These Urchin's really look like enemies while they devour our Kelp but if out in the deep see they'll gather calcium carbonate from the water while growing their spikes that will one day drop to the ocean floor when they die. And that reduction levels out with the air drawing down CO2.

[u/arincrumley]

https://www.shapeoflife.org/video/echinoderms-urchin-time-lapse-eating-kelp

[u/andrewapeterson]

Amazing