Firstly, what is a carbon sink?
It's something that takes out more carbon dioxide from the environment than it releases. The main natural carbon sinks are plants, the ocean, and soil. Each of them effectively takes carbon dioxide out of the environment through their normal processes. They then "store it" in a form that doesn't contribute to greenhouse gasses or accelerate climate change.
Most of us know that trees can help reduce the amount of carbon dioxide from the environment (they "use it up" through the process of photosynthesis - where they turn carbon dioxide, light and water into a bigger tree). Planting trees has, therefore become a widely known and used way to combat climate change.
However, did you know that seaweed is a highly effective carbon sink? Scientists are now looking at how it could be used to prevent global warming.