Quote from SierraClub (Link 2)

The Claim
Seaweed has been removing carbon dioxide from the atmosphere for at least 500 million years. Recent studies suggest that wild seaweed continues to do humanity a solid by sequestering 173 million metric tons annually. The average square kilometer of seaweed can sequester more than a thousand metric tons. Start-ups like Maine-based Running Tide hope to help this process along by farming seaweed for the express purpose of sinking it and locking down its carbon. Shopify has already agreed to be the first purchaser of the resulting carbon offsets.

The picture : Illustration by Peter and Maria Hoey

Endquote from SierraClub (Link 2)