Award: OCE-2205984

Project Outcomes Report for the General Public

 

This project investigated how calcium carbonate (the same material found in seashells and limestone) dissolves beneath the seafloor and how this process affects ocean chemistry and the global carbon cycle. Calcium carbonate plays a key role in regulating how much carbon dioxide (CO₂) the ocean can absorb from the atmosphere, which has important implications for climate change.

 

A major outcome of this work was the development of a global framework for understanding how calcium carbonate behaves below the seafloor. By compiling and analyzing chemical data from more than a thousand scientific ocean drilling sites around the world, we showed that seawater trapped within sediments is often chemically capable of dissolving calcium carbonate, even when the overlying ocean water is not. This dissolution is primarily driven by the breakdown of organic matter by microbes, which alters seawater chemistry. At greater depths below the seafloor, different microbial processes reverse this trend and promote mineral stability. These results demonstrate that carbonate dissolution beneath the seafloor is more widespread than previously recognized and could play an important role in ocean chemistry.

 

The project also provided new insights into how different types of carbonate minerals form and transform during burial. Using advanced laboratory techniques, we identified multiple forms of calcium carbonate in marine sediments and linked them to specific biological and chemical processes. This improves our ability to interpret sediment records and understand how ocean conditions have changed over time.

 

 

The project also contributed to understanding the role of marine organisms, including fish, in the ocean carbon cycle. By analyzing ocean samples and conducting laboratory experiments, we identified new sources of carbonate particles in the open ocean and developed methods to better track their origin and fate.

 

In addition, this work explored emerging approaches to remove CO₂ from the atmosphere by adding alkalinity to the ocean. Laboratory and shipboard experiments showed that adding alkalinity can trigger the formation of new minerals, which can reduce the efficiency of this carbon removal strategy. These findings provide important constraints for evaluating the feasibility and environmental impacts of ocean-based carbon dioxide removal.

 

Beyond scientific discoveries, this project supported the training of undergraduate students, who gained hands-on experience in laboratory experiments, fieldwork, and data analysis. The project also contributed to public outreach and science communication efforts, helping to explain how ocean chemistry and the carbon cycle are connected to climate change.

 

Overall, this research advances our understanding of how the ocean regulates carbon and provides new tools and knowledge to better predict how marine systems will respond to future environmental change.

 

Last Modified: 04/14/2026
Modified by: Mohammed   Hashim