The oceans are a major carbon sink, absorbing and storing a significant amount of carbon dioxide (CO2) from the atmosphere. According to estimates from the Intergovernmental Panel on Climate Change (IPCC), the oceans absorb about 25% of the CO2 that is released into the atmosphere each year. This means that the oceans play a critical role in helping to mitigate the impacts of climate change by removing CO2 from the atmosphere.

Seaweed has the potential to sequester large amounts of carbon each year, according to a 2016 study published in Nature Geoscience. The paper estimates that marine macroalgae, also known as kelp, could store around 175 million tons of carbon annually through burial in coastal sediments or exporting it to the deep sea. In 2020, a report from the Energy Futures Initiative, a non-profit focused on climate technology, suggested that marine carbon dioxide removal could potentially sequester CO2 at a scale of one billion tons in the future due to the vast amount of available space in the ocean and the lack of land use issues.

The ocean can create carbon credits through a process called “ocean fertilization,” in which nutrients are added to the water to stimulate the growth of phytoplankton, which are small photosynthetic organisms that absorb carbon dioxide from the atmosphere. When phytoplankton die, they sink to the ocean floor and take the carbon they have absorbed with them, effectively removing carbon dioxide from the atmosphere. This process can be quantified, and the carbon dioxide removed from the atmosphere through ocean fertilization can be turned into carbon credits that can be traded on carbon markets.

It is worth noting that while the oceans are an important carbon sink, they can also be a source of CO2 if the carbon that is stored in the water is released back into the atmosphere. This can occur through a process called ocean acidification, which occurs when the pH of the water decreases due to the absorption of CO2. This can have negative impacts on marine life and ecosystems.