulate phytoplankton based photosynthesis and generate improvements to the ocean ecosystem, while removing carbon dioxide from the atmosphere as it is consumed by photosynthesis.

There have been two naturally stimulated iron replenishment events in the Pacific Northwest due to volcanic dust from a nearby eruption.  The most recent such event occurred in 2008 with the eruption of Mt Kasatochi15 in the Gulf of Alaska.  This eruption deposited millions of tons of volcanic ash, containing iron, across the Pacific Ocean.

This image shows the extent of the volcanic ash from the Kasotochi eruption in 2008  Red means high concentrations and blue being the lowest.  When this in compared to satellite observations of chlorophyll in the ocean (an indicator of phytoplankton growth) a major difference is seen between the 2007 and 2008, when volcanic iron stimulated plankton growth.

Comparing the satellite plankton observations against the believed salmon migration routes indicates that migrating salmon were likely within the zone that contained vastly increased levels of plankton biomass, including zooplankton, which is a food source for salmon.  If the fish fed upon this biomass source, they would have grown to be larger and much less likely to die from malnutrition.  Since sockeye salmon spend two years in the ocean before returning, this is believed to be the cause of the record sockeye salmon returns reported in 2010.16

Given this evidence that raising concentrations of iron may be a practical and cost effective methodology for improving the ocean ecosystem and sequestration of atmospheric carbon dioxide, several small to medium scale scientific experiments were conducted by academic and research organizations.  The most recent such experiment was conducted by the Alfred Wegener Institute in 2009 the results of which have not yet been published.  However, the Alfred Wegener Institute has recently published the results of their 2004 experiment17.  Among other findings, the research did show that no harmful environmental effects were noted in creating an artificially generated iron induced plankton bloom, and that very large quantities of carbon dioxide are indeed sequestered from the atmosphere.

It is not surprising that no harmful effects were noted, since if adding iron to the ocean were in fact a negative stress on the ecosystem, a massive negative effect would have been seen following the Kasotochi eruption which deposited millions of tons of iron into the ocean.  In fact, only positive environmental effects were ever observed.  Any rational discussion that proposes addition of iron to the ocean is environmentally negative or hazardous must address the positive environmental effect of the Kasotochi eruption and to take into account the massive quantities of iron that were deposited into the ocean, with no observed ill effects.

In light of these facts, our organization performed an iron micro-nutrient enrichment mission during the summer of 2012 to answer the following question "Does adding a trace amount of iron to a High Nutrient Low Chlorophyll (HNLC), cold core ocean eddy located in a known salmon migration route cause phytoplankton to grow, and if so, what are the resulting environmental benefits or costs"?  We deposited 100 tons of iron sulphate, and 20 tons of iron oxide over approximately 5,000 km2 into a HNLC, cold core eddy centred approximately 300 nautical miles west of Haida Gwaii.  This did indeed generate a plankton bloom, clearly visible from satellite observations.

The location and timing of this plankton bloom was meant to coincide with migrating salmon, so that a large source of food would be generated within their known migration route.

Before, during and after stimulating this plankton bloom, our research ship and two Autonomous Underwater Vehicles known as Slocum gliders collected detailed mesoscale data of the ocean ecosystem so that scientific conclusions could be made on the merits of this endeavour.

Our instruments collected a wide range of observations which are detailed on the “Scientific Data” section of our website.  This data is available for analysis by researchers and interested parties without charge.

In the autumn of 2013 the Globe and Mail published an article called “Pink salmon reaching Fraser River in massive numbers”18.  Not only was the 2013 salmon return in the Fraser River far larger than expected, Howe sound also experienced a salmon return that was 10 to 100 times what was expected.  

At this time no significant environmental change has been noted within the Gulf of Alaska ecosystem that could be responsible for this, other than the plankton bloom we generated.  It is possible that a yet unknown factor could have caused this response in the 2013 fisheries returns and we remain engaged in the scientific study of this event.  We must clearly state that at this time, no causal relationship exists between the 2013 fisheries returns and our project.  Further research will be required to prove the cause of the increase in the 2013 fisheries.

Our organization is committed to further study and research of this event, and to engage with the scientific community and stakeholders to establish factual consensus on the merits and limitations of ocean micro-nutrient replenishment as a practical means of fisheries management.  Any organization or individual who is interested in contributing to analysis of our data, engaging with us or support of our organization should contact us.


1. http://en.wikipedia.org/wiki/Iron_Hypothesis

2  http://en.wikipedia.org/wiki/John_Martin_(oceanographer)

3. Maher, B.A. et al. (2010) Global connections between Aeolian dust, climate and ocean biogeochemistry at the present day and at the last glacial maximum. Earth Science Reviews, 99, 61-97. doi:10.1016/j.earscirev.2009.12.001

4. http://en.wikipedia.org/wiki/Phytoplankton

5. http://en.wikipedia.org/wiki/Zooplankton

6. http://en.wikipedia.org/wiki/Blue_whale

7. Boyce, D.G., Lewis, M.R., Worm, B. (2010) Global phytoplankton decline over the past century. Nature, 466, 591-596. doi:10.1038/nature09268

8. Weier, John. "John Martin (1935-1993)". On the Shoulders of Giants. NASA Earth Observatory. Retrieved 2012-08-27

9. Mahow1ald, N.M. et al. (2005) Atmospheric global dust cycle and iron inputs to the ocean. Global Biogeochemical Cycles, 19, GB4025. doi:10.1029/2004GB002402

Olgun, N. et al. (2011) Surface ocean iron fertilization: The role of airborne volcanic ash from subduction zone and hot spot volcanoes and related iron flues into the Pacific Ocean. Global  Biogeochemical Cycles, 25, GB4001. Doi:10.1029/2009GB003761

10. Maher, B.A. et al. (2010) Global connections between Aeolian dust, climate and ocean biogeochemistry at the present day and at the last glacial maximum. Earth Science Reviews, 99, 61-97. doi:10.1016/j.earscirev.2009.12.001

11. Sun, J., Zhang, Mingying., Liu, T. (2001) Spatial and temporal characteristics of dust storms in China and its surrounding regions, 1960-1999: Relations to source area and climate. Journal of Geophysical Research, 106(D10), 325-333.

Xiao, F., Shou, C., Liao, Y. (2008) Dust storms evolution in Talkimakan Desert and its correlation with climatic parameters. Journal of Geographical Sciences, 18, 415-424. doi:10.1007/s11442-008-0415-8

12. Mahowald, N.M. and Luo, Chao. (2003) A less dusty future? Geophysical Research Letters, 30(17) 1903-1906. doi: 10.1029/2003GL017880

13. Falkowski, P. (2012) Ocean Science: The power of plankton. Nature, 483, S17-S20. doi:10.1038/483S17a

Field, C.B. et al. (1998) Primary Production of the Bioshpere: Integrating Terrestrial and Oceanic Components. Science, 281, 237-240. doi:10.1126/science.281.5374.237

Sheldon, R.W., Sutcliffe, W.H.Jr., Paranjape, M.A. (1977) Structure of pelagic food chain and relationship between plankton and fish production. Journal of the Fisheries Research Board of Canada, 34:2344-2353

14. Martin, J.,Fitzwater,S (1988) Iron deficiency limits phytoplankton growth in the north-east Pacific subarctic.Nature 331, 341 - 343 (28 January 1988); doi:10.1038/331341a0

15. http://en.wikipedia.org/wiki/Kasatochi_Island

16.Parsons T, Whitney F, (2012) Fisheries and Oceanography 21:5, 374-377,2012  Did volcanic ash from Mt. Kasatoshi in 2008 contribute to a phenomenal increase in Fraser River sockeye salmon (Oncorhynchus nerka) in 2010?

Lindenthal, Langmann, Patsch, Lorkowski Hort (2013) “The ocean response to volcanic iron fertilisation after the eruption of Kasatochi volcano: a regional-scale biogeochemical ocean modelstudy. Biogeosciences, 10, 3715–3729

17. Smetacek V et al, (2012) Deep Carbon export from a Southern Ocean iron-fertilized diatom bloom, Nature 487, 313-319 (19 July 2012)doi:10.1038/nature11229

18. http://www.theglobeandmail.com/news/british-columbia/pink-salmon-reaching-fraser-river-in-massive-numbers/article14298697/

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