Scientists improve oceans to absorb more carbon dioxide

Scientists improve oceans to absorb more carbon dioxide

Alec Rune

Scientists plan to seed part of the Pacific Ocean with iron to create a surge in surface phytoplankton that would absorb carbon dioxide from the air, reviving field tests of a geoengineering technique that has been taboo for more than a decade.

On September 9, 23 academics from Exploring Ocean Iron Solutions (ExOIS), a private non-profit consortium, Climate Frontiers To evaluate the iron fertilizer, the researchers used CO₂ The consortium is studying what materials it can sequester in the deep ocean and how that might affect marine ecosystems, and consortium member Ken Buesseler of the Woods Hole Oceanographic Institution said he hopes to begin testing the technology as early as 2026 across a 10,000-square-kilometer (40,000-square-mile) area of ​​the northeast Pacific Ocean.

The Intergovernmental Panel on Climate Change says the world needs to remove billions of tonnes of CO2 from the atmosphere.₂ With the goal of limiting global warming to 1.5 degrees Celsius (2.7 degrees Fahrenheit), Buesseler says fertilization could be “one piece of that puzzle.” The ocean already contains far more carbon than Earth’s plants, crops and soils, and has the capacity to hold even more, he says. Applying iron could boost the growth of phytoplankton, “accelerating” the natural biological carbon pump, he adds.

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During photosynthesis, phytoplankton consume CO₂These regions are rich in nutrients like oxygen, sunlight, and iron, but in many parts of the ocean, these elements are scarce. When transported to these regions by wind-blown dust or volcanic ash, or by ships purposefully pumping iron sulfate solutions, vast numbers of microorganisms can grow and multiply rapidly. When these organisms die, or are eaten and excreted by larger organisms, some of the carbon they absorbed sinks into the slow currents of the deep ocean as “marine snow,” not releasing carbon into the atmosphere for decades or centuries.

ExOIS is seeking to raise $160 million for the entire program. To start, scientists have received a $2 million grant from the National Oceanic and Atmospheric Administration for computer modeling, and are in negotiations with potential donors such as Ocean Resilience and the Climate Alliance, a coalition of philanthropies funded by billionaire Michael Bloomberg and others.

ExOIS plans to apply for permission to conduct the trials from the U.S. Environmental Protection Agency under the London Protocol, which imposed an international ban on commercial marine iron fertilization in 2013. The treaty allows fertilizer application for research purposes as long as it is monitored and does not cause environmental harm.

Buesseler and his colleagues added iron to the ocean in 12 experiments in the 1990s and 2000s, but an infamous incident in 2012, when American entrepreneur Russ George dumped 100 tonnes of iron filings off the coast of Canada in part to boost salmon fisheries, sparked a public backlash against tinkering with the Earth’s natural systems.

ExOIS promises to closely monitor the effects of field studies and improve computer models of those effects. Scientists will add a non-reactive tracer, such as sulfur hexafluoride, to the iron sulfate solution, which will help them track the spread of fertilizer-sprayed water as the iron sulfate slowly breaks down. They say CO₂ They’ll use ships, floats and underwater drones to measure iron concentrations, and look at satellite imagery that can document an increase in the color of phytoplankton at the ocean’s surface. The group also promises more public engagement and consideration of environmental impacts than previous iron-spraying projects.

The effects could be diverse and far-reaching. In 2009, German and Indian scientists conducted experiments in the southwest Atlantic, where larger zooplankton ate smaller phytoplankton, and very little carbon actually reached the deep ocean. In 2006, U.S. and Canadian researchers conducted experiments in the northeast Pacific, where toxic phytoplankton species flourished. This has raised concerns that fertilization could create “dead zones” where algal blooms could consume all the oxygen in the water and kill other organisms. Phytoplankton blooms could also consume nutrients such as phosphorus and nitrogen, causing a phenomenon called “nutrient plundering,” in which nutrients become unavailable to other organisms. Moreover, scientists still know very little about the deep-sea ecosystems where carbon is supposed to be stored. “Probably (iron fertilization) affects something we don’t yet fully understand,” says Lisa Levin, a deep-sea expert at Scripps Institution of Oceanography, who is not involved in the ExOIS program.

Last year, a computer modeling study by researchers from the UK, US and France found that putting 1 to 2 million tonnes of iron into the oceans each year could absorb 45 billion tonnes of carbon by 2100. But it would also deprive other marine life of nutrients. Warming could lead to an estimated 15% loss in marine biomass, and another 5% could be lost due to iron fertilization, especially in fisheries along the Atlantic, Pacific and Indian Ocean coasts. “I haven’t really seen[ExOIS]put forward hypotheses about where previous research went wrong and how to increase carbon yields or minimize the negative effects,” says Alessandro Tagliabue of the University of Liverpool in the UK, co-first author of the study.

Buesseler argues that such difficult trade-offs may be necessary: ​​”This is a smaller change in biological terms than doing nothing and watching the Earth boil,” he says.