Anoxic Marine Basins Could Be the Most Viable Places to Conduct Large-Scale Carbon Sequestration in Deep Ocean, Study Reveals

Experts suggest that global warming beyond two degrees Celsius above the pre-industrial average could seriously harm human life. To prevent the mean global temperature from crossing this critical threshold, authorities aim to reduce atmospheric carbon dioxide emissions.

Biomass Carbon Storage

Climate models suggest that net negative carbon dioxide must be removed in order to reach climate goals. Different ways can be done to store carbon. One of the promising methods is the sinking of carbon to the seafloor in the form of plant biomass. This will cause the vegetation to stop releasing carbon dioxide and methane into the air as it degrades. Ideally, this approach would lock away carbon for hundreds or thousands of years.

This idea of carbon storage is not new, yet uncertainties surround it. One challenge is the introduction of loads of plant materials and their effect on the chemistry and ecology of the surrounding materials. Experts should ensure that decomposition products do not escape into sensitive habitats. Additionally, carbon should not return to the water column to be released at the surface.

Anoxic Biomass Carbon Sequestration

The consequences of carbon storage could further damage the already fragile ocean ecosystems, so scientists thought of the least destructive version of the idea they could envision. For this reason, anoxic marine basins emerge as the most likely candidate.

Anoxic marine basin refers to a body of water without oxygen, generally formed in areas with restricted water exchange. They are intense and are largely isolated from the major oxygen-supplying currents. As a result, they cannot support animal life and are primarily populated by microbes and specialized fungi with metabolisms different from those in oxygen-rich environments.

In the study "Biomass Storage in Anoxic Marine Basins: Initial Estimates of Geochemical Impacts and CO2 Sequestration Capacity," the research team examined three basins with different properties to determine the most promising candidate for biomass storage. Led by

geochemist and geobiologist Morgan Raven, the researchers chose the Cariaco Basin near Venezuela, the Black Sea in Eastern Europe, and the Orca Basin in the Gulf of Mexico.

The Black Sea is so restricted that it is largely isolated from the rest of the ocean. It is also becoming more anoxic as humans dumped fertilizers over the last century. Meanwhile, the Cariaco Basin has the same chemical properties as the Black Sea but is subject to a faster water turnover. Finally, the "wildly weird" Orca Basin is a hypersaline mini-basin on the continental slope. Its salt concentration is so high that it creates a drastic difference in density from the upper waters.

The Black Sea basin emerged as the best option due to its size and isolation. Measuring 7,500 feet (2,300 meters) deep and 124,467 square miles (322,367 square kilometers) wide, this anoxic marine basin can contain biomass at large scales relevant to climate.

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