Anoxic marine basins are among the best candidates for deep-sea carbon sequestration

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Last Updated22/02/2024

According to scientists, anoxic marine basins may be among the most viable places to conduct large-scale carbon sequestration in the deep ocean.

To achieve climate goals, including limiting global warming to 1.5°C above pre industrial levels, net negative CO2 removal strategies are essential.
Sending plant biomass to the seafloor offers a promising method for carbon storage, preventing CO2 and methane release into the atmosphere during decomposition.
Anoxic marine basins are identified as suitable sites for carbon storage.

The researchers examined three basins viz. the Black Sea, the Cariaco Basin, and the Orca Basin; assessing their capacity for biomass storage and preservation.
Among the three basins, the Black Sea emerges as the most viable option due to its depth, isolation, and ongoing anoxia.

They are characterised by oxygen deficiency and isolation from main currents.
In most anoxic basins, the water is extremely stagnant and can have mixing times of many thousand years.
They can’t support animal life and are populated primarily by microbes and some very specialised fungi with different metabolisms than creatures in oxygen-rich environments.
Many anoxic basins also contain toxic chemicals, which are produced by geothermal activity or by microbes living in the basins.
Some also contain salt domes, big mounds of hardened salt.
In some anoxic basins, methane and other gases collect in reservoirs beneath the seafloor.
- The gases can percolate upward, pushing up domes of sediment on the seafloor that are called mud volcanoes.
- The gases can burst through the soft sediments, creating "mini-eruptions" of wispy columns of sediment-filled water.

Permanent anoxic basins form when there is a strong layering of the water column created in a cup-like formation on the ocean floor.
The layering is caused by density differences due to salt concentration or temperature.
Once stratification occurs, circulation with the rest of the ocean is minimised, and microorganisms consume the oxygen in the water.