De-acidifying and Revitalizing the Ocean While Reducing CO2—With Iron Enrichment

by Vins
Published: Last Updated on

For over 20 years researchers have noted how wind driven, iron-laden dust (sand) has fertilized the ocean, feeding plankton which also soak up carbon dioxide from the air. A recent study shows the effects of iron enrichment over 40,000 years, providing a historical validation of the iron hypothesis, with evidence appearing in the sediment record.

However, new studies in the Southern Ocean revealed that the CO2 sequestering efficiency of the phytoplankton is reduced by the iron-stimulated growth of shelled organisms that graze on the plankton, reducing their efficacy by up to thirty percent. With this and other studies it’s becoming clear that iron helps in CO2 reduction, yet even massive amounts will not, by itself, solve the carbon dioxide problem.

Iron fertilization has applications beyond climate change, as borne out by other experiments. Seeding small ocean areas clearly supports phytoplankton growth spurts, and local aquatic life. Another recent study offers a paradigm shift in geological thinking involving iron fertilization in the formation of the Bahamas and other coral platforms. This theory, if correct, also offers a partial solution to ocean acidification and revitalization.

Researchers believe that iron-rich dust fertilized cyanobacteria which provided a source of nitrogen to the rest of the ecological community in this nutrient-poor environment while also sequestering CO2 from the water, raising ocean pH, and initiating the precipitation of carbonate in the waters. This phenomenon might be responsible for the formation of vast amounts of sediments in the oceans, throughout geological history.

Human activities and CO2 emissions have caused reductions in atmospheric dust and a dramatic decline in this natural fertilization process. Iron fertilization proponents suggest the possibility of helping revitalize coral reefs, “dead zones,” fish colonies, etc. with the careful addition of iron sulfate, which is easily accessible and inexpensive.

Despite these possibilities, there is steady resistance from those who fear unintended ecological impacts especially with larger-scale experiments. The standard mantra is always: More research is needed. This is understandable, yet given the urgency of the declining health of our oceans and climate, it’s astonishing that we aren’t exploring this further.


Alfredo Martinez-Garcia, Daniel Sigman, Haoil Ren, Robert Anderson, Mariette Straub, David Hodell, Samuel Jaccard, Timothy Eglinton, Gerald Haug, “Iron Fertilization of the Sub-Antarctic Ocean During the Last Ice Age,” Science, March 21, 2014,

Bob Yirka, “Drill core evidence adds credence to iron fertilization hypothesis regarding last ice age,“ Phys-Org, Mar 21, 2014,

Ian Salter and international collaborators, “Iron fertilization less efficient for deep-sea carbon dioxide storage than previously thought?” Phys-Org, Nov. 10, 2014,

P.K. Swart, A.M. Oehlert, G.J. Mackenzie, G.P. Eberli and J.J.G. Reijmer, The Fertilization of the Bahamas by Saharan Dust: A Trigger for Carbonate Precipitation?, Journal of Geology, June 30, 2014,

“Saharan Dust is Key to Formation of Bahamas’ Great Bank, Study Finds,” Science Daily, July 24, 2014,

Tim Worstoll, “Iron Fertilisation of the Oceans Produces Fish and Sequesters Carbon Dioxide. So Why Do Environmentalists Oppose It?,” Forbes, April 28, 2014,

Student Researcher: Kayla Smyth (San Francisco State University)

Faculty Evaluator: Kenn Burrows (San Francisco State University)