Here is quote from my Thursday Briefed by Data post:
The short story is that whales come to the surface to go to the bathroom. This provides food for phytoplankton and creates growth in phytoplankton. This moves up the food chain to create food for whales. When the fish and whales die, carbon is sequestered on the floor of the ocean.
Click the link to read more, as well as the other quick takes.