Ocean iron fertilization: A promising path for carbon removal?

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Greg Rau

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Dec 10, 2025, 2:14:28 AM (7 days ago) Dec 10
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In a recent Ocean Series webinar, Dr. Ken Buesseler, Senior Scientist at the Woods Hole Oceanographic Institution, discussed a promising yet debated solution: Ocean Iron Fertilization. As a marine radiochemist and the director of the non-profit Exploring Ocean Iron Solutions (ExOIS), Dr. Buesseler shared insights on how adding small amounts of iron to the ocean could amplify its natural ability to store carbon, the potential impacts on marine ecosystems, and the path toward responsible research.”

Bhaskar M V

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Dec 10, 2025, 10:16:18 AM (7 days ago) Dec 10
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The emphasis of Ocean Fertilization should change from the input, Iron, to the targeted / desired output, Diatoms.
Growing Diatom Algae in Oceans is the best pathway for Carbon Sequestration.

Regards

Bhaskar 

Ken Buesseler

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Dec 11, 2025, 3:47:40 PM (6 days ago) Dec 11
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Since diatoms have already been shown to respond naturally and quickly to iron inputs in many parts of the ocean, and since they are the "winners" of the Biological Carbon Pump in terms of efficiency for C export out of the surface ocean and rapid transfer to depth, yes, enhancing diatoms remains key to enhancing C sequestration.  And, they also need very little iron to promote their growth. Other micro and macronutrients will matter, but let's stop talking about "nutrient fertilization" and focus on testing "iron fertilization" as you could never scale up mCDR with macronutrient additions.  

Bhaskar M V

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Dec 11, 2025, 9:17:21 PM (5 days ago) Dec 11
to Ken Buesseler, Carbon Dioxide Removal
Ken

You are missing the basic point.
Algal Blooms in Lakes, Coastal Waters, etc., are causing problems of Eutrophication, Hypoxia, Mass Fish Kills, decline in Fish, etc.
These are generally blooms of Cyanobacteria / Blue Green Algae and Dinoflagellates / Red Tides and in a few locations of Toxic Diatoms.
The apprehension about 'Iron' Fertilization is that this may result in bloom of the very same algae that are causing these problems.
So we need a solution that clearly results in growth of ONLY healthy non-toxic Diatoms and not of other types of algae.
Dosing Iron in the form of Iron Sulfate and Hematite Ore does not ensure that ONLY non-toxic Diatoms grow.

That is why our solution to dose 10 Micro-nutrients on a Nano Silica base is necessary.
We have demonstrated that this ensures that this solution grows ONLY Non-Toxic Diatoms and 
thereby solves the problems of Algal Blooms, i.e., blooms of Cyanobacteria and Dinoflagellates.

I don't understand your reference to "nutrient fertilization", my comment did not mention this.
I too am advocating MICRO-nutrient Fertilization, all the Micro-nutrients that Diatoms require.
We have identified that Diatoms require 10 Micro-nutrients, we can change the formula if required.

In lakes and coastal waters, we can use the Macro-nutrients, N and P, 
from Fertilizer runoff and Sewage to grow Diatoms and thus grow Fish.
We can demonstrate that we can solve the problems of Eutrophication, Hypoxia, etc.

Regards

Bhaskar
Director
Kadambari Consultants Pvt Ltd
Hyderabad. India
Ph. & WhatsApp : +91 92465 08213


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Kevin Wolf

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Dec 15, 2025, 12:24:07 AM (2 days ago) Dec 15
to Ken Buesseler, Carbon Dioxide Removal
Ken,

There is a lot of evidence that a lack of silica is also prematurely stopping diatom production. It is not just a lack of iron (see these papers about the coast of CA).

When micro-nutrients are added to the ocean primarily to boost fishery production and reduce harmful algal blooms (HABs)—whether directly or via dust deposition—these activities fall under “Ocean Ecosystem Enhancement or Management.” In contrast, adding iron mainly to sequester carbon is classified as “geoengineering.” Both approaches stimulate the biological pump and can increase long‑term (100+ year) carbon sequestration compared with doing nothing, but geoengineering is far more politically contentious than ecosystem enhancement.

Carbon-credit–driven projects naturally emphasize maximizing carbon drawdown, treating fish production and HAB reduction as secondary co‑benefits. However, an iron‑only fertilization strategy downplays the importance of tailoring a specific mix and dose of micro‑nutrients to achieve concrete ecological outcomes in a given area, such as increasing zooplankton food supply or suppressing HAB‑forming species. Many stakeholders are more motivated by restoring fish and whale populations and reducing HABs on tourist beaches than by supporting ocean geoengineering framed purely around Ocean Iron Fertilization (OIF).

Framing this work as “Ocean Abundance Restoration” better reflects the ecological complexity of the ocean than simpler “add iron” proposals. We think adding micronutrients to the ocean has a much better chance of being widely and quickly added it is  primary goals are rebuilding fisheries and reducing HABs, with carbon credits recognized as a significant, but derivative, benefit arising from the additional carbon drawn down and sequestered by an invigorated biological pump.

Sincerely,

Kevin Wolf, Co-chair
Ocean Abundance Restoration Alliance

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Benjamin Twining

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Dec 16, 2025, 4:34:58 PM (15 hours ago) Dec 16
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Bhaskar,

Please direct me to the evidence supporting your statement that adding multiple nutrients and nano silica only supports the growth of non-toxic diatoms? I am interested in these findings.

thank you,
Ben
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