Artificially inducing phytoplankton blooms could lower carbon dioxide levels and fight climate change

The main conversation about climate change focuses mainly on one thing: how much carbon is in the air – and by extension, how to reduce it. However, what is less talked about, but perhaps becoming incredibly important, is how much carbon is in our oceans. There is 50 times more carbon in the ocean than in the atmosphere. Some climate researchers believe that if we could increase the amount of carbon the ocean can absorb from the atmosphere just a little bit, we could avoid some of the worst effects of climate change.

That may seem unusual when you first hear it, but think about it a little longer. The ocean covers about 70 percent of the Earth’s surface and naturally absorbs carbon dioxide, effectively dissolving it. Phytoplankton in the ocean use this carbon dioxide and sunlight to carry out photosynthesis, just like plants on land. This process produces oxygen – phytoplankton is actually responsible for about 50 percent of the oxygen in our atmosphere.

Some climate researchers have proposed that if we could increase the amount of phytoplankton in the ocean, we could get more carbon from the atmosphere. A well-known way to produce a phytoplankton bloom is to introduce iron, an important nutrient for the plankton community, into the water. Many parts of the ocean are low in iron, so even a relatively small addition of iron could theoretically produce a lot of phytoplankton and thereby remove a lot of carbon dioxide from the atmosphere.

“Give me half a tank of iron, and I’ll give you an ice age,” wrote John Martin, an oceanographer at Moss Landing Marine Laboratories, in 1988. At the time, most people were just beginning to become familiar with the idea of ​​climate change as we know it today. . But that’s also around the time when people started thinking about how iron fertilization could affect phytoplankton growth and, in turn, alter carbon levels in the atmosphere.

While climate scientists have spent considerable time discussing this strategy among themselves, there has been no concerted effort to explore it further and take it seriously. Ken Buesseler, a marine radiochemist at the Woods Hole Oceanographic Institution, is a scientist who has done some research on iron fertilization in the ocean. He and his team looked at whether the introduction of iron “could alter the flow of carbon into the deep ocean” and found that there was a significant carbon sequestering effect.

Buesseler told The Daily Beast that his research was done nearly 20 years ago and not much has happened since.

“What happened 20 years ago is that we started walking around and spreading a chemical form of iron and looking for that phytoplankton – the plant’s response – and indeed it showed very clearly that if you improve the iron You can create more uptake of carbon dioxide,” Buesseler said. “The difference between now and 20 years ago is that I think the climate crisis is so much clearer to the public.”

A phytoplankton bloom off the coast of Iceland, observed from space.


Using the oceans to combat climate change has become a hot topic among climate scientists in recent years, and Buesseler was part of a group of scientists that released a report through the National Academies of Sciences, Engineering, and Medicine late last year on the available options, including increasing phytoplankton levels.

‘We have a large reservoir. It already absorbs a third of the greenhouse gases. The question people now ask themselves more often is: what can we do to improve that?” according to Büsseler. ‘Let’s go outside. Let’s do experiments.”

The experiments themselves wouldn’t harm the ocean’s natural ecosystem, Buesseler said, but they could tell us a lot about how introducing more iron into the ocean on a much larger scale could affect that ecosystem in the long run. He doesn’t believe this would cause major damage on a large scale, but it’s important to get the investigation done so we can be sure. He said a “very conservative” estimate would be that up to a gigatonne of carbon dioxide could be captured annually if this process were done on a large scale.

The difference between now and 20 years ago is that I think the climate crisis is much clearer to the public.

Ken Buesseler, Oceanographic Institution Woods Hole

“It will change the types of plants and animals that grow, but that’s already happening with the changes in temperature and acidity,” Buesseler said.

David Siegel, a professor of marine science at the University of California, Santa Barbara, told The Daily Beast that iron fertilization would also be quite simple. You could just take a 120-foot fishing boat and deploy the iron where it is most effective to encourage phytoplankton growth.

“It can be done relatively cheaply. Every atom of iron you add in the right places can fix tens of thousands of carbon atoms,” meaning it gets absorbed by the water. “It’s quite efficient,” Siegel said. “You can deploy ships that release iron oxide into the water — even just iron ore into the water — and you can make flowers that you can see from space. We know that.”

The effects would come on pretty quickly. Scientists who have introduced iron into seawater in the past have seen that phytoplankton blooms can become apparent within the first 24 hours. The ideal place to introduce the iron would be where it is least abundant, namely parts of the ocean – mainly in the southern hemisphere – that are not close to land. Iron that ends up in the ocean usually comes from dust blown into the ocean from land.

Both Buesseler and Siegel stressed that this should not be seen as an alternative to ending the use of fossil fuels. That’s still critical when it comes to having a shot at beating climate change. But to avoid the worst effects of climate change, carbon removal strategies must also be developed to reduce the amount of greenhouse gases in the air.

“Even if we decarbonise our economies, we still need to remove about 20 gigatons of carbon dioxide from the atmosphere to keep us close to the Paris Agreement targets,” Siegel said.

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