Ocean iron fertilization: Is increasing iron content in the sea a sustainable fix for climate change?

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  Quantumrun Foresight
• October 3, 2022

Insight summary

Exploring the ocean's role in climate change, scientists are testing whether adding iron to seawater can boost organisms that absorb carbon dioxide. This approach, while intriguing, may not be as effective as hoped due to the complex balance of marine ecosystems and self-regulating microorganisms. The implications extend to policy and industry, with calls for careful consideration of environmental impacts and the development of less invasive methods for carbon sequestration.

Ocean iron fertilization context

Scientists are conducting experiments on the ocean by increasing its iron content to encourage the growth of organisms that absorb carbon dioxide. While the studies are initially promising, some researchers argue that ocean iron fertilization will have little effect on reversing climate change.

The world’s oceans are partially responsible for maintaining atmospheric carbon levels, primarily through phytoplankton activity. These organisms take atmospheric carbon dioxide from plants and photosynthesis; those that aren’t eaten, preserve carbon and sink to the ocean floor. Phytoplankton can lie on the ocean floor for hundreds or thousands of years.

However, phytoplankton needs iron, phosphate, and nitrate to grow. Iron is the second most common mineral on Earth, and it enters the ocean from dust on the continents. Similarly, iron sinks to the seafloor, so some parts of the ocean have less of this mineral than others. For example, the Southern Ocean has a lower iron level and phytoplankton population than other oceans, even though it is rich in other macronutrients.

Some scientists believe that encouraging the availability of iron underwater can lead to more marine micro-organisms that can absorb carbon dioxide. Studies in ocean iron fertilization have been around since the 1980s when marine biogeochemist John Martin conducted bottle-based studies demonstrating that adding iron to high-nutrient oceans rapidly increased phytoplankton populations. Of the 13 large-scale iron fertilization experiments conducted due to Martin’s hypothesis, only two resulted in removing carbon lost to deep sea algae growth. The remaining failed to show an impact or had vague results.

Disruptive impact

Research from the Massachusetts Institute of Technology highlights a crucial aspect of the ocean iron fertilization method: the existing balance between marine microorganisms and mineral concentrations in the ocean. These microorganisms, crucial in pulling carbon from the atmosphere, exhibit a self-regulating capacity, altering ocean chemistry to meet their needs. This finding suggests that simply increasing iron in oceans may not significantly boost the capacity of these microbes to sequester more carbon as they already optimize their environment for maximum efficiency.

Governments and environmental bodies need to consider the intricate relationships within oceanic systems before implementing large-scale geoengineering projects like iron fertilization. While the initial hypothesis suggested that adding iron could drastically increase carbon sequestration, the reality is more nuanced. This reality requires a more comprehensive approach to climate change mitigation, considering the ripple effects through marine ecosystems.

For companies looking towards future technologies and methods to combat climate change, the research underscores the importance of thorough ecological understanding. It challenges entities to look beyond straightforward solutions and invest in more ecosystem-based approaches. This perspective can foster innovation in developing climate solutions that are not only effective but also sustainable.

Implications of ocean iron fertilization

Wider implications of ocean iron fertilization may include: 

• Scientists continuing to conduct iron fertilization experiments to test if it can revitalize fisheries or work on other endangered marine micro-organisms. 


• Some companies and research organizations continuing to collaborate on experiments that attempt to carry out ocean iron fertilization schemes to collect carbon credits.


• Raising public awareness and concern of the environmental hazards of ocean iron fertilization experiments (e.g., algae blooms).


• Pressure from marine conservationists to permanently ban all large-scale iron fertilization projects.


• The United Nations creating stricter guidelines on what experiments will be allowed on the ocean and their duration.


• Increased investment by governments and private sectors in marine research, leading to the discovery of alternative, less invasive methods for carbon sequestration in oceans.


• Enhanced regulatory frameworks by international bodies, ensuring that ocean fertilization activities align with global environmental protection standards.


• Development of new market opportunities for environmental monitoring technologies, as businesses seek to comply with stricter regulations on oceanic experiments.

Questions to consider

• What other repercussions might result from conducting iron fertilization in various oceans?


• How else might iron fertilization affect marine life?