Deep Sea Volcanoes May Have Fertilized Ancient Oceans, Aiding Carbon Storage
New research reveals a surprising link between sea levels, volcanic activity at the bottom of the ocean, and the health of marine life at the surface.
A study published in Nature Geoscience by Boston College researchers presents evidence that during Earth's ice-age transitions, falling sea levels may have triggered increased volcanic activity along mid-ocean ridges. This, in turn, released significant amounts of iron from hydrothermal vents.
A Natural Iron Pump
In the eastern equatorial Pacific, where surface waters are notoriously iron-deficient, this deep-sea iron may have acted as a crucial fertilizer. By boosting the growth of phytoplankton, this process could have enhanced the ocean's ability to absorb and store carbon.
The research team analyzed nitrogen isotopes in the shells of foraminifera—tiny fossilized plankton—from sediment cores that span 200,000 years. Their analysis revealed that periods of peak nutrient consumption during deglaciations coincided precisely with times of higher hydrothermal iron release.
How the Connection Works
- The Catalyst: Lower sea levels during ice ages reduce pressure on underwater volcanoes, increasing their activity.
- The Fertilizer: This volcanism releases more iron into the deep ocean from hydrothermal vents.
- The Delivery: Ocean modeling suggests that under these stronger hydrothermal conditions, the iron can be mixed upward to the sunlit surface, where plankton can use it.
Key Statements from the Researchers
"The surprising message is that life at the sunlit ocean surface may be connected to volcanic activity thousands of meters below."
— Lead author Xingchen "Tony" Wang
The team described the phenomenon as a "natural experiment" created by Earth's own climate cycles.
Co-first author Tianshu Kong noted the clarity of the data: "When the 200,000-year record came together, the two deglacial peaks were striking."
Supporting this, co-first author Xiaozhou Ruan explained the modeling results: "Our modeling suggests that under stronger hydrothermal activity, iron released in the deep ocean could be transported to depths where upwelling and mixing make a connection to surface waters plausible."
Broader Implications
This study outlines a potential natural feedback loop connecting:
- Sea level → Seafloor volcanism → Ocean biology → Carbon storage → Atmospheric CO2 → Climate
It is important to note that this research does not test deliberate ocean iron fertilization as a carbon dioxide removal strategy. Instead, it examines a natural, geological process from Earth's past.
The researchers plan to investigate whether this natural fertilization occurred in other regions, particularly in the Southern Ocean, to see if this was a global phenomenon.
Sources:
- Boston College press release (June 9, 2026)
- Nature Geoscience: "Ocean iron fertilization from enhanced mid-ocean-ridge volcanism due to ice-age sea-level falls"