The Largest Seaweed Bloom on Earth

The world’s largest patch of seaweed appears every summer in the mid-Atlantic. Since 2011, the Great Atlantic Sargassum Belt has been growing to monstrous sizes - thousands of kilometres long - and it's been clogging up beaches along the Americas with metres of stinking brown sludge. Now, scientists in Florida and George have used satellite tracking to figure out what's going on - as Phil Sansom explains...