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Sage Ono (USA) explores the abundant life around the giant kelp forests in Monterey Bay National Marine Sanctuary.

This location used to be known for giant kelp so thick it blocked out the sun. However, when Sage swam down, he found hordes of purple sea urchins chewing through what was left of the once dense kelp forest.

Purple sea urchins have benefited from the decline of the sunflower sea star. This was a major predator until it was almost completely wiped out by a wasting disease in 2014.

The resulting explosion in urchin numbers, together with a series of marine heatwaves, has reduced kelp cover in the region by more than 80%.